tests: fix compilation on OSX (libargp detection)
Added known host test cases
known_hosts: add ssh_knownhosts_algorithms()

Goal of that function is to test the preferred key exchange methods
based on what's available in the known_hosts file
knownhosts: add test case for bug #138
Knownhosts: implement hostkey with knownhosts heuristic
server: allow custom server banners (bug #83)
Kex: fix coverity warning + edge case
build: fix cmake bug introduced yesterday

Compilation failed on OSX because of the missing OR OSX
build: remove OSX deprecated warnings for openssl
Make function ssh_channel_accept() nonblocking if timeout is 0.

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
client: Fix EOF session error reporting.

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
src: Define MAX_BUF_SIZE globally and use it.

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
src: Fix argument order in ssh_channel_pty_window_change_callback

So that it would match ssh_channel_pty_request_callback as well as the documentation

Signed-off-by: Audrius Butkevicius <audrius.butkevicius@gmail.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
doc: Document expected return value of channel data callback

Signed-off-by: Audrius Butkevicius <audrius.butkevicius@gmail.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
doc: correct ssh_channel_read_timeout units

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
socket: fix read of non-connected socket

Ensure to check whether the socket at hand is indeed still connected
throughout POLLIN processing in ssh_socket_pollcallback.

Before this change, the POLLIN block in ssh_socket_pollcallback is
predicated against the condition (s->state == SSH_SOCKET_CONNECTED).
Once entered, data from the socket is consumed through the data
callback in this loop:

  do {
    r = s->callbacks->data(buffer_get_rest(s->in_buffer),
                           buffer_get_rest_len(s->in_buffer),
                           s->callbacks->userdata);
    buffer_pass_bytes(s->in_buffer,r);
  } while (r > 0);

However, it is possible for the socket data callback to change the
state of the socket (closing it, for example).  Fix the loop to only
continue so long as the socket remains connected: this also entails
setting the ssh_socket state to SSH_SOCKET_CLOSED upon close.

The bug can be observed before the change by sending a bogus banner
to the server: 'echo -e "A\r\nB\r\n" | nc localhost 22'.  Each of
'A' and 'B' will be processed by 'callback_receive_banner', even
though the client socket is closed after rejection of 'A'.

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
ConfigureChecks: Stop checking for CMAKE_HAVE_THREADS_LIBRARY.

libssh is primarily interested in whether pthreads is present and can be
used. Checking for CMAKE_HAVE_THREADS_LIBRARY is not the same thing, as
there are cases where pthread exists but CMAKE_HAVE_THREADS_LIBRARY is not
set (for example, FreeBSD passes -DTHREADS_HAVE_PTHREAD_ARG=1 to CMake by
default as a way to skip the checks for -lpthread, -lpthreads and others and
tell the build system that -pthread is the one expected to be used).

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
threads: Be less strict when deciding whether to build libssh_threads.

As mentioned in the previous commit, there are cases where
CMAKE_HAVE_THREADS_LIBRARY is not set and pthreads _is_ being used: one can
pass -DTHREADS_HAVE_PTHREAD_ARG=1 to CMake directly so that it just passes
-pthread to the compiler/linker and does not set CMAKE_HAVE_THREADS_LIBRARY.

Since we are only interested in knowing whether any threading library has
been found, we should use CMAKE_THREAD_LIBS_INIT instead (Threads_FOUND
would also work).

Note that, at the moment, there is only a pthreads backend available in
threads/, so if it is not found configuration will fail because CMake will
try to create a library from an empty set of source files.

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
server: use custom server banners

Value of session->serverbanner never gets used

Signed-off-by: Audrius Butkevicius <audrius.butkevicius@gmail.com>
knownhosts: detect variations of ecdsa