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
alone_decode(void * coder_ptr,const lzma_allocator * allocator lzma_attribute ((__unused__)),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)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
alone_decoder_end(void * coder_ptr,const lzma_allocator * allocator)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
alone_decoder_memconfig(void * coder_ptr,uint64_t * memusage,uint64_t * old_memlimit,uint64_t new_memlimit)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
lzma_alone_decoder_init(lzma_next_coder * next,const lzma_allocator * allocator,uint64_t memlimit,bool picky)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)
lzma_alone_decoder(lzma_stream * strm,uint64_t memlimit)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 }
244