/*

Copyright (c) 2007-2021. The YARA Authors. All Rights Reserved.

Redistribution and use in source and binary forms, with or without modification,

are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this

list of conditions and the following disclaimer.

2. 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.

3. Neither the name of the copyright holder 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.

*/

#if defined(USE_LINUX_PROC)

#include <assert.h>

#include <errno.h>

#include <fcntl.h>

#include <inttypes.h>

#include <sys/mman.h>

#include <sys/stat.h>

#include <sys/sysmacros.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <unistd.h>

#include <yara/error.h>

#include <yara/globals.h>

#include <yara/libyara.h>

#include <yara/mem.h>

#include <yara/proc.h>

#include <yara/strutils.h>

typedef struct _YR_PROC_INFO

{

  int pid;

  int mem_fd;

  int pagemap_fd;

  FILE* maps;

  uint64_t map_offset;

  uint64_t next_block_end;

  int page_size;

  char map_path[PATH_MAX];

  uint64_t map_dmaj;

  uint64_t map_dmin;

  uint64_t map_ino;

} YR_PROC_INFO;

static int page_size = -1;

int _yr_process_attach(int pid, YR_PROC_ITERATOR_CTX* context)

{

  char buffer[256];

  page_size = sysconf(_SC_PAGE_SIZE);

  if (page_size < 0)

    page_size = 4096;

  YR_PROC_INFO* proc_info = (YR_PROC_INFO*) yr_malloc(sizeof(YR_PROC_INFO));

  if (proc_info == NULL)

    return ERROR_INSUFFICIENT_MEMORY;

  proc_info->pid = pid;

  proc_info->maps = NULL;

  proc_info->mem_fd = -1;

  proc_info->pagemap_fd = -1;

  proc_info->next_block_end = 0;

  snprintf(buffer, sizeof(buffer), "/proc/%u/maps", pid);

  proc_info->maps = fopen(buffer, "r");

  if (proc_info->maps == NULL)

    goto err;

  snprintf(buffer, sizeof(buffer), "/proc/%u/mem", pid);

  proc_info->mem_fd = open(buffer, O_RDONLY);

  if (proc_info->mem_fd == -1)

    goto err;

  snprintf(buffer, sizeof(buffer), "/proc/%u/pagemap", pid);

  proc_info->pagemap_fd = open(buffer, O_RDONLY);

  if (proc_info->mem_fd == -1)

    goto err;

  context->proc_info = proc_info;

  return ERROR_SUCCESS;

err:

  if (proc_info)

  {

    if (proc_info->pagemap_fd != -1)

      close(proc_info->pagemap_fd);

    if (proc_info->mem_fd != -1)

      close(proc_info->mem_fd);

    if (proc_info->maps != NULL)

      fclose(proc_info->maps);

    yr_free(proc_info);

  }

  return ERROR_COULD_NOT_ATTACH_TO_PROCESS;

}

int _yr_process_detach(YR_PROC_ITERATOR_CTX* context)

{

  YR_PROC_INFO* proc_info = (YR_PROC_INFO*) context->proc_info;

  if (proc_info)

  {

    fclose(proc_info->maps);

    close(proc_info->mem_fd);

    close(proc_info->pagemap_fd);

  }

  if (context->buffer != NULL)

  {

    munmap((void*) context->buffer, context->buffer_size);

    context->buffer = NULL;

    context->buffer_size = 0;

  }

  return ERROR_SUCCESS;

}

YR_API const uint8_t* yr_process_fetch_memory_block_data(YR_MEMORY_BLOCK* block)

{

  const uint8_t* result = NULL;

  uint64_t* pagemap = NULL;

  YR_PROC_ITERATOR_CTX* context = (YR_PROC_ITERATOR_CTX*) block->context;

  YR_PROC_INFO* proc_info = (YR_PROC_INFO*) context->proc_info;

  if (context->buffer != NULL)

  {

    munmap((void*) context->buffer, context->buffer_size);

    context->buffer = NULL;

    context->buffer_size = 0;

  }

  int fd = -2;  // Assume mapping not connected with a file.

  // Only try mapping the file if it has a path and belongs to a device

  if (strlen(proc_info->map_path) > 0 &&

      !(proc_info->map_dmaj == 0 && proc_info->map_dmin == 0))

  {

    struct stat st;

    fd = open(proc_info->map_path, O_RDONLY);

    if (fd < 0)

    {

      fd = -1;  // File does not exist.

    }

    else if (fstat(fd, &st) < 0)

    {

      // Why should stat fail after file open? Treat like missing.

      close(fd);

      fd = -1;

    }

    else if (

        (major(st.st_dev) != proc_info->map_dmaj) ||

        (minor(st.st_dev) != proc_info->map_dmin) ||

        (st.st_ino != proc_info->map_ino))

    {

      // Wrong file, may have been replaced. Treat like missing.

      close(fd);

      fd = -1;

    }

    else if (st.st_size < proc_info->map_offset + block->size)

    {

      // Mapping extends past end of file. Treat like missing.

      close(fd);

      fd = -1;

    }

    else if ((st.st_mode & S_IFMT) != S_IFREG)

    {

      // Correct filesystem object, but not a regular file. Treat like

      // uninitialized mapping.

      close(fd);

      fd = -2;

    }

  }

  if (fd >= 0)

  {

    context->buffer = mmap(

        NULL,

        block->size,

        PROT_READ | PROT_WRITE,

        MAP_PRIVATE,

        fd,

        proc_info->map_offset);

    close(fd);

  }

  else

  {

    context->buffer = mmap(

        NULL,

        block->size,

        PROT_READ | PROT_WRITE,

        MAP_PRIVATE | MAP_ANONYMOUS,

        -1,

        0);

  }

  if (context->buffer != NULL)

  {

    context->buffer_size = block->size;

  }

  else

  {

    context->buffer_size = 0;

    goto _exit;

  }

  // If mapping can't be accessed through the filesystem, read everything from

  // target process VM.

  if (fd == -1)

  {

    if (pread(

            proc_info->mem_fd,

            (void*) context->buffer,

            block->size,

            block->base) == -1)

    {

      goto _exit;

    }

  }

  else

  {

    pagemap = calloc(block->size / page_size, sizeof(uint64_t));

    if (pagemap == NULL)

    {

      goto _exit;

    }

    if (pread(

            proc_info->pagemap_fd,

            pagemap,

            sizeof(uint64_t) * block->size / page_size,

            sizeof(uint64_t) * block->base / page_size) == -1)

    {

      goto _exit;

    }

    for (uint64_t i = 0; i < block->size / page_size; i++)

    {

      if (pagemap[i] >> 61 == 0)

      {

        continue;

      }

      // Overwrite our mapping if the page is present, file-backed, or

      // swap-backed and if it differs from our mapping.

      uint8_t buffer[page_size];

      if (pread(

              proc_info->mem_fd,

              buffer,

              page_size,

              block->base + i * page_size) == -1)

      {

        goto _exit;

      }

      if (memcmp(

              (void*) context->buffer + i * page_size,

              (void*) buffer,

              page_size) != 0)

      {

        memcpy(

            (void*) context->buffer + i * page_size, (void*) buffer, page_size);

      }

    }

  }

  result = context->buffer;

_exit:;

  if (pagemap)

  {

    free(pagemap);

    pagemap = NULL;

  }

  YR_DEBUG_FPRINTF(2, stderr, "- %s() {} = %p\n", __FUNCTION__, result);

  return result;

}

YR_API YR_MEMORY_BLOCK* yr_process_get_next_memory_block(

    YR_MEMORY_BLOCK_ITERATOR* iterator)

{

  YR_PROC_ITERATOR_CTX* context = (YR_PROC_ITERATOR_CTX*) iterator->context;

  YR_PROC_INFO* proc_info = (YR_PROC_INFO*) context->proc_info;

  char buffer[PATH_MAX];

  char perm[5];

  uint64_t begin, end;

  uint64_t current_begin = context->current_block.base +

                           context->current_block.size;

  uint64_t max_process_memory_chunk;

  yr_get_configuration_uint64(

      YR_CONFIG_MAX_PROCESS_MEMORY_CHUNK, &max_process_memory_chunk);

  iterator->last_error = ERROR_SUCCESS;

  if (proc_info->next_block_end <= current_begin)

  {

    int path_start, n = 0;

    char* p;

    while (fgets(buffer, sizeof(buffer), proc_info->maps) != NULL)

    {

      // locate the '\n' character

      p = strrchr(buffer, '\n');

      // If we haven't read the whole line, skip over the rest.

      if (p == NULL)

      {

        int c;

        do

        {

          c = fgetc(proc_info->maps);

        } while (c >= 0 && c != '\n');

      }

      // otherwise remove '\n' at the end of the line

      else

      {

        *p = '\0';

      }

      // Each row in /proc/$PID/maps describes a region of contiguous virtual

      // memory in a process or thread. Each row has the following fields:

      //

      // address           perms offset  dev   inode   pathname

      // 08048000-08056000 r-xp 00000000 03:0c 64593   /usr/sbin/gpm

      //

      n = sscanf(

          buffer,

          "%" SCNx64 "-%" SCNx64 " %4s "

          "%" SCNx64 " %" SCNx64 ":%" SCNx64 " %" SCNu64 " %n",

          &begin,

          &end,

          perm,

          &(proc_info->map_offset),

          &(proc_info->map_dmaj),

          &(proc_info->map_dmin),

          &(proc_info->map_ino),

          &path_start);

      // If the row was parsed correctly sscan must return 7.

      if (n == 7)

      {

        // skip the memory region that doesn't have read permission.

        if (perm[0] != 'r')

        {

          continue;

        }

        // path_start contains the offset within buffer where the path starts,

        // the path should start with /.

        if (buffer[path_start] == '/')

          strncpy(

              proc_info->map_path,

              buffer + path_start,

              sizeof(proc_info->map_path) - 1);

        else

          proc_info->map_path[0] = '\0';

        break;

      }

    }

    if (n == 7)

    {

      current_begin = begin;

      proc_info->next_block_end = end;

    }

    else

    {

      YR_DEBUG_FPRINTF(2, stderr, "+ %s() = NULL\n", __FUNCTION__);

      return NULL;

    }

  }

  context->current_block.base = current_begin;

  context->current_block.size = yr_min(

      proc_info->next_block_end - current_begin, max_process_memory_chunk);

  assert(context->current_block.size > 0);

  YR_DEBUG_FPRINTF(

      2,

      stderr,

      "- %s() {} = %p // .base=0x%" PRIx64 " .size=%" PRIu64 "\n",

      __FUNCTION__,

      context->current_block,

      context->current_block.base,

      context->current_block.size);

  return &context->current_block;

}

YR_API YR_MEMORY_BLOCK* yr_process_get_first_memory_block(

    YR_MEMORY_BLOCK_ITERATOR* iterator)

{

  YR_DEBUG_FPRINTF(2, stderr, "+ %s() {\n", __FUNCTION__);

  YR_MEMORY_BLOCK* result = NULL;

  YR_PROC_ITERATOR_CTX* context = (YR_PROC_ITERATOR_CTX*) iterator->context;

  YR_PROC_INFO* proc_info = (YR_PROC_INFO*) context->proc_info;

  if (fseek(proc_info->maps, 0, SEEK_SET) != 0)

  {

    result = NULL;

    goto _exit;

  }

  proc_info->next_block_end = 0;

  result = yr_process_get_next_memory_block(iterator);

_exit:

  if (result == NULL)

    iterator->last_error = ERROR_COULD_NOT_READ_PROCESS_MEMORY;

  YR_DEBUG_FPRINTF(2, stderr, "} = %p // %s()\n", result, __FUNCTION__);

  return result;

}

#endif