/*

|  Copyright (C) 2007 Christophe Fergeau <teuf@gnome.org>

|

|  The code in this file is heavily based on the proof-of-concept code

|  written by wtbw

|

| Redistribution and use in source and binary forms, with or without

| modification, are permitted provided that the following conditions are met:

|

|   1. Redistributions of source code must retain the above copyright

| notice, this list of conditions and the following disclaimer.

|   2. Redistributions in binary form must reproduce the above copyright

| notice, this list of conditions and the following disclaimer in the

| documentation and/or other materials provided with the distribution.

|   3. The name of the author may not be used to endorse or promote

| products derived from this software without specific prior written

| permission.

|

| THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

| IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

| OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

| IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

| INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,

| BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS

| OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

| ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

| OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT

| OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY

| OF SUCH DAMAGE.

|

|

|  iTunes and iPod are trademarks of Apple

|

|  This product is not supported/written/published by Apple!

*/

#ifdef HAVE_CONFIG_H

#include <config.h>

#endif

#include <glib.h>

#include <string.h>

#include "itdb.h"

#include "db-itunes-parser.h"

#include "itdb_private.h"

static const unsigned char table1[256] = {

	0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 

	0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,

	0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 

	0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,

	0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 

	0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,

	0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 

	0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,

	0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 

	0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,

	0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 

	0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,

	0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 

	0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,

	0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 

	0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,

	0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 

	0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,

	0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 

	0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,

	0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 

	0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,

	0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 

	0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,

	0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 

	0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,

	0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 

	0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,

	0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 

	0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,

	0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 

	0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16

};

static const unsigned char table2[256] = {

	0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38, 

	0xBF, 0x40, 0xA3, 0x9E, 0x81, 0xF3, 0xD7, 0xFB,

	0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87, 

	0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB,

	0x54, 0x7B, 0x94, 0x32, 0xA6, 0xC2, 0x23, 0x3D, 

	0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,

	0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2, 

	0x76, 0x5B, 0xA2, 0x49, 0x6D, 0x8B, 0xD1, 0x25,

	0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16, 

	0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92,

	0x6C, 0x70, 0x48, 0x50, 0xFD, 0xED, 0xB9, 0xDA, 

	0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,

	0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A, 

	0xF7, 0xE4, 0x58, 0x05, 0xB8, 0xB3, 0x45, 0x06,

	0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02, 

	0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B,

	0x3A, 0x91, 0x11, 0x41, 0x4F, 0x67, 0xDC, 0xEA, 

	0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,

	0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85, 

	0xE2, 0xF9, 0x37, 0xE8, 0x1C, 0x75, 0xDF, 0x6E,

	0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89, 

	0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B,

	0xFC, 0x56, 0x3E, 0x4B, 0xC6, 0xD2, 0x79, 0x20, 

	0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,

	0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31, 

	0xB1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xEC, 0x5F,

	0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D, 

	0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF,

	0xA0, 0xE0, 0x3B, 0x4D, 0xAE, 0x2A, 0xF5, 0xB0, 

	0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,

	0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 

	0xE1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D

};

static const unsigned char fixed[18] = {

    0x67, 0x23, 0xFE, 0x30, 0x45, 0x33, 0xF8, 0x90, 0x99,

    0x21, 0x07, 0xC1, 0xD0, 0x12, 0xB2, 0xA1, 0x07, 0x81

};

#ifndef HAVE_G_CHECKSUM_RESET

#define g_checksum_reset(checksum)                      \

G_STMT_START {                                          \

    g_checksum_free(checksum);                          \

    (checksum) = g_checksum_new (G_CHECKSUM_SHA1);      \

} G_STMT_END

#endif

static int gcd(int a, int b){

    while (TRUE)

    {

        a = a % b;

        if( a == 0 )

            return b;

        b = b % a;

        if( b == 0 )

            return a;

    }

}

static int lcm(int a, int b)

{

    if(a==0 || b==0)

        return 1;

    return (a*b)/gcd(a,b);

}

static unsigned char *generate_key (const unsigned char *firewire_id)

{

    unsigned char *key;

    unsigned char y[16];

    GChecksum *checksum;

    gsize checksum_len;

    int i;

    /* take LCM of each two bytes in the FWID in turn */

    for (i=0; i<4; i++){

        int a = firewire_id[i*2];

        int b = firewire_id[i*2+1];

        int cur_lcm = lcm(a,b);

        unsigned char hi = (cur_lcm & 0xFF00) >> 8;

        unsigned char lo = cur_lcm & 0xFF;

        y[i*4    ] = table1[hi];

        y[i*4 + 1] = table2[hi];

        y[i*4 + 2] = table1[lo];

        y[i*4 + 3] = table2[lo];

    }

    /* hash */

    checksum = g_checksum_new (G_CHECKSUM_SHA1);

    g_checksum_update (checksum, fixed, sizeof (fixed));

    g_checksum_update (checksum, y, sizeof (y));

    key = g_new0 (unsigned char, 64);

    checksum_len = 64;

    g_checksum_get_digest (checksum, key, &checksum_len);

    g_checksum_free (checksum);

    return key;

}

static unsigned char *itdb_compute_hash (const unsigned char *firewire_id,

					 const unsigned char *itdb,

					 unsigned long size, 

					 gsize *len)

{

    unsigned char *key;

    unsigned char *hash;

    GChecksum *checksum;

    int i;

    const gsize CHECKSUM_LEN = g_checksum_type_get_length (G_CHECKSUM_SHA1);

    gsize digest_len;

    key = generate_key(firewire_id);

    if (key == NULL) {

	return NULL;

    }

    /* hmac sha1 */

    for (i=0; i < 64; i++)

    {

        key[i] ^= 0x36;

    }

    /* 20 bytes for the checksum, and 1 trailing \0 */

    hash = g_new0 (unsigned char, CHECKSUM_LEN+1);

    checksum = g_checksum_new (G_CHECKSUM_SHA1);

    g_checksum_update (checksum, key, 64);

    g_checksum_update (checksum, itdb, size);

    digest_len = CHECKSUM_LEN;

    g_checksum_get_digest (checksum, hash, &digest_len);

    g_assert (digest_len == CHECKSUM_LEN);

    for (i=0; i < 64; i++)

        key[i] ^= 0x36 ^ 0x5c;

    g_checksum_reset (checksum);

    g_checksum_update (checksum, key, 64);

    g_checksum_update (checksum, hash, digest_len);

    g_checksum_get_digest (checksum, hash, &digest_len);

    g_checksum_free (checksum);

    g_assert (digest_len == CHECKSUM_LEN);

    g_free (key);

    if (len != NULL) {

	*len = digest_len;

    }

    return hash;

}

gboolean itdb_hash58_write_hash (Itdb_Device *device, 

				 unsigned char *itdb_data, 

				 gsize itdb_len,

				 GError **error)

{

    unsigned char firewire_id[20];

    guchar backup18[8];

    guchar backup32[20];

    unsigned char *checksum;

    gsize len;

    MhbdHeader *header;

    g_assert (itdb_device_get_checksum_type (device) == ITDB_CHECKSUM_HASH58);

    if (!itdb_device_get_hex_uuid(device, firewire_id)) {

	g_set_error (error, 0, -1, "Couldn't find the iPod firewire ID");

	return FALSE;

    }

    if (itdb_len < 0x6c) {

	g_set_error (error, 0, -1, "iTunesDB file too small to write checksum");

	return FALSE;

    }

    header = (MhbdHeader *)itdb_data;

    g_assert (strncmp (header->header_id, "mhbd", strlen ("mhbd")) == 0);

    memcpy (backup18, &header->db_id, sizeof (backup18));

    memcpy (backup32, &header->unk_0x32, sizeof (backup32));

    /* Those fields must be zero'ed out for the sha1 calculation */

    memset(&header->db_id, 0, sizeof (header->db_id));

    memset(&header->unk_0x32, 0, sizeof (header->unk_0x32));

    memset(&header->hash58, 0, sizeof (header->hash58));

    header->hashing_scheme = GUINT16_FROM_LE (ITDB_CHECKSUM_HASH58);

    checksum = itdb_compute_hash (firewire_id, itdb_data, itdb_len, &len;;

    if (checksum == NULL) {

	g_set_error (error, 0, -1, "Failed to compute checksum");

	return FALSE;

    }

    g_assert (len <= sizeof (header->hash58));

    memcpy (&header->hash58, checksum, len);

    g_free (checksum);

    memcpy (&header->db_id, backup18, sizeof (backup18));

    memcpy (&header->unk_0x32, backup32, sizeof (backup32));

    return TRUE;

}