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@@ -52,7 +52,6 @@
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#include <event2/bufferevent_ssl.h>
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#include <event2/buffer.h>
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#include <event2/event.h>
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-#include "compat_libevent.h"
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#endif
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#define CRYPTO_PRIVATE /* to import prototypes from crypto.h */
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@@ -64,6 +63,7 @@
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#include "torlog.h"
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#include "container.h"
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#include <string.h>
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+#include "compat_libevent.h"
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/* Enable the "v2" TLS handshake.
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*/
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@@ -157,6 +157,11 @@ struct tor_tls_t {
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/** If set, a callback to invoke whenever the client tries to renegotiate
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* the handshake. */
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void (*negotiated_callback)(tor_tls_t *tls, void *arg);
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+
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+ /** Callback to invoke whenever a client tries to renegotiate more
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+ than once. */
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+ void (*excess_renegotiations_callback)(evutil_socket_t, short, void *);
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+
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/** Argument to pass to negotiated_callback. */
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void *callback_arg;
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};
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@@ -1228,17 +1233,6 @@ tor_tls_context_new(crypto_pk_env_t *identity, unsigned int key_lifetime)
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return NULL;
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}
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-/** Return true if the <b>tls</b> object has completed more
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- * renegotiations than needed for the Tor protocol. */
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-static INLINE int
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-tor_tls_got_excess_renegotiations(tor_tls_t *tls)
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-{
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- /** The Tor v2 server handshake needs a single renegotiation after
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- the initial SSL handshake. This means that if we ever see more
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- than 2 handshakes, we raise the flag. */
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- return (tls->server_handshake_count > 2) ? 1 : 0;
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-}
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-
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#ifdef V2_HANDSHAKE_SERVER
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/** Return true iff the cipher list suggested by the client for <b>ssl</b> is
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* a list that indicates that the client knows how to do the v2 TLS connection
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@@ -1307,6 +1301,20 @@ tor_tls_got_client_hello(tor_tls_t *tls)
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}
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tls->got_renegotiate = 1;
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+ } else if (tls->server_handshake_count > 2) {
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+ /* We got more than one renegotiation requests. The Tor protocol
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+ needs just one renegotiation; more than that probably means
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+ They are trying to DoS us and we have to stop them. We can't
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+ close their connection from in here since it's an OpenSSL
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+ callback, so we set a libevent timer that triggers in the next
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+ event loop and closes the connection. */
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+
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+ struct timeval zero_seconds_timer = {0,0};
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+
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+ if (tor_event_base_once(tls->excess_renegotiations_callback,
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+ tls->callback_arg, &zero_seconds_timer) < 0) {
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+ log_warn(LD_GENERAL, "Didn't manage to set a renegotiation limiting callback.");
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+ }
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}
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/* Now check the cipher list. */
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@@ -1523,16 +1531,20 @@ tor_tls_set_logged_address(tor_tls_t *tls, const char *address)
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tls->address = tor_strdup(address);
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}
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-/** Set <b>cb</b> to be called with argument <b>arg</b> whenever <b>tls</b>
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- * next gets a client-side renegotiate in the middle of a read. Do not
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- * invoke this function until <em>after</em> initial handshaking is done!
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+/** Set <b>cb</b> to be called with argument <b>arg</b> whenever
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+ * <b>tls</b> next gets a client-side renegotiate in the middle of a
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+ * read. Set <b>cb2</b> to be called with argument <b>arg</b> whenever
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+ * <b>tls</b> gets excess renegotiation requests. Do not invoke this
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+ * function until <em>after</em> initial handshaking is done!
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*/
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void
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-tor_tls_set_renegotiate_callback(tor_tls_t *tls,
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+tor_tls_set_renegotiate_callbacks(tor_tls_t *tls,
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void (*cb)(tor_tls_t *, void *arg),
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+ void (*cb2)(evutil_socket_t, short, void *),
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void *arg)
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{
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tls->negotiated_callback = cb;
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+ tls->excess_renegotiations_callback = cb2;
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tls->callback_arg = arg;
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tls->got_renegotiate = 0;
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SSL_set_info_callback(tls->ssl, tor_tls_state_changed_callback);
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@@ -1592,6 +1604,7 @@ tor_tls_free(tor_tls_t *tls)
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SSL_free(tls->ssl);
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tls->ssl = NULL;
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tls->negotiated_callback = NULL;
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+ tls->excess_renegotiations_callback = NULL;
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if (tls->context)
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tor_tls_context_decref(tls->context);
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tor_free(tls->address);
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@@ -1620,12 +1633,6 @@ tor_tls_read(tor_tls_t *tls, char *cp, size_t len)
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err = tor_tls_get_error(tls, r, CATCH_ZERO, "reading", LOG_DEBUG, LD_NET);
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- if (tor_tls_got_excess_renegotiations(tls)) {
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- log_info(LD_NET, "Detected excess renegotiation from %s!", ADDR(tls));
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-
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- return TOR_TLS_ERROR_MISC;
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- }
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-
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#ifdef V2_HANDSHAKE_SERVER
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if (tls->got_renegotiate) {
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if (tls->server_handshake_count != 2) {
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@@ -1680,12 +1687,6 @@ tor_tls_write(tor_tls_t *tls, const char *cp, size_t n)
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r = SSL_write(tls->ssl, cp, (int)n);
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err = tor_tls_get_error(tls, r, 0, "writing", LOG_INFO, LD_NET);
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- if (tor_tls_got_excess_renegotiations(tls)) {
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- log_info(LD_NET, "Detected excess renegotiation from %s!", ADDR(tls));
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-
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- return TOR_TLS_ERROR_MISC;
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- }
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-
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if (err == TOR_TLS_DONE) {
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return r;
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}
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