Allow no-key, single-value JSON body

CHANGES

@@ -1,6 +1,8 @@
 DD mmm YYYY - 2.9.x (to be released)
 -------------------
 
+ * Allow no-key, single-value JSON body
+   [Issue #2735 - @marcstern, @martinhsv]
  * Set SecStatusEngine Off in modsecurity.conf-recommended
    [Issue #2717 - @un99known99, @martinhsv]
  * Fix memory leak that occurs on JSON parsing error

apache2/msc_json.c

@@ -27,8 +27,7 @@ int json_add_argument(modsec_rec *msr, const char *value, unsigned length)
      * to reference this argument; for now we simply ignore these
      */
     if (!msr->json->current_key) {
-        msr_log(msr, 3, "Cannot add scalar value without an associated key");
-        return 1;
+        msr->json->current_key = "";
     }
 
     arg = (msc_arg *) apr_pcalloc(msr->mp, sizeof(msc_arg));

apache2/msc_json.h

@@ -39,7 +39,7 @@ struct json_data {
 
     /* prefix is used to create data hierarchy (i.e., 'parent.child.value') */
     unsigned char *prefix;
-    unsigned char *current_key;
+    const unsigned char *current_key;
     long int current_depth;
     int depth_limit_exceeded;
 };

tests/regression/rule/15-json.t

@@ -224,6 +224,40 @@
 			),
 		),
 	),
+},
+{
+	type => "rule",
+	comment => "json parser - no-key single value",
+	conf => qq(
+		SecRuleEngine On
+		SecRequestBodyAccess On
+		SecDebugLog $ENV{DEBUG_LOG}
+                SecAuditEngine RelevantOnly
+                SecAuditLog "$ENV{AUDIT_LOG}"
+		SecDebugLogLevel 9
+		SecRequestBodyJsonDepthLimit 3
+		SecRule REQUEST_HEADERS:Content-Type "application/json" \\
+		     "id:'200001',phase:1,t:none,t:lowercase,pass,nolog,ctl:requestBodyProcessor=JSON"
+		SecRule REQBODY_ERROR "!\@eq 0" "id:'200444',phase:2,log,deny,status:403,msg:'Failed to parse request body'"
+		SecRule ARGS "\@streq 25" "id:'200445',phase:2,log,deny,status:403"
+	),
+	match_log => {
+		audit => [ qr/200445/s, 1 ],
+	},
+	match_response => {
+		status => qr/^403$/,
+	},
+	request => new HTTP::Request(
+		POST => "http://$ENV{SERVER_NAME}:$ENV{SERVER_PORT}/test.txt",
+		[
+			"Content-Type" => "application/json",
+		],
+		normalize_raw_request_data(
+			q(
+				25
+			),
+		),
+	),
 }