pam_motd: Fix segmentation fault when no motd_dir specified (#76)

This fixes a regression introduced by #69, where motd_path was set
to NULL and passed into strdup() if the motd_dir argument was
not specified in the configuration file. This caused a segmentation
fault.

* modules/pam_motd/pam_motd.c: fix checks for NULL in arguments
* xtests/Makefile.am: add test scripts and config file
* xtests/tst-pam_motd.sh: add running tst-pam_motd4.sh
* xtests/tst-pam_motd4.pamd: create
* xtests/tst-pam_motd4.sh: create

5 files changed, 43 insertions, 7 deletions

diff --git a/modules/pam_motd/pam_motd.c b/modules/pam_motd/pam_motd.c
index 1c1cfcfa..ec3ebd58 100644
--- a/modules/pam_motd/pam_motd.c
+++ b/modules/pam_motd/pam_motd.c
@@ -132,7 +132,6 @@ static int pam_split_string(const pam_handle_t *pamh, char *arg, char delim,
 	goto out;
     }
 
-
     arg_extracted = strtok_r(arg, delim_str, &arg);
     while (arg_extracted != NULL && i < num_strs) {
 	arg_split[i++] = arg_extracted;
@@ -363,15 +362,21 @@ int pam_sm_open_session(pam_handle_t *pamh, int flags,
 	motd_dir_path = default_motd_dir;
     }
 
-    motd_path_copy = strdup(motd_path);
+    if (motd_path != NULL) {
+	motd_path_copy = strdup(motd_path);
+    }
+
     if (motd_path_copy != NULL) {
-	if (pam_split_string(pamh, motd_path_copy, ':', &motd_path_split,
-		&num_motd_paths) == 0) {
+	if (pam_split_string(pamh, motd_path_copy, ':',
+		&motd_path_split, &num_motd_paths) == 0) {
 	    goto out;
 	}
     }
 
-    motd_dir_path_copy = strdup(motd_dir_path);
+    if (motd_dir_path != NULL) {
+	motd_dir_path_copy = strdup(motd_dir_path);
+    }
+
     if (motd_dir_path_copy != NULL) {
 	if (pam_split_string(pamh, motd_dir_path_copy, ':',
 		&motd_dir_path_split, &num_motd_dir_paths) == 0) {
diff --git a/xtests/Makefile.am b/xtests/Makefile.am
index 555d5e33..4d5aba3d 100644
--- a/xtests/Makefile.am
+++ b/xtests/Makefile.am
@@ -34,8 +34,8 @@ EXTRA_DIST = run-xtests.sh tst-pam_dispatch1.pamd tst-pam_dispatch2.pamd \
 	tst-pam_pwhistory1.pamd tst-pam_pwhistory1.sh \
 	tst-pam_time1.pamd time.conf \
 	tst-pam_motd.sh tst-pam_motd1.sh tst-pam_motd2.sh \
-	tst-pam_motd3.sh tst-pam_motd1.pamd \
-	tst-pam_motd2.pamd tst-pam_motd3.pamd
+	tst-pam_motd3.sh tst-pam_motd4.sh tst-pam_motd1.pamd \
+	tst-pam_motd2.pamd tst-pam_motd3.pamd tst-pam_motd4.pamd
 
 XTESTS = tst-pam_dispatch1 tst-pam_dispatch2 tst-pam_dispatch3 \
 	tst-pam_dispatch4 tst-pam_dispatch5 \
diff --git a/xtests/tst-pam_motd.sh b/xtests/tst-pam_motd.sh
index 9b0c38f6..90801280 100755
--- a/xtests/tst-pam_motd.sh
+++ b/xtests/tst-pam_motd.sh
@@ -5,3 +5,4 @@ set -e
 ./tst-pam_motd1.sh
 ./tst-pam_motd2.sh
 ./tst-pam_motd3.sh
+./tst-pam_motd4.sh
diff --git a/xtests/tst-pam_motd4.pamd b/xtests/tst-pam_motd4.pamd
new file mode 100644
index 00000000..9dc311ad
--- /dev/null
+++ b/xtests/tst-pam_motd4.pamd
@@ -0,0 +1,3 @@
+#%PAM-1.0
+session    required    pam_permit.so
+session    optional    pam_motd.so motd=tst-pam_motd4.d/etc/motd
diff --git a/xtests/tst-pam_motd4.sh b/xtests/tst-pam_motd4.sh
new file mode 100755
index 00000000..6022177f
--- /dev/null
+++ b/xtests/tst-pam_motd4.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+
+TST_DIR="tst-pam_motd4.d"
+
+function tst_cleanup() {
+    rm -rf "${TST_DIR}"
+    rm -f tst-pam_motd4.out
+}
+
+mkdir -p ${TST_DIR}/etc
+
+# Verify the case of single motd with no motd_dir given in tst-pam_motd4.pamd
+echo "motd: /etc/motd" > ${TST_DIR}/etc/motd
+
+./tst-pam_motd tst-pam_motd4 > tst-pam_motd4.out
+
+RET=$?
+
+motd_to_show_output=$(cat tst-pam_motd4.out | grep "motd: /etc/motd")
+if [ -z "${motd_to_show_output}" ];
+then
+    tst_cleanup
+    exit 1
+fi
+
+tst_cleanup
+exit $RET