toys/posix/cpio.c

/* cpio.c - a basic cpio
 *
 * Copyright 2013 Isaac Dunham <ibid.ag@gmail.com>
 * Copyright 2015 Frontier Silicon Ltd.
 *
 * see https://www.kernel.org/doc/Documentation/early-userspace/buffer-format.txt
 * and http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/cpio.html
 * and http://pubs.opengroup.org/onlinepubs/7908799/xcu/cpio.html
 *
 * Yes, that's SUSv2, newer versions removed it, but RPM and initramfs use
 * this archive format. We implement (only) the modern "-H newc" variant which
 * expanded headers to 110 bytes (first field 6 bytes, rest are 8).
 * In order: magic ino mode uid gid nlink mtime filesize devmajor devminor
 * rdevmajor rdevminor namesize check
 * This is the equivalent of mode -H newc in other implementations.
 *
 * todo: export/import linux file list text format ala gen_initramfs_list.sh

USE_CPIO(NEWTOY(cpio, "(no-preserve-owner)(trailer)mduH:p:|i|t|F:v(verbose)o|[!pio][!pot][!pF]", TOYFLAG_BIN))

config CPIO
  bool "cpio"
  default y
  help
    usage: cpio -{o|t|i|p DEST} [-v] [--verbose] [-F FILE] [--no-preserve-owner]
           [ignored: -mdu -H newc]

    Copy files into and out of a "newc" format cpio archive.

    -F FILE	Use archive FILE instead of stdin/stdout
    -p DEST	Copy-pass mode, copy stdin file list to directory DEST
    -i	Extract from archive into file system (stdin=archive)
    -o	Create archive (stdin=list of files, stdout=archive)
    -t	Test files (list only, stdin=archive, stdout=list of files)
    -v	Verbose
    --no-preserve-owner (don't set ownership during extract)
    --trailer Add legacy trailer (prevents concatenation)
*/

#define FOR_cpio
#include "toys.h"

GLOBALS(
  char *F, *p, *H;
)

// Read strings, tail padded to 4 byte alignment. Argument "align" is amount
// by which start of string isn't aligned (usually 0, but header is 110 bytes
// which is 2 bytes off because the first field wasn't expanded from 6 to 8).
static char *strpad(int fd, unsigned len, unsigned align)
{
  char *str;

  align = (align + len) & 3;
  if (align) len += (4-align);
  xreadall(fd, str = xmalloc(len+1), len);
  str[len]=0; // redundant, in case archive is bad

  return str;
}

//convert hex to uint; mostly to allow using bits of non-terminated strings
static unsigned x8u(char *hex)
{
  unsigned val, inpos = 8, outpos;
  char pattern[6];

  while (*hex == '0') {
    hex++;
    if (!--inpos) return 0;
  }
  // Because scanf gratuitously treats %*X differently than printf does.
  sprintf(pattern, "%%%dX%%n", inpos);
  sscanf(hex, pattern, &val, &outpos);
  if (inpos != outpos) error_exit("bad header");

  return val;
}

void cpio_main(void)
{
  // Subtle bit: FLAG_o is 1 so we can just use it to select stdin/stdout.
  int pipe, afd = toys.optflags & FLAG_o;
  pid_t pid = 0;

  // In passthrough mode, parent stays in original dir and generates archive
  // to pipe, child does chdir to new dir and reads archive from stdin (pipe).
  if (TT.p) {
    if (toys.stacktop) {
      // xpopen() doesn't return from child due to vfork(), instead restarts
      // with !toys.stacktop
      pid = xpopen(0, &pipe, 0);
      afd = pipe;
    } else {
      // child
      toys.optflags |= FLAG_i;
      xchdir(TT.p);
    }
  }

  if (TT.F) {
    int perm = (toys.optflags & FLAG_o) ? O_CREAT|O_WRONLY|O_TRUNC : O_RDONLY;

    afd = xcreate(TT.F, perm, 0644);
  }

  // read cpio archive

  if (toys.optflags & (FLAG_i|FLAG_t)) for (;;) {
    char *name, *tofree, *data;
    unsigned size, mode, uid, gid, timestamp;
    int test = toys.optflags & FLAG_t, err = 0;

    // Read header and name.
    if (!(size =readall(afd, toybuf, 110))) break;
    if (size != 110 || memcmp(toybuf, "070701", 6)) error_exit("bad header");
    tofree = name = strpad(afd, x8u(toybuf+94), 110);
    if (!strcmp("TRAILER!!!", name)) {
      if (CFG_TOYBOX_FREE) free(tofree);
      break;
    }

    // If you want to extract absolute paths, "cd /" and run cpio.
    while (*name == '/') name++;
    // TODO: remove .. entries

    size = x8u(toybuf+54);
    mode = x8u(toybuf+14);
    uid = x8u(toybuf+22);
    gid = x8u(toybuf+30);
    timestamp = x8u(toybuf+46); // unsigned 32 bit, so year 2100 problem

    if (toys.optflags & (FLAG_t|FLAG_v)) puts(name);

    if (!test && strrchr(name, '/') && mkpath(name)) {
      perror_msg("mkpath '%s'", name);
      test++;
    }

    // Consume entire record even if it couldn't create file, so we're
    // properly aligned with next file.

    if (S_ISDIR(mode)) {
      if (!test) err = mkdir(name, mode);
    } else if (S_ISLNK(mode)) {
      data = strpad(afd, size, 0);
      if (!test) err = symlink(data, name);
      free(data);
      // Can't get a filehandle to a symlink, so do special chown
      if (!err && !geteuid() && !(toys.optflags & FLAG_no_preserve_owner))
        err = lchown(name, uid, gid);
    } else if (S_ISREG(mode)) {
      int fd = test ? 0 : open(name, O_CREAT|O_WRONLY|O_TRUNC|O_NOFOLLOW, mode);

      // If write fails, we still need to read/discard data to continue with
      // archive. Since doing so overwrites errno, report error now
      if (fd < 0) {
        perror_msg("create %s", name);
        test++;
      }

      data = toybuf;
      while (size) {
        if (size < sizeof(toybuf)) data = strpad(afd, size, 0);
        else xreadall(afd, toybuf, sizeof(toybuf));
        if (!test) xwrite(fd, data, data == toybuf ? sizeof(toybuf) : size);
        if (data != toybuf) {
          free(data);
          break;
        }
        size -= sizeof(toybuf);
      }

      if (!test) {
        // set owner, restore dropped suid bit
        if (!geteuid() && !(toys.optflags & FLAG_no_preserve_owner)) {
          err = fchown(fd, uid, gid);
          if (!err) err = fchmod(fd, mode);
        }
        close(fd);
      }
    } else if (!test)
      err = mknod(name, mode, dev_makedev(x8u(toybuf+78), x8u(toybuf+86)));

    // Set ownership and timestamp.
    if (!test && !err) {
      // Creading dir/dev doesn't give us a filehandle, we have to refer to it
      // by name to chown/utime, but how do we know it's the same item?
      // Check that we at least have the right type of entity open, and do
      // NOT restore dropped suid bit in this case.
      if (!S_ISREG(mode) && !S_ISLNK(mode) && !geteuid()
          && !(toys.optflags & FLAG_no_preserve_owner))
      {
        int fd = open(name, O_RDONLY|O_NOFOLLOW);
        struct stat st;

        if (fd != -1 && !fstat(fd, &st) && (st.st_mode&S_IFMT) == (mode&S_IFMT))
          err = fchown(fd, uid, gid);
        else err = 1;

        close(fd);
      }

      // set timestamp
      if (!err) {
        struct timespec times[2];

        memset(times, 0, sizeof(struct timespec)*2);
        times[0].tv_sec = times[1].tv_sec = timestamp;
        err = utimensat(AT_FDCWD, name, times, AT_SYMLINK_NOFOLLOW);
      }
    }

    if (err) perror_msg_raw(name);
    free(tofree);

  // Output cpio archive

  } else {
    char *name = 0;
    size_t size = 0;

    for (;;) {
      struct stat st;
      unsigned nlen, error = 0, zero = 0;
      int len, fd = -1;
      ssize_t llen;

      len = getline(&name, &size, stdin);
      if (len<1) break;
      if (name[len-1] == '\n') name[--len] = 0;
      nlen = len+1;
      if (lstat(name, &st) || (S_ISREG(st.st_mode)
          && st.st_size && (fd = open(name, O_RDONLY))<0))
      {
        perror_msg_raw(name);
        continue;
      }

      if (!S_ISREG(st.st_mode) && !S_ISLNK(st.st_mode)) st.st_size = 0;
      if (st.st_size >> 32) perror_msg("skipping >2G file '%s'", name);
      else {
        llen = sprintf(toybuf,
          "070701%08X%08X%08X%08X%08X%08X%08X%08X%08X%08X%08X%08X%08X",
          (int)st.st_ino, st.st_mode, st.st_uid, st.st_gid, (int)st.st_nlink,
          (int)st.st_mtime, (int)st.st_size, dev_major(st.st_dev),
          dev_minor(st.st_dev), dev_major(st.st_rdev), dev_minor(st.st_rdev),
          nlen, 0);
        xwrite(afd, toybuf, llen);
        xwrite(afd, name, nlen);

        // NUL Pad header up to 4 multiple bytes.
        llen = (llen + nlen) & 3;
        if (llen) xwrite(afd, &zero, 4-llen);

        // Write out body for symlink or regular file
        llen = st.st_size;
        if (S_ISLNK(st.st_mode)) {
          if (readlink(name, toybuf, sizeof(toybuf)-1) == llen)
            xwrite(afd, toybuf, llen);
          else perror_msg("readlink '%s'", name);
        } else while (llen) {
          nlen = llen > sizeof(toybuf) ? sizeof(toybuf) : llen;
          llen -= nlen;
          // If read fails, write anyway (already wrote size in header)
          if (nlen != readall(fd, toybuf, nlen))
            if (!error++) perror_msg("bad read from file '%s'", name);
          xwrite(afd, toybuf, nlen);
        }
        llen = st.st_size & 3;
        if (llen) xwrite(afd, &zero, 4-llen);
      }
      close(fd);
    }
    free(name);

    if (FLAG_trailer) {
      memset(toybuf, 0, sizeof(toybuf));
      xwrite(afd, toybuf,
        sprintf(toybuf, "070701%040X%056X%08XTRAILER!!!", 1, 0x0b, 0)+4);
    }
  }
  if (TT.F) xclose(afd);

  if (TT.p) toys.exitval |= xpclose(pid, pipe);
}