Re: HMAC error - help pls

[Aris Adamantiadis <aris@xxxxxxxxxxxx>]

Hi Jeetu,

I did not have much time to read your email completely, but it seems in
first impression that server/client is sending garbage. Could you attach
the first hundreds lines of debugging output, especially the key exchange ?
Also, do you have an estimation of the number of bytes that have been
transmitted before the failure ? (i.e. does it approach gigabytes ?)

Thanks,

Aris

Le 7/06/11 12:00, jeetu.golani@xxxxxxxxx a écrit :
> 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)
>