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Back up to the beginning of the file if we don't have a gzip header. 

If the first byte of the file is 31, and we advance to the next byte but
find it's not 139, back up to the first byte before falling through and
treating the file as uncompressed.

Add/expand some comments while we're at it.

Bug: 16252
Change-Id: I292b51f9cc04173482a43b26b0ce73c9e7aee570
Reviewed-on: https://code.wireshark.org/review/35315
Petri-Dish: Guy Harris <guy@alum.mit.edu>
Tested-by: Petri Dish Buildbot
Reviewed-by: Guy Harris <guy@alum.mit.edu>
This commit is contained in:
Guy Harris 2019-12-04 22:19:20 -08:00
parent 4b673a14d0
commit ffabb74e2c
1 changed files with 128 additions and 77 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

205
wiretap/file_wrappers.c
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@ -659,98 +659,149 @@ gz_head(FILE_T state)
if (state->in.next[0] == 31) {
state->in.avail--;
state->in.next++;
if (state->in.avail == 0 && fill_in_buffer(state) == -1)
/* Make sure the byte after the first byte is present */
if (state->in.avail == 0 && fill_in_buffer(state) == -1) {
/* Read error. */
return -1;
if (state->in.avail != 0 && state->in.next[0] == 139) {
}
if (state->in.avail != 0) {
if (state->in.next[0] == 139) {
/*
* We have what looks like the ID1 and ID2 bytes of a gzip
* header.
* Continue processing the file.
*
* XXX - some capture file formats (I'M LOOKING AT YOU,
* ENDACE!) can have 31 in the first byte of the file
* and 139 in the second byte of the file. For now, in
* those cases, you lose.
*/
#ifdef HAVE_ZLIB
guint8 cm;
guint8 flags;
guint16 len;
guint16 hcrc;
guint8 cm;
guint8 flags;
guint16 len;
guint16 hcrc;
/* we have a gzip header, woo hoo! */
state->in.avail--;
state->in.next++;
state->in.avail--;
state->in.next++;
/* read rest of header */
/* read rest of header */
/* compression method (CM) */
if (gz_next1(state, &cm) == -1)
return -1;
if (cm != 8) {
state->err = WTAP_ERR_DECOMPRESS;
state->err_info = "unknown compression method";
return -1;
}
/* flags (FLG) */
if (gz_next1(state, &flags) == -1)
return -1;
if (flags & 0xe0) { /* reserved flag bits */
state->err = WTAP_ERR_DECOMPRESS;
state->err_info = "reserved flag bits set";
return -1;
}
/* modification time (MTIME) */
if (gz_skipn(state, 4) == -1)
return -1;
/* extra flags (XFL) */
if (gz_skipn(state, 1) == -1)
return -1;
/* operating system (OS) */
if (gz_skipn(state, 1) == -1)
return -1;
if (flags & 4) {
/* extra field - get XLEN */
if (gz_next2(state, &len) == -1)
/* compression method (CM) */
if (gz_next1(state, &cm) == -1)
return -1;
if (cm != 8) {
state->err = WTAP_ERR_DECOMPRESS;
state->err_info = "unknown compression method";
return -1;
}
/* skip the extra field */
if (gz_skipn(state, len) == -1)
/* flags (FLG) */
if (gz_next1(state, &flags) == -1) {
/* Read error. */
return -1;
}
if (flags & 8) {
/* file name */
if (gz_skipzstr(state) == -1)
}
if (flags & 0xe0) { /* reserved flag bits */
state->err = WTAP_ERR_DECOMPRESS;
state->err_info = "reserved flag bits set";
return -1;
}
if (flags & 16) {
/* comment */
if (gz_skipzstr(state) == -1)
return -1;
}
if (flags & 2) {
/* header crc */
if (gz_next2(state, &hcrc) == -1)
return -1;
/* XXX - check the CRC? */
}
}
/* set up for decompression */
inflateReset(&(state->strm));
state->strm.adler = crc32(0L, Z_NULL, 0);
state->compression = ZLIB;
state->is_compressed = TRUE;
/* modification time (MTIME) */
if (gz_skipn(state, 4) == -1) {
/* Read error. */
return -1;
}
/* extra flags (XFL) */
if (gz_skipn(state, 1) == -1) {
/* Read error. */
return -1;
}
/* operating system (OS) */
if (gz_skipn(state, 1) == -1) {
/* Read error. */
return -1;
}
if (flags & 4) {
/* extra field - get XLEN */
if (gz_next2(state, &len) == -1) {
/* Read error. */
return -1;
}
/* skip the extra field */
if (gz_skipn(state, len) == -1) {
/* Read error. */
return -1;
}
}
if (flags & 8) {
/* file name */
if (gz_skipzstr(state) == -1) {
/* Read error. */
return -1;
}
}
if (flags & 16) {
/* comment */
if (gz_skipzstr(state) == -1) {
/* Read error. */
return -1;
}
}
if (flags & 2) {
/* header crc */
if (gz_next2(state, &hcrc) == -1) {
/* Read error. */
return -1;
}
/* XXX - check the CRC? */
}
/* set up for decompression */
inflateReset(&(state->strm));
state->strm.adler = crc32(0L, Z_NULL, 0);
state->compression = ZLIB;
state->is_compressed = TRUE;
#ifdef Z_BLOCK
if (state->fast_seek) {
struct zlib_cur_seek_point *cur = g_new(struct zlib_cur_seek_point,1);
if (state->fast_seek) {
struct zlib_cur_seek_point *cur = g_new(struct zlib_cur_seek_point,1);
cur->pos = cur->have = 0;
g_free(state->fast_seek_cur);
state->fast_seek_cur = cur;
fast_seek_header(state, state->raw_pos - state->in.avail, state->pos, GZIP_AFTER_HEADER);
}
cur->pos = cur->have = 0;
g_free(state->fast_seek_cur);
state->fast_seek_cur = cur;
fast_seek_header(state, state->raw_pos - state->in.avail, state->pos, GZIP_AFTER_HEADER);
}
#endif /* Z_BLOCK */
return 0;
return 0;
#else /* HAVE_ZLIB */
state->err = WTAP_ERR_DECOMPRESSION_NOT_SUPPORTED;
state->err_info = "reading gzip-compressed files isn't supported";
return -1;
state->err = WTAP_ERR_DECOMPRESSION_NOT_SUPPORTED;
state->err_info = "reading gzip-compressed files isn't supported";
return -1;
#endif /* HAVE_ZLIB */
}
/*
* Not a gzip file. "Unget" the first character; either:
*
* 1) we read both of the first two bytes into the
* buffer with the first ws_read, so we can just back
* up by one byte;
*
* 2) we only read the first byte into the buffer with
* the first ws_read (e.g., because we're reading from
* a pipe and only the first byte had been writen to
* the pipe at that point), and read the second byte
* into the buffer after the first byte in the
* fill_in_buffer call, so we now have two bytes in
* the buffer, and can just back up by one byte.
*/
state->in.avail++;
state->in.next--;
}
}
#ifdef HAVE_LIBXZ