Replace import DLL name.

peirep.c

/*
 * Replace import DLL name.
 *
 * XXX: 32bit only
 *
 * Usage:
 *   peirep.exe /replace msvcrt.dll msvcr100.dll app.exe out.exe
 *
 * Reference:
 * http://msdn.microsoft.com/msdnmag/issues/02/03/PE2/default.aspx
 * http://forums.belution.com/ja/vc/000/234/78s.shtml
 * http://nienie.com/~masapico/api_ImageDirectoryEntryToData.html
 * http://www.geocities.jp/i96815/windows/win09.html
 * http://hp.vector.co.jp/authors/VA050396/index.html
 */

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#define TO_DOS_HEADER(base) ((PIMAGE_DOS_HEADER)(base))
#define TO_NT_HEADERS(base) ((PIMAGE_NT_HEADERS)((LPBYTE)(base) + TO_DOS_HEADER(base)->e_lfanew))

/* VC8/include/delayimp.h */
#if !defined(_DELAY_IMP_VER)
typedef DWORD                       RVA;

typedef struct ImgDelayDescr {
    DWORD           grAttrs;        // attributes
    RVA             rvaDLLName;     // RVA to dll name
    RVA             rvaHmod;        // RVA of module handle
    RVA             rvaIAT;         // RVA of the IAT
    RVA             rvaINT;         // RVA of the INT
    RVA             rvaBoundIAT;    // RVA of the optional bound IAT
    RVA             rvaUnloadIAT;   // RVA of optional copy of original IAT
    DWORD           dwTimeStamp;    // 0 if not bound,
                                    // O.W. date/time stamp of DLL bound to (Old BIND)
    } ImgDelayDescr, * PImgDelayDescr;

enum DLAttr {                   // Delay Load Attributes
    dlattrRva = 0x1,                // RVAs are used instead of pointers
                                    // Having this set indicates a VC7.0
                                    // and above delay load descriptor.
    };
#endif
static void *memmem(const void *haystack, size_t haystacklen, const void *needle, size_t needlelen);
static size_t fgetsize(FILE *f);
static int read_file(const char *path, char **pbuf, size_t *psize);
static int write_file(const char *path, char *buf, size_t size);
static char *rva_to_ptr(char *base, RVA rva);
static void replace_import_dll_name(const char *modulepath, const char *fromname, const char *toname, const char *outpath);

static void *
memmem(const void *haystack, size_t haystacklen, const void *needle, size_t needlelen)
{
  const char *a = haystack;
  const char *b = needle;
  size_t i;

  if (haystacklen == 0 || needlelen == 0)
    return (void *)haystack;

  for (i = 0; i + needlelen <= haystacklen; ++i) {
    if (a[i] == b[0] && memcmp(&a[i], needle, needlelen) == 0)
      return (void *)&a[i];
  }

  return NULL;
}

static size_t
fgetsize(FILE *f)
{
  fpos_t cur;
  fpos_t end;

  if (fgetpos(f, &cur) != 0)
    return (size_t)-1;

  if (fseek(f, 0L, SEEK_END) != 0)
    return (size_t)-1;

  if (fgetpos(f, &end) != 0)
    return (size_t)-1;

  if (fsetpos(f, &cur) != 0)
    return (size_t)-1;

  return (size_t)end;
}

static int
read_file(const char *path, char **pbuf, size_t *psize)
{
  FILE *f;
  size_t size;
  char *buf;

  f = fopen(path, "rb");
  if (f == NULL)
    return -1;

  size = fgetsize(f);
  if (size == (size_t)-1) {
    fclose(f);
    return -1;
  }

  buf = malloc(size);
  if (buf == NULL) {
    fclose(f);
    return -1;
  }

  if (fread(buf, 1, size, f) != size) {
    fclose(f);
    free(buf);
    return -1;
  }

  fclose(f);

  *pbuf = buf;
  *psize = size;

  return 0;
}

static int
write_file(const char *path, char *buf, size_t size)
{
  FILE *f;

  f = fopen(path, "wb");
  if (f == NULL)
    return -1;

  if (fwrite(buf, 1, size, f) != size) {
    fclose(f);
    return -1;
  }

  fclose(f);

  return 0;
}

static char *
rva_to_ptr(char *base, RVA rva)
{
  PIMAGE_DATA_DIRECTORY dir;
  PIMAGE_SECTION_HEADER psec;
  DWORD i;

  dir = TO_NT_HEADERS(base)->OptionalHeader.DataDirectory
    + IMAGE_DIRECTORY_ENTRY_IMPORT;

  psec = (PIMAGE_SECTION_HEADER)(TO_NT_HEADERS(base) + 1);

  for (i = 0; i < TO_NT_HEADERS(base)->FileHeader.NumberOfSections; i++) {
    if (psec[i].VirtualAddress <= rva
        && rva < psec[i].VirtualAddress + psec[i].SizeOfRawData) {
      return base + rva + (psec[i].PointerToRawData - psec[i].VirtualAddress);
    }
  }

  return NULL;
}

static void
replace_import_dll_name(const char *modulepath, const char *fromname, const char *toname, const char *outpath)
{
  char *p;
  size_t size;
  PIMAGE_DOS_HEADER pdos;
  PIMAGE_NT_HEADERS pnt;
  PIMAGE_SECTION_HEADER psec;
  DWORD i;
  char *pname;
  char tmpbuf[1024];
  size_t tmpsize;
  RVA tonamerva;
  PIMAGE_IMPORT_DESCRIPTOR Imp;
  PIMAGE_DATA_DIRECTORY dir;
  int off;

  if (read_file(modulepath, &p, &size) != 0)
    return;

  // check dos header
  pdos = TO_DOS_HEADER(p);
  if (pdos->e_magic != IMAGE_DOS_SIGNATURE || pdos->e_lfanew == 0) {
    free(p);
    return; // not executable file
  }

  // check nt header
  pnt = TO_NT_HEADERS(p);
  if (pnt->Signature != IMAGE_NT_SIGNATURE
      || pnt->OptionalHeader.Magic != IMAGE_NT_OPTIONAL_HDR32_MAGIC) {
    free(p);
    return; // not PE file
  }

  // get section table
  psec = (PIMAGE_SECTION_HEADER)(pnt + 1);

  pname = NULL;
  // add new name if not exists
  // XXX: do not work when there is extra space.
  for (i = 0; i < pnt->FileHeader.NumberOfSections; i++) {
    if (strcmp(psec[i].Name, ".rdata") == 0) {
      tmpsize = strlen(toname) + 2;
      tmpbuf[0] = 0;
      strcpy(&tmpbuf[1], toname);
      tmpbuf[tmpsize - 1] = 0;
      pname = memmem(&p[psec[i].PointerToRawData], psec[i].SizeOfRawData,
          tmpbuf, tmpsize);
      if (pname == NULL) {
        pname = &p[psec[i].PointerToRawData] + psec[i].SizeOfRawData;
        memcpy(pname, tmpbuf, tmpsize);
        psec[i].SizeOfRawData += tmpsize;
      }
      ++pname;
      tonamerva = psec[i].VirtualAddress
        + (pname - &p[psec[i].PointerToRawData]);
      break;
    }
  }

  if (pname == NULL)
    return;

  dir = pnt->OptionalHeader.DataDirectory + IMAGE_DIRECTORY_ENTRY_IMPORT;

  Imp = (PIMAGE_IMPORT_DESCRIPTOR)rva_to_ptr(p, dir->VirtualAddress);

  for ( ; Imp->OriginalFirstThunk != 0; ++Imp) {
    if (stricmp(rva_to_ptr(p, Imp->Name), fromname) == 0)
      Imp->Name = tonamerva;
  }

  write_file(outpath, p, size);

  free(p);
}

int
main(int argc, char **argv)
{
  DWORD_PTR Base;
  if (argc == 6 && stricmp(argv[1] + 1, "REPLACE") == 0) {
    replace_import_dll_name(argv[4], argv[2], argv[3], argv[5]);
  } else {
    printf("usage: %s [option] [file]\n", argv[0]);
    printf("\n");
    printf("      /REPLACE fromname toname exepath outpath\n");
  }
  return 0;
}