TLS state leaks for every plain HTTP request on the websocket port #376

For a TLS connection, do_handshake() in common/network/websocket.c creates an SSL_CTX and an SSL. Every early return (each plain HTTP request for a file of the web client, and each refused or failed handshake) frees the connection context with free_ws_ctx() only; just the websocket path calls ws_socket_free(). So each file request over TLS leaks its SSL and SSL_CTX. One page load of the web client is 35 such requests.

Measured on 1.3.2 (kasmweb/chromium:1.16.0): 2000 requests for /package.json grew Xvnc by 75 MB (about 38 KB each); with the change below, by 0.4 MB. The code is the same on master.

The change we ship, against v1.3.2 (ws_socket_free() already sets both pointers to NULL, so nothing is freed twice):

--- a/common/network/websocket.c
+++ b/common/network/websocket.c
@@ -248,6 +248,18 @@ ws_ctx_t *alloc_ws_ctx() {
 }
 
 void free_ws_ctx(ws_ctx_t *ctx) {
+    // The handshake's early returns (plain HTTP requests, refused or failed
+    // handshakes) free the context without ws_socket_free(); release the TLS
+    // state here so a TLS connection does not leak its SSL and SSL_CTX.
+    // ws_socket_free() clears both pointers, so nothing is freed twice.
+    if (ctx->ssl) {
+        SSL_free(ctx->ssl);
+        ctx->ssl = NULL;
+    }
+    if (ctx->ssl_ctx) {
+        SSL_CTX_free(ctx->ssl_ctx);
+        ctx->ssl_ctx = NULL;
+    }
     free(ctx->cin_buf);
     free(ctx->cout_buf);
     free(ctx->tin_buf);