commit b4429307899afd637ae33e8e6a1400f30b57085e Author: Nick Mathewson nickm@torproject.org Date: Tue Dec 11 17:46:12 2012 -0500
Fix serious breakage in connection_handle_write_impl
When we first implemented TLS, we assumed in conneciton_handle_write that a TOR_TLS_WANT_WRITE from flush_buf_tls meant that nothing had been written. But when we moved our buffers to a ring buffer implementation back in 0.1.0.5-rc (!), we broke that invariant: it's possible that some bytes have been written but nothing.
That's bad. It means that if we do a sequence of TLS writes that ends with a WANTWRITE, we don't notice that we flushed any bytes, and we don't (I think) decrement buckets.
Fixes bug 7708; bugfix on 0.1.0.5-rc --- changes/bug7708 | 5 +++++ src/or/connection.c | 15 +++++++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/changes/bug7708 b/changes/bug7708 new file mode 100644 index 0000000..e272adf --- /dev/null +++ b/changes/bug7708 @@ -0,0 +1,5 @@ + o Major bugfixes: + - When a TLS write is partially successful but incomplete, remember + that the flushed part has been flushed, and notice that bytes were + actually written. Reported and fixed pseudonymously. Fixes bug + 7708; bugfix on Tor 0.1.0.5-rc. diff --git a/src/or/connection.c b/src/or/connection.c index eac9c4f..3e6341b 100644 --- a/src/or/connection.c +++ b/src/or/connection.c @@ -3168,6 +3168,7 @@ connection_handle_write_impl(connection_t *conn, int force) ssize_t max_to_write; time_t now = approx_time(); size_t n_read = 0, n_written = 0; + int dont_stop_writing = 0;
tor_assert(!connection_is_listener(conn));
@@ -3220,6 +3221,7 @@ connection_handle_write_impl(connection_t *conn, int force) if (connection_speaks_cells(conn) && conn->state > OR_CONN_STATE_PROXY_HANDSHAKING) { or_connection_t *or_conn = TO_OR_CONN(conn); + size_t initial_size; if (conn->state == OR_CONN_STATE_TLS_HANDSHAKING || conn->state == OR_CONN_STATE_TLS_CLIENT_RENEGOTIATING) { connection_stop_writing(conn); @@ -3235,6 +3237,7 @@ connection_handle_write_impl(connection_t *conn, int force) }
/* else open, or closing */ + initial_size = buf_datalen(conn->outbuf); result = flush_buf_tls(or_conn->tls, conn->outbuf, max_to_write, &conn->outbuf_flushlen);
@@ -3257,7 +3260,8 @@ connection_handle_write_impl(connection_t *conn, int force) case TOR_TLS_WANTWRITE: log_debug(LD_NET,"wanted write."); /* we're already writing */ - return 0; + dont_stop_writing = 1; + break; case TOR_TLS_WANTREAD: /* Make sure to avoid a loop if the receive buckets are empty. */ log_debug(LD_NET,"wanted read."); @@ -3279,6 +3283,12 @@ connection_handle_write_impl(connection_t *conn, int force) tor_tls_get_n_raw_bytes(or_conn->tls, &n_read, &n_written); log_debug(LD_GENERAL, "After TLS write of %d: %ld read, %ld written", result, (long)n_read, (long)n_written); + /* So we notice bytes were written even on error */ + /* XXXX024 This cast is safe since we can never write INT_MAX bytes in a + * single set of TLS operations. But it looks kinda ugly. If we refactor + * the *_buf_tls functions, we should make them return ssize_t or size_t + * or something. */ + result = (int)(initial_size-buf_datalen(conn->outbuf)); } else { CONN_LOG_PROTECT(conn, result = flush_buf(conn->s, conn->outbuf, @@ -3313,7 +3323,8 @@ connection_handle_write_impl(connection_t *conn, int force) connection_mark_for_close(conn); }
- if (!connection_wants_to_flush(conn)) { /* it's done flushing */ + if (!connection_wants_to_flush(conn) && + !dont_stop_writing) { /* it's done flushing */ if (connection_finished_flushing(conn) < 0) { /* already marked */ return -1;