Corrupted MAC problem on PSOS platform

[Jim Fan]

Hi Group,
I am porting openSSH to an embedded platform running pSOS. I am able
to setup a connection with the server but after I disconnect and
reconnect, I always get the following error message and client won't
establish connection with the server.

<First connection..............................>
debug: Enabling compatibility mode for protocol 2.0
debug: SSH2_MSG_KEXINIT sent
debug: kex: client->server aes256-cbc hmac-sha1 none
debug: kex: server->client aes256-cbc hmac-sha1 none
debug: SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received
debug: SSH2_MSG_KEX_DH_GEX_GROUP sent
debug: expecting SSH2_MSG_KEX_DH_GEX_INIT
debug: SSH2_MSG_KEX_DH_GEX_REPLY sent
debug: kex_derive_keys........................
debug: newkeys[1]=0xfd4868
debug: SSH2_MSG_NEWKEYS sent
debug: expecting SSH2_MSG_NEWKEYS
debug: newkeys[0]=0xfd4748
debug: SSH2_MSG_NEWKEYS received
debug: userauth-request for user terter service ssh-connection method none
debug: attempt 0 failures 0
debug: userauth-request for user terter service ssh-connection method
keyboard-interactive
debug: attempt 1 failures 1
debug: keyboard-interactive devs
debug: auth2_challenge: user=terter devs=
debug: kbdint_alloc: devices ''
debug: userauth-request for user terter service ssh-connection method password
debug: attempt 2 failures 2
Accepted password for terter from 172.23.1.174 port 1331 ssh2
Accepted password for terter from 172.23.1.174 port 1331 ssh2

debug: Entering interactive session for SSH2.
debug: server_init_dispatch_20
debug: server_input_channel_open: ctype session rchan 256 win 16384 max 16384
debug: input_session_request
debug: channel 0: new [server-session]
debug: session_new: init
debug: session_new: session 0
debug: session_open: channel 0
debug: session_open: session 0: link with channel 0
debug: server_input_channel_open: confirm session
debug: server_input_channel_req: channel 0 request pty-req reply 1
debug: session_by_channel: session 0 channel 0
debug: session_input_channel_req: session 0 req pty-req
debug: Allocating pty.
debug: session_pty_req: session 0 alloc
debug: server_input_channel_req: channel 0 request shell reply 1
debug: session_by_channel: session 0 channel 0
debug: session_input_channel_req: session 0 req shell
Secure shell client connected
Secure shell client disconnected
debug: channel 0: free: server-session, nchannels 1
debug: session_close: session 0 pid 0
000110.999|SSHD |3|01|Closing connection to 172.23.1.174

<Connection 2.............>
debug: Enabling compatibility mode for protocol 2.0
debug: SSH2_MSG_KEXINIT sent
debug: kex: client->server aes256-cbc hmac-sha1 none
debug: kex: server->client aes256-cbc hmac-sha1 none
debug: SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received
debug: SSH2_MSG_KEX_DH_GEX_GROUP sent
debug: expecting SSH2_MSG_KEX_DH_GEX_INIT
debug: SSH2_MSG_KEX_DH_GEX_REPLY sent
debug: kex_derive_keys........................
debug: newkeys[1]=0x1024898
debug: SSH2_MSG_NEWKEYS sent
debug: expecting SSH2_MSG_NEWKEYS
debug: newkeys[0]=0x1024778
debug: SSH2_MSG_NEWKEYS received

<following debug messages were added by me>
macbuf------------------------------20
5d38305c8b399a79c644d9e021be0d2247d1124
input-------------------------------
3b50 7e58 d759 5dfc dbe5 6c3f 46df 7297
a0cf d748
Disconnecting: Corrupted MAC on input.
Disconnecting: Corrupted MAC on input.


I checked key exchanges in both connections and they all looked ok.
Any ideas why MAC check would fail on second connection attempt?

Best Regards,
Jim