rainerscript: ensure parse_json consumes entire input string

This fix ensures that parse_json() only succeeds if the entire input
string is a valid JSON value. This prevents false positives when a
non-JSON string happens to start with a valid JSON value, like a number.
Documentation is updated to reflect this stricter validation.

Impact: Corrects false-success in parse_json() for malformed input.

Modified doFunc_parse_json in grammar/rainerscript.c to check if the
json-c tokener consumed the entire provided string. After parsing, the
remainder of the string is scanned for any non-whitespace characters.
If trailing garbage is found, the function now returns RS_SCRIPT_EINVAL
instead of RS_SCRIPT_EOK. Updated rs-parse_json.rst to document the
requirement for a complete JSON object/value. Added a regression test and
updated the testbench Makefile.am to include the new validation scenario.

Fixes: https://github.com/rsyslog/rsyslog/issues/4970
AI-Agent: Antigravity

doc/source/rainerscript/functions/rs-parse_json.rst

@@ -9,8 +9,11 @@ parse_json(str, container)
 
 Parses the json string ``str`` and places the resulting json object
 into ``container`` where container can be any valid rsyslog variable.
+Note that the **entire** ``str`` must be valid JSON for the function
+to succeed. If there is trailing data after a valid JSON object/value,
+it will be considered as an error.
 Returns 0 on success and something otherwise if ``str`` does **not**
-contain valid json.
+contain a valid, complete json string.
 
 
 Example

grammar/rainerscript.c

@@ -1822,11 +1822,22 @@ static void ATTR_NONNULL() doFunc_parse_json(struct cnffunc *__restrict__ const
     json = json_tokener_parse_ex(tokener, jsontext, strlen(jsontext));
     if (json == NULL) {
         retVal = RS_SCRIPT_EINVAL;
+    } else {
+        /* Check for trailing garbage */
+        int i = tokener->char_offset;
+        while (jsontext[i] != '\0' && isspace((uchar)jsontext[i])) {
+            i++;
+        }
+        if (jsontext[i] != '\0') {
+            json_object_put(json);
+            json = NULL;
+            retVal = RS_SCRIPT_EINVAL;
         } else {
             size_t off = (*container == '$') ? 1 : 0;
             msgAddJSON(pMsg, (uchar *)container + off, json, 0, 0);
             retVal = RS_SCRIPT_EOK;
         }
+    }
     wtiSetScriptErrno(pWti, retVal);
     json_tokener_free(tokener);
 

plugins/mmanon/mmanon.c

@@ -1321,7 +1321,8 @@ static rsRetVal findIPv6(struct ipv6_int *num, char *address, wrkrInstanceData_t
     struct hashtable *randConsisUniqueGeneratedIPs = useEmbedded
                                                          ? pWrkrData->pData->embeddedIPv4.randConsisUniqueGeneratedIPs
                                                          : pWrkrData->pData->ipv6.randConsisUniqueGeneratedIPs;
-    const int uniqueMode = useEmbedded ? pWrkrData->pData->embeddedIPv4.randConsisUnique : pWrkrData->pData->ipv6.randConsisUnique;
+    const int uniqueMode =
+        useEmbedded ? pWrkrData->pData->embeddedIPv4.randConsisUnique : pWrkrData->pData->ipv6.randConsisUnique;
     struct ipv6_int original = *num;
     struct ipv6_int *uniqueKey = NULL;
     sbool locked = 0;

tests/Makefile.am

@@ -449,6 +449,7 @@ TESTS +=  \
 	rscript_is_time.sh \
 	rscript_script_error.sh \
 	rscript_parse_json.sh \
+	rscript_parse_json_issue.sh \
 	rscript_previous_action_suspended.sh \
 	rscript_str2num_negative.sh \
 	rscript_exists-yes.sh \
@@ -2286,6 +2287,7 @@ EXTRA_DIST= \
 	rscript_is_time.sh \
 	rscript_script_error.sh \
 	rscript_parse_json.sh \
+	rscript_parse_json_issue.sh \
 	rscript_parse_json-vg.sh \
 	rscript_backticks-vg.sh \
 	rscript_backticks_empty_envvar.sh \

tests/rscript_parse_json_issue.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+# Reproduction for parse_json() issue
+. ${srcdir:=.}/diag.sh init
+generate_conf
+add_conf '
+module(load="../plugins/imtcp/.libs/imtcp")
+input(type="imtcp" port="0" listenPortFileName="'$RSYSLOG_DYNNAME'.tcpflood_port")
+template(name="outfmt" type="string" string="ret: %$.ret%, parsed: %$!parsed%\n")
+
+local4.* {
+    set $.ret = parse_json("22 08 23 this is a test message", "\$!parsed");
+    action(type="omfile" file=`echo $RSYSLOG_OUT_LOG` template="outfmt")
+}
+'
+startup
+tcpflood -m1
+shutdown_when_empty
+wait_shutdown
+
+export EXPECTED='ret: 1, parsed: '
+# Since the bug is that it returns 0 and parses "22", we expect ret: 0 and parsed: 22 if it fails.
+# We want it to be 1 and empty.
+cmp_exact $RSYSLOG_OUT_LOG
+
+exit_test