smb_signing.c

samba-3.0.22.tar.gz 编译smb服务器的源码

/* 
   Unix SMB/CIFS implementation.
   SMB Signing Code
   Copyright (C) Jeremy Allison 2003.
   Copyright (C) Andrew Bartlett <[e-mail]> 2002-2003
   
   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 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"

/* Lookup a packet's MID (multiplex id) and figure out it's sequence number */
struct outstanding_packet_lookup {
	uint16 mid;
	uint32 reply_seq_num;
	struct outstanding_packet_lookup *prev, *next;
};

/* Store the data for an ongoing trans/trans2/nttrans operation. */
struct trans_info_context {
	uint16 mid;
	uint32 send_seq_num;
	uint32 reply_seq_num;
};

struct smb_basic_signing_context {
	DATA_BLOB mac_key;
	uint32 send_seq_num;
	struct trans_info_context *trans_info;
	struct outstanding_packet_lookup *outstanding_packet_list;
};

static BOOL store_sequence_for_reply(struct outstanding_packet_lookup **list, 
				     uint16 mid, uint32 reply_seq_num)
{
	struct outstanding_packet_lookup *t;

	/* Ensure we only add a mid once. */
	for (t = *list; t; t = t->next) {
		if (t->mid == mid) {
			return False;
		}
	}

	t = SMB_XMALLOC_P(struct outstanding_packet_lookup);
	ZERO_STRUCTP(t);

	t->mid = mid;
	t->reply_seq_num = reply_seq_num;

	/*
	 * Add to the *start* of the list not the end of the list.
	 * This ensures that the *last* send sequence with this mid
	 * is returned by preference.
	 * This can happen if the mid wraps and one of the early
	 * mid numbers didn't get a reply and is still lurking on
	 * the list. JRA. Found by Fran Fabrizio <[e-mail]>.
	 */

	DLIST_ADD(*list, t);
	DEBUG(10,("store_sequence_for_reply: stored seq = %u mid = %u\n",
			(unsigned int)reply_seq_num, (unsigned int)mid ));
	return True;
}

static BOOL get_sequence_for_reply(struct outstanding_packet_lookup **list,
				   uint16 mid, uint32 *reply_seq_num)
{
	struct outstanding_packet_lookup *t;

	for (t = *list; t; t = t->next) {
		if (t->mid == mid) {
			*reply_seq_num = t->reply_seq_num;
			DEBUG(10,("get_sequence_for_reply: found seq = %u mid = %u\n",
				(unsigned int)t->reply_seq_num, (unsigned int)t->mid ));
			DLIST_REMOVE(*list, t);
			SAFE_FREE(t);
			return True;
		}
	}
	return False;
}

/***********************************************************
 SMB signing - Common code before we set a new signing implementation
************************************************************/

static BOOL cli_set_smb_signing_common(struct cli_state *cli) 
{
	if (!cli->sign_info.negotiated_smb_signing 
	    && !cli->sign_info.mandatory_signing) {
		return False;
	}

	if (cli->sign_info.doing_signing) {
		return False;
	}
	
	if (cli->sign_info.free_signing_context)
		cli->sign_info.free_signing_context(&cli->sign_info);

	/* These calls are INCOMPATIBLE with SMB signing */
	cli->readbraw_supported = False;
	cli->writebraw_supported = False;
	
	return True;
}

/***********************************************************
 SMB signing - Common code for 'real' implementations
************************************************************/

static BOOL set_smb_signing_real_common(struct smb_sign_info *si)
{
	if (si->mandatory_signing) {
		DEBUG(5, ("Mandatory SMB signing enabled!\n"));
	}

	si->doing_signing = True;
	DEBUG(5, ("SMB signing enabled!\n"));

	return True;
}

static void mark_packet_signed(char *outbuf)
{
	uint16 flags2;
	flags2 = SVAL(outbuf,smb_flg2);
	flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
	SSVAL(outbuf,smb_flg2, flags2);
}

/***********************************************************
 SMB signing - NULL implementation - calculate a MAC to send.
************************************************************/

static void null_sign_outgoing_message(char *outbuf, struct smb_sign_info *si)
{
	/* we can't zero out the sig, as we might be trying to send a
	   session request - which is NBT-level, not SMB level and doesn't
	   have the field */
	return;
}

/***********************************************************
 SMB signing - NULL implementation - check a MAC sent by server.
************************************************************/

static BOOL null_check_incoming_message(char *inbuf, struct smb_sign_info *si, BOOL must_be_ok)
{
	return True;
}

/***********************************************************
 SMB signing - NULL implementation - free signing context
************************************************************/

static void null_free_signing_context(struct smb_sign_info *si)
{
	return;
}

/**
 SMB signing - NULL implementation - setup the MAC key.

 @note Used as an initialisation only - it will not correctly
       shut down a real signing mechanism
*/

static BOOL null_set_signing(struct smb_sign_info *si)
{
	si->signing_context = NULL;
	
	si->sign_outgoing_message = null_sign_outgoing_message;
	si->check_incoming_message = null_check_incoming_message;
	si->free_signing_context = null_free_signing_context;

	return True;
}

/**
 * Free the signing context
 */
 
static void free_signing_context(struct smb_sign_info *si)
{
	if (si->free_signing_context) {
		si->free_signing_context(si);
		si->signing_context = NULL;
	}

	null_set_signing(si);
}


static BOOL signing_good(char *inbuf, struct smb_sign_info *si, BOOL good, uint32 seq, BOOL must_be_ok) 
{
	if (good) {

		if (!si->doing_signing) {
			si->doing_signing = True;
		}
		
		if (!si->seen_valid) {
			si->seen_valid = True;
		}

	} else {
		if (!si->mandatory_signing && !si->seen_valid) {

			if (!must_be_ok) {
				return True;
			}
			/* Non-mandatory signing - just turn off if this is the first bad packet.. */
			DEBUG(5, ("srv_check_incoming_message: signing negotiated but not required and peer\n"
				  "isn't sending correct signatures. Turning off.\n"));
			si->negotiated_smb_signing = False;
			si->allow_smb_signing = False;
			si->doing_signing = False;
			free_signing_context(si);
			return True;
		} else if (!must_be_ok) {
			/* This packet is known to be unsigned */
			return True;
		} else {
			/* Mandatory signing or bad packet after signing started - fail and disconnect. */
			if (seq)
				DEBUG(0, ("signing_good: BAD SIG: seq %u\n", (unsigned int)seq));
			return False;
		}
	}
	return True;
}	

/***********************************************************
 SMB signing - Simple implementation - calculate a MAC on the packet
************************************************************/

static void simple_packet_signature(struct smb_basic_signing_context *data, 
				    const uchar *buf, uint32 seq_number, 
				    unsigned char calc_md5_mac[16])
{
	const size_t offset_end_of_sig = (smb_ss_field + 8);
	unsigned char sequence_buf[8];
	struct MD5Context md5_ctx;
#if 0
        /* JRA - apparently this is incorrect. */
	unsigned char key_buf[16];
#endif

	/*
	 * Firstly put the sequence number into the first 4 bytes.
	 * and zero out the next 4 bytes.
	 *
	 * We do this here, to avoid modifying the packet.
	 */

	DEBUG(10,("simple_packet_signature: sequence number %u\n", seq_number ));

	SIVAL(sequence_buf, 0, seq_number);
	SIVAL(sequence_buf, 4, 0);

	/* Calculate the 16 byte MAC - but don't alter the data in the
	   incoming packet.
	   
	   This makes for a bit of fussing about, but it's not too bad.
	*/
	MD5Init(&md5_ctx);

	/* intialise with the key */
	MD5Update(&md5_ctx, data->mac_key.data, data->mac_key.length); 
#if 0
	/* JRA - apparently this is incorrect. */
	/* NB. When making and verifying SMB signatures, Windows apparently
		zero-pads the key to 128 bits if it isn't long enough.
		From Nalin Dahyabhai <[e-mail]> */
	if (data->mac_key.length < sizeof(key_buf)) {
		memset(key_buf, 0, sizeof(key_buf));
		MD5Update(&md5_ctx, key_buf, sizeof(key_buf) - data->mac_key.length);
	}
#endif

	/* copy in the first bit of the SMB header */
	MD5Update(&md5_ctx, buf + 4, smb_ss_field - 4);

	/* copy in the sequence number, instead of the signature */
	MD5Update(&md5_ctx, sequence_buf, sizeof(sequence_buf));

	/* copy in the rest of the packet in, skipping the signature */
	MD5Update(&md5_ctx, buf + offset_end_of_sig, 
		  smb_len(buf) - (offset_end_of_sig - 4));

	/* calculate the MD5 sig */ 
	MD5Final(calc_md5_mac, &md5_ctx);
}


/***********************************************************
 SMB signing - Client implementation - send the MAC.
************************************************************/

static void client_sign_outgoing_message(char *outbuf, struct smb_sign_info *si)
{
	unsigned char calc_md5_mac[16];
	struct smb_basic_signing_context *data = si->signing_context;
	uint32 send_seq_num;

	if (!si->doing_signing)
		return;

	/* JRA Paranioa test - we should be able to get rid of this... */
	if (smb_len(outbuf) < (smb_ss_field + 8 - 4)) {
		DEBUG(1, ("client_sign_outgoing_message: Logic error. Can't check signature on short packet! smb_len = %u\n",
					smb_len(outbuf) ));
		abort();
	}

	/* mark the packet as signed - BEFORE we sign it...*/
	mark_packet_signed(outbuf);

	if (data->trans_info)
		send_seq_num = data->trans_info->send_seq_num;
	else
		send_seq_num = data->send_seq_num;

	simple_packet_signature(data, (const unsigned char *)outbuf, send_seq_num, calc_md5_mac);

	DEBUG(10, ("client_sign_outgoing_message: sent SMB signature of\n"));
	dump_data(10, (const char *)calc_md5_mac, 8);

	memcpy(&outbuf[smb_ss_field], calc_md5_mac, 8);

/*	cli->outbuf[smb_ss_field+2]=0; 
	Uncomment this to test if the remote server actually verifies signatures...*/

	if (data->trans_info)
		return;

	data->send_seq_num++;
	store_sequence_for_reply(&data->outstanding_packet_list, 
				 SVAL(outbuf,smb_mid), data->send_seq_num);
	data->send_seq_num++;
}

/***********************************************************
 SMB signing - Client implementation - check a MAC sent by server.
************************************************************/

static BOOL client_check_incoming_message(char *inbuf, struct smb_sign_info *si, BOOL must_be_ok)
{
	BOOL good;