nss: use TLSv1.3 as default if supported

SSL_VersionRangeGetDefault returns (TLSv1.0, TLSv1.2) as supported
range in NSS 3.45. It looks like the intention is to raise the minimum
version rather than lowering the maximum, so adjust accordingly. Note
that the caller (nss_setup_connect) initializes the version range to
(TLSv1.0, TLSv1.3), so there is no need to check for >= TLSv1.0 again.

Closes #4187
Reviewed-by: Daniel Stenberg
Reviewed-by: Kamil Dudka

1 files changed, 6 insertions, 10 deletions

diff --git a/lib/vtls/nss.c b/lib/vtls/nss.c
index 482fd5e99..435f3e93a 100644
--- a/lib/vtls/nss.c
+++ b/lib/vtls/nss.c
@@ -1734,20 +1734,16 @@ static CURLcode nss_init_sslver(SSLVersionRange *sslver,
   CURLcode result;
   const long min = SSL_CONN_CONFIG(version);
   const long max = SSL_CONN_CONFIG(version_max);
-
-  /* map CURL_SSLVERSION_DEFAULT to NSS default */
-  if(min == CURL_SSLVERSION_DEFAULT || max == CURL_SSLVERSION_MAX_DEFAULT) {
-    /* map CURL_SSLVERSION_DEFAULT to NSS default */
-    if(SSL_VersionRangeGetDefault(ssl_variant_stream, sslver) != SECSuccess)
-      return CURLE_SSL_CONNECT_ERROR;
-    /* ... but make sure we use at least TLSv1.0 according to libcurl API */
-    if(sslver->min < SSL_LIBRARY_VERSION_TLS_1_0)
-      sslver->min = SSL_LIBRARY_VERSION_TLS_1_0;
-  }
+  SSLVersionRange vrange;
 
   switch(min) {
   case CURL_SSLVERSION_TLSv1:
   case CURL_SSLVERSION_DEFAULT:
+    /* Bump our minimum TLS version if NSS has stricter requirements. */
+    if(SSL_VersionRangeGetDefault(ssl_variant_stream, &vrange) != SECSuccess)
+      return CURLE_SSL_CONNECT_ERROR;
+    if(sslver->min < vrange.min)
+      sslver->min = vrange.min;
     break;
   default:
     result = nss_sslver_from_curl(&sslver->min, min);