Disabled XTS mode in enc utility as it is not supported

PR#3442
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>

apps/enc.c

@@ -339,6 +339,12 @@ bad:
 		goto end;
 		}
 
+	if (cipher && (EVP_CIPHER_mode(cipher) == EVP_CIPH_XTS_MODE))
+		{
+		BIO_printf(bio_err, "Ciphers in XTS mode are not supported by the enc utility\n");
+		goto end;
+		}
+
 	if (md && (dgst=EVP_get_digestbyname(md)) == NULL)
 		{
 		BIO_printf(bio_err,"%s is an unsupported message digest type\n",md);