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transport_send: Finish in-progress key exchange before sending data

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_libssh2_channel_write() first reads outstanding packets before writing
new data. If it reads a key exchange request, it will immediately start
key re-exchange, which will require sending a response. If the output
socket is full, this will result in a return from
_libssh2_transport_read() of LIBSSH2_ERROR_EAGAIN. In order not to block
a write because there is no data to read, this error is explicitly
ignored and the code continues marshalling a packet for sending. When it
is sent, the remote end immediately drops the connection because it was
expecting a continuation of the key exchange, but got a data packet.

This change adds the same check for key exchange to
_libssh2_transport_send() that is in _libssh2_transport_read(). This
ensures that key exchange is completed before any data packet is sent.
This commit is contained in:
Matthew Booth
2012-03-16 16:29:00 +01:00
committed by Daniel Stenberg
parent fed0759720
commit cc4f9d5679
1 changed files with 19 additions and 1 deletions
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20
src/transport.c
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@@ -296,7 +296,7 @@ int _libssh2_transport_read(LIBSSH2_SESSION * session)
* is done!
*/
_libssh2_debug(session, LIBSSH2_TRACE_TRANS, "Redirecting into the"
" key re-exchange");
" key re-exchange from _libssh2_transport_read");
rc = _libssh2_kex_exchange(session, 1, &session->startup_key_state);
if (rc)
return rc;
@@ -687,6 +687,24 @@ int _libssh2_transport_send(LIBSSH2_SESSION *session,
const unsigned char *orgdata = data;
size_t orgdata_len = data_len;
/*
* If the last read operation was interrupted in the middle of a key
* exchange, we must complete that key exchange before continuing to write
* further data.
*
* See the similar block in _libssh2_transport_read for more details.
*/
if (session->state & LIBSSH2_STATE_EXCHANGING_KEYS &&
!(session->state & LIBSSH2_STATE_KEX_ACTIVE)) {
/* Don't write any new packets if we're still in the middle of a key
* exchange. */
_libssh2_debug(session, LIBSSH2_TRACE_TRANS, "Redirecting into the"
" key re-exchange from _libssh2_transport_send");
rc = _libssh2_kex_exchange(session, 1, &session->startup_key_state);
if (rc)
return rc;
}
debugdump(session, "libssh2_transport_write plain", data, data_len);
if(data2)
debugdump(session, "libssh2_transport_write plain2", data2, data2_len);