commit 616b60cef39f78d8a6ebb984096ff0ec09a3021c Author: Nick Mathewson nickm@torproject.org Date: Tue Dec 6 19:49:20 2011 -0500
Revert "Use callback-driven approach to block renegotiations."
This reverts commit 406ae1ba5ad529a4d0e710229dab6ed645d42b50. --- src/common/compat_libevent.c | 9 ------ src/common/compat_libevent.h | 3 -- src/common/tortls.c | 57 ++++++++++++++++++++--------------------- src/common/tortls.h | 4 +-- src/or/connection_or.c | 20 +------------- 5 files changed, 31 insertions(+), 62 deletions(-)
diff --git a/src/common/compat_libevent.c b/src/common/compat_libevent.c index fcc1193..7a28c9b 100644 --- a/src/common/compat_libevent.c +++ b/src/common/compat_libevent.c @@ -559,15 +559,6 @@ tor_check_libevent_header_compatibility(void) #endif }
-/** Wrapper around libevent's event_base_once(). Sets a - * timeout-triggered event with no associated file descriptor. */ -int -tor_event_base_once(void (*cb)(evutil_socket_t, short, void *), - void *arg, struct timeval *timer) -{ - return event_base_once(tor_libevent_get_base(), -1, EV_TIMEOUT, cb, arg, timer); -} - /* If possible, we're going to try to use Libevent's periodic timer support, since it does a pretty good job of making sure that periodic events get diff --git a/src/common/compat_libevent.h b/src/common/compat_libevent.h index 897eddb..0247297 100644 --- a/src/common/compat_libevent.h +++ b/src/common/compat_libevent.h @@ -46,9 +46,6 @@ void tor_event_free(struct event *ev);
typedef struct periodic_timer_t periodic_timer_t;
-int tor_event_base_once(void (*cb)(evutil_socket_t, short, void *), - void *arg, struct timeval *timer); - periodic_timer_t *periodic_timer_new(struct event_base *base, const struct timeval *tv, void (*cb)(periodic_timer_t *timer, void *data), diff --git a/src/common/tortls.c b/src/common/tortls.c index 2ef2803..62d34f7 100644 --- a/src/common/tortls.c +++ b/src/common/tortls.c @@ -52,6 +52,7 @@ #include <event2/bufferevent_ssl.h> #include <event2/buffer.h> #include <event2/event.h> +#include "compat_libevent.h" #endif
#define CRYPTO_PRIVATE /* to import prototypes from crypto.h */ @@ -63,7 +64,6 @@ #include "torlog.h" #include "container.h" #include <string.h> -#include "compat_libevent.h"
/* Enable the "v2" TLS handshake. */ @@ -157,11 +157,6 @@ struct tor_tls_t { /** If set, a callback to invoke whenever the client tries to renegotiate * the handshake. */ void (*negotiated_callback)(tor_tls_t *tls, void *arg); - - /** Callback to invoke whenever a client tries to renegotiate more - than once. */ - void (*excess_renegotiations_callback)(evutil_socket_t, short, void *); - /** Argument to pass to negotiated_callback. */ void *callback_arg; }; @@ -1265,6 +1260,17 @@ 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 @@ -1333,20 +1339,6 @@ tor_tls_got_client_hello(tor_tls_t *tls) }
tls->got_renegotiate = 1; - } else if (tls->server_handshake_count > 2) { - /* We got more than one renegotiation requests. The Tor protocol - needs just one renegotiation; more than that probably means - They are trying to DoS us and we have to stop them. We can't - close their connection from in here since it's an OpenSSL - callback, so we set a libevent timer that triggers in the next - event loop and closes the connection. */ - - struct timeval zero_seconds_timer = {0,0}; - - if (tor_event_base_once(tls->excess_renegotiations_callback, - tls->callback_arg, &zero_seconds_timer) < 0) { - log_warn(LD_GENERAL, "Didn't manage to set a renegotiation limiting callback."); - } }
/* Now check the cipher list. */ @@ -1563,20 +1555,16 @@ tor_tls_set_logged_address(tor_tls_t *tls, const char *address) tls->address = tor_strdup(address); }
-/** Set <b>cb</b> to be called with argument <b>arg</b> whenever - * <b>tls</b> next gets a client-side renegotiate in the middle of a - * read. Set <b>cb2</b> to be called with argument <b>arg</b> whenever - * <b>tls</b> gets excess renegotiation requests. Do not invoke this - * function until <em>after</em> initial handshaking is done! +/** Set <b>cb</b> to be called with argument <b>arg</b> whenever <b>tls</b> + * next gets a client-side renegotiate in the middle of a read. Do not + * invoke this function until <em>after</em> initial handshaking is done! */ void -tor_tls_set_renegotiate_callbacks(tor_tls_t *tls, +tor_tls_set_renegotiate_callback(tor_tls_t *tls, void (*cb)(tor_tls_t *, void *arg), - void (*cb2)(evutil_socket_t, short, void *), void *arg) { tls->negotiated_callback = cb; - tls->excess_renegotiations_callback = cb2; tls->callback_arg = arg; tls->got_renegotiate = 0; SSL_set_info_callback(tls->ssl, tor_tls_state_changed_callback); @@ -1636,7 +1624,6 @@ tor_tls_free(tor_tls_t *tls) SSL_free(tls->ssl); tls->ssl = NULL; tls->negotiated_callback = NULL; - tls->excess_renegotiations_callback = NULL; if (tls->context) tor_tls_context_decref(tls->context); tor_free(tls->address); @@ -1665,6 +1652,12 @@ 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) { if (tls->server_handshake_count != 2) { @@ -1719,6 +1712,12 @@ 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; } diff --git a/src/common/tortls.h b/src/common/tortls.h index 5874881..e558df7 100644 --- a/src/common/tortls.h +++ b/src/common/tortls.h @@ -13,7 +13,6 @@
#include "crypto.h" #include "compat.h" -#include "compat_libevent.h"
/* Opaque structure to hold a TLS connection. */ typedef struct tor_tls_t tor_tls_t; @@ -61,9 +60,8 @@ int tor_tls_context_init(int is_public_server, unsigned int key_lifetime); tor_tls_t *tor_tls_new(int sock, int is_server); void tor_tls_set_logged_address(tor_tls_t *tls, const char *address); -void tor_tls_set_renegotiate_callbacks(tor_tls_t *tls, +void tor_tls_set_renegotiate_callback(tor_tls_t *tls, void (*cb)(tor_tls_t *, void *arg), - void (*cb2)(evutil_socket_t, short, void *), void *arg); int tor_tls_is_server(tor_tls_t *tls); void tor_tls_free(tor_tls_t *tls); diff --git a/src/or/connection_or.c b/src/or/connection_or.c index ff696f8..992db9a 100644 --- a/src/or/connection_or.c +++ b/src/or/connection_or.c @@ -1156,20 +1156,6 @@ connection_or_tls_renegotiated_cb(tor_tls_t *tls, void *_conn) } }
-/** Invoked on the server side using a timer from inside - * tor_tls_got_client_hello() when the server receives excess - * renegotiation attempts; probably indicating a DoS. */ -static void -connection_or_close_connection_cb(evutil_socket_t fd, short what, void *_conn) -{ - or_connection_t *conn = _conn; - (void) what; - (void) fd; - - connection_stop_reading(TO_CONN(conn)); - connection_mark_for_close(TO_CONN(conn)); -} - /** Move forward with the tls handshake. If it finishes, hand * <b>conn</b> to connection_tls_finish_handshake(). * @@ -1216,9 +1202,8 @@ connection_tls_continue_handshake(or_connection_t *conn) /* v2/v3 handshake, but not a client. */ log_debug(LD_OR, "Done with initial SSL handshake (server-side). " "Expecting renegotiation or VERSIONS cell"); - tor_tls_set_renegotiate_callbacks(conn->tls, + tor_tls_set_renegotiate_callback(conn->tls, connection_or_tls_renegotiated_cb, - connection_or_close_connection_cb, conn); conn->_base.state = OR_CONN_STATE_TLS_SERVER_RENEGOTIATING; connection_stop_writing(TO_CONN(conn)); @@ -1280,9 +1265,8 @@ connection_or_handle_event_cb(struct bufferevent *bufev, short event, } else if (tor_tls_get_num_server_handshakes(conn->tls) == 1) { /* v2 or v3 handshake, as a server. Only got one handshake, so * wait for the next one. */ - tor_tls_set_renegotiate_callbacks(conn->tls, + tor_tls_set_renegotiate_callback(conn->tls, connection_or_tls_renegotiated_cb, - connection_or_close_connection_cb, conn); conn->_base.state = OR_CONN_STATE_TLS_SERVER_RENEGOTIATING; /* return 0; */