sanity check for empty directory strings

Author: JacobBarthelmeh

wolfcrypt/src/asn.c

@@ -13903,6 +13903,18 @@ static int GetCertName(DecodedCert* cert, char* full, byte* hash, int nameType,
                 return ASN_PARSE_E;
             }
 
+        #ifndef WOLFSSL_NO_ASN_STRICT
+            /* RFC 5280 section 4.1.2.4 lists a DirecotryString as being
+             * 1..MAX in length */
+            if (strLen < 1) {
+                WOLFSSL_MSG("Non conforming DirectoryString of length 0 was"
+                            " found");
+                WOLFSSL_MSG("Use WOLFSSL_NO_ASN_STRICT if wanting to allow"
+                            " empty DirectoryString's");
+                return ASN_PARSE_E;
+            }
+        #endif
+
             if (id == ASN_COMMON_NAME) {
                 if (nameType == SUBJECT) {
                     cert->subjectCN = (char *)&input[srcIdx];
@@ -14533,6 +14545,18 @@ static int GetCertName(DecodedCert* cert, char* full, byte* hash, int nameType,
                 /* Get string reference. */
                 GetASN_GetRef(&dataASN[RDNASN_IDX_ATTR_VAL], &str, &strLen);
 
+            #ifndef WOLFSSL_NO_ASN_STRICT
+                /* RFC 5280 section 4.1.2.4 lists a DirecotryString as being
+                 * 1..MAX in length */
+                if (ret == 0 && strLen < 1) {
+                    WOLFSSL_MSG("Non conforming DirectoryString of length 0 was"
+                                " found");
+                    WOLFSSL_MSG("Use WOLFSSL_NO_ASN_STRICT if wanting to allow"
+                                " empty DirectoryString's");
+                    ret = ASN_PARSE_E;
+                }
+            #endif
+
                 /* Convert BER tag to a OpenSSL type. */
                 switch (tag) {
                     case CTC_UTF8: