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/*
Unix SMB/CIFS implementation.
schannel library code
Copyright (C) Andrew Tridgell 2004
Copyright (C) Andrew Bartlett <abartlet@samba.org> 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 2 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, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "includes.h"
#include "lib/crypto/crypto.h"
#include "auth/auth.h"
#include "auth/gensec/schannel.h"
#define NETSEC_SIGN_SIGNATURE { 0x77, 0x00, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00 }
#define NETSEC_SEAL_SIGNATURE { 0x77, 0x00, 0x7a, 0x00, 0xff, 0xff, 0x00, 0x00 }
/*******************************************************************
Encode or Decode the sequence number (which is symmetric)
********************************************************************/
static void netsec_deal_with_seq_num(struct schannel_state *state,
const uint8_t packet_digest[8],
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, packet_digest, 8, sequence_key);
arcfour_crypt(seq_num, sequence_key, 8);
state->seq_num++;
}
/*******************************************************************
Calculate the key with which to encode the data payload
********************************************************************/
static void netsec_get_sealing_key(const uint8_t session_key[16],
const uint8_t seq_num[8],
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] = session_key[i] ^ 0xf0;
}
hmac_md5(sess_kf0, zeros, 4, digest2);
hmac_md5(digest2, seq_num, 8, sealing_key);
}
/*******************************************************************
Create a digest over the entire packet (including the data), and
MD5 it with the session key.
********************************************************************/
static void schannel_digest(const uint8_t sess_key[16],
const uint8_t netsec_sig[8],
const uint8_t *confounder,
const uint8_t *data, size_t data_len,
uint8_t digest_final[16])
{
uint8_t packet_digest[16];
static const uint8_t zeros[4];
struct MD5Context ctx;
MD5Init(&ctx);
MD5Update(&ctx, zeros, 4);
MD5Update(&ctx, netsec_sig, 8);
if (confounder) {
MD5Update(&ctx, confounder, 8);
}
MD5Update(&ctx, data, data_len);
MD5Final(packet_digest, &ctx);
hmac_md5(sess_key, packet_digest, sizeof(packet_digest), digest_final);
}
/*
unseal a packet
*/
NTSTATUS schannel_unseal_packet(struct gensec_security *gensec_security,
TALLOC_CTX *mem_ctx,
uint8_t *data, size_t length,
const uint8_t *whole_pdu, size_t pdu_length,
DATA_BLOB *sig)
{
struct schannel_state *state = gensec_security->private_data;
uint8_t digest_final[16];
uint8_t confounder[8];
uint8_t seq_num[8];
uint8_t sealing_key[16];
static const uint8_t netsec_sig[8] = NETSEC_SEAL_SIGNATURE;
if (sig->length != 32) {
return NT_STATUS_ACCESS_DENIED;
}
memcpy(confounder, sig->data+24, 8);
RSIVAL(seq_num, 0, state->seq_num);
SIVAL(seq_num, 4, state->initiator?0:0x80);
netsec_get_sealing_key(state->creds->session_key, seq_num, sealing_key);
arcfour_crypt(confounder, sealing_key, 8);
arcfour_crypt(data, sealing_key, length);
schannel_digest(state->creds->session_key,
netsec_sig, confounder,
data, length, digest_final);
if (memcmp(digest_final, sig->data+16, 8) != 0) {
dump_data_pw("calc digest:", digest_final, 8);
dump_data_pw("wire digest:", sig->data+16, 8);
return NT_STATUS_ACCESS_DENIED;
}
netsec_deal_with_seq_num(state, digest_final, seq_num);
if (memcmp(seq_num, sig->data+8, 8) != 0) {
dump_data_pw("calc seq num:", seq_num, 8);
dump_data_pw("wire seq num:", sig->data+8, 8);
return NT_STATUS_ACCESS_DENIED;
}
return NT_STATUS_OK;
}
/*
check the signature on a packet
*/
NTSTATUS schannel_check_packet(struct gensec_security *gensec_security,
TALLOC_CTX *mem_ctx,
const uint8_t *data, size_t length,
const uint8_t *whole_pdu, size_t pdu_length,
const DATA_BLOB *sig)
{
struct schannel_state *state = gensec_security->private_data;
uint8_t digest_final[16];
uint8_t seq_num[8];
static const uint8_t netsec_sig[8] = NETSEC_SIGN_SIGNATURE;
/* w2k sends just 24 bytes and skip the confounder */
if (sig->length != 32 && sig->length != 24) {
return NT_STATUS_ACCESS_DENIED;
}
RSIVAL(seq_num, 0, state->seq_num);
SIVAL(seq_num, 4, state->initiator?0:0x80);
dump_data_pw("seq_num:\n", seq_num, 8);
dump_data_pw("sess_key:\n", state->creds->session_key, 16);
schannel_digest(state->creds->session_key,
netsec_sig, NULL,
data, length, digest_final);
netsec_deal_with_seq_num(state, digest_final, seq_num);
if (memcmp(seq_num, sig->data+8, 8) != 0) {
dump_data_pw("calc seq num:", seq_num, 8);
dump_data_pw("wire seq num:", sig->data+8, 8);
return NT_STATUS_ACCESS_DENIED;
}
if (memcmp(digest_final, sig->data+16, 8) != 0) {
dump_data_pw("calc digest:", digest_final, 8);
dump_data_pw("wire digest:", sig->data+16, 8);
return NT_STATUS_ACCESS_DENIED;
}
return NT_STATUS_OK;
}
/*
seal a packet
*/
NTSTATUS schannel_seal_packet(struct gensec_security *gensec_security,
TALLOC_CTX *mem_ctx,
uint8_t *data, size_t length,
const uint8_t *whole_pdu, size_t pdu_length,
DATA_BLOB *sig)
{
struct schannel_state *state = gensec_security->private_data;
uint8_t digest_final[16];
uint8_t confounder[8];
uint8_t seq_num[8];
uint8_t sealing_key[16];
static const uint8_t netsec_sig[8] = NETSEC_SEAL_SIGNATURE;
generate_random_buffer(confounder, 8);
RSIVAL(seq_num, 0, state->seq_num);
SIVAL(seq_num, 4, state->initiator?0x80:0);
schannel_digest(state->creds->session_key,
netsec_sig, confounder,
data, length, digest_final);
netsec_get_sealing_key(state->creds->session_key, seq_num, sealing_key);
arcfour_crypt(confounder, sealing_key, 8);
arcfour_crypt(data, sealing_key, length);
netsec_deal_with_seq_num(state, digest_final, seq_num);
(*sig) = data_blob_talloc(mem_ctx, NULL, 32);
memcpy(sig->data, netsec_sig, 8);
memcpy(sig->data+8, seq_num, 8);
memcpy(sig->data+16, digest_final, 8);
memcpy(sig->data+24, confounder, 8);
dump_data_pw("signature:", sig->data+ 0, 8);
dump_data_pw("seq_num :", sig->data+ 8, 8);
dump_data_pw("digest :", sig->data+16, 8);
dump_data_pw("confound :", sig->data+24, 8);
return NT_STATUS_OK;
}
/*
sign a packet
*/
NTSTATUS schannel_sign_packet(struct gensec_security *gensec_security,
TALLOC_CTX *mem_ctx,
const uint8_t *data, size_t length,
const uint8_t *whole_pdu, size_t pdu_length,
DATA_BLOB *sig)
{
struct schannel_state *state = gensec_security->private_data;
uint8_t digest_final[16];
uint8_t seq_num[8];
static const uint8_t netsec_sig[8] = NETSEC_SIGN_SIGNATURE;
RSIVAL(seq_num, 0, state->seq_num);
SIVAL(seq_num, 4, state->initiator?0x80:0);
schannel_digest(state->creds->session_key,
netsec_sig, NULL,
data, length, digest_final);
netsec_deal_with_seq_num(state, digest_final, seq_num);
(*sig) = data_blob_talloc(mem_ctx, NULL, 32);
memcpy(sig->data, netsec_sig, 8);
memcpy(sig->data+8, seq_num, 8);
memcpy(sig->data+16, digest_final, 8);
memset(sig->data+24, 0, 8);
dump_data_pw("signature:", sig->data+ 0, 8);
dump_data_pw("seq_num :", sig->data+ 8, 8);
dump_data_pw("digest :", sig->data+16, 8);
dump_data_pw("confound :", sig->data+24, 8);
return NT_STATUS_OK;
}
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