// Copyright (c) 2013, Facebook, Inc.
// All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * 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.
// * Neither the name Facebook nor the names of its contributors may be used to
// endorse or promote products derived from this software without specific
// prior written permission.
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
#include "fishhook.h"
#include <dlfcn.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <mach/mach.h>
#include <mach/vm_map.h>
#include <mach/vm_region.h>
#include <mach-o/dyld.h>
#include <mach-o/loader.h>
#include <mach-o/nlist.h>
#include <pthread.h>
#ifdef __LP64__
typedef struct mach_header_64 mach_header_t;
typedef struct segment_command_64 segment_command_t;
typedef struct section_64 section_t;
typedef struct nlist_64 nlist_t;
#define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT_64
#else
typedef struct mach_header mach_header_t;
typedef struct segment_command segment_command_t;
typedef struct section section_t;
typedef struct nlist nlist_t;
#define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT
#endif
#ifndef SEG_DATA_CONST
#define SEG_DATA_CONST "__DATA_CONST"
#endif
#ifndef SEG_AUTH_CONST
#define SEG_AUTH_CONST "__AUTH_CONST"
#endif
struct rebindings_entry {
struct rebinding *rebindings;
size_t rebindings_nel;
struct rebindings_entry *next;
};
static struct rebindings_entry *_rebindings_head;
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
static int prepend_rebindings(struct rebindings_entry **rebindings_head,
struct rebinding rebindings[],
size_t nel) {
struct rebindings_entry *new_entry = (struct rebindings_entry *) malloc(sizeof(struct rebindings_entry));
if (!new_entry) {
return -1;
}
new_entry->rebindings = (struct rebinding *) malloc(sizeof(struct rebinding) * nel);
if (!new_entry->rebindings) {
free(new_entry);
return -1;
}
memcpy(new_entry->rebindings, rebindings, sizeof(struct rebinding) * nel);
new_entry->rebindings_nel = nel;
new_entry->next = *rebindings_head;
*rebindings_head = new_entry;
return 0;
}
static vm_prot_t get_protection(void *sectionStart) {
mach_port_t task = mach_task_self();
vm_size_t size = 0;
vm_address_t address = (vm_address_t)sectionStart;
memory_object_name_t object;
#if __LP64__
mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
vm_region_basic_info_data_64_t info;
kern_return_t info_ret = vm_region_64(
task, &address, &size, VM_REGION_BASIC_INFO_64, (vm_region_info_64_t)&info, &count, &object);
#else
mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT;
vm_region_basic_info_data_t info;
kern_return_t info_ret = vm_region(task, &address, &size, VM_REGION_BASIC_INFO, (vm_region_info_t)&info, &count, &object);
#endif
if (info_ret == KERN_SUCCESS) {
return info.protection;
} else {
return VM_PROT_READ;
}
}
static void perform_rebinding_with_section(struct rebindings_entry *rebindings,
section_t *section,
intptr_t slide,
nlist_t *symtab,
char *strtab,
uint32_t *indirect_symtab) {
const bool isDataConst = strcmp(section->segname, SEG_DATA_CONST) == 0;
const bool isAuthConst = strcmp(section->segname, SEG_AUTH_CONST) == 0;
uint32_t *indirect_symbol_indices = indirect_symtab + section->reserved1;
void **indirect_symbol_bindings = (void **)((uintptr_t)slide + section->addr);
vm_prot_t oldProtection = VM_PROT_READ;
vm_size_t trunc_address = (vm_size_t)indirect_symbol_bindings;
vm_size_t trunc_size = 0;
if (isDataConst || isAuthConst) {
trunc_address = trunc_page((vm_size_t)indirect_symbol_bindings);
trunc_size =(vm_size_t)indirect_symbol_bindings -trunc_address;
pthread_mutex_lock(&mutex);
oldProtection = get_protection((void *)trunc_address);
// Use vm_protect to also set VM_PROT_COPY.
kern_return_t err = vm_protect(mach_task_self(),
(uintptr_t)trunc_address,
section->size+trunc_size,
0,
VM_PROT_READ | VM_PROT_WRITE | VM_PROT_COPY);
if (err != KERN_SUCCESS) {
fprintf(
stderr,
"perform_rebinding_with_section vm_protect failed. error code: %d, "
"trunc address: 0x%lx, trunc size: 0x%lx, section size: 0x%llx\n",
err, trunc_address, trunc_size, section->size);
pthread_mutex_unlock(&mutex);
return;
}
}
for (uint i = 0; i < section->size / sizeof(void *); i++) {
uint32_t symtab_index = indirect_symbol_indices[i];
if (symtab_index == INDIRECT_SYMBOL_ABS || symtab_index == INDIRECT_SYMBOL_LOCAL ||
symtab_index == (INDIRECT_SYMBOL_LOCAL | INDIRECT_SYMBOL_ABS)) {
continue;
}
uint32_t strtab_offset = symtab[symtab_index].n_un.n_strx;
char *symbol_name = strtab + strtab_offset;
bool symbol_name_longer_than_1 = symbol_name[0] && symbol_name[1];
struct rebindings_entry *cur = rebindings;
while (cur) {
for (uint j = 0; j < cur->rebindings_nel; j++) {
if (symbol_name_longer_than_1 &&
strcmp(&symbol_name[1], cur->rebindings[j].name) == 0) {
if (cur->rebindings[j].replaced != NULL &&
indirect_symbol_bindings[i] != cur->rebindings[j].replacement) {
*(cur->rebindings[j].replaced) = indirect_symbol_bindings[i];
}
indirect_symbol_bindings[i] = cur->rebindings[j].replacement;
goto symbol_loop;
}
}
cur = cur->next;
}
symbol_loop:;
}
if (isDataConst || isAuthConst) {
int protection = 0;
if (oldProtection & VM_PROT_READ) {
protection |= PROT_READ;
}
if (oldProtection & VM_PROT_WRITE) {
protection |= PROT_WRITE;
}
if (oldProtection & VM_PROT_EXECUTE) {
protection |= PROT_EXEC;
}
mprotect((void *)trunc_address, section->size+trunc_size, protection);
pthread_mutex_unlock(&mutex);
}
}
static void rebind_symbols_for_image(struct rebindings_entry *rebindings,
const struct mach_header *header,
intptr_t slide) {
Dl_info info;
if (dladdr(header, &info) == 0) {
return;
}
segment_command_t *cur_seg_cmd;
segment_command_t *linkedit_segment = NULL;
struct symtab_command* symtab_cmd = NULL;
struct dysymtab_command* dysymtab_cmd = NULL;
uintptr_t cur = (uintptr_t)header + sizeof(mach_header_t);
for (uint i = 0; i < header->ncmds; i++, cur += cur_seg_cmd->cmdsize) {
cur_seg_cmd = (segment_command_t *)cur;
if (cur_seg_cmd->cmd == LC_SEGMENT_ARCH_DEPENDENT) {
if (strcmp(cur_seg_cmd->segname, SEG_LINKEDIT) == 0) {
linkedit_segment = cur_seg_cmd;
}
} else if (cur_seg_cmd->cmd == LC_SYMTAB) {
symtab_cmd = (struct symtab_command*)cur_seg_cmd;
} else if (cur_seg_cmd->cmd == LC_DYSYMTAB) {
dysymtab_cmd = (struct dysymtab_command*)cur_seg_cmd;
}
}
if (!symtab_cmd || !dysymtab_cmd || !linkedit_segment ||
!dysymtab_cmd->nindirectsyms) {
return;
}
// Find base symbol/string table addresses
uintptr_t linkedit_base = (uintptr_t)slide + linkedit_segment->vmaddr - linkedit_segment->fileoff;
nlist_t *symtab = (nlist_t *)(linkedit_base + symtab_cmd->symoff);
char *strtab = (char *)(linkedit_base + symtab_cmd->stroff);
// Get indirect symbol table (array of uint32_t indices into symbol table)
uint32_t *indirect_symtab = (uint32_t *)(linkedit_base + dysymtab_cmd->indirectsymoff);
cur = (uintptr_t)header + sizeof(mach_header_t);
for (uint i = 0; i < header->ncmds; i++, cur += cur_seg_cmd->cmdsize) {
cur_seg_cmd = (segment_command_t *)cur;
if (cur_seg_cmd->cmd == LC_SEGMENT_ARCH_DEPENDENT) {
if (strcmp(cur_seg_cmd->segname, SEG_DATA) != 0 &&
strcmp(cur_seg_cmd->segname, SEG_DATA_CONST) != 0 &&
strcmp(cur_seg_cmd->segname, SEG_AUTH_CONST) != 0) {
continue;
}
for (uint j = 0; j < cur_seg_cmd->nsects; j++) {
section_t *sect =
(section_t *)(cur + sizeof(segment_command_t)) + j;
if ((sect->flags & SECTION_TYPE) == S_LAZY_SYMBOL_POINTERS) {
perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab);
}
if ((sect->flags & SECTION_TYPE) == S_NON_LAZY_SYMBOL_POINTERS) {
perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab);
}
}
}
}
}
static void _rebind_symbols_for_image(const struct mach_header *header,
intptr_t slide) {
rebind_symbols_for_image(_rebindings_head, header, slide);
}
int rebind_symbols_image(void *header,
intptr_t slide,
struct rebinding rebindings[],
size_t rebindings_nel) {
struct rebindings_entry *rebindings_head = NULL;
int retval = prepend_rebindings(&rebindings_head, rebindings, rebindings_nel);
rebind_symbols_for_image(rebindings_head, (const struct mach_header *) header, slide);
if (rebindings_head) {
free(rebindings_head->rebindings);
}
free(rebindings_head);
return retval;
}
int rebind_symbols(struct rebinding rebindings[], size_t rebindings_nel) {
int retval = prepend_rebindings(&_rebindings_head, rebindings, rebindings_nel);
if (retval < 0) {
return retval;
}
// If this was the first call, register callback for image additions (which is also invoked for
// existing images, otherwise, just run on existing images
if (!_rebindings_head->next) {
_dyld_register_func_for_add_image(_rebind_symbols_for_image);
} else {
uint32_t c = _dyld_image_count();
for (uint32_t i = 0; i < c; i++) {
_rebind_symbols_for_image(_dyld_get_image_header(i), _dyld_get_image_vmaddr_slide(i));
}
}
return retval;
}
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