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samba-mirror/libcli/auth/schannel_sign.c
Stefan Metzmacher 033ced60ac libcli/auth: rewrite schannel sign/seal code to be more generic
This prepares support for HMAC-SHA256/AES.

metze
2009-09-16 12:29:06 +02:00

269 lines
6.7 KiB
C

/*
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 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];
struct MD5Context 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);
if (do_unseal) {
netsec_do_seal(state, seq_num,
confounder,
data, length);
}
netsec_do_sign(state, confounder,
data, length,
header, checksum);
ret = memcmp(checksum, sig->data+16, checksum_length);
if (ret != 0) {
dump_data_pw("calc digest:", checksum, checksum_length);
dump_data_pw("wire digest:", sig->data+16, checksum_length);
return NT_STATUS_ACCESS_DENIED;
}
netsec_do_seq_num(state, checksum, checksum_length, seq_num);
ret = memcmp(seq_num, sig->data+8, 8);
if (ret != 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;
}
NTSTATUS netsec_outgoing_packet(struct schannel_state *state,
TALLOC_CTX *mem_ctx,
bool do_seal,
uint8_t *data, size_t length,
DATA_BLOB *sig)
{
uint32_t min_sig_size = 0;
uint32_t used_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];
netsec_offset_and_sizes(state,
do_seal,
&min_sig_size,
&used_sig_size,
&checksum_length,
&confounder_ofs);
RSIVAL(seq_num, 0, state->seq_num);
SIVAL(seq_num, 4, state->initiator?0x80:0);
if (do_seal) {
confounder = _confounder;
generate_random_buffer(confounder, 8);
} else {
confounder = NULL;
}
netsec_do_sign(state, confounder,
data, length,
header, checksum);
if (do_seal) {
netsec_do_seal(state, seq_num,
confounder,
data, length);
}
netsec_do_seq_num(state, checksum, checksum_length, seq_num);
(*sig) = data_blob_talloc_zero(mem_ctx, used_sig_size);
memcpy(sig->data, header, 8);
memcpy(sig->data+8, seq_num, 8);
memcpy(sig->data+16, checksum, checksum_length);
if (confounder) {
memcpy(sig->data+confounder_ofs, 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, checksum_length);
dump_data_pw("confound :", sig->data+confounder_ofs, 8);
return NT_STATUS_OK;
}