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compress.c

/*
 * Copyright (c) Ian F. Darwin 1986-1995.
 * Software written by Ian F. Darwin and others;
 * maintained 1995-present by Christos Zoulas and others.
 * 
 * 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 immediately at the beginning of the file, without modification,
 *    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.
 *  
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */
/*
 * compress routines:
 *    zmagic() - returns 0 if not recognized, uncompresses and prints
 *             information if recognized
 *    uncompress(method, old, n, newch) - uncompress old into new, 
 *                                using method, return sizeof new
 */
#include "file.h"
#include "magic.h"
#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#ifdef HAVE_SYS_WAIT_H
#include <sys/wait.h>
#endif
#ifdef HAVE_LIBZ
#include <zlib.h>
#endif

#ifndef lint
FILE_RCSID("@(#)$Id: compress.c,v 1.38 2004/09/11 19:15:57 christos Exp $")
#endif


private struct {
      const char *magic;
      size_t maglen;
      const char *const argv[3];
      int silent;
} compr[] = {
      { "\037\235", 2, { "gzip", "-cdq", NULL }, 1 },       /* compressed */
      /* Uncompress can get stuck; so use gzip first if we have it
       * Idea from Damien Clark, thanks! */
      { "\037\235", 2, { "uncompress", "-c", NULL }, 1 },   /* compressed */
      { "\037\213", 2, { "gzip", "-cdq", NULL }, 1 },       /* gzipped */
      { "\037\236", 2, { "gzip", "-cdq", NULL }, 1 },       /* frozen */
      { "\037\240", 2, { "gzip", "-cdq", NULL }, 1 },       /* SCO LZH */
      /* the standard pack utilities do not accept standard input */
      { "\037\036", 2, { "gzip", "-cdq", NULL }, 0 },       /* packed */
      { "BZh",      3, { "bzip2", "-cd", NULL }, 1 },       /* bzip2-ed */
};

private int ncompr = sizeof(compr) / sizeof(compr[0]);


private ssize_t swrite(int, const void *, size_t);
private ssize_t sread(int, void *, size_t);
private size_t uncompressbuf(struct magic_set *, size_t, const unsigned char *,
    unsigned char **, size_t);
#ifdef HAVE_LIBZ
private size_t uncompressgzipped(struct magic_set *, const unsigned char *,
    unsigned char **, size_t);
#endif

protected int
file_zmagic(struct magic_set *ms, const unsigned char *buf, size_t nbytes)
{
      unsigned char *newbuf = NULL;
      size_t i, nsz;
      int rv = 0;

      if ((ms->flags & MAGIC_COMPRESS) == 0)
            return 0;

      for (i = 0; i < ncompr; i++) {
            if (nbytes < compr[i].maglen)
                  continue;
            if (memcmp(buf, compr[i].magic, compr[i].maglen) == 0 &&
                (nsz = uncompressbuf(ms, i, buf, &newbuf, nbytes)) != 0) {
                  ms->flags &= ~MAGIC_COMPRESS;
                  rv = -1;
                  if (file_buffer(ms, newbuf, nsz) == -1)
                        goto error;
                  if (file_printf(ms, " (") == -1)
                        goto error;
                  if (file_buffer(ms, buf, nbytes) == -1)
                        goto error;
                  if (file_printf(ms, ")") == -1)
                        goto error;
                  rv = 1;
                  break;
            }
      }
error:
      if (newbuf)
            free(newbuf);
      ms->flags |= MAGIC_COMPRESS;
      return rv;
}

/*
 * `safe' write for sockets and pipes.
 */
private ssize_t
swrite(int fd, const void *buf, size_t n)
{
      int rv;
      size_t rn = n;

      do
            switch (rv = write(fd, buf, n)) {
            case -1:
                  if (errno == EINTR)
                        continue;
                  return -1;
            default:
                  n -= rv;
                  buf = ((const char *)buf) + rv;
                  break;
            }
      while (n > 0);
      return rn;
}


/*
 * `safe' read for sockets and pipes.
 */
private ssize_t
sread(int fd, void *buf, size_t n)
{
      int rv;
      size_t rn = n;

      do
            switch (rv = read(fd, buf, n)) {
            case -1:
                  if (errno == EINTR)
                        continue;
                  return -1;
            case 0:
                  return rn - n;
            default:
                  n -= rv;
                  buf = ((char *)buf) + rv;
                  break;
            }
      while (n > 0);
      return rn;
}

protected int
file_pipe2file(struct magic_set *ms, int fd, const void *startbuf,
    size_t nbytes)
{
      char buf[4096];
      int r, tfd;

      (void)strcpy(buf, "/tmp/file.XXXXXX");
#ifndef HAVE_MKSTEMP
      {
            char *ptr = mktemp(buf);
            tfd = open(ptr, O_RDWR|O_TRUNC|O_EXCL|O_CREAT, 0600);
            r = errno;
            (void)unlink(ptr);
            errno = r;
      }
#else
      tfd = mkstemp(buf);
      r = errno;
      (void)unlink(buf);
      errno = r;
#endif
      if (tfd == -1) {
            file_error(ms, errno,
                "cannot create temporary file for pipe copy");
            return -1;
      }

      if (swrite(tfd, startbuf, nbytes) != (ssize_t)nbytes)
            r = 1;
      else {
            while ((r = sread(fd, buf, sizeof(buf))) > 0)
                  if (swrite(tfd, buf, (size_t)r) != r)
                        break;
      }

      switch (r) {
      case -1:
            file_error(ms, errno, "error copying from pipe to temp file");
            return -1;
      case 0:
            break;
      default:
            file_error(ms, errno, "error while writing to temp file");
            return -1;
      }

      /*
       * We duplicate the file descriptor, because fclose on a
       * tmpfile will delete the file, but any open descriptors
       * can still access the phantom inode.
       */
      if ((fd = dup2(tfd, fd)) == -1) {
            file_error(ms, errno, "could not dup descriptor for temp file");
            return -1;
      }
      (void)close(tfd);
      if (lseek(fd, (off_t)0, SEEK_SET) == (off_t)-1) {
            file_badseek(ms);
            return -1;
      }
      return fd;
}

#ifdef HAVE_LIBZ

#define FHCRC           (1 << 1)
#define FEXTRA          (1 << 2)
#define FNAME           (1 << 3)
#define FCOMMENT  (1 << 4)

private size_t
uncompressgzipped(struct magic_set *ms, const unsigned char *old,
    unsigned char **newch, size_t n)
{
      unsigned char flg = old[3];
      size_t data_start = 10;
      z_stream z;
      int rc;

      if (flg & FEXTRA) {
            if (data_start+1 >= n)
                  return 0;
            data_start += 2 + old[data_start] + old[data_start + 1] * 256;
      }
      if (flg & FNAME) {
            while(data_start < n && old[data_start])
                  data_start++;
            data_start++;
      }
      if(flg & FCOMMENT) {
            while(data_start < n && old[data_start])
                  data_start++;
            data_start++;
      }
      if(flg & FHCRC)
            data_start += 2;

      if (data_start >= n)
            return 0;
      if ((*newch = (unsigned char *)malloc(HOWMANY + 1)) == NULL) {
            return 0;
      }
      
      /* XXX: const castaway, via strchr */
      z.next_in = (Bytef *)strchr((const char *)old + data_start,
          old[data_start]);
      z.avail_in = n - data_start;
      z.next_out = *newch;
      z.avail_out = HOWMANY;
      z.zalloc = Z_NULL;
      z.zfree = Z_NULL;
      z.opaque = Z_NULL;

      rc = inflateInit2(&z, -15);
      if (rc != Z_OK) {
            file_error(ms, 0, "zlib: %s", z.msg);
            return 0;
      }

      rc = inflate(&z, Z_SYNC_FLUSH);
      if (rc != Z_OK && rc != Z_STREAM_END) {
            file_error(ms, 0, "zlib: %s", z.msg);
            return 0;
      }

      n = (size_t)z.total_out;
      inflateEnd(&z);
      
      /* let's keep the nul-terminate tradition */
      (*newch)[n++] = '\0';

      return n;
}
#endif

private size_t
uncompressbuf(struct magic_set *ms, size_t method, const unsigned char *old,
    unsigned char **newch, size_t n)
{
      int fdin[2], fdout[2];
      int r;

      /* The buffer is NUL terminated, and we don't need that. */
      n--;
       
#ifdef HAVE_LIBZ
      if (method == 2)
            return uncompressgzipped(ms, old, newch, n);
#endif

      if (pipe(fdin) == -1 || pipe(fdout) == -1) {
            file_error(ms, errno, "cannot create pipe");    
            return 0;
      }
      switch (fork()) {
      case 0:     /* child */
            (void) close(0);
            (void) dup(fdin[0]);
            (void) close(fdin[0]);
            (void) close(fdin[1]);

            (void) close(1);
            (void) dup(fdout[1]);
            (void) close(fdout[0]);
            (void) close(fdout[1]);
            if (compr[method].silent)
                  (void) close(2);

            execvp(compr[method].argv[0],
                   (char *const *)compr[method].argv);
            exit(1);
            /*NOTREACHED*/
      case -1:
            file_error(ms, errno, "could not fork");
            return 0;

      default: /* parent */
            (void) close(fdin[0]);
            (void) close(fdout[1]);
            /* fork again, to avoid blocking because both pipes filled */
            switch (fork()) {
            case 0: /* child */
                  (void)close(fdout[0]);
                  if (swrite(fdin[1], old, n) != n)
                        exit(1);
                  exit(0);
                  /*NOTREACHED*/

            case -1:
                  exit(1);
                  /*NOTREACHED*/

            default:  /* parent */
                  break;
            }
            (void) close(fdin[1]);
            fdin[1] = -1;
            if ((*newch = (unsigned char *) malloc(HOWMANY + 1)) == NULL) {
                  n = 0;
                  goto err;
            }
            if ((r = sread(fdout[0], *newch, HOWMANY)) <= 0) {
                  free(*newch);
                  n = 0;
                  newch[0] = '\0';
                  goto err;
            } else {
                  n = r;
            }
            /* NUL terminate, as every buffer is handled here. */
            (*newch)[n++] = '\0';
err:
            if (fdin[1] != -1)
                  (void) close(fdin[1]);
            (void) close(fdout[0]);
#ifdef WNOHANG
            while (waitpid(-1, NULL, WNOHANG) != -1)
                  continue;
#else
            (void)wait(NULL);
#endif
            return n;
      }
}

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