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Fat Mach-O support #7

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Fat Mach-O support #7

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46 changes: 41 additions & 5 deletions unfairplay.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,9 @@
#include <stdint.h>
#include <stdbool.h>
#include <mach-o/loader.h>
#include <mach-o/fat.h>

#define SWAP32(x) (((x & 0xff000000) >> 24) | ((x & 0x00ff0000) >> 8) | ((x & 0x0000ff00) << 8) | ((x & 0x000000ff) << 24))

extern int mremap_encrypted(void*, size_t, uint32_t, uint32_t, uint32_t);

Expand Down Expand Up @@ -56,8 +59,8 @@ int copy(const char* src, const char* dest) {
return result;
}

static int unprotect(int f, uint8_t *dupe, struct encryption_info_command_64 *info) {
void *base = mmap(NULL, info->cryptsize, PROT_READ | PROT_EXEC, MAP_PRIVATE, f, info->cryptoff);
static int unprotect(int f, uint64_t fileoff, uint8_t *dupe, struct encryption_info_command_64 *info) {
void *base = mmap(NULL, info->cryptsize, PROT_READ | PROT_EXEC, MAP_PRIVATE, f, fileoff + info->cryptoff);
if (base == MAP_FAILED) {
perror("mmap");
return 1;
Expand Down Expand Up @@ -143,6 +146,39 @@ int main(int argc, char* argv[]) {
return 1;
}

uint8_t *real_base = base;
size_t real_base_size = base_size;
uint8_t *real_dupe = dupe;
size_t real_dupe_size = dupe_size;

uint64_t fileoff = 0;
if(*(uint32_t*)base == FAT_CIGAM)
{
struct fat_header *fh = (struct fat_header*)base;
struct fat_arch *arch = (struct fat_arch*)(fh + 1);
for(size_t i = 0; i < SWAP32(fh->nfat_arch); ++i)
{
if(SWAP32(arch[i].cputype) == CPU_TYPE_ARM64 && SWAP32(arch[i].cpusubtype) == CPU_SUBTYPE_ARM64_ALL)
{
uint32_t offset = SWAP32(arch[i].offset);
uint32_t size = SWAP32(arch[i].size);
assert(offset < base_size);
assert(size <= base_size - offset);
base += offset;
dupe += offset;
base_size = size;
dupe_size = size;
fileoff = offset;
break;
}
}
if(!fileoff)
{
printf("Failed to find arm64 slice.\n");
return 1;
}
}

struct mach_header_64* header = (struct mach_header_64*) base;
assert(header->magic == MH_MAGIC_64);
assert(header->cputype == CPU_TYPE_ARM64);
Expand All @@ -162,7 +198,7 @@ int main(int argc, char* argv[]) {
// If "unprotect"'ing is successful, then change the "cryptid" so that
// the loader does not attempt to decrypt decrypted pages.
//
if (unprotect(f, dupe, encryption_info) == 0) {
if (unprotect(f, fileoff, dupe, encryption_info) == 0) {
encryption_info = (struct encryption_info_command_64*) (dupe + offset);
encryption_info->cryptid = 0;
}
Expand All @@ -175,8 +211,8 @@ int main(int argc, char* argv[]) {
offset += command->cmdsize;
}

munmap(base, base_size);
munmap(dupe, dupe_size);
munmap(real_base, real_base_size);
munmap(real_dupe, real_dupe_size);

printf("Succeeded in decrypting the binary.\n");

Expand Down