tor/src/common/torgzip.c
2015-01-06 13:52:54 -05:00

618 lines
18 KiB
C

/* Copyright (c) 2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2015, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file torgzip.c
* \brief A simple in-memory gzip implementation.
**/
#include "orconfig.h"
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include "torint.h"
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#include "util.h"
#include "torlog.h"
#include "torgzip.h"
/* zlib 1.2.4 and 1.2.5 do some "clever" things with macros. Instead of
saying "(defined(FOO) ? FOO : 0)" they like to say "FOO-0", on the theory
that nobody will care if the compile outputs a no-such-identifier warning.
Sorry, but we like -Werror over here, so I guess we need to define these.
I hope that zlib 1.2.6 doesn't break these too.
*/
#ifndef _LARGEFILE64_SOURCE
#define _LARGEFILE64_SOURCE 0
#endif
#ifndef _LFS64_LARGEFILE
#define _LFS64_LARGEFILE 0
#endif
#ifndef _FILE_OFFSET_BITS
#define _FILE_OFFSET_BITS 0
#endif
#ifndef off64_t
#define off64_t int64_t
#endif
#include <zlib.h>
static size_t tor_zlib_state_size_precalc(int inflate,
int windowbits, int memlevel);
/** Total number of bytes allocated for zlib state */
static size_t total_zlib_allocation = 0;
/** Set to 1 if zlib is a version that supports gzip; set to 0 if it doesn't;
* set to -1 if we haven't checked yet. */
static int gzip_is_supported = -1;
/** Return true iff we support gzip-based compression. Otherwise, we need to
* use zlib. */
int
is_gzip_supported(void)
{
if (gzip_is_supported >= 0)
return gzip_is_supported;
if (!strcmpstart(ZLIB_VERSION, "0.") ||
!strcmpstart(ZLIB_VERSION, "1.0") ||
!strcmpstart(ZLIB_VERSION, "1.1"))
gzip_is_supported = 0;
else
gzip_is_supported = 1;
return gzip_is_supported;
}
/** Return a string representation of the version of the currently running
* version of zlib. */
const char *
tor_zlib_get_version_str(void)
{
return zlibVersion();
}
/** Return a string representation of the version of the version of zlib
* used at compilation. */
const char *
tor_zlib_get_header_version_str(void)
{
return ZLIB_VERSION;
}
/** Return the 'bits' value to tell zlib to use <b>method</b>.*/
static INLINE int
method_bits(compress_method_t method, zlib_compression_level_t level)
{
/* Bits+16 means "use gzip" in zlib >= 1.2 */
const int flag = method == GZIP_METHOD ? 16 : 0;
switch (level) {
default:
case HIGH_COMPRESSION: return flag + 15;
case MEDIUM_COMPRESSION: return flag + 13;
case LOW_COMPRESSION: return flag + 11;
}
}
static INLINE int
get_memlevel(zlib_compression_level_t level)
{
switch (level) {
default:
case HIGH_COMPRESSION: return 8;
case MEDIUM_COMPRESSION: return 7;
case LOW_COMPRESSION: return 6;
}
}
/** @{ */
/* These macros define the maximum allowable compression factor. Anything of
* size greater than CHECK_FOR_COMPRESSION_BOMB_AFTER is not allowed to
* have an uncompression factor (uncompressed size:compressed size ratio) of
* any greater than MAX_UNCOMPRESSION_FACTOR.
*
* Picking a value for MAX_UNCOMPRESSION_FACTOR is a trade-off: we want it to
* be small to limit the attack multiplier, but we also want it to be large
* enough so that no legitimate document --even ones we might invent in the
* future -- ever compresses by a factor of greater than
* MAX_UNCOMPRESSION_FACTOR. Within those parameters, there's a reasonably
* large range of possible values. IMO, anything over 8 is probably safe; IMO
* anything under 50 is probably sufficient.
*/
#define MAX_UNCOMPRESSION_FACTOR 25
#define CHECK_FOR_COMPRESSION_BOMB_AFTER (1024*64)
/** @} */
/** Return true if uncompressing an input of size <b>in_size</b> to an input
* of size at least <b>size_out</b> looks like a compression bomb. */
static int
is_compression_bomb(size_t size_in, size_t size_out)
{
if (size_in == 0 || size_out < CHECK_FOR_COMPRESSION_BOMB_AFTER)
return 0;
return (size_out / size_in > MAX_UNCOMPRESSION_FACTOR);
}
/** Given <b>in_len</b> bytes at <b>in</b>, compress them into a newly
* allocated buffer, using the method described in <b>method</b>. Store the
* compressed string in *<b>out</b>, and its length in *<b>out_len</b>.
* Return 0 on success, -1 on failure.
*/
int
tor_gzip_compress(char **out, size_t *out_len,
const char *in, size_t in_len,
compress_method_t method)
{
struct z_stream_s *stream = NULL;
size_t out_size, old_size;
off_t offset;
tor_assert(out);
tor_assert(out_len);
tor_assert(in);
tor_assert(in_len < UINT_MAX);
*out = NULL;
if (method == GZIP_METHOD && !is_gzip_supported()) {
/* Old zlib version don't support gzip in deflateInit2 */
log_warn(LD_BUG, "Gzip not supported with zlib %s", ZLIB_VERSION);
goto err;
}
stream = tor_malloc_zero(sizeof(struct z_stream_s));
stream->zalloc = Z_NULL;
stream->zfree = Z_NULL;
stream->opaque = NULL;
stream->next_in = (unsigned char*) in;
stream->avail_in = (unsigned int)in_len;
if (deflateInit2(stream, Z_BEST_COMPRESSION, Z_DEFLATED,
method_bits(method, HIGH_COMPRESSION),
get_memlevel(HIGH_COMPRESSION),
Z_DEFAULT_STRATEGY) != Z_OK) {
log_warn(LD_GENERAL, "Error from deflateInit2: %s",
stream->msg?stream->msg:"<no message>");
goto err;
}
/* Guess 50% compression. */
out_size = in_len / 2;
if (out_size < 1024) out_size = 1024;
*out = tor_malloc(out_size);
stream->next_out = (unsigned char*)*out;
stream->avail_out = (unsigned int)out_size;
while (1) {
switch (deflate(stream, Z_FINISH))
{
case Z_STREAM_END:
goto done;
case Z_OK:
/* In case zlib doesn't work as I think .... */
if (stream->avail_out >= stream->avail_in+16)
break;
case Z_BUF_ERROR:
offset = stream->next_out - ((unsigned char*)*out);
old_size = out_size;
out_size *= 2;
if (out_size < old_size) {
log_warn(LD_GENERAL, "Size overflow in compression.");
goto err;
}
*out = tor_realloc(*out, out_size);
stream->next_out = (unsigned char*)(*out + offset);
if (out_size - offset > UINT_MAX) {
log_warn(LD_BUG, "Ran over unsigned int limit of zlib while "
"uncompressing.");
goto err;
}
stream->avail_out = (unsigned int)(out_size - offset);
break;
default:
log_warn(LD_GENERAL, "Gzip compression didn't finish: %s",
stream->msg ? stream->msg : "<no message>");
goto err;
}
}
done:
*out_len = stream->total_out;
#ifdef OPENBSD
/* "Hey Rocky! Watch me change an unsigned field to a signed field in a
* third-party API!"
* "Oh, that trick will just make people do unsafe casts to the unsigned
* type in their cross-platform code!"
* "Don't be foolish. I'm _sure_ they'll have the good sense to make sure
* the newly unsigned field isn't negative." */
tor_assert(stream->total_out >= 0);
#endif
if (((size_t)stream->total_out) > out_size + 4097) {
/* If we're wasting more than 4k, don't. */
*out = tor_realloc(*out, stream->total_out + 1);
}
if (deflateEnd(stream)!=Z_OK) {
log_warn(LD_BUG, "Error freeing gzip structures");
goto err;
}
tor_free(stream);
if (is_compression_bomb(*out_len, in_len)) {
log_warn(LD_BUG, "We compressed something and got an insanely high "
"compression factor; other Tors would think this was a zlib bomb.");
goto err;
}
return 0;
err:
if (stream) {
deflateEnd(stream);
tor_free(stream);
}
tor_free(*out);
return -1;
}
/** Given zero or more zlib-compressed or gzip-compressed strings of
* total length
* <b>in_len</b> bytes at <b>in</b>, uncompress them into a newly allocated
* buffer, using the method described in <b>method</b>. Store the uncompressed
* string in *<b>out</b>, and its length in *<b>out_len</b>. Return 0 on
* success, -1 on failure.
*
* If <b>complete_only</b> is true, we consider a truncated input as a
* failure; otherwise we decompress as much as we can. Warn about truncated
* or corrupt inputs at <b>protocol_warn_level</b>.
*/
int
tor_gzip_uncompress(char **out, size_t *out_len,
const char *in, size_t in_len,
compress_method_t method,
int complete_only,
int protocol_warn_level)
{
struct z_stream_s *stream = NULL;
size_t out_size, old_size;
off_t offset;
int r;
tor_assert(out);
tor_assert(out_len);
tor_assert(in);
tor_assert(in_len < UINT_MAX);
if (method == GZIP_METHOD && !is_gzip_supported()) {
/* Old zlib version don't support gzip in inflateInit2 */
log_warn(LD_BUG, "Gzip not supported with zlib %s", ZLIB_VERSION);
return -1;
}
*out = NULL;
stream = tor_malloc_zero(sizeof(struct z_stream_s));
stream->zalloc = Z_NULL;
stream->zfree = Z_NULL;
stream->opaque = NULL;
stream->next_in = (unsigned char*) in;
stream->avail_in = (unsigned int)in_len;
if (inflateInit2(stream,
method_bits(method, HIGH_COMPRESSION)) != Z_OK) {
log_warn(LD_GENERAL, "Error from inflateInit2: %s",
stream->msg?stream->msg:"<no message>");
goto err;
}
out_size = in_len * 2; /* guess 50% compression. */
if (out_size < 1024) out_size = 1024;
if (out_size >= SIZE_T_CEILING || out_size > UINT_MAX)
goto err;
*out = tor_malloc(out_size);
stream->next_out = (unsigned char*)*out;
stream->avail_out = (unsigned int)out_size;
while (1) {
switch (inflate(stream, complete_only ? Z_FINISH : Z_SYNC_FLUSH))
{
case Z_STREAM_END:
if (stream->avail_in == 0)
goto done;
/* There may be more compressed data here. */
if ((r = inflateEnd(stream)) != Z_OK) {
log_warn(LD_BUG, "Error freeing gzip structures");
goto err;
}
if (inflateInit2(stream,
method_bits(method,HIGH_COMPRESSION)) != Z_OK) {
log_warn(LD_GENERAL, "Error from second inflateInit2: %s",
stream->msg?stream->msg:"<no message>");
goto err;
}
break;
case Z_OK:
if (!complete_only && stream->avail_in == 0)
goto done;
/* In case zlib doesn't work as I think.... */
if (stream->avail_out >= stream->avail_in+16)
break;
case Z_BUF_ERROR:
if (stream->avail_out > 0) {
log_fn(protocol_warn_level, LD_PROTOCOL,
"possible truncated or corrupt zlib data");
goto err;
}
offset = stream->next_out - (unsigned char*)*out;
old_size = out_size;
out_size *= 2;
if (out_size < old_size) {
log_warn(LD_GENERAL, "Size overflow in uncompression.");
goto err;
}
if (is_compression_bomb(in_len, out_size)) {
log_warn(LD_GENERAL, "Input looks like a possible zlib bomb; "
"not proceeding.");
goto err;
}
if (out_size >= SIZE_T_CEILING) {
log_warn(LD_BUG, "Hit SIZE_T_CEILING limit while uncompressing.");
goto err;
}
*out = tor_realloc(*out, out_size);
stream->next_out = (unsigned char*)(*out + offset);
if (out_size - offset > UINT_MAX) {
log_warn(LD_BUG, "Ran over unsigned int limit of zlib while "
"uncompressing.");
goto err;
}
stream->avail_out = (unsigned int)(out_size - offset);
break;
default:
log_warn(LD_GENERAL, "Gzip decompression returned an error: %s",
stream->msg ? stream->msg : "<no message>");
goto err;
}
}
done:
*out_len = stream->next_out - (unsigned char*)*out;
r = inflateEnd(stream);
tor_free(stream);
if (r != Z_OK) {
log_warn(LD_BUG, "Error freeing gzip structures");
goto err;
}
/* NUL-terminate output. */
if (out_size == *out_len)
*out = tor_realloc(*out, out_size + 1);
(*out)[*out_len] = '\0';
return 0;
err:
if (stream) {
inflateEnd(stream);
tor_free(stream);
}
if (*out) {
tor_free(*out);
}
return -1;
}
/** Try to tell whether the <b>in_len</b>-byte string in <b>in</b> is likely
* to be compressed or not. If it is, return the likeliest compression method.
* Otherwise, return UNKNOWN_METHOD.
*/
compress_method_t
detect_compression_method(const char *in, size_t in_len)
{
if (in_len > 2 && fast_memeq(in, "\x1f\x8b", 2)) {
return GZIP_METHOD;
} else if (in_len > 2 && (in[0] & 0x0f) == 8 &&
(ntohs(get_uint16(in)) % 31) == 0) {
return ZLIB_METHOD;
} else {
return UNKNOWN_METHOD;
}
}
/** Internal state for an incremental zlib compression/decompression. The
* body of this struct is not exposed. */
struct tor_zlib_state_t {
struct z_stream_s stream; /**< The zlib stream */
int compress; /**< True if we are compressing; false if we are inflating */
/** Number of bytes read so far. Used to detect zlib bombs. */
size_t input_so_far;
/** Number of bytes written so far. Used to detect zlib bombs. */
size_t output_so_far;
/** Approximate number of bytes allocated for this object. */
size_t allocation;
};
/** Construct and return a tor_zlib_state_t object using <b>method</b>. If
* <b>compress</b>, it's for compression; otherwise it's for
* decompression. */
tor_zlib_state_t *
tor_zlib_new(int compress, compress_method_t method,
zlib_compression_level_t compression_level)
{
tor_zlib_state_t *out;
int bits, memlevel;
if (method == GZIP_METHOD && !is_gzip_supported()) {
/* Old zlib version don't support gzip in inflateInit2 */
log_warn(LD_BUG, "Gzip not supported with zlib %s", ZLIB_VERSION);
return NULL;
}
if (! compress) {
/* use this setting for decompression, since we might have the
* max number of window bits */
compression_level = HIGH_COMPRESSION;
}
out = tor_malloc_zero(sizeof(tor_zlib_state_t));
out->stream.zalloc = Z_NULL;
out->stream.zfree = Z_NULL;
out->stream.opaque = NULL;
out->compress = compress;
bits = method_bits(method, compression_level);
memlevel = get_memlevel(compression_level);
if (compress) {
if (deflateInit2(&out->stream, Z_BEST_COMPRESSION, Z_DEFLATED,
bits, memlevel,
Z_DEFAULT_STRATEGY) != Z_OK)
goto err;
} else {
if (inflateInit2(&out->stream, bits) != Z_OK)
goto err;
}
out->allocation = tor_zlib_state_size_precalc(!compress, bits, memlevel);
total_zlib_allocation += out->allocation;
return out;
err:
tor_free(out);
return NULL;
}
/** Compress/decompress some bytes using <b>state</b>. Read up to
* *<b>in_len</b> bytes from *<b>in</b>, and write up to *<b>out_len</b> bytes
* to *<b>out</b>, adjusting the values as we go. If <b>finish</b> is true,
* we've reached the end of the input.
*
* Return TOR_ZLIB_DONE if we've finished the entire compression/decompression.
* Return TOR_ZLIB_OK if we're processed everything from the input.
* Return TOR_ZLIB_BUF_FULL if we're out of space on <b>out</b>.
* Return TOR_ZLIB_ERR if the stream is corrupt.
*/
tor_zlib_output_t
tor_zlib_process(tor_zlib_state_t *state,
char **out, size_t *out_len,
const char **in, size_t *in_len,
int finish)
{
int err;
tor_assert(*in_len <= UINT_MAX);
tor_assert(*out_len <= UINT_MAX);
state->stream.next_in = (unsigned char*) *in;
state->stream.avail_in = (unsigned int)*in_len;
state->stream.next_out = (unsigned char*) *out;
state->stream.avail_out = (unsigned int)*out_len;
if (state->compress) {
err = deflate(&state->stream, finish ? Z_FINISH : Z_NO_FLUSH);
} else {
err = inflate(&state->stream, finish ? Z_FINISH : Z_SYNC_FLUSH);
}
state->input_so_far += state->stream.next_in - ((unsigned char*)*in);
state->output_so_far += state->stream.next_out - ((unsigned char*)*out);
*out = (char*) state->stream.next_out;
*out_len = state->stream.avail_out;
*in = (const char *) state->stream.next_in;
*in_len = state->stream.avail_in;
if (! state->compress &&
is_compression_bomb(state->input_so_far, state->output_so_far)) {
log_warn(LD_DIR, "Possible zlib bomb; abandoning stream.");
return TOR_ZLIB_ERR;
}
switch (err)
{
case Z_STREAM_END:
return TOR_ZLIB_DONE;
case Z_BUF_ERROR:
if (state->stream.avail_in == 0 && !finish)
return TOR_ZLIB_OK;
return TOR_ZLIB_BUF_FULL;
case Z_OK:
if (state->stream.avail_out == 0 || finish)
return TOR_ZLIB_BUF_FULL;
return TOR_ZLIB_OK;
default:
log_warn(LD_GENERAL, "Gzip returned an error: %s",
state->stream.msg ? state->stream.msg : "<no message>");
return TOR_ZLIB_ERR;
}
}
/** Deallocate <b>state</b>. */
void
tor_zlib_free(tor_zlib_state_t *state)
{
if (!state)
return;
total_zlib_allocation -= state->allocation;
if (state->compress)
deflateEnd(&state->stream);
else
inflateEnd(&state->stream);
tor_free(state);
}
/** Return an approximate number of bytes used in RAM to hold a state with
* window bits <b>windowBits</b> and compression level 'memlevel' */
static size_t
tor_zlib_state_size_precalc(int inflate, int windowbits, int memlevel)
{
windowbits &= 15;
#define A_FEW_KILOBYTES 2048
if (inflate) {
/* From zconf.h:
"The memory requirements for inflate are (in bytes) 1 << windowBits
that is, 32K for windowBits=15 (default value) plus a few kilobytes
for small objects."
*/
return sizeof(tor_zlib_state_t) + sizeof(struct z_stream_s) +
(1 << 15) + A_FEW_KILOBYTES;
} else {
/* Also from zconf.h:
"The memory requirements for deflate are (in bytes):
(1 << (windowBits+2)) + (1 << (memLevel+9))
... plus a few kilobytes for small objects."
*/
return sizeof(tor_zlib_state_t) + sizeof(struct z_stream_s) +
(1 << (windowbits + 2)) + (1 << (memlevel + 9)) + A_FEW_KILOBYTES;
}
#undef A_FEW_KILOBYTES
}
/** Return the approximate number of bytes allocated for <b>state</b>. */
size_t
tor_zlib_state_size(const tor_zlib_state_t *state)
{
return state->allocation;
}
/** Return the approximate number of bytes allocated for all zlib states. */
size_t
tor_zlib_get_total_allocation(void)
{
return total_zlib_allocation;
}