source: trunk/server/libcli/auth/schannel_sign.c@ 752

/*
   Unix SMB/CIFS implementation.

   schannel library code

   Copyright (C) Andrew Tridgell 2004
   Copyright (C) Andrew Bartlett <[email protected]> 2005

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

   This program 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 General Public License for more details.

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

#include "includes.h"
#include "../libcli/auth/schannel.h"
#include "../lib/crypto/crypto.h"

static void netsec_offset_and_sizes(struct schannel_state *state,
                                    bool do_seal,
                                    uint32_t *_min_sig_size,
                                    uint32_t *_used_sig_size,
                                    uint32_t *_checksum_length,
                                    uint32_t *_confounder_ofs)
{
        uint32_t min_sig_size = 24;
        uint32_t used_sig_size = 32;
        uint32_t checksum_length = 8;
        uint32_t confounder_ofs = 24;

        if (do_seal) {
                min_sig_size += 8;
        }

        if (_min_sig_size) {
                *_min_sig_size = min_sig_size;
        }

        if (_used_sig_size) {
                *_used_sig_size = used_sig_size;
        }

        if (_checksum_length) {
                *_checksum_length = checksum_length;
        }

        if (_confounder_ofs) {
                *_confounder_ofs = confounder_ofs;
        }
}

/*******************************************************************
 Encode or Decode the sequence number (which is symmetric)
 ********************************************************************/
static void netsec_do_seq_num(struct schannel_state *state,
                              const uint8_t *checksum,
                              uint32_t checksum_length,
                              uint8_t seq_num[8])
{
        static const uint8_t zeros[4];
        uint8_t sequence_key[16];
        uint8_t digest1[16];

        hmac_md5(state->creds->session_key, zeros, sizeof(zeros), digest1);
        hmac_md5(digest1, checksum, checksum_length, sequence_key);
        arcfour_crypt(seq_num, sequence_key, 8);

        state->seq_num++;
}

static void netsec_do_seal(struct schannel_state *state,
                           const uint8_t seq_num[8],
                           uint8_t confounder[8],
                           uint8_t *data, uint32_t length)
{
        uint8_t sealing_key[16];
        static const uint8_t zeros[4];
        uint8_t digest2[16];
        uint8_t sess_kf0[16];
        int i;

        for (i = 0; i < 16; i++) {
                sess_kf0[i] = state->creds->session_key[i] ^ 0xf0;
        }

        hmac_md5(sess_kf0, zeros, 4, digest2);
        hmac_md5(digest2, seq_num, 8, sealing_key);

        arcfour_crypt(confounder, sealing_key, 8);
        arcfour_crypt(data, sealing_key, length);
}

/*******************************************************************
 Create a digest over the entire packet (including the data), and
 MD5 it with the session key.
 ********************************************************************/
static void netsec_do_sign(struct schannel_state *state,
                           const uint8_t *confounder,
                           const uint8_t *data, size_t data_len,
                           uint8_t header[8],
                           uint8_t *checksum)
{
        uint8_t packet_digest[16];
        static const uint8_t zeros[4];
        MD5_CTX ctx;

        MD5Init(&ctx);
        MD5Update(&ctx, zeros, 4);
        if (confounder) {
                SSVAL(header, 0, NL_SIGN_HMAC_MD5);
                SSVAL(header, 2, NL_SEAL_RC4);
                SSVAL(header, 4, 0xFFFF);
                SSVAL(header, 6, 0x0000);

                MD5Update(&ctx, header, 8);
                MD5Update(&ctx, confounder, 8);
        } else {
                SSVAL(header, 0, NL_SIGN_HMAC_MD5);
                SSVAL(header, 2, NL_SEAL_NONE);
                SSVAL(header, 4, 0xFFFF);
                SSVAL(header, 6, 0x0000);

                MD5Update(&ctx, header, 8);
        }
        MD5Update(&ctx, data, data_len);
        MD5Final(packet_digest, &ctx);

        hmac_md5(state->creds->session_key,
                 packet_digest, sizeof(packet_digest),
                 checksum);
}

NTSTATUS netsec_incoming_packet(struct schannel_state *state,
                                TALLOC_CTX *mem_ctx,
                                bool do_unseal,
                                uint8_t *data, size_t length,
                                const DATA_BLOB *sig)
{
        uint32_t min_sig_size = 0;
        uint8_t header[8];
        uint8_t checksum[32];
        uint32_t checksum_length = sizeof(checksum_length);
        uint8_t _confounder[8];
        uint8_t *confounder = NULL;
        uint32_t confounder_ofs = 0;
        uint8_t seq_num[8];
        int ret;

        netsec_offset_and_sizes(state,
                                do_unseal,
                                &min_sig_size,
                                NULL,
                                &checksum_length,
                                &confounder_ofs);

        if (sig->length < min_sig_size) {
                return NT_STATUS_ACCESS_DENIED;
        }

        if (do_unseal) {
                confounder = _confounder;
                memcpy(confounder, sig->data+confounder_ofs, 8);
        } else {
                confounder = NULL;
        }

        RSIVAL(seq_num, 0, state->seq_num);
        SIVAL(seq_num, 4, state->initiator?0:0x80);