7 This directory contains bunch of files to test handling of .lzma files
8 in .lzma decoder implementations. Many of the files have been created
9 by hand with a hex editor, thus there is no better "source code" than
10 the files themselves. All the test files (*.lzma) and this README have
11 been put into the public domain.
16 Good files (good-*.lzma) must decode successfully without requiring
17 a lot of CPU time or RAM. If the decoder supports only Single-Block
18 Streams, then good-multi-*.lzma won't decode, of course.
20 Bad files (bad-*.lzma) must cause the decoder to give an error. Like
21 with the good files, these files must not require a lot of CPU time
22 or RAM before they get detected to be broken.
24 Malicious files (malicious-*.lzma) are good in terms of the file format
25 specification, but try to trigger excessive CPU, RAM or disk usage in
26 the decoder. To prevent malicious files from putting the decoder in
27 inifinite loop (*), eating all available RAM or disk space, decoders
28 should have internal limitters that catch these situations.
30 (*) Strictly speaking not infinite, but if decoding of a small file
31 would take a few weeks or even years, it's an infinite loop in
35 2. Descriptions of Individual Files
39 good-single-none.lzma uses implicit Copy filter with known Uncompressed
42 good-single-none-pad.lzma is good-single-none.lzma with Footer Padding.
44 good-cat-single-none-pad.lzma is two good-single-none-pad.lzma files
45 concatenated as is. Fully decoding this file requires that the decoder
46 supports decoding concatenated files.
48 good-single-subblock_implicit.lzma uses implicit Subblock filter.
50 good-single-lzma.lzma is LZMA compressed file with EOPM.
52 good-single-subblock-lzma.lzma has basic combination of Subblock and
55 good-single-subblock_rle.lzma takes advantage of Subblock filter's
58 good-single-delta-lzma.tiff.lzma is an image file that compresses
59 better with Delta+LZMA than with plain LZMA.
64 bad-single-none-truncated.lzma is good-single-none.lzma without the
65 last byte of the file.
67 bad-cat-single-none-pad_garbage_1.lzma is good-cat-single-none-pad.lzma
68 with 0xFE appended to the end of the file. 0xFE doesn't begin .lzma
69 or LZMA_Alone format file.
71 bad-cat-single-none-pad_garbage_2.lzma is good-cat-single-none-pad.lzma
72 with 0xFF appended to the end of the file. 0xFF begins .lzma format
73 file, thus the decoder has to detect that the file is incomplete.
75 bad-cat-single-none-pad_garbage_3.lzma is good-cat-single-none-pad.lzma
76 with 0x5D appended to the end of the file. 0x5D is the most common
77 first byte of LZMA_Alone format file.
79 bad-single-data_after_eopm_1.lzma has LZMA+Subblock, where the Subblock
80 filter gives one byte of data to LZMA after LZMA has detected EOPM.
82 bad-single-data_after_eopm_2.lzma is like
83 bad-single-data_after_eopm_1.lzma but Subblock gives 256 MiB of data
84 to LZMA after LZMA has detected EOPM.
86 bad-single-subblock_subblock.lzma has Subblock+Subblock, where the
87 Subblock decoder is given End of Input in the middle of a Subblock.
89 bad-single-subblock-padding_loop.lzma contains huge amount of
90 consecutive Padding bytes, which isn't allowed by the Subblock filter
91 format. If it were allowed, this file would hang the decoder for very
92 long time (weeks to years).
94 bad-single-subblock1023-slow.lzma is similar to
95 malicious-single-subblock31-slow.lzma except that this uses 1023 bytes
96 of Padding in every place instead of 31 bytes. The Subblock filter
97 format specification allows only 31-byte Padings, thus this file must
98 get detected as bad without producing any output. Allowing larger
99 Padding than 31 bytes was considered (so this test file was created),
100 but it seemed to be a bad idea since it would increase worst-case CPU
106 malicious-single-subblock31-slow.lzma requires quite a bit of CPU time
107 per decoded byte. It contains LZMA compressed Subblock filter data that
108 has as much Padding as the specification allows. LZMA is also used as
109 a Subfilter, to further slowdown the decoder. Every Subfilter instance
110 produces only one byte of output. If you can create a file that wastes
111 notably more CPU cycles than this file, please contact Lasse Collin.
113 malicious-single-subblock-256MiB.lzma is a tiny file that produces
114 256 MiB of output. It uses Subblock filter's run-length encoding
117 malicious-single-subblock-64PiB.lzma is a tiny file that produces
118 64 PiB of output (if you have patience to wait). This is done by
119 chaining two Subblock filters and using their run-length encoders.
121 malicious-multi-metadata-64PiB.lzma is like
122 malicious-single-subblock-64PiB.lzma but the huge amount of output
123 is in a Metadata Block. Trying to decode this file may take years
124 unless the decoder catches that the Metadata has unreasonable size.