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, 39 insertions, 9 deletions

diff --git a/lib/vtls/gskit.c b/lib/vtls/gskit.c
index a0d462b70..d760b6a87 100644
--- a/lib/vtls/gskit.c
+++ b/lib/vtls/gskit.c
@@ -748,6 +748,40 @@ static ssize_t gskit_recv(struct connectdata *conn, int num, char *buf,
   return (ssize_t) nread;
 }
 
+static CURLcode
+set_ssl_version_min_max(unsigned int *protoflags, struct connectdata *conn)
+{
+  struct Curl_easy *data = conn->data;
+  long ssl_version = SSL_CONN_CONFIG(version);
+  long ssl_version_max = SSL_CONN_CONFIG(version_max);
+  long i = ssl_version;
+  switch(ssl_version_max) {
+    case CURL_SSLVERSION_MAX_NONE:
+      ssl_version_max = ssl_version;
+      break;
+    case CURL_SSLVERSION_MAX_DEFAULT:
+      ssl_version_max = CURL_SSLVERSION_TLSv1_2;
+      break;
+  }
+  for(; i <= (ssl_version_max >> 16); ++i) {
+    switch(i) {
+      case CURL_SSLVERSION_TLSv1_0:
+        *protoflags |= CURL_GSKPROTO_TLSV10_MASK;
+        break;
+      case CURL_SSLVERSION_TLSv1_1:
+        *protoflags |= CURL_GSKPROTO_TLSV11_MASK;
+        break;
+      case CURL_SSLVERSION_TLSv1_2:
+        *protoflags |= CURL_GSKPROTO_TLSV11_MASK;
+        break;
+      case CURL_SSLVERSION_TLSv1_3:
+        failf(data, "GSKit: TLS 1.3 is not yet supported");
+        return CURLE_SSL_CONNECT_ERROR;
+    }
+  }
+
+  return CURLE_OK;
+}
 
 static CURLcode gskit_connect_step1(struct connectdata *conn, int sockindex)
 {
@@ -764,7 +798,7 @@ static CURLcode gskit_connect_step1(struct connectdata *conn, int sockindex)
   const char * const hostname = SSL_IS_PROXY()? conn->http_proxy.host.name:
     conn->host.name;
   const char *sni;
-  unsigned int protoflags;
+  unsigned int protoflags = 0;
   long timeout;
   Qso_OverlappedIO_t commarea;
   int sockpair[2];
@@ -849,17 +883,13 @@ static CURLcode gskit_connect_step1(struct connectdata *conn, int sockindex)
                  CURL_GSKPROTO_TLSV11_MASK | CURL_GSKPROTO_TLSV12_MASK;
     break;
   case CURL_SSLVERSION_TLSv1_0:
-    protoflags = CURL_GSKPROTO_TLSV10_MASK;
-    break;
   case CURL_SSLVERSION_TLSv1_1:
-    protoflags = CURL_GSKPROTO_TLSV11_MASK;
-    break;
   case CURL_SSLVERSION_TLSv1_2:
-    protoflags = CURL_GSKPROTO_TLSV12_MASK;
-    break;
   case CURL_SSLVERSION_TLSv1_3:
-    failf(data, "GSKit: TLS 1.3 is not yet supported");
-    return CURLE_SSL_CONNECT_ERROR;
+    result = set_ssl_version_min_max(&protoflags, conn);
+    if(result != CURLE_OK)
+      return result;
+    break;
   default:
     failf(data, "Unrecognized parameter passed via CURLOPT_SSLVERSION");
     return CURLE_SSL_CONNECT_ERROR;