source: zzuf/trunk/src/myfork.c @ 4393 Tweet

/*
 *  zzuf - general purpose fuzzer
 *  Copyright (c) 2002-2010 Sam Hocevar <sam@hocevar.net>
 *                All Rights Reserved
 *
 *  This program is free software. It comes without any warranty, to
 *  the extent permitted by applicable law. You can redistribute it
 *  and/or modify it under the terms of the Do What The Fuck You Want
 *  To Public License, Version 2, as published by Sam Hocevar. See
 *  http://sam.zoy.org/wtfpl/COPYING for more details.
 */

/*
 *  myfork.c: launcher
 */

#include "config.h"

#define _INCLUDE_POSIX_SOURCE /* for STDERR_FILENO on HP-UX */

#if defined HAVE_STDINT_H
#   include <stdint.h>
#elif defined HAVE_INTTYPES_H
#   include <inttypes.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#if defined HAVE_UNISTD_H
#   include <unistd.h>
#endif
#if defined HAVE_WINDOWS_H
#   include <windows.h>
#   include <imagehlp.h>
#   include <tlhelp32.h>
#endif
#include <string.h>
#include <fcntl.h> /* for O_BINARY */
#if defined HAVE_SYS_RESOURCE_H
#   include <sys/resource.h> /* for RLIMIT_AS */
#endif

#include "common.h"
#include "opts.h"
#include "random.h"
#include "fd.h"
#include "fuzz.h"
#include "myfork.h"
#include "md5.h"
#include "timer.h"

/* Handle old libtool versions */
#if !defined LT_OBJDIR
#   define LT_OBJDIR ".libs/"
#endif

#if defined RLIMIT_AS
#   define ZZUF_RLIMIT_MEM RLIMIT_AS
#elif defined RLIMIT_VMEM
#   define ZZUF_RLIMIT_MEM RLIMIT_VMEM
#elif defined RLIMIT_DATA
#   define ZZUF_RLIMIT_MEM RLIMIT_DATA
#else
#   undef ZZUF_RLIMIT_MEM
#endif

#if defined RLIMIT_CPU
#   define ZZUF_RLIMIT_CPU RLIMIT_CPU
#else
#   undef ZZUF_RLIMIT_CPU
#endif

static int run_process(struct child *child, struct opts *, int[][2]);

#if defined HAVE_WINDOWS_H
static void rep32(uint8_t *buf, void *addr);
static int dll_inject(void *, void *, char const *);
static intptr_t get_base_address(DWORD);
static intptr_t get_entry_point_offset(char const *);
#endif

int myfork(struct child *child, struct opts *opts)
{
    int pipes[3][2];
    pid_t pid;
    int i;

    /* Prepare communication pipe */
    for(i = 0; i < 3; i++)
    {
        int ret;
#if defined HAVE_PIPE
        ret = pipe(pipes[i]);
#elif defined HAVE__PIPE
        ret = _pipe(pipes[i], 512, _O_BINARY | O_NOINHERIT);
#endif
        if(ret < 0)
        {
            perror("pipe");
            return -1;
        }
    }

    pid = run_process(child, opts, pipes);
    if(pid < 0)
    {
        /* FIXME: close pipes */
        fprintf(stderr, "error launching `%s'\n", child->newargv[0]);
        return -1;
    }

    child->pid = pid;
    for(i = 0; i < 3; i++)
    {
        close(pipes[i][1]);
        child->fd[i] = pipes[i][0];
    }

    return 0;
}

#if !defined HAVE_SETENV
static void setenv(char const *name, char const *value, int overwrite)
{
    char *str;

    if(!overwrite && getenv(name))
        return;

    str = malloc(strlen(name) + 1 + strlen(value) + 1);
    sprintf(str, "%s=%s", name, value);
    putenv(str);
}
#endif

static int run_process(struct child *child, struct opts *opts, int pipes[][2])
{
    char buf[64];
#if defined HAVE_FORK
    static int const files[] = { DEBUG_FILENO, STDERR_FILENO, STDOUT_FILENO };
    char *libpath, *tmp;
    int pid, j, len = strlen(opts->oldargv[0]);
#   if defined __APPLE__
#       define EXTRAINFO ""
#       define PRELOAD "DYLD_INSERT_LIBRARIES"
    setenv("DYLD_FORCE_FLAT_NAMESPACE", "1", 1);
#   elif defined __osf__
#       define EXTRAINFO ":DEFAULT"
#       define PRELOAD "_RLD_LIST"
#   elif defined __sun && defined __i386
#       define EXTRAINFO ""
#       define PRELOAD "LD_PRELOAD_32"
#   else
#       define EXTRAINFO ""
#       define PRELOAD "LD_PRELOAD"
#   endif
#elif HAVE_WINDOWS_H
    PROCESS_INFORMATION pinfo;
    STARTUPINFO sinfo;
    HANDLE pid;
    void *epaddr;
    int ret;
#endif

#if defined HAVE_FORK
    /* Fork and launch child */
    pid = fork();
    if(pid < 0)
        perror("fork");
    if(pid != 0)
        return pid;

    /* We loop in reverse order so that files[0] is done last,
     * just in case one of the other dup2()ed fds had the value */
    for(j = 3; j--; )
    {
        close(pipes[j][0]);
        if(pipes[j][1] != files[j])
        {
            dup2(pipes[j][1], files[j]);
            close(pipes[j][1]);
        }
    }
#endif

#if defined HAVE_SETRLIMIT && defined ZZUF_RLIMIT_MEM
    if(opts->maxmem >= 0)
    {
        struct rlimit rlim;
        rlim.rlim_cur = opts->maxmem * 1048576;
        rlim.rlim_max = opts->maxmem * 1048576;
        setrlimit(ZZUF_RLIMIT_MEM, &rlim);
    }
#endif

#if defined HAVE_SETRLIMIT && defined ZZUF_RLIMIT_CPU
    if(opts->maxcpu >= 0)
    {
        struct rlimit rlim;
        rlim.rlim_cur = opts->maxcpu;
        rlim.rlim_max = opts->maxcpu + 5;
        setrlimit(ZZUF_RLIMIT_CPU, &rlim);
    }
#endif

    /* Set environment variables */
    sprintf(buf, "%i", opts->seed);
    setenv("ZZUF_SEED", buf, 1);
    sprintf(buf, "%g", opts->minratio);
    setenv("ZZUF_MINRATIO", buf, 1);
    sprintf(buf, "%g", opts->maxratio);
    setenv("ZZUF_MAXRATIO", buf, 1);

#if defined HAVE_FORK
    /* Make sure there is space for everything we might do. */
    libpath = malloc(len + strlen(LIBDIR "/" LT_OBJDIR SONAME EXTRAINFO) + 1);
    strcpy(libpath, opts->oldargv[0]);

    /* If the binary name contains a '/', we look for a libzzuf in the
     * same directory. Otherwise, we only look into the system directory
     * to avoid shared library attacks. Write the result in libpath. */
    tmp = strrchr(libpath, '/');
    if(tmp)
    {
        strcpy(tmp + 1, LT_OBJDIR SONAME);
        if(access(libpath, R_OK) < 0)
            strcpy(libpath, LIBDIR "/" SONAME);
    }
    else
        strcpy(libpath, LIBDIR "/" SONAME);

    /* OSF1 only */
    strcat(libpath, EXTRAINFO);

    /* Do not clobber previous LD_PRELOAD values */
    tmp = getenv(PRELOAD);
    if(tmp && *tmp)
    {
        char *bigbuf = malloc(strlen(tmp) + strlen(libpath) + 2);
        sprintf(bigbuf, "%s:%s", tmp, libpath);
        free(libpath);
        libpath = bigbuf;
    }

    /* Only preload the library in preload mode */
    if (opts->opmode == OPMODE_PRELOAD)
        setenv(PRELOAD, libpath, 1);
    free(libpath);

    if(execvp(child->newargv[0], child->newargv))
    {
        perror(child->newargv[0]);
        exit(EXIT_FAILURE);
    }

    exit(EXIT_SUCCESS);
    /* no return */
    return 0;
#elif HAVE_WINDOWS_H
    pid = GetCurrentProcess();

    memset(&sinfo, 0, sizeof(sinfo));
    sinfo.cb = sizeof(sinfo);
    DuplicateHandle(pid, (HANDLE)_get_osfhandle(pipes[0][1]), pid,
        /* FIXME */ &sinfo.hStdInput, 0, TRUE, DUPLICATE_SAME_ACCESS);
    DuplicateHandle(pid, (HANDLE)_get_osfhandle(pipes[1][1]), pid,
                    &sinfo.hStdError, 0, TRUE, DUPLICATE_SAME_ACCESS);
    DuplicateHandle(pid, (HANDLE)_get_osfhandle(pipes[2][1]), pid,
                    &sinfo.hStdOutput, 0, TRUE, DUPLICATE_SAME_ACCESS);
    sinfo.dwFlags = STARTF_USESTDHANDLES;
    ret = CreateProcess(NULL, child->newargv[0], NULL, NULL, FALSE,
                        CREATE_SUSPENDED, NULL, NULL, &sinfo, &pinfo);
    if(!ret)
        return -1;

    /* Get the child process's entry point address */
    epaddr = (void *)get_entry_point(child->newargv[0],
                                     pinfo.dwProcessId);
    if(!epaddr)
        return -1;

    /* Insert the replacement code */
    ret = dll_inject(pinfo.hProcess, epaddr, SONAME);
    if(ret < 0)
    {
        TerminateProcess(pinfo.hProcess, -1);
        return -1;
    }

    ret = ResumeThread(pinfo.hThread);
    if(ret < 0)
    {
        TerminateProcess(pinfo.hProcess, -1);
        return -1;
    }

    return (long int)pinfo.hProcess;
#endif
}

#if defined HAVE_WINDOWS_H
static void rep32(uint8_t *buf, void *addr)
{
    while(buf++)
        if (memcmp(buf, "____", 4) == 0)
        {
            memcpy(buf, &addr, 4);
            return;
        }
}

static int dll_inject(void *process, void *epaddr, char const *lib)
{
    static uint8_t const loader[] =
        /* Load the injected DLL into memory */
        "\xb8____"       /* mov %eax, <library_name_address> */
        "\x50"           /* push %eax */
        "\xb8____"       /* mov %eax, <LoadLibraryA> */
        "\xff\xd0"       /* call %eax */
        /* Restore the clobbered entry point code using our backup */
        "\xb8\0\0\0\0"   /* mov %eax,0 */
        "\x50"           /* push %eax */
        "\xb8____"       /* mov %eax, <jumper_length> */
        "\x50"           /* push %eax */
        "\xb8____"       /* mov %eax, <backuped_entry_point_address> */
        "\x50"           /* push %eax */
        "\xb8____"       /* mov %eax, <original_entry_point_address> */
        "\x50"           /* push %eax */
        "\xb8____"       /* mov %eax, <GetCurrentProcess> */
        "\xff\xd0"       /* call %eax */
        "\x50"           /* push %eax */
        "\xb8____"       /* mov %eax, <WriteProcessMemory> */
        "\xff\xd0"       /* call %eax */
        /* Jump to the original entry point */
        "\xb8____"       /* mov %eax, <original_entry_point_address> */
        "\xff\xe0";      /* jmp %eax */

    static uint8_t const jumper[] =
        /* Jump to the injected loader */
        "\xb8____"       /* mov eax, <loader_address> */
        "\xff\xe0";      /* jmp eax */

    /* code:
     * +---------------+--------------------+--------------+-------------+
     * |     loader    | entry point backup | library name |   jumper    |
     * |  len(loader)  |    len(jumper)     |   len(lib)   | len(jumper) |
     * +---------------+--------------------+--------------+-------------+ */
    uint8_t code[1024];

    void *kernel32;
    uint8_t *loaderaddr;
    size_t liblen, loaderlen, jumperlen;
    DWORD tmp;

    liblen = strlen(lib) + 1;
    loaderlen = sizeof(loader) - 1;
    jumperlen = sizeof(jumper) - 1;
    if (loaderlen + jumperlen + liblen > 1024)
        return -1;

    /* Allocate memory in the child for our injected code */
    loaderaddr = VirtualAllocEx(process, NULL, loaderlen + jumperlen + liblen,
                                MEM_COMMIT, PAGE_EXECUTE_READWRITE);
    if(!loaderaddr)
        return -1;

    /* Create the first shellcode (jumper).
     *
     * The jumper's job is simply to jump at the second shellcode's location.
     * It is written at the original entry point's location, which will in
     * turn be restored by the second shellcode.
     */
    memcpy(code + loaderlen + jumperlen + liblen, jumper, jumperlen);
    rep32(code + loaderlen + jumperlen + liblen, loaderaddr);

    /* Create the second shellcode (loader, backuped entry point, and library
     * name).
     *
     * The loader's job is to load the library by calling LoadLibraryA(),
     * restore the original entry point using the backup copy, and jump
     * back to the original entry point as if the process had just started.
     *
     * The second shellcode is written at a freshly allocated memory location.
     */
    memcpy(code, loader, loaderlen);
    memcpy(code + loaderlen + jumperlen, lib, liblen);

    /* Backup the old entry point code */
    ReadProcessMemory(process, epaddr, code + loaderlen,
                      jumperlen, &tmp);
    if(tmp != jumperlen)
        return -1;

    /* FIXME: the GetProcAddress calls assume the library was loaded at
     * the same address in the child process. This is wrong since Vista
     * and its address space randomisation. */
    kernel32 = LoadLibrary("kernel32.dll");
    if(!kernel32)
        return -1;

    rep32(code, loaderaddr + loaderlen + jumperlen);
    rep32(code, GetProcAddress(kernel32, "LoadLibraryA"));
    rep32(code, (void *)(uintptr_t)jumperlen);
    rep32(code, loaderaddr + loaderlen);
    rep32(code, epaddr);
    rep32(code, GetProcAddress(kernel32, "GetCurrentProcess"));
    rep32(code, GetProcAddress(kernel32, "WriteProcessMemory"));
    rep32(code, epaddr);
    FreeLibrary(kernel32);

    /* Write our shellcodes into the target process */
    WriteProcessMemory(process, epaddr, code + loaderlen + jumperlen + liblen,
                       jumperlen, &tmp);
    if(tmp != jumperlen)
        return -1;

    WriteProcessMemory(process, loaderaddr, code,
                       loaderlen + jumperlen + liblen, &tmp);
    if(tmp != loaderlen + jumperlen + liblen)
        return -1;

    return 0;
}

/* Find the process's entry point address offset. The information is in
 * the file's PE header. */
static intptr_t get_entry_point(char const *name, DWORD pid)
{
    PIMAGE_DOS_HEADER dos;
    PIMAGE_NT_HEADERS nt;
    intptr_t ret = 0;
    void *file, *map, *base;

    file = CreateFile(name, GENERIC_READ, FILE_SHARE_READ,
                      NULL, OPEN_EXISTING, 0, NULL);
    if(file == INVALID_HANDLE_VALUE)
        return ret;

    map = CreateFileMapping(file, NULL, PAGE_READONLY, 0, 0, NULL);
    if(!map)
    {
        CloseHandle(file);
        return ret;
    }

    base = MapViewOfFile(map, FILE_MAP_READ, 0, 0, 0);
    if(!base)
    {
        CloseHandle(map);
        CloseHandle(file);
        return ret;
    }

    /* Sanity checks */
    dos = (PIMAGE_DOS_HEADER)base;
    nt = (PIMAGE_NT_HEADERS)((char *)base + dos->e_lfanew);
    if(dos->e_magic == IMAGE_DOS_SIGNATURE /* 0x5A4D */
      && nt->Signature == IMAGE_NT_SIGNATURE /* 0x00004550 */
      && nt->FileHeader.Machine == IMAGE_FILE_MACHINE_I386
      && nt->OptionalHeader.Magic == 0x10b /* IMAGE_NT_OPTIONAL_HDR32_MAGIC */)
    {
        ret = get_base_address(pid);
        /* Base address not found in the running process. Falling back
         * to the header's information, which is unreliable because of
         * Vista's address space randomisation. */
        if (!ret)
            ret = (intptr_t)nt->OptionalHeader.BaseOfCode;

        ret += (intptr_t)nt->OptionalHeader.AddressOfEntryPoint;
    }

    UnmapViewOfFile(base);
    CloseHandle(map);
    CloseHandle(file);

    return ret;
}

/* Find the process's base address once it is loaded in memory (the header
 * information is unreliable because of Vista's ASLR). */
static intptr_t get_base_address(DWORD pid)
{
    MODULEENTRY32 entry;
    intptr_t ret = 0;
    void *list;
    int k;

    list = CreateToolhelp32Snapshot(TH32CS_SNAPMODULE, pid);
    entry.dwSize = sizeof(entry);
    for(k = Module32First(list, &entry); k; k = Module32Next(list, &entry))
    {
        /* FIXME: how do we select the correct module? */
        ret = (intptr_t)entry.modBaseAddr;
    }
    CloseHandle(list);

    return ret;
}

#endif