diff options
Diffstat (limited to '')
| -rw-r--r-- | epan/tvbuff_lz77.c | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/epan/tvbuff_lz77.c b/epan/tvbuff_lz77.c new file mode 100644 index 00000000..08e711ca --- /dev/null +++ b/epan/tvbuff_lz77.c @@ -0,0 +1,157 @@ +/* + * Decompression code for Plain LZ77. This encoding is used by + * Microsoft in various file formats and protocols including SMB3. + * + * See MS-XCA. + * + * Copyright (C) 2019 Aurélien Aptel + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +#include <glib.h> +#include <epan/exceptions.h> +#include <epan/tvbuff.h> +#include <epan/wmem_scopes.h> + +#define MAX_INPUT_SIZE (16*1024*1024) /* 16MB */ + +static gboolean do_uncompress(tvbuff_t *tvb, int offset, int in_size, + wmem_array_t *obuf) +{ + guint buf_flags = 0, buf_flag_count = 0; + int in_off = 0; + int last_length_half_byte = 0; + guint match_bytes, match_len, match_off; + guint i; + + if (!tvb) + return FALSE; + + if (!in_size || in_size > MAX_INPUT_SIZE) + return FALSE; + + while (1) { + if (buf_flag_count == 0) { + buf_flags = tvb_get_letohl(tvb, offset+in_off); + in_off += 4; + buf_flag_count = 32; + } + buf_flag_count--; + if ((buf_flags & (1u << buf_flag_count)) == 0) { + guint8 v = tvb_get_guint8(tvb, offset+in_off); + wmem_array_append_one(obuf, v); + in_off++; + } else { + if (in_off == in_size) + return TRUE; + match_bytes = tvb_get_letohs(tvb, offset+in_off); + in_off += 2; + match_len = match_bytes % 8; + match_off = (match_bytes/8) + 1; + if (match_len == 7) { + if (last_length_half_byte == 0) { + match_len = tvb_get_guint8(tvb, offset+in_off); + match_len = match_len % 16; + last_length_half_byte = in_off; + in_off++; + } else { + match_len = tvb_get_guint8(tvb, offset+last_length_half_byte); + match_len = match_len / 16; + last_length_half_byte = 0; + } + if (match_len == 15) { + match_len = tvb_get_guint8(tvb, offset+in_off); + in_off++; + if (match_len == 255) { + match_len = tvb_get_letohs(tvb, offset+in_off); + in_off += 2; + if (match_len == 0) { + /* This case isn't documented */ + match_len = tvb_get_letohs(tvb, offset+in_off); + in_off += 4; + } + if (match_len < 15+7) + return FALSE; + match_len -= (15 + 7); + } + match_len += 15; + } + match_len += 7; + } + match_len += 3; + for (i = 0; i < match_len; i++) { + guint8 byte; + if (match_off > wmem_array_get_count(obuf)) + return FALSE; + if (wmem_array_try_index(obuf, wmem_array_get_count(obuf)-match_off, &byte)) + return FALSE; + wmem_array_append_one(obuf, byte); + } + } + } + + return TRUE; +} + +tvbuff_t * +tvb_uncompress_lz77(tvbuff_t *tvb, const int offset, int in_size) +{ + volatile gboolean ok = FALSE; + wmem_allocator_t *pool; + wmem_array_t *obuf; + tvbuff_t *out; + + pool = wmem_allocator_new(WMEM_ALLOCATOR_SIMPLE); + obuf = wmem_array_sized_new(pool, 1, in_size*2); + + TRY { + ok = do_uncompress(tvb, offset, in_size, obuf); + } CATCH_ALL { + ok = FALSE; + } + ENDTRY; + + if (ok) { + /* + * Cannot pass a tvb free callback that frees the wmem + * pool, so we make an extra copy that uses bare + * pointers. This could be optimized if tvb API had a + * free pool callback of some sort. + */ + guint size = wmem_array_get_count(obuf); + guint8 *p = (guint8 *)g_malloc(size); + memcpy(p, wmem_array_get_raw(obuf), size); + out = tvb_new_real_data(p, size, size); + tvb_set_free_cb(out, g_free); + } else { + out = NULL; + } + + wmem_destroy_allocator(pool); + + return out; +} + +tvbuff_t * +tvb_child_uncompress_lz77(tvbuff_t *parent, tvbuff_t *tvb, const int offset, int in_size) +{ + tvbuff_t *new_tvb = tvb_uncompress_lz77(tvb, offset, in_size); + 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: + */ |