ssl: Limit SSL to only support TLSv1.2 and TLSv1.3HEADmaster

This also restructures the SSL code to use the modern OpenSSL equivalent
of these functions simplifying internal code to be more readable.

Signed-off-by: GitHub <noreply@github.com>

2 files changed, 42 insertions, 50 deletions

diff --git a/include/rabbitmq-c/ssl_socket.h b/include/rabbitmq-c/ssl_socket.h
index ddedbd2..64930cc 100644
--- a/include/rabbitmq-c/ssl_socket.h
+++ b/include/rabbitmq-c/ssl_socket.h
@@ -189,6 +189,9 @@ typedef enum {
  * connecting to the broker. Set min == max to restrict to just that
  * version.
  *
+ * As of v0.14.0 the defaults are TLS v1.2 and TLS v1.3. TLS v1.1 and lower are
+ * no longer supported.
+ *
  * \param [in,out] self An SSL/TLS socket object.
  * \param [in] min the minimum acceptable TLS version
  * \param [in] max the maxmium acceptable TLS version
diff --git a/librabbitmq/amqp_openssl.c b/librabbitmq/amqp_openssl.c
index 3b79b45..55483c3 100644
--- a/librabbitmq/amqp_openssl.c
+++ b/librabbitmq/amqp_openssl.c
@@ -331,10 +331,11 @@ amqp_socket_t *amqp_ssl_socket_new(amqp_connection_state_t state) {
   if (!self->ctx) {
     goto error;
   }
-  /* Disable SSLv2 and SSLv3 */
-  SSL_CTX_set_options(self->ctx, SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3);
-  amqp_ssl_socket_set_ssl_versions((amqp_socket_t *)self, AMQP_TLSv1_2,
-                                   AMQP_TLSvLATEST);
+  status = amqp_ssl_socket_set_ssl_versions((amqp_socket_t *)self, AMQP_TLSv1_2,
+                                            AMQP_TLSvLATEST);
+  if (status != AMQP_STATUS_OK) {
+    goto error;
+  }
 
   SSL_CTX_set_mode(self->ctx, SSL_MODE_ENABLE_PARTIAL_WRITE);
   /* OpenSSL v1.1.1 turns this on by default, which makes the non-blocking
@@ -509,64 +510,52 @@ void amqp_ssl_socket_set_verify_hostname(amqp_socket_t *base,
   self->verify_hostname = verify;
 }
 
+static int get_tls_version(amqp_tls_version_t ver, int *tls_version) {
+  switch (ver) {
+    case AMQP_TLSv1_2:
+      *tls_version = TLS1_2_VERSION;
+      break;
+    case AMQP_TLSv1_3:
+    case AMQP_TLSvLATEST:
+      *tls_version = TLS1_3_VERSION;
+      break;
+    default:
+      return AMQP_STATUS_UNSUPPORTED;
+  }
+  return AMQP_STATUS_OK;
+}
+
 int amqp_ssl_socket_set_ssl_versions(amqp_socket_t *base,
                                      amqp_tls_version_t min,
                                      amqp_tls_version_t max) {
   struct amqp_ssl_socket_t *self;
+  int min_ver;
+  int max_ver;
+  int status;
   if (base->klass != &amqp_ssl_socket_class) {
     amqp_abort("<%p> is not of type amqp_ssl_socket_t", base);
   }
   self = (struct amqp_ssl_socket_t *)base;
 
-  {
-    long clear_options;
-    long set_options = 0;
-#if defined(SSL_OP_NO_TLSv1_3)
-    amqp_tls_version_t max_supported = AMQP_TLSv1_3;
-    clear_options = SSL_OP_NO_TLSv1 | SSL_OP_NO_TLSv1_1 | SSL_OP_NO_TLSv1_2 |
-                    SSL_OP_NO_TLSv1_3;
-#elif defined(SSL_OP_NO_TLSv1_2)
-    amqp_tls_version_t max_supported = AMQP_TLSv1_2;
-    clear_options = SSL_OP_NO_TLSv1 | SSL_OP_NO_TLSv1_1 | SSL_OP_NO_TLSv1_2;
-#else
-#error "Need a version of OpenSSL that can support TLSv1.2 or greater."
-#endif
-
-    if (AMQP_TLSvLATEST == max) {
-      max = max_supported;
-    }
-    if (AMQP_TLSvLATEST == min) {
-      min = max_supported;
-    }
+  if (max < min) {
+    return AMQP_STATUS_INVALID_PARAMETER;
+  }
 
-    if (min > max) {
-      return AMQP_STATUS_INVALID_PARAMETER;
-    }
+  status = get_tls_version(min, &min_ver);
+  if (status != AMQP_STATUS_OK) {
+    return status;
+  }
 
-    if (max > max_supported || min > max_supported) {
-      return AMQP_STATUS_UNSUPPORTED;
-    }
+  status = get_tls_version(max, &max_ver);
+  if (status != AMQP_STATUS_OK) {
+    return status;
+  }
 
-    if (min > AMQP_TLSv1) {
-      set_options |= SSL_OP_NO_TLSv1;
-    }
-#ifdef SSL_OP_NO_TLSv1_1
-    if (min > AMQP_TLSv1_1 || max < AMQP_TLSv1_1) {
-      set_options |= SSL_OP_NO_TLSv1_1;
-    }
-#endif
-#ifdef SSL_OP_NO_TLSv1_2
-    if (max < AMQP_TLSv1_2) {
-      set_options |= SSL_OP_NO_TLSv1_2;
-    }
-#endif
-#ifdef SSL_OP_NO_TLSv1_3
-    if (max < AMQP_TLSv1_3) {
-      set_options |= SSL_OP_NO_TLSv1_3;
-    }
-#endif
-    SSL_CTX_clear_options(self->ctx, clear_options);
-    SSL_CTX_set_options(self->ctx, set_options);
+  if (!SSL_CTX_set_min_proto_version(self->ctx, min_ver)) {
+    return AMQP_STATUS_INVALID_PARAMETER;
+  }
+  if (!SSL_CTX_set_max_proto_version(self->ctx, max_ver)) {
+    return AMQP_STATUS_INVALID_PARAMETER;
   }
 
   return AMQP_STATUS_OK;