Attach.mm

/*
 *  Attach.mm
 *  MachOView
 *
 *  Created by fG! on 08/09/13.
 *  reverser@put.as
 *
 *  Contains functions for the attach to process feature.
 *
 */

#include "Attach.h"

#include <stdio.h>

/* local functions */
static kern_return_t readmem(mach_vm_offset_t *buffer, mach_vm_address_t address, mach_vm_size_t size, pid_t pid, vm_region_basic_info_data_64_t *info);

#pragma mark Public functions

/*
 * find main binary by iterating memory region
 * assumes there's only one binary with filetype == MH_EXECUTE
 */
kern_return_t
find_main_binary(pid_t pid, mach_vm_address_t *main_address)
{
  vm_map_t targetTask = 0;
  kern_return_t kr = 0;
  if (task_for_pid(mach_task_self(), pid, &targetTask))
  {
    NSLog(@"[ERROR] Can't execute task_for_pid! Do you have the right permissions/entitlements?\n");
    return KERN_FAILURE;
  }
  
  vm_address_t iter = 0;
  while (1)
  {
    struct mach_header mh = {0};
    vm_address_t addr = iter;
    vm_size_t lsize = 0;
    uint32_t depth;
    mach_vm_size_t bytes_read = 0;
    struct vm_region_submap_info_64 info;
    mach_msg_type_number_t count = VM_REGION_SUBMAP_INFO_COUNT_64;
    if (vm_region_recurse_64(targetTask, &addr, &lsize, &depth, (vm_region_info_t)&info, &count))
    {
      break;
    }
    kr = mach_vm_read_overwrite(targetTask, (mach_vm_address_t)addr, (mach_vm_size_t)sizeof(struct mach_header), (mach_vm_address_t)&mh, &bytes_read);
    if (kr == KERN_SUCCESS && bytes_read == sizeof(struct mach_header))
    {
      /* only one image with MH_EXECUTE filetype */
      if ( (mh.magic == MH_MAGIC || mh.magic == MH_MAGIC_64) && mh.filetype == MH_EXECUTE)
      {
#if DEBUG
        NSLog(@"Found main binary mach-o image @ %p!\n", (void*)addr);
#endif
        *main_address = addr;
        break;
      }
    }
    iter = addr + lsize;
  }
  return KERN_SUCCESS;
}

/*
 * we need to find the binary file size
 * which is taken from the filesize field of each segment command
 * and not the vmsize (because of alignment)
 * if we dump using vmaddresses, we will get the alignment space into the dumped
 * binary and get into problems :-)
 */
int64_t
get_image_size(mach_vm_address_t address, pid_t pid, uint64_t *vmaddr_slide)
{
  vm_region_basic_info_data_64_t region_info = {0};
  // allocate a buffer to read the header info
  // NOTE: this is not exactly correct since the 64bit version has an extra 4 bytes
  // but this will work for this purpose so no need for more complexity!
  struct mach_header header = {0};
  if (readmem((mach_vm_offset_t*)&header, address, sizeof(struct mach_header), pid, &region_info))
  {
    NSLog(@"Can't read header!");
    return -1;
  }
  
  if (header.magic != MH_MAGIC && header.magic != MH_MAGIC_64)
  {
		printf("[ERROR] Target is not a mach-o binary!\n");
    return -1;
  }
  
  int64_t imagefilesize = -1;
  /* read the load commands */
  uint8_t *loadcmds = (uint8_t*)malloc(header.sizeofcmds);
  uint16_t mach_header_size = sizeof(struct mach_header);
  if (header.magic == MH_MAGIC_64)
  {
    mach_header_size = sizeof(struct mach_header_64);
  }
  if (readmem((mach_vm_offset_t*)loadcmds, address+mach_header_size, header.sizeofcmds, pid, &region_info))
  {
    NSLog(@"Can't read load commands");
    free(loadcmds);
    return -1;
  }
  
  /* process and retrieve address and size of linkedit */
  uint8_t *loadCmdAddress = 0;
  loadCmdAddress = (uint8_t*)loadcmds;
  struct load_command *loadCommand    = NULL;
  struct segment_command *segCmd      = NULL;
  struct segment_command_64 *segCmd64 = NULL;
  for (uint32_t i = 0; i < header.ncmds; i++)
  {
    loadCommand = (struct load_command*)loadCmdAddress;
    if (loadCommand->cmd == LC_SEGMENT)
    {
      segCmd = (struct segment_command*)loadCmdAddress;
      if (strncmp(segCmd->segname, "__PAGEZERO", 16) != 0)
      {
        if (strncmp(segCmd->segname, "__TEXT", 16) == 0)
        {
          *vmaddr_slide = address - segCmd->vmaddr;
        }
        imagefilesize += segCmd->filesize;
      }
    }
    else if (loadCommand->cmd == LC_SEGMENT_64)
    {
      segCmd64 = (struct segment_command_64*)loadCmdAddress;
      if (strncmp(segCmd64->segname, "__PAGEZERO", 16) != 0)
      {
        if (strncmp(segCmd64->segname, "__TEXT", 16) == 0)
        {
          *vmaddr_slide = address - segCmd64->vmaddr;
        }
        imagefilesize += segCmd64->filesize;
      }
    }
    // advance to next command
    loadCmdAddress += loadCommand->cmdsize;
  }
  free(loadcmds);
  return imagefilesize;
}

/*
 * dump the binary into the allocated buffer
 * we dump each segment and advance the buffer
 */
kern_return_t
dump_binary(mach_vm_address_t address, pid_t pid, uint8_t *buffer, uint64_t aslr_slide)
{
  vm_region_basic_info_data_64_t region_info = {0};
  // allocate a buffer to read the header info
  // NOTE: this is not exactly correct since the 64bit version has an extra 4 bytes
  // but this will work for this purpose so no need for more complexity!
  struct mach_header header = {0};
  if (readmem((mach_vm_offset_t*)&header, address, sizeof(struct mach_header), pid, &region_info))
  {
    NSLog(@"Can't read header!");
    return KERN_FAILURE;
  }
  
  if (header.magic != MH_MAGIC && header.magic != MH_MAGIC_64)
  {
    printf("[ERROR] Target is not a mach-o binary!\n");
    exit(1);
  }
  
  // read the header info to find the LINKEDIT
  uint8_t *loadcmds = (uint8_t*)malloc(header.sizeofcmds);
  
  uint16_t mach_header_size = sizeof(struct mach_header);
  if (header.magic == MH_MAGIC_64)
  {
    mach_header_size = sizeof(struct mach_header_64);
  }
  // retrieve the load commands
  if (readmem((mach_vm_offset_t*)loadcmds, address+mach_header_size, header.sizeofcmds, pid, &region_info))
  {
    NSLog(@"Can't read load commands");
    free(loadcmds);
    loadcmds = NULL;
    return KERN_FAILURE;
  }
  
  // process and retrieve address and size of linkedit
  uint8_t *loadCmdAddress = 0;
  loadCmdAddress = (uint8_t*)loadcmds;
  struct load_command *loadCommand    = NULL;
  struct segment_command *segCmd      = NULL;
  struct segment_command_64 *segCmd64 = NULL;
  for (uint32_t i = 0; i < header.ncmds; i++)
  {
    loadCommand = (struct load_command*)loadCmdAddress;
    if (loadCommand->cmd == LC_SEGMENT)
    {
      segCmd = (struct segment_command*)loadCmdAddress;
      if (strncmp(segCmd->segname, "__PAGEZERO", 16) != 0)
      {
#if DEBUG
        printf("[DEBUG] Dumping %s at %llx with size %x (buffer:%x)\n", segCmd->segname, segCmd->vmaddr+aslr_slide, segCmd->filesize, (uint32_t)*buffer);
#endif
        readmem((mach_vm_offset_t*)buffer, segCmd->vmaddr+aslr_slide, segCmd->filesize, pid, &region_info);
      }
      buffer += segCmd->filesize;
    }
    else if (loadCommand->cmd == LC_SEGMENT_64)
    {
      segCmd64 = (struct segment_command_64*)loadCmdAddress;
      if (strncmp(segCmd64->segname, "__PAGEZERO", 16) != 0)
      {
#if DEBUG
        printf("[DEBUG] Dumping %s at %llx with size %llx (buffer:%x)\n", segCmd64->segname, segCmd64->vmaddr+aslr_slide, segCmd64->filesize, (uint32_t)*buffer);
#endif
        readmem((mach_vm_offset_t*)buffer, segCmd64->vmaddr+aslr_slide, segCmd64->filesize, pid, &region_info);
      }
      buffer += segCmd64->filesize;
    }
    // advance to next command
    loadCmdAddress += loadCommand->cmdsize;
  }
  free(loadcmds);
  loadcmds = NULL;
  return KERN_SUCCESS;
}

#pragma mark Local functions

static kern_return_t
readmem(mach_vm_offset_t *buffer, mach_vm_address_t address, mach_vm_size_t size, pid_t pid, vm_region_basic_info_data_64_t *info)
{
  // get task for pid
  vm_map_t port;
  
  kern_return_t kr;
  //#if DEBUG
  //    printf("[DEBUG] Readmem of address %llx to buffer %llx with size %llx\n", address, buffer, size);
  //#endif
  if (task_for_pid(mach_task_self(), pid, &port))
  {
    fprintf(stderr, "[ERROR] Can't execute task_for_pid! Do you have the right permissions/entitlements?\n");
    return KERN_FAILURE;
  }
  
  mach_msg_type_number_t info_cnt = sizeof (vm_region_basic_info_data_64_t);
  mach_port_t object_name;
  mach_vm_size_t size_info;
  mach_vm_address_t address_info = address;
  kr = mach_vm_region(port, &address_info, &size_info, VM_REGION_BASIC_INFO_64, (vm_region_info_t)info, &info_cnt, &object_name);
  if (kr)
  {
    fprintf(stderr, "[ERROR] mach_vm_region failed with error %d\n", (int)kr);
    return KERN_FAILURE;
  }
  
  /* read memory - vm_read_overwrite because we supply the buffer */
  mach_vm_size_t nread;
  kr = mach_vm_read_overwrite(port, address, size, (mach_vm_address_t)buffer, &nread);
  if (kr)
  {
    fprintf(stderr, "[ERROR] vm_read failed! %d\n", kr);
    return KERN_FAILURE;
  }
  else if (nread != size)
  {
    fprintf(stderr, "[ERROR] vm_read failed! requested size: 0x%llx read: 0x%llx\n", size, nread);
    return KERN_FAILURE;
  }
  return KERN_SUCCESS;
}