journal: Add test cases that catch out-of-bounds read in journald

The test cases from commit 8595102 check for the return value of
syslog_parse_identifier() and will catch the condition that produced
vulnerability from CVE-2018-16866.

Add these tests to our stable branches.

Tested that these tests will fail if the fix for CVE-2018-16866 is missing
from the branch.

src/journal/test-journal-syslog.c

@@ -22,8 +22,8 @@
 #include "macro.h"
 #include "string-util.h"
 
-static void test_syslog_parse_identifier(const char* str,
-                                         const char *ident, const char*pid, int ret) {
+static void test_syslog_parse_identifier(const char *str,
+                                         const char *ident, const char *pid, const char *rest, int ret) {
         const char *buf = str;
         _cleanup_free_ char *ident2 = NULL, *pid2 = NULL;
         int ret2;
@@ -33,12 +33,22 @@ static void test_syslog_parse_identifier(const char* str,
         assert_se(ret == ret2);
         assert_se(ident == ident2 || streq_ptr(ident, ident2));
         assert_se(pid == pid2 || streq_ptr(pid, pid2));
+        assert_se(streq(buf, rest));
 }
 
 int main(void) {
-        test_syslog_parse_identifier("pidu[111]: xxx", "pidu", "111", 11);
-        test_syslog_parse_identifier("pidu: xxx", "pidu", NULL, 6);
-        test_syslog_parse_identifier("pidu xxx", NULL, NULL, 0);
+        test_syslog_parse_identifier("pidu[111]: xxx", "pidu", "111", "xxx", 11);
+        test_syslog_parse_identifier("pidu: xxx", "pidu", NULL, "xxx", 6);
+        test_syslog_parse_identifier("pidu:  xxx", "pidu", NULL, " xxx", 6);
+        test_syslog_parse_identifier("pidu xxx", NULL, NULL, "pidu xxx", 0);
+        test_syslog_parse_identifier("   pidu xxx", NULL, NULL, "   pidu xxx", 0);
+        test_syslog_parse_identifier("", NULL, NULL, "", 0);
+        test_syslog_parse_identifier("  ", NULL, NULL, "  ", 0);
+        test_syslog_parse_identifier(":", "", NULL, "", 1);
+        test_syslog_parse_identifier(":  ", "", NULL, " ", 2);
+        test_syslog_parse_identifier("pidu:", "pidu", NULL, "", 5);
+        test_syslog_parse_identifier("pidu: ", "pidu", NULL, "", 6);
+        test_syslog_parse_identifier("pidu : ", NULL, NULL, "pidu : ", 0);
 
         return 0;
 }