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/*
* img4.c
* Functions for handling the new IMG4 format
*
* Copyright (c) 2013 Nikias Bassen. All Rights Reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <stdlib.h>
#include <string.h>
#include "common.h"
#include "img4.h"
#define ASN1_CONSTRUCTED 0x20
#define ASN1_SEQUENCE 0x10
#define ASN1_CONTEXT_SPECIFIC 0x80
#define ASN1_IA5_STRING 0x16
#define IMG4_MAGIC "IMG4"
#define IMG4_MAGIC_SIZE 4
static unsigned char* asn1_create_element_header(unsigned char type, unsigned int size, unsigned char** data, unsigned int *data_size)
{
unsigned char buf[6];
unsigned int off = 0;
if (!type || size == 0 || !data || !data_size) {
return NULL;
}
buf[off++] = type;
// first, calculate the size
if (size >= 0x1000000) {
// 1+4 bytes length
buf[off++] = 0x84;
buf[off++] = (size >> 24) & 0xFF;
buf[off++] = (size >> 16) & 0xFF;
buf[off++] = (size >> 8) & 0xFF;
buf[off++] = size & 0xFF;
} else if (size >= 0x10000) {
// 1+3 bytes length
buf[off++] = 0x83;
buf[off++] = (size >> 16) & 0xFF;
buf[off++] = (size >> 8) & 0xFF;
buf[off++] = size & 0xFF;
} else if (size >= 0x100) {
// 1+2 bytes length
buf[off++] = 0x82;
buf[off++] = (size >> 8) & 0xFF;
buf[off++] = (size & 0xFF);
} else if (size >= 0x80) {
// 1+1 byte length
buf[off++] = 0x81;
buf[off++] = (size & 0xFF);
} else {
// 1 byte length
buf[off++] = size & 0xFF;
}
*data = malloc(off);
memcpy(*data, buf, off);
*data_size = off;
return *data;
}
static unsigned int asn1_get_element(const unsigned char* data, unsigned char* type, unsigned char* size)
{
unsigned int off = 0;
if (!data)
return 0;
if (type)
*type = data[off++];
if (size)
*size = data[off++];
return off;
}
static const unsigned char *asn1_find_element(unsigned int index, unsigned char type, const unsigned char* data)
{
unsigned char el_type = 0;
unsigned char el_size = 0;
unsigned int off = 0;
// verify data integrity
if (data[off++] != (ASN1_CONSTRUCTED | ASN1_SEQUENCE))
return NULL;
// check data size
switch (data[off++]) {
case 0x84:
off += 4;
break;
case 0x83:
off += 3;
break;
case 0x82:
off += 2;
break;
case 0x81:
off += 1;
break;
default:
break;
}
// find the element we are searching
for (int i = 0; i <= index; i++) {
off += asn1_get_element(&data[off], &el_type, &el_size);
if (i == index)
break;
off += el_size;
}
// check element type
if (el_type != type)
return NULL;
return &data[off];
}
int img4_stitch_component(const char* component_name, const unsigned char* component_data, unsigned int component_size, const unsigned char* blob, unsigned int blob_size, unsigned char** img4_data, unsigned int *img4_size)
{
unsigned char* magic_header = NULL;
unsigned int magic_header_size = 0;
unsigned char* blob_header = NULL;
unsigned int blob_header_size = 0;
unsigned char* img4header = NULL;
unsigned int img4header_size = 0;
unsigned int content_size;
unsigned char* outbuf;
unsigned char* p;
if (!component_name || !component_data || component_size == 0 || !blob || blob_size == 0 || !img4_data || !img4_size) {
return -1;
}
info("Personalizing IMG4 component %s...\n", component_name);
/* first we need check if we have to change the tag for the given component */
const void *tag = asn1_find_element(1, ASN1_IA5_STRING, component_data);
if (tag) {
debug("Tag found\n");
if (strcmp(component_name, "RestoreKernelCache") == 0) {
memcpy((void*)tag, "rkrn", 4);
} else if (strcmp(component_name, "RestoreDeviceTree") == 0) {
memcpy((void*)tag, "rdtr", 4);
} else if (strcmp(component_name, "RestoreSEP") == 0) {
memcpy((void*)tag, "rsep", 4);
} else if (strcmp(component_name, "AppleLogo") == 0) {
memcpy((void*)tag, "rlgo", 4);
}
}
// create element header for the "IMG4" magic
asn1_create_element_header(ASN1_IA5_STRING, IMG4_MAGIC_SIZE, &magic_header, &magic_header_size);
// create element header for the blob (ApImg4Ticket)
asn1_create_element_header(ASN1_CONTEXT_SPECIFIC|ASN1_CONSTRUCTED, blob_size, &blob_header, &blob_header_size);
// calculate the size for the final IMG4 file (asn1 sequence)
content_size = magic_header_size + IMG4_MAGIC_SIZE + component_size + blob_header_size + blob_size;
// create element header for the final IMG4 asn1 blob
asn1_create_element_header(ASN1_SEQUENCE|ASN1_CONSTRUCTED, content_size, &img4header, &img4header_size);
outbuf = (unsigned char*)malloc(img4header_size + content_size);
if (!outbuf) {
if (magic_header) {
free(magic_header);
}
if (blob_header) {
free(blob_header);
}
if (img4header) {
free(img4header);
}
error("ERROR: out of memory when personalizing IMG4 component %s\n", component_name);
return -1;
}
p = outbuf;
// now put everything together
memcpy(p, img4header, img4header_size);
p += img4header_size;
memcpy(p, magic_header, magic_header_size);
p += magic_header_size;
memcpy(p, IMG4_MAGIC, IMG4_MAGIC_SIZE);
p += IMG4_MAGIC_SIZE;
memcpy(p, component_data, component_size);
p += component_size;
memcpy(p, blob_header, blob_header_size);
p += blob_header_size;
memcpy(p, blob, blob_size);
p += blob_size;
*img4_data = outbuf;
*img4_size = (p - outbuf);
if (magic_header) {
free(magic_header);
}
if (blob_header) {
free(blob_header);
}
if (img4header) {
free(img4header);
}
return 0;
}
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