1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       block_decoder.c
4/// \brief      Decodes .xz Blocks
5//
6//  Author:     Lasse Collin
7//
8//  This file has been put into the public domain.
9//  You can do whatever you want with this file.
10//
11///////////////////////////////////////////////////////////////////////////////
12
13#include "block_decoder.h"
14#include "filter_decoder.h"
15#include "check.h"
16
17
18struct lzma_coder_s {
19	enum {
20		SEQ_CODE,
21		SEQ_PADDING,
22		SEQ_CHECK,
23	} sequence;
24
25	/// The filters in the chain; initialized with lzma_raw_decoder_init().
26	lzma_next_coder next;
27
28	/// Decoding options; we also write Compressed Size and Uncompressed
29	/// Size back to this structure when the decoding has been finished.
30	lzma_block *block;
31
32	/// Compressed Size calculated while decoding
33	lzma_vli compressed_size;
34
35	/// Uncompressed Size calculated while decoding
36	lzma_vli uncompressed_size;
37
38	/// Maximum allowed Compressed Size; this takes into account the
39	/// size of the Block Header and Check fields when Compressed Size
40	/// is unknown.
41	lzma_vli compressed_limit;
42
43	/// Position when reading the Check field
44	size_t check_pos;
45
46	/// Check of the uncompressed data
47	lzma_check_state check;
48};
49
50
51static inline bool
52update_size(lzma_vli *size, lzma_vli add, lzma_vli limit)
53{
54	if (limit > LZMA_VLI_MAX)
55		limit = LZMA_VLI_MAX;
56
57	if (limit < *size || limit - *size < add)
58		return true;
59
60	*size += add;
61
62	return false;
63}
64
65
66static inline bool
67is_size_valid(lzma_vli size, lzma_vli reference)
68{
69	return reference == LZMA_VLI_UNKNOWN || reference == size;
70}
71
72
73static lzma_ret
74block_decode(lzma_coder *coder, lzma_allocator *allocator,
75		const uint8_t *restrict in, size_t *restrict in_pos,
76		size_t in_size, uint8_t *restrict out,
77		size_t *restrict out_pos, size_t out_size, lzma_action action)
78{
79	switch (coder->sequence) {
80	case SEQ_CODE: {
81		const size_t in_start = *in_pos;
82		const size_t out_start = *out_pos;
83
84		const lzma_ret ret = coder->next.code(coder->next.coder,
85				allocator, in, in_pos, in_size,
86				out, out_pos, out_size, action);
87
88		const size_t in_used = *in_pos - in_start;
89		const size_t out_used = *out_pos - out_start;
90
91		// NOTE: We compare to compressed_limit here, which prevents
92		// the total size of the Block growing past LZMA_VLI_MAX.
93		if (update_size(&coder->compressed_size, in_used,
94					coder->compressed_limit)
95				|| update_size(&coder->uncompressed_size,
96					out_used,
97					coder->block->uncompressed_size))
98			return LZMA_DATA_ERROR;
99
100		lzma_check_update(&coder->check, coder->block->check,
101				out + out_start, out_used);
102
103		if (ret != LZMA_STREAM_END)
104			return ret;
105
106		// Compressed and Uncompressed Sizes are now at their final
107		// values. Verify that they match the values given to us.
108		if (!is_size_valid(coder->compressed_size,
109					coder->block->compressed_size)
110				|| !is_size_valid(coder->uncompressed_size,
111					coder->block->uncompressed_size))
112			return LZMA_DATA_ERROR;
113
114		// Copy the values into coder->block. The caller
115		// may use this information to construct Index.
116		coder->block->compressed_size = coder->compressed_size;
117		coder->block->uncompressed_size = coder->uncompressed_size;
118
119		coder->sequence = SEQ_PADDING;
120	}
121
122	// Fall through
123
124	case SEQ_PADDING:
125		// Compressed Data is padded to a multiple of four bytes.
126		while (coder->compressed_size & 3) {
127			if (*in_pos >= in_size)
128				return LZMA_OK;
129
130			// We use compressed_size here just get the Padding
131			// right. The actual Compressed Size was stored to
132			// coder->block already, and won't be modified by
133			// us anymore.
134			++coder->compressed_size;
135
136			if (in[(*in_pos)++] != 0x00)
137				return LZMA_DATA_ERROR;
138		}
139
140		if (coder->block->check == LZMA_CHECK_NONE)
141			return LZMA_STREAM_END;
142
143		lzma_check_finish(&coder->check, coder->block->check);
144		coder->sequence = SEQ_CHECK;
145
146	// Fall through
147
148	case SEQ_CHECK: {
149		const size_t check_size = lzma_check_size(coder->block->check);
150		lzma_bufcpy(in, in_pos, in_size, coder->block->raw_check,
151				&coder->check_pos, check_size);
152		if (coder->check_pos < check_size)
153			return LZMA_OK;
154
155		// Validate the Check only if we support it.
156		// coder->check.buffer may be uninitialized
157		// when the Check ID is not supported.
158		if (lzma_check_is_supported(coder->block->check)
159				&& memcmp(coder->block->raw_check,
160					coder->check.buffer.u8,
161					check_size) != 0)
162			return LZMA_DATA_ERROR;
163
164		return LZMA_STREAM_END;
165	}
166	}
167
168	return LZMA_PROG_ERROR;
169}
170
171
172static void
173block_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
174{
175	lzma_next_end(&coder->next, allocator);
176	lzma_free(coder, allocator);
177	return;
178}
179
180
181extern lzma_ret
182lzma_block_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
183		lzma_block *block)
184{
185	lzma_next_coder_init(&lzma_block_decoder_init, next, allocator);
186
187	// Validate the options. lzma_block_unpadded_size() does that for us
188	// except for Uncompressed Size and filters. Filters are validated
189	// by the raw decoder.
190	if (lzma_block_unpadded_size(block) == 0
191			|| !lzma_vli_is_valid(block->uncompressed_size))
192		return LZMA_PROG_ERROR;
193
194	// Allocate and initialize *next->coder if needed.
195	if (next->coder == NULL) {
196		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
197		if (next->coder == NULL)
198			return LZMA_MEM_ERROR;
199
200		next->code = &block_decode;
201		next->end = &block_decoder_end;
202		next->coder->next = LZMA_NEXT_CODER_INIT;
203	}
204
205	// Basic initializations
206	next->coder->sequence = SEQ_CODE;
207	next->coder->block = block;
208	next->coder->compressed_size = 0;
209	next->coder->uncompressed_size = 0;
210
211	// If Compressed Size is not known, we calculate the maximum allowed
212	// value so that encoded size of the Block (including Block Padding)
213	// is still a valid VLI and a multiple of four.
214	next->coder->compressed_limit
215			= block->compressed_size == LZMA_VLI_UNKNOWN
216				? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
217					- block->header_size
218					- lzma_check_size(block->check)
219				: block->compressed_size;
220
221	// Initialize the check. It's caller's problem if the Check ID is not
222	// supported, and the Block decoder cannot verify the Check field.
223	// Caller can test lzma_check_is_supported(block->check).
224	next->coder->check_pos = 0;
225	lzma_check_init(&next->coder->check, block->check);
226
227	// Initialize the filter chain.
228	return lzma_raw_decoder_init(&next->coder->next, allocator,
229			block->filters);
230}
231
232
233extern LZMA_API(lzma_ret)
234lzma_block_decoder(lzma_stream *strm, lzma_block *block)
235{
236	lzma_next_strm_init(lzma_block_decoder_init, strm, block);
237
238	strm->internal->supported_actions[LZMA_RUN] = true;
239	strm->internal->supported_actions[LZMA_FINISH] = true;
240
241	return LZMA_OK;
242}
243