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Diffstat (limited to 'src/common/compress.c')
| -rw-r--r-- | src/common/compress.c | 665 |
1 files changed, 665 insertions, 0 deletions
diff --git a/src/common/compress.c b/src/common/compress.c new file mode 100644 index 0000000000..47c93cf6a9 --- /dev/null +++ b/src/common/compress.c @@ -0,0 +1,665 @@ +/* Copyright (c) 2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2017, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file compress.c + * \brief Common compression API. + **/ + +#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 "compress.h" +#include "compress_lzma.h" +#include "compress_none.h" +#include "compress_zlib.h" +#include "compress_zstd.h" + +/** Total number of bytes allocated for compression state overhead. */ +static atomic_counter_t total_compress_allocation; + +/** @{ */ +/* 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. */ +MOCK_IMPL(int, +tor_compress_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); +} + +/** Guess the size that <b>in_len</b> will be after compression or + * decompression. */ +static size_t +guess_compress_size(int compress, compress_method_t method, + compression_level_t compression_level, + size_t in_len) +{ + // ignore these for now. + (void)compression_level; + if (method == NO_METHOD) { + /* Guess that we'll need an extra byte, to avoid a needless realloc + * for nul-termination */ + return (in_len < SIZE_MAX) ? in_len + 1 : in_len; + } + + /* Always guess a factor of 2. */ + if (compress) { + in_len /= 2; + } else { + if (in_len < SIZE_T_CEILING/2) + in_len *= 2; + } + return MAX(in_len, 1024); +} + +/** Internal function to implement tor_compress/tor_uncompress, depending on + * whether <b>compress</b> is set. All arguments are as for tor_compress or + * tor_uncompress. */ +static int +tor_compress_impl(int compress, + char **out, size_t *out_len, + const char *in, size_t in_len, + compress_method_t method, + compression_level_t compression_level, + int complete_only, + int protocol_warn_level) +{ + tor_compress_state_t *stream; + int rv; + + stream = tor_compress_new(compress, method, compression_level); + + if (stream == NULL) { + log_warn(LD_GENERAL, "NULL stream while %scompressing", + compress?"":"de"); + log_debug(LD_GENERAL, "method: %d level: %d at len: %lu", + method, compression_level, (unsigned long)in_len); + return -1; + } + + size_t in_len_orig = in_len; + size_t out_remaining, out_alloc; + char *outptr; + + out_remaining = out_alloc = + guess_compress_size(compress, method, compression_level, in_len); + *out = outptr = tor_malloc(out_remaining); + + const int finish = complete_only || compress; + + while (1) { + switch (tor_compress_process(stream, + &outptr, &out_remaining, + &in, &in_len, finish)) { + case TOR_COMPRESS_DONE: + if (in_len == 0 || compress) { + goto done; + } else { + // More data is present, and we're decompressing. So we may need to + // reinitialize the stream if we are handling multiple concatenated + // inputs. + tor_compress_free(stream); + stream = tor_compress_new(compress, method, compression_level); + if (stream == NULL) { + log_warn(LD_GENERAL, "NULL stream while %scompressing", + compress?"":"de"); + goto err; + } + } + break; + case TOR_COMPRESS_OK: + if (compress || complete_only) { + log_fn(protocol_warn_level, LD_PROTOCOL, + "Unexpected %s while %scompressing", + complete_only?"end of input":"result", + compress?"":"de"); + log_debug(LD_GENERAL, "method: %d level: %d at len: %lu", + method, compression_level, (unsigned long)in_len); + goto err; + } else { + if (in_len == 0) { + goto done; + } + } + break; + case TOR_COMPRESS_BUFFER_FULL: { + if (!compress && outptr < *out+out_alloc) { + // A buffer error in this case means that we have a problem + // with our input. + log_fn(protocol_warn_level, LD_PROTOCOL, + "Possible truncated or corrupt compressed data"); + goto err; + } + if (out_alloc >= SIZE_T_CEILING / 2) { + log_warn(LD_GENERAL, "While %scompressing data: ran out of space.", + compress?"":"un"); + goto err; + } + if (!compress && + tor_compress_is_compression_bomb(in_len_orig, out_alloc)) { + // This should already have been caught down in the backend logic. + // LCOV_EXCL_START + tor_assert_nonfatal_unreached(); + goto err; + // LCOV_EXCL_STOP + } + const size_t offset = outptr - *out; + out_alloc *= 2; + *out = tor_realloc(*out, out_alloc); + outptr = *out + offset; + out_remaining = out_alloc - offset; + break; + } + case TOR_COMPRESS_ERROR: + log_fn(protocol_warn_level, LD_GENERAL, + "Error while %scompressing data: bad input?", + compress?"":"un"); + goto err; // bad data. + + // LCOV_EXCL_START + default: + tor_assert_nonfatal_unreached(); + goto err; + // LCOV_EXCL_STOP + } + } + done: + *out_len = outptr - *out; + if (compress && tor_compress_is_compression_bomb(*out_len, in_len_orig)) { + log_warn(LD_BUG, "We compressed something and got an insanely high " + "compression factor; other Tors would think this was a " + "compression bomb."); + goto err; + } + if (!compress) { + // NUL-terminate our output. + if (out_alloc == *out_len) + *out = tor_realloc(*out, out_alloc + 1); + (*out)[*out_len] = '\0'; + } + rv = 0; + goto out; + + err: + tor_free(*out); + *out_len = 0; + rv = -1; + goto out; + + out: + tor_compress_free(stream); + return rv; +} + +/** 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_compress(char **out, size_t *out_len, + const char *in, size_t in_len, + compress_method_t method) +{ + return tor_compress_impl(1, out, out_len, in, in_len, method, + BEST_COMPRESSION, + 1, LOG_WARN); +} + +/** Given zero or more 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 any bytes are written to <b>out</b>, an extra byte NUL is always + * written at the end, but not counted in <b>out_len</b>. This is a + * safety feature to ensure that the output can be treated as a + * NUL-terminated string -- though of course, callers should check + * out_len anyway. + * + * 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_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) +{ + return tor_compress_impl(0, out, out_len, in, in_len, method, + BEST_COMPRESSION, + complete_only, protocol_warn_level); +} + +/** 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 if (in_len > 2 && + fast_memeq(in, "\x5d\x00\x00", 3)) { + return LZMA_METHOD; + } else if (in_len > 3 && + fast_memeq(in, "\x28\xb5\x2f\xfd", 4)) { + return ZSTD_METHOD; + } else { + return UNKNOWN_METHOD; + } +} + +/** Return 1 if a given <b>method</b> is supported; otherwise 0. */ +int +tor_compress_supports_method(compress_method_t method) +{ + switch (method) { + case GZIP_METHOD: + case ZLIB_METHOD: + return tor_zlib_method_supported(); + case LZMA_METHOD: + return tor_lzma_method_supported(); + case ZSTD_METHOD: + return tor_zstd_method_supported(); + case NO_METHOD: + return 1; + case UNKNOWN_METHOD: + default: + return 0; + } +} + +/** + * Return a bitmask of the supported compression types, where 1<<m is + * set in the bitmask if and only if compression with method <b>m</b> is + * supported. + */ +unsigned +tor_compress_get_supported_method_bitmask(void) +{ + static unsigned supported = 0; + if (supported == 0) { + compress_method_t m; + for (m = NO_METHOD; m <= UNKNOWN_METHOD; ++m) { + if (tor_compress_supports_method(m)) { + supported |= (1u << m); + } + } + } + return supported; +} + +/** Table of compression method names. These should have an "x-" prefix, + * if they are not listed in the IANA content coding registry. */ +static const struct { + const char *name; + compress_method_t method; +} compression_method_names[] = { + { "gzip", GZIP_METHOD }, + { "deflate", ZLIB_METHOD }, + // We call this "x-tor-lzma" rather than "x-lzma", because we impose a + // lower maximum memory usage on the decoding side. + { "x-tor-lzma", LZMA_METHOD }, + { "x-zstd" , ZSTD_METHOD }, + { "identity", NO_METHOD }, + + /* Later entries in this table are not canonical; these are recognized but + * not emitted. */ + { "x-gzip", GZIP_METHOD }, +}; + +/** Return the canonical string representation of the compression method + * <b>method</b>, or NULL if the method isn't recognized. */ +const char * +compression_method_get_name(compress_method_t method) +{ + unsigned i; + for (i = 0; i < ARRAY_LENGTH(compression_method_names); ++i) { + if (method == compression_method_names[i].method) + return compression_method_names[i].name; + } + return NULL; +} + +/** Table of compression human readable method names. */ +static const struct { + compress_method_t method; + const char *name; +} compression_method_human_names[] = { + { NO_METHOD, "uncompressed" }, + { GZIP_METHOD, "gzipped" }, + { ZLIB_METHOD, "deflated" }, + { LZMA_METHOD, "LZMA compressed" }, + { ZSTD_METHOD, "Zstandard compressed" }, + { UNKNOWN_METHOD, "unknown encoding" }, +}; + +/** Return a human readable string representation of the compression method + * <b>method</b>, or NULL if the method isn't recognized. */ +const char * +compression_method_get_human_name(compress_method_t method) +{ + unsigned i; + for (i = 0; i < ARRAY_LENGTH(compression_method_human_names); ++i) { + if (method == compression_method_human_names[i].method) + return compression_method_human_names[i].name; + } + return NULL; +} + +/** Return the compression method represented by the string <b>name</b>, or + * UNKNOWN_METHOD if the string isn't recognized. */ +compress_method_t +compression_method_get_by_name(const char *name) +{ + unsigned i; + for (i = 0; i < ARRAY_LENGTH(compression_method_names); ++i) { + if (!strcmp(compression_method_names[i].name, name)) + return compression_method_names[i].method; + } + return UNKNOWN_METHOD; +} + +/** Return a string representation of the version of the library providing the + * compression method given in <b>method</b>. Returns NULL if <b>method</b> is + * unknown or unsupported. */ +const char * +tor_compress_version_str(compress_method_t method) +{ + switch (method) { + case GZIP_METHOD: + case ZLIB_METHOD: + return tor_zlib_get_version_str(); + case LZMA_METHOD: + return tor_lzma_get_version_str(); + case ZSTD_METHOD: + return tor_zstd_get_version_str(); + case NO_METHOD: + case UNKNOWN_METHOD: + default: + return NULL; + } +} + +/** Return a string representation of the version of the library, found at + * compile time, providing the compression method given in <b>method</b>. + * Returns NULL if <b>method</b> is unknown or unsupported. */ +const char * +tor_compress_header_version_str(compress_method_t method) +{ + switch (method) { + case GZIP_METHOD: + case ZLIB_METHOD: + return tor_zlib_get_header_version_str(); + case LZMA_METHOD: + return tor_lzma_get_header_version_str(); + case ZSTD_METHOD: + return tor_zstd_get_header_version_str(); + case NO_METHOD: + case UNKNOWN_METHOD: + default: + return NULL; + } +} + +/** Return the approximate number of bytes allocated for all + * supported compression schemas. */ +size_t +tor_compress_get_total_allocation(void) +{ + return atomic_counter_get(&total_compress_allocation) + + tor_zlib_get_total_allocation() + + tor_lzma_get_total_allocation() + + tor_zstd_get_total_allocation(); +} + +/** Internal state for an incremental compression/decompression. The body of + * this struct is not exposed. */ +struct tor_compress_state_t { + compress_method_t method; /**< The compression method. */ + + union { + tor_zlib_compress_state_t *zlib_state; + tor_lzma_compress_state_t *lzma_state; + tor_zstd_compress_state_t *zstd_state; + } u; /**< Compression backend state. */ +}; + +/** Construct and return a tor_compress_state_t object using <b>method</b>. If + * <b>compress</b>, it's for compression; otherwise it's for decompression. */ +tor_compress_state_t * +tor_compress_new(int compress, compress_method_t method, + compression_level_t compression_level) +{ + tor_compress_state_t *state; + + state = tor_malloc_zero(sizeof(tor_compress_state_t)); + state->method = method; + + switch (method) { + case GZIP_METHOD: + case ZLIB_METHOD: { + tor_zlib_compress_state_t *zlib_state = + tor_zlib_compress_new(compress, method, compression_level); + + if (zlib_state == NULL) + goto err; + + state->u.zlib_state = zlib_state; + break; + } + case LZMA_METHOD: { + tor_lzma_compress_state_t *lzma_state = + tor_lzma_compress_new(compress, method, compression_level); + + if (lzma_state == NULL) + goto err; + + state->u.lzma_state = lzma_state; + break; + } + case ZSTD_METHOD: { + tor_zstd_compress_state_t *zstd_state = + tor_zstd_compress_new(compress, method, compression_level); + + if (zstd_state == NULL) + goto err; + + state->u.zstd_state = zstd_state; + break; + } + case NO_METHOD: { + break; + } + case UNKNOWN_METHOD: + goto err; + } + + atomic_counter_add(&total_compress_allocation, + sizeof(tor_compress_state_t)); + return state; + + err: + tor_free(state); + 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_COMPRESS_DONE if we've finished the entire + * compression/decompression. + * Return TOR_COMPRESS_OK if we're processed everything from the input. + * Return TOR_COMPRESS_BUFFER_FULL if we're out of space on <b>out</b>. + * Return TOR_COMPRESS_ERROR if the stream is corrupt. + */ +tor_compress_output_t +tor_compress_process(tor_compress_state_t *state, + char **out, size_t *out_len, + const char **in, size_t *in_len, + int finish) +{ + tor_assert(state != NULL); + const size_t in_len_orig = *in_len; + const size_t out_len_orig = *out_len; + tor_compress_output_t rv; + + if (*out_len == 0 && (*in_len > 0 || finish)) { + // If we still have input data, but no space for output data, we might as + // well return early and let the caller do the reallocation of the out + // variable. + return TOR_COMPRESS_BUFFER_FULL; + } + + switch (state->method) { + case GZIP_METHOD: + case ZLIB_METHOD: + rv = tor_zlib_compress_process(state->u.zlib_state, + out, out_len, in, in_len, + finish); + break; + case LZMA_METHOD: + rv = tor_lzma_compress_process(state->u.lzma_state, + out, out_len, in, in_len, + finish); + break; + case ZSTD_METHOD: + rv = tor_zstd_compress_process(state->u.zstd_state, + out, out_len, in, in_len, + finish); + break; + case NO_METHOD: + rv = tor_cnone_compress_process(out, out_len, in, in_len, + finish); + break; + default: + case UNKNOWN_METHOD: + goto err; + } + if (BUG((rv == TOR_COMPRESS_OK) && + *in_len == in_len_orig && + *out_len == out_len_orig)) { + log_warn(LD_GENERAL, + "More info on the bug: method == %s, finish == %d, " + " *in_len == in_len_orig == %lu, " + "*out_len == out_len_orig == %lu", + compression_method_get_human_name(state->method), finish, + (unsigned long)in_len_orig, (unsigned long)out_len_orig); + return TOR_COMPRESS_ERROR; + } + + return rv; + err: + return TOR_COMPRESS_ERROR; +} + +/** Deallocate <b>state</b>. */ +void +tor_compress_free_(tor_compress_state_t *state) +{ + if (state == NULL) + return; + + switch (state->method) { + case GZIP_METHOD: + case ZLIB_METHOD: + tor_zlib_compress_free(state->u.zlib_state); + break; + case LZMA_METHOD: + tor_lzma_compress_free(state->u.lzma_state); + break; + case ZSTD_METHOD: + tor_zstd_compress_free(state->u.zstd_state); + break; + case NO_METHOD: + break; + case UNKNOWN_METHOD: + break; + } + + atomic_counter_sub(&total_compress_allocation, + sizeof(tor_compress_state_t)); + tor_free(state); +} + +/** Return the approximate number of bytes allocated for <b>state</b>. */ +size_t +tor_compress_state_size(const tor_compress_state_t *state) +{ + tor_assert(state != NULL); + + size_t size = sizeof(tor_compress_state_t); + + switch (state->method) { + case GZIP_METHOD: + case ZLIB_METHOD: + size += tor_zlib_compress_state_size(state->u.zlib_state); + break; + case LZMA_METHOD: + size += tor_lzma_compress_state_size(state->u.lzma_state); + break; + case ZSTD_METHOD: + size += tor_zstd_compress_state_size(state->u.zstd_state); + break; + case NO_METHOD: + case UNKNOWN_METHOD: + break; + } + + return size; +} + +/** Initialize all compression modules. */ +void +tor_compress_init(void) +{ + atomic_counter_init(&total_compress_allocation); + + tor_zlib_init(); + tor_lzma_init(); + tor_zstd_init(); +} + |