/*
    Copyright (c) 2007-2016 Contributors as noted in the AUTHORS file

    This file is part of libzmq, the ZeroMQ core engine in C++.

    libzmq is free software; you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License (LGPL) as published
    by the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    As a special exception, the Contributors give you permission to link
    this library with independent modules to produce an executable,
    regardless of the license terms of these independent modules, and to
    copy and distribute the resulting executable under terms of your choice,
    provided that you also meet, for each linked independent module, the
    terms and conditions of the license of that module. An independent
    module is a module which is not derived from or based on this library.
    If you modify this library, you must extend this exception to your
    version of the library.

    libzmq is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
    License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "precompiled.hpp"
#include "platform.hpp"

#ifdef HAVE_LIBGSSAPI_KRB5

#ifdef ZMQ_HAVE_WINDOWS
#include "windows.hpp"
#endif

#include <string.h>
#include <string>

#include "msg.hpp"
#include "session_base.hpp"
#include "err.hpp"
#include "gssapi_server.hpp"
#include "wire.hpp"

#include <gssapi/gssapi.h>

zmq::gssapi_server_t::gssapi_server_t (session_base_t *session_,
                                       const std::string &peer_address_,
                                       const options_t &options_) :
    gssapi_mechanism_base_t (options_),
    session (session_),
    peer_address (peer_address_),
    state (recv_next_token),
    security_context_established (false)
{
    maj_stat = GSS_S_CONTINUE_NEEDED;
    if(!options_.gss_principal.empty())
    {
        const std::string::size_type principal_size = options_.gss_principal.size();
        principal_name = static_cast <char *>(malloc(principal_size+1));
        assert(principal_name);
        memcpy(principal_name, options_.gss_principal.c_str(), principal_size+1 );

        if (acquire_credentials (principal_name, &cred) != 0)
            maj_stat = GSS_S_FAILURE;
    }
}

zmq::gssapi_server_t::~gssapi_server_t ()
{
    if(cred)
        gss_release_cred(&min_stat, &cred);

    if(target_name)
        gss_release_name(&min_stat, &target_name);
}

int zmq::gssapi_server_t::next_handshake_command (msg_t *msg_)
{
    if (state == send_ready) {
        int rc = produce_ready(msg_);
        if (rc == 0)
            state = recv_ready;

        return rc;
    }

    if (state != send_next_token) {
        errno = EAGAIN;
        return -1;
    }

    if (produce_next_token (msg_) < 0)
        return -1;

    if (maj_stat != GSS_S_CONTINUE_NEEDED && maj_stat != GSS_S_COMPLETE)
        return -1;

    if (maj_stat == GSS_S_COMPLETE) {
        security_context_established = true;
    }

    state = recv_next_token;

    return 0;
}

int zmq::gssapi_server_t::process_handshake_command (msg_t *msg_)
{
    if (state == recv_ready) {
        int rc = process_ready(msg_);
        if (rc == 0)
            state = connected;

        return rc;
    }

    if (state != recv_next_token) {
        errno = EPROTO;
        return -1;
    }

    if (security_context_established) {
        //  Use ZAP protocol (RFC 27) to authenticate the user.
        bool expecting_zap_reply = false;
        int rc = session->zap_connect ();
        if (rc == 0) {
            send_zap_request();
            rc = receive_and_process_zap_reply ();
            if (rc != 0) {
                if (errno != EAGAIN)
                    return -1;
                expecting_zap_reply = true;
            }
        }
        state = expecting_zap_reply? expect_zap_reply: send_ready;
        return 0;
    }

    if (process_next_token (msg_) < 0)
        return -1;

    accept_context ();
    state = send_next_token;

    errno_assert (msg_->close () == 0);
    errno_assert (msg_->init () == 0);

    return 0;
}

void zmq::gssapi_server_t::send_zap_request ()
{
    int rc;
    msg_t msg;

    //  Address delimiter frame
    rc = msg.init ();
    errno_assert (rc == 0);
    msg.set_flags (msg_t::more);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);

    //  Version frame
    rc = msg.init_size (3);
    errno_assert (rc == 0);
    memcpy (msg.data (), "1.0", 3);
    msg.set_flags (msg_t::more);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);

    //  Request ID frame
    rc = msg.init_size (1);
    errno_assert (rc == 0);
    memcpy (msg.data (), "1", 1);
    msg.set_flags (msg_t::more);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);

    //  Domain frame
    rc = msg.init_size (options.zap_domain.length ());
    errno_assert (rc == 0);
    memcpy (msg.data (), options.zap_domain.c_str (), options.zap_domain.length ());
    msg.set_flags (msg_t::more);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);

    //  Address frame
    rc = msg.init_size (peer_address.length ());
    errno_assert (rc == 0);
    memcpy (msg.data (), peer_address.c_str (), peer_address.length ());
    msg.set_flags (msg_t::more);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);

    //  Identity frame
    rc = msg.init_size (options.identity_size);
    errno_assert (rc == 0);
    memcpy (msg.data (), options.identity, options.identity_size);
    msg.set_flags (msg_t::more);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);

    //  Mechanism frame
    rc = msg.init_size (6);
    errno_assert (rc == 0);
    memcpy (msg.data (), "GSSAPI", 6);
    msg.set_flags (msg_t::more);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);

    //  Principal frame
    gss_buffer_desc principal;
    gss_display_name(&min_stat, target_name, &principal, NULL);

    rc = msg.init_size (principal.length);
    errno_assert (rc == 0);
    memcpy (msg.data (), principal.value, principal.length);
    rc = session->write_zap_msg (&msg);
    errno_assert (rc == 0);
    gss_release_buffer(&min_stat, &principal);
}

int zmq::gssapi_server_t::receive_and_process_zap_reply ()
{
    int rc = 0;
    msg_t msg [7];  //  ZAP reply consists of 7 frames

    //  Initialize all reply frames
    for (int i = 0; i < 7; i++) {
        rc = msg [i].init ();
        errno_assert (rc == 0);
    }

    for (int i = 0; i < 7; i++) {
        rc = session->read_zap_msg (&msg [i]);
        if (rc == -1)
            break;
        if ((msg [i].flags () & msg_t::more) == (i < 6? 0: msg_t::more)) {
            errno = EPROTO;
            rc = -1;
            break;
        }
    }

    if (rc != 0)
        goto error;

    //  Address delimiter frame
    if (msg [0].size () > 0) {
        rc = -1;
        errno = EPROTO;
        goto error;
    }

    //  Version frame
    if (msg [1].size () != 3 || memcmp (msg [1].data (), "1.0", 3)) {
        rc = -1;
        errno = EPROTO;
        goto error;
    }

    //  Request id frame
    if (msg [2].size () != 1 || memcmp (msg [2].data (), "1", 1)) {
        rc = -1;
        errno = EPROTO;
        goto error;
    }

    //  Status code frame
    if (msg [3].size () != 3 || memcmp (msg [3].data (), "200", 3)) {
        rc = -1;
        errno = EACCES;
        goto error;
    }

    //  Save user id
    set_user_id (msg [5].data (), msg [5].size ());

    //  Process metadata frame
    rc = parse_metadata (static_cast <const unsigned char*> (msg [6].data ()),
                         msg [6].size (), true);

error:
    for (int i = 0; i < 7; i++) {
        const int rc2 = msg [i].close ();
        errno_assert (rc2 == 0);
    }

    return rc;
}


int zmq::gssapi_server_t::encode (msg_t *msg_)
{
    zmq_assert (state == connected);

    if (do_encryption)
      return encode_message (msg_);

    return 0;
}

int zmq::gssapi_server_t::decode (msg_t *msg_)
{
    zmq_assert (state == connected);

    if (do_encryption)
      return decode_message (msg_);

    return 0;
}

int zmq::gssapi_server_t::zap_msg_available ()
{
    if (state != expect_zap_reply) {
        errno = EFSM;
        return -1;
    }
    const int rc = receive_and_process_zap_reply ();
    if (rc == 0)
        state = send_ready;
    return rc;
}

zmq::mechanism_t::status_t zmq::gssapi_server_t::status () const
{
    return state == connected? mechanism_t::ready: mechanism_t::handshaking;
}

int zmq::gssapi_server_t::produce_next_token (msg_t *msg_)
{
    if (send_tok.length != 0) { // Client expects another token
        if (produce_initiate(msg_, send_tok.value, send_tok.length) < 0)
            return -1;
        gss_release_buffer(&min_stat, &send_tok);
    }

    if (maj_stat != GSS_S_COMPLETE && maj_stat != GSS_S_CONTINUE_NEEDED) {
        gss_release_name(&min_stat, &target_name);
        if (context != GSS_C_NO_CONTEXT)
            gss_delete_sec_context(&min_stat, &context, GSS_C_NO_BUFFER);
        return -1;
    }

    return 0;
}

int zmq::gssapi_server_t::process_next_token (msg_t *msg_)
{
    if (maj_stat == GSS_S_CONTINUE_NEEDED) {
        if (process_initiate(msg_, &recv_tok.value, recv_tok.length) < 0) {
            if (target_name != GSS_C_NO_NAME)
                gss_release_name(&min_stat, &target_name);
            return -1;
        }
    }

    return 0;
}

void zmq::gssapi_server_t::accept_context ()
{
    maj_stat = gss_accept_sec_context(&init_sec_min_stat, &context, cred,
                                      &recv_tok, GSS_C_NO_CHANNEL_BINDINGS,
                                      &target_name, &doid, &send_tok,
                                      &ret_flags, NULL, NULL);

    if (recv_tok.value) {
        free (recv_tok.value);
        recv_tok.value = NULL;
    }
}

#endif