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Commit ffa7b159 authored by Nick Mathewson's avatar Nick Mathewson 🥄

Deliberately close OR connections if proxies leave extra data

We already did this, but we did it by accident, which is pretty
risky: if we hadn't, then our code would have treated extra data in
the inbuf as having been transmitted as TLS-authenticated data.

Closes ticket 40017; Found by opara.
parent e2d3c9c5
o Minor features (protocol, proxy support, defense in depth):
- Respond more deliberately to misbehaving proxies that leave leftover
data on their connections, so as to be even less likely as to allow
them to pass their data off as having come from a relay.
Closes ticket 40017.
......@@ -566,11 +566,6 @@ connection_or_reached_eof(or_connection_t *conn)
connection_or_process_inbuf(or_connection_t *conn)
/** Don't let the inbuf of a nonopen OR connection grow beyond this many
* bytes: it's either a broken client, a non-Tor client, or a DOS
* attempt. */
int ret = 0;
......@@ -581,6 +576,15 @@ connection_or_process_inbuf(or_connection_t *conn)
/* start TLS after handshake completion, or deal with error */
if (ret == 1) {
tor_assert(TO_CONN(conn)->proxy_state == PROXY_CONNECTED);
if (buf_datalen(conn->base_.inbuf) != 0) {
log_fn(LOG_PROTOCOL_WARN, LD_NET, "Found leftover (%d bytes) "
"when transitioning from PROXY_HANDSHAKING state on %s: "
connection_or_close_for_error(conn, 0);
return -1;
if (connection_tls_start_handshake(conn, 0) < 0)
ret = -1;
/* Touch the channel's active timestamp if there is one */
......@@ -601,14 +605,12 @@ connection_or_process_inbuf(or_connection_t *conn)
break; /* don't do anything */
/* This check was necessary with 0.2.2, when the TLS_SERVER_RENEGOTIATING
* check would otherwise just let data accumulate. It serves no purpose
* in 0.2.3.
* XXXX Remove this check once we verify that the above paragraph is
* 100% true. */
if (buf_datalen(conn->base_.inbuf) > MAX_OR_INBUF_WHEN_NONOPEN) {
log_fn(LOG_PROTOCOL_WARN, LD_NET, "Accumulated too much data (%d bytes) "
/* This check makes sure that we don't have any data on the inbuf if we're
* doing our TLS handshake: if we did, they were probably put there by a
* SOCKS proxy trying to trick us into accepting unauthenticated data.
if (buf_datalen(conn->base_.inbuf) != 0) {
log_fn(LOG_PROTOCOL_WARN, LD_NET, "Accumulated data (%d bytes) "
"on non-open %s; closing.",
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