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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,
54                 const lzma_allocator *allocator lzma_attribute((__unused__)),
55                 const uint8_t *restrict in, size_t *restrict in_pos,
56                 size_t in_size, uint8_t *restrict out,
57                 size_t *restrict out_pos, size_t out_size,
58                 lzma_action action)
59 {
60         lzma_alone_coder *coder = coder_ptr;
61
62         while (*out_pos < out_size
63                         && (coder->sequence == SEQ_CODE || *in_pos < in_size))
64         switch (coder->sequence) {
65         case SEQ_PROPERTIES:
66                 if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
67                         return LZMA_FORMAT_ERROR;
68
69                 coder->sequence = SEQ_DICTIONARY_SIZE;
70                 ++*in_pos;
71                 break;
72
73         case SEQ_DICTIONARY_SIZE:
74                 coder->options.dict_size
75                                 |= (size_t)(in[*in_pos]) << (coder->pos * 8);
76
77                 if (++coder->pos == 4) {
78                         if (coder->picky && coder->options.dict_size
79                                         != UINT32_MAX) {
80                                 // A hack to ditch tons of false positives:
81                                 // We allow only dictionary sizes that are
82                                 // 2^n or 2^n + 2^(n-1). LZMA_Alone created
83                                 // only files with 2^n, but accepts any
84                                 // dictionary size.
85                                 uint32_t d = coder->options.dict_size - 1;
86                                 d |= d >> 2;
87                                 d |= d >> 3;
88                                 d |= d >> 4;
89                                 d |= d >> 8;
90                                 d |= d >> 16;
91                                 ++d;
92
93                                 if (d != coder->options.dict_size)
94                                         return LZMA_FORMAT_ERROR;
95                         }
96
97                         coder->pos = 0;
98                         coder->sequence = SEQ_UNCOMPRESSED_SIZE;
99                 }
100
101                 ++*in_pos;
102                 break;
103
104         case SEQ_UNCOMPRESSED_SIZE:
105                 coder->uncompressed_size
106                                 |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
107                 ++*in_pos;
108                 if (++coder->pos < 8)
109                         break;
110
111                 // Another hack to ditch false positives: Assume that
112                 // if the uncompressed size is known, it must be less
113                 // than 256 GiB.
114                 if (coder->picky
115                                 && coder->uncompressed_size != LZMA_VLI_UNKNOWN
116                                 && coder->uncompressed_size
117                                         >= (LZMA_VLI_C(1) << 38))
118                         return LZMA_FORMAT_ERROR;
119
120                 // Calculate the memory usage so that it is ready
121                 // for SEQ_CODER_INIT.
122                 coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
123                                 + LZMA_MEMUSAGE_BASE;
124
125                 coder->pos = 0;
126                 coder->sequence = SEQ_CODER_INIT;
127
128         // Fall through
129
130         case SEQ_CODER_INIT: {
131                 if (coder->memusage > coder->memlimit)
132                         return LZMA_MEMLIMIT_ERROR;
133
134                 lzma_filter_info filters[2] = {
135                         {
136                                 .init = &lzma_lzma_decoder_init,
137                                 .options = &coder->options,
138                         }, {
139                                 .init = NULL,
140                         }
141                 };
142
143                 const lzma_ret ret = lzma_next_filter_init(&coder->next,
144                                 allocator, filters);
145                 if (ret != LZMA_OK)
146                         return ret;
147
148                 // Use a hack to set the uncompressed size.
149                 lzma_lz_decoder_uncompressed(coder->next.coder,
150                                 coder->uncompressed_size);
151
152                 coder->sequence = SEQ_CODE;
153                 break;
154         }
155
156         case SEQ_CODE: {
157                 return coder->next.code(coder->next.coder,
158                                 allocator, in, in_pos, in_size,
159                                 out, out_pos, out_size, action);
160         }
161
162         default:
163                 return LZMA_PROG_ERROR;
164         }
165
166         return LZMA_OK;
167 }
168
169
170 static void
171 alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
172 {
173         lzma_alone_coder *coder = coder_ptr;
174         lzma_next_end(&coder->next, allocator);
175         lzma_free(coder, allocator);
176         return;
177 }
178
179
180 static lzma_ret
181 alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
182                 uint64_t *old_memlimit, uint64_t new_memlimit)
183 {
184         lzma_alone_coder *coder = coder_ptr;
185
186         *memusage = coder->memusage;
187         *old_memlimit = coder->memlimit;
188
189         if (new_memlimit != 0) {
190                 if (new_memlimit < coder->memusage)
191                         return LZMA_MEMLIMIT_ERROR;
192
193                 coder->memlimit = new_memlimit;
194         }
195
196         return LZMA_OK;
197 }
198
199
200 extern lzma_ret
201 lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
202                 uint64_t memlimit, bool picky)
203 {
204         lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
205
206         lzma_alone_coder *coder = next->coder;
207
208         if (coder == NULL) {
209                 coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
210                 if (coder == NULL)
211                         return LZMA_MEM_ERROR;
212
213                 next->coder = coder;
214                 next->code = &alone_decode;
215                 next->end = &alone_decoder_end;
216                 next->memconfig = &alone_decoder_memconfig;
217                 coder->next = LZMA_NEXT_CODER_INIT;
218         }
219
220         coder->sequence = SEQ_PROPERTIES;
221         coder->picky = picky;
222         coder->pos = 0;
223         coder->options.dict_size = 0;
224         coder->options.preset_dict = NULL;
225         coder->options.preset_dict_size = 0;
226         coder->uncompressed_size = 0;
227         coder->memlimit = my_max(1, memlimit);
228         coder->memusage = LZMA_MEMUSAGE_BASE;
229
230         return LZMA_OK;
231 }
232
233
234 extern LZMA_API(lzma_ret)
235 lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
236 {
237         lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);
238
239         strm->internal->supported_actions[LZMA_RUN] = true;
240         strm->internal->supported_actions[LZMA_FINISH] = true;
241
242         return LZMA_OK;
243 }