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wireshark/epan/tvbuff_zlib.c

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/* tvbuff_zlib.c
*
* Copyright (c) 2000 by Gilbert Ramirez <gram@alumni.rice.edu>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include <config.h>
#include <glib.h>
#include <string.h>
#ifdef HAVE_ZLIB
#define ZLIB_CONST
#include <zlib.h>
#endif
#include "tvbuff.h"
#ifdef TVB_Z_DEBUG
#include <wsutil/ws_printf.h> /* ws_debug_printf */
#endif
#ifdef HAVE_ZLIB
/*
* Uncompresses a zlib compressed packet inside a message of tvb at offset with
* length comprlen. Returns an uncompressed tvbuffer if uncompression
* succeeded or NULL if uncompression failed.
*/
#define TVB_Z_MIN_BUFSIZ 32768
#define TVB_Z_MAX_BUFSIZ 1048576 * 10
/* #define TVB_Z_DEBUG 1 */
#undef TVB_Z_DEBUG
tvbuff_t *
tvb_uncompress(tvbuff_t *tvb, const int offset, int comprlen)
{
gint err;
guint bytes_out = 0;
guint8 *compr;
guint8 *uncompr = NULL;
tvbuff_t *uncompr_tvb = NULL;
z_streamp strm;
Bytef *strmbuf;
guint inits_done = 0;
gint wbits = MAX_WBITS;
guint8 *next;
guint bufsiz;
#ifdef TVB_Z_DEBUG
guint inflate_passes = 0;
guint bytes_in = tvb_captured_length_remaining(tvb, offset);
#endif
if (tvb == NULL || comprlen <= 0) {
return NULL;
}
compr = (guint8 *)tvb_memdup(NULL, tvb, offset, comprlen);
if (compr == NULL) {
return NULL;
}
/*
* Assume that the uncompressed data is at least twice as big as
* the compressed size.
*/
bufsiz = tvb_captured_length_remaining(tvb, offset) * 2;
bufsiz = CLAMP(bufsiz, TVB_Z_MIN_BUFSIZ, TVB_Z_MAX_BUFSIZ);
#ifdef TVB_Z_DEBUG
ws_debug_printf("bufsiz: %u bytes\n", bufsiz);
#endif
next = compr;
strm = g_new0(z_stream, 1);
strm->next_in = next;
strm->avail_in = comprlen;
strmbuf = (Bytef *)g_malloc0(bufsiz);
strm->next_out = strmbuf;
strm->avail_out = bufsiz;
err = inflateInit2(strm, wbits);
inits_done = 1;
if (err != Z_OK) {
inflateEnd(strm);
g_free(strm);
wmem_free(NULL, compr);
g_free(strmbuf);
return NULL;
}
while (1) {
memset(strmbuf, '\0', bufsiz);
strm->next_out = strmbuf;
strm->avail_out = bufsiz;
err = inflate(strm, Z_SYNC_FLUSH);
if (err == Z_OK || err == Z_STREAM_END) {
guint bytes_pass = bufsiz - strm->avail_out;
#ifdef TVB_Z_DEBUG
++inflate_passes;
#endif
if (uncompr == NULL) {
/*
* This is ugly workaround for bug #6480
* (https://gitlab.com/wireshark/wireshark/-/issues/6480)
*
* g_memdup(..., 0) returns NULL (g_malloc(0) also)
* when uncompr is NULL logic below doesn't create tvb
* which is later interpreted as decompression failed.
*/
uncompr = (guint8 *)((bytes_pass || err != Z_STREAM_END) ?
g_memdup(strmbuf, bytes_pass) :
g_strdup(""));
} else {
guint8 *new_data = (guint8 *)g_malloc0(bytes_out + bytes_pass);
memcpy(new_data, uncompr, bytes_out);
memcpy(new_data + bytes_out, strmbuf, bytes_pass);
g_free(uncompr);
uncompr = new_data;
}
bytes_out += bytes_pass;
if (err == Z_STREAM_END) {
inflateEnd(strm);
g_free(strm);
g_free(strmbuf);
break;
}
} else if (err == Z_BUF_ERROR) {
/*
* It's possible that not enough frames were captured
* to decompress this fully, so return what we've done
* so far, if any.
*/
inflateEnd(strm);
g_free(strm);
g_free(strmbuf);
if (uncompr != NULL) {
break;
} else {
wmem_free(NULL, compr);
return NULL;
}
} else if (err == Z_DATA_ERROR && inits_done == 1
&& uncompr == NULL && comprlen >= 2 &&
(*compr == 0x1f) && (*(compr + 1) == 0x8b)) {
/*
* inflate() is supposed to handle both gzip and deflate
* streams automatically, but in reality it doesn't
* seem to handle either (at least not within the
* context of an HTTP response.) We have to try
* several tweaks, depending on the type of data and
* version of the library installed.
*/
/*
* Gzip file format. Skip past the header, since the
* fix to make it work (setting windowBits to 31)
* doesn't work with all versions of the library.
*/
Bytef *c = compr + 2;
Bytef flags = 0;
/* we read two bytes already (0x1f, 0x8b) and
need at least Z_DEFLATED, 1 byte flags, 4
bytes MTIME, 1 byte XFL, 1 byte OS */
if (comprlen < 10 || *c != Z_DEFLATED) {
inflateEnd(strm);
g_free(strm);
wmem_free(NULL, compr);
g_free(strmbuf);
return NULL;
}
c++;
flags = *c;
c++;
/* Skip past the MTIME (4 bytes),
XFL, and OS fields (1 byte each). */
c += 6;
if (flags & (1 << 2)) {
/* An Extra field is present. It
consists of 2 bytes xsize and xsize
bytes of data.
Read byte-by-byte (least significant
byte first) to make sure we abort
cleanly when the xsize is truncated
after the first byte. */
guint16 xsize = 0;
if (c-compr < comprlen) {
xsize += *c;
c++;
}
if (c-compr < comprlen) {
xsize += *c << 8;
c++;
}
c += xsize;
}
if (flags & (1 << 3)) {
/* A null terminated filename */
while ((c - compr) < comprlen && *c != '\0') {
c++;
}
c++;
}
if (flags & (1 << 4)) {
/* A null terminated comment */
while ((c - compr) < comprlen && *c != '\0') {
c++;
}
c++;
}
if (c - compr > comprlen) {
inflateEnd(strm);
g_free(strm);
wmem_free(NULL, compr);
g_free(strmbuf);
return NULL;
}
/* Drop gzip header */
comprlen -= (int) (c - compr);
next = c;
inflateReset(strm);
strm->next_in = next;
strm->avail_in = comprlen;
inflateEnd(strm);
inflateInit2(strm, wbits);
inits_done++;
} else if (err == Z_DATA_ERROR && uncompr == NULL &&
inits_done <= 3) {
/*
* Re-init the stream with a negative
* MAX_WBITS. This is necessary due to
* some servers (Apache) not sending
* the deflate header with the
* content-encoded response.
*/
wbits = -MAX_WBITS;
inflateReset(strm);
strm->next_in = next;
strm->avail_in = comprlen;
inflateEnd(strm);
memset(strmbuf, '\0', bufsiz);
strm->next_out = strmbuf;
strm->avail_out = bufsiz;
err = inflateInit2(strm, wbits);
inits_done++;
if (err != Z_OK) {
g_free(strm);
g_free(strmbuf);
wmem_free(NULL, compr);
g_free(uncompr);
return NULL;
}
} else {
inflateEnd(strm);
g_free(strm);
g_free(strmbuf);
if (uncompr == NULL) {
wmem_free(NULL, compr);
return NULL;
}
break;
}
}
#ifdef TVB_Z_DEBUG
ws_debug_printf("inflate() total passes: %u\n", inflate_passes);
ws_debug_printf("bytes in: %u\nbytes out: %u\n\n", bytes_in, bytes_out);
#endif
if (uncompr != NULL) {
uncompr_tvb = tvb_new_real_data(uncompr, bytes_out, bytes_out);
tvb_set_free_cb(uncompr_tvb, g_free);
}
wmem_free(NULL, compr);
return uncompr_tvb;
}
#else
tvbuff_t *
tvb_uncompress(tvbuff_t *tvb _U_, const int offset _U_, int comprlen _U_)
{
return NULL;
}
#endif
tvbuff_t *
tvb_child_uncompress(tvbuff_t *parent, tvbuff_t *tvb, const int offset, int comprlen)
{
tvbuff_t *new_tvb = tvb_uncompress(tvb, offset, comprlen);
if (new_tvb)
tvb_set_child_real_data_tvbuff (parent, new_tvb);
return new_tvb;
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/
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