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-lzma.lzma is LZMA compressed file with EOPM.
50 good-single-subblock-lzma.lzma has basic combination of Subblock and
53 good-single-subblock_rle.lzma takes advantage of Subblock filter's
56 good-single-delta-lzma.tiff.lzma is an image file that compresses
57 better with Delta+LZMA than with plain LZMA.
62 bad-single-none-truncated.lzma is good-single-none.lzma without the
63 last byte of the file.
65 bad-cat-single-none-pad_garbage_1.lzma is good-cat-single-none-pad.lzma
66 with 0xFE appended to the end of the file. 0xFE doesn't begin .lzma
67 or LZMA_Alone format file.
69 bad-cat-single-none-pad_garbage_2.lzma is good-cat-single-none-pad.lzma
70 with 0xFF appended to the end of the file. 0xFF begins .lzma format
71 file, thus the decoder has to detect that the file is incomplete.
73 bad-cat-single-none-pad_garbage_3.lzma is good-cat-single-none-pad.lzma
74 with 0x5D appended to the end of the file. 0x5D is the most common
75 first byte of LZMA_Alone format file.
77 bad-single-data_after_eopm_1.lzma has LZMA+Subblock, where the Subblock
78 filter gives one byte of data to LZMA after LZMA has detected EOPM.
80 bad-single-data_after_eopm_2.lzma is like
81 bad-single-data_after_eopm_1.lzma but Subblock gives 256 MiB of data
82 to LZMA after LZMA has detected EOPM.
84 bad-single-subblock_subblock.lzma has Subblock+Subblock, where the
85 Subblock decoder is given End of Input in the middle of a Subblock.
87 bad-single-subblock-padding_loop.lzma contains huge amount of
88 consecutive Padding bytes, which isn't allowed by the Subblock filter
89 format. If it were allowed, this file would hang the decoder for very
90 long time (weeks to years).
92 bad-single-subblock1023-slow.lzma is similar to
93 malicious-single-subblock31-slow.lzma except that this uses 1023 bytes
94 of Padding in every place instead of 31 bytes. The Subblock filter
95 format specification allows only 31-byte Padings, thus this file must
96 get detected as bad without producing any output. Allowing larger
97 Padding than 31 bytes was considered (so this test file was created),
98 but it seemed to be a bad idea since it would increase worst-case CPU
104 malicious-single-subblock31-slow.lzma requires quite a bit of CPU time
105 per decoded byte. It contains LZMA compressed Subblock filter data that
106 has as much Padding as the specification allows. LZMA is also used as
107 a Subfilter, to further slowdown the decoder. Every Subfilter instance
108 produces only one byte of output. If you can create a file that wastes
109 notably more CPU cycles than this file, please contact Lasse Collin.
111 malicious-single-subblock-256MiB.lzma is a tiny file that produces
112 256 MiB of output. It uses Subblock filter's run-length encoding
115 malicious-single-subblock-64PiB.lzma is a tiny file that produces
116 64 PiB of output (if you have patience to wait). This is done by
117 chaining two Subblock filters and using their run-length encoders.
119 malicious-multi-metadata-64PiB.lzma is like
120 malicious-single-subblock-64PiB.lzma but the huge amount of output
121 is in a Metadata Block. Trying to decode this file may take years
122 unless the decoder catches that the Metadata has unreasonable size.