1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file alone_decoder.c
4 /// \brief Decoder for LZMA_Alone files
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 "alone_decoder.h"
14 #include "lzma_decoder.h"
15 #include "lz_decoder.h"
16
17
18 typedef struct {
19 lzma_next_coder next;
20
21 enum {
22 SEQ_PROPERTIES,
23 SEQ_DICTIONARY_SIZE,
24 SEQ_UNCOMPRESSED_SIZE,
25 SEQ_CODER_INIT,
26 SEQ_CODE,
27 } sequence;
28
29 /// If true, reject files that are unlikely to be .lzma files.
30 /// If false, more non-.lzma files get accepted and will give
31 /// LZMA_DATA_ERROR either immediately or after a few output bytes.
32 bool picky;
33
34 /// Position in the header fields
35 size_t pos;
36
37 /// Uncompressed size decoded from the header
38 lzma_vli uncompressed_size;
39
40 /// Memory usage limit
41 uint64_t memlimit;
42
43 /// Amount of memory actually needed (only an estimate)
44 uint64_t memusage;
45
46 /// Options decoded from the header needed to initialize
47 /// the LZMA decoder
48 lzma_options_lzma options;
49 } lzma_alone_coder;
50
51
52 static lzma_ret
53 alone_decode(void *coder_ptr, const lzma_allocator *allocator,
54 const uint8_t *restrict in, size_t *restrict in_pos,
55 size_t in_size, uint8_t *restrict out,
56 size_t *restrict out_pos, size_t out_size,
57 lzma_action action)
58 {
59 lzma_alone_coder *coder = coder_ptr;
60
61 while (*out_pos < out_size
62 && (coder->sequence == SEQ_CODE || *in_pos < in_size))
63 switch (coder->sequence) {
64 case SEQ_PROPERTIES:
65 if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
66 return LZMA_FORMAT_ERROR;
67
68 coder->sequence = SEQ_DICTIONARY_SIZE;
69 ++*in_pos;
70 break;
71
72 case SEQ_DICTIONARY_SIZE:
73 coder->options.dict_size
74 |= (size_t)(in[*in_pos]) << (coder->pos * 8);
75
76 if (++coder->pos == 4) {
77 if (coder->picky && coder->options.dict_size
78 != UINT32_MAX) {
79 // A hack to ditch tons of false positives:
80 // We allow only dictionary sizes that are
81 // 2^n or 2^n + 2^(n-1). LZMA_Alone created
82 // only files with 2^n, but accepts any
83 // dictionary size.
84 uint32_t d = coder->options.dict_size - 1;
85 d |= d >> 2;
86 d |= d >> 3;
87 d |= d >> 4;
88 d |= d >> 8;
89 d |= d >> 16;
90 ++d;
91
92 if (d != coder->options.dict_size)
93 return LZMA_FORMAT_ERROR;
94 }
95
96 coder->pos = 0;
97 coder->sequence = SEQ_UNCOMPRESSED_SIZE;
98 }
99
100 ++*in_pos;
101 break;
102
103 case SEQ_UNCOMPRESSED_SIZE:
104 coder->uncompressed_size
105 |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
106 ++*in_pos;
107 if (++coder->pos < 8)
108 break;
109
110 // Another hack to ditch false positives: Assume that
111 // if the uncompressed size is known, it must be less
112 // than 256 GiB.
113 //
114 // FIXME? Without picky we allow > LZMA_VLI_MAX which doesn't
115 // really matter in this specific situation (> LZMA_VLI_MAX is
116 // safe in the LZMA decoder) but it's somewhat weird still.
117 if (coder->picky
118 && coder->uncompressed_size != LZMA_VLI_UNKNOWN
119 && coder->uncompressed_size
120 >= (LZMA_VLI_C(1) << 38))
121 return LZMA_FORMAT_ERROR;
122
123 // Use LZMA_FILTER_LZMA1EXT features to specify the
124 // uncompressed size and that the end marker is allowed
125 // even when the uncompressed size is known. Both .lzma
126 // header and LZMA1EXT use UINT64_MAX indicate that size
127 // is unknown.
128 coder->options.ext_flags = LZMA_LZMA1EXT_ALLOW_EOPM;
129 lzma_set_ext_size(coder->options, coder->uncompressed_size);
130
131 // Calculate the memory usage so that it is ready
132 // for SEQ_CODER_INIT.
133 coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
134 + LZMA_MEMUSAGE_BASE;
135
136 coder->pos = 0;
137 coder->sequence = SEQ_CODER_INIT;
138
139 // Fall through
140
141 case SEQ_CODER_INIT: {
142 if (coder->memusage > coder->memlimit)
143 return LZMA_MEMLIMIT_ERROR;
144
145 lzma_filter_info filters[2] = {
146 {
147 .id = LZMA_FILTER_LZMA1EXT,
148 .init = &lzma_lzma_decoder_init,
149 .options = &coder->options,
150 }, {
151 .init = NULL,
152 }
153 };
154
155 return_if_error(lzma_next_filter_init(&coder->next,
156 allocator, filters));
157
158 coder->sequence = SEQ_CODE;
159 break;
160 }
161
162 case SEQ_CODE: {
163 return coder->next.code(coder->next.coder,
164 allocator, in, in_pos, in_size,
165 out, out_pos, out_size, action);
166 }
167
168 default:
169 return LZMA_PROG_ERROR;
170 }
171
172 return LZMA_OK;
173 }
174
175
176 static void
177 alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
178 {
179 lzma_alone_coder *coder = coder_ptr;
180 lzma_next_end(&coder->next, allocator);
181 lzma_free(coder, allocator);
182 return;
183 }
184
185
186 static lzma_ret
187 alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
188 uint64_t *old_memlimit, uint64_t new_memlimit)
189 {
190 lzma_alone_coder *coder = coder_ptr;
191
192 *memusage = coder->memusage;
193 *old_memlimit = coder->memlimit;
194
195 if (new_memlimit != 0) {
196 if (new_memlimit < coder->memusage)
197 return LZMA_MEMLIMIT_ERROR;
198
199 coder->memlimit = new_memlimit;
200 }
201
202 return LZMA_OK;
203 }
204
205
206 extern lzma_ret
207 lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
208 uint64_t memlimit, bool picky)
209 {
210 lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
211
212 lzma_alone_coder *coder = next->coder;
213
214 if (coder == NULL) {
215 coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
216 if (coder == NULL)
217 return LZMA_MEM_ERROR;
218
219 next->coder = coder;
220 next->code = &alone_decode;
221 next->end = &alone_decoder_end;
222 next->memconfig = &alone_decoder_memconfig;
223 coder->next = LZMA_NEXT_CODER_INIT;
224 }
225
226 coder->sequence = SEQ_PROPERTIES;
227 coder->picky = picky;
228 coder->pos = 0;
229 coder->options.dict_size = 0;
230 coder->options.preset_dict = NULL;
231 coder->options.preset_dict_size = 0;
232 coder->uncompressed_size = 0;
233 coder->memlimit = my_max(1, memlimit);
234 coder->memusage = LZMA_MEMUSAGE_BASE;
235
236 return LZMA_OK;
237 }
238
239
240 extern LZMA_API(lzma_ret)
241 lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
242 {
243 lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);
244
245 strm->internal->supported_actions[LZMA_RUN] = true;
246 strm->internal->supported_actions[LZMA_FINISH] = true;
247
248 return LZMA_OK;
249 }