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/*
Unix SMB/CIFS implementation.
SMB Signing Code
Copyright (C) Jeremy Allison 2002.
Copyright (C) Andrew Bartlett <abartlet@samba.org> 2002-2003
Copyright (C) James J Myers <myersjj@samba.org> 2003
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/raw/libcliraw.h"
#include "libcli/raw/raw_proto.h"
#include "../lib/crypto/crypto.h"
/***********************************************************
SMB signing - Common code before we set a new signing implementation
************************************************************/
bool set_smb_signing_common(struct smb_signing_context *sign_info)
{
if (sign_info->doing_signing) {
DEBUG(5, ("SMB Signing already in progress, so we don't start it again\n"));
return false;
}
if (!sign_info->allow_smb_signing) {
DEBUG(5, ("SMB Signing has been locally disabled\n"));
return false;
}
return true;
}
void mark_packet_signed(struct smb_request_buffer *out)
{
uint16_t flags2;
flags2 = SVAL(out->hdr, HDR_FLG2);
flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
SSVAL(out->hdr, HDR_FLG2, flags2);
}
bool signing_good(struct smb_signing_context *sign_info,
unsigned int seq, bool good)
{
if (good) {
if (!sign_info->doing_signing) {
DEBUG(5, ("Seen valid packet, so turning signing on\n"));
sign_info->doing_signing = true;
}
if (!sign_info->seen_valid) {
DEBUG(5, ("Seen valid packet, so marking signing as 'seen valid'\n"));
sign_info->seen_valid = true;
}
} else {
if (!sign_info->seen_valid) {
/* If we have never seen a good packet, just turn it off */
DEBUG(5, ("signing_good: signing negotiated but not required and peer\n"
"isn't sending correct signatures. Turning off.\n"));
smbcli_set_signing_off(sign_info);
return true;
} else {
/* bad packet after signing started - fail and disconnect. */
DEBUG(0, ("signing_good: BAD SIG: seq %u\n", seq));
return false;
}
}
return true;
}
void sign_outgoing_message(struct smb_request_buffer *out, DATA_BLOB *mac_key, unsigned int seq_num)
{
uint8_t calc_md5_mac[16];
MD5_CTX md5_ctx;
/*
* Firstly put the sequence number into the first 4 bytes.
* and zero out the next 4 bytes.
*/
SIVAL(out->hdr, HDR_SS_FIELD, seq_num);
SIVAL(out->hdr, HDR_SS_FIELD + 4, 0);
/* mark the packet as signed - BEFORE we sign it...*/
mark_packet_signed(out);
/* Calculate the 16 byte MAC and place first 8 bytes into the field. */
MD5Init(&md5_ctx);
MD5Update(&md5_ctx, mac_key->data, mac_key->length);
MD5Update(&md5_ctx,
out->buffer + NBT_HDR_SIZE,
out->size - NBT_HDR_SIZE);
MD5Final(calc_md5_mac, &md5_ctx);
memcpy(&out->hdr[HDR_SS_FIELD], calc_md5_mac, 8);
DEBUG(5, ("sign_outgoing_message: SENT SIG (seq: %d): sent SMB signature of\n",
seq_num));
dump_data(5, calc_md5_mac, 8);
/* req->out.hdr[HDR_SS_FIELD+2]=0;
Uncomment this to test if the remote server actually verifies signitures...*/
}
bool check_signed_incoming_message(struct smb_request_buffer *in, DATA_BLOB *mac_key, unsigned int seq_num)
{
bool good;
uint8_t calc_md5_mac[16];
uint8_t *server_sent_mac;
uint8_t sequence_buf[8];
MD5_CTX md5_ctx;
const size_t offset_end_of_sig = (HDR_SS_FIELD + 8);
int i;
const int sign_range = 0;
/* room enough for the signature? */
if (in->size < NBT_HDR_SIZE + HDR_SS_FIELD + 8) {
return false;
}
if (!mac_key->length) {
/* NO key yet */
return false;
}
/* its quite bogus to be guessing sequence numbers, but very useful
when debugging signing implementations */
for (i = 0-sign_range; i <= 0+sign_range; i++) {
/*
* Firstly put the sequence number into the first 4 bytes.
* and zero out the next 4 bytes.
*/
SIVAL(sequence_buf, 0, seq_num + i);
SIVAL(sequence_buf, 4, 0);
/* get a copy of the server-sent mac */
server_sent_mac = &in->hdr[HDR_SS_FIELD];
/* Calculate the 16 byte MAC and place first 8 bytes into the field. */
MD5Init(&md5_ctx);
MD5Update(&md5_ctx, mac_key->data,
mac_key->length);
MD5Update(&md5_ctx, in->hdr, HDR_SS_FIELD);
MD5Update(&md5_ctx, sequence_buf, sizeof(sequence_buf));
MD5Update(&md5_ctx, in->hdr + offset_end_of_sig,
in->size - NBT_HDR_SIZE - (offset_end_of_sig));
MD5Final(calc_md5_mac, &md5_ctx);
good = (memcmp(server_sent_mac, calc_md5_mac, 8) == 0);
if (i == 0) {
if (!good) {
DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): wanted SMB signature of\n", seq_num + i));
dump_data(5, calc_md5_mac, 8);
DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): got SMB signature of\n", seq_num + i));
dump_data(5, server_sent_mac, 8);
} else {
DEBUG(15, ("check_signed_incoming_message: GOOD SIG (seq: %d): got SMB signature of\n", seq_num + i));
dump_data(5, server_sent_mac, 8);
}
}
if (good) break;
}
if (good && i != 0) {
DEBUG(0,("SIGNING OFFSET %d (should be %d)\n", i, seq_num));
}
return good;
}
/**
SMB signing - NULL implementation
@note Used as an initialisation only - it will not correctly
shut down a real signing mechanism
*/
bool smbcli_set_signing_off(struct smb_signing_context *sign_info)
{
DEBUG(5, ("Shutdown SMB signing\n"));
sign_info->doing_signing = false;
data_blob_free(&sign_info->mac_key);
sign_info->signing_state = SMB_SIGNING_ENGINE_OFF;
return true;
}
/***********************************************************
SMB signing - Simple implementation - setup the MAC key.
************************************************************/
bool smbcli_simple_set_signing(TALLOC_CTX *mem_ctx,
struct smb_signing_context *sign_info,
const DATA_BLOB *user_session_key,
const DATA_BLOB *response)
{
if (sign_info->mandatory_signing) {
DEBUG(5, ("Mandatory SMB signing enabled!\n"));
}
DEBUG(5, ("SMB signing enabled!\n"));
if (response && response->length) {
sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, response->length + user_session_key->length);
} else {
sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, user_session_key->length);
}
memcpy(&sign_info->mac_key.data[0], user_session_key->data, user_session_key->length);
if (response && response->length) {
memcpy(&sign_info->mac_key.data[user_session_key->length],response->data, response->length);
}
dump_data_pw("Started Signing with key:\n", sign_info->mac_key.data, sign_info->mac_key.length);
sign_info->signing_state = SMB_SIGNING_ENGINE_ON;
sign_info->next_seq_num = 2;
return true;
}
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