1// SPDX-License-Identifier: 0BSD
2
3///////////////////////////////////////////////////////////////////////////////
4//
5/// \file       alone_decoder.c
6/// \brief      Decoder for LZMA_Alone files
7//
8//  Author:     Lasse Collin
9//
10///////////////////////////////////////////////////////////////////////////////
11
12#include "alone_decoder.h"
13#include "lzma_decoder.h"
14#include "lz_decoder.h"
15
16
17typedef struct {
18	lzma_next_coder next;
19
20	enum {
21		SEQ_PROPERTIES,
22		SEQ_DICTIONARY_SIZE,
23		SEQ_UNCOMPRESSED_SIZE,
24		SEQ_CODER_INIT,
25		SEQ_CODE,
26	} sequence;
27
28	/// If true, reject files that are unlikely to be .lzma files.
29	/// If false, more non-.lzma files get accepted and will give
30	/// LZMA_DATA_ERROR either immediately or after a few output bytes.
31	bool picky;
32
33	/// Position in the header fields
34	size_t pos;
35
36	/// Uncompressed size decoded from the header
37	lzma_vli uncompressed_size;
38
39	/// Memory usage limit
40	uint64_t memlimit;
41
42	/// Amount of memory actually needed (only an estimate)
43	uint64_t memusage;
44
45	/// Options decoded from the header needed to initialize
46	/// the LZMA decoder
47	lzma_options_lzma options;
48} lzma_alone_coder;
49
50
51static lzma_ret
52alone_decode(void *coder_ptr, const lzma_allocator *allocator,
53		const uint8_t *restrict in, size_t *restrict in_pos,
54		size_t in_size, uint8_t *restrict out,
55		size_t *restrict out_pos, size_t out_size,
56		lzma_action action)
57{
58	lzma_alone_coder *coder = coder_ptr;
59
60	while (*out_pos < out_size
61			&& (coder->sequence == SEQ_CODE || *in_pos < in_size))
62	switch (coder->sequence) {
63	case SEQ_PROPERTIES:
64		if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
65			return LZMA_FORMAT_ERROR;
66
67		coder->sequence = SEQ_DICTIONARY_SIZE;
68		++*in_pos;
69		break;
70
71	case SEQ_DICTIONARY_SIZE:
72		coder->options.dict_size
73				|= (size_t)(in[*in_pos]) << (coder->pos * 8);
74
75		if (++coder->pos == 4) {
76			if (coder->picky && coder->options.dict_size
77					!= UINT32_MAX) {
78				// A hack to ditch tons of false positives:
79				// We allow only dictionary sizes that are
80				// 2^n or 2^n + 2^(n-1). LZMA_Alone created
81				// only files with 2^n, but accepts any
82				// dictionary size.
83				uint32_t d = coder->options.dict_size - 1;
84				d |= d >> 2;
85				d |= d >> 3;
86				d |= d >> 4;
87				d |= d >> 8;
88				d |= d >> 16;
89				++d;
90
91				if (d != coder->options.dict_size)
92					return LZMA_FORMAT_ERROR;
93			}
94
95			coder->pos = 0;
96			coder->sequence = SEQ_UNCOMPRESSED_SIZE;
97		}
98
99		++*in_pos;
100		break;
101
102	case SEQ_UNCOMPRESSED_SIZE:
103		coder->uncompressed_size
104				|= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
105		++*in_pos;
106		if (++coder->pos < 8)
107			break;
108
109		// Another hack to ditch false positives: Assume that
110		// if the uncompressed size is known, it must be less
111		// than 256 GiB.
112		//
113		// FIXME? Without picky we allow > LZMA_VLI_MAX which doesn't
114		// really matter in this specific situation (> LZMA_VLI_MAX is
115		// safe in the LZMA decoder) but it's somewhat weird still.
116		if (coder->picky
117				&& coder->uncompressed_size != LZMA_VLI_UNKNOWN
118				&& coder->uncompressed_size
119					>= (LZMA_VLI_C(1) << 38))
120			return LZMA_FORMAT_ERROR;
121
122		// Use LZMA_FILTER_LZMA1EXT features to specify the
123		// uncompressed size and that the end marker is allowed
124		// even when the uncompressed size is known. Both .lzma
125		// header and LZMA1EXT use UINT64_MAX indicate that size
126		// is unknown.
127		coder->options.ext_flags = LZMA_LZMA1EXT_ALLOW_EOPM;
128		lzma_set_ext_size(coder->options, coder->uncompressed_size);
129
130		// Calculate the memory usage so that it is ready
131		// for SEQ_CODER_INIT.
132		coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
133				+ LZMA_MEMUSAGE_BASE;
134
135		coder->pos = 0;
136		coder->sequence = SEQ_CODER_INIT;
137
138	// Fall through
139
140	case SEQ_CODER_INIT: {
141		if (coder->memusage > coder->memlimit)
142			return LZMA_MEMLIMIT_ERROR;
143
144		lzma_filter_info filters[2] = {
145			{
146				.id = LZMA_FILTER_LZMA1EXT,
147				.init = &lzma_lzma_decoder_init,
148				.options = &coder->options,
149			}, {
150				.init = NULL,
151			}
152		};
153
154		return_if_error(lzma_next_filter_init(&coder->next,
155				allocator, filters));
156
157		coder->sequence = SEQ_CODE;
158		break;
159	}
160
161	case SEQ_CODE: {
162		return coder->next.code(coder->next.coder,
163				allocator, in, in_pos, in_size,
164				out, out_pos, out_size, action);
165	}
166
167	default:
168		return LZMA_PROG_ERROR;
169	}
170
171	return LZMA_OK;
172}
173
174
175static void
176alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
177{
178	lzma_alone_coder *coder = coder_ptr;
179	lzma_next_end(&coder->next, allocator);
180	lzma_free(coder, allocator);
181	return;
182}
183
184
185static lzma_ret
186alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
187		uint64_t *old_memlimit, uint64_t new_memlimit)
188{
189	lzma_alone_coder *coder = coder_ptr;
190
191	*memusage = coder->memusage;
192	*old_memlimit = coder->memlimit;
193
194	if (new_memlimit != 0) {
195		if (new_memlimit < coder->memusage)
196			return LZMA_MEMLIMIT_ERROR;
197
198		coder->memlimit = new_memlimit;
199	}
200
201	return LZMA_OK;
202}
203
204
205extern lzma_ret
206lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
207		uint64_t memlimit, bool picky)
208{
209	lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
210
211	lzma_alone_coder *coder = next->coder;
212
213	if (coder == NULL) {
214		coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
215		if (coder == NULL)
216			return LZMA_MEM_ERROR;
217
218		next->coder = coder;
219		next->code = &alone_decode;
220		next->end = &alone_decoder_end;
221		next->memconfig = &alone_decoder_memconfig;
222		coder->next = LZMA_NEXT_CODER_INIT;
223	}
224
225	coder->sequence = SEQ_PROPERTIES;
226	coder->picky = picky;
227	coder->pos = 0;
228	coder->options.dict_size = 0;
229	coder->options.preset_dict = NULL;
230	coder->options.preset_dict_size = 0;
231	coder->uncompressed_size = 0;
232	coder->memlimit = my_max(1, memlimit);
233	coder->memusage = LZMA_MEMUSAGE_BASE;
234
235	return LZMA_OK;
236}
237
238
239extern LZMA_API(lzma_ret)
240lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
241{
242	lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);
243
244	strm->internal->supported_actions[LZMA_RUN] = true;
245	strm->internal->supported_actions[LZMA_FINISH] = true;
246
247	return LZMA_OK;
248}
249