1 files changed, 249 insertions, 0 deletions
diff --git a/src/liblzma/common/alone_decoder.c b/src/liblzma/common/alone_decoder.c
new file mode 100644
index 0000000..1dc85ba
--- /dev/null
+++ b/src/liblzma/common/alone_decoder.c
@@ -0,0 +1,249 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \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;
+}