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Fix issues pointed out by nickm.

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- Rename tor_tls_got_server_hello() to tor_tls_got_client_hello().
- Replaced some aggressive asserts with LD_BUG logging.

  They were the innocent "I believe I understand how these callbacks
  work, and this assert proves it" type of callbacks, and not the "If
  this statement is not true, computer is exploding." type of
  callbacks.
- Added a changes file.
This commit is contained in:
George Kadianakis 2011-11-03 22:33:50 +01:00
parent e2b3527106
commit e097bffaed
2 changed files with 27 additions and 10 deletions
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11
changes/bug4312 Normal file
View File

@ -0,0 +1,11 @@
o Security fixes:
- Block excess renegotiations even if they are RFC5746 compliant.
This mitigates potential SSL Denial of Service attacks that use
SSL renegotiation as a way of forcing the server to perform
unneeded computationally expensive SSL handshakes. Implements
#4312.
- Fix a bug where tor would not notice excess renegotiation
attempts before it received the first data SSL record. Fixes
part of #4312.

26
src/common/tortls.c
View File

@ -1291,17 +1291,21 @@ tor_tls_client_is_using_v2_ciphers(const SSL *ssl, const char *address)
return 1;
}
/** We sent the ServerHello part of an SSL handshake. This might mean
* that we completed a renegotiation and appropriate actions must be
* taken. */
/** We got an SSL ClientHello message. This might mean that the
* client wants to initiate a renegotiation and appropriate actions
* must be taken. */
static void
tor_tls_got_server_hello(tor_tls_t *tls)
tor_tls_got_client_hello(tor_tls_t *tls)
{
if (tls->server_handshake_count < 3)
++tls->server_handshake_count;
if (tls->server_handshake_count == 2) {
tor_assert(tls->negotiated_callback);
if (!tls->negotiated_callback) {
log_warn(LD_BUG, "Got a renegotiation request but we don't"
" have a renegotiation callback set!");
}
tls->got_renegotiate = 1;
}
@ -1344,8 +1348,8 @@ tor_tls_state_changed_callback(const SSL *ssl, int type, int val)
if (type == SSL_CB_ACCEPT_LOOP &&
ssl->state == SSL3_ST_SW_SRVR_HELLO_A) {
/* Call tor_tls_got_server_hello() for every SSL ServerHello we
send. */
/* Call tor_tls_got_client_hello() for every SSL ClientHello we
receive. */
tor_tls_t *tls = tor_tls_get_by_ssl(ssl);
if (!tls) {
@ -1353,7 +1357,7 @@ tor_tls_state_changed_callback(const SSL *ssl, int type, int val)
return;
}
tor_tls_got_server_hello(tls);
tor_tls_got_client_hello(tls);
}
#endif
@ -1624,8 +1628,10 @@ tor_tls_read(tor_tls_t *tls, char *cp, size_t len)
#ifdef V2_HANDSHAKE_SERVER
if (tls->got_renegotiate) {
tor_assert(tls->server_handshake_count == 2);
/* XXX tor_assert(err == TOR_TLS_WANTREAD); */
if (tls->server_handshake_count != 2) {
log_warn(LD_BUG, "We did not notice renegotiation in a timely fashion (%u)!",
tls->server_handshake_count);
}
/* Renegotiation happened! */
log_info(LD_NET, "Got a TLS renegotiation from %s", ADDR(tls));