source: zzuf/trunk/doc/zzuf.1 @ 1640

Last change on this file since 1640 was 1640, checked in by Sam Hocevar, 14 years ago
  • Changed -M to -m (for --md5).
File size: 12.7 KB
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1.TH zzuf 1 "2006-12-22" "zzuf"
2.SH NAME
3zzuf \- multiple purpose fuzzer
4.SH SYNOPSIS
5\fBzzuf\fR [\fB\-cdiMnqS\fR] [\fB\-r\fR \fIratio\fR] [\fB\-s\fR \fIseed\fR | \fB\-s\fR \fIstart:stop\fR]
6.br
7                [\fB\-F\fR \fIforks\fR] [\fB\-C\fR \fIcrashes\fR] [\fB\-B\fR \fIbytes\fR] [\fB\-T\fR \fIseconds\fR]
8.br
9                [\fB\-P\fR \fIprotect\fR] [\fB\-R\fR \fIrefuse\fR]
10.br
11                [\fB\-I\fR \fIinclude\fR] [\fB\-E\fR \fIexclude\fR] [\fIPROGRAM\fR [\fIARGS\fR]...]
12.br
13\fBzzuf \-h\fR | \fB\-\-help\fR
14.br
15\fBzzuf \-v\fR | \fB\-\-version\fR
16.SH DESCRIPTION
17.PP
18\fBZzuf\fR is a transparent application input fuzzer. It works by intercepting
19file and network operations and changing random bits in the program's input.
20\fBZzuf\fR's behaviour is deterministic, making it easy to reproduce bugs.
21.SH USAGE
22.PP
23\fBZzuf\fR will run an application specified on its command line, one or
24several times, with optional arguments, and will report the application's
25relevant behaviour on the standard output, eg:
26.PP
27\fB    zzuf cat /dev/zero\fR
28.PP
29If you want to specify flags for your application, put a \(oq\fB\-\-\fR\(cq
30marker before them on the command line (otherwise \fBzzuf\fR will try to
31interpret them as arguments for itself), eg:
32.PP
33\fB    zzuf \-B 1000 cat \-\- \-v /dev/zero\fR
34.PP
35When no program is specified, \fBzzuf\fR simply fuzzes the standard input, as
36if the \fBcat\fR utility had been called:
37.PP
38\fB    zzuf < /dev/zero\fR
39.SH OPTIONS
40.TP
41\fB\-B\fR, \fB\-\-max\-bytes\fR=\fIn\fR
42Automatically terminate child processes that output more than \fIn\fR bytes
43on the standard output and standard error channels. This is useful to detect
44infinite loops. See also the \fB\-T\fR flag.
45.TP
46\fB\-c\fR, \fB\-\-cmdline\fR
47Only fuzz files whose name is specified in the target application's command
48line. This is mostly a shortcut to avoid specifiying twice the argument:
49
50\fB    zzuf \-c cat file.txt\fR
51
52has the same effect as
53
54\fB    zzuf \-I \(aq^file\\.txt$\(aq cat file.txt\fR
55
56See the \fB\-I\fR flag for more information on restricting fuzzing to
57specific files.
58.TP
59\fB\-C\fR, \fB\-\-max\-crashes\fR=\fIn\fR
60Stop forking when at least \fIn\fR children have crashed. The default value
61is 1, meaning \fBzzuf\fR will stop as soon as one child has crashed. A process
62is considered to have crashed if any signal (such as, but not limited to,
63\fBSIGSEGV\fR) caused it to exit. If the \fB\-x\fR flag is used, this will
64also include processes that exit with a non-zero status.
65
66This option is only relevant if the \fB\-s\fR flag is used with an interval
67argument.
68.TP
69\fB\-d\fR, \fB\-\-debug\fR
70Activate the display of debug messages.
71.TP
72\fB\-E\fR, \fB\-\-exclude\fR=\fIregex\fR
73Do not fuzz files whose name matches the \fIregex\fR regular expression. This
74option supersedes anything that is specified by the \fB\-I\fR flag. Use this
75for instance if you are unsure of what files your application is going to read
76and do not want it to fuzz files in the \fB/etc\fR directory.
77
78Multiple \fB\-E\fR flags can be specified, in which case files matching any one
79of the regular expressions will be ignored.
80.TP
81\fB\-F\fR, \fB\-\-max\-forks\fR=\fIforks\fR
82Specify the number of simultaneous children that can be run.
83
84This option is only relevant if the \fB\-s\fR flag is used with an interval
85argument.
86.TP
87\fB\-i\fR, \fB\-\-stdin\fR
88Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
89.TP
90\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
91Only fuzz files whose name matches the \fIregex\fR regular expression. Use
92this for instance if your application reads configuration files at startup
93and you only want specific files to be fuzzed.
94
95Multiple \fB\-I\fR flags can be specified, in which case files matching any one
96of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
97.TP
98\fB\-m\fR, \fB\-\-md5\fR
99Instead of displaying the program's standard output, just print the MD5 digest
100of that output. The standard error channel is left untouched.
101.TP
102\fB\-n\fR, \fB\-\-network\fR
103Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
104.TP
105\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
106Protect a list of characters so that if they appear in input data that would
107normally be fuzzed, they are left unmodified instead.
108
109Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
110The sequences interpreted by \fBzzuf\fR are:
111.RS
112.TP
113\fB\\n\fR
114new line
115.TP
116\fB\\r\fR
117return
118.TP
119\fB\\t\fR
120tabulation
121.TP
122\fB\\\fR\fINNN\fR
123the byte whose octal value is \fINNN\fR
124.TP
125\fB\\x\fR\fINN\fR
126the byte whose hexadecimal value is \fINN\fR
127.TP
128\fB\\\\\fR
129backslash (\(oq\\\(cq)
130.RE
131.IP
132You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
133bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(dq\\001\-/\(dq\fR\(cq.
134
135The statistical outcome of this option should not be overlooked: if characters
136are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
137on the data being fuzzed. For instance, asking to fuzz 1% of input bits
138(\fB\-r\ 0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
139result in an actual average fuzzing ratio of 0.9% with truly random data,
1400.3% with random ASCII data and 0.2% with standard English text.
141
142See also the \fB\-R\fR flag.
143.TP
144\fB\-q\fR, \fB\-\-quiet\fR
145Hide the output of the fuzzed application. This is useful if the application
146is very verbose but only its exit code or signaled status is really useful to
147you.
148.TP
149\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
150Specify the proportion of bits that will be randomly fuzzed. A value of 0
151will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
152bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
153the input files undiscernible from random data. The default fuzzing ratio
154is 0.004 (fuzz 0.4% of the files' bits).
155.TP
156\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
157Refuse a list of characters by not fuzzing bytes that would otherwise be
158changed to a character that is in \fIlist\fR. If the original byte is already
159in \fIlist\fR, it is left unchanged.
160
161See the \fB\-P\fR option for a description of \fIlist\fR.
162.TP
163\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
164.PD 0
165.TP
166\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
167.PD
168Specify the random seed to use for fuzzing, or an interval of random seeds.
169Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
170the same way, even with a different target application. The purpose of this is
171to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
172causes the target application to crash.
173
174If an interval is specified, \fBzzuf\fR will run the application several times,
175each time with a different seed, and report the behaviour of each run.
176.TP
177\fB\-S\fR, \fB\-\-signal\fR
178Prevent children from installing signal handlers for signals that usually
179cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
180\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
181platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
182\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
183simply crash. If you do not want core dumps, you should set appropriate limits
184with the \fBlimit coredumpsize\fR command. See your shell's documentation on
185how to set such limits.
186.TP
187\fB\-T\fR, \fB\-\-max\-time\fR=\fIn\fR
188Automatically terminate child processes that run for more than \fIn\fR
189seconds. This is useful to detect infinite loops or processes stuck in other
190situations. See also the \fB\-B\fR flag.
191.TP
192\fB\-x\fR, \fB\-\-check\-exit\fR
193Report processes that exit with a non-zero status. By default only processes
194that crash due to a signal are reported.
195.TP
196\fB\-h\fR, \fB\-\-help\fR
197Display a short help message and exit.
198.TP
199\fB\-v\fR, \fB\-\-version\fR
200Output version information and exit.
201.SH EXAMPLES
202.PP
203Fuzz the input of the \fBcat\fR program using default settings:
204.PP
205\fB    zzuf cat /etc/motd\fR
206.PP
207Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
208.PP
209\fB    zzuf \-s 94324 \-r 0.01 cat /etc/motd\fR
210.PP
211Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
212and prevent non-ASCII characters from appearing in the output:
213.PP
214\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
215.PP
216Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
217original input and excluding \fB.xml\fR files from fuzzing (because
218\fBconvert\fR will also open its own XML configuration files and we do not
219want \fBzzuf\fR to fuzz them):
220.PP
221\fB    zzuf \-E \(aq\\.xml$\(aq convert \-\- foo.jpeg \-format tga /dev/null\fR
222.PP
223Fuzz the input of \fBVLC\fR, using file \fBmovie.avi\fR as the original input
224and restricting fuzzing to filenames that appear on the command line
225(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
226can be read by \fBVLC\fR to reproduce the same behaviour without using
227\fBzzuf\fR:
228.PP
229\fB    zzuf \-c \-s 87423 \-r 0.01 vlc movie.avi\fR
230\fB    zzuf \-c \-s 87423 \-r 0.01 cp movie.avi fuzzy\-movie.avi\fR
231\fB    vlc fuzzy\-movie.avi\fR
232.PP
233Fuzz 2% of \fBMPlayer\fR's input bits (\fB\-r\ 0.02\fR) with seeds 0 to 9999
234(\fB\-s\ 0:10000\fR), disabling its standard output messages (\fB\-q\fR),
235launching up to three simultaneous child processes (\fB\-F\ 3\fR), killing
236\fBMPlayer\fR if it takes more than one minute to read the file (\fB\-T\ 60\fR)
237and disabling its \fBSIGSEGV\fR signal handler (\fB\-S\fR):
238.PP
239\fB    zzuf \-c \-r 0.02 \-q \-s 0:10000 \-F 3 \-T 60 \-S \\\fR
240\fB      mplayer \-\- \-benchmark \-vo null \-fps 1000 movie.avi\fR
241.SH RESTRICTIONS
242.PP
243Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR on most
244Unix systems, \fBDYLD_INSERT_LIBRARIES\fR on Mac OS X) to run its child
245processes, it will fail in the presence of any mechanism that disables
246preloading. For instance setuid root binaries will not be fuzzed when run
247as an unprivileged user.
248.PP
249For the same reasons, \fBzzuf\fR will also not work with statically linked
250binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
251where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
252.PP
253Though best efforts are made, identical behaviour for different versions of
254\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
255different operating systems and with different target programs is only
256guaranteed when the same version of \fBzzuf\fR is being used.
257.SH BUGS
258.PP
259\fBZzuf\fR probably does not behave correctly with 64-bit offsets.
260.PP
261It is not yet possible to insert or drop bytes from the input, to fuzz
262according to the file format, to swap bytes, etc. More advanced fuzzing
263methods are planned.
264.PP
265As of now, \fBzzuf\fR does not really support multithreaded applications. The
266behaviour with multithreaded applications where more than one thread does file
267descriptor operations is undefined.
268.SH NOTES
269In order to intercept file and network operations and signal handlers,
270\fBzzuf\fR diverts and reimplements the following functions, which can
271be private libc symbols, too:
272.TP
273Unix file descriptor handling:
274\fBopen\fR(), \fBlseek\fR(), \fBread\fR(), \fBaccept\fR(), \fBsocket\fR(),
275\fBmmap\fR(), \fBmunmap\fR(), \fBclose\fR()
276.TP
277Standard IO streams:
278\fBfopen\fR(), \fBfreopen\fR(), \fBfseek\fR(), \fBfseeko\fR(), \fBrewind\fR(),
279\fBfread\fR(), \fBgetc\fR(), \fBfgetc\fR(), \fBfgets\fR(), \fBungetc\fR(),
280\fBfclose\fR()
281.TP
282Linux-specific:
283\fBopen64\fR(), \fBlseek64\fR(), \fBmmap64\fR(), \fB_IO_getc\fR(),
284\fBgetline\fR(), \fBgetdelim\fR(), \fB__getdelim\fR()
285.TP
286BSD-specific:
287\fBfgetln\fR(), \fB__srefill\fR()
288.TP
289Mac OS X-specific:
290\fBmap_fd\fR()
291.TP
292Signal handling:
293\fBsignal\fR(), \fBsigaction\fR()
294.PP
295If an application manipulates file descriptors (reading data, seeking around)
296using functions that are not in that list, \fBzzuf\fR will not fuzz its
297input consistently and the results should not be trusted. You can use a tool
298such as \fBltrace(1)\fR on Linux to know the missing functions.
299.PP
300On BSD systems, such as FreeBSD or Mac OS X, \fB__srefill\fR() is enough to
301monitor all standard IO streams functions. On other systems, such as Linux,
302each function is reimplemented on a case by case basis. One important
303unimplemented function is \fBfscanf\fR(), because of its complexity. Missing
304functions will be added upon user request.
305.SH HISTORY
306.PP
307\fBZzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
308multimedia stream corrupter used to find bugs in the \fBVLC\fR media player.
309.SH AUTHOR
310.PP
311Copyright \(co 2002, 2007 Sam Hocevar <sam@zoy.org>.
312.PP
313\fBZzuf\fR and this manual page are free software. They come without any
314warranty, to the extent permitted by applicable law. You can redistribute
315them and/or modify them under the terms of the Do What The Fuck You Want
316To Public License, Version 2, as published by Sam Hocevar. See
317\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
318.PP
319\fBZzuf\fR's webpage can be found at \fBhttp://sam.zoy.org/zzuf/\fR.
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