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255 lines
10 KiB
Text
255 lines
10 KiB
Text
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.lzma Test Files
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----------------
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0. Introduction
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This directory contains bunch of files to test handling of .lzma files
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in .lzma decoder implementations. Many of the files have been created
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by hand with a hex editor, thus there is no better "source code" than
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the files themselves. All the test files (*.lzma) and this README have
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been put into the public domain.
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1. File Types
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Good files (good-*.lzma) must decode successfully without requiring
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a lot of CPU time or RAM. If the decoder supports only Single-Block
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Streams, then good-multi-*.lzma won't decode, of course.
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Bad files (bad-*.lzma) must cause the decoder to give an error. Like
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with the good files, these files must not require a lot of CPU time
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or RAM before they get detected to be broken.
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Malicious files (malicious-*.lzma) are good in terms of the file format
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specification, but try to trigger excessive CPU, RAM or disk usage in
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the decoder. To prevent malicious files from putting the decoder in
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inifinite loop (*), eating all available RAM or disk space, decoders
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should have internal limitters that catch these situations.
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(*) Strictly speaking not infinite, but if decoding of a small file
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would take a few weeks or even years, it's an infinite loop in
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practice.
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2. Descriptions of Individual Files
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2.1. Good Files
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good-single-none.lzma uses implicit Copy filter with known Uncompressed
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Size.
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good-single-none-pad.lzma is good-single-none.lzma with Footer Padding.
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good-cat-single-none-pad.lzma is two good-single-none-pad.lzma files
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concatenated as is. Fully decoding this file requires that the decoder
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supports decoding concatenated files.
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good-single-subblock_implicit.lzma uses implicit Subblock filter.
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good-single-lzma.lzma is LZMA compressed file with EOPM.
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good-single-subblock-lzma.lzma has basic combination of Subblock and
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LZMA filters.
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good-single-none-empty_1.lzma is an empty file with implicit Copy
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filter and no integrity Check.
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good-single-none-empty_2.lzma is an empty file with implicit Copy
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filter and CRC32 as Check.
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good-single-none-empty_3.lzma is an empty file with implicit Copy
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filter, known Compressed Size, and no integrity Check.
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good-single-lzma-empty.lzma is an empty file with LZMA filter and no
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integrity Check.
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good-single-subblock_rle.lzma takes advantage of Subblock filter's
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run-length encoding.
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good-single-delta-lzma.tiff.lzma is an image file that compresses
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better with Delta+LZMA than with plain LZMA.
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good-single-lzma-flush_1.lzma has a flush marker in the middle of
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the file, and no EOPM.
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good-single-lzma-flush_2.lzma has a flush marker in the middle of
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the file and just before EOPM.
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good-multi-none-1.lzma is a basic Multi-Block Stream with two Data
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Blocks and Footer Metadata Block.
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good-multi-none-2.lzma is good-multi-none-1.lzma with Total Size and
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Uncompressed Size added to the Footer Metadata Block.
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good-multi-none-extra_1.lzma has the `Extra is present' flag set but
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no actual Extra Records.
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good-multi-none-extra_2.lzma has two non-empty Extra Records.
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good-multi-none-extra_3.lzma has an Extra Record that has empty Data.
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good-multi-none-header_1.lzma has very minimal Header Metadata Block
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with only the Metadata Flags field.
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good-multi-none-header_2.lzma has all information in both Header and
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Footer Metadata Blocks. The Size of Header Metadata Block has wrong
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value in Header Metadata Block, but this value must be ignored by
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the decoder in case of Header Metadata Block.
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good-multi-none-header_3.lzma has Index only in the Header Metadata
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Block. Footer Metadata Block contains only Size of Header Metadata
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Block and Total Size.
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good-multi-none-block_1.lzma has Index in Header Metadata Block. The
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Compressed Size and Uncompressed Size fields are present in the Data
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Blocks. There is some Footer Padding between the Blocks.
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2.2. Bad Files
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bad-single-none-truncated.lzma is good-single-none.lzma without the
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last byte of the file.
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bad-cat-single-none-pad_garbage_1.lzma is good-cat-single-none-pad.lzma
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with 0xFE appended to the end of the file. 0xFE doesn't begin .lzma
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or LZMA_Alone format file.
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bad-cat-single-none-pad_garbage_2.lzma is good-cat-single-none-pad.lzma
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with 0xFF appended to the end of the file. 0xFF begins .lzma format
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file, thus the decoder has to detect that the file is incomplete.
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bad-cat-single-none-pad_garbage_3.lzma is good-cat-single-none-pad.lzma
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with 0x5D appended to the end of the file. 0x5D is the most common
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first byte of LZMA_Alone format file.
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bad-single-none-footer_filter_flags.lzma has different Stream Flags
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in Stream Footer than in Stream Header.
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bad-single-none-too_long_vli.lzma has 10-byte variable-length integer.
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bad-single-none-empty.lzma is like good-single-none-empty_3.lzma but
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with non-zero value in the Compressed Size field.
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bad-single-data_after_eopm_1.lzma has LZMA+Subblock, where the Subblock
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filter gives one byte of data to LZMA after LZMA has detected EOPM.
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bad-single-data_after_eopm_2.lzma is like
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bad-single-data_after_eopm_1.lzma but Subblock gives 256 MiB of data
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to LZMA after LZMA has detected EOPM.
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bad-single-subblock_subblock.lzma has Subblock+Subblock, where the
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Subblock decoder is given End of Input in the middle of a Subblock.
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bad-single-subblock-padding_loop.lzma contains huge amount of
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consecutive Padding bytes, which isn't allowed by the Subblock filter
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format. If it were allowed, this file would hang the decoder for very
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long time (weeks to years).
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bad-single-subblock1023-slow.lzma is similar to
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malicious-single-subblock31-slow.lzma except that this uses 1023 bytes
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of Padding in every place instead of 31 bytes. The Subblock filter
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format specification allows only 31-byte Padings, thus this file must
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get detected as bad without producing any output. Allowing larger
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Padding than 31 bytes was considered (so this test file was created),
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but it seemed to be a bad idea since it would increase worst-case CPU
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usage.
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bad-single-lzma-flush_beginning.lzma has flush marker in the beginning
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of the LZMA data.
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bad-single-lzma-flush_twice.lzma has two flush markers with no data
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between them.
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bad-multi-none-1.lzma has data after the last field in the Metadata
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Block and the `Extra is present' flag is not set.
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bad-multi-none-2.lzma has wrong Total Size in Footer Metadata Block.
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bad-multi-none-3.lzma has wrong Uncompressed Size in Footer Metadata
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Block.
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bad-multi-none-index_1.lzma has wrong value in the Number of Data
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Blocks field.
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bad-multi-none-index_2.lzma has too short Metadata to contain all
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the Index Records.
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bad-multi-none-index_3.lzma has wrong value in Total Size field in
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the Index.
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bad-multi-none-index_4.lzma has wrong value in Uncompressed Size field
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in the Index.
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bad-multi-none-extra_1.lzma has incomplete Extra Record at the end of
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the Metadata Block.
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bad-multi-none-extra_2.lzma has incomplete variable-length integer as
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Extra Record ID.
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bad-multi-none-extra_3.lzma has incomplete Extra Record at the end of
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the Metadata Block.
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bad-multi-none-header_1.lzma has empty Header Metadata Block (even
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the Metadata Flags field is not present).
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bad-multi-none-header_2.lzma has Index in the Header Metadata Block,
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which describes only one Data Block, while the Stream actually has
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two Data Blocks. A sophisticated decoder should give an error when
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it detects the second Data Block; all Multi-Block decoders must
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detect the file as corrupt at some point.
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bad-multi-none-header_3.lzma contains too small Total Size in Header
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Metadata Block. A sophisticated decoder should abort decoding before
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the second Data Block, preferably before the first Data Block has
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been finished; all Multi-Block decoders must detect the file as
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corrupt at some point.
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bad-multi-none-header_4.lzma is like bad-multi-none-header_3.lzma but
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with too small Uncompressed Size.
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bad-multi-none-header_5.lzma has Index in the Header Metadata Block,
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but the Total Size field is missing from the Footer Metadata Block.
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bad-multi-none-header_6.lzma has both Index and Total Size in Header
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Metadata Block, but Total Size doesn't match the Index. A sophisticated
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decoder should abort before decoding any Data Blocks; all Multi-Block
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decoders must detect the file as corrupt at some point.
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bad-multi-none-block_1.lzma has wrong Uncompressed Size in the first
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Data Block. A sophisticated decoder should detect this error before
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producing any output, because it can see that the Uncompressed Size
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doesn't match with the Index in Header Metadata Block; all Multi-Block
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decoders must detect the file as corrupt at some point.
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bad-multi-none-block_2.lzma has too big Compressed Size in the first
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Data Block. A sophisticated decoder may be able to detect the file as
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corrupt before producing any output, because Comrpessed Size + size
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of Block Header exceed the Total Size stored in Index in Header
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Metadata Block. A sophisticated decoder should be able to detect the
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error before the end of the first Data Block; all Multi-Block decoders
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must detect the file as corrupt at some point.
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2.3. Malicious Files
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malicious-single-subblock31-slow.lzma requires quite a bit of CPU time
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per decoded byte. It contains LZMA compressed Subblock filter data that
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has as much Padding as the specification allows. LZMA is also used as
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a Subfilter, to further slowdown the decoder. Every Subfilter instance
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produces only one byte of output. If you can create a file that wastes
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notably more CPU cycles than this file, please contact Lasse Collin.
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malicious-single-subblock-256MiB.lzma is a tiny file that produces
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256 MiB of output. It uses Subblock filter's run-length encoding
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to achieve this.
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malicious-single-subblock-64PiB.lzma is a tiny file that produces
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64 PiB of output (if you have patience to wait). This is done by
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chaining two Subblock filters and using their run-length encoders.
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malicious-multi-metadata-64PiB.lzma is like
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malicious-single-subblock-64PiB.lzma but the huge amount of output
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is in a Metadata Block. Trying to decode this file may take years
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unless the decoder catches that the Metadata has unreasonable size.
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