ustream-ssl: Revised security on mbedtls

The sender domain has a DMARC Reject/Quarantine policy which disallows
sending mailing list messages using the original "From" header.

To mitigate this problem, the original message has been wrapped
automatically by the mailing list software.
I've revised the security options, and made them more uniform across the
ssl libraries.

- use only TLS 1.2 in server mode
- changed the ciphersuite ordering

Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>

diff --git a/ustream-mbedtls.c b/ustream-mbedtls.c
index 9b22ad281174666f498045c187aa57f07e2dd3a7..347c6003fbbf73d1b019d1503304821c083451e3 100644 (file)
--- a/ustream-mbedtls.c
+++ b/ustream-mbedtls.c
@@ -86,33 +86,28 @@ static int _urandom(void *ctx, unsigned char *out, size_t len)
        return 0;
 }
 
-#define TLS_DEFAULT_CIPHERS                    \
-    TLS_CIPHER(AES_128_GCM_SHA256)             \
-    TLS_CIPHER(AES_256_GCM_SHA384)             \
-    TLS_CIPHER(AES_128_CBC_SHA)                        \
-    TLS_CIPHER(AES_256_CBC_SHA)                        \
-    TLS_CIPHER(3DES_EDE_CBC_SHA)
-
-static const int default_ciphersuites_nodhe[] =
+#define AES_CIPHERS(v)                                 \
+       MBEDTLS_TLS_##v##_WITH_AES_128_GCM_SHA256,      \
+       MBEDTLS_TLS_##v##_WITH_AES_256_GCM_SHA384,      \
+       MBEDTLS_TLS_##v##_WITH_AES_128_CBC_SHA,         \
+       MBEDTLS_TLS_##v##_WITH_AES_256_CBC_SHA
+
+static const int default_ciphersuites_server[] =
 {
-#define TLS_CIPHER(v)                          \
-       MBEDTLS_TLS_ECDHE_ECDSA_WITH_##v,       \
-       MBEDTLS_TLS_ECDHE_RSA_WITH_##v,         \
-       MBEDTLS_TLS_RSA_WITH_##v,
-       TLS_DEFAULT_CIPHERS
-#undef TLS_CIPHER
+       AES_CIPHERS(ECDHE_ECDSA),
+       AES_CIPHERS(ECDHE_RSA),
+       AES_CIPHERS(RSA),
        0
 };
 
-static const int default_ciphersuites[] =
+static const int default_ciphersuites_client[] =
 {
-#define TLS_CIPHER(v)                          \
-       MBEDTLS_TLS_ECDHE_ECDSA_WITH_##v,       \
-       MBEDTLS_TLS_ECDHE_RSA_WITH_##v,         \
-       MBEDTLS_TLS_DHE_RSA_WITH_##v,           \
-       MBEDTLS_TLS_RSA_WITH_##v,
-       TLS_DEFAULT_CIPHERS
-#undef TLS_CIPHER
+       AES_CIPHERS(ECDHE_ECDSA),
+       AES_CIPHERS(ECDHE_RSA),
+       AES_CIPHERS(DHE_RSA),
+       MBEDTLS_TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA,
+       AES_CIPHERS(RSA),
+       MBEDTLS_TLS_RSA_WITH_3DES_EDE_CBC_SHA,
        0
 };
 
@@ -152,10 +147,12 @@ __ustream_ssl_context_new(bool server)
        mbedtls_ssl_conf_authmode(conf, MBEDTLS_SSL_VERIFY_NONE);
        mbedtls_ssl_conf_rng(conf, _urandom, NULL);
 
-       if (server)
-               mbedtls_ssl_conf_ciphersuites(conf, default_ciphersuites_nodhe);
-       else
-               mbedtls_ssl_conf_ciphersuites(conf, default_ciphersuites);
+       if (server) {
+               mbedtls_ssl_conf_ciphersuites(conf, default_ciphersuites_server);
+               mbedtls_ssl_conf_min_version(conf, MBEDTLS_SSL_MAJOR_VERSION_3,
+                                            MBEDTLS_SSL_MINOR_VERSION_3);
+       } else
+               mbedtls_ssl_conf_ciphersuites(conf, default_ciphersuites_client);
 
 #if defined(MBEDTLS_SSL_CACHE_C)
        mbedtls_ssl_conf_session_cache(conf, &ctx->cache,