diff options
author | Alan Dunn <amdunn@gmail.com> | 2014-02-06 08:12:46 -0600 |
---|---|---|
committer | Andreas Schneider <asn@cryptomilk.org> | 2014-02-06 19:41:00 +0100 |
commit | bb0023b7c703a932b59756b728c95ca7e28e58c4 (patch) | |
tree | 0bb52537ce4096ff42f743a9564744691660b43f /src/packet1.c | |
parent | 398e8d50b54c6947b9c6e494fc6adc17e96521be (diff) | |
download | libssh-bb0023b7c703a932b59756b728c95ca7e28e58c4.tar.gz libssh-bb0023b7c703a932b59756b728c95ca7e28e58c4.tar.xz libssh-bb0023b7c703a932b59756b728c95ca7e28e58c4.zip |
packet: Do not decrypt zero length rest of buffer
If we receive a packet of length exactly blocksize, then
packet_decrypt gets called on a buffer of size 0. The check at the
beginning of packet_decrypt indicates that the function should be
called on buffers of at least one blocksize, though the check allows
through zero length. As is packet_decrypt can return -1 when len is 0
because malloc can return NULL in this case: according to the ISO C
standard, malloc is free to return NULL or a pointer that can be freed
when size == 0, and uclibc by default will return NULL here (in
"non-glibc-compatible" mode). The net result is that when using
uclibc connections with libssh can anomalously fail.
Alternatively, packet_decrypt (and probably packet_encrypt for
consistency) could be made to always succeed on len == 0 without
depending on the behavior of malloc.
Thanks to Josh Berlin for bringing conneciton failures with uclibc to
my attention.
Signed-off-by: Alan Dunn <amdunn@gmail.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Diffstat (limited to 'src/packet1.c')
-rw-r--r-- | src/packet1.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/src/packet1.c b/src/packet1.c index ec72f166..3284f17a 100644 --- a/src/packet1.c +++ b/src/packet1.c @@ -106,7 +106,7 @@ int ssh_packet_socket_callback1(const void *data, size_t receivedlen, void *user size_t processed=0; uint32_t padding; uint32_t crc; - uint32_t len; + uint32_t len, buffer_len; ssh_session session=(ssh_session)user; switch (session->packet_state){ @@ -168,11 +168,16 @@ int ssh_packet_socket_callback1(const void *data, size_t receivedlen, void *user * We decrypt everything, missing the lenght part (which was * previously read, unencrypted, and is not part of the buffer */ - if (packet_decrypt(session, - ssh_buffer_get_begin(session->in_buffer), - ssh_buffer_get_len(session->in_buffer)) < 0) { - ssh_set_error(session, SSH_FATAL, "Packet decrypt error"); - goto error; + buffer_len = ssh_buffer_get_len(session->in_buffer); + if (buffer_len > 0) { + int rc; + rc = packet_decrypt(session, + ssh_buffer_get_begin(session->in_buffer), + buffer_len); + if (rc < 0) { + ssh_set_error(session, SSH_FATAL, "Packet decrypt error"); + goto error; + } } } #ifdef DEBUG_CRYPTO @@ -300,6 +305,8 @@ int packet_send1(ssh_session session) { ssh_buffer_get_len(session->out_buffer)); #endif + /* session->out_buffer should have more than sizeof(uint32_t) bytes + in it as required for packet_encrypt */ packet_encrypt(session, (unsigned char *)ssh_buffer_get_begin(session->out_buffer) + sizeof(uint32_t), ssh_buffer_get_len(session->out_buffer) - sizeof(uint32_t)); |