key re-exchange problem?

Andre Charbonneau <[email protected]>
Newsgroups gmane.comp.java.sshtools.user
Message-ID <[email protected]> 
Hi,
I have a problem with sshtools where the connection is being closed and 
I get a protocol error.  According to the debug output, it looks like 
this occurs during key re-exchange.

Here is the debug output:

    (...)
    DEBUG - Received 16384 bytes of data for channel id 2
    DEBUG - SshMsgKexInit:
    Supported Kex [diffie-hellman-group1-sha1]
    Supported Public Keys [ssh-dss, ssh-rsa]
    Supported Encryption Client->Server [blowfish-cbc, 3des-cbc]
    Supported Encryption Server->Client [blowfish-cbc, 3des-cbc]
    Supported Mac Client->Server [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Mac Server->Client [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Compression Client->Server [none]
    Supported Compression Server->Client [none]
    Supported Languages Client->Server []
    Supported Languages Server->Client []
    First Kex Packet Follows [FALSE]
    INFO - Sending SSH_MSG_KEX_INIT
    DEBUG - Received SSH_MSG_CHANNEL_DATA
    DEBUG - Received 16384 bytes of data for channel id 2
    DEBUG - SshMsgKexInit:
    Supported Kex [diffie-hellman-group1-sha1]
    Supported Public Keys [ssh-dss, ssh-rsa]
    Supported Encryption Client->Server [blowfish-cbc, 3des-cbc]
    Supported Encryption Server->Client [blowfish-cbc, 3des-cbc]
    Supported Mac Client->Server [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Mac Server->Client [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Compression Client->Server [none]
    Supported Compression Server->Client [none]
    Supported Languages Client->Server []
    Supported Languages Server->Client []
    First Kex Packet Follows [FALSE]
    INFO - Sending SSH_MSG_KEX_INIT
    DEBUG - Received SSH_MSG_CHANNEL_DATA
    DEBUG - Received 16384 bytes of data for channel id 2
    DEBUG - SshMsgKexInit:
    Supported Kex [diffie-hellman-group1-sha1]
    Supported Public Keys [ssh-dss, ssh-rsa]
    Supported Encryption Client->Server [blowfish-cbc, 3des-cbc]
    Supported Encryption Server->Client [blowfish-cbc, 3des-cbc]
    Supported Mac Client->Server [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Mac Server->Client [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Compression Client->Server [none]
    Supported Compression Server->Client [none]
    Supported Languages Client->Server []
    Supported Languages Server->Client []
    First Kex Packet Follows [FALSE]
    INFO - Sending SSH_MSG_KEX_INIT
    DEBUG - Received SSH_MSG_CHANNEL_DATA
    DEBUG - Received 16384 bytes of data for channel id 2
    DEBUG - SshMsgKexInit:
    Supported Kex [diffie-hellman-group1-sha1]
    Supported Public Keys [ssh-dss, ssh-rsa]
    Supported Encryption Client->Server [blowfish-cbc, 3des-cbc]
    Supported Encryption Server->Client [blowfish-cbc, 3des-cbc]
    Supported Mac Client->Server [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Mac Server->Client [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    Supported Compression Client->Server [none]
    Supported Compression Server->Client [none]
    Supported Languages Client->Server []
    Supported Languages Server->Client []
    First Kex Packet Follows [FALSE]
    INFO - Sending SSH_MSG_KEX_INIT
    DEBUG - Received SSH_MSG_KEX_INIT
    DEBUG - SshMsgKexInit:
    Supported Kex [gss-group1-sha1-dZuIebMjgUqaxvbF7hDbAw==,
    gss-group1-sha1-N3+k7/4wGxHyuP8Yxi4RhA==,
    diffie-hellman-group-exchange-sha1, diffie-hellman-group14-sha1,
    diffie-hellman-group1-sha1]
    Supported Public Keys [ssh-rsa, ssh-dss]
    Supported Encryption Client->Server [aes128-cbc, 3des-cbc,
    blowfish-cbc, cast128-cbc, arcfour, aes192-cbc, aes256-cbc,
    [email protected], aes128-ctr, aes192-ctr, aes256-ctr]
    Supported Encryption Server->Client [aes128-cbc, 3des-cbc,
    blowfish-cbc, cast128-cbc, arcfour, aes192-cbc, aes256-cbc,
    [email protected], aes128-ctr, aes192-ctr, aes256-ctr]
    Supported Mac Client->Server [hmac-md5, hmac-sha1, hmac-ripemd160,
    [email protected], hmac-sha1-96, hmac-md5-96]
    Supported Mac Server->Client [hmac-md5, hmac-sha1, hmac-ripemd160,
    [email protected], hmac-sha1-96, hmac-md5-96]
    Supported Compression Client->Server [none, zlib]
    Supported Compression Server->Client [none, zlib]
    Supported Languages Client->Server []
    Supported Languages Server->Client []
    First Kex Packet Follows [FALSE]
    DEBUG - Determine AlgorithmKEXD
    DEBUG - Client Algorithms: [blowfish-cbc, 3des-cbc]
    DEBUG - Server Algorithms: [aes128-cbc, 3des-cbc, blowfish-cbc,
    cast128-cbc, arcfour, aes192-cbc, aes256-cbc,
    [email protected], aes128-ctr, aes192-ctr, aes256-ctr]
    DEBUG - Returning blowfish-cbc
    DEBUG - Determine Algorithm
    DEBUG - Client Algorithms: [blowfish-cbc, 3des-cbc]
    DEBUG - Server Algorithms: [aes128-cbc, 3des-cbc, blowfish-cbc,
    cast128-cbc, arcfour, aes192-cbc, aes256-cbc,
    [email protected], aes128-ctr, aes192-ctr, aes256-ctr]
    DEBUG - Returning blowfish-cbc
    DEBUG - Determine Algorithm
    DEBUG - Client Algorithms: [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    DEBUG - Server Algorithms: [hmac-md5, hmac-sha1, hmac-ripemd160,
    [email protected], hmac-sha1-96, hmac-md5-96]
    DEBUG - Returning hmac-sha1
    DEBUG - Determine Algorithm
    DEBUG - Client Algorithms: [hmac-sha1, hmac-md5-96, hmac-md5,
    hmac-sha1-96]
    DEBUG - Server Algorithms: [hmac-md5, hmac-sha1, hmac-ripemd160,
    [email protected], hmac-sha1-96, hmac-md5-96]
    DEBUG - Returning hmac-sha1
    DEBUG - Determine Algorithm
    DEBUG - Client Algorithms: [none]
    DEBUG - Server Algorithms: [none, zlib]
    DEBUG - Returning none
    DEBUG - Determine Algorithm
    DEBUG - Client Algorithms: [none]
    DEBUG - Server Algorithms: [none, zlib]
    DEBUG - Returning none
    INFO - Starting key exchange
    DEBUG - Determine Algorithm
    DEBUG - Client Algorithms: [diffie-hellman-group1-sha1]
    DEBUG - Server Algorithms:
    [gss-group1-sha1-dZuIebMjgUqaxvbF7hDbAw==,
    gss-group1-sha1-N3+k7/4wGxHyuP8Yxi4RhA==,
    diffie-hellman-group-exchange-sha1, diffie-hellman-group14-sha1,
    diffie-hellman-group1-sha1]
    DEBUG - Returning diffie-hellman-group1-sha1
    DEBUG - Key exchange algorithm: diffie-hellman-group1-sha1
    INFO - Starting client side key exchange.
    INFO - Sending SSH_MSG_KEXDH_INIT
    INFO - The remote computer disconnected: Protocol error: expected
    packet type 30, got 20
    INFO - The Transport Protocol has been stopped


So according to the debug output, the server is expecting 
SSH_MSG_KEXDH_INIT (30), but got SSH_MSG_KEX_INIT (20) instead.  If I 
look at the debug output above, it looks like the client sent more than 
one SSH_MSG_KEX_INIT message, which goes against the rfc4253 
recommendations (section 7.1), which says that once a SSH_MSG_KEX_INIT 
message is sent, then more SSH_MSG_KEY_INIT *MUST NOT* be sent until it 
has sent a SSH_MSG_NEWKEYS message.  (Maybe somehow the extra 
(redundant) SSH_MSG_KEX_INIT messages get queued and the server received 
one of those redundant  SSH_MSG_KEX_INIT instead of the 
SSH_MSG_KEXDH_INIT it is suppose to get.)

Could this be what is causing the protocol error?

Any help/advice with this will be much appreciated.


Regards,
    Andre

-- 
Andre Charbonneau

100 Sussex Drive, Rm 2025
Research Computing Support, IMSB
National Research Council Canada
Ottawa, ON, Canada K1A 0R6
613-993-3129  Fax: 613-993-3127     



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