[tor-commits] [tor/maint-0.2.4] Switch ECDHE group default logic for bridge/relay TLS

[nickm at torproject.org]

commit 72c1e5acfe1c6f04f4d7d398fc4a964d4bc5b62e
Author: Nick Mathewson <nickm at torproject.org>
Date:   Thu Sep 19 10:40:41 2013 -0400

    Switch ECDHE group default logic for bridge/relay TLS
    
    According to the manpage, bridges use P256 for conformity and relays
    use P224 for speed. But skruffy points out that we've gotten it
    backwards in the code.
    
    In this patch, we make the default P256 for everybody.
    
    Fixes bug 9780; bugfix on 0.2.4.8-alpha.
---
 changes/bug9780     |    8 ++++++++
 doc/tor.1.txt       |    2 +-
 src/common/tortls.c |    4 +---
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/changes/bug9780 b/changes/bug9780
new file mode 100644
index 0000000..3cb51bd
--- /dev/null
+++ b/changes/bug9780
@@ -0,0 +1,8 @@
+  o Minor bugfixes (performance, fingerprinting):
+    - Our default TLS ecdhe groups were backwards: we meant to be using
+      P224 for relays (for performance win) and P256 for bridges (since
+      it is more common in the wild). Instead we had it backwards. After
+      reconsideration, we decided that the default should be P256 on all
+      hosts, since its security is probably better, and since P224 is
+      reportedly used quite little in the wild.  Found by "skruffy" on
+      IRC. Fix for bug 9780; bugfix on 0.2.4.8-alpha.
diff --git a/doc/tor.1.txt b/doc/tor.1.txt
index b206275..38423c2 100644
--- a/doc/tor.1.txt
+++ b/doc/tor.1.txt
@@ -1642,7 +1642,7 @@ is non-zero):
     What EC group should we try to use for incoming TLS connections?
     P224 is faster, but makes us stand out more. Has no effect if
     we're a client, or if our OpenSSL version lacks support for ECDHE.
-    (Default: P224 for public servers; P256 for bridges.)
+    (Default: P256)
 
 [[CellStatistics]] **CellStatistics** **0**|**1**::
     When this option is enabled, Tor writes statistics on the mean time that
diff --git a/src/common/tortls.c b/src/common/tortls.c
index b7e5bc1..72f6c40 100644
--- a/src/common/tortls.c
+++ b/src/common/tortls.c
@@ -1369,10 +1369,8 @@ tor_tls_context_new(crypto_pk_t *identity, unsigned int key_lifetime,
       nid = NID_secp224r1;
     else if (flags & TOR_TLS_CTX_USE_ECDHE_P256)
       nid = NID_X9_62_prime256v1;
-    else if (flags & TOR_TLS_CTX_IS_PUBLIC_SERVER)
-      nid = NID_X9_62_prime256v1;
     else
-      nid = NID_secp224r1;
+      nid = NID_X9_62_prime256v1;
     /* Use P-256 for ECDHE. */
     ec_key = EC_KEY_new_by_curve_name(nid);
     if (ec_key != NULL) /*XXXX Handle errors? */