rule parsing: valid that input rule string is UTF8

Before parsing a rule string, validate that it is UTF-8 first.

Related Redmine issue:
https://redmine.openinfosecfoundation.org/issues/3850

src/detect-parse.c

@@ -1212,6 +1212,11 @@ static int SigParse(DetectEngineCtx *de_ctx, Signature *s,
 {
     SCEnter();
 
+    if (!rs_check_utf8(sigstr)) {
+        SCLogError(SC_ERR_RULE_INVALID_UTF8, "rule is not valid UTF-8");
+        SCReturnInt(-1);
+    }
+
     s->sig_str = SCStrdup(sigstr);
     if (unlikely(s->sig_str == NULL)) {
         SCReturnInt(-1);

src/util-error.c

@@ -376,6 +376,7 @@ const char * SCErrorToString(SCError err)
         CASE_CODE (SC_WARN_PATH_READ_ERROR);
         CASE_CODE (SC_ERR_PLUGIN);
         CASE_CODE(SC_ERR_LOG_OUTPUT);
+        CASE_CODE(SC_ERR_RULE_INVALID_UTF8);
 
         CASE_CODE (SC_ERR_MAX);
     }

src/util-error.h

@@ -366,6 +366,7 @@ typedef enum {
     SC_ERR_HTTP2_LOG_GENERIC,
     SC_ERR_PLUGIN,
     SC_ERR_LOG_OUTPUT,
+    SC_ERR_RULE_INVALID_UTF8,
 
     SC_ERR_MAX
 } SCError;