1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file       index_hash.c
4 /// \brief      Validates Index by using a hash function
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 "common.h"
14 #include "index.h"
15 #include "check.h"
16 
17 
18 typedef struct {
19 	/// Sum of the Block sizes (including Block Padding)
20 	lzma_vli blocks_size;
21 
22 	/// Sum of the Uncompressed Size fields
23 	lzma_vli uncompressed_size;
24 
25 	/// Number of Records
26 	lzma_vli count;
27 
28 	/// Size of the List of Index Records as bytes
29 	lzma_vli index_list_size;
30 
31 	/// Check calculated from Unpadded Sizes and Uncompressed Sizes.
32 	lzma_check_state check;
33 
34 } lzma_index_hash_info;
35 
36 
37 struct lzma_index_hash_s {
38 	enum {
39 		SEQ_BLOCK,
40 		SEQ_COUNT,
41 		SEQ_UNPADDED,
42 		SEQ_UNCOMPRESSED,
43 		SEQ_PADDING_INIT,
44 		SEQ_PADDING,
45 		SEQ_CRC32,
46 	} sequence;
47 
48 	/// Information collected while decoding the actual Blocks.
49 	lzma_index_hash_info blocks;
50 
51 	/// Information collected from the Index field.
52 	lzma_index_hash_info records;
53 
54 	/// Number of Records not fully decoded
55 	lzma_vli remaining;
56 
57 	/// Unpadded Size currently being read from an Index Record.
58 	lzma_vli unpadded_size;
59 
60 	/// Uncompressed Size currently being read from an Index Record.
61 	lzma_vli uncompressed_size;
62 
63 	/// Position in variable-length integers when decoding them from
64 	/// the List of Records.
65 	size_t pos;
66 
67 	/// CRC32 of the Index
68 	uint32_t crc32;
69 };
70 
71 
72 extern LZMA_API(lzma_index_hash *)
73 lzma_index_hash_init(lzma_index_hash *index_hash,
74 		const lzma_allocator *allocator)
75 {
76 	if (index_hash == NULL) {
77 		index_hash = lzma_alloc(sizeof(lzma_index_hash), allocator);
78 		if (index_hash == NULL)
79 			return NULL;
80 	}
81 
82 	index_hash->sequence = SEQ_BLOCK;
83 	index_hash->blocks.blocks_size = 0;
84 	index_hash->blocks.uncompressed_size = 0;
85 	index_hash->blocks.count = 0;
86 	index_hash->blocks.index_list_size = 0;
87 	index_hash->records.blocks_size = 0;
88 	index_hash->records.uncompressed_size = 0;
89 	index_hash->records.count = 0;
90 	index_hash->records.index_list_size = 0;
91 	index_hash->unpadded_size = 0;
92 	index_hash->uncompressed_size = 0;
93 	index_hash->pos = 0;
94 	index_hash->crc32 = 0;
95 
96 	// These cannot fail because LZMA_CHECK_BEST is known to be supported.
97 	(void)lzma_check_init(&index_hash->blocks.check, LZMA_CHECK_BEST);
98 	(void)lzma_check_init(&index_hash->records.check, LZMA_CHECK_BEST);
99 
100 	return index_hash;
101 }
102 
103 
104 extern LZMA_API(void)
105 lzma_index_hash_end(lzma_index_hash *index_hash,
106 		const lzma_allocator *allocator)
107 {
108 	lzma_free(index_hash, allocator);
109 	return;
110 }
111 
112 
113 extern LZMA_API(lzma_vli)
114 lzma_index_hash_size(const lzma_index_hash *index_hash)
115 {
116 	// Get the size of the Index from ->blocks instead of ->records for
117 	// cases where application wants to know the Index Size before
118 	// decoding the Index.
119 	return index_size(index_hash->blocks.count,
120 			index_hash->blocks.index_list_size);
121 }
122 
123 
124 /// Updates the sizes and the hash without any validation.
125 static lzma_ret
126 hash_append(lzma_index_hash_info *info, lzma_vli unpadded_size,
127 		lzma_vli uncompressed_size)
128 {
129 	info->blocks_size += vli_ceil4(unpadded_size);
130 	info->uncompressed_size += uncompressed_size;
131 	info->index_list_size += lzma_vli_size(unpadded_size)
132 			+ lzma_vli_size(uncompressed_size);
133 	++info->count;
134 
135 	const lzma_vli sizes[2] = { unpadded_size, uncompressed_size };
136 	lzma_check_update(&info->check, LZMA_CHECK_BEST,
137 			(const uint8_t *)(sizes), sizeof(sizes));
138 
139 	return LZMA_OK;
140 }
141 
142 
143 extern LZMA_API(lzma_ret)
144 lzma_index_hash_append(lzma_index_hash *index_hash, lzma_vli unpadded_size,
145 		lzma_vli uncompressed_size)
146 {
147 	// Validate the arguments.
148 	if (index_hash->sequence != SEQ_BLOCK
149 			|| unpadded_size < UNPADDED_SIZE_MIN
150 			|| unpadded_size > UNPADDED_SIZE_MAX
151 			|| uncompressed_size > LZMA_VLI_MAX)
152 		return LZMA_PROG_ERROR;
153 
154 	// Update the hash.
155 	return_if_error(hash_append(&index_hash->blocks,
156 			unpadded_size, uncompressed_size));
157 
158 	// Validate the properties of *info are still in allowed limits.
159 	if (index_hash->blocks.blocks_size > LZMA_VLI_MAX
160 			|| index_hash->blocks.uncompressed_size > LZMA_VLI_MAX
161 			|| index_size(index_hash->blocks.count,
162 					index_hash->blocks.index_list_size)
163 				> LZMA_BACKWARD_SIZE_MAX
164 			|| index_stream_size(index_hash->blocks.blocks_size,
165 					index_hash->blocks.count,
166 					index_hash->blocks.index_list_size)
167 				> LZMA_VLI_MAX)
168 		return LZMA_DATA_ERROR;
169 
170 	return LZMA_OK;
171 }
172 
173 
174 extern LZMA_API(lzma_ret)
175 lzma_index_hash_decode(lzma_index_hash *index_hash, const uint8_t *in,
176 		size_t *in_pos, size_t in_size)
177 {
178 	// Catch zero input buffer here, because in contrast to Index encoder
179 	// and decoder functions, applications call this function directly
180 	// instead of via lzma_code(), which does the buffer checking.
181 	if (*in_pos >= in_size)
182 		return LZMA_BUF_ERROR;
183 
184 	// NOTE: This function has many similarities to index_encode() and
185 	// index_decode() functions found from index_encoder.c and
186 	// index_decoder.c. See the comments especially in index_encoder.c.
187 	const size_t in_start = *in_pos;
188 	lzma_ret ret = LZMA_OK;
189 
190 	while (*in_pos < in_size)
191 	switch (index_hash->sequence) {
192 	case SEQ_BLOCK:
193 		// Check the Index Indicator is present.
194 		if (in[(*in_pos)++] != 0x00)
195 			return LZMA_DATA_ERROR;
196 
197 		index_hash->sequence = SEQ_COUNT;
198 		break;
199 
200 	case SEQ_COUNT: {
201 		ret = lzma_vli_decode(&index_hash->remaining,
202 				&index_hash->pos, in, in_pos, in_size);
203 		if (ret != LZMA_STREAM_END)
204 			goto out;
205 
206 		// The count must match the count of the Blocks decoded.
207 		if (index_hash->remaining != index_hash->blocks.count)
208 			return LZMA_DATA_ERROR;
209 
210 		ret = LZMA_OK;
211 		index_hash->pos = 0;
212 
213 		// Handle the special case when there are no Blocks.
214 		index_hash->sequence = index_hash->remaining == 0
215 				? SEQ_PADDING_INIT : SEQ_UNPADDED;
216 		break;
217 	}
218 
219 	case SEQ_UNPADDED:
220 	case SEQ_UNCOMPRESSED: {
221 		lzma_vli *size = index_hash->sequence == SEQ_UNPADDED
222 				? &index_hash->unpadded_size
223 				: &index_hash->uncompressed_size;
224 
225 		ret = lzma_vli_decode(size, &index_hash->pos,
226 				in, in_pos, in_size);
227 		if (ret != LZMA_STREAM_END)
228 			goto out;
229 
230 		ret = LZMA_OK;
231 		index_hash->pos = 0;
232 
233 		if (index_hash->sequence == SEQ_UNPADDED) {
234 			if (index_hash->unpadded_size < UNPADDED_SIZE_MIN
235 					|| index_hash->unpadded_size
236 						> UNPADDED_SIZE_MAX)
237 				return LZMA_DATA_ERROR;
238 
239 			index_hash->sequence = SEQ_UNCOMPRESSED;
240 		} else {
241 			// Update the hash.
242 			return_if_error(hash_append(&index_hash->records,
243 					index_hash->unpadded_size,
244 					index_hash->uncompressed_size));
245 
246 			// Verify that we don't go over the known sizes. Note
247 			// that this validation is simpler than the one used
248 			// in lzma_index_hash_append(), because here we know
249 			// that values in index_hash->blocks are already
250 			// validated and we are fine as long as we don't
251 			// exceed them in index_hash->records.
252 			if (index_hash->blocks.blocks_size
253 					< index_hash->records.blocks_size
254 					|| index_hash->blocks.uncompressed_size
255 					< index_hash->records.uncompressed_size
256 					|| index_hash->blocks.index_list_size
257 					< index_hash->records.index_list_size)
258 				return LZMA_DATA_ERROR;
259 
260 			// Check if this was the last Record.
261 			index_hash->sequence = --index_hash->remaining == 0
262 					? SEQ_PADDING_INIT : SEQ_UNPADDED;
263 		}
264 
265 		break;
266 	}
267 
268 	case SEQ_PADDING_INIT:
269 		index_hash->pos = (LZMA_VLI_C(4) - index_size_unpadded(
270 				index_hash->records.count,
271 				index_hash->records.index_list_size)) & 3;
272 		index_hash->sequence = SEQ_PADDING;
273 
274 	// Fall through
275 
276 	case SEQ_PADDING:
277 		if (index_hash->pos > 0) {
278 			--index_hash->pos;
279 			if (in[(*in_pos)++] != 0x00)
280 				return LZMA_DATA_ERROR;
281 
282 			break;
283 		}
284 
285 		// Compare the sizes.
286 		if (index_hash->blocks.blocks_size
287 				!= index_hash->records.blocks_size
288 				|| index_hash->blocks.uncompressed_size
289 				!= index_hash->records.uncompressed_size
290 				|| index_hash->blocks.index_list_size
291 				!= index_hash->records.index_list_size)
292 			return LZMA_DATA_ERROR;
293 
294 		// Finish the hashes and compare them.
295 		lzma_check_finish(&index_hash->blocks.check, LZMA_CHECK_BEST);
296 		lzma_check_finish(&index_hash->records.check, LZMA_CHECK_BEST);
297 		if (memcmp(index_hash->blocks.check.buffer.u8,
298 				index_hash->records.check.buffer.u8,
299 				lzma_check_size(LZMA_CHECK_BEST)) != 0)
300 			return LZMA_DATA_ERROR;
301 
302 		// Finish the CRC32 calculation.
303 		index_hash->crc32 = lzma_crc32(in + in_start,
304 				*in_pos - in_start, index_hash->crc32);
305 
306 		index_hash->sequence = SEQ_CRC32;
307 
308 	// Fall through
309 
310 	case SEQ_CRC32:
311 		do {
312 			if (*in_pos == in_size)
313 				return LZMA_OK;
314 
315 			if (((index_hash->crc32 >> (index_hash->pos * 8))
316 					& 0xFF) != in[(*in_pos)++])
317 				return LZMA_DATA_ERROR;
318 
319 		} while (++index_hash->pos < 4);
320 
321 		return LZMA_STREAM_END;
322 
323 	default:
324 		assert(0);
325 		return LZMA_PROG_ERROR;
326 	}
327 
328 out:
329 	// Update the CRC32,
330 	index_hash->crc32 = lzma_crc32(in + in_start,
331 			*in_pos - in_start, index_hash->crc32);
332 
333 	return ret;
334 }
335