Reference:https://src.fedoraproject.org/rpms/openssh/blob/rawhide/f/openssh-8.0p1-pkcs11-uri.patch

---
 Makefile.in                      |  20 +-
 configure.ac                     |  37 ++
 regress/agent-pkcs11.sh          |   2 +-
 regress/pkcs11.sh                | 349 +++++++++++++++
 regress/unittests/pkcs11/tests.c | 337 +++++++++++++++
 ssh-add.c                        |  44 +-
 ssh-agent.c                      | 101 ++++-
 ssh-keygen.c                     |   7 +-
 ssh-pkcs11-client.c              |   3 +
 ssh-pkcs11-uri.c                 | 419 ++++++++++++++++++
 ssh-pkcs11-uri.h                 |  42 ++
 ssh-pkcs11.c                     | 715 +++++++++++++++++++++++--------
 ssh-pkcs11.h                     |   4 +
 ssh.c                            | 104 +++--
 ssh_config.5                     |  15 +
 15 files changed, 1961 insertions(+), 238 deletions(-)
 create mode 100644 regress/pkcs11.sh
 create mode 100644 regress/unittests/pkcs11/tests.c
 create mode 100644 ssh-pkcs11-uri.c
 create mode 100644 ssh-pkcs11-uri.h

diff --git a/Makefile.in b/Makefile.in
index 8229885..45f7a93 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -105,7 +105,7 @@ LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
 	monitor_fdpass.o rijndael.o ssh-dss.o ssh-ecdsa.o ssh-ecdsa-sk.o \
 	ssh-ed25519-sk.o ssh-rsa.o dh.o \
 	msg.o progressmeter.o dns.o entropy.o gss-genr.o umac.o umac128.o \
-	ssh-pkcs11.o smult_curve25519_ref.o \
+	ssh-pkcs11.o ssh-pkcs11-uri.o smult_curve25519_ref.o \
 	poly1305.o chacha.o cipher-chachapoly.o cipher-chachapoly-libcrypto.o \
 	ssh-ed25519.o digest-openssl.o digest-libc.o \
 	hmac.o sc25519.o ge25519.o fe25519.o ed25519.o verify.o hash.o \
@@ -299,6 +299,8 @@ clean:	regressclean
 	rm -f regress/unittests/sshsig/test_sshsig$(EXEEXT)
 	rm -f regress/unittests/utf8/*.o
 	rm -f regress/unittests/utf8/test_utf8$(EXEEXT)
+	rm -f regress/unittests/pkcs11/*.o
+	rm -f regress/unittests/pkcs11/test_pkcs11$(EXEEXT)
 	rm -f regress/misc/sk-dummy/*.o
 	rm -f regress/misc/sk-dummy/*.lo
 	rm -f regress/misc/sk-dummy/sk-dummy.so
@@ -336,6 +338,8 @@ distclean:	regressclean
 	rm -f regress/unittests/sshsig/test_sshsig
 	rm -f regress/unittests/utf8/*.o
 	rm -f regress/unittests/utf8/test_utf8
+	rm -f regress/unittests/pkcs11/*.o
+	rm -f regress/unittests/pkcs11/test_pkcs11
 	rm -f regress/misc/sk-dummy/*.o
 	rm -f regress/misc/sk-dummy/*.lo
 	rm -f regress/misc/sk-dummy/sk-dummy.so
@@ -513,6 +517,7 @@ regress-prep:
 	$(MKDIR_P) `pwd`/regress/unittests/sshkey
 	$(MKDIR_P) `pwd`/regress/unittests/sshsig
 	$(MKDIR_P) `pwd`/regress/unittests/utf8
+	$(MKDIR_P) `pwd`/regress/unittests/pkcs11
 	$(MKDIR_P) `pwd`/regress/misc/sk-dummy
 	[ -f `pwd`/regress/Makefile ] || \
 	    ln -s `cd $(srcdir) && pwd`/regress/Makefile `pwd`/regress/Makefile
@@ -679,6 +684,16 @@ regress/unittests/utf8/test_utf8$(EXEEXT): \
 	    regress/unittests/test_helper/libtest_helper.a \
 	    -lssh -lopenbsd-compat -lssh -lopenbsd-compat $(TESTLIBS)
 
+UNITTESTS_TEST_PKCS11_OBJS=\
+	regress/unittests/pkcs11/tests.o
+
+regress/unittests/pkcs11/test_pkcs11$(EXEEXT): \
+    ${UNITTESTS_TEST_PKCS11_OBJS} \
+    regress/unittests/test_helper/libtest_helper.a libssh.a
+	$(LD) -o $@ $(LDFLAGS) $(UNITTESTS_TEST_PKCS11_OBJS) \
+	    regress/unittests/test_helper/libtest_helper.a \
+	    -lssh -lopenbsd-compat -lssh -lopenbsd-compat $(TESTLIBS)
+
 # These all need to be compiled -fPIC, so they are treated differently.
 SK_DUMMY_OBJS=\
 	regress/misc/sk-dummy/sk-dummy.lo \
@@ -713,7 +728,8 @@ regress-unit-binaries: regress-prep $(REGRESSLIBS) \
 	regress/unittests/sshbuf/test_sshbuf$(EXEEXT) \
 	regress/unittests/sshkey/test_sshkey$(EXEEXT) \
 	regress/unittests/sshsig/test_sshsig$(EXEEXT) \
-	regress/unittests/utf8/test_utf8$(EXEEXT)
+	regress/unittests/utf8/test_utf8$(EXEEXT) \
+	regress/unittests/pkcs11/test_pkcs11$(EXEEXT) \
 
 tests:	file-tests t-exec interop-tests unit
 	echo all tests passed
diff --git a/configure.ac b/configure.ac
index 6f7dc48..b57d0a5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2035,12 +2035,14 @@ AC_LINK_IFELSE(
 	[AC_DEFINE([HAVE_ISBLANK], [1], [Define if you have isblank(3C).])
 ])
 
+SCARD_MSG="yes"
 disable_pkcs11=
 AC_ARG_ENABLE([pkcs11],
 	[  --disable-pkcs11        disable PKCS#11 support code [no]],
 	[
 		if test "x$enableval" = "xno" ; then
 			disable_pkcs11=1
+			SCARD_MSG="no"
 		fi
 	]
 )
@@ -2064,6 +2066,40 @@ AC_SEARCH_LIBS([dlopen], [dl])
 AC_CHECK_FUNCS([dlopen])
 AC_CHECK_DECL([RTLD_NOW], [], [], [#include <dlfcn.h>])
 
+# Check whether we have a p11-kit, we got default provider on command line
+DEFAULT_PKCS11_PROVIDER_MSG="no"
+AC_ARG_WITH([default-pkcs11-provider],
+	[  --with-default-pkcs11-provider[[=PATH]]   Use default pkcs11 provider (p11-kit detected by default)],
+	[ if test "x$withval" != "xno" && test "x$disable_pkcs11" = "x"; then
+		if test "x$withval" = "xyes" ; then
+			AC_PATH_TOOL([PKGCONFIG], [pkg-config], [no])
+			if test "x$PKGCONFIG" != "xno"; then
+				AC_MSG_CHECKING([if $PKGCONFIG knows about p11-kit])
+				if "$PKGCONFIG" "p11-kit-1"; then
+					AC_MSG_RESULT([yes])
+					use_pkgconfig_for_p11kit=yes
+				else
+					AC_MSG_RESULT([no])
+				fi
+			fi
+		else
+			PKCS11_PATH="${withval}"
+		fi
+		if test "x$use_pkgconfig_for_p11kit" = "xyes"; then
+			PKCS11_PATH=`$PKGCONFIG --variable=proxy_module p11-kit-1`
+		fi
+		AC_CHECK_FILE("$PKCS11_PATH",
+			[ AC_DEFINE_UNQUOTED([PKCS11_DEFAULT_PROVIDER], ["$PKCS11_PATH"], [Path to default PKCS#11 provider (p11-kit proxy)])
+			  DEFAULT_PKCS11_PROVIDER_MSG="$PKCS11_PATH"
+			],
+			[ AC_MSG_ERROR([Requested PKCS11 provided not found]) ]
+		)
+	else
+		AC_MSG_WARN([Needs PKCS11 support to enable default pkcs11 provider])
+	fi ]
+)
+
+
 # IRIX has a const char return value for gai_strerror()
 AC_CHECK_FUNCS([gai_strerror], [
 	AC_DEFINE([HAVE_GAI_STRERROR])
@@ -5651,6 +5687,7 @@ echo "                  BSD Auth support: $BSD_AUTH_MSG"
 echo "              Random number source: $RAND_MSG"
 echo "             Privsep sandbox style: $SANDBOX_STYLE"
 echo "                   PKCS#11 support: $enable_pkcs11"
+echo "          Default PKCS#11 provider: $DEFAULT_PKCS11_PROVIDER_MSG"
 echo "                  U2F/FIDO support: $enable_sk"
 
 echo ""
diff --git a/regress/agent-pkcs11.sh b/regress/agent-pkcs11.sh
index 268a70d..72efa3b 100644
--- a/regress/agent-pkcs11.sh
+++ b/regress/agent-pkcs11.sh
@@ -113,7 +113,7 @@ else
 	done
 
 	trace "remove pkcs11 keys"
-	echo ${TEST_SSH_PIN} | notty ${SSHADD} -e ${TEST_SSH_PKCS11} > /dev/null 2>&1
+	${SSHADD} -e ${TEST_SSH_PKCS11} > /dev/null 2>&1
 	r=$?
 	if [ $r -ne 0 ]; then
 		fail "ssh-add -e failed: exit code $r"
diff --git a/regress/pkcs11.sh b/regress/pkcs11.sh
new file mode 100644
index 0000000..a91aee9
--- /dev/null
+++ b/regress/pkcs11.sh
@@ -0,0 +1,349 @@
+#
+#  Copyright (c) 2017 Red Hat
+#
+#  Authors: Jakub Jelen <jjelen@redhat.com>
+#
+#  Permission to use, copy, modify, and distribute this software for any
+#  purpose with or without fee is hereby granted, provided that the above
+#  copyright notice and this permission notice appear in all copies.
+#
+#  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+#  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+#  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+#  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+#  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+#  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+#  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+tid="pkcs11 tests with soft token"
+
+try_token_libs() {
+	for _lib in "$@" ; do
+		if test -f "$_lib" ; then
+			verbose "Using token library $_lib"
+			TEST_SSH_PKCS11="$_lib"
+			return
+		fi
+	done
+	echo "skipped: Unable to find PKCS#11 token library"
+	exit 0
+}
+
+try_token_libs \
+	/usr/local/lib/softhsm/libsofthsm2.so \
+	/usr/lib64/pkcs11/libsofthsm2.so \
+	/usr/lib/x86_64-linux-gnu/softhsm/libsofthsm2.so
+
+TEST_SSH_PIN=1234
+TEST_SSH_SOPIN=12345678
+if [ "x$TEST_SSH_SSHPKCS11HELPER" != "x" ]; then
+	SSH_PKCS11_HELPER="${TEST_SSH_SSHPKCS11HELPER}"
+	export SSH_PKCS11_HELPER
+fi
+
+test -f "$TEST_SSH_PKCS11" || fatal "$TEST_SSH_PKCS11 does not exist"
+
+# setup environment for softhsm token
+DIR=$OBJ/SOFTHSM
+rm -rf $DIR
+TOKEN=$DIR/tokendir
+mkdir -p $TOKEN
+SOFTHSM2_CONF=$DIR/softhsm2.conf
+export SOFTHSM2_CONF
+cat > $SOFTHSM2_CONF << EOF
+# SoftHSM v2 configuration file
+directories.tokendir = ${TOKEN}
+objectstore.backend = file
+# ERROR, WARNING, INFO, DEBUG
+log.level = DEBUG
+# If CKF_REMOVABLE_DEVICE flag should be set
+slots.removable = false
+EOF
+out=$(softhsm2-util --init-token --free --label token-slot-0 --pin "$TEST_SSH_PIN" --so-pin "$TEST_SSH_SOPIN")
+slot=$(echo -- $out | sed 's/.* //')
+
+# prevent ssh-agent from calling ssh-askpass
+SSH_ASKPASS=/usr/bin/true
+export SSH_ASKPASS
+unset DISPLAY
+# We need interactive access to test PKCS# since it prompts for PIN
+sed -i 's/.*BatchMode.*//g' $OBJ/ssh_proxy
+
+# start command w/o tty, so ssh accepts pin from stdin (from agent-pkcs11.sh)
+notty() {
+	perl -e 'use POSIX; POSIX::setsid();
+	    if (fork) { wait; exit($? >> 8); } else { exec(@ARGV) }' "$@"
+}
+
+trace "generating keys"
+ID1="02"
+ID2="04"
+RSA=${DIR}/RSA
+EC=${DIR}/EC
+openssl genpkey -algorithm rsa > $RSA
+openssl pkcs8 -nocrypt -in $RSA |\
+    softhsm2-util --slot "$slot" --label "SSH RSA Key $ID1" --id $ID1 \
+	--pin "$TEST_SSH_PIN" --import /dev/stdin
+openssl genpkey \
+    -genparam \
+    -algorithm ec \
+    -pkeyopt ec_paramgen_curve:prime256v1 |\
+    openssl genpkey \
+    -paramfile /dev/stdin > $EC
+openssl pkcs8 -nocrypt -in $EC |\
+    softhsm2-util --slot "$slot" --label "SSH ECDSA Key $ID2" --id $ID2 \
+	--pin "$TEST_SSH_PIN" --import /dev/stdin
+
+trace "List the keys in the ssh-keygen with PKCS#11 URIs"
+${SSHKEYGEN} -D ${TEST_SSH_PKCS11} > $OBJ/token_keys
+if [ $? -ne 0 ]; then
+	fail "FAIL: keygen fails to enumerate keys on PKCS#11 token"
+fi
+grep "pkcs11:" $OBJ/token_keys > /dev/null
+if [ $? -ne 0 ]; then
+	fail "FAIL: The keys from ssh-keygen do not contain PKCS#11 URI as a comment"
+fi
+
+# Set the ECDSA key to authorized keys
+grep "ECDSA" $OBJ/token_keys > $OBJ/authorized_keys_$USER
+
+trace "Simple connect with ssh (without PKCS#11 URI)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -I ${TEST_SSH_PKCS11} \
+    -F $OBJ/ssh_proxy somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with pkcs11 failed (exit code $r)"
+fi
+
+trace "Connect with PKCS#11 URI"
+trace "  (ECDSA key should succeed)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy \
+    -i "pkcs11:id=%${ID2}?module-path=${TEST_SSH_PKCS11}" somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI failed (exit code $r)"
+fi
+
+trace "  (RSA key should fail)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy \
+     -i "pkcs11:id=%${ID1}?module-path=${TEST_SSH_PKCS11}" somehost exit 5
+r=$?
+if [ $r -eq 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI succeeded (should fail)"
+fi
+
+trace "Connect with PKCS#11 URI including PIN should not prompt"
+trace "  (ECDSA key should succeed)"
+${SSH} -F $OBJ/ssh_proxy -i \
+    "pkcs11:id=%${ID2}?module-path=${TEST_SSH_PKCS11}&pin-value=${TEST_SSH_PIN}" somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI failed (exit code $r)"
+fi
+
+trace "  (RSA key should fail)"
+${SSH} -F $OBJ/ssh_proxy -i \
+    "pkcs11:id=%${ID1}?module-path=${TEST_SSH_PKCS11}&pin-value=${TEST_SSH_PIN}" somehost exit 5
+r=$?
+if [ $r -eq 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI succeeded (should fail)"
+fi
+
+trace "Connect with various filtering options in PKCS#11 URI"
+trace "  (by object label, ECDSA should succeed)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy \
+    -i "pkcs11:object=SSH%20ECDSA%20Key%2004?module-path=${TEST_SSH_PKCS11}" somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI failed (exit code $r)"
+fi
+
+trace "  (by object label, RSA key should fail)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy \
+     -i "pkcs11:object=SSH%20RSA%20Key%2002?module-path=${TEST_SSH_PKCS11}" somehost exit 5
+r=$?
+if [ $r -eq 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI succeeded (should fail)"
+fi
+
+trace "  (by token label, ECDSA key should succeed)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy \
+    -i "pkcs11:id=%${ID2};token=token-slot-0?module-path=${TEST_SSH_PKCS11}" somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI failed (exit code $r)"
+fi
+
+trace "  (by wrong token label, should fail)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy \
+     -i "pkcs11:token=token-slot-99?module-path=${TEST_SSH_PKCS11}" somehost exit 5
+r=$?
+if [ $r -eq 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI succeeded (should fail)"
+fi
+
+
+
+
+trace "Test PKCS#11 URI specification in configuration files"
+echo "IdentityFile \"pkcs11:id=%${ID2}?module-path=${TEST_SSH_PKCS11}\"" \
+    >> $OBJ/ssh_proxy
+trace "  (ECDSA key should succeed)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI in config failed (exit code $r)"
+fi
+
+# Set the RSA key as authorized
+grep "RSA" $OBJ/token_keys > $OBJ/authorized_keys_$USER
+
+trace "  (RSA key should fail)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy somehost exit 5
+r=$?
+if [ $r -eq 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI in config succeeded (should fail)"
+fi
+sed -i -e "/IdentityFile/d" $OBJ/ssh_proxy
+
+trace "Test PKCS#11 URI specification in configuration files with bogus spaces"
+echo "IdentityFile \"    pkcs11:?module-path=${TEST_SSH_PKCS11}    \"" \
+    >> $OBJ/ssh_proxy
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI with bogus spaces in config failed" \
+	    "(exit code $r)"
+fi
+sed -i -e "/IdentityFile/d" $OBJ/ssh_proxy
+
+
+trace "Combination of PKCS11Provider and PKCS11URI on commandline"
+trace "  (RSA key should succeed)"
+echo ${TEST_SSH_PIN} | notty ${SSH} -F $OBJ/ssh_proxy \
+    -i "pkcs11:id=%${ID1}" -I ${TEST_SSH_PKCS11} somehost exit 5
+r=$?
+if [ $r -ne 5 ]; then
+	fail "FAIL: ssh connect with PKCS#11 URI and provider combination" \
+	    "failed (exit code $r)"
+fi
+
+trace "Regress: Missing provider in PKCS11URI option"
+${SSH} -F $OBJ/ssh_proxy \
+    -o IdentityFile=\"pkcs11:token=segfault\" somehost exit 5
+r=$?
+if [ $r -eq 139 ]; then
+	fail "FAIL: ssh connect with missing provider_id from configuration option" \
+	    "crashed (exit code $r)"
+fi
+
+
+trace "SSH Agent can work with PKCS#11 URI"
+trace "start the agent"
+eval `${SSHAGENT} -s` >  /dev/null
+
+r=$?
+if [ $r -ne 0 ]; then
+	fail "could not start ssh-agent: exit code $r"
+else
+	trace "add whole provider to agent"
+	echo ${TEST_SSH_PIN} | notty ${SSHADD} \
+	    "pkcs11:?module-path=${TEST_SSH_PKCS11}" #> /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "FAIL: ssh-add failed with whole provider: exit code $r"
+	fi
+
+	trace " pkcs11 list via agent (all keys)"
+	${SSHADD} -l > /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "FAIL: ssh-add -l failed with whole provider: exit code $r"
+	fi
+
+	trace " pkcs11 connect via agent (all keys)"
+	${SSH} -F $OBJ/ssh_proxy somehost exit 5
+	r=$?
+	if [ $r -ne 5 ]; then
+		fail "FAIL: ssh connect failed with whole provider (exit code $r)"
+	fi
+
+	trace " remove pkcs11 keys (all keys)"
+	${SSHADD} -d "pkcs11:?module-path=${TEST_SSH_PKCS11}" > /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "FAIL: ssh-add -d failed with whole provider: exit code $r"
+	fi
+
+	trace "add only RSA key to the agent"
+	echo ${TEST_SSH_PIN} | notty ${SSHADD} \
+	    "pkcs11:id=%${ID1}?module-path=${TEST_SSH_PKCS11}" > /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "FAIL ssh-add failed with RSA key: exit code $r"
+	fi
+
+	trace " pkcs11 connect via agent (RSA key)"
+	${SSH} -F $OBJ/ssh_proxy somehost exit 5
+	r=$?
+	if [ $r -ne 5 ]; then
+		fail "FAIL: ssh connect failed with RSA key (exit code $r)"
+	fi
+
+	trace " remove RSA pkcs11 key"
+	${SSHADD} -d "pkcs11:id=%${ID1}?module-path=${TEST_SSH_PKCS11}" \
+	    > /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "FAIL: ssh-add -d failed with RSA key: exit code $r"
+	fi
+
+	trace "add only ECDSA key to the agent"
+	echo ${TEST_SSH_PIN} | notty ${SSHADD} \
+	    "pkcs11:id=%${ID2}?module-path=${TEST_SSH_PKCS11}" > /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "FAIL: ssh-add failed with second key: exit code $r"
+	fi
+
+	trace " pkcs11 connect via agent (ECDSA key should fail)"
+	${SSH} -F $OBJ/ssh_proxy somehost exit 5
+	r=$?
+	if [ $r -eq 5 ]; then
+		fail "FAIL: ssh connect passed with ECDSA key (should fail)"
+	fi
+
+	trace "add also the RSA key to the agent"
+	echo ${TEST_SSH_PIN} | notty ${SSHADD} \
+	    "pkcs11:id=%${ID1}?module-path=${TEST_SSH_PKCS11}" > /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "FAIL: ssh-add failed with first key: exit code $r"
+	fi
+
+	trace " remove ECDSA pkcs11 key"
+	${SSHADD} -d "pkcs11:id=%${ID2}?module-path=${TEST_SSH_PKCS11}" \
+	    > /dev/null 2>&1
+	r=$?
+	if [ $r -ne 0 ]; then
+		fail "ssh-add -d failed with ECDSA key: exit code $r"
+	fi
+
+	trace " remove already-removed pkcs11 key should fail"
+	${SSHADD} -d "pkcs11:id=%${ID2}?module-path=${TEST_SSH_PKCS11}" \
+	    > /dev/null 2>&1
+	r=$?
+	if [ $r -eq 0 ]; then
+		fail "FAIL: ssh-add -d passed with non-existing key (should fail)"
+	fi
+
+	trace " pkcs11 connect via agent (the RSA key should be still usable)"
+	${SSH} -F $OBJ/ssh_proxy somehost exit 5
+	r=$?
+	if [ $r -ne 5 ]; then
+		fail "ssh connect failed with RSA key (after removing ECDSA): exit code $r"
+	fi
+
+	trace "kill agent"
+	${SSHAGENT} -k > /dev/null
+fi
diff --git a/regress/unittests/pkcs11/tests.c b/regress/unittests/pkcs11/tests.c
new file mode 100644
index 0000000..d726fdf
--- /dev/null
+++ b/regress/unittests/pkcs11/tests.c
@@ -0,0 +1,337 @@
+/*
+ * Copyright (c) 2017 Red Hat
+ *
+ * Authors: Jakub Jelen <jjelen@redhat.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "includes.h"
+
+#include <locale.h>
+#include <string.h>
+
+#include "../test_helper/test_helper.h"
+
+#include "sshbuf.h"
+#include "ssh-pkcs11-uri.h"
+
+#define EMPTY_URI compose_uri(NULL, 0, NULL, NULL, NULL, NULL, NULL, NULL)
+
+/* prototypes are not public -- specify them here internally for tests */
+struct sshbuf *percent_encode(const char *, size_t, char *);
+int percent_decode(char *, char **);
+
+void
+compare_uri(struct pkcs11_uri *a, struct pkcs11_uri *b)
+{
+	ASSERT_PTR_NE(a, NULL);
+	ASSERT_PTR_NE(b, NULL);
+	ASSERT_SIZE_T_EQ(a->id_len, b->id_len);
+	ASSERT_MEM_EQ(a->id, b->id, a->id_len);
+	if (b->object != NULL)
+		ASSERT_STRING_EQ(a->object, b->object);
+	else /* both should be null */
+		ASSERT_PTR_EQ(a->object, b->object);
+	if (b->module_path != NULL)
+		ASSERT_STRING_EQ(a->module_path, b->module_path);
+	else /* both should be null */
+		ASSERT_PTR_EQ(a->module_path, b->module_path);
+	if (b->token != NULL)
+		ASSERT_STRING_EQ(a->token, b->token);
+	else /* both should be null */
+		ASSERT_PTR_EQ(a->token, b->token);
+	if (b->manuf != NULL)
+		ASSERT_STRING_EQ(a->manuf, b->manuf);
+	else /* both should be null */
+		ASSERT_PTR_EQ(a->manuf, b->manuf);
+	if (b->lib_manuf != NULL)
+		ASSERT_STRING_EQ(a->lib_manuf, b->lib_manuf);
+	else /* both should be null */
+		ASSERT_PTR_EQ(a->lib_manuf, b->lib_manuf);
+}
+
+void
+check_parse_rv(char *uri, struct pkcs11_uri *expect, int expect_rv)
+{
+	char *buf = NULL, *str;
+	struct pkcs11_uri *pkcs11uri = NULL;
+	int rv;
+
+	if (expect_rv == 0)
+		str = "Valid";
+	else
+		str = "Invalid";
+	asprintf(&buf, "%s PKCS#11 URI parsing: %s", str, uri);
+	TEST_START(buf);
+	free(buf);
+	pkcs11uri = pkcs11_uri_init();
+	rv = pkcs11_uri_parse(uri, pkcs11uri);
+	ASSERT_INT_EQ(rv, expect_rv);
+	if (rv == 0) /* in case of failure result is undefined */
+		compare_uri(pkcs11uri, expect);
+	pkcs11_uri_cleanup(pkcs11uri);
+	free(expect);
+	TEST_DONE();
+}
+
+void
+check_parse(char *uri, struct pkcs11_uri *expect)
+{
+	check_parse_rv(uri, expect, 0);
+}
+
+struct pkcs11_uri *
+compose_uri(unsigned char *id, size_t id_len, char *token, char *lib_manuf,
+    char *manuf, char *module_path, char *object, char *pin)
+{
+	struct pkcs11_uri *uri = pkcs11_uri_init();
+	if (id_len > 0) {
+		uri->id_len = id_len;
+		uri->id = id;
+	}
+	uri->module_path = module_path;
+	uri->token = token;
+	uri->lib_manuf = lib_manuf;
+	uri->manuf = manuf;
+	uri->object = object;
+	uri->pin = pin;
+	return uri;
+}
+
+static void
+test_parse_valid(void)
+{
+	/* path arguments */
+	check_parse("pkcs11:id=%01",
+	    compose_uri("\x01", 1, NULL, NULL, NULL, NULL, NULL, NULL));
+	check_parse("pkcs11:id=%00%01",
+	    compose_uri("\x00\x01", 2, NULL, NULL, NULL, NULL, NULL, NULL));
+	check_parse("pkcs11:token=SSH%20Keys",
+	    compose_uri(NULL, 0, "SSH Keys", NULL, NULL, NULL, NULL, NULL));
+	check_parse("pkcs11:library-manufacturer=OpenSC",
+	    compose_uri(NULL, 0, NULL, "OpenSC", NULL, NULL, NULL, NULL));
+	check_parse("pkcs11:manufacturer=piv_II",
+	    compose_uri(NULL, 0, NULL, NULL, "piv_II", NULL, NULL, NULL));
+	check_parse("pkcs11:object=SIGN%20Key",
+	    compose_uri(NULL, 0, NULL, NULL, NULL, NULL, "SIGN Key", NULL));
+	/* query arguments */
+	check_parse("pkcs11:?module-path=/usr/lib64/p11-kit-proxy.so",
+	    compose_uri(NULL, 0, NULL, NULL, NULL, "/usr/lib64/p11-kit-proxy.so", NULL, NULL));
+	check_parse("pkcs11:?pin-value=123456",
+	    compose_uri(NULL, 0, NULL, NULL, NULL, NULL, NULL, "123456"));
+
+	/* combinations */
+	/* ID SHOULD be percent encoded */
+	check_parse("pkcs11:token=SSH%20Key;id=0",
+	    compose_uri("0", 1, "SSH Key", NULL, NULL, NULL, NULL, NULL));
+	check_parse(
+	    "pkcs11:manufacturer=CAC?module-path=/usr/lib64/p11-kit-proxy.so",
+	    compose_uri(NULL, 0, NULL, NULL, "CAC",
+	    "/usr/lib64/p11-kit-proxy.so", NULL, NULL));
+	check_parse(
+	    "pkcs11:object=RSA%20Key?module-path=/usr/lib64/pkcs11/opencryptoki.so",
+	    compose_uri(NULL, 0, NULL, NULL, NULL,
+	    "/usr/lib64/pkcs11/opencryptoki.so", "RSA Key", NULL));
+	check_parse("pkcs11:?module-path=/usr/lib64/p11-kit-proxy.so&pin-value=123456",
+	    compose_uri(NULL, 0, NULL, NULL, NULL, "/usr/lib64/p11-kit-proxy.so", NULL, "123456"));
+
+	/* empty path component matches everything */
+	check_parse("pkcs11:", EMPTY_URI);
+
+	/* empty string is a valid to match against (and different from NULL) */
+	check_parse("pkcs11:token=",
+	    compose_uri(NULL, 0, "", NULL, NULL, NULL, NULL, NULL));
+	/* Percent character needs to be percent-encoded */
+	check_parse("pkcs11:token=%25",
+	     compose_uri(NULL, 0, "%", NULL, NULL, NULL, NULL, NULL));
+}
+
+static void
+test_parse_invalid(void)
+{
+	/* Invalid percent encoding */
+	check_parse_rv("pkcs11:id=%0", EMPTY_URI, -1);
+	/* Invalid percent encoding */
+	check_parse_rv("pkcs11:id=%ZZ", EMPTY_URI, -1);
+	/* Space MUST be percent encoded -- XXX not enforced yet */
+	check_parse("pkcs11:token=SSH Keys",
+	    compose_uri(NULL, 0, "SSH Keys", NULL, NULL, NULL, NULL, NULL));
+	/* MUST NOT contain duplicate attributes of the same name */
+	check_parse_rv("pkcs11:id=%01;id=%02", EMPTY_URI, -1);
+	/* MUST NOT contain duplicate attributes of the same name */
+	check_parse_rv("pkcs11:?pin-value=111111&pin-value=123456", EMPTY_URI, -1);
+	/* Unrecognized attribute in path are ignored with log message */
+	check_parse("pkcs11:key_name=SSH", EMPTY_URI);
+	/* Unrecognized attribute in query SHOULD be ignored */
+	check_parse("pkcs11:?key_name=SSH", EMPTY_URI);
+}
+
+void
+check_gen(char *expect, struct pkcs11_uri *uri)
+{
+	char *buf = NULL, *uri_str;
+
+	asprintf(&buf, "Valid PKCS#11 URI generation: %s", expect);
+	TEST_START(buf);
+	free(buf);
+	uri_str = pkcs11_uri_get(uri);
+	ASSERT_PTR_NE(uri_str, NULL);
+	ASSERT_STRING_EQ(uri_str, expect);
+	free(uri_str);
+	TEST_DONE();
+}
+
+static void
+test_generate_valid(void)
+{
+	/* path arguments */
+	check_gen("pkcs11:id=%01",
+	    compose_uri("\x01", 1, NULL, NULL, NULL, NULL, NULL, NULL));
+	check_gen("pkcs11:id=%00%01",
+	    compose_uri("\x00\x01", 2, NULL, NULL, NULL, NULL, NULL, NULL));
+	check_gen("pkcs11:token=SSH%20Keys", /* space must be percent encoded */
+	    compose_uri(NULL, 0, "SSH Keys", NULL, NULL, NULL, NULL, NULL));
+	/* library-manufacturer is not implmented now */
+	/*check_gen("pkcs11:library-manufacturer=OpenSC",
+	    compose_uri(NULL, 0, NULL, "OpenSC", NULL, NULL, NULL, NULL));*/
+	check_gen("pkcs11:manufacturer=piv_II",
+	    compose_uri(NULL, 0, NULL, NULL, "piv_II", NULL, NULL, NULL));
+	check_gen("pkcs11:object=RSA%20Key",
+	    compose_uri(NULL, 0, NULL, NULL, NULL, NULL, "RSA Key", NULL));
+	/* query arguments */
+	check_gen("pkcs11:?module-path=/usr/lib64/p11-kit-proxy.so",
+	    compose_uri(NULL, 0, NULL, NULL, NULL, "/usr/lib64/p11-kit-proxy.so", NULL, NULL));
+
+	/* combinations */
+	check_gen("pkcs11:id=%02;token=SSH%20Keys",
+	    compose_uri("\x02", 1, "SSH Keys", NULL, NULL, NULL, NULL, NULL));
+	check_gen("pkcs11:id=%EE%02?module-path=/usr/lib64/p11-kit-proxy.so",
+	    compose_uri("\xEE\x02", 2, NULL, NULL, NULL, "/usr/lib64/p11-kit-proxy.so", NULL, NULL));
+	check_gen("pkcs11:object=Encryption%20Key;manufacturer=piv_II",
+	    compose_uri(NULL, 0, NULL, NULL, "piv_II", NULL, "Encryption Key", NULL));
+
+	/* empty path component matches everything */
+	check_gen("pkcs11:", EMPTY_URI);
+
+}
+
+void
+check_encode(char *source, size_t len, char *allow_list, char *expect)
+{
+	char *buf = NULL;
+	struct sshbuf *b;
+
+	asprintf(&buf, "percent_encode: expected %s", expect);
+	TEST_START(buf);
+	free(buf);
+
+	b = percent_encode(source, len, allow_list);
+	ASSERT_STRING_EQ(sshbuf_ptr(b), expect);
+	sshbuf_free(b);
+	TEST_DONE();
+}
+
+static void
+test_percent_encode_multibyte(void)
+{
+	/* SHOULD be encoded as octets according to the UTF-8 character encoding */
+
+	/* multi-byte characters are "for free" */
+	check_encode("$", 1, "", "%24");
+	check_encode("¢", 2, "", "%C2%A2");
+	check_encode("€", 3, "", "%E2%82%AC");
+	check_encode("𐍈", 4, "", "%F0%90%8D%88");
+
+	/* CK_UTF8CHAR is unsigned char (1 byte) */
+	/* labels SHOULD be normalized to NFC [UAX15] */
+
+}
+
+static void
+test_percent_encode(void)
+{
+	/* Without allow list encodes everything (for CKA_ID) */
+	check_encode("A*", 2, "", "%41%2A");
+	check_encode("\x00", 1, "", "%00");
+	check_encode("\x7F", 1, "", "%7F");
+	check_encode("\x80", 1, "", "%80");
+	check_encode("\xff", 1, "", "%FF");
+
+	/* Default allow list encodes anything but safe letters */
+	check_encode("test" "\x00" "0alpha", 11, PKCS11_URI_WHITELIST,
+	    "test%000alpha");
+	check_encode(" ", 1, PKCS11_URI_WHITELIST,
+	    "%20"); /* Space MUST be percent encoded */
+	check_encode("/", 1, PKCS11_URI_WHITELIST,
+	    "%2F"); /* '/' delimiter MUST be percent encoded (in the path) */
+	check_encode("?", 1, PKCS11_URI_WHITELIST,
+	    "%3F"); /* delimiter '?' MUST be percent encoded (in the path) */
+	check_encode("#", 1, PKCS11_URI_WHITELIST,
+	    "%23"); /* '#' MUST be always percent encoded */
+	check_encode("key=value;separator?query&amp;#anch", 35, PKCS11_URI_WHITELIST,
+	    "key%3Dvalue%3Bseparator%3Fquery%26amp%3B%23anch");
+
+	/* Components in query can have '/' unencoded (useful for paths) */
+	check_encode("/path/to.file", 13, PKCS11_URI_WHITELIST "/",
+	    "/path/to.file");
+}
+
+void
+check_decode(char *source, char *expect, int expect_len)
+{
+	char *buf = NULL, *out = NULL;
+	int rv;
+
+	asprintf(&buf, "percent_decode: %s", source);
+	TEST_START(buf);
+	free(buf);
+
+	rv = percent_decode(source, &out);
+	ASSERT_INT_EQ(rv, expect_len);
+	if (rv >= 0)
+		ASSERT_MEM_EQ(out, expect, expect_len);
+	free(out);
+	TEST_DONE();
+}
+
+static void
+test_percent_decode(void)
+{
+	/* simple valid cases */
+	check_decode("%00", "\x00", 1);
+	check_decode("%FF", "\xFF", 1);
+
+	/* normal strings shold be kept intact */
+	check_decode("strings are left", "strings are left", 16);
+	check_decode("10%25 of trees", "10% of trees", 12);
+
+	/* make sure no more than 2 bytes are parsed */
+	check_decode("%222", "\x22" "2", 2);
+
+	/* invalid expects failure */
+	check_decode("%0", "", -1);
+	check_decode("%Z", "", -1);
+	check_decode("%FG", "", -1);
+}
+
+void
+tests(void)
+{
+	test_percent_encode();
+	test_percent_encode_multibyte();
+	test_percent_decode();
+	test_parse_valid();
+	test_parse_invalid();
+	test_generate_valid();
+}
diff --git a/ssh-add.c b/ssh-add.c
index 777f21e..940e3a0 100644
--- a/ssh-add.c
+++ b/ssh-add.c
@@ -69,6 +69,7 @@
 #include "ssh-sk.h"
 #include "sk-api.h"
 #include "hostfile.h"
+#include "ssh-pkcs11-uri.h"
 
 /* argv0 */
 extern char *__progname;
@@ -230,6 +231,34 @@ delete_all(int agent_fd, int qflag)
 	return ret;
 }
 
+#ifdef ENABLE_PKCS11
+static int update_card(int, int, const char *, int, struct dest_constraint **, size_t, char *);
+
+int
+update_pkcs11_uri(int agent_fd, int adding, const char *pkcs11_uri, int qflag,
+    struct dest_constraint **dest_constraints, size_t ndest_constraints)
+{
+	char *pin = NULL;
+	struct pkcs11_uri *uri;
+
+	/* dry-run parse to make sure the URI is valid and to report errors */
+	uri = pkcs11_uri_init();
+	if (pkcs11_uri_parse((char *) pkcs11_uri, uri) != 0)
+		fatal("Failed to parse PKCS#11 URI");
+	if (uri->pin != NULL) {
+		pin = strdup(uri->pin);
+		if (pin == NULL) {
+			fatal("Failed to dupplicate string");
+		}
+		/* pin is freed in the update_card() */
+	}
+	pkcs11_uri_cleanup(uri);
+
+	return update_card(agent_fd, adding, pkcs11_uri, qflag, 
+	           dest_constraints, ndest_constraints, pin);
+}
+#endif
+
 static int
 add_file(int agent_fd, const char *filename, int key_only, int qflag,
     const char *skprovider, struct dest_constraint **dest_constraints,
@@ -445,12 +474,11 @@ add_file(int agent_fd, const char *filename, int key_only, int qflag,
 
 static int
 update_card(int agent_fd, int add, const char *id, int qflag,
-    struct dest_constraint **dest_constraints, size_t ndest_constraints)
+    struct dest_constraint **dest_constraints, size_t ndest_constraints, char *pin)
 {
-	char *pin = NULL;
 	int r, ret = -1;
 
-	if (add) {
+	if (add && pin == NULL) {
 		if ((pin = read_passphrase("Enter passphrase for PKCS#11: ",
 		    RP_ALLOW_STDIN)) == NULL)
 			return -1;
@@ -634,6 +662,14 @@ do_file(int agent_fd, int deleting, int key_only, char *file, int qflag,
     const char *skprovider, struct dest_constraint **dest_constraints,
     size_t ndest_constraints)
 {
+#ifdef ENABLE_PKCS11
+	if (strlen(file) >= strlen(PKCS11_URI_SCHEME) &&
+	    strncmp(file, PKCS11_URI_SCHEME,
+	    strlen(PKCS11_URI_SCHEME)) == 0) {
+		return update_pkcs11_uri(agent_fd, !deleting, file, qflag,
+                   dest_constraints, ndest_constraints);
+	}
+#endif
 	if (deleting) {
 		if (delete_file(agent_fd, file, key_only, qflag) == -1)
 			return -1;
@@ -960,7 +996,7 @@ main(int argc, char **argv)
 	}
 	if (pkcs11provider != NULL) {
 		if (update_card(agent_fd, !deleting, pkcs11provider,
-		    qflag, dest_constraints, ndest_constraints) == -1)
+		    qflag, dest_constraints, ndest_constraints, NULL) == -1)
 			ret = 1;
 		goto done;
 	}
diff --git a/ssh-agent.c b/ssh-agent.c
index 006ddad..50d0638 100644
--- a/ssh-agent.c
+++ b/ssh-agent.c
@@ -1369,10 +1369,72 @@ no_identities(SocketEntry *e)
 }
 
 #ifdef ENABLE_PKCS11
+static char *
+sanitize_pkcs11_provider(const char *provider)
+{
+	struct pkcs11_uri *uri = NULL;
+	char *sane_uri, *module_path = NULL; /* default path */
+	char canonical_provider[PATH_MAX];
+
+	if (provider == NULL)
+		return NULL;
+
+	if (strlen(provider) >= strlen(PKCS11_URI_SCHEME) &&
+	    strncmp(provider, PKCS11_URI_SCHEME,
+	    strlen(PKCS11_URI_SCHEME)) == 0) {
+		/* PKCS#11 URI */
+		uri = pkcs11_uri_init();
+		if (uri == NULL) {
+			error("Failed to init PKCS#11 URI");
+			return NULL;
+		}
+
+		if (pkcs11_uri_parse(provider, uri) != 0) {
+			error("Failed to parse PKCS#11 URI");
+			return NULL;
+		}
+		/* validate also provider from URI */
+		if (uri->module_path)
+			module_path = strdup(uri->module_path);
+	} else
+		module_path = strdup(provider); /* simple path */
+
+	if (module_path != NULL) { /* do not validate default NULL path in URI */
+		if (realpath(module_path, canonical_provider) == NULL) {
+			verbose("failed PKCS#11 provider \"%.100s\": realpath: %s",
+			    module_path, strerror(errno));
+			free(module_path);
+			pkcs11_uri_cleanup(uri);
+			return NULL;
+		}
+		free(module_path);
+		if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
+			verbose("refusing PKCS#11 provider \"%.100s\": "
+			    "not allowed", canonical_provider);
+			pkcs11_uri_cleanup(uri);
+			return NULL;
+		}
+
+		/* copy verified and sanitized provider path back to the uri */
+		if (uri) {
+			free(uri->module_path);
+			uri->module_path = xstrdup(canonical_provider);
+		}
+	}
+
+	if (uri) {
+		sane_uri = pkcs11_uri_get(uri);
+		pkcs11_uri_cleanup(uri);
+		return sane_uri;
+	} else {
+		return xstrdup(canonical_provider); /* simple path */
+	}
+}
+
 static void
 process_add_smartcard_key(SocketEntry *e)
 {
-	char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
+	char *provider = NULL, *pin = NULL, *sane_uri = NULL;
 	char **comments = NULL;
 	int r, i, count = 0, success = 0, confirm = 0;
 	u_int seconds = 0;
@@ -1393,33 +1455,28 @@ process_add_smartcard_key(SocketEntry *e)
 		error_f("failed to parse constraints");
 		goto send;
 	}
-	if (realpath(provider, canonical_provider) == NULL) {
-		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
-		    provider, strerror(errno));
-		goto send;
-	}
-	if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
-		verbose("refusing PKCS#11 add of \"%.100s\": "
-		    "provider not allowed", canonical_provider);
+
+	sane_uri = sanitize_pkcs11_provider(provider);
+	if (sane_uri == NULL)
 		goto send;
-	}
-	debug_f("add %.100s", canonical_provider);
+
 	if (lifetime && !death)
 		death = monotime() + lifetime;
 
-	count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
+	debug_f("add %.100s", sane_uri);
+	count = pkcs11_add_provider(sane_uri, pin, &keys, &comments);
 	for (i = 0; i < count; i++) {
 		k = keys[i];
 		if (lookup_identity(k) == NULL) {
 			id = xcalloc(1, sizeof(Identity));
 			id->key = k;
 			keys[i] = NULL; /* transferred */
-			id->provider = xstrdup(canonical_provider);
+			id->provider = xstrdup(sane_uri);
 			if (*comments[i] != '\0') {
 				id->comment = comments[i];
 				comments[i] = NULL; /* transferred */
 			} else {
-				id->comment = xstrdup(canonical_provider);
+				id->comment = xstrdup(sane_uri);
 			}
 			id->death = death;
 			id->confirm = confirm;
@@ -1438,6 +1495,7 @@ process_add_smartcard_key(SocketEntry *e)
 send:
 	free(pin);
 	free(provider);
+	free(sane_uri);
 	free(keys);
 	free(comments);
 	free_dest_constraints(dest_constraints, ndest_constraints);
@@ -1447,7 +1505,7 @@ send:
 static void
 process_remove_smartcard_key(SocketEntry *e)
 {
-	char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
+	char *provider = NULL, *pin = NULL, *sane_uri = NULL;
 	int r, success = 0;
 	Identity *id, *nxt;
 
@@ -1459,30 +1517,29 @@ process_remove_smartcard_key(SocketEntry *e)
 	}
 	free(pin);
 
-	if (realpath(provider, canonical_provider) == NULL) {
-		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
-		    provider, strerror(errno));
+	sane_uri = sanitize_pkcs11_provider(provider);
+	if (sane_uri == NULL)
 		goto send;
-	}
 
-	debug_f("remove %.100s", canonical_provider);
+	debug_f("remove %.100s", sane_uri);
 	for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
 		nxt = TAILQ_NEXT(id, next);
 		/* Skip file--based keys */
 		if (id->provider == NULL)
 			continue;
-		if (!strcmp(canonical_provider, id->provider)) {
+		if (!strcmp(sane_uri, id->provider)) {
 			TAILQ_REMOVE(&idtab->idlist, id, next);
 			free_identity(id);
 			idtab->nentries--;
 		}
 	}
-	if (pkcs11_del_provider(canonical_provider) == 0)
+	if (pkcs11_del_provider(sane_uri) == 0)
 		success = 1;
 	else
 		error_f("pkcs11_del_provider failed");
 send:
 	free(provider);
+	free(sane_uri);
 	send_status(e, success);
 }
 #endif /* ENABLE_PKCS11 */
diff --git a/ssh-keygen.c b/ssh-keygen.c
index 9b2beda..1a7de44 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -864,8 +864,11 @@ do_download(struct passwd *pw)
 			free(fp);
 		} else {
 			(void) sshkey_write(keys[i], stdout); /* XXX check */
-			fprintf(stdout, "%s%s\n",
-			    *(comments[i]) == '\0' ? "" : " ", comments[i]);
+			if (*(comments[i]) != '\0') {
+				fprintf(stdout, " %s", comments[i]);
+			}
+			(void) pkcs11_uri_write(keys[i], stdout);
+			fprintf(stdout, "\n");
 		}
 		free(comments[i]);
 		sshkey_free(keys[i]);
diff --git a/ssh-pkcs11-client.c b/ssh-pkcs11-client.c
index cfd833d..9e4f02b 100644
--- a/ssh-pkcs11-client.c
+++ b/ssh-pkcs11-client.c
@@ -323,6 +323,8 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
 	u_int nkeys, i;
 	struct sshbuf *msg;
 
+	debug_f("called, name = %s", name);
+
 	if (fd < 0 && pkcs11_start_helper() < 0)
 		return (-1);
 
@@ -342,6 +344,7 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
 		*keysp = xcalloc(nkeys, sizeof(struct sshkey *));
 		if (labelsp)
 			*labelsp = xcalloc(nkeys, sizeof(char *));
+		debug_f("nkeys = %u", nkeys);
 		for (i = 0; i < nkeys; i++) {
 			/* XXX clean up properly instead of fatal() */
 			if ((r = sshbuf_get_string(msg, &blob, &blen)) != 0 ||
diff --git a/ssh-pkcs11-uri.c b/ssh-pkcs11-uri.c
new file mode 100644
index 0000000..a8a4946
--- /dev/null
+++ b/ssh-pkcs11-uri.c
@@ -0,0 +1,419 @@
+/*
+ * Copyright (c) 2017 Red Hat
+ *
+ * Authors: Jakub Jelen <jjelen@redhat.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "includes.h"
+
+#ifdef ENABLE_PKCS11
+
+#include <stdio.h>
+#include <string.h>
+
+#include "sshkey.h"
+#include "sshbuf.h"
+#include "log.h"
+
+#define CRYPTOKI_COMPAT
+#include "pkcs11.h"
+
+#include "ssh-pkcs11-uri.h"
+
+#define PKCS11_URI_PATH_SEPARATOR ";"
+#define PKCS11_URI_QUERY_SEPARATOR "&"
+#define PKCS11_URI_VALUE_SEPARATOR "="
+#define PKCS11_URI_ID "id"
+#define PKCS11_URI_TOKEN "token"
+#define PKCS11_URI_OBJECT "object"
+#define PKCS11_URI_LIB_MANUF "library-manufacturer"
+#define PKCS11_URI_MANUF "manufacturer"
+#define PKCS11_URI_MODULE_PATH "module-path"
+#define PKCS11_URI_PIN_VALUE "pin-value"
+
+/* Keyword tokens. */
+typedef enum {
+	pId, pToken, pObject, pLibraryManufacturer, pManufacturer, pModulePath,
+	pPinValue, pBadOption
+} pkcs11uriOpCodes;
+
+/* Textual representation of the tokens. */
+static struct {
+	const char *name;
+	pkcs11uriOpCodes opcode;
+} keywords[] = {
+	{ PKCS11_URI_ID, pId },
+	{ PKCS11_URI_TOKEN, pToken },
+	{ PKCS11_URI_OBJECT, pObject },
+	{ PKCS11_URI_LIB_MANUF, pLibraryManufacturer },
+	{ PKCS11_URI_MANUF, pManufacturer },
+	{ PKCS11_URI_MODULE_PATH, pModulePath },
+	{ PKCS11_URI_PIN_VALUE, pPinValue },
+	{ NULL, pBadOption }
+};
+
+static pkcs11uriOpCodes
+parse_token(const char *cp)
+{
+	u_int i;
+
+	for (i = 0; keywords[i].name; i++)
+		if (strncasecmp(cp, keywords[i].name,
+		    strlen(keywords[i].name)) == 0)
+			return keywords[i].opcode;
+
+	return pBadOption;
+}
+
+int
+percent_decode(char *data, char **outp)
+{
+	char tmp[3];
+	char *out, *tmp_end;
+	char *p = data;
+	long value;
+	size_t outlen = 0;
+
+	out = malloc(strlen(data)+1); /* upper bound */
+	if (out == NULL)
+		return -1;
+	while (*p != '\0') {
+		switch (*p) {
+		case '%':
+			p++;
+			if (*p == '\0')
+				goto fail;
+			tmp[0] = *p++;
+			if (*p == '\0')
+				goto fail;
+			tmp[1] = *p++;
+			tmp[2] = '\0';
+			tmp_end = NULL;
+			value = strtol(tmp, &tmp_end, 16);
+			if (tmp_end != tmp+2)
+				goto fail;
+			else
+				out[outlen++] = (char) value;
+			break;
+		default:
+			out[outlen++] = *p++;
+			break;
+		}
+	}
+
+	/* zero terminate */
+	out[outlen] = '\0';
+	*outp = out;
+	return outlen;
+fail:
+	free(out);
+	return -1;
+}
+
+struct sshbuf *
+percent_encode(const char *data, size_t length, const char *allow_list)
+{
+	struct sshbuf *b = NULL;
+	char tmp[4], *cp;
+	size_t i;
+
+	if ((b = sshbuf_new()) == NULL)
+		return NULL;
+	for (i = 0; i < length; i++) {
+		cp = strchr(allow_list, data[i]);
+		/* if c is specified as '\0' pointer to terminator is returned !! */
+		if (cp != NULL && *cp != '\0') {
+			if (sshbuf_put(b, &data[i], 1) != 0)
+				goto err;
+		} else
+			if (snprintf(tmp, 4, "%%%02X", (unsigned char) data[i]) < 3
+			    || sshbuf_put(b, tmp, 3) != 0)
+				goto err;
+	}
+	if (sshbuf_put(b, "\0", 1) == 0)
+		return b;
+err:
+	sshbuf_free(b);
+	return NULL;
+}
+
+char *
+pkcs11_uri_append(char *part, const char *separator, const char *key,
+    struct sshbuf *value)
+{
+	char *new_part;
+	size_t size = 0;
+
+	if (value == NULL)
+		return NULL;
+
+	size = asprintf(&new_part,
+	    "%s%s%s"  PKCS11_URI_VALUE_SEPARATOR "%s",
+	    (part != NULL ? part : ""),
+	    (part != NULL ? separator : ""),
+	    key, sshbuf_ptr(value));
+	sshbuf_free(value);
+	free(part);
+
+	if (size <= 0)
+		return NULL;
+	return new_part;
+}
+
+char *
+pkcs11_uri_get(struct pkcs11_uri *uri)
+{
+	size_t size = 0;
+	char *p = NULL, *path = NULL, *query = NULL;
+
+	/* compose a percent-encoded ID */
+	if (uri->id_len > 0) {
+		struct sshbuf *key_id = percent_encode(uri->id, uri->id_len, "");
+		path = pkcs11_uri_append(path, PKCS11_URI_PATH_SEPARATOR,
+		    PKCS11_URI_ID, key_id);
+		if (path == NULL)
+			goto err;
+	}
+
+	/* Write object label */
+	if (uri->object) {
+		struct sshbuf *label = percent_encode(uri->object, strlen(uri->object),
+		    PKCS11_URI_WHITELIST);
+		path = pkcs11_uri_append(path, PKCS11_URI_PATH_SEPARATOR,
+		    PKCS11_URI_OBJECT, label);
+		if (path == NULL)
+			goto err;
+	}
+
+	/* Write token label */
+	if (uri->token) {
+		struct sshbuf *label = percent_encode(uri->token, strlen(uri->token),
+		    PKCS11_URI_WHITELIST);
+		path = pkcs11_uri_append(path, PKCS11_URI_PATH_SEPARATOR,
+		    PKCS11_URI_TOKEN, label);
+		if (path == NULL)
+			goto err;
+	}
+
+	/* Write manufacturer */
+	if (uri->manuf) {
+		struct sshbuf *manuf = percent_encode(uri->manuf,
+		    strlen(uri->manuf), PKCS11_URI_WHITELIST);
+		path = pkcs11_uri_append(path, PKCS11_URI_PATH_SEPARATOR,
+		    PKCS11_URI_MANUF, manuf);
+		if (path == NULL)
+			goto err;
+	}
+
+	/* Write module_path */
+	if (uri->module_path) {
+		struct sshbuf *module = percent_encode(uri->module_path,
+		    strlen(uri->module_path), PKCS11_URI_WHITELIST "/");
+		query = pkcs11_uri_append(query, PKCS11_URI_QUERY_SEPARATOR,
+		    PKCS11_URI_MODULE_PATH, module);
+		if (query == NULL)
+			goto err;
+	}
+
+	size = asprintf(&p, PKCS11_URI_SCHEME "%s%s%s",
+	    path != NULL ? path : "",
+	    query != NULL ? "?" : "",
+	    query != NULL ? query : "");
+err:
+	free(query);
+	free(path);
+	if (size <= 0)
+		return NULL;
+	return p;
+}
+
+struct pkcs11_uri *
+pkcs11_uri_init()
+{
+	struct pkcs11_uri *d = calloc(1, sizeof(struct pkcs11_uri));
+	return d;
+}
+
+void
+pkcs11_uri_cleanup(struct pkcs11_uri *pkcs11)
+{
+	if (pkcs11 == NULL) {
+		return;
+	}
+
+	free(pkcs11->id);
+	free(pkcs11->module_path);
+	free(pkcs11->token);
+	free(pkcs11->object);
+	free(pkcs11->lib_manuf);
+	free(pkcs11->manuf);
+	if (pkcs11->pin)
+		freezero(pkcs11->pin, strlen(pkcs11->pin));
+	free(pkcs11);
+}
+
+int
+pkcs11_uri_parse(const char *uri, struct pkcs11_uri *pkcs11)
+{
+	char *saveptr1, *saveptr2, *str1, *str2, *tok;
+	int rv = 0, len;
+	char *p = NULL;
+
+	size_t scheme_len = strlen(PKCS11_URI_SCHEME);
+	if (strlen(uri) < scheme_len || /* empty URI matches everything */
+	    strncmp(uri, PKCS11_URI_SCHEME, scheme_len) != 0) {
+		error_f("The '%s' does not look like PKCS#11 URI", uri);
+		return -1;
+	}
+
+	if (pkcs11 == NULL) {
+		error_f("Bad arguments. The pkcs11 can't be null");
+		return -1;
+	}
+
+	/* skip URI schema name */
+	p = strdup(uri);
+	str1 = p;
+
+	/* everything before ? */
+	tok = strtok_r(str1, "?", &saveptr1);
+	if (tok == NULL) {
+		error_f("pk11-path expected, got EOF");
+		rv = -1;
+		goto out;
+	}
+
+	/* skip URI schema name:
+	 * the scheme ensures that there is at least something before "?"
+	 * allowing empty pk11-path. Resulting token at worst pointing to
+	 * \0 byte */
+	tok = tok + scheme_len;
+
+	/* parse pk11-path */
+	for (str2 = tok; ; str2 = NULL) {
+		char **charptr, *arg = NULL;
+		pkcs11uriOpCodes opcode;
+		tok = strtok_r(str2, PKCS11_URI_PATH_SEPARATOR, &saveptr2);
+		if (tok == NULL)
+			break;
+		opcode = parse_token(tok);
+		if (opcode != pBadOption)
+			arg = tok + strlen(keywords[opcode].name) + 1; /* separator "=" */
+
+		switch (opcode) {
+		case pId:
+			/* CKA_ID */
+			if (pkcs11->id != NULL) {
+				verbose_f("The id already set in the PKCS#11 URI");
+				rv = -1;
+				goto out;
+			}
+			len = percent_decode(arg, &pkcs11->id);
+			if (len <= 0) {
+				verbose_f("Failed to percent-decode CKA_ID: %s", arg);
+				rv = -1;
+				goto out;
+			} else
+				pkcs11->id_len = len;
+			debug3_f("Setting CKA_ID = %s from PKCS#11 URI", arg);
+			break;
+		case pToken:
+			/* CK_TOKEN_INFO -> label */
+			charptr = &pkcs11->token;
+ parse_string:
+			if (*charptr != NULL) {
+				verbose_f("The %s already set in the PKCS#11 URI",
+				    keywords[opcode].name);
+				rv = -1;
+				goto out;
+			}
+			percent_decode(arg, charptr);
+			debug3_f("Setting %s = %s from PKCS#11 URI",
+			    keywords[opcode].name, *charptr);
+			break;
+
+		case pObject:
+			/* CK_TOKEN_INFO -> manufacturerID */
+			charptr = &pkcs11->object;
+			goto parse_string;
+
+		case pManufacturer:
+			/* CK_TOKEN_INFO -> manufacturerID */
+			charptr = &pkcs11->manuf;
+			goto parse_string;
+
+		case pLibraryManufacturer:
+			/* CK_INFO -> manufacturerID */
+			charptr = &pkcs11->lib_manuf;
+			goto parse_string;
+
+		default:
+			/* Unrecognized attribute in the URI path SHOULD be error */
+			verbose_f("Unknown part of path in PKCS#11 URI: %s", tok);
+		}
+	}
+
+	tok = strtok_r(NULL, "?", &saveptr1);
+	if (tok == NULL) {
+		goto out;
+	}
+	/* parse pk11-query (optional) */
+	for (str2 = tok; ; str2 = NULL) {
+		char *arg;
+		pkcs11uriOpCodes opcode;
+		tok = strtok_r(str2, PKCS11_URI_QUERY_SEPARATOR, &saveptr2);
+		if (tok == NULL)
+			break;
+		opcode = parse_token(tok);
+		if (opcode != pBadOption)
+			arg = tok + strlen(keywords[opcode].name) + 1; /* separator "=" */
+
+		switch (opcode) {
+		case pModulePath:
+			/* module-path is PKCS11Provider */
+			if (pkcs11->module_path != NULL) {
+				verbose_f("Multiple module-path attributes are"
+				    "not supported the PKCS#11 URI");
+				rv = -1;
+				goto out;
+			}
+			percent_decode(arg, &pkcs11->module_path);
+			debug3_f("Setting PKCS11Provider = %s from PKCS#11 URI",
+			    pkcs11->module_path);
+			break;
+
+		case pPinValue:
+			/* pin-value */
+			if (pkcs11->pin != NULL) {
+				verbose_f("Multiple pin-value attributes are"
+				    "not supported the PKCS#11 URI");
+				rv = -1;
+				goto out;
+			}
+			percent_decode(arg, &pkcs11->pin);
+			debug3_f("Setting PIN from PKCS#11 URI");
+			break;
+
+		default:
+			/* Unrecognized attribute in the URI query SHOULD be ignored */
+			verbose_f("Unknown part of query in PKCS#11 URI: %s", tok);
+		}
+	}
+out:
+	free(p);
+	return rv;
+}
+
+#endif /* ENABLE_PKCS11 */
diff --git a/ssh-pkcs11-uri.h b/ssh-pkcs11-uri.h
new file mode 100644
index 0000000..942a5a5
--- /dev/null
+++ b/ssh-pkcs11-uri.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2017 Red Hat
+ *
+ * Authors: Jakub Jelen <jjelen@redhat.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#define PKCS11_URI_SCHEME "pkcs11:"
+#define PKCS11_URI_WHITELIST	"abcdefghijklmnopqrstuvwxyz" \
+				"ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
+				"0123456789_-.()"
+
+struct pkcs11_uri {
+	/* path */
+	char *id;
+	size_t id_len;
+	char *token;
+	char *object;
+	char *lib_manuf;
+	char *manuf;
+	/* query */
+	char *module_path;
+	char *pin; /* Only parsed, but not printed */
+};
+
+struct	 pkcs11_uri *pkcs11_uri_init();
+void	 pkcs11_uri_cleanup(struct pkcs11_uri *);
+int	 pkcs11_uri_parse(const char *, struct pkcs11_uri *);
+struct	 pkcs11_uri *pkcs11_uri_init();
+char	*pkcs11_uri_get(struct pkcs11_uri *uri);
+
diff --git a/ssh-pkcs11.c b/ssh-pkcs11.c
index b2e2b32..720ae2a 100644
--- a/ssh-pkcs11.c
+++ b/ssh-pkcs11.c
@@ -55,8 +55,8 @@ struct pkcs11_slotinfo {
 	int			logged_in;
 };
 
-struct pkcs11_provider {
-	char			*name;
+struct pkcs11_module {
+	char			*module_path;
 	void			*handle;
 	CK_FUNCTION_LIST	*function_list;
 	CK_INFO			info;
@@ -65,6 +65,13 @@ struct pkcs11_provider {
 	struct pkcs11_slotinfo	*slotinfo;
 	int			valid;
 	int			refcount;
+};
+
+struct pkcs11_provider {
+	char			*name;
+	struct pkcs11_module	*module; /* can be shared between various providers */
+	int			refcount;
+	int			valid;
 	TAILQ_ENTRY(pkcs11_provider) next;
 };
 
@@ -75,6 +82,7 @@ struct pkcs11_key {
 	CK_ULONG		slotidx;
 	char			*keyid;
 	int			keyid_len;
+	char			*label;
 };
 
 int pkcs11_interactive = 0;
@@ -106,26 +114,61 @@ pkcs11_init(int interactive)
  * this is called when a provider gets unregistered.
  */
 static void
-pkcs11_provider_finalize(struct pkcs11_provider *p)
+pkcs11_module_finalize(struct pkcs11_module *m)
 {
 	CK_RV rv;
 	CK_ULONG i;
 
-	debug_f("provider \"%s\" refcount %d valid %d",
-	    p->name, p->refcount, p->valid);
-	if (!p->valid)
+	debug_f("%p refcount %d valid %d", m, m->refcount, m->valid);
+	if (!m->valid)
 		return;
-	for (i = 0; i < p->nslots; i++) {
-		if (p->slotinfo[i].session &&
-		    (rv = p->function_list->C_CloseSession(
-		    p->slotinfo[i].session)) != CKR_OK)
+	for (i = 0; i < m->nslots; i++) {
+		if (m->slotinfo[i].session &&
+		    (rv = m->function_list->C_CloseSession(
+		    m->slotinfo[i].session)) != CKR_OK)
 			error("C_CloseSession failed: %lu", rv);
 	}
-	if ((rv = p->function_list->C_Finalize(NULL)) != CKR_OK)
+	if ((rv = m->function_list->C_Finalize(NULL)) != CKR_OK)
 		error("C_Finalize failed: %lu", rv);
+	m->valid = 0;
+	m->function_list = NULL;
+	dlclose(m->handle);
+}
+
+/*
+ * remove a reference to the pkcs11 module.
+ * called when a provider is unregistered.
+ */
+static void
+pkcs11_module_unref(struct pkcs11_module *m)
+{
+	debug_f("%p refcount %d", m, m->refcount);
+	if (--m->refcount <= 0) {
+		pkcs11_module_finalize(m);
+		if (m->valid)
+			error_f("%p still valid", m);
+		free(m->slotlist);
+		free(m->slotinfo);
+		free(m->module_path);
+		free(m);
+	}
+}
+
+/*
+ * finalize a provider shared library, it's no longer usable.
+ * however, there might still be keys referencing this provider,
+ * so the actual freeing of memory is handled by pkcs11_provider_unref().
+ * this is called when a provider gets unregistered.
+ */
+static void
+pkcs11_provider_finalize(struct pkcs11_provider *p)
+{
+	debug_f("%p refcount %d valid %d", p, p->refcount, p->valid);
+	if (!p->valid)
+		return;
+	pkcs11_module_unref(p->module);
+	p->module = NULL;
 	p->valid = 0;
-	p->function_list = NULL;
-	dlclose(p->handle);
 }
 
 /*
@@ -137,11 +180,9 @@ pkcs11_provider_unref(struct pkcs11_provider *p)
 {
 	debug_f("provider \"%s\" refcount %d", p->name, p->refcount);
 	if (--p->refcount <= 0) {
-		if (p->valid)
-			error_f("provider \"%s\" still valid", p->name);
 		free(p->name);
-		free(p->slotlist);
-		free(p->slotinfo);
+		if (p->module)
+			pkcs11_module_unref(p->module);
 		free(p);
 	}
 }
@@ -159,6 +200,20 @@ pkcs11_terminate(void)
 	}
 }
 
+/* lookup provider by module path */
+static struct pkcs11_module *
+pkcs11_provider_lookup_module(char *module_path)
+{
+	struct pkcs11_provider *p;
+
+	TAILQ_FOREACH(p, &pkcs11_providers, next) {
+		debug("check %p %s (%s)", p, p->name, p->module->module_path);
+		if (!strcmp(module_path, p->module->module_path))
+			return (p->module);
+	}
+	return (NULL);
+}
+
 /* lookup provider by name */
 static struct pkcs11_provider *
 pkcs11_provider_lookup(char *provider_id)
@@ -173,19 +228,55 @@ pkcs11_provider_lookup(char *provider_id)
 	return (NULL);
 }
 
+int pkcs11_del_provider_by_uri(struct pkcs11_uri *);
+
 /* unregister provider by name */
 int
 pkcs11_del_provider(char *provider_id)
+{
+	int rv;
+	struct pkcs11_uri *uri;
+
+	debug_f("called, provider_id = %s", provider_id);
+
+      if (provider_id == NULL)
+          return 0;
+
+	uri = pkcs11_uri_init();
+	if (uri == NULL)
+		fatal("Failed to init PKCS#11 URI");
+
+	if (strlen(provider_id) >= strlen(PKCS11_URI_SCHEME) &&
+	    strncmp(provider_id, PKCS11_URI_SCHEME, strlen(PKCS11_URI_SCHEME)) == 0) {
+		if (pkcs11_uri_parse(provider_id, uri) != 0)
+			fatal("Failed to parse PKCS#11 URI");
+	} else {
+		uri->module_path = strdup(provider_id);
+	}
+
+	rv = pkcs11_del_provider_by_uri(uri);
+	pkcs11_uri_cleanup(uri);
+	return rv;
+}
+
+/* unregister provider by PKCS#11 URI */
+int
+pkcs11_del_provider_by_uri(struct pkcs11_uri *uri)
 {
 	struct pkcs11_provider *p;
+	int rv = -1;
+	char *provider_uri = pkcs11_uri_get(uri);
 
-	if ((p = pkcs11_provider_lookup(provider_id)) != NULL) {
+	debug3_f("called with provider %s", provider_uri);
+
+	if ((p = pkcs11_provider_lookup(provider_uri)) != NULL) {
 		TAILQ_REMOVE(&pkcs11_providers, p, next);
 		pkcs11_provider_finalize(p);
 		pkcs11_provider_unref(p);
-		return (0);
+		rv = 0;
 	}
-	return (-1);
+	free(provider_uri);
+	return rv;
 }
 
 static RSA_METHOD *rsa_method;
@@ -195,6 +286,55 @@ static EC_KEY_METHOD *ec_key_method;
 static int ec_key_idx = 0;
 #endif /* OPENSSL_HAS_ECC && HAVE_EC_KEY_METHOD_NEW */
 
+/*
+ * This can't be in the ssh-pkcs11-uri, becase we can not depend on
+ * PKCS#11 structures in ssh-agent (using client-helper communication)
+ */
+int
+pkcs11_uri_write(const struct sshkey *key, FILE *f)
+{
+	char *p = NULL;
+	struct pkcs11_uri uri;
+	struct pkcs11_key *k11;
+
+	/* sanity - is it a RSA key with associated app_data? */
+	switch (key->type) {
+	case KEY_RSA:
+		k11 = RSA_get_ex_data(key->rsa, rsa_idx);
+		break;
+#ifdef HAVE_EC_KEY_METHOD_NEW
+	case KEY_ECDSA:
+		k11 = EC_KEY_get_ex_data(key->ecdsa, ec_key_idx);
+		break;
+#endif
+	default:
+		error("Unknown key type %d", key->type);
+		return -1;
+	}
+	if (k11 == NULL) {
+		error("Failed to get ex_data for key type %d", key->type);
+		return (-1);
+	}
+
+	/* omit type -- we are looking for private-public or private-certificate pairs */
+	uri.id = k11->keyid;
+	uri.id_len = k11->keyid_len;
+	uri.token = k11->provider->module->slotinfo[k11->slotidx].token.label;
+	uri.object = k11->label;
+	uri.module_path = k11->provider->module->module_path;
+	uri.lib_manuf = k11->provider->module->info.manufacturerID;
+	uri.manuf = k11->provider->module->slotinfo[k11->slotidx].token.manufacturerID;
+
+	p = pkcs11_uri_get(&uri);
+	/* do not cleanup -- we do not allocate here, only reference */
+	if (p == NULL)
+		return -1;
+
+	fprintf(f, " %s", p);
+	free(p);
+	return 0;
+}
+
 /* release a wrapped object */
 static void
 pkcs11_k11_free(void *parent, void *ptr, CRYPTO_EX_DATA *ad, int idx,
@@ -208,6 +348,7 @@ pkcs11_k11_free(void *parent, void *ptr, CRYPTO_EX_DATA *ad, int idx,
 	if (k11->provider)
 		pkcs11_provider_unref(k11->provider);
 	free(k11->keyid);
+	free(k11->label);
 	free(k11);
 }
 
@@ -222,8 +363,8 @@ pkcs11_find(struct pkcs11_provider *p, CK_ULONG slotidx, CK_ATTRIBUTE *attr,
 	CK_RV			rv;
 	int			ret = -1;
 
-	f = p->function_list;
-	session = p->slotinfo[slotidx].session;
+	f = p->module->function_list;
+	session = p->module->slotinfo[slotidx].session;
 	if ((rv = f->C_FindObjectsInit(session, attr, nattr)) != CKR_OK) {
 		error("C_FindObjectsInit failed (nattr %lu): %lu", nattr, rv);
 		return (-1);
@@ -262,12 +403,12 @@ pkcs11_login_slot(struct pkcs11_provider *provider, struct pkcs11_slotinfo *si,
 	else {
 		snprintf(prompt, sizeof(prompt), "Enter PIN for '%s': ",
 		    si->token.label);
-		if ((pin = read_passphrase(prompt, RP_ALLOW_EOF)) == NULL) {
+		if ((pin = read_passphrase(prompt, RP_ALLOW_EOF|RP_ALLOW_STDIN)) == NULL) {
 			debug_f("no pin specified");
 			return (-1);	/* bail out */
 		}
 	}
-	rv = provider->function_list->C_Login(si->session, type, (u_char *)pin,
+	rv = provider->module->function_list->C_Login(si->session, type, (u_char *)pin,
 	    (pin != NULL) ? strlen(pin) : 0);
 	if (pin != NULL)
 		freezero(pin, strlen(pin));
@@ -297,13 +438,14 @@ pkcs11_login_slot(struct pkcs11_provider *provider, struct pkcs11_slotinfo *si,
 static int
 pkcs11_login(struct pkcs11_key *k11, CK_USER_TYPE type)
 {
-	if (k11 == NULL || k11->provider == NULL || !k11->provider->valid) {
+	if (k11 == NULL || k11->provider == NULL || !k11->provider->valid ||
+	    k11->provider->module == NULL || !k11->provider->module->valid) {
 		error("no pkcs11 (valid) provider found");
 		return (-1);
 	}
 
 	return pkcs11_login_slot(k11->provider,
-	    &k11->provider->slotinfo[k11->slotidx], type);
+	    &k11->provider->module->slotinfo[k11->slotidx], type);
 }
 
 
@@ -319,13 +461,14 @@ pkcs11_check_obj_bool_attrib(struct pkcs11_key *k11, CK_OBJECT_HANDLE obj,
 
 	*val = 0;
 
-	if (!k11->provider || !k11->provider->valid) {
+	if (!k11->provider || !k11->provider->valid ||
+	    !k11->provider->module || !k11->provider->module->valid) {
 		error("no pkcs11 (valid) provider found");
 		return (-1);
 	}
 
-	f = k11->provider->function_list;
-	si = &k11->provider->slotinfo[k11->slotidx];
+	f = k11->provider->module->function_list;
+	si = &k11->provider->module->slotinfo[k11->slotidx];
 
 	attr.type = type;
 	attr.pValue = &flag;
@@ -356,13 +499,14 @@ pkcs11_get_key(struct pkcs11_key *k11, CK_MECHANISM_TYPE mech_type)
 	int			 always_auth = 0;
 	int			 did_login = 0;
 
-	if (!k11->provider || !k11->provider->valid) {
+	if (!k11->provider || !k11->provider->valid ||
+	    !k11->provider->module || !k11->provider->module->valid) {
 		error("no pkcs11 (valid) provider found");
 		return (-1);
 	}
 
-	f = k11->provider->function_list;
-	si = &k11->provider->slotinfo[k11->slotidx];
+	f = k11->provider->module->function_list;
+	si = &k11->provider->module->slotinfo[k11->slotidx];
 
 	if ((si->token.flags & CKF_LOGIN_REQUIRED) && !si->logged_in) {
 		if (pkcs11_login(k11, CKU_USER) < 0) {
@@ -439,8 +583,8 @@ pkcs11_rsa_private_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa,
 		return (-1);
 	}
 
-	f = k11->provider->function_list;
-	si = &k11->provider->slotinfo[k11->slotidx];
+	f = k11->provider->module->function_list;
+	si = &k11->provider->module->slotinfo[k11->slotidx];
 	tlen = RSA_size(rsa);
 
 	/* XXX handle CKR_BUFFER_TOO_SMALL */
@@ -484,7 +628,7 @@ pkcs11_rsa_start_wrapper(void)
 /* redirect private key operations for rsa key to pkcs11 token */
 static int
 pkcs11_rsa_wrap(struct pkcs11_provider *provider, CK_ULONG slotidx,
-    CK_ATTRIBUTE *keyid_attrib, RSA *rsa)
+    CK_ATTRIBUTE *keyid_attrib, CK_ATTRIBUTE *label_attrib, RSA *rsa)
 {
 	struct pkcs11_key	*k11;
 
@@ -502,6 +646,12 @@ pkcs11_rsa_wrap(struct pkcs11_provider *provider, CK_ULONG slotidx,
 		memcpy(k11->keyid, keyid_attrib->pValue, k11->keyid_len);
 	}
 
+	if (label_attrib->ulValueLen > 0 ) {
+		k11->label = xmalloc(label_attrib->ulValueLen+1);
+		memcpy(k11->label, label_attrib->pValue, label_attrib->ulValueLen);
+		k11->label[label_attrib->ulValueLen] = 0;
+	}
+
 	RSA_set_method(rsa, rsa_method);
 	RSA_set_ex_data(rsa, rsa_idx, k11);
 	return (0);
@@ -532,8 +682,8 @@ ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
 		return (NULL);
 	}
 
-	f = k11->provider->function_list;
-	si = &k11->provider->slotinfo[k11->slotidx];
+	f = k11->provider->module->function_list;
+	si = &k11->provider->module->slotinfo[k11->slotidx];
 
 	siglen = ECDSA_size(ec);
 	sig = xmalloc(siglen);
@@ -598,7 +748,7 @@ pkcs11_ecdsa_start_wrapper(void)
 
 static int
 pkcs11_ecdsa_wrap(struct pkcs11_provider *provider, CK_ULONG slotidx,
-    CK_ATTRIBUTE *keyid_attrib, EC_KEY *ec)
+    CK_ATTRIBUTE *keyid_attrib, CK_ATTRIBUTE *label_attrib, EC_KEY *ec)
 {
 	struct pkcs11_key	*k11;
 
@@ -615,6 +765,12 @@ pkcs11_ecdsa_wrap(struct pkcs11_provider *provider, CK_ULONG slotidx,
 		k11->keyid = xmalloc(k11->keyid_len);
 		memcpy(k11->keyid, keyid_attrib->pValue, k11->keyid_len);
 	}
+	if (label_attrib->ulValueLen > 0 ) {
+		k11->label = xmalloc(label_attrib->ulValueLen+1);
+		memcpy(k11->label, label_attrib->pValue, label_attrib->ulValueLen);
+		k11->label[label_attrib->ulValueLen] = 0;
+	}
+
 	EC_KEY_set_method(ec, ec_key_method);
 	EC_KEY_set_ex_data(ec, ec_key_idx, k11);
 
@@ -651,8 +807,8 @@ pkcs11_open_session(struct pkcs11_provider *p, CK_ULONG slotidx, char *pin,
 	CK_SESSION_HANDLE	session;
 	int			login_required, ret;
 
-	f = p->function_list;
-	si = &p->slotinfo[slotidx];
+	f = p->module->function_list;
+	si = &p->module->slotinfo[slotidx];
 
 	login_required = si->token.flags & CKF_LOGIN_REQUIRED;
 
@@ -662,9 +818,9 @@ pkcs11_open_session(struct pkcs11_provider *p, CK_ULONG slotidx, char *pin,
 		error("pin required");
 		return (-SSH_PKCS11_ERR_PIN_REQUIRED);
 	}
-	if ((rv = f->C_OpenSession(p->slotlist[slotidx], CKF_RW_SESSION|
+	if ((rv = f->C_OpenSession(p->module->slotlist[slotidx], CKF_RW_SESSION|
 	    CKF_SERIAL_SESSION, NULL, NULL, &session)) != CKR_OK) {
-		error("C_OpenSession failed: %lu", rv);
+		error("C_OpenSession failed for slot %lu: %lu", slotidx, rv);
 		return (-1);
 	}
 	if (login_required && pin != NULL && strlen(pin) != 0) {
@@ -700,7 +856,8 @@ static struct sshkey *
 pkcs11_fetch_ecdsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
     CK_OBJECT_HANDLE *obj)
 {
-	CK_ATTRIBUTE		 key_attr[3];
+	CK_ATTRIBUTE		 key_attr[4];
+	int			 nattr = 4;
 	CK_SESSION_HANDLE	 session;
 	CK_FUNCTION_LIST	*f = NULL;
 	CK_RV			 rv;
@@ -714,14 +871,15 @@ pkcs11_fetch_ecdsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 
 	memset(&key_attr, 0, sizeof(key_attr));
 	key_attr[0].type = CKA_ID;
-	key_attr[1].type = CKA_EC_POINT;
-	key_attr[2].type = CKA_EC_PARAMS;
+	key_attr[1].type = CKA_LABEL;
+	key_attr[2].type = CKA_EC_POINT;
+	key_attr[3].type = CKA_EC_PARAMS;
 
-	session = p->slotinfo[slotidx].session;
-	f = p->function_list;
+	session = p->module->slotinfo[slotidx].session;
+	f = p->module->function_list;
 
 	/* figure out size of the attributes */
-	rv = f->C_GetAttributeValue(session, *obj, key_attr, 3);
+	rv = f->C_GetAttributeValue(session, *obj, key_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_GetAttributeValue failed: %lu", rv);
 		return (NULL);
@@ -732,19 +890,19 @@ pkcs11_fetch_ecdsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 	 * ensure that none of the others are zero length.
 	 * XXX assumes CKA_ID is always first.
 	 */
-	if (key_attr[1].ulValueLen == 0 ||
-	    key_attr[2].ulValueLen == 0) {
+	if (key_attr[2].ulValueLen == 0 ||
+	    key_attr[3].ulValueLen == 0) {
 		error("invalid attribute length");
 		return (NULL);
 	}
 
 	/* allocate buffers for attributes */
-	for (i = 0; i < 3; i++)
+	for (i = 0; i < nattr; i++)
 		if (key_attr[i].ulValueLen > 0)
 			key_attr[i].pValue = xcalloc(1, key_attr[i].ulValueLen);
 
 	/* retrieve ID, public point and curve parameters of EC key */
-	rv = f->C_GetAttributeValue(session, *obj, key_attr, 3);
+	rv = f->C_GetAttributeValue(session, *obj, key_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_GetAttributeValue failed: %lu", rv);
 		goto fail;
@@ -756,8 +914,8 @@ pkcs11_fetch_ecdsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 		goto fail;
 	}
 
-	attrp = key_attr[2].pValue;
-	group = d2i_ECPKParameters(NULL, &attrp, key_attr[2].ulValueLen);
+	attrp = key_attr[3].pValue;
+	group = d2i_ECPKParameters(NULL, &attrp, key_attr[3].ulValueLen);
 	if (group == NULL) {
 		ossl_error("d2i_ECPKParameters failed");
 		goto fail;
@@ -768,13 +926,13 @@ pkcs11_fetch_ecdsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 		goto fail;
 	}
 
-	if (key_attr[1].ulValueLen <= 2) {
+	if (key_attr[2].ulValueLen <= 2) {
 		error("CKA_EC_POINT too small");
 		goto fail;
 	}
 
-	attrp = key_attr[1].pValue;
-	octet = d2i_ASN1_OCTET_STRING(NULL, &attrp, key_attr[1].ulValueLen);
+	attrp = key_attr[2].pValue;
+	octet = d2i_ASN1_OCTET_STRING(NULL, &attrp, key_attr[2].ulValueLen);
 	if (octet == NULL) {
 		ossl_error("d2i_ASN1_OCTET_STRING failed");
 		goto fail;
@@ -791,7 +949,7 @@ pkcs11_fetch_ecdsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 		goto fail;
 	}
 
-	if (pkcs11_ecdsa_wrap(p, slotidx, &key_attr[0], ec))
+	if (pkcs11_ecdsa_wrap(p, slotidx, &key_attr[0], &key_attr[1], ec))
 		goto fail;
 
 	key = sshkey_new(KEY_UNSPEC);
@@ -807,7 +965,7 @@ pkcs11_fetch_ecdsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 	ec = NULL;	/* now owned by key */
 
 fail:
-	for (i = 0; i < 3; i++)
+	for (i = 0; i < nattr; i++)
 		free(key_attr[i].pValue);
 	if (ec)
 		EC_KEY_free(ec);
@@ -824,7 +982,8 @@ static struct sshkey *
 pkcs11_fetch_rsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
     CK_OBJECT_HANDLE *obj)
 {
-	CK_ATTRIBUTE		 key_attr[3];
+	CK_ATTRIBUTE		 key_attr[4];
+	int			 nattr = 4;
 	CK_SESSION_HANDLE	 session;
 	CK_FUNCTION_LIST	*f = NULL;
 	CK_RV			 rv;
@@ -835,14 +994,15 @@ pkcs11_fetch_rsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 
 	memset(&key_attr, 0, sizeof(key_attr));
 	key_attr[0].type = CKA_ID;
-	key_attr[1].type = CKA_MODULUS;
-	key_attr[2].type = CKA_PUBLIC_EXPONENT;
+	key_attr[1].type = CKA_LABEL;
+	key_attr[2].type = CKA_MODULUS;
+	key_attr[3].type = CKA_PUBLIC_EXPONENT;
 
-	session = p->slotinfo[slotidx].session;
-	f = p->function_list;
+	session = p->module->slotinfo[slotidx].session;
+	f = p->module->function_list;
 
 	/* figure out size of the attributes */
-	rv = f->C_GetAttributeValue(session, *obj, key_attr, 3);
+	rv = f->C_GetAttributeValue(session, *obj, key_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_GetAttributeValue failed: %lu", rv);
 		return (NULL);
@@ -853,19 +1013,19 @@ pkcs11_fetch_rsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 	 * ensure that none of the others are zero length.
 	 * XXX assumes CKA_ID is always first.
 	 */
-	if (key_attr[1].ulValueLen == 0 ||
-	    key_attr[2].ulValueLen == 0) {
+	if (key_attr[2].ulValueLen == 0 ||
+	    key_attr[3].ulValueLen == 0) {
 		error("invalid attribute length");
 		return (NULL);
 	}
 
 	/* allocate buffers for attributes */
-	for (i = 0; i < 3; i++)
+	for (i = 0; i < nattr; i++)
 		if (key_attr[i].ulValueLen > 0)
 			key_attr[i].pValue = xcalloc(1, key_attr[i].ulValueLen);
 
 	/* retrieve ID, modulus and public exponent of RSA key */
-	rv = f->C_GetAttributeValue(session, *obj, key_attr, 3);
+	rv = f->C_GetAttributeValue(session, *obj, key_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_GetAttributeValue failed: %lu", rv);
 		goto fail;
@@ -877,8 +1037,8 @@ pkcs11_fetch_rsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 		goto fail;
 	}
 
-	rsa_n = BN_bin2bn(key_attr[1].pValue, key_attr[1].ulValueLen, NULL);
-	rsa_e = BN_bin2bn(key_attr[2].pValue, key_attr[2].ulValueLen, NULL);
+	rsa_n = BN_bin2bn(key_attr[2].pValue, key_attr[2].ulValueLen, NULL);
+	rsa_e = BN_bin2bn(key_attr[3].pValue, key_attr[3].ulValueLen, NULL);
 	if (rsa_n == NULL || rsa_e == NULL) {
 		error("BN_bin2bn failed");
 		goto fail;
@@ -887,7 +1047,7 @@ pkcs11_fetch_rsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 		fatal_f("set key");
 	rsa_n = rsa_e = NULL; /* transferred */
 
-	if (pkcs11_rsa_wrap(p, slotidx, &key_attr[0], rsa))
+	if (pkcs11_rsa_wrap(p, slotidx, &key_attr[0], &key_attr[1], rsa))
 		goto fail;
 
 	key = sshkey_new(KEY_UNSPEC);
@@ -902,7 +1062,7 @@ pkcs11_fetch_rsa_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 	rsa = NULL;	/* now owned by key */
 
 fail:
-	for (i = 0; i < 3; i++)
+	for (i = 0; i < nattr; i++)
 		free(key_attr[i].pValue);
 	RSA_free(rsa);
 
@@ -913,7 +1073,8 @@ static int
 pkcs11_fetch_x509_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
     CK_OBJECT_HANDLE *obj, struct sshkey **keyp, char **labelp)
 {
-	CK_ATTRIBUTE		 cert_attr[3];
+	CK_ATTRIBUTE		 cert_attr[4];
+	int			 nattr = 4;
 	CK_SESSION_HANDLE	 session;
 	CK_FUNCTION_LIST	*f = NULL;
 	CK_RV			 rv;
@@ -937,14 +1098,15 @@ pkcs11_fetch_x509_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 
 	memset(&cert_attr, 0, sizeof(cert_attr));
 	cert_attr[0].type = CKA_ID;
-	cert_attr[1].type = CKA_SUBJECT;
-	cert_attr[2].type = CKA_VALUE;
+	cert_attr[1].type = CKA_LABEL;
+	cert_attr[2].type = CKA_SUBJECT;
+	cert_attr[3].type = CKA_VALUE;
 
-	session = p->slotinfo[slotidx].session;
-	f = p->function_list;
+	session = p->module->slotinfo[slotidx].session;
+	f = p->module->function_list;
 
 	/* figure out size of the attributes */
-	rv = f->C_GetAttributeValue(session, *obj, cert_attr, 3);
+	rv = f->C_GetAttributeValue(session, *obj, cert_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_GetAttributeValue failed: %lu", rv);
 		return -1;
@@ -956,18 +1118,19 @@ pkcs11_fetch_x509_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 	 * XXX assumes CKA_ID is always first.
 	 */
 	if (cert_attr[1].ulValueLen == 0 ||
-	    cert_attr[2].ulValueLen == 0) {
+	    cert_attr[2].ulValueLen == 0 ||
+	    cert_attr[3].ulValueLen == 0) {
 		error("invalid attribute length");
 		return -1;
 	}
 
 	/* allocate buffers for attributes */
-	for (i = 0; i < 3; i++)
+	for (i = 0; i < nattr; i++)
 		if (cert_attr[i].ulValueLen > 0)
 			cert_attr[i].pValue = xcalloc(1, cert_attr[i].ulValueLen);
 
 	/* retrieve ID, subject and value of certificate */
-	rv = f->C_GetAttributeValue(session, *obj, cert_attr, 3);
+	rv = f->C_GetAttributeValue(session, *obj, cert_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_GetAttributeValue failed: %lu", rv);
 		goto out;
@@ -981,8 +1144,8 @@ pkcs11_fetch_x509_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 		subject = xstrdup("invalid subject");
 	X509_NAME_free(x509_name);
 
-	cp = cert_attr[2].pValue;
-	if ((x509 = d2i_X509(NULL, &cp, cert_attr[2].ulValueLen)) == NULL) {
+	cp = cert_attr[3].pValue;
+	if ((x509 = d2i_X509(NULL, &cp, cert_attr[3].ulValueLen)) == NULL) {
 		error("d2i_x509 failed");
 		goto out;
 	}
@@ -1002,7 +1165,7 @@ pkcs11_fetch_x509_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 			goto out;
 		}
 
-		if (pkcs11_rsa_wrap(p, slotidx, &cert_attr[0], rsa))
+		if (pkcs11_rsa_wrap(p, slotidx, &cert_attr[0], &cert_attr[1], rsa))
 			goto out;
 
 		key = sshkey_new(KEY_UNSPEC);
@@ -1032,7 +1195,7 @@ pkcs11_fetch_x509_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 			goto out;
 		}
 
-		if (pkcs11_ecdsa_wrap(p, slotidx, &cert_attr[0], ec))
+		if (pkcs11_ecdsa_wrap(p, slotidx, &cert_attr[0], &cert_attr[1], ec))
 			goto out;
 
 		key = sshkey_new(KEY_UNSPEC);
@@ -1052,7 +1215,7 @@ pkcs11_fetch_x509_pubkey(struct pkcs11_provider *p, CK_ULONG slotidx,
 		goto out;
 	}
  out:
-	for (i = 0; i < 3; i++)
+	for (i = 0; i < nattr; i++)
 		free(cert_attr[i].pValue);
 	X509_free(x509);
 	RSA_free(rsa);
@@ -1103,11 +1266,12 @@ note_key(struct pkcs11_provider *p, CK_ULONG slotidx, const char *context,
  */
 static int
 pkcs11_fetch_certs(struct pkcs11_provider *p, CK_ULONG slotidx,
-    struct sshkey ***keysp, char ***labelsp, int *nkeys)
+    struct sshkey ***keysp, char ***labelsp, int *nkeys, struct pkcs11_uri *uri)
 {
 	struct sshkey		*key = NULL;
 	CK_OBJECT_CLASS		 key_class;
-	CK_ATTRIBUTE		 key_attr[1];
+	CK_ATTRIBUTE		 key_attr[3];
+	int			 nattr = 1;
 	CK_SESSION_HANDLE	 session;
 	CK_FUNCTION_LIST	*f = NULL;
 	CK_RV			 rv;
@@ -1124,10 +1288,23 @@ pkcs11_fetch_certs(struct pkcs11_provider *p, CK_ULONG slotidx,
 	key_attr[0].pValue = &key_class;
 	key_attr[0].ulValueLen = sizeof(key_class);
 
-	session = p->slotinfo[slotidx].session;
-	f = p->function_list;
+	if (uri->id != NULL) {
+		key_attr[nattr].type = CKA_ID;
+		key_attr[nattr].pValue = uri->id;
+		key_attr[nattr].ulValueLen = uri->id_len;
+		nattr++;
+	}
+	if (uri->object != NULL) {
+		key_attr[nattr].type = CKA_LABEL;
+		key_attr[nattr].pValue = uri->object;
+		key_attr[nattr].ulValueLen = strlen(uri->object);
+		nattr++;
+	}
 
-	rv = f->C_FindObjectsInit(session, key_attr, 1);
+	session = p->module->slotinfo[slotidx].session;
+	f = p->module->function_list;
+
+	rv = f->C_FindObjectsInit(session, key_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_FindObjectsInit failed: %lu", rv);
 		goto fail;
@@ -1208,11 +1385,12 @@ fail:
  */
 static int
 pkcs11_fetch_keys(struct pkcs11_provider *p, CK_ULONG slotidx,
-    struct sshkey ***keysp, char ***labelsp, int *nkeys)
+    struct sshkey ***keysp, char ***labelsp, int *nkeys, struct pkcs11_uri *uri)
 {
 	struct sshkey		*key = NULL;
 	CK_OBJECT_CLASS		 key_class;
-	CK_ATTRIBUTE		 key_attr[2];
+	CK_ATTRIBUTE		 key_attr[3];
+	int			 nattr = 1;
 	CK_SESSION_HANDLE	 session;
 	CK_FUNCTION_LIST	*f = NULL;
 	CK_RV			 rv;
@@ -1228,10 +1406,23 @@ pkcs11_fetch_keys(struct pkcs11_provider *p, CK_ULONG slotidx,
 	key_attr[0].pValue = &key_class;
 	key_attr[0].ulValueLen = sizeof(key_class);
 
-	session = p->slotinfo[slotidx].session;
-	f = p->function_list;
+	if (uri->id != NULL) {
+		key_attr[nattr].type = CKA_ID;
+		key_attr[nattr].pValue = uri->id;
+		key_attr[nattr].ulValueLen = uri->id_len;
+		nattr++;
+	}
+	if (uri->object != NULL) {
+		key_attr[nattr].type = CKA_LABEL;
+		key_attr[nattr].pValue = uri->object;
+		key_attr[nattr].ulValueLen = strlen(uri->object);
+		nattr++;
+	}
 
-	rv = f->C_FindObjectsInit(session, key_attr, 1);
+	session = p->module->slotinfo[slotidx].session;
+	f = p->module->function_list;
+
+	rv = f->C_FindObjectsInit(session, key_attr, nattr);
 	if (rv != CKR_OK) {
 		error("C_FindObjectsInit failed: %lu", rv);
 		goto fail;
@@ -1500,16 +1691,10 @@ pkcs11_ecdsa_generate_private_key(struct pkcs11_provider *p, CK_ULONG slotidx,
 }
 #endif /* WITH_PKCS11_KEYGEN */
 
-/*
- * register a new provider, fails if provider already exists. if
- * keyp is provided, fetch keys.
- */
 static int
-pkcs11_register_provider(char *provider_id, char *pin,
-    struct sshkey ***keyp, char ***labelsp,
-    struct pkcs11_provider **providerp, CK_ULONG user)
+pkcs11_initialize_provider(struct pkcs11_uri *uri, struct pkcs11_provider **providerp)
 {
-	int nkeys, need_finalize = 0;
+	int need_finalize = 0;
 	int ret = -1;
 	struct pkcs11_provider *p = NULL;
 	void *handle = NULL;
@@ -1518,164 +1703,298 @@ pkcs11_register_provider(char *provider_id, char *pin,
 	CK_FUNCTION_LIST *f = NULL;
 	CK_TOKEN_INFO *token;
 	CK_ULONG i;
-
-	if (providerp == NULL)
+	char *provider_module = NULL;
+	struct pkcs11_module *m = NULL;
+
+	/* if no provider specified, fallback to p11-kit */
+	if (uri->module_path == NULL) {
+#ifdef PKCS11_DEFAULT_PROVIDER
+		provider_module = strdup(PKCS11_DEFAULT_PROVIDER);
+#else
+		error_f("No module path provided");
 		goto fail;
-	*providerp = NULL;
-
-	if (keyp != NULL)
-		*keyp = NULL;
-	if (labelsp != NULL)
-		*labelsp = NULL;
+#endif
+	} else {
+		provider_module = strdup(uri->module_path);
+	}
 
-	if (pkcs11_provider_lookup(provider_id) != NULL) {
-		debug_f("provider already registered: %s", provider_id);
-		goto fail;
+	p = xcalloc(1, sizeof(*p));
+	p->name = pkcs11_uri_get(uri);
+
+	if ((m = pkcs11_provider_lookup_module(provider_module)) != NULL
+	   && m->valid) {
+		debug_f("provider module already initialized: %s", provider_module);
+		free(provider_module);
+		/* Skip the initialization of PKCS#11 module */
+		m->refcount++;
+		p->module = m;
+		p->valid = 1;
+		TAILQ_INSERT_TAIL(&pkcs11_providers, p, next);
+		p->refcount++;	/* add to provider list */
+		*providerp = p;
+		return 0;
+	} else {
+		m = xcalloc(1, sizeof(*m));
+		p->module = m;
+		m->refcount++;
 	}
+
 	/* open shared pkcs11-library */
-	if ((handle = dlopen(provider_id, RTLD_NOW)) == NULL) {
-		error("dlopen %s failed: %s", provider_id, dlerror());
+	if ((handle = dlopen(provider_module, RTLD_NOW)) == NULL) {
+		error("dlopen %s failed: %s", provider_module, dlerror());
 		goto fail;
 	}
 	if ((getfunctionlist = dlsym(handle, "C_GetFunctionList")) == NULL) {
 		error("dlsym(C_GetFunctionList) failed: %s", dlerror());
 		goto fail;
 	}
-	p = xcalloc(1, sizeof(*p));
-	p->name = xstrdup(provider_id);
-	p->handle = handle;
+
+	p->module->handle = handle;
 	/* setup the pkcs11 callbacks */
 	if ((rv = (*getfunctionlist)(&f)) != CKR_OK) {
 		error("C_GetFunctionList for provider %s failed: %lu",
-		    provider_id, rv);
+		    provider_module, rv);
 		goto fail;
 	}
-	p->function_list = f;
+	m->function_list = f;
 	if ((rv = f->C_Initialize(NULL)) != CKR_OK) {
 		error("C_Initialize for provider %s failed: %lu",
-		    provider_id, rv);
+		    provider_module, rv);
 		goto fail;
 	}
 	need_finalize = 1;
-	if ((rv = f->C_GetInfo(&p->info)) != CKR_OK) {
+	if ((rv = f->C_GetInfo(&m->info)) != CKR_OK) {
 		error("C_GetInfo for provider %s failed: %lu",
-		    provider_id, rv);
+		    provider_module, rv);
+		goto fail;
+	}
+	rmspace(m->info.manufacturerID, sizeof(m->info.manufacturerID));
+	if (uri->lib_manuf != NULL &&
+	    strcmp(uri->lib_manuf, m->info.manufacturerID)) {
+		debug_f("Skipping provider %s not matching library_manufacturer",
+		    m->info.manufacturerID);
 		goto fail;
 	}
-	rmspace(p->info.manufacturerID, sizeof(p->info.manufacturerID));
-	rmspace(p->info.libraryDescription, sizeof(p->info.libraryDescription));
+	rmspace(m->info.libraryDescription, sizeof(m->info.libraryDescription));
 	debug("provider %s: manufacturerID <%s> cryptokiVersion %d.%d"
 	    " libraryDescription <%s> libraryVersion %d.%d",
-	    provider_id,
-	    p->info.manufacturerID,
-	    p->info.cryptokiVersion.major,
-	    p->info.cryptokiVersion.minor,
-	    p->info.libraryDescription,
-	    p->info.libraryVersion.major,
-	    p->info.libraryVersion.minor);
-	if ((rv = f->C_GetSlotList(CK_TRUE, NULL, &p->nslots)) != CKR_OK) {
+	    provider_module,
+	    m->info.manufacturerID,
+	    m->info.cryptokiVersion.major,
+	    m->info.cryptokiVersion.minor,
+	    m->info.libraryDescription,
+	    m->info.libraryVersion.major,
+	    m->info.libraryVersion.minor);
+
+	if ((rv = f->C_GetSlotList(CK_TRUE, NULL, &m->nslots)) != CKR_OK) {
 		error("C_GetSlotList failed: %lu", rv);
 		goto fail;
 	}
-	if (p->nslots == 0) {
-		debug_f("provider %s returned no slots", provider_id);
+	if (m->nslots == 0) {
+		debug_f("provider %s returned no slots", provider_module);
 		ret = -SSH_PKCS11_ERR_NO_SLOTS;
 		goto fail;
 	}
-	p->slotlist = xcalloc(p->nslots, sizeof(CK_SLOT_ID));
-	if ((rv = f->C_GetSlotList(CK_TRUE, p->slotlist, &p->nslots))
+	m->slotlist = xcalloc(m->nslots, sizeof(CK_SLOT_ID));
+	if ((rv = f->C_GetSlotList(CK_TRUE, m->slotlist, &m->nslots))
 	    != CKR_OK) {
 		error("C_GetSlotList for provider %s failed: %lu",
-		    provider_id, rv);
+		    provider_module, rv);
 		goto fail;
 	}
-	p->slotinfo = xcalloc(p->nslots, sizeof(struct pkcs11_slotinfo));
 	p->valid = 1;
-	nkeys = 0;
-	for (i = 0; i < p->nslots; i++) {
-		token = &p->slotinfo[i].token;
-		if ((rv = f->C_GetTokenInfo(p->slotlist[i], token))
+	m->slotinfo = xcalloc(m->nslots, sizeof(struct pkcs11_slotinfo));
+	m->valid = 1;
+	for (i = 0; i < m->nslots; i++) {
+		token = &m->slotinfo[i].token;
+		if ((rv = f->C_GetTokenInfo(m->slotlist[i], token))
 		    != CKR_OK) {
 			error("C_GetTokenInfo for provider %s slot %lu "
-			    "failed: %lu", provider_id, (u_long)i, rv);
-			continue;
-		}
-		if ((token->flags & CKF_TOKEN_INITIALIZED) == 0) {
-			debug2_f("ignoring uninitialised token in "
-			    "provider %s slot %lu", provider_id, (u_long)i);
+			    "failed: %lu", provider_module, (u_long)i, rv);
+			token->flags = 0;
 			continue;
 		}
 		rmspace(token->label, sizeof(token->label));
 		rmspace(token->manufacturerID, sizeof(token->manufacturerID));
 		rmspace(token->model, sizeof(token->model));
 		rmspace(token->serialNumber, sizeof(token->serialNumber));
+	}
+	m->module_path = provider_module;
+	provider_module = NULL;
+
+	/* insert unconditionally -- remove if there will be no keys later */
+	TAILQ_INSERT_TAIL(&pkcs11_providers, p, next);
+	p->refcount++;	/* add to provider list */
+	*providerp = p;
+	return 0;
+
+fail:
+	if (need_finalize && (rv = f->C_Finalize(NULL)) != CKR_OK)
+		error("C_Finalize for provider %s failed: %lu",
+		    provider_module, rv);
+	free(provider_module);
+	if (m) {
+		free(m->slotlist);
+		free(m);
+	}
+	if (p) {
+		free(p->name);
+		free(p);
+	}
+	if (handle)
+		dlclose(handle);
+	return ret;
+}
+
+/*
+ * register a new provider, fails if provider already exists. if
+ * keyp is provided, fetch keys.
+ */
+static int
+pkcs11_register_provider_by_uri(struct pkcs11_uri *uri, char *pin,
+    struct sshkey ***keyp, char ***labelsp, struct pkcs11_provider **providerp,
+    CK_ULONG user)
+{
+	int nkeys;
+	int ret = -1;
+	struct pkcs11_provider *p = NULL;
+	CK_ULONG i;
+	CK_TOKEN_INFO *token;
+	char *provider_uri = NULL;
+
+	if (providerp == NULL)
+		goto fail;
+	*providerp = NULL;
+
+	if (keyp != NULL)
+		*keyp = NULL;
+
+	if ((ret = pkcs11_initialize_provider(uri, &p)) != 0) {
+		goto fail;
+	}
+
+	provider_uri = pkcs11_uri_get(uri);
+	if (pin == NULL && uri->pin != NULL) {
+		pin = uri->pin;
+	}
+	nkeys = 0;
+	for (i = 0; i < p->module->nslots; i++) {
+		token = &p->module->slotinfo[i].token;
+		if ((token->flags & CKF_TOKEN_INITIALIZED) == 0) {
+			debug2_f("ignoring uninitialised token in "
+			    "provider %s slot %lu", provider_uri, (u_long)i);
+			continue;
+		}
+		if (uri->token != NULL &&
+		    strcmp(token->label, uri->token) != 0) {
+			debug2_f("ignoring token not matching label (%s) "
+			    "specified by PKCS#11 URI in slot %lu",
+			    token->label, (unsigned long)i);
+			continue;
+		}
+		if (uri->manuf != NULL &&
+		    strcmp(token->manufacturerID, uri->manuf) != 0) {
+			debug2_f("ignoring token not matching requrested "
+			    "manufacturerID (%s) specified by PKCS#11 URI in "
+			    "slot %lu", token->manufacturerID, (unsigned long)i);
+			continue;
+		}
 		debug("provider %s slot %lu: label <%s> manufacturerID <%s> "
 		    "model <%s> serial <%s> flags 0x%lx",
-		    provider_id, (unsigned long)i,
+		    provider_uri, (unsigned long)i,
 		    token->label, token->manufacturerID, token->model,
 		    token->serialNumber, token->flags);
 		/*
-		 * open session, login with pin and retrieve public
-		 * keys (if keyp is provided)
+		 * open session if not yet openend, login with pin and
+		 * retrieve public keys (if keyp is provided)
 		 */
-		if ((ret = pkcs11_open_session(p, i, pin, user)) != 0 ||
+		if ((p->module->slotinfo[i].session != 0 ||
+		    (ret = pkcs11_open_session(p, i, pin, user)) != 0) && /* ??? */
 		    keyp == NULL)
 			continue;
-		pkcs11_fetch_keys(p, i, keyp, labelsp, &nkeys);
-		pkcs11_fetch_certs(p, i, keyp, labelsp, &nkeys);
-		if (nkeys == 0 && !p->slotinfo[i].logged_in &&
+		pkcs11_fetch_keys(p, i, keyp, labelsp, &nkeys, uri);
+		pkcs11_fetch_certs(p, i, keyp, labelsp, &nkeys, uri);
+		if (nkeys == 0 && !p->module->slotinfo[i].logged_in &&
 		    pkcs11_interactive) {
 			/*
 			 * Some tokens require login before they will
 			 * expose keys.
 			 */
-			if (pkcs11_login_slot(p, &p->slotinfo[i],
+			debug3_f("Trying to login as there were no keys found");
+			if (pkcs11_login_slot(p, &p->module->slotinfo[i],
 			    CKU_USER) < 0) {
 				error("login failed");
 				continue;
 			}
-			pkcs11_fetch_keys(p, i, keyp, labelsp, &nkeys);
-			pkcs11_fetch_certs(p, i, keyp, labelsp, &nkeys);
+			pkcs11_fetch_keys(p, i, keyp, labelsp, &nkeys, uri);
+			pkcs11_fetch_certs(p, i, keyp, labelsp, &nkeys, uri);
+		}
+		if (nkeys == 0 && uri->object != NULL) {
+			debug3_f("No keys found. Retrying without label (%s) ",
+			    uri->object);
+			/* Try once more without the label filter */
+			char *label = uri->object;
+			uri->object = NULL; /* XXX clone uri? */
+			pkcs11_fetch_keys(p, i, keyp, labelsp, &nkeys, uri);
+			pkcs11_fetch_certs(p, i, keyp, labelsp, &nkeys, uri);
+			uri->object = label;
 		}
 	}
+	pin = NULL; /* Will be cleaned up with URI */
 
 	/* now owned by caller */
 	*providerp = p;
 
-	TAILQ_INSERT_TAIL(&pkcs11_providers, p, next);
-	p->refcount++;	/* add to provider list */
-
+	free(provider_uri);
 	return (nkeys);
 fail:
-	if (need_finalize && (rv = f->C_Finalize(NULL)) != CKR_OK)
-		error("C_Finalize for provider %s failed: %lu",
-		    provider_id, rv);
 	if (p) {
-		free(p->name);
-		free(p->slotlist);
-		free(p->slotinfo);
-		free(p);
+ 		TAILQ_REMOVE(&pkcs11_providers, p, next);
+		pkcs11_provider_unref(p);
 	}
-	if (handle)
-		dlclose(handle);
 	if (ret > 0)
 		ret = -1;
 	return (ret);
 }
 
-/*
- * register a new provider and get number of keys hold by the token,
- * fails if provider already exists
- */
+static int
+pkcs11_register_provider(char *provider_id, char *pin, struct sshkey ***keyp,
+    char ***labelsp, struct pkcs11_provider **providerp, CK_ULONG user)
+{
+	struct pkcs11_uri *uri = NULL;
+	int r;
+
+	debug_f("called, provider_id = %s", provider_id);
+
+	uri = pkcs11_uri_init();
+	if (uri == NULL)
+		fatal("failed to init PKCS#11 URI");
+
+	if (strlen(provider_id) >= strlen(PKCS11_URI_SCHEME) &&
+	    strncmp(provider_id, PKCS11_URI_SCHEME, strlen(PKCS11_URI_SCHEME)) == 0) {
+		if (pkcs11_uri_parse(provider_id, uri) != 0)
+			fatal("Failed to parse PKCS#11 URI");
+	} else {
+		uri->module_path = strdup(provider_id);
+	}
+
+	r = pkcs11_register_provider_by_uri(uri, pin, keyp, labelsp, providerp, user);
+	pkcs11_uri_cleanup(uri);
+
+	return r;
+}
+
 int
-pkcs11_add_provider(char *provider_id, char *pin, struct sshkey ***keyp,
-    char ***labelsp)
+pkcs11_add_provider_by_uri(struct pkcs11_uri *uri, char *pin,
+    struct sshkey ***keyp, char ***labelsp)
 {
 	struct pkcs11_provider *p = NULL;
 	int nkeys;
+	char *provider_uri = pkcs11_uri_get(uri);
 
-	nkeys = pkcs11_register_provider(provider_id, pin, keyp, labelsp,
-	    &p, CKU_USER);
+	debug_f("called, provider_uri = %s", provider_uri);
+
+	nkeys = pkcs11_register_provider_by_uri(uri, pin, keyp, labelsp, &p, CKU_USER);
 
 	/* no keys found or some other error, de-register provider */
 	if (nkeys <= 0 && p != NULL) {
@@ -1684,7 +2003,37 @@ pkcs11_add_provider(char *provider_id, char *pin, struct sshkey ***keyp,
 		pkcs11_provider_unref(p);
 	}
 	if (nkeys == 0)
-		debug_f("provider %s returned no keys", provider_id);
+		debug_f("provider %s returned no keys", provider_uri);
+
+	free(provider_uri);
+	return nkeys;
+}
+
+/*
+ * register a new provider and get number of keys hold by the token,
+ * fails if provider already exists
+ */
+int
+pkcs11_add_provider(char *provider_id, char *pin,
+    struct sshkey ***keyp, char ***labelsp)
+{
+	struct pkcs11_uri *uri;
+	int nkeys;
+
+	uri = pkcs11_uri_init();
+	if (uri == NULL)
+		fatal("Failed to init PKCS#11 URI");
+
+	if (strlen(provider_id) >= strlen(PKCS11_URI_SCHEME) &&
+	    strncmp(provider_id, PKCS11_URI_SCHEME, strlen(PKCS11_URI_SCHEME)) == 0) {
+		if (pkcs11_uri_parse(provider_id, uri) != 0)
+			fatal("Failed to parse PKCS#11 URI");
+	} else {
+		uri->module_path = strdup(provider_id);
+	}
+
+	nkeys = pkcs11_add_provider_by_uri(uri, pin, keyp, labelsp);
+	pkcs11_uri_cleanup(uri);
 
 	return (nkeys);
 }
diff --git a/ssh-pkcs11.h b/ssh-pkcs11.h
index 81f1d7c..feaf74d 100644
--- a/ssh-pkcs11.h
+++ b/ssh-pkcs11.h
@@ -22,10 +22,14 @@
 #define	SSH_PKCS11_ERR_PIN_REQUIRED		4
 #define	SSH_PKCS11_ERR_PIN_LOCKED		5
 
+#include "ssh-pkcs11-uri.h"
+
 int	pkcs11_init(int);
 void	pkcs11_terminate(void);
 int	pkcs11_add_provider(char *, char *, struct sshkey ***, char ***);
+int	pkcs11_add_provider_by_uri(struct pkcs11_uri *, char *, struct sshkey ***, char ***);
 int	pkcs11_del_provider(char *);
+int	pkcs11_uri_write(const struct sshkey *, FILE *);
 #ifdef WITH_PKCS11_KEYGEN
 struct sshkey *
 	pkcs11_gakp(char *, char *, unsigned int, char *, unsigned int,
diff --git a/ssh.c b/ssh.c
index 244b7f3..fff421a 100644
--- a/ssh.c
+++ b/ssh.c
@@ -835,6 +835,14 @@ main(int ac, char **av)
 			options.gss_deleg_creds = 1;
 			break;
 		case 'i':
+#ifdef ENABLE_PKCS11
+			if (strlen(optarg) >= strlen(PKCS11_URI_SCHEME) &&
+			    strncmp(optarg, PKCS11_URI_SCHEME,
+			    strlen(PKCS11_URI_SCHEME)) == 0) {
+				add_identity_file(&options, NULL, optarg, 1);
+				break;
+			}
+#endif
 			p = tilde_expand_filename(optarg, getuid());
 			if (stat(p, &st) == -1)
 				fprintf(stderr, "Warning: Identity file %s "
@@ -1699,6 +1707,7 @@ main(int ac, char **av)
 #ifdef ENABLE_PKCS11
 	(void)pkcs11_del_provider(options.pkcs11_provider);
 #endif
+	pkcs11_terminate();
 
  skip_connect:
 	exit_status = ssh_session2(ssh, cinfo);
@@ -2215,6 +2224,45 @@ ssh_session2(struct ssh *ssh, const struct ssh_conn_info *cinfo)
 	    options.escape_char : SSH_ESCAPECHAR_NONE, id);
 }
 
+#ifdef ENABLE_PKCS11
+static void
+load_pkcs11_identity(char *pkcs11_uri, char *identity_files[],
+    struct sshkey *identity_keys[], int *n_ids)
+{
+	int nkeys, i;
+	struct sshkey **keys;
+	struct pkcs11_uri *uri;
+
+	debug("identity file '%s' from pkcs#11", pkcs11_uri);
+	uri = pkcs11_uri_init();
+	if (uri == NULL)
+		fatal("Failed to init PKCS#11 URI");
+
+	if (pkcs11_uri_parse(pkcs11_uri, uri) != 0)
+	fatal("Failed to parse PKCS#11 URI %s", pkcs11_uri);
+
+	/* we need to merge URI and provider together */
+	if (options.pkcs11_provider != NULL && uri->module_path == NULL)
+		uri->module_path = strdup(options.pkcs11_provider);
+
+	if (options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
+	    (nkeys = pkcs11_add_provider_by_uri(uri, NULL, &keys, NULL)) > 0) {
+		for (i = 0; i < nkeys; i++) {
+			if (*n_ids >= SSH_MAX_IDENTITY_FILES) {
+				sshkey_free(keys[i]);
+				continue;
+			}
+			identity_keys[*n_ids] = keys[i];
+			identity_files[*n_ids] = pkcs11_uri_get(uri);
+			(*n_ids)++;
+		}
+		free(keys);
+	}
+
+	pkcs11_uri_cleanup(uri);
+}
+#endif /* ENABLE_PKCS11 */
+
 /* Loads all IdentityFile and CertificateFile keys */
 static void
 load_public_identity_files(const struct ssh_conn_info *cinfo)
@@ -2229,11 +2277,6 @@ load_public_identity_files(const struct ssh_conn_info *cinfo)
 	char *certificate_files[SSH_MAX_CERTIFICATE_FILES];
 	struct sshkey *certificates[SSH_MAX_CERTIFICATE_FILES];
 	int certificate_file_userprovided[SSH_MAX_CERTIFICATE_FILES];
-#ifdef ENABLE_PKCS11
-	struct sshkey **keys = NULL;
-	char **comments = NULL;
-	int nkeys;
-#endif /* PKCS11 */
 
 	n_ids = n_certs = 0;
 	memset(identity_files, 0, sizeof(identity_files));
@@ -2246,33 +2289,46 @@ load_public_identity_files(const struct ssh_conn_info *cinfo)
 	    sizeof(certificate_file_userprovided));
 
 #ifdef ENABLE_PKCS11
-	if (options.pkcs11_provider != NULL &&
-	    options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
-	    (pkcs11_init(!options.batch_mode) == 0) &&
-	    (nkeys = pkcs11_add_provider(options.pkcs11_provider, NULL,
-	    &keys, &comments)) > 0) {
-		for (i = 0; i < nkeys; i++) {
-			if (n_ids >= SSH_MAX_IDENTITY_FILES) {
-				sshkey_free(keys[i]);
-				free(comments[i]);
-				continue;
-			}
-			identity_keys[n_ids] = keys[i];
-			identity_files[n_ids] = comments[i]; /* transferred */
-			n_ids++;
-		}
-		free(keys);
-		free(comments);
+	/* handle fallback from PKCS11Provider option */
+	pkcs11_init(!options.batch_mode);
+
+	if (options.pkcs11_provider != NULL) {
+		struct pkcs11_uri *uri;
+
+		uri = pkcs11_uri_init();
+		if (uri == NULL)
+			fatal("Failed to init PKCS#11 URI");
+
+		/* Construct simple PKCS#11 URI to simplify access */
+		uri->module_path = strdup(options.pkcs11_provider);
+
+		/* Add it as any other IdentityFile */
+		cp = pkcs11_uri_get(uri);
+		add_identity_file(&options, NULL, cp, 1);
+		free(cp);
+
+		pkcs11_uri_cleanup(uri);
 	}
 #endif /* ENABLE_PKCS11 */
 	for (i = 0; i < options.num_identity_files; i++) {
+		char *name = options.identity_files[i];
 		if (n_ids >= SSH_MAX_IDENTITY_FILES ||
-		    strcasecmp(options.identity_files[i], "none") == 0) {
+		    strcasecmp(name, "none") == 0) {
 			free(options.identity_files[i]);
 			options.identity_files[i] = NULL;
 			continue;
 		}
-		cp = tilde_expand_filename(options.identity_files[i], getuid());
+#ifdef ENABLE_PKCS11
+		if (strlen(name) >= strlen(PKCS11_URI_SCHEME) &&
+		    strncmp(name, PKCS11_URI_SCHEME,
+		    strlen(PKCS11_URI_SCHEME)) == 0) {
+			load_pkcs11_identity(name, identity_files,
+			    identity_keys, &n_ids);
+			free(options.identity_files[i]);
+			continue;
+		}
+#endif /* ENABLE_PKCS11 */
+		cp = tilde_expand_filename(name, getuid());
 		filename = default_client_percent_dollar_expand(cp, cinfo);
 		free(cp);
 		check_load(sshkey_load_public(filename, &public, NULL),
diff --git a/ssh_config.5 b/ssh_config.5
index 0a6c4a6..4bacaf9 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -1114,6 +1114,21 @@ may also be used in conjunction with
 .Cm CertificateFile
 in order to provide any certificate also needed for authentication with
 the identity.
+.Pp
+The authentication identity can be also specified in a form of PKCS#11 URI
+starting with a string
+.Cm pkcs11: .
+There is supported a subset of the PKCS#11 URI as defined
+in RFC 7512 (implemented path arguments
+.Cm id ,
+.Cm manufacturer ,
+.Cm object ,
+.Cm token
+and query arguments
+.Cm module-path
+and
+.Cm pin-value
+). The URI can not be in quotes.
 .It Cm IgnoreUnknown
 Specifies a pattern-list of unknown options to be ignored if they are
 encountered in configuration parsing.
-- 
2.27.0

