diff -up at-3.1.20/at.c.pam at-3.1.20/at.c

--- at-3.1.20/at.c.pam	2016-06-28 22:18:00.000000000 +0200

+++ at-3.1.20/at.c	2016-07-01 09:44:22.251683924 +0200

@@ -144,18 +144,13 @@ sigc(int signo)

 /* If the user presses ^C, remove the spool file and exit 

  */

     if (fcreated) {

-	/*

         PRIV_START

-

+        /*

         We need the unprivileged uid here since the file is owned by the real

         (not effective) uid.

         */

-        setregid(real_gid, effective_gid);

-	    unlink(atfile);

-        setregid(effective_gid, real_gid);

-        /*

+	unlink(atfile);

 	PRIV_END

-        */

     }

     exit(EXIT_FAILURE);

 }

@@ -315,26 +310,19 @@ writefile(time_t runtimer, char queue)

 	 * bit.  Yes, this is a kluge.

 	 */

 	cmask = umask(S_IRUSR | S_IWUSR | S_IXUSR);

-        seteuid(real_uid);

+       if ((seteuid(effective_uid)) < 0)

+	    perr("Error in seteuid: %s", errno);

 	if ((fd = open(atfile, O_CREAT | O_EXCL | O_TRUNC | O_WRONLY, S_IRUSR)) == -1)

 	    perr("Cannot create atjob file %.500s", atfile);

-        seteuid(effective_uid);

 	if ((fd2 = dup(fd)) < 0)

 	    perr("Error in dup() of job file");

-        /*

 	if (fchown(fd2, real_uid, real_gid) != 0)

-	    perr("Cannot give away file");

-        */

+	    perr("Cannot give real_uid and real_gid the file");

     PRIV_END

-    /* We no longer need suid root; now we just need to be able to write

-     * to the directory, if necessary.

-     */

-

-    REDUCE_PRIV(daemon_uid, daemon_gid)

     /* We've successfully created the file; let's set the flag so it 

      * gets removed in case of an interrupt or error.

      */

@@ -673,7 +661,7 @@ process_jobs(int argc, char **argv, int

                     We need the unprivileged uid here since the file is owned by the real

                     (not effective) uid.

                     */

-                    setregid(real_gid, effective_gid);

+		    PRIV_START

 		    if (queue == '=') {

 			fprintf(stderr, "Warning: deleting running job\n");

@@ -682,8 +670,8 @@ process_jobs(int argc, char **argv, int

 			perr("Cannot unlink %.500s", dirent->d_name);

 			rc = EXIT_FAILURE;

 		    }

+		    PRIV_END

-                    setregid(effective_gid, real_gid);

 		    done = 1;

 		    break;

@@ -693,7 +681,7 @@ process_jobs(int argc, char **argv, int

 			FILE *fp;

 			int ch;

-			setregid(real_gid, effective_gid);

+			PRIV_START

 			fp = fopen(dirent->d_name, "r");

 			if (fp) {

@@ -706,7 +694,7 @@ process_jobs(int argc, char **argv, int

 			    perr("Cannot open %.500s", dirent->d_name);

 			    rc = EXIT_FAILURE;

 			}

-			setregid(effective_gid, real_gid);

+			PRIV_END

 		    }

 		    break;

diff -up at-3.1.20/atd.c.pam at-3.1.20/atd.c

--- at-3.1.20/atd.c.pam	2016-06-28 22:14:39.000000000 +0200

+++ at-3.1.20/atd.c	2016-07-01 09:44:22.251683924 +0200

@@ -91,6 +91,10 @@ int selinux_enabled = 0;

 /* Macros */

+#ifndef LOG_ATD

+#define LOG_ATD        LOG_DAEMON

+#endif

+

 #define BATCH_INTERVAL_DEFAULT 60

 #define CHECK_INTERVAL 3600

@@ -114,7 +118,7 @@ static int run_as_daemon = 0;

 static volatile sig_atomic_t term_signal = 0;

-#ifdef HAVE_PAM

+#ifdef WITH_PAM

 #include <security/pam_appl.h>

 static pam_handle_t *pamh = NULL;

@@ -123,15 +127,7 @@ static const struct pam_conv conv = {

 	NULL

 };

-#define PAM_FAIL_CHECK if (retcode != PAM_SUCCESS) { \

-	fprintf(stderr,"\n%s\n",pam_strerror(pamh, retcode)); \

-	syslog(LOG_ERR,"%s",pam_strerror(pamh, retcode)); \

-	pam_end(pamh, retcode); exit(1); \

-    }

-#define PAM_END { retcode = pam_close_session(pamh,0); \

-		pam_end(pamh,retcode); }

-

-#endif /* HAVE_PAM */

+#endif /* WITH_PAM */

 /* Signal handlers */

 RETSIGTYPE 

@@ -292,7 +288,7 @@ run_file(const char *filename, uid_t uid

     char fmt[64];

     unsigned long jobno;

     int rc;

-#ifdef HAVE_PAM

+#ifdef WITH_PAM

     int retcode;

 #endif

@@ -449,17 +445,11 @@ run_file(const char *filename, uid_t uid

     fstat(fd_out, &buf;;

     size = buf.st_size;

-#ifdef HAVE_PAM

-    PRIV_START

-    retcode = pam_start("atd", pentry->pw_name, &conv, &pamh);

-    PAM_FAIL_CHECK;

-    retcode = pam_acct_mgmt(pamh, PAM_SILENT);

-    PAM_FAIL_CHECK;

-    retcode = pam_open_session(pamh, PAM_SILENT);

-    PAM_FAIL_CHECK;

-    retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED | PAM_SILENT);

-    PAM_FAIL_CHECK;

-    PRIV_END

+#ifdef WITH_PAM

+    AT_START_PAM;

+    AT_OPEN_PAM_SESSION;

+    closelog(); 

+    openlog("atd", LOG_PID, LOG_ATD);

 #endif

     close(STDIN_FILENO);

@@ -473,7 +463,14 @@ run_file(const char *filename, uid_t uid

     else if (pid == 0) {

 	char *nul = NULL;

 	char **nenvp = &nul;

+	char **pam_envp=0L;

+	PRIV_START

+#ifdef WITH_PAM

+	pam_envp = pam_getenvlist(pamh);

+	if ( ( pam_envp != 0L ) && (pam_envp[0] != 0L) )

+		nenvp = pam_envp;

+#endif

 	/* Set up things for the child; we want standard input from the

 	 * input file, and standard output and error sent to our output file.

 	 */

@@ -492,8 +489,6 @@ run_file(const char *filename, uid_t uid

 	close(fd_in);

 	close(fd_out);

-	PRIV_START

-

 	    nice((tolower((int) queue) - 'a' + 1) * 2);

 #ifdef WITH_SELINUX

@@ -514,9 +509,9 @@ run_file(const char *filename, uid_t uid

 	    chdir("/");

-	    if (execle("/bin/sh", "sh", (char *) NULL, nenvp) != 0)

-		perr("Exec failed for /bin/sh");

-

+	    execle("/bin/sh", "sh", (char *) NULL, nenvp);

+	    perr("Exec failed for /bin/sh");

+            /* perr exits, the PRIV_END is just for nice form */

 	PRIV_END

     }

     /* We're the parent.  Let's wait.

@@ -529,14 +524,6 @@ run_file(const char *filename, uid_t uid

      */

     waitpid(pid, (int *) NULL, 0);

-#ifdef HAVE_PAM

-    PRIV_START

-	pam_setcred(pamh, PAM_DELETE_CRED | PAM_SILENT);

-	retcode = pam_close_session(pamh, PAM_SILENT);

-	pam_end(pamh, retcode);

-    PRIV_END

-#endif

-

     /* Send mail.  Unlink the output file after opening it, so it

      * doesn't hang around after the run.

      */

@@ -567,8 +554,13 @@ run_file(const char *filename, uid_t uid

     unlink(newname);

     free(newname);

+#ifdef ATD_MAIL_PROGRAM

     if (((send_mail != -1) && (buf.st_size != size)) || (send_mail == 1)) {

+       int mail_pid = -1;

+     mail_pid = fork();

+

+     if ( mail_pid == 0 ) {

 	PRIV_START

 	    if (initgroups(pentry->pw_name, pentry->pw_gid))

@@ -590,7 +582,20 @@ run_file(const char *filename, uid_t uid

 	    perr("Exec failed for mail command");

 	PRIV_END

+     }

+     else if ( mail_pid == -1 ) {

+           syslog(LOG_ERR, "fork of mailer failed: %m");

+     }

+     /* Parent */

+     waitpid(mail_pid, (int *) NULL, 0);

     }

+

+#ifdef WITH_PAM

+    AT_CLOSE_PAM;

+    closelog();

+    openlog("atd", LOG_PID, LOG_ATD);

+#endif

+#endif

     exit(EXIT_SUCCESS);

 }

diff -up at-3.1.20/config.h.in.pam at-3.1.20/config.h.in

--- at-3.1.20/config.h.in.pam	2015-12-18 21:29:24.000000000 +0100

+++ at-3.1.20/config.h.in	2016-07-01 09:44:22.251683924 +0200

@@ -68,8 +68,8 @@

 /* Define to 1 if you have the <nlist.h> header file. */

 #undef HAVE_NLIST_H

-/* Define to 1 for PAM support */

-#undef HAVE_PAM

+/* Define if you are building with_pam */

+#undef WITH_PAM

 /* Define to 1 if you have the `pstat_getdynamic' function. */

 #undef HAVE_PSTAT_GETDYNAMIC

diff -up at-3.1.20/configure.ac.pam at-3.1.20/configure.ac

--- at-3.1.20/configure.ac.pam	2016-06-28 22:55:52.000000000 +0200

+++ at-3.1.20/configure.ac	2016-07-01 09:45:23.268092527 +0200

@@ -78,7 +78,7 @@ AC_FUNC_GETLOADAVG

 AC_CHECK_FUNCS(getcwd mktime strftime setreuid setresuid sigaction waitpid)

 AC_CHECK_HEADERS(security/pam_appl.h, [

   PAMLIB="-lpam"

-  AC_DEFINE(HAVE_PAM, 1, [Define to 1 for PAM support])

+  AC_DEFINE(WITH_PAM, 1, [Define to 1 for PAM support])

 ])

 dnl Checking for programs

@@ -239,6 +239,13 @@ AC_ARG_WITH(daemon_username,

 )

 AC_SUBST(DAEMON_USERNAME)

+AC_ARG_WITH(pam,

+[ --with-pam            Define to enable pam support ],

+AC_DEFINE(WITH_PAM),

+)

+AC_CHECK_LIB(pam, pam_start, PAMLIB='-lpam -lpam_misc')

+AC_SUBST(PAMLIB)

+

 AC_ARG_WITH(selinux,

 [ --with-selinux       Define to run with selinux (default=check)],

 [],

diff -up at-3.1.20/Makefile.in.pam at-3.1.20/Makefile.in

--- at-3.1.20/Makefile.in.pam	2016-07-01 09:44:22.250683901 +0200

+++ at-3.1.20/Makefile.in	2016-07-01 09:44:22.252683947 +0200

@@ -68,7 +68,7 @@ LIST = Filelist Filelist.asc

 all: at atd atd.service atrun

 at: $(ATOBJECTS)

-	$(CC) $(LDFLAGS) -pie -o at $(ATOBJECTS) $(LIBS) $(LEXLIB)

+	$(CC) $(LDFLAGS) -pie -o at $(ATOBJECTS) $(LIBS) $(LEXLIB) $(PAMLIB)

 	rm -f $(CLONES)

 	$(LN_S) -f at atq

 	$(LN_S) -f at atrm

diff -up at-3.1.20/perm.c.pam at-3.1.20/perm.c

--- at-3.1.20/perm.c.pam	2015-08-22 00:09:22.000000000 +0200

+++ at-3.1.20/perm.c	2016-07-01 09:44:22.252683947 +0200

@@ -51,6 +51,14 @@

 #define PRIV_END while(0)

 #endif

+#ifdef WITH_PAM

+#include <security/pam_appl.h>

+static pam_handle_t *pamh = NULL;

+static const struct pam_conv conv = {

+       NULL

+};

+#endif

+

 /* Structures and unions */

@@ -108,18 +116,45 @@ user_in_file(const char *path, const cha

 int

 check_permission()

 {

-  uid_t uid = geteuid();

+  uid_t euid = geteuid(), uid=getuid(), egid=getegid(), gid=getgid();

   struct passwd *pentry;

   int    allow = 0, deny = 1;

-  if (uid == 0)

+  int    retcode = 0;

+  if (euid == 0)

     return 1;

-  if ((pentry = getpwuid(uid)) == NULL) {

+  if ((pentry = getpwuid(euid)) == NULL) {

     perror("Cannot access user database");

     exit(EXIT_FAILURE);

   }

+#ifdef  WITH_PAM

+/*

+ *  We must check if the atd daemon userid will be allowed to gain the job owner user's

+ *  credentials with PAM . If not, the user has been denied at(1) usage, eg. with pam_access.

+ */

+  if (setreuid(daemon_uid, daemon_uid) != 0) {

+      fprintf(stderr, "cannot set egid: %s", strerror(errno));

+      exit(1);

+  }

+  if (setregid(daemon_gid, daemon_gid) != 0) {

+      fprintf(stderr, "cannot set euid: %s", strerror(errno));

+      exit(1);

+  }

+

+    AT_START_PAM;

+    AT_CLOSE_PAM;

+    if (setregid(gid,egid) != 0) {

+        fprintf(stderr, "cannot set egid: %s", strerror(errno));

+        exit(1);

+    }

+    if (setreuid(uid,euid) != 0) {

+        fprintf(stderr, "cannot set euid: %s", strerror(errno));

+        exit(1);

+    }

+#endif

+

   allow = user_in_file(ETCDIR "/at.allow", pentry->pw_name);

   if (allow==0 || allow==1)

     return allow;

diff -up at-3.1.20/privs.h.pam at-3.1.20/privs.h

--- at-3.1.20/privs.h.pam	2015-08-22 00:09:22.000000000 +0200

+++ at-3.1.20/privs.h	2016-07-01 09:44:22.252683947 +0200

@@ -144,3 +144,63 @@ extern gid_t real_gid, effective_gid, da

 #error "Cannot implement user ID swapping without setreuid or setresuid"

 #endif

 #endif

+

+#ifdef WITH_PAM

+/* PAM failed after session was open.  */

+#define PAM_SESSION_FAIL if (retcode != PAM_SUCCESS) \

+       pam_close_session(pamh,PAM_SILENT);

+

+/* syslog will be logging error messages */

+#ifdef HAVE_UNISTD_H

+#include <syslog.h>

+#endif

+

+/* PAM fail even before opening the session */

+#define PAM_FAIL_CHECK \

+       do { if (retcode != PAM_SUCCESS) { \

+               fprintf(stderr,"PAM failure: %s\n",pam_strerror(pamh, retcode)); \

+               syslog(LOG_ERR,"%s",pam_strerror(pamh, retcode)); \

+               if (pamh) \

+                   pam_end(pamh, retcode); \

+               if (setregid(getgid(),getegid()) != 0) { \

+                   fprintf(stderr, "cannot set egid: %s", strerror(errno)); \

+                   exit(1); \

+               } \

+               if (setreuid(getuid(),geteuid()) != 0) { \

+                   fprintf(stderr, "cannot set euid: %s", strerror(errno)); \

+                   exit(1); \

+               } \

+               exit(1); \

+           } \

+       } while (0) \

+

+static int pam_session_opened = 0;      //global for open session

+

+#define AT_START_PAM { \

+        retcode = pam_start("atd", pentry->pw_name, &conv, &pamh); \

+        PAM_FAIL_CHECK; \

+        retcode = pam_set_item(pamh, PAM_TTY, "atd"); \

+        PAM_FAIL_CHECK; \

+        retcode = pam_acct_mgmt(pamh, PAM_SILENT); \

+        PAM_FAIL_CHECK; \

+} 

+

+#define AT_OPEN_PAM_SESSION { \

+        retcode = pam_open_session(pamh, PAM_SILENT); \

+        PAM_FAIL_CHECK; \

+        retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED | PAM_SILENT); \

+        PAM_FAIL_CHECK; \

+        if (retcode == PAM_SUCCESS) \

+                pam_session_opened = 1; \

+}

+

+#define AT_CLOSE_PAM { \

+        if (pam_session_opened != 0) { \

+                pam_setcred(pamh, PAM_DELETE_CRED | PAM_SILENT); \

+                pam_close_session(pamh, PAM_SILENT); \

+        } \

+        pam_end(pamh, PAM_SUCCESS); \

+}

+

+#endif

+