Decoding of the SNI server_name allow to embed NUL Character

Motivation:

We incorrectly used NewStringUTF(...) to construct the java string which uses modified UTF-8 and so could result in have embed NUL chars. We need to ensure we re-construct the java string from the byte array to ensure nothing is re-interpreted.

Modifications:

Replace use of NewStringUTF(...) with tcn_new_stringn(...) which is the correct thing to use when creating a String from raw bytes received on the wire.

Result:

Correct converting of SNI server_name to java string

Author: normanmaurer

openssl-dynamic/src/main/c/ssl.c

@@ -2612,7 +2612,7 @@ TCN_IMPLEMENT_CALL(jstring, SSL, getSniHostname)(TCN_STDARGS, jlong ssl)
     if (servername == NULL) {
         return NULL;
     }
-    return tcn_new_string(e, servername);
+    return tcn_new_stringn(e, servername, strlen(servername));
 }
 
 TCN_IMPLEMENT_CALL(jboolean, SSL, isSessionReused)(TCN_STDARGS, jlong ssl)

openssl-dynamic/src/main/c/sslcontext.c

@@ -2616,7 +2616,7 @@ static int ssl_servername_cb(SSL *ssl, int *ad, void *arg)
         if (tcn_get_java_env(&e) != JNI_OK) {
             return SSL_TLSEXT_ERR_ALERT_FATAL;
         }
-        if ((servername_str = (*e)->NewStringUTF(e, servername)) == NULL) {
+        if ((servername_str = tcn_new_stringn(e, servername, strlen(servername))) == NULL) {
             return SSL_TLSEXT_ERR_ALERT_FATAL;
         }
         result = (*e)->CallBooleanMethod(e, c->sni_hostname_matcher, c->sni_hostname_matcher_method, P2J(ssl), servername_str);