view toys/posix/cpio.c @ 1331:11fe363078b8 draft

cpio: archive more files While writing tests for cpio, I found that cpio tries to open empty files if they're regular files, and fails to archive them if unreadable. This can be easily avoided, and is not the usual behavior.
author Isaac Dunham <ibid.ag@gmail.com>
date Sun, 01 Jun 2014 13:50:39 -0500
parents c214de62b18b
children 2148d1502264
line wrap: on
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/* cpio.c - a basic cpio
 *
 * Written 2013 AD by Isaac Dunham; this code is placed under the 
 * same license as toybox or as CC0, at your option.
 *
 * 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, the newer standards removed it around the time RPM
 * and initramfs started heavily using this archive format.
 *
 * Modern cpio expanded header 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

USE_CPIO(NEWTOY(cpio, "duH:i|t|F:v(verbose)o|[!io][!ot]", TOYFLAG_BIN))

config CPIO
  bool "cpio"
  default y
  help
    usage: cpio -{o|t|i} [-v] [--verbose] [-F FILE] [ignored: -du -H newc]

    copy files into and out of a "newc" format cpio archive

    -F FILE	use archive FILE instead of stdin/stdout
    -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 (list files during create/extract)
*/

#define FOR_cpio
#include "toys.h"

GLOBALS(
  char *archive;
  char *fmt;
)

// 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
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)
{
  int afd;

  // Subtle bit: FLAG_o is 1 so we can just use it to select stdin/stdout.

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

    afd = xcreate(TT.archive, 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.
    xreadall(afd, toybuf, 110);
    tofree = name = strpad(afd, x8u(toybuf+94), 110);
    if (!strcmp("TRAILER!!!", name)) 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+30);
    gid = x8u(toybuf+38);
    timestamp = x8u(toybuf+46); // unsigned 32 bit, so year 2100 problem

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

    if (!test && strrchr(name, '/') && mkpathat(AT_FDCWD, name, 0, 2)) {
      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);
      // Can't get a filehandle to a symlink, so do special chown
      if (!err && !getpid()) 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 (!getpid()) {
          err = fchown(fd, uid, gid);
          if (!err) err = fchmod(fd, mode);
        }
        close(fd);
      }
    } else if (!test)
      err = mknod(name, mode, makedev(x8u(toybuf+62), x8u(toybuf+70)));

    // 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) && !getpid()) {
        int fd = open(name, O_WRONLY|O_NOFOLLOW);
        struct stat st;

        if (fd != -1 && !fstat(fd, &st) && (st.st_mode&S_IFMT) == mode)
          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("'%s'", 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("%s", 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, major(st.st_dev),
          minor(st.st_dev), major(st.st_rdev), 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) write(afd, &zero, 4-llen);
      }
      close(fd);
    }
    free(name);

    memset(toybuf, 0, sizeof(toybuf));
    xwrite(afd, toybuf,
      sprintf(toybuf, "070701%040X%056X%08XTRAILER!!!", 1, 0x0b, 0)+4);
  }
}