HMAC error - help pls

["jeetu.golani@xxxxxxxxx" <jeetu.golani@xxxxxxxxx>]

Hi guys,

In continuation with my efforts to put together a libssh based server,
I have had significant success and can say it is very impressive to
see the effort you guys have put in the libssh library, thank you :)

I could sincerely use some help though. All in all my server is
behaving much more robust than it ever has. I have been testing with
multiple X client applications being forwarded simultaneously and all
in all it runs well. I had some previous issues I had mailed this list
about (subject: multithreaded server issues) but an init of the buffer
seems to have helped.

I have noticed some behaviour I do not understand. Below is what the
libssh log says when set to SSH_LOG_PACKET

With multiple applications, after extensive use of the applications
(for e.g. xeyes and xclock running) I have noticed that after sometime
the applications are unable to refresh their window - there is no
crash most of these times and if left alone maybe clock may eventually
refresh part of the window etc. xeyes stops showing it's eyes moving
around but still seems to be running - ssh client connected seems to
show some activity too.

The libssh log seems to suggest that there is packet corruption at
this point. Two things stand out from the below log:

I]

[3] Decrypting 16 bytes
[3] Packet size decrypted: 2754678753 (0xa4310fe1)
[1] Error : read_packet(): Packet len too high(2754678753 a4310fe1)

II]
[3] Decrypting 96 bytes
[1] Error : HMAC error

Pls note this log is an excerpt of a long log taken once the strange
behaviour has manifested.

What is a HMAC error? can someone pls shed light on what could be
causing the above?

Thanks,
Jeetu


[3] Type 94
[3] Dispatching handler for packet type 94
[2] Channel receiving 32 bytes data in 0 (local win=72640 remote win=2095160)
[1] placing 32 bytes into channel buffer (stderr=0)
[2] Channel windows are now (local win=72608 remote win=2095160)
[3] Decrypting 16 bytes
[3] Packet size decrypted: 60 (0x3c)
[3] Read a 60 bytes packet
[3] Decrypting 48 bytes
[3] 18 bytes padding, 59 bytes left in buffer
[3] After padding, 41 bytes left in buffer
[3] Final size 41
[3] Type 94
[3] Dispatching handler for packet type 94
[2] Channel receiving 32 bytes data in 0 (local win=72608 remote win=2095160)
[1] placing 32 bytes into channel buffer (stderr=0)
[2] Channel windows are now (local win=72576 remote win=2095160)
[3] Decrypting 16 bytes
[3] Decrypting 16 bytes
[3] Packet size decrypted: 2754678753 (0xa4310fe1)
[1] Error : read_packet(): Packet len too high(2754678753 a4310fe1)
[3] Packet size decrypted: 92 (0x5c)
[3] Read a 92 bytes packet
[3] Decrypting 96 bytes
[1] Error : HMAC error
[3] Writing on the wire a packet having 1993 bytes before
[3] 1993 bytes after comp + 18 padding bytes = 2012 bytes packet
[3] Encrypting packet with seq num: 36518, len: 2016
[3] Enabling POLLOUT for socket
[1] channel_write wrote 1984 bytes
[3] Writing on the wire a packet having 17 bytes before
[3] 17 bytes after comp + 10 padding bytes = 28 bytes packet
[3] Encrypting packet with seq num: 36519, len: 32
[3] Enabling POLLOUT for socket
[1] channel_write wrote 8 bytes
[3] Read a 92 bytes packet
[3] Decrypting 176 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 256 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 336 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 416 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 496 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 576 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 656 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 736 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 816 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 896 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 976 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 1056 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 1136 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 1216 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 1296 bytes
[1] Error : HMAC error
[3] Read a 92 bytes packet
[3] Decrypting 1376 bytes
[1] Error : HMAC error
[3] Writing on the wire a packet having 8605 bytes before
[3] 8605 bytes after comp + 14 padding bytes = 8620 bytes packet
[3] Encrypting packet with seq num: 885, len: 8624
[3] Enabling POLLOUT for socket
[1] channel_write wrote 8596 bytes
[3] Writing on the wire a packet having 8605 bytes before
[3] 8605 bytes after comp + 14 padding bytes = 8620 bytes packet
[3] Encrypting packet with seq num: 886, len: 8624
[3] Enabling POLLOUT for socket
[1] channel_write wrote 8596 bytes
[3] Decrypting 16 bytes
[3] Packet size decrypted: 3661937450 (0xda44bb2a)
[1] Error : read_packet(): Packet len too high(3661937450 da44bb2a)