In 'ssh_bind_listen', move setting of 'sshbind->bindfd' to only happen after
the listen call: otherwise 'bindfd' can be set to a bogus descriptor for the
case that listen fails.
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
When accepting a new connection, a forking server based on libssh forks
and the child process handles the request. The RAND_bytes() function of
openssl doesn't reset its state after the fork, but simply adds the
current process id (getpid) to the PRNG state, which is not guaranteed
to be unique.
This can cause several children to end up with same PRNG state which is
a security issue.
Make sure to explicitly set key pointers to NULL following the use
of 'ssh_key_free' throughout bind.c.
Before this change, a double free can happen via 'ssh_bind_free'
as in this example callpath:
// create an ssh_bind
ssh_bind b = ssh_bind_new();
// provide a path to a wrong key-type
ssh_bind_options_set(b, SSH_BIND_OPTIONS_DSAKEY, path_to_rsa_key);
// initialize set key-type
ssh_bind_listen(b);
-> error path "The DSA host key has the wrong type: %d",
ssh_key_free(sshbind->dsa)
-> ssh_key_clean(key) // OK
-> SAFE_FREE(key) // OK, but, sshbind->dsa is *not* set to NULL
// ssh_bind_listen failed, so clean up ssh_bind
ssh_bind_free(b);
-> ssh_key_free(sshbind->dsa) // double-free here
To fix, set pointers to NULL that have been free'd with 'ssh_key_free'.
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This function is pretty much obsolete on most platforms. The standard
errno should be used. If it is not enough on Windows we should use
WSAGetLastError() in future.
