Magisk/jni/extract.c

150 lines
3.7 KiB
C
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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sendfile.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <assert.h>
#include <string.h>
#include "bootimgtools.h"
void dump(uint8_t *ptr, size_t size, char* filename) {
unlink(filename);
int ofd = open(filename, O_WRONLY|O_CREAT, 0644);
assert(ofd >= 0);
int ret = write(ofd, ptr, size);
assert(ret == size);
close(ofd);
}
//TODO: Search for other header types
void dump_ramdisk(uint8_t *ptr, size_t size) {
//GZip header
if(memcmp(ptr, "\x1f\x8b\x08\x00", 4) == 0) {
dump(ptr, size, "ramdisk.gz");
//MTK header
} else if(memcmp(ptr, "\x88\x16\x88\x58", 4) == 0) {
if(memcmp(ptr+8, "RECOVERY", 8)==0) {
dump(ptr, 0, "ramdisk-mtk-recovery");
} else if(memcmp(ptr+8, "ROOTFS\0\0", 8)==0) {
dump(ptr, 0, "ramdisk-mtk-boot");
} else {
exit(1);
}
dump(ptr, 0, "ramdisk-mtk"); //Create an mtk flag
dump_ramdisk(ptr+512, size-512);
} else {
//Since our first aim is to extract/repack ramdisk
//Stop if we can't find it
//Still dump it for debug purposes
dump(ptr, size, "ramdisk");
fprintf(stderr, "Unknown ramdisk type\n");
abort();
}
}
void search_security_hdr(uint8_t *buf, size_t size) {
if(memcmp(buf, "CHROMEOS", 8) == 0) {
dump(buf, 0, "chromeos");
return;
}
}
int search_security(uint8_t *buf, size_t size, int pos) {
//Rockchip signature
if(memcmp(buf+1024, "SIGN", 4) == 0) {
//Rockchip signature AT LEAST means the bootloader will check the crc
dump(buf, 0, "rkcrc"); //Create an flag to tell it
//And it's possible there is a security too
return 1;
}
//If we didn't parse the whole file, it is highly likely there is a boot signature
if(pos < size) {
return 1;
}
return 0;
}
/*
* TODO:
* - At the moment we dump kernel + ramdisk + second + DT, it's likely we only want ramdisk
* - Error-handling via assert() is perhaps not the best
*/
int extract(char *image) {
int fd = open(image, O_RDONLY);
off_t size = lseek(fd, 0, SEEK_END);
lseek(fd, 0, SEEK_SET);
uint8_t *orig = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0);
uint8_t *base = orig;
assert(base);
search_security_hdr(base, size);
//We're searching for the header in the whole file, we could stop earlier.
//At least HTC and nVidia have a signature header
while(base<(orig+size)) {
if(memcmp(base, BOOT_MAGIC, BOOT_MAGIC_SIZE) == 0)
break;
//We're searching every 256bytes, is it ok?
base += 256;
}
assert(base < (orig+size));
struct boot_img_hdr *hdr = (struct boot_img_hdr*) base;
assert(
hdr->page_size == 2048 ||
hdr->page_size == 4096 ||
hdr->page_size == 16384
);
long pos = hdr->page_size;
dump(base+pos, hdr->kernel_size, "kernel");
pos += hdr->kernel_size + hdr->page_size-1;
pos &= ~(hdr->page_size-1L);
dump_ramdisk(base+pos, hdr->ramdisk_size);
pos += hdr->ramdisk_size + hdr->page_size-1;
pos &= ~(hdr->page_size-1L);
if(hdr->second_size) {
assert( (pos+hdr->second_size) <= size);
dump(base+pos, hdr->second_size, "second");
pos += hdr->second_size + hdr->page_size-1;
pos &= ~(hdr->page_size-1L);
}
//This is non-standard, so we triple check
if( hdr->unused[0] &&
pos < size &&
(pos+hdr->unused[0]) <= size) {
if(memcmp(base+pos, "QCDT", 4) == 0 ||
memcmp(base+pos, "SPRD", 4) == 0 ||
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memcmp(base+pos, "DTBH", 4) == 0 ||
memcmp(base+pos, "\xD0\x0D\xFE\xED", 4) == 0
) {
dump(base+pos, hdr->unused[0], "dt");
pos += hdr->unused[0] + hdr->page_size-1;
pos &= ~(hdr->page_size-1L);
}
}
//If we think we find some security-related infos in the boot.img
//create a "secure" flag to warn the user it is dangerous
if(search_security(base, size, pos)) {
dump(base, 0, "secure");
}
munmap(orig, size);
close(fd);
return 0;
}