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
18 typedef struct {
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 /// True if the integrity check won't be calculated and verified.
50 bool ignore_check;
51 } lzma_block_coder;
52
53
54 static inline bool
update_size(lzma_vli * size,lzma_vli add,lzma_vli limit)55 update_size(lzma_vli *size, lzma_vli add, lzma_vli limit)
56 {
57 if (limit > LZMA_VLI_MAX)
58 limit = LZMA_VLI_MAX;
59
60 if (limit < *size || limit - *size < add)
61 return true;
62
63 *size += add;
64
65 return false;
66 }
67
68
69 static inline bool
is_size_valid(lzma_vli size,lzma_vli reference)70 is_size_valid(lzma_vli size, lzma_vli reference)
71 {
72 return reference == LZMA_VLI_UNKNOWN || reference == size;
73 }
74
75
76 static lzma_ret
block_decode(void * coder_ptr,const lzma_allocator * allocator,const uint8_t * restrict in,size_t * restrict in_pos,size_t in_size,uint8_t * restrict out,size_t * restrict out_pos,size_t out_size,lzma_action action)77 block_decode(void *coder_ptr, const lzma_allocator *allocator,
78 const uint8_t *restrict in, size_t *restrict in_pos,
79 size_t in_size, uint8_t *restrict out,
80 size_t *restrict out_pos, size_t out_size, lzma_action action)
81 {
82 lzma_block_coder *coder = coder_ptr;
83
84 switch (coder->sequence) {
85 case SEQ_CODE: {
86 const size_t in_start = *in_pos;
87 const size_t out_start = *out_pos;
88
89 const lzma_ret ret = coder->next.code(coder->next.coder,
90 allocator, in, in_pos, in_size,
91 out, out_pos, out_size, action);
92
93 const size_t in_used = *in_pos - in_start;
94 const size_t out_used = *out_pos - out_start;
95
96 // NOTE: We compare to compressed_limit here, which prevents
97 // the total size of the Block growing past LZMA_VLI_MAX.
98 if (update_size(&coder->compressed_size, in_used,
99 coder->compressed_limit)
100 || update_size(&coder->uncompressed_size,
101 out_used,
102 coder->block->uncompressed_size))
103 return LZMA_DATA_ERROR;
104
105 if (!coder->ignore_check)
106 lzma_check_update(&coder->check, coder->block->check,
107 out + out_start, out_used);
108
109 if (ret != LZMA_STREAM_END)
110 return ret;
111
112 // Compressed and Uncompressed Sizes are now at their final
113 // values. Verify that they match the values given to us.
114 if (!is_size_valid(coder->compressed_size,
115 coder->block->compressed_size)
116 || !is_size_valid(coder->uncompressed_size,
117 coder->block->uncompressed_size))
118 return LZMA_DATA_ERROR;
119
120 // Copy the values into coder->block. The caller
121 // may use this information to construct Index.
122 coder->block->compressed_size = coder->compressed_size;
123 coder->block->uncompressed_size = coder->uncompressed_size;
124
125 coder->sequence = SEQ_PADDING;
126 }
127
128 // Fall through
129
130 case SEQ_PADDING:
131 // Compressed Data is padded to a multiple of four bytes.
132 while (coder->compressed_size & 3) {
133 if (*in_pos >= in_size)
134 return LZMA_OK;
135
136 // We use compressed_size here just get the Padding
137 // right. The actual Compressed Size was stored to
138 // coder->block already, and won't be modified by
139 // us anymore.
140 ++coder->compressed_size;
141
142 if (in[(*in_pos)++] != 0x00)
143 return LZMA_DATA_ERROR;
144 }
145
146 if (coder->block->check == LZMA_CHECK_NONE)
147 return LZMA_STREAM_END;
148
149 if (!coder->ignore_check)
150 lzma_check_finish(&coder->check, coder->block->check);
151
152 coder->sequence = SEQ_CHECK;
153
154 // Fall through
155
156 case SEQ_CHECK: {
157 const size_t check_size = lzma_check_size(coder->block->check);
158 lzma_bufcpy(in, in_pos, in_size, coder->block->raw_check,
159 &coder->check_pos, check_size);
160 if (coder->check_pos < check_size)
161 return LZMA_OK;
162
163 // Validate the Check only if we support it.
164 // coder->check.buffer may be uninitialized
165 // when the Check ID is not supported.
166 if (!coder->ignore_check
167 && lzma_check_is_supported(coder->block->check)
168 && memcmp(coder->block->raw_check,
169 coder->check.buffer.u8,
170 check_size) != 0)
171 return LZMA_DATA_ERROR;
172
173 return LZMA_STREAM_END;
174 }
175 }
176
177 return LZMA_PROG_ERROR;
178 }
179
180
181 static void
block_decoder_end(void * coder_ptr,const lzma_allocator * allocator)182 block_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
183 {
184 lzma_block_coder *coder = coder_ptr;
185 lzma_next_end(&coder->next, allocator);
186 lzma_free(coder, allocator);
187 return;
188 }
189
190
191 extern lzma_ret
lzma_block_decoder_init(lzma_next_coder * next,const lzma_allocator * allocator,lzma_block * block)192 lzma_block_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
193 lzma_block *block)
194 {
195 lzma_next_coder_init(&lzma_block_decoder_init, next, allocator);
196
197 // Validate the options. lzma_block_unpadded_size() does that for us
198 // except for Uncompressed Size and filters. Filters are validated
199 // by the raw decoder.
200 if (lzma_block_unpadded_size(block) == 0
201 || !lzma_vli_is_valid(block->uncompressed_size))
202 return LZMA_PROG_ERROR;
203
204 // Allocate *next->coder if needed.
205 lzma_block_coder *coder = next->coder;
206 if (coder == NULL) {
207 coder = lzma_alloc(sizeof(lzma_block_coder), allocator);
208 if (coder == NULL)
209 return LZMA_MEM_ERROR;
210
211 next->coder = coder;
212 next->code = &block_decode;
213 next->end = &block_decoder_end;
214 coder->next = LZMA_NEXT_CODER_INIT;
215 }
216
217 // Basic initializations
218 coder->sequence = SEQ_CODE;
219 coder->block = block;
220 coder->compressed_size = 0;
221 coder->uncompressed_size = 0;
222
223 // If Compressed Size is not known, we calculate the maximum allowed
224 // value so that encoded size of the Block (including Block Padding)
225 // is still a valid VLI and a multiple of four.
226 coder->compressed_limit
227 = block->compressed_size == LZMA_VLI_UNKNOWN
228 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
229 - block->header_size
230 - lzma_check_size(block->check)
231 : block->compressed_size;
232
233 // Initialize the check. It's caller's problem if the Check ID is not
234 // supported, and the Block decoder cannot verify the Check field.
235 // Caller can test lzma_check_is_supported(block->check).
236 coder->check_pos = 0;
237 lzma_check_init(&coder->check, block->check);
238
239 coder->ignore_check = block->version >= 1
240 ? block->ignore_check : false;
241
242 // Initialize the filter chain.
243 return lzma_raw_decoder_init(&coder->next, allocator,
244 block->filters);
245 }
246
247
248 extern LZMA_API(lzma_ret)
lzma_block_decoder(lzma_stream * strm,lzma_block * block)249 lzma_block_decoder(lzma_stream *strm, lzma_block *block)
250 {
251 lzma_next_strm_init(lzma_block_decoder_init, strm, block);
252
253 strm->internal->supported_actions[LZMA_RUN] = true;
254 strm->internal->supported_actions[LZMA_FINISH] = true;
255
256 return LZMA_OK;
257 }
258