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 curl#1166

docs/cmdline-opts/tls-max.d

@@ -0,0 +1,24 @@
+Long: tls-max
+Arg: <VERSION>
+Tags: Versions
+Protocols: SSL
+Added: 7.54.0
+Requires: TLS
+See-also: tlsv1.0 tlsv1.1 tlsv1.2
+Help: Use TLSv1.0 or greater
+---
+VERSION defines maximum supported TLS version. A minimum is defined
+by arguments tlsv1.0 or tlsv1.1 or tlsv1.2.
+
+.RS
+.IP "default"
+Use up to recommended TLS version.
+.IP "1.0"
+Use up to TLSv1.0.
+.IP "1.1"
+Use up to TLSv1.1.
+.IP "1.2"
+Use up to TLSv1.2.
+.IP "1.3"
+Use up to TLSv1.3.
+.RE

docs/libcurl/opts/CURLOPT_PROXY_SSLVERSION.3

@@ -46,6 +46,23 @@ TLSv1.1
 TLSv1.2
 .IP CURL_SSLVERSION_TLSv1_3
 TLSv1.3
+.IP CURL_SSLVERSION_MAX_DEFAULT
+The flag defines maximum supported TLS version as TLSv1.2 or default
+value from SSL library. Only library NSS currently allows to get
+maximum supported TLS version.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_0
+The flag defines maximum supported TLS version as TLSv1.0.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_1
+The flag defines maximum supported TLS version as TLSv1.1.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_2
+The flag defines maximum supported TLS version as TLSv1.2.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_3
+The flag defines maximum supported TLS version as TLSv1.3.
+(Added in 7.54.0)
 .RE
 .SH DEFAULT
 CURL_SSLVERSION_DEFAULT
@@ -58,7 +75,8 @@ if(curl) {
   curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
 
   /* ask libcurl to use TLS version 1.0 or later */
-  curl_easy_setopt(curl, CURLOPT_PROXY_SSLVERSION, CURL_SSLVERSION_TLSv1);
+  curl_easy_setopt(curl, CURLOPT_PROXY_SSLVERSION, CURL_SSLVERSION_TLSv1_1 |
+                   CURL_SSLVERSION_MAX_DEFAULT);
 
   /* Perform the request */
   curl_easy_perform(curl);

docs/libcurl/opts/CURLOPT_SSLVERSION.3

@@ -50,6 +50,23 @@ TLSv1.1 (Added in 7.34.0)
 TLSv1.2 (Added in 7.34.0)
 .IP CURL_SSLVERSION_TLSv1_3
 TLSv1.3 (Added in 7.52.0)
+.IP CURL_SSLVERSION_MAX_DEFAULT
+The flag defines maximum supported TLS version as TLSv1.2 or default
+value from SSL library. Only library NSS currently allows to get
+maximum supported TLS version.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_0
+The flag defines maximum supported TLS version as TLSv1.0.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_1
+The flag defines maximum supported TLS version as TLSv1.1.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_2
+The flag defines maximum supported TLS version as TLSv1.2.
+(Added in 7.54.0)
+.IP CURL_SSLVERSION_MAX_TLSv1_3
+The flag defines maximum supported TLS version as TLSv1.3.
+(Added in 7.54.0)
 .RE
 .SH DEFAULT
 CURL_SSLVERSION_DEFAULT
@@ -61,8 +78,9 @@ CURL *curl = curl_easy_init();
 if(curl) {
   curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
 
-  /* ask libcurl to use TLS version 1.0 or later */
-  curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);
+  /* ask libcurl to use TLS version 1.1 or later */
+  curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1.1 |
+                   CURL_SSLVERSION_MAX_DEFAULT);
 
   /* Perform the request */
   curl_easy_perform(curl);

docs/libcurl/symbols-in-versions

@@ -798,6 +798,12 @@ CURL_SSLVERSION_TLSv1_0         7.34.0
 CURL_SSLVERSION_TLSv1_1         7.34.0
 CURL_SSLVERSION_TLSv1_2         7.34.0
 CURL_SSLVERSION_TLSv1_3         7.52.0
+CURL_SSLVERSION_MAX_NONE        7.54.0
+CURL_SSLVERSION_MAX_DEFAULT     7.54.0
+CURL_SSLVERSION_MAX_TLSv1_0     7.54.0
+CURL_SSLVERSION_MAX_TLSv1_1     7.54.0
+CURL_SSLVERSION_MAX_TLSv1_2     7.54.0
+CURL_SSLVERSION_MAX_TLSv1_3     7.54.0
 CURL_TIMECOND_IFMODSINCE        7.9.7
 CURL_TIMECOND_IFUNMODSINCE      7.9.7
 CURL_TIMECOND_LASTMOD           7.9.7

include/curl/curl.h

@@ -1884,6 +1884,18 @@ enum {
   CURL_SSLVERSION_LAST /* never use, keep last */
 };
 
+enum {
+  CURL_SSLVERSION_MAX_NONE =     0,
+  CURL_SSLVERSION_MAX_DEFAULT =  (CURL_SSLVERSION_TLSv1   << 16),
+  CURL_SSLVERSION_MAX_TLSv1_0 =  (CURL_SSLVERSION_TLSv1_0 << 16),
+  CURL_SSLVERSION_MAX_TLSv1_1 =  (CURL_SSLVERSION_TLSv1_1 << 16),
+  CURL_SSLVERSION_MAX_TLSv1_2 =  (CURL_SSLVERSION_TLSv1_2 << 16),
+  CURL_SSLVERSION_MAX_TLSv1_3 =  (CURL_SSLVERSION_TLSv1_3 << 16),
+
+  /* never use, keep last */
+  CURL_SSLVERSION_MAX_LAST =     (CURL_SSLVERSION_LAST    << 16)
+};
+
 enum CURL_TLSAUTH {
   CURL_TLSAUTH_NONE,
   CURL_TLSAUTH_SRP,

lib/url.c

@@ -695,6 +695,9 @@ CURLcode Curl_open(struct Curl_easy **curl)
   return result;
 }
 
+#define C_SSLVERSION_VALUE(x) (x & 0xffff)
+#define C_SSLVERSION_MAX_VALUE(x) (x & 0xffff0000)
+
 CURLcode Curl_setopt(struct Curl_easy *data, CURLoption option,
                      va_list param)
 {
@@ -927,7 +930,9 @@ CURLcode Curl_setopt(struct Curl_easy *data, CURLoption option,
      * implementations are lame.
      */
 #ifdef USE_SSL
-    data->set.ssl.primary.version = va_arg(param, long);
+    arg = va_arg(param, long);
+    data->set.ssl.primary.version = C_SSLVERSION_VALUE(arg);
+    data->set.ssl.primary.version_max = C_SSLVERSION_MAX_VALUE(arg);
 #else
     result = CURLE_UNKNOWN_OPTION;
 #endif
@@ -938,7 +943,9 @@ CURLcode Curl_setopt(struct Curl_easy *data, CURLoption option,
      * implementations are lame.
      */
 #ifdef USE_SSL
-    data->set.proxy_ssl.primary.version = va_arg(param, long);
+    arg = va_arg(param, long);
+    data->set.proxy_ssl.primary.version = C_SSLVERSION_VALUE(arg);
+    data->set.proxy_ssl.primary.version_max = C_SSLVERSION_MAX_VALUE(arg);
 #else
     result = CURLE_UNKNOWN_OPTION;
 #endif

lib/urldata.h

@@ -350,6 +350,7 @@ struct ssl_connect_data {
 
 struct ssl_primary_config {
   long version;          /* what version the client wants to use */
+  long version_max;      /* max supported version the client wants to use*/
   bool verifypeer;       /* set TRUE if this is desired */
   bool verifyhost;       /* set TRUE if CN/SAN must match hostname */
   bool verifystatus;     /* set TRUE if certificate status must be checked */

lib/vtls/axtls.c

@@ -156,6 +156,12 @@ static CURLcode connect_prep(struct connectdata *conn, int sockindex)
        same connection */
     return CURLE_OK;
 
+  if(SSL_CONN_CONFIG(version_max) != CURL_SSLVERSION_MAX_NONE) {
+    failf(data, "axtls does not support CURL_SSLVERSION_MAX");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+
   /* axTLS only supports TLSv1 */
   /* check to see if we've been told to use an explicit SSL/TLS version */
   switch(SSL_CONN_CONFIG(version)) {

lib/vtls/cyassl.c

@@ -149,6 +149,11 @@ cyassl_connect_step1(struct connectdata *conn,
   if(conssl->state == ssl_connection_complete)
     return CURLE_OK;
 
+  if(SSL_CONN_CONFIG(version_max) != CURL_SSLVERSION_MAX_NONE) {
+    failf(data, "CyaSSL does not support to set maximum SSL/TLS version");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
   /* check to see if we've been told to use an explicit SSL/TLS version */
   switch(SSL_CONN_CONFIG(version)) {
   case CURL_SSLVERSION_DEFAULT:

lib/vtls/darwinssl.c

@@ -1044,6 +1044,109 @@ CF_INLINE bool is_file(const char *filename)
   return false;
 }
 
+#if CURL_BUILD_MAC_10_8 || CURL_BUILD_IOS
+static CURLcode darwinssl_version_from_curl(long *darwinver, long version)
+{
+  switch(ssl_version) {
+    case CURL_SSLVERSION_TLSv1_0:
+      *darwinver = kTLSProtocol1;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_1:
+      *darwinver = kTLSProtocol11;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_2:
+      *darwinver = kTLSProtocol12;
+      return CURLE_OK;
+    case CURL_SSLVERSION_TLSv1_3:
+      break;
+  }
+  return CURLE_SSL_CONNECT_ERROR;
+}
+#endif
+
+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];
+  long ssl_version = SSL_CONN_CONFIG(version);
+  long ssl_version_max = SSL_CONN_CONFIG(version_max);
+
+  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;
+  }
+
+#if CURL_BUILD_MAC_10_8 || CURL_BUILD_IOS
+  if(SSLSetProtocolVersionMax != NULL) {
+    SSLProtocol darwin_ver_min = kTLSProtocol1;
+    SSLProtocol darwin_ver_max = kTLSProtocol1;
+    CURLcode result = darwinssl_version_from_curl(&darwin_ver_min,
+                                                  ssl_version);
+    if(result) {
+      failf(data, "unsupported min version passed via CURLOPT_SSLVERSION");
+      return result;
+    }
+    result = darwinssl_version_from_curl(&darwin_ver_max,
+                                         ssl_version_max >> 16);
+    if(result) {
+      failf(data, "unsupported max version passed via CURLOPT_SSLVERSION");
+      return result;
+    }
+
+    (void)SSLSetProtocolVersionMin(connssl->ssl_ctx, darwin_ver_min);
+    (void)SSLSetProtocolVersionMax(connssl->ssl_ctx, darwin_ver_max);
+    return result;
+  }
+  else {
+#if CURL_SUPPORT_MAC_10_8
+    long i = ssl_version;
+    (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
+                                       kSSLProtocolAll,
+                                       false);
+    for(; i <= (ssl_version_max >> 16); i++) {
+      switch(i) {
+        case CURL_SSLVERSION_TLSv1_0:
+          (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
+                                            kTLSProtocol1,
+                                            true);
+          break;
+        case CURL_SSLVERSION_TLSv1_1:
+          (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
+                                            kTLSProtocol11,
+                                            true);
+          break;
+        case CURL_SSLVERSION_TLSv1_2:
+          (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
+                                            kTLSProtocol12,
+                                            true);
+          break;
+        case CURL_SSLVERSION_TLSv1_3:
+          failf(data, "DarwinSSL: TLS 1.3 is not yet supported");
+          return CURLE_SSL_CONNECT_ERROR;
+      }
+    }
+    return CURLE_OK;
+#endif  /* CURL_SUPPORT_MAC_10_8 */
+  }
+#endif  /* CURL_BUILD_MAC_10_8 || CURL_BUILD_IOS */
+  failf(data, "DarwinSSL: cannot set SSL protocol");
+  return CURLE_SSL_CONNECT_ERROR;
+}
+
+
 static CURLcode darwinssl_connect_step1(struct connectdata *conn,
                                         int sockindex)
 {
@@ -1113,20 +1216,15 @@ static CURLcode darwinssl_connect_step1(struct connectdata *conn,
       (void)SSLSetProtocolVersionMax(connssl->ssl_ctx, kTLSProtocol12);
       break;
     case CURL_SSLVERSION_TLSv1_0:
-      (void)SSLSetProtocolVersionMin(connssl->ssl_ctx, kTLSProtocol1);
-      (void)SSLSetProtocolVersionMax(connssl->ssl_ctx, kTLSProtocol1);
-      break;
     case CURL_SSLVERSION_TLSv1_1:
-      (void)SSLSetProtocolVersionMin(connssl->ssl_ctx, kTLSProtocol11);
-      (void)SSLSetProtocolVersionMax(connssl->ssl_ctx, kTLSProtocol11);
-      break;
     case CURL_SSLVERSION_TLSv1_2:
-      (void)SSLSetProtocolVersionMin(connssl->ssl_ctx, kTLSProtocol12);
-      (void)SSLSetProtocolVersionMax(connssl->ssl_ctx, kTLSProtocol12);
-      break;
     case CURL_SSLVERSION_TLSv1_3:
-      failf(data, "DarwinSSL: 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;
+      }
     case CURL_SSLVERSION_SSLv3:
       err = SSLSetProtocolVersionMin(connssl->ssl_ctx, kSSLProtocol3);
       if(err != noErr) {
@@ -1167,23 +1265,15 @@ static CURLcode darwinssl_connect_step1(struct connectdata *conn,
                                          true);
       break;
     case CURL_SSLVERSION_TLSv1_0:
-      (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
-                                         kTLSProtocol1,
-                                         true);
-      break;
     case CURL_SSLVERSION_TLSv1_1:
-      (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
-                                         kTLSProtocol11,
-                                         true);
-      break;
     case CURL_SSLVERSION_TLSv1_2:
-      (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
-                                         kTLSProtocol12,
-                                         true);
-      break;
     case CURL_SSLVERSION_TLSv1_3:
-      failf(data, "DarwinSSL: 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;
+      }
     case CURL_SSLVERSION_SSLv3:
       err = SSLSetProtocolVersionEnabled(connssl->ssl_ctx,
                                          kSSLProtocol3,
@@ -1209,6 +1299,11 @@ static CURLcode darwinssl_connect_step1(struct connectdata *conn,
 #endif  /* CURL_SUPPORT_MAC_10_8 */
   }
 #else
+  if(conn->ssl_config.version_max != CURL_SSLVERSION_MAX_NONE) {
+    failf(data, "Your version of the OS does not support to set maximum"
+                " SSL/TLS version");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
   (void)SSLSetProtocolVersionEnabled(connssl->ssl_ctx, kSSLProtocolAll, false);
   switch(conn->ssl_config.version) {
   case CURL_SSLVERSION_DEFAULT: