vtls: add options to specify range of enabled TLS versions

This commit introduces the CURL_SSLVERSION_MAX_* constants as well as
the --tls-max option of the curl tool.

Closes https://github.com/curl/curl/pull/1166

1 files changed, 71 insertions, 20 deletions

diff --git a/lib/vtls/mbedtls.c b/lib/vtls/mbedtls.c
index 07239bf26..dbcb1690c 100644
--- a/lib/vtls/mbedtls.c
+++ b/lib/vtls/mbedtls.c
@@ -157,6 +157,71 @@ const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_fr =
 static Curl_recv mbed_recv;
 static Curl_send mbed_send;
 
+static CURLcode mbedtls_version_from_curl(int *mbedver, long version)
+{
+  switch(ssl_version) {
+    case CURL_SSLVERSION_TLSv1_0:
+      *mbedver = MBEDTLS_SSL_MINOR_VERSION_1;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_1:
+      *mbedver = MBEDTLS_SSL_MINOR_VERSION_2;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_2:
+      *mbedver = MBEDTLS_SSL_MINOR_VERSION_3;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_3:
+      break;
+  }
+  return CURLE_SSL_CONNECT_ERROR;
+}
+
+static CURLcode
+set_ssl_version_min_max(struct connectdata *conn, int sockindex)
+{
+  struct Curl_easy *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  int mbedtls_ver_min = MBEDTLS_SSL_MINOR_VERSION_1;
+  int mbedtls_ver_max = MBEDTLS_SSL_MINOR_VERSION_1;
+  long ssl_version = SSL_CONN_CONFIG(version);
+  long ssl_version_max = SSL_CONN_CONFIG(version_max);
+  CURLcode result = CURLE_OK;
+
+  switch(ssl_version) {
+    case CURL_SSLVERSION_DEFAULT:
+    case CURL_SSLVERSION_TLSv1:
+      ssl_version = CURL_SSLVERSION_TLSv1_0;
+      ssl_version_max = CURL_SSLVERSION_MAX_TLSv1_2;
+      break;
+  }
+
+  switch(ssl_version_max) {
+    case CURL_SSLVERSION_MAX_NONE:
+      ssl_version_max = ssl_version << 16;
+      break;
+    case CURL_SSLVERSION_MAX_DEFAULT:
+      ssl_version_max = CURL_SSLVERSION_MAX_TLSv1_2;
+      break;
+  }
+
+  result = mbedtls_version_from_curl(&mbedtls_ver_min, ssl_version);
+  if(result) {
+    failf(data, "unsupported min version passed via CURLOPT_SSLVERSION");
+    return result;
+  }
+  result = mbedtls_version_from_curl(&mbedtls_ver_max, ssl_version_max >> 16);
+  if(result) {
+    failf(data, "unsupported max version passed via CURLOPT_SSLVERSION");
+    return result;
+  }
+
+  mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
+                               mbedtls_ver_min);
+  mbedtls_ssl_conf_max_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
+                               mbedtls_ver_max);
+
+  return result;
+}
+
 static CURLcode
 mbed_connect_step1(struct connectdata *conn,
                    int sockindex)
@@ -333,29 +398,15 @@ mbed_connect_step1(struct connectdata *conn,
     infof(data, "mbedTLS: Set SSL version to SSLv3\n");
     break;
   case CURL_SSLVERSION_TLSv1_0:
-    mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
-                                 MBEDTLS_SSL_MINOR_VERSION_1);
-    mbedtls_ssl_conf_max_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
-                                 MBEDTLS_SSL_MINOR_VERSION_1);
-    infof(data, "mbedTLS: Set SSL version to TLS 1.0\n");
-    break;
   case CURL_SSLVERSION_TLSv1_1:
-    mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
-                                 MBEDTLS_SSL_MINOR_VERSION_2);
-    mbedtls_ssl_conf_max_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
-                                 MBEDTLS_SSL_MINOR_VERSION_2);
-    infof(data, "mbedTLS: Set SSL version to TLS 1.1\n");
-    break;
   case CURL_SSLVERSION_TLSv1_2:
-    mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
-                                 MBEDTLS_SSL_MINOR_VERSION_3);
-    mbedtls_ssl_conf_max_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
-                                 MBEDTLS_SSL_MINOR_VERSION_3);
-    infof(data, "mbedTLS: Set SSL version to TLS 1.2\n");
-    break;
   case CURL_SSLVERSION_TLSv1_3:
-    failf(data, "mbedTLS: TLS 1.3 is not yet supported");
-    return CURLE_SSL_CONNECT_ERROR;
+    {
+      CURLcode result = set_ssl_version_min_max(conn, sockindex);
+      if(result != CURLE_OK)
+        return result;
+      break;
+    }
   default:
     failf(data, "Unrecognized parameter passed via CURLOPT_SSLVERSION");
     return CURLE_SSL_CONNECT_ERROR;