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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.
This commit is contained in:
Nick Mathewson 2013-09-19 10:40:41 -04:00
parent fa1034cd99
commit 72c1e5acfe
3 changed files with 10 additions and 4 deletions
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8
changes/bug9780 Normal file
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@ -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.

2
doc/tor.1.txt
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@ -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

4
src/common/tortls.c
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@ -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? */