summaryrefslogtreecommitdiffstats
path: root/src/liblzma/common/alone_decoder.c
blob: 1dc85badf941650889caa60bf59f3efb44c71e14 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
///////////////////////////////////////////////////////////////////////////////
//
/// \file       alone_decoder.c
/// \brief      Decoder for LZMA_Alone files
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "alone_decoder.h"
#include "lzma_decoder.h"
#include "lz_decoder.h"


typedef struct {
	lzma_next_coder next;

	enum {
		SEQ_PROPERTIES,
		SEQ_DICTIONARY_SIZE,
		SEQ_UNCOMPRESSED_SIZE,
		SEQ_CODER_INIT,
		SEQ_CODE,
	} sequence;

	/// If true, reject files that are unlikely to be .lzma files.
	/// If false, more non-.lzma files get accepted and will give
	/// LZMA_DATA_ERROR either immediately or after a few output bytes.
	bool picky;

	/// Position in the header fields
	size_t pos;

	/// Uncompressed size decoded from the header
	lzma_vli uncompressed_size;

	/// Memory usage limit
	uint64_t memlimit;

	/// Amount of memory actually needed (only an estimate)
	uint64_t memusage;

	/// Options decoded from the header needed to initialize
	/// the LZMA decoder
	lzma_options_lzma options;
} lzma_alone_coder;


static lzma_ret
alone_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)
{
	lzma_alone_coder *coder = coder_ptr;

	while (*out_pos < out_size
			&& (coder->sequence == SEQ_CODE || *in_pos < in_size))
	switch (coder->sequence) {
	case SEQ_PROPERTIES:
		if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
			return LZMA_FORMAT_ERROR;

		coder->sequence = SEQ_DICTIONARY_SIZE;
		++*in_pos;
		break;

	case SEQ_DICTIONARY_SIZE:
		coder->options.dict_size
				|= (size_t)(in[*in_pos]) << (coder->pos * 8);

		if (++coder->pos == 4) {
			if (coder->picky && coder->options.dict_size
					!= UINT32_MAX) {
				// A hack to ditch tons of false positives:
				// We allow only dictionary sizes that are
				// 2^n or 2^n + 2^(n-1). LZMA_Alone created
				// only files with 2^n, but accepts any
				// dictionary size.
				uint32_t d = coder->options.dict_size - 1;
				d |= d >> 2;
				d |= d >> 3;
				d |= d >> 4;
				d |= d >> 8;
				d |= d >> 16;
				++d;

				if (d != coder->options.dict_size)
					return LZMA_FORMAT_ERROR;
			}

			coder->pos = 0;
			coder->sequence = SEQ_UNCOMPRESSED_SIZE;
		}

		++*in_pos;
		break;

	case SEQ_UNCOMPRESSED_SIZE:
		coder->uncompressed_size
				|= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
		++*in_pos;
		if (++coder->pos < 8)
			break;

		// Another hack to ditch false positives: Assume that
		// if the uncompressed size is known, it must be less
		// than 256 GiB.
		//
		// FIXME? Without picky we allow > LZMA_VLI_MAX which doesn't
		// really matter in this specific situation (> LZMA_VLI_MAX is
		// safe in the LZMA decoder) but it's somewhat weird still.
		if (coder->picky
				&& coder->uncompressed_size != LZMA_VLI_UNKNOWN
				&& coder->uncompressed_size
					>= (LZMA_VLI_C(1) << 38))
			return LZMA_FORMAT_ERROR;

		// Use LZMA_FILTER_LZMA1EXT features to specify the
		// uncompressed size and that the end marker is allowed
		// even when the uncompressed size is known. Both .lzma
		// header and LZMA1EXT use UINT64_MAX indicate that size
		// is unknown.
		coder->options.ext_flags = LZMA_LZMA1EXT_ALLOW_EOPM;
		lzma_set_ext_size(coder->options, coder->uncompressed_size);

		// Calculate the memory usage so that it is ready
		// for SEQ_CODER_INIT.
		coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
				+ LZMA_MEMUSAGE_BASE;

		coder->pos = 0;
		coder->sequence = SEQ_CODER_INIT;

	// Fall through

	case SEQ_CODER_INIT: {
		if (coder->memusage > coder->memlimit)
			return LZMA_MEMLIMIT_ERROR;

		lzma_filter_info filters[2] = {
			{
				.id = LZMA_FILTER_LZMA1EXT,
				.init = &lzma_lzma_decoder_init,
				.options = &coder->options,
			}, {
				.init = NULL,
			}
		};

		return_if_error(lzma_next_filter_init(&coder->next,
				allocator, filters));

		coder->sequence = SEQ_CODE;
		break;
	}

	case SEQ_CODE: {
		return coder->next.code(coder->next.coder,
				allocator, in, in_pos, in_size,
				out, out_pos, out_size, action);
	}

	default:
		return LZMA_PROG_ERROR;
	}

	return LZMA_OK;
}


static void
alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
	lzma_alone_coder *coder = coder_ptr;
	lzma_next_end(&coder->next, allocator);
	lzma_free(coder, allocator);
	return;
}


static lzma_ret
alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
		uint64_t *old_memlimit, uint64_t new_memlimit)
{
	lzma_alone_coder *coder = coder_ptr;

	*memusage = coder->memusage;
	*old_memlimit = coder->memlimit;

	if (new_memlimit != 0) {
		if (new_memlimit < coder->memusage)
			return LZMA_MEMLIMIT_ERROR;

		coder->memlimit = new_memlimit;
	}

	return LZMA_OK;
}


extern lzma_ret
lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
		uint64_t memlimit, bool picky)
{
	lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);

	lzma_alone_coder *coder = next->coder;

	if (coder == NULL) {
		coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
		if (coder == NULL)
			return LZMA_MEM_ERROR;

		next->coder = coder;
		next->code = &alone_decode;
		next->end = &alone_decoder_end;
		next->memconfig = &alone_decoder_memconfig;
		coder->next = LZMA_NEXT_CODER_INIT;
	}

	coder->sequence = SEQ_PROPERTIES;
	coder->picky = picky;
	coder->pos = 0;
	coder->options.dict_size = 0;
	coder->options.preset_dict = NULL;
	coder->options.preset_dict_size = 0;
	coder->uncompressed_size = 0;
	coder->memlimit = my_max(1, memlimit);
	coder->memusage = LZMA_MEMUSAGE_BASE;

	return LZMA_OK;
}


extern LZMA_API(lzma_ret)
lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
{
	lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);

	strm->internal->supported_actions[LZMA_RUN] = true;
	strm->internal->supported_actions[LZMA_FINISH] = true;

	return LZMA_OK;
}