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Also handle needless renegotiations in SSL_write().

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SSL_read(), SSL_write() and SSL_do_handshake() can always progress the
SSL protocol instead of their normal operation, this means that we
must be checking for needless renegotiations after they return.

Introduce tor_tls_got_excess_renegotiations() which makes the
          tls->server_handshake_count > 2
check for us, and use it in tor_tls_read() and tor_tls_write().

Cases that should not be handled:

* SSL_do_handshake() is only called by tor_tls_renegotiate() which is a
  client-only function.

* The SSL_read() in tor_tls_shutdown() does not need to be handled,
  since SSL_shutdown() will be called if SSL_read() returns an error.
This commit is contained in:
George Kadianakis 2011-10-26 13:36:30 +02:00
parent 340809dd22
commit e2b3527106
1 changed files with 24 additions and 8 deletions
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32
src/common/tortls.c
View File

@ -1228,6 +1228,17 @@ tor_tls_context_new(crypto_pk_env_t *identity, unsigned int key_lifetime)
return NULL;
}
/** Return true if the <b>tls</b> object has completed more
* renegotiations than needed for the Tor protocol. */
static INLINE int
tor_tls_got_excess_renegotiations(tor_tls_t *tls)
{
/** The Tor v2 server handshake needs a single renegotiation after
the initial SSL handshake. This means that if we ever see more
than 2 handshakes, we raise the flag. */
return (tls->server_handshake_count > 2) ? 1 : 0;
}
#ifdef V2_HANDSHAKE_SERVER
/** Return true iff the cipher list suggested by the client for <b>ssl</b> is
* a list that indicates that the client knows how to do the v2 TLS connection
@ -1605,6 +1616,12 @@ tor_tls_read(tor_tls_t *tls, char *cp, size_t len)
err = tor_tls_get_error(tls, r, CATCH_ZERO, "reading", LOG_DEBUG, LD_NET);
if (tor_tls_got_excess_renegotiations(tls)) {
log_info(LD_NET, "Detected excess renegotiation from %s!", ADDR(tls));
return TOR_TLS_ERROR_MISC;
}
#ifdef V2_HANDSHAKE_SERVER
if (tls->got_renegotiate) {
tor_assert(tls->server_handshake_count == 2);
@ -1617,14 +1634,6 @@ tor_tls_read(tor_tls_t *tls, char *cp, size_t len)
tls->got_renegotiate = 0;
return r;
} else if (tls->server_handshake_count > 2) {
/* If we get more than 2 handshakes, it means that our peer is
trying to re-renegotiate. Return an error. */
tor_assert(tls->server_handshake_count == 3);
log_info(LD_NET, "Detected excess renegotiation from %s!", ADDR(tls));
return TOR_TLS_ERROR_MISC;
}
#endif
@ -1664,6 +1673,13 @@ tor_tls_write(tor_tls_t *tls, const char *cp, size_t n)
}
r = SSL_write(tls->ssl, cp, (int)n);
err = tor_tls_get_error(tls, r, 0, "writing", LOG_INFO, LD_NET);
if (tor_tls_got_excess_renegotiations(tls)) {
log_info(LD_NET, "Detected excess renegotiation from %s!", ADDR(tls));
return TOR_TLS_ERROR_MISC;
}
if (err == TOR_TLS_DONE) {
return r;
}