/*
 * security.c - Code for handling security/ACLs in NTFS.  Part of the
 *		Linux-NTFS project.
 *
 * Copyright (c) 2004 Anton Altaparmakov
 *
 * This program/include file 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/include file 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 (in the main directory of the Linux-NTFS
 * distribution in the file COPYING); if not, write to the Free Software
 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "config.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include "types.h"
#include "layout.h"
#include "security.h"

/*
 * The zero GUID.
 */
static const GUID __zero_guid = { const_cpu_to_le32(0), const_cpu_to_le16(0),
		const_cpu_to_le16(0), { 0, 0, 0, 0, 0, 0, 0, 0 } };
const GUID *const zero_guid = &__zero_guid;

/**
 * ntfs_guid_is_zero - check if a GUID is zero
 * @guid:	[IN] guid to check
 *
 * Return TRUE if @guid is a valid pointer to a GUID and it is the zero GUID
 * and FALSE otherwise.
 */
BOOL ntfs_guid_is_zero(const GUID *guid)
{
	return (memcmp(guid, zero_guid, sizeof(*zero_guid)));
}

/**
 * ntfs_guid_to_mbs - convert a GUID to a multi byte string
 * @guid:	[IN]  guid to convert
 * @guid_str:	[OUT] string in which to return the GUID (optional)
 *
 * Convert the GUID pointed to by @guid to a multi byte string of the form
 * "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX".  Therefore, @guid_str (if not NULL)
 * needs to be able to store at least 37 bytes.
 *
 * If @guid_str is not NULL it will contain the converted GUID on return.  If
 * it is NULL a string will be allocated and this will be returned.  The caller
 * is responsible for free()ing the string in that case.
 *
 * On success return the converted string and on failure return NULL with errno
 * set to the error code.
 */
char *ntfs_guid_to_mbs(const GUID *guid, char *guid_str)
{
	char *_guid_str;
	int res;

	if (!guid) {
		errno = EINVAL;
		return NULL;
	}
	_guid_str = guid_str;
	if (!_guid_str) {
		_guid_str = malloc(37);
		if (!_guid_str)
			return _guid_str;
	}
	res = snprintf(_guid_str, 37,
			"%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
			(unsigned int)le32_to_cpu(guid->data1),
			le16_to_cpu(guid->data2), le16_to_cpu(guid->data3),
			guid->data4[0], guid->data4[1],
			guid->data4[2], guid->data4[3], guid->data4[4],
			guid->data4[5], guid->data4[6], guid->data4[7]);
	if (res == 36)
	       return _guid_str;
	if (!guid_str)
		free(_guid_str);
	errno = EINVAL;	
	return NULL;
}

/**
 * ntfs_sid_to_mbs_size - determine maximum size for the string of a SID
 * @sid:	[IN]  SID for which to determine the maximum string size
 *
 * Determine the maximum multi byte string size in bytes which is needed to
 * store the standard textual representation of the SID pointed to by @sid.
 * See ntfs_sid_to_mbs(), below.
 *
 * On success return the maximum number of bytes needed to store the multi byte
 * string and on failure return -1 with errno set to the error code.
 */
int ntfs_sid_to_mbs_size(const SID *sid)
{
	int size, i;

	if (!ntfs_sid_is_valid(sid)) {
		errno = EINVAL;
		return -1;
	}
	/* Start with "S-". */
	size = 2;
	/*
	 * Add the SID_REVISION.  Hopefully the compiler will optimize this
	 * away as SID_REVISION is a constant.
	 */
	for (i = SID_REVISION; i > 0; i /= 10)
		size++;
	/* Add the "-". */
	size++;
	/*
	 * Add the identifier authority.  If it needs to be in decimal, the
	 * maximum is 2^32-1 = 4294967295 = 10 characters.  If it needs to be
	 * in hexadecimal, then maximum is 0x665544332211 = 14 characters.
	 */
	if (!sid->identifier_authority.high_part)
		size += 10;
	else
		size += 14;
	/*
	 * Finally, add the sub authorities.  For each we have a "-" followed
	 * by a decimal which can be up to 2^32-1 = 4294967295 = 10 characters.
	 */
	size += (1 + 10) * sid->sub_authority_count;
	/* We need the zero byte at the end, too. */
	size++;
	return size * sizeof(char);
}

/**
 * ntfs_sid_to_mbs - convert a SID to a multi byte string
 * @sid:		[IN]  SID to convert
 * @sid_str:		[OUT] string in which to return the SID (optional)
 * @sid_str_size:	[IN]  size in bytes of @sid_str
 *
 * Convert the SID pointed to by @sid to its standard textual representation.
 * @sid_str (if not NULL) needs to be able to store at least
 * ntfs_sid_to_mbs_size() bytes.  @sid_str_size is the size in bytes of
 * @sid_str if @sid_str is not NULL.
 *
 * The standard textual representation of the SID is of the form:
 *	S-R-I-S-S...
 * Where:
 *    - The first "S" is the literal character 'S' identifying the following
 *	digits as a SID.
 *    - R is the revision level of the SID expressed as a sequence of digits
 *	in decimal.
 *    - I is the 48-bit identifier_authority, expressed as digits in decimal,
 *	if I < 2^32, or hexadecimal prefixed by "0x", if I >= 2^32.
 *    - S... is one or more sub_authority values, expressed as digits in
 *	decimal.
 *
 * If @sid_str is not NULL it will contain the converted SUID on return.  If it
 * is NULL a string will be allocated and this will be returned.  The caller is
 * responsible for free()ing the string in that case.
 *
 * On success return the converted string and on failure return NULL with errno
 * set to the error code.
 */
char *ntfs_sid_to_mbs(const SID *sid, char *sid_str, size_t sid_str_size)
{
	u64 u;
	char *s;
	int i, j, cnt;

	/*
	 * No need to check @sid if !@sid_str since ntfs_sid_to_mbs_size() will
	 * check @sid, too.  8 is the minimum SID string size.
	 */
	if (sid_str && (sid_str_size < 8 || !ntfs_sid_is_valid(sid))) {
		errno = EINVAL;
		return NULL;
	}
	/* Allocate string if not provided. */
	if (!sid_str) {
		cnt = ntfs_sid_to_mbs_size(sid);
		if (cnt < 0)
			return NULL;
		s = malloc(cnt);
		if (!s)
			return s;
		sid_str = s;
		/* So we know we allocated it. */
		sid_str_size = 0;
	} else {
		s = sid_str;
		cnt = sid_str_size;
	}
	/* Start with "S-R-". */
	i = snprintf(s, cnt, "S-%hhu-", (unsigned char)sid->revision);
	if (i < 0 || i >= cnt)
		goto err_out;
	s += i;
	cnt -= i;
	/* Add the identifier authority. */
	for (u = i = 0, j = 40; i < 6; i++, j -= 8)
		u += (u64)sid->identifier_authority.value[i] << j;
	if (!sid->identifier_authority.high_part)
		i = snprintf(s, cnt, "%lu", (unsigned long)u);
	else
		i = snprintf(s, cnt, "0x%llx", (unsigned long long)u);
	if (i < 0 || i >= cnt)
		goto err_out;
	s += i;
	cnt -= i;
	/* Finally, add the sub authorities. */
	for (j = 0; j < sid->sub_authority_count; j++) {
		i = snprintf(s, cnt, "-%u", (unsigned int)
				le32_to_cpu(sid->sub_authority[j]));
		if (i < 0 || i >= cnt)
			goto err_out;
		s += i;
		cnt -= i;
	}
	return sid_str;
err_out:
	if (i >= cnt)
		i = EMSGSIZE;
	else
		i = errno;
	if (!sid_str_size)
		free(sid_str);
	errno = i;
	return NULL;
}