Subject: [libssh2] Stack Overflow

[libssh2] Stack Overflow

From: Cary Fitzhugh <>
Date: Fri, 28 Mar 2008 13:37:22 -0400

Hello all,


We're looking at this bug now - but maybe some of you might have an idea
as to what is going on.

We have a system that uses libssh2 for all kinds of file transfers, and
everything seems to work fine for files less than a GB or so.

When we try to transfer a file of > 1GB it will crash in the middle of
the file transfer.

I finally got it into visual studio and got the stack trace. Visual
Studio says that the issue is a stack overflow.

The back trace goes as far back as VS will display (and still doesn't
get to the user-level code).


It looks like it's spinning round and round with: -- why would it need
to reexchange the key in the middle of a transfer?

The transfer has been running for about 27 minutes at this point. It is
very consistent as well - every time the file tries to go up it seems to
go bad at about the same place in the file.



libssh2_packet_read( line 528, transport.c )

  calling: full_packet( session , encypted (true) ) -- the session
seems valid, it does have a null server host key (but a server host key
len of 151) ??


full_packet (line 231 transport.c)

  calling: libssh2_packet_add( session, payload, len = 457, state = 0)


libssh2_packet_add (line 921 packet.c )

  calling: libssh2_kex_exhange( session, 1, NB_state_sent2 )


libssh2_kex_exhange (1764 kex.c)

  calling: session->kex->echange_keys (session, NB_created)


kex_exchange_diffie_hellman_group_14_sha1_key_exchange (line 795 kex.c)

  calling: libssh2_kex_method_diffie_hellman_groupGP_sha1_key_exchange


libssh2_kex_method_diffie_hellman_groupGP_sha1_key_exchange (191 kex.c)

  calling: libssh2_packet_require_ex


libssh2_packet_require_ex (line 1088 packet.c)

  calling libssh2_packet_read (and around we go).


We're looking at it - but figured I'd let you all know, maybe you have
some ideas.



Cary FitzHugh



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Received on 2008-03-28