commit 0b319de60f7c80ab5c37c57af182f4f710ceb5b7 Author: Nick Mathewson nickm@torproject.org Date: Thu Apr 17 10:23:18 2014 -0400
Elevate server TLS cipher preferences over client
The server cipher list is (thanks to #11513) chosen systematically to put the best choices for Tor first. The client cipher list is chosen to resemble a browser. So let's set SSL_OP_CIPHER_SERVER_PREFERENCE to have the servers pick according to their own preference order. --- changes/ticket11528 | 6 ++++++ src/common/tortls.c | 4 ++++ 2 files changed, 10 insertions(+)
diff --git a/changes/ticket11528 b/changes/ticket11528 new file mode 100644 index 0000000..15daad9 --- /dev/null +++ b/changes/ticket11528 @@ -0,0 +1,6 @@ + o Minor features: + - Servers now trust themselves to have a better view than clients of + which TLS ciphersuites to choose. (Thanks to #11513, the server + list is now well-considered, whereas the client list has been + chosen mainly for anti-fingerprinting purposes.) Resolves ticket + 11528. diff --git a/src/common/tortls.c b/src/common/tortls.c index 886ee0d..8eb524e 100644 --- a/src/common/tortls.c +++ b/src/common/tortls.c @@ -1261,6 +1261,10 @@ tor_tls_context_new(crypto_pk_t *identity, unsigned int key_lifetime, goto error; SSL_CTX_set_options(result->ctx, SSL_OP_NO_SSLv2);
+ /* Prefer the server's ordering of ciphers: the client's ordering has + * historically been chosen for fingerprinting resistance. */ + SSL_CTX_set_options(result->ctx, SSL_OP_CIPHER_SERVER_PREFERENCE); + /* Disable TLS1.1 and TLS1.2 if they exist. We need to do this to * workaround a bug present in all OpenSSL 1.0.1 versions (as of 1 * June 2012), wherein renegotiating while using one of these TLS