From 0a66ad22e54c72690ec2a29a019767c55c5281fc Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@ozlabs.org>
Date: Fri, 18 Oct 2024 20:22:57 +1100
Subject: [PATCH] pppd: Remove passprompt plugin

This is prompted by a number of factors:

* It was more useful back in the dial-up days, but no-one uses dial-up
  any more

* In many cases there will be no terminal accessible to the prompter
  program at the point where the prompter is run

* The passwordfd plugin does much the same thing but does it more
  cleanly and securely

* The handling of privileges and file descriptors needs to be audited
  thoroughly.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
---
 pppd/plugins/Makefile.am  |   6 +-
 pppd/plugins/passprompt.c | 137 --------------------------------------
 2 files changed, 1 insertion(+), 142 deletions(-)
 delete mode 100644 pppd/plugins/passprompt.c

diff --git a/pppd/plugins/Makefile.am b/pppd/plugins/Makefile.am
index 2826148c7..9480d51b4 100644
--- a/pppd/plugins/Makefile.am
+++ b/pppd/plugins/Makefile.am
@@ -1,4 +1,4 @@
-pppd_plugin_LTLIBRARIES = minconn.la passprompt.la passwordfd.la winbind.la
+pppd_plugin_LTLIBRARIES = minconn.la passwordfd.la winbind.la
 pppd_plugindir = $(PPPD_PLUGIN_DIR)
 
 PLUGIN_CPPFLAGS = -I${top_srcdir}
@@ -8,10 +8,6 @@ minconn_la_CPPFLAGS = $(PLUGIN_CPPFLAGS)
 minconn_la_LDFLAGS = $(PLUGIN_LDFLAGS)
 minconn_la_SOURCES = minconn.c
 
-passprompt_la_CPPFLAGS = $(PLUGIN_CPPFLAGS)
-passprompt_la_LDFLAGS = $(PLUGIN_LDFLAGS)
-passprompt_la_SOURCES = passprompt.c
-
 passwordfd_la_CPPFLAGS = $(PLUGIN_CPPFLAGS)
 passwordfd_la_LDFLAGS = $(PLUGIN_LDFLAGS)
 passwordfd_la_SOURCES = passwordfd.c
diff --git a/pppd/plugins/passprompt.c b/pppd/plugins/passprompt.c
deleted file mode 100644
index 7779d511d..000000000
--- a/pppd/plugins/passprompt.c
+++ /dev/null
@@ -1,137 +0,0 @@
-/*
- * passprompt.c - pppd plugin to invoke an external PAP password prompter
- *
- * Copyright 1999 Paul Mackerras, Alan Curry.
- *
- *  This program is free software; you can redistribute it and/or
- *  modify it under the terms of the GNU General Public License
- *  as published by the Free Software Foundation; either version
- *  2 of the License, or (at your option) any later version.
- */
-
-#include <errno.h>
-#include <unistd.h>
-#include <sys/wait.h>
-#include <sys/param.h>
-#include <limits.h>
-#include <stdio.h>
-#include <syslog.h>
-#include <stdarg.h>
-#include <stdint.h>
-#include <stdbool.h>
-#include <string.h>
-
-#include <pppd/pppd.h>
-#include <pppd/upap.h>
-#include <pppd/eap.h>
-#include <pppd/options.h>
-
-char pppd_version[] = PPPD_VERSION;
-
-static char promptprog[PATH_MAX+1];
-static int promptprog_refused = 0;
-
-static struct option options[] = {
-    { "promptprog", o_string, promptprog,
-      "External PAP password prompting program",
-      OPT_STATIC, NULL, PATH_MAX },
-    { NULL }
-};
-
-static int promptpass(char *user, char *passwd)
-{
-    int p[2];
-    pid_t kid;
-    int readgood, wstat, ret;
-    ssize_t red;
-
-    if (promptprog_refused || promptprog[0] == 0 || access(promptprog, X_OK) < 0)
-	return -1;	/* sorry, can't help */
-
-    if (!passwd)
-	return 1;
-
-    if (pipe(p)) {
-	warn("Can't make a pipe for %s", promptprog);
-	return 0;
-    }
-    if ((kid = fork()) == (pid_t) -1) {
-	warn("Can't fork to run %s", promptprog);
-	close(p[0]);
-	close(p[1]);
-	return 0;
-    }
-    if (!kid) {
-	/* we are the child, exec the program */
-	char *argv[5], fdstr[32];
-	ppp_sys_close();
-	closelog();
-	close(p[0]);
-	ret = seteuid(getuid());
-	if (ret != 0) {
-		warn("Couldn't set effective user id");
-	}
-	ret = setegid(getgid());
-	if (ret != 0) {
-		warn("Couldn't set effective user id");
-	}
-	sprintf(fdstr, "%d", p[1]);
-	argv[0] = promptprog;
-	argv[1] = strdup(user);
-	argv[2] = strdup(ppp_remote_name());
-	argv[3] = fdstr;
-	argv[4] = 0;
-	execv(*argv, argv);
-	_exit(127);
-    }
-
-    /* we are the parent, read the password from the pipe */
-    close(p[1]);
-    readgood = 0;
-    do {
-	red = read(p[0], passwd + readgood, MAXSECRETLEN-1 - readgood);
-	if (red == 0)
-	    break;
-	if (red < 0) {
-	    if (errno == EINTR && !ppp_signaled(SIGTERM))
-		continue;
-	    error("Can't read secret from %s: %m", promptprog);
-	    readgood = -1;
-	    break;
-	}
-	readgood += red;
-    } while (readgood < MAXSECRETLEN - 1);
-    close(p[0]);
-
-    /* now wait for child to exit */
-    while (waitpid(kid, &wstat, 0) < 0) {
-	if (errno != EINTR || ppp_signaled(SIGTERM)) {
-	    warn("error waiting for %s: %m", promptprog);
-	    break;
-	}
-    }
-
-    if (readgood < 0)
-	return 0;
-    passwd[readgood] = 0;
-    if (!WIFEXITED(wstat))
-	warn("%s terminated abnormally", promptprog);
-    if (WEXITSTATUS(wstat)) {
-	    warn("%s exited with code %d", promptprog, WEXITSTATUS(wstat));
-	    /* code when cancel was hit in the prompt prog */
-	    if (WEXITSTATUS(wstat) == 128) {
-	        promptprog_refused = 1;
-	    }
-	    return -1;
-    }
-    return 1;
-}
-
-void plugin_init(void)
-{
-    ppp_add_options(options);
-    pap_passwd_hook = promptpass;
-#ifdef PPP_WITH_EAPTLS
-    eaptls_passwd_hook = promptpass;
-#endif
-}
