krb5/downstream-ksu-pam-integration.patch

From 90ba715be48c2e1b6c7ca53cb1d75f3af2c388d6 Mon Sep 17 00:00:00 2001
From: Robbie Harwood <rharwood@redhat.com>
Date: Tue, 23 Aug 2016 16:29:58 -0400
Subject: [PATCH] [downstream] ksu pam integration

Modify ksu so that it performs account and session management on behalf of
the target user account, mimicking the action of regular su.  The default
service name is "ksu", because on Fedora at least the configuration used
is determined by whether or not a login shell is being opened, and so
this may need to vary, too.  At run-time, ksu's behavior can be reset to
the earlier, non-PAM behavior by setting "use_pam" to false in the [ksu]
section of /etc/krb5.conf.

When enabled, ksu gains a dependency on libpam.

Originally RT#5939, though it's changed since then to perform the account
and session management before dropping privileges, and to apply on top of
changes we're proposing for how it handles cache collections.

Last-updated: krb5-1.18-beta1
---
 src/aclocal.m4              |  69 +++++++
 src/clients/ksu/Makefile.in |   8 +-
 src/clients/ksu/main.c      |  88 +++++++-
 src/clients/ksu/pam.c       | 389 ++++++++++++++++++++++++++++++++++++
 src/clients/ksu/pam.h       |  57 ++++++
 src/configure.ac            |   2 +
 6 files changed, 610 insertions(+), 3 deletions(-)
 create mode 100644 src/clients/ksu/pam.c
 create mode 100644 src/clients/ksu/pam.h

diff --git a/src/aclocal.m4 b/src/aclocal.m4
index 024d6370c..ca9fcf664 100644
--- a/src/aclocal.m4
+++ b/src/aclocal.m4
@@ -1677,3 +1677,72 @@ if test "$with_ldap" = yes; then
   OPENLDAP_PLUGIN=yes
 fi
 ])dnl
+dnl
+dnl
+dnl Use PAM instead of local crypt() compare for checking local passwords,
+dnl and perform PAM account, session management, and password-changing where
+dnl appropriate.
+dnl 
+AC_DEFUN(KRB5_WITH_PAM,[
+AC_ARG_WITH(pam,[AC_HELP_STRING(--with-pam,[compile with PAM support])],
+	    withpam="$withval",withpam=auto)
+AC_ARG_WITH(pam-ksu-service,[AC_HELP_STRING(--with-ksu-service,[PAM service name for ksu ["ksu"]])],
+	    withksupamservice="$withval",withksupamservice=ksu)
+old_LIBS="$LIBS"
+if test "$withpam" != no ; then
+	AC_MSG_RESULT([checking for PAM...])
+	PAM_LIBS=
+
+	AC_CHECK_HEADERS(security/pam_appl.h)
+	if test "x$ac_cv_header_security_pam_appl_h" != xyes ; then
+		if test "$withpam" = auto ; then
+			AC_MSG_RESULT([Unable to locate security/pam_appl.h.])
+			withpam=no
+		else
+			AC_MSG_ERROR([Unable to locate security/pam_appl.h.])
+		fi
+	fi
+
+	LIBS=
+	unset ac_cv_func_pam_start
+	AC_CHECK_FUNCS(putenv pam_start)
+	if test "x$ac_cv_func_pam_start" = xno ; then
+		unset ac_cv_func_pam_start
+		AC_CHECK_LIB(dl,dlopen)
+		AC_CHECK_FUNCS(pam_start)
+		if test "x$ac_cv_func_pam_start" = xno ; then
+			AC_CHECK_LIB(pam,pam_start)
+			unset ac_cv_func_pam_start
+			unset ac_cv_func_pam_getenvlist
+			AC_CHECK_FUNCS(pam_start pam_getenvlist)
+			if test "x$ac_cv_func_pam_start" = xyes ; then
+				PAM_LIBS="$LIBS"
+			else
+				if test "$withpam" = auto ; then
+					AC_MSG_RESULT([Unable to locate libpam.])
+					withpam=no
+				else
+					AC_MSG_ERROR([Unable to locate libpam.])
+				fi
+			fi
+		fi
+	fi
+	if test "$withpam" != no ; then
+		AC_MSG_NOTICE([building with PAM support])
+		AC_DEFINE(USE_PAM,1,[Define if Kerberos-aware tools should support PAM])
+		AC_DEFINE_UNQUOTED(KSU_PAM_SERVICE,"$withksupamservice",
+				   [Define to the name of the PAM service name to be used by ksu.])
+		PAM_LIBS="$LIBS"
+		NON_PAM_MAN=".\\\" "
+		PAM_MAN=
+	else
+		PAM_MAN=".\\\" "
+		NON_PAM_MAN=
+	fi
+fi
+LIBS="$old_LIBS"
+AC_SUBST(PAM_LIBS)
+AC_SUBST(PAM_MAN)
+AC_SUBST(NON_PAM_MAN)
+])dnl
+
diff --git a/src/clients/ksu/Makefile.in b/src/clients/ksu/Makefile.in
index 8b4edce4d..9d58f29b5 100644
--- a/src/clients/ksu/Makefile.in
+++ b/src/clients/ksu/Makefile.in
@@ -3,12 +3,14 @@ BUILDTOP=$(REL)..$(S)..
 DEFINES = -DGET_TGT_VIA_PASSWD -DPRINC_LOOK_AHEAD -DCMD_PATH='"/usr/local/sbin /usr/local/bin /sbin /bin /usr/sbin /usr/bin"'
 
 KSU_LIBS=@KSU_LIBS@
+PAM_LIBS=@PAM_LIBS@
 
 SRCS = \
 	$(srcdir)/krb_auth_su.c \
 	$(srcdir)/ccache.c \
 	$(srcdir)/authorization.c \
 	$(srcdir)/main.c \
+	$(srcdir)/pam.c \
 	$(srcdir)/heuristic.c \
 	$(srcdir)/xmalloc.c \
 	$(srcdir)/setenv.c
@@ -17,13 +19,17 @@ OBJS = \
 	ccache.o \
 	authorization.o \
 	main.o \
+	pam.o \
 	heuristic.o \
 	xmalloc.o @SETENVOBJ@
 
 all: ksu
 
 ksu: $(OBJS) $(KRB5_BASE_DEPLIBS)
-	$(CC_LINK) -o $@ $(OBJS) $(KRB5_BASE_LIBS) $(KSU_LIBS)
+	$(CC_LINK) -o $@ $(OBJS) $(KRB5_BASE_LIBS) $(KSU_LIBS) $(PAM_LIBS)
+
+pam.o: pam.c
+	$(CC) $(ALL_CFLAGS) -c $<
 
 clean:
 	$(RM) ksu
diff --git a/src/clients/ksu/main.c b/src/clients/ksu/main.c
index af1286172..931f05404 100644
--- a/src/clients/ksu/main.c
+++ b/src/clients/ksu/main.c
@@ -26,6 +26,7 @@
  * KSU was written by:  Ari Medvinsky, ari@isi.edu
  */
 
+#include "autoconf.h"
 #include "ksu.h"
 #include "adm_proto.h"
 #include <sys/types.h>
@@ -33,6 +34,10 @@
 #include <signal.h>
 #include <grp.h>
 
+#ifdef USE_PAM
+#include "pam.h"
+#endif
+
 /* globals */
 char * prog_name;
 int auth_debug =0;
@@ -40,6 +45,7 @@ char k5login_path[MAXPATHLEN];
 char k5users_path[MAXPATHLEN];
 char * gb_err = NULL;
 int quiet = 0;
+int force_fork = 0;
 /***********/
 
 #define KS_TEMPORARY_CACHE "MEMORY:_ksu"
@@ -536,6 +542,23 @@ main (argc, argv)
                prog_name,target_user,client_name,
                source_user,ontty());
 
+#ifdef USE_PAM
+        if (appl_pam_enabled(ksu_context, "ksu")) {
+            if (appl_pam_acct_mgmt(KSU_PAM_SERVICE, 1, target_user, NULL,
+                                   NULL, source_user,
+                                   ttyname(STDERR_FILENO)) != 0) {
+                fprintf(stderr, "Access denied for %s.\n", target_user);
+                exit(1);
+            }
+            if (appl_pam_requires_chauthtok()) {
+                fprintf(stderr, "Password change required for %s.\n",
+                        target_user);
+                exit(1);
+            }
+            force_fork++;
+        }
+#endif
+
         /* Run authorization as target.*/
         if (krb5_seteuid(target_uid)) {
             com_err(prog_name, errno, _("while switching to target for "
@@ -596,6 +619,24 @@ main (argc, argv)
 
             exit(1);
         }
+#ifdef USE_PAM
+    } else {
+        /* we always do PAM account management, even for root */
+        if (appl_pam_enabled(ksu_context, "ksu")) {
+            if (appl_pam_acct_mgmt(KSU_PAM_SERVICE, 1, target_user, NULL,
+                                   NULL, source_user,
+                                   ttyname(STDERR_FILENO)) != 0) {
+                fprintf(stderr, "Access denied for %s.\n", target_user);
+                exit(1);
+            }
+            if (appl_pam_requires_chauthtok()) {
+                fprintf(stderr, "Password change required for %s.\n",
+                        target_user);
+                exit(1);
+            }
+            force_fork++;
+        }
+#endif
     }
 
     if( some_rest_copy){
@@ -653,6 +694,30 @@ main (argc, argv)
         exit(1);
     }
 
+#ifdef USE_PAM
+    if (appl_pam_enabled(ksu_context, "ksu")) {
+        if (appl_pam_session_open() != 0) {
+            fprintf(stderr, "Error opening session for %s.\n", target_user);
+            exit(1);
+        }
+#ifdef DEBUG
+        if (auth_debug){
+            printf(" Opened PAM session.\n");
+        }
+#endif
+        if (appl_pam_cred_init()) {
+            fprintf(stderr, "Error initializing credentials for %s.\n",
+                    target_user);
+            exit(1);
+        }
+#ifdef DEBUG
+        if (auth_debug){
+            printf(" Initialized PAM credentials.\n");
+        }
+#endif
+    }
+#endif
+
     /* set permissions */
     if (setgid(target_pwd->pw_gid) < 0) {
         perror("ksu: setgid");
@@ -750,7 +815,7 @@ main (argc, argv)
         fprintf(stderr, "program to be execed %s\n",params[0]);
     }
 
-    if( keep_target_cache ) {
+    if( keep_target_cache && !force_fork ) {
         execv(params[0], params);
         com_err(prog_name, errno, _("while trying to execv %s"), params[0]);
         sweep_up(ksu_context, cc_target);
@@ -780,16 +845,35 @@ main (argc, argv)
             if (ret_pid == -1) {
                 com_err(prog_name, errno, _("while calling waitpid"));
             }
-            sweep_up(ksu_context, cc_target);
+            if( !keep_target_cache ) {
+                sweep_up(ksu_context, cc_target);
+            }
             exit (statusp);
         case -1:
             com_err(prog_name, errno, _("while trying to fork."));
             sweep_up(ksu_context, cc_target);
             exit (1);
         case 0:
+#ifdef USE_PAM
+            if (appl_pam_enabled(ksu_context, "ksu")) {
+                if (appl_pam_setenv() != 0) {
+                    fprintf(stderr, "Error setting up environment for %s.\n",
+                            target_user);
+                    exit (1);
+                }
+#ifdef DEBUG
+                if (auth_debug){
+                    printf(" Set up PAM environment.\n");
+                }
+#endif
+            }
+#endif
             execv(params[0], params);
             com_err(prog_name, errno, _("while trying to execv %s"),
                     params[0]);
+            if( keep_target_cache ) {
+                sweep_up(ksu_context, cc_target);
+            }
             exit (1);
         }
     }
diff --git a/src/clients/ksu/pam.c b/src/clients/ksu/pam.c
new file mode 100644
index 000000000..cbfe48704
--- /dev/null
+++ b/src/clients/ksu/pam.c
@@ -0,0 +1,389 @@
+/*
+ * src/clients/ksu/pam.c
+ *
+ * Copyright 2007,2009,2010 Red Hat, Inc.
+ *
+ * All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  Redistributions of source code must retain the above copyright notice, this
+ *  list of conditions and the following disclaimer.
+ *
+ *  Redistributions in binary form must reproduce the above copyright notice,
+ *  this list of conditions and the following disclaimer in the documentation
+ *  and/or other materials provided with the distribution.
+ *
+ *  Neither the name of Red Hat, Inc. nor the names of its contributors may be
+ *  used to endorse or promote products derived from this software without
+ *  specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * 
+ * Convenience wrappers for using PAM.
+ */
+
+#include "autoconf.h"
+#ifdef USE_PAM
+#include <sys/types.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include "k5-int.h"
+#include "pam.h"
+
+#ifndef MAXPWSIZE
+#define MAXPWSIZE 128
+#endif
+
+static int appl_pam_started;
+static pid_t appl_pam_starter = -1;
+static int appl_pam_session_opened;
+static int appl_pam_creds_initialized;
+static int appl_pam_pwchange_required;
+static pam_handle_t *appl_pamh;
+static struct pam_conv appl_pam_conv;
+static char *appl_pam_user;
+struct appl_pam_non_interactive_args {
+	const char *user;
+	const char *password;
+};
+
+int
+appl_pam_enabled(krb5_context context, const char *section)
+{
+	int enabled = 1;
+	if ((context != NULL) && (context->profile != NULL)) {
+		if (profile_get_boolean(context->profile,
+					section,
+					USE_PAM_CONFIGURATION_KEYWORD,
+					NULL,
+					enabled, &enabled) != 0) {
+			enabled = 1;
+		}
+	}
+	return enabled;
+}
+
+void
+appl_pam_cleanup(void)
+{
+	if (getpid() != appl_pam_starter) {
+		return;
+	}
+#ifdef DEBUG
+	printf("Called to clean up PAM.\n");
+#endif
+	if (appl_pam_creds_initialized) {
+#ifdef DEBUG
+		printf("Deleting PAM credentials.\n");
+#endif
+		pam_setcred(appl_pamh, PAM_DELETE_CRED);
+		appl_pam_creds_initialized = 0;
+	}
+	if (appl_pam_session_opened) {
+#ifdef DEBUG
+		printf("Closing PAM session.\n");
+#endif
+		pam_close_session(appl_pamh, 0);
+		appl_pam_session_opened = 0;
+	}
+	appl_pam_pwchange_required = 0;
+	if (appl_pam_started) {
+#ifdef DEBUG
+		printf("Shutting down PAM.\n");
+#endif
+		pam_end(appl_pamh, 0);
+		appl_pam_started = 0;
+		appl_pam_starter = -1;
+		free(appl_pam_user);
+		appl_pam_user = NULL;
+	}
+}
+static int
+appl_pam_interactive_converse(int num_msg, const struct pam_message **msg,
+			      struct pam_response **presp, void *appdata_ptr)
+{
+	const struct pam_message *message;
+	struct pam_response *resp;
+	int i, code;
+	char *pwstring, pwbuf[MAXPWSIZE];
+	unsigned int pwsize;
+	resp = malloc(sizeof(struct pam_response) * num_msg);
+	if (resp == NULL) {
+		return PAM_BUF_ERR;
+	}
+	memset(resp, 0, sizeof(struct pam_response) * num_msg);
+	code = PAM_SUCCESS;
+	for (i = 0; i < num_msg; i++) {
+		message = &(msg[0][i]); /* XXX */
+		message = msg[i]; /* XXX */
+		pwstring = NULL;
+		switch (message->msg_style) {
+		case PAM_TEXT_INFO:
+		case PAM_ERROR_MSG:
+			printf("[%s]\n", message->msg ? message->msg : "");
+			fflush(stdout);
+			resp[i].resp = NULL;
+			resp[i].resp_retcode = PAM_SUCCESS;
+			break;
+		case PAM_PROMPT_ECHO_ON:
+		case PAM_PROMPT_ECHO_OFF:
+			if (message->msg_style == PAM_PROMPT_ECHO_ON) {
+				if (fgets(pwbuf, sizeof(pwbuf),
+					  stdin) != NULL) {
+					pwbuf[strcspn(pwbuf, "\r\n")] = '\0';
+					pwstring = pwbuf;
+				}
+			} else {
+				pwstring = getpass(message->msg ?
+						   message->msg :
+						   "");
+			}
+			if ((pwstring != NULL) && (pwstring[0] != '\0')) {
+				pwsize = strlen(pwstring);
+				resp[i].resp = malloc(pwsize + 1);
+				if (resp[i].resp == NULL) {
+					resp[i].resp_retcode = PAM_BUF_ERR;
+				} else {
+					memcpy(resp[i].resp, pwstring, pwsize);
+					resp[i].resp[pwsize] = '\0';
+					resp[i].resp_retcode = PAM_SUCCESS;
+				}
+			} else {
+				resp[i].resp_retcode = PAM_CONV_ERR;
+				code = PAM_CONV_ERR;
+			}
+			break;
+		default:
+			break;
+		}
+	}
+	*presp = resp;
+	return code;
+}
+static int
+appl_pam_non_interactive_converse(int num_msg,
+				  const struct pam_message **msg,
+				  struct pam_response **presp,
+				  void *appdata_ptr)
+{
+	const struct pam_message *message;
+	struct pam_response *resp;
+	int i, code;
+	unsigned int pwsize;
+	struct appl_pam_non_interactive_args *args;
+	const char *pwstring;
+	resp = malloc(sizeof(struct pam_response) * num_msg);
+	if (resp == NULL) {
+		return PAM_BUF_ERR;
+	}
+	args = appdata_ptr;
+	memset(resp, 0, sizeof(struct pam_response) * num_msg);
+	code = PAM_SUCCESS;
+	for (i = 0; i < num_msg; i++) {
+		message = &((*msg)[i]);
+		message = msg[i];
+		pwstring = NULL;
+		switch (message->msg_style) {
+		case PAM_TEXT_INFO:
+		case PAM_ERROR_MSG:
+			break;
+		case PAM_PROMPT_ECHO_ON:
+		case PAM_PROMPT_ECHO_OFF:
+			if (message->msg_style == PAM_PROMPT_ECHO_ON) {
+				/* assume "user" */
+				pwstring = args->user;
+			} else {
+				/* assume "password" */
+				pwstring = args->password;
+			}
+			if ((pwstring != NULL) && (pwstring[0] != '\0')) {
+				pwsize = strlen(pwstring);
+				resp[i].resp = malloc(pwsize + 1);
+				if (resp[i].resp == NULL) {
+					resp[i].resp_retcode = PAM_BUF_ERR;
+				} else {
+					memcpy(resp[i].resp, pwstring, pwsize);
+					resp[i].resp[pwsize] = '\0';
+					resp[i].resp_retcode = PAM_SUCCESS;
+				}
+			} else {
+				resp[i].resp_retcode = PAM_CONV_ERR;
+				code = PAM_CONV_ERR;
+			}
+			break;
+		default:
+			break;
+		}
+	}
+	*presp = resp;
+	return code;
+}
+static int
+appl_pam_start(const char *service, int interactive,
+	       const char *login_username,
+	       const char *non_interactive_password,
+	       const char *hostname,
+	       const char *ruser,
+	       const char *tty)
+{
+	static int exit_handler_registered;
+	static struct appl_pam_non_interactive_args args;
+	int ret = 0;
+	if (appl_pam_started &&
+	    (strcmp(login_username, appl_pam_user) != 0)) {
+		appl_pam_cleanup();
+		appl_pam_user = NULL;
+	}
+	if (!appl_pam_started) {
+#ifdef DEBUG
+		printf("Starting PAM up (service=\"%s\",user=\"%s\").\n",
+		       service, login_username);
+#endif
+		memset(&appl_pam_conv, 0, sizeof(appl_pam_conv));
+		appl_pam_conv.conv = interactive ?
+				     &appl_pam_interactive_converse :
+				     &appl_pam_non_interactive_converse;
+		memset(&args, 0, sizeof(args));
+		args.user = strdup(login_username);
+		args.password = non_interactive_password ?
+				strdup(non_interactive_password) :
+				NULL;
+		appl_pam_conv.appdata_ptr = &args;
+		ret = pam_start(service, login_username,
+				&appl_pam_conv, &appl_pamh);
+		if (ret == 0) {
+			if (hostname != NULL) {
+#ifdef DEBUG
+				printf("Setting PAM_RHOST to \"%s\".\n", hostname);
+#endif
+				pam_set_item(appl_pamh, PAM_RHOST, hostname);
+			}
+			if (ruser != NULL) {
+#ifdef DEBUG
+				printf("Setting PAM_RUSER to \"%s\".\n", ruser);
+#endif
+				pam_set_item(appl_pamh, PAM_RUSER, ruser);
+			}
+			if (tty != NULL) {
+#ifdef DEBUG
+				printf("Setting PAM_TTY to \"%s\".\n", tty);
+#endif
+				pam_set_item(appl_pamh, PAM_TTY, tty);
+			}
+			if (!exit_handler_registered &&
+			    (atexit(appl_pam_cleanup) != 0)) {
+				pam_end(appl_pamh, 0);
+				appl_pamh = NULL;
+				ret = -1;
+			} else {
+				appl_pam_started = 1;
+				appl_pam_starter = getpid();
+				appl_pam_user = strdup(login_username);
+				exit_handler_registered = 1;
+			}
+		}
+	}
+	return ret;
+}
+int
+appl_pam_acct_mgmt(const char *service, int interactive,
+		   const char *login_username,
+		   const char *non_interactive_password,
+		   const char *hostname,
+		   const char *ruser,
+		   const char *tty)
+{
+	int ret;
+	appl_pam_pwchange_required = 0;
+	ret = appl_pam_start(service, interactive, login_username,
+			     non_interactive_password, hostname, ruser, tty);
+	if (ret == 0) {
+#ifdef DEBUG
+		printf("Calling pam_acct_mgmt().\n");
+#endif
+		ret = pam_acct_mgmt(appl_pamh, 0);
+		switch (ret) {
+		case PAM_IGNORE:
+			ret = 0;
+			break;
+		case PAM_NEW_AUTHTOK_REQD:
+			appl_pam_pwchange_required = 1;
+			ret = 0;
+			break;
+		default:
+			break;
+		}
+	}
+	return ret;
+}
+int
+appl_pam_requires_chauthtok(void)
+{
+	return appl_pam_pwchange_required;
+}
+int
+appl_pam_session_open(void)
+{
+	int ret = 0;
+	if (appl_pam_started) {
+#ifdef DEBUG
+		printf("Opening PAM session.\n");
+#endif
+		ret = pam_open_session(appl_pamh, 0);
+		if (ret == 0) {
+			appl_pam_session_opened = 1;
+		}
+	}
+	return ret;
+}
+int
+appl_pam_setenv(void)
+{
+	int ret = 0;
+#ifdef HAVE_PAM_GETENVLIST
+#ifdef HAVE_PUTENV
+	int i;
+	char **list;
+	if (appl_pam_started) {
+		list = pam_getenvlist(appl_pamh);
+		for (i = 0; ((list != NULL) && (list[i] != NULL)); i++) {
+#ifdef DEBUG
+			printf("Setting \"%s\" in environment.\n", list[i]);
+#endif
+			putenv(list[i]);
+		}
+	}
+#endif
+#endif
+	return ret;
+}
+int
+appl_pam_cred_init(void)
+{
+	int ret = 0;
+	if (appl_pam_started) {
+#ifdef DEBUG
+		printf("Initializing PAM credentials.\n");
+#endif
+		ret = pam_setcred(appl_pamh, PAM_ESTABLISH_CRED);
+		if (ret == 0) {
+			appl_pam_creds_initialized = 1;
+		}
+	}
+	return ret;
+}
+#endif
diff --git a/src/clients/ksu/pam.h b/src/clients/ksu/pam.h
new file mode 100644
index 000000000..0ab76569c
--- /dev/null
+++ b/src/clients/ksu/pam.h
@@ -0,0 +1,57 @@
+/*
+ * src/clients/ksu/pam.h
+ *
+ * Copyright 2007,2009,2010 Red Hat, Inc.
+ *
+ * All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  Redistributions of source code must retain the above copyright notice, this
+ *  list of conditions and the following disclaimer.
+ *
+ *  Redistributions in binary form must reproduce the above copyright notice,
+ *  this list of conditions and the following disclaimer in the documentation
+ *  and/or other materials provided with the distribution.
+ *
+ *  Neither the name of Red Hat, Inc. nor the names of its contributors may be
+ *  used to endorse or promote products derived from this software without
+ *  specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * 
+ * Convenience wrappers for using PAM.
+ */
+
+#include <krb5.h>
+#ifdef HAVE_SECURITY_PAM_APPL_H
+#include <security/pam_appl.h>
+#endif
+
+#define USE_PAM_CONFIGURATION_KEYWORD "use_pam"
+
+#ifdef USE_PAM
+int appl_pam_enabled(krb5_context context, const char *section);
+int appl_pam_acct_mgmt(const char *service, int interactive,
+		       const char *local_username,
+		       const char *non_interactive_password,
+		       const char *hostname,
+		       const char *ruser,
+		       const char *tty);
+int appl_pam_requires_chauthtok(void);
+int appl_pam_session_open(void);
+int appl_pam_setenv(void);
+int appl_pam_cred_init(void);
+void appl_pam_cleanup(void);
+#endif
diff --git a/src/configure.ac b/src/configure.ac
index 4eb080784..693f76a81 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -1389,6 +1389,8 @@ AC_SUBST([VERTO_VERSION])
 
 AC_PATH_PROG(GROFF, groff)
 
+KRB5_WITH_PAM
+
 # Make localedir work in autoconf 2.5x.
 if test "${localedir+set}" != set; then
     localedir='$(datadir)/locale'