source: zzuf/trunk/doc/zzuf.1 @ 1658

Last change on this file since 1658 was 1658, checked in by Sam Hocevar, 14 years ago
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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\-cdiMnqSx\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\-M\fR \fImegabytes\fR] [\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 [\fB\-\-\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 specifying 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\-M\fR, \fB\-\-max-memory\fR=\fImegabytes\fR
103Specify the maximum amount of memory, in megabytes, that children are allowed
104to allocate. This is useful to detect infinite loops that eat up a lot of
105memory. The value should set reasonably high so as not to interfer with normal
106program operation.
107
108\fBzzuf\fR uses the \fBsetrlimit\fR() call to set memory usage limitations and
109relies on the operating system's ability to enforce such limitations.
110.TP
111\fB\-n\fR, \fB\-\-network\fR
112Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
113.TP
114\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
115Protect a list of characters so that if they appear in input data that would
116normally be fuzzed, they are left unmodified instead.
117
118Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
119The sequences interpreted by \fBzzuf\fR are:
120.RS
121.TP
122\fB\\n\fR
123new line
124.TP
125\fB\\r\fR
126return
127.TP
128\fB\\t\fR
129tabulation
130.TP
131\fB\\\fR\fINNN\fR
132the byte whose octal value is \fINNN\fR
133.TP
134\fB\\x\fR\fINN\fR
135the byte whose hexadecimal value is \fINN\fR
136.TP
137\fB\\\\\fR
138backslash (\(oq\\\(cq)
139.RE
140.IP
141You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
142bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(dq\\001\-/\(dq\fR\(cq.
143
144The statistical outcome of this option should not be overlooked: if characters
145are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
146on the data being fuzzed. For instance, asking to fuzz 1% of input bits
147(\fB\-r\ 0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
148result in an actual average fuzzing ratio of 0.9% with truly random data,
1490.3% with random ASCII data and 0.2% with standard English text.
150
151See also the \fB\-R\fR flag.
152.TP
153\fB\-q\fR, \fB\-\-quiet\fR
154Hide the output of the fuzzed application. This is useful if the application
155is very verbose but only its exit code or signaled status is really useful to
156you.
157.TP
158\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
159Specify the proportion of bits that will be randomly fuzzed. A value of 0
160will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
161bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
162the input files undiscernible from random data. The default fuzzing ratio
163is 0.004 (fuzz 0.4% of the files' bits).
164.TP
165\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
166Refuse a list of characters by not fuzzing bytes that would otherwise be
167changed to a character that is in \fIlist\fR. If the original byte is already
168in \fIlist\fR, it is left unchanged.
169
170See the \fB\-P\fR option for a description of \fIlist\fR.
171.TP
172\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
173.PD 0
174.TP
175\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
176.PD
177Specify the random seed to use for fuzzing, or an interval of random seeds.
178Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
179the same way, even with a different target application. The purpose of this is
180to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
181causes the target application to crash.
182
183If an interval is specified, \fBzzuf\fR will run the application several times,
184each time with a different seed, and report the behaviour of each run.
185.TP
186\fB\-S\fR, \fB\-\-signal\fR
187Prevent children from installing signal handlers for signals that usually
188cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
189\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
190platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
191\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
192simply crash. If you do not want core dumps, you should set appropriate limits
193with the \fBlimit coredumpsize\fR command. See your shell's documentation on
194how to set such limits.
195.TP
196\fB\-T\fR, \fB\-\-max\-time\fR=\fIn\fR
197Automatically terminate child processes that run for more than \fIn\fR
198seconds. This is useful to detect infinite loops or processes stuck in other
199situations. See also the \fB\-B\fR flag.
200.TP
201\fB\-x\fR, \fB\-\-check\-exit\fR
202Report processes that exit with a non-zero status. By default only processes
203that crash due to a signal are reported.
204.TP
205\fB\-h\fR, \fB\-\-help\fR
206Display a short help message and exit.
207.TP
208\fB\-v\fR, \fB\-\-version\fR
209Output version information and exit.
210.SH EXAMPLES
211.PP
212Fuzz the input of the \fBcat\fR program using default settings:
213.PP
214\fB    zzuf cat /etc/motd\fR
215.PP
216Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
217.PP
218\fB    zzuf \-s 94324 \-r 0.01 cat /etc/motd\fR
219.PP
220Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
221and prevent non-ASCII characters from appearing in the output:
222.PP
223\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
224.PP
225Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
226original input and excluding \fB.xml\fR files from fuzzing (because
227\fBconvert\fR will also open its own XML configuration files and we do not
228want \fBzzuf\fR to fuzz them):
229.PP
230\fB    zzuf \-E \(aq\\.xml$\(aq convert \-\- foo.jpeg \-format tga /dev/null\fR
231.PP
232Fuzz the input of \fBVLC\fR, using file \fBmovie.avi\fR as the original input
233and restricting fuzzing to filenames that appear on the command line
234(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
235can be read by \fBVLC\fR to reproduce the same behaviour without using
236\fBzzuf\fR:
237.PP
238\fB    zzuf \-c \-s 87423 \-r 0.01 vlc movie.avi\fR
239\fB    zzuf \-c \-s 87423 \-r 0.01 <movie.avi >fuzzy\-movie.avi\fR
240\fB    vlc fuzzy\-movie.avi\fR
241.PP
242Fuzz 2% of \fBMPlayer\fR's input bits (\fB\-r\ 0.02\fR) with seeds 0 to 9999
243(\fB\-s\ 0:10000\fR), disabling its standard output messages (\fB\-q\fR),
244launching up to three simultaneous child processes (\fB\-F\ 3\fR), killing
245\fBMPlayer\fR if it takes more than one minute to read the file (\fB\-T\ 60\fR)
246and disabling its \fBSIGSEGV\fR signal handler (\fB\-S\fR):
247.PP
248\fB    zzuf \-c \-r 0.02 \-q \-s 0:10000 \-F 3 \-T 60 \-S \\\fR
249\fB      mplayer \-\- \-benchmark \-vo null \-fps 1000 movie.avi\fR
250.SH RESTRICTIONS
251.PP
252Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR,
253\fB_RLD_LIST\fB, \fBDYLD_INSERT_LIBRARIES\fR, etc.) to run its child
254processes, it will fail in the presence of any mechanism that disables
255preloading. For instance setuid root binaries will not be fuzzed when run
256as an unprivileged user.
257.PP
258For the same reasons, \fBzzuf\fR will also not work with statically linked
259binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
260where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
261.PP
262Though best efforts are made, identical behaviour for different versions of
263\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
264different operating systems and with different target programs is only
265guaranteed when the same version of \fBzzuf\fR is being used.
266.SH BUGS
267.PP
268\fBzzuf\fR probably does not behave correctly with 64-bit offsets.
269.PP
270It is not yet possible to insert or drop bytes from the input, to fuzz
271according to the file format, to swap bytes, etc. More advanced fuzzing
272methods are planned.
273.PP
274As of now, \fBzzuf\fR does not really support multithreaded applications. The
275behaviour with multithreaded applications where more than one thread does file
276descriptor operations is undefined.
277.SH NOTES
278In order to intercept file and network operations, signal handlers and memory
279allocations, \fBzzuf\fR diverts and reimplements the following functions,
280which can be private libc symbols, too:
281.TP
282Unix file descriptor handling:
283\fBopen\fR(), \fBlseek\fR(), \fBread\fR(), \fBaccept\fR(), \fBsocket\fR(),
284\fBclose\fR()
285.TP
286Standard IO streams:
287\fBfopen\fR(), \fBfreopen\fR(), \fBfseek\fR(), \fBfseeko\fR(), \fBrewind\fR(),
288\fBfread\fR(), \fBgetc\fR(), \fBfgetc\fR(), \fBfgets\fR(), \fBungetc\fR(),
289\fBfclose\fR()
290.TP
291Memory management:
292\fBmmap\fR(), \fBmunmap\fR(), \fBmalloc\fR(), \fBcalloc\fR(), \fBvalloc\fR(),
293\fBfree\fR(), \fBmemalign\fR(), \fBposix_memalign\fR()
294.TP
295Linux-specific:
296\fBopen64\fR(), \fBlseek64\fR(), \fBmmap64\fR(), \fB_IO_getc\fR(),
297\fBgetline\fR(), \fBgetdelim\fR(), \fB__getdelim\fR()
298.TP
299BSD-specific:
300\fBfgetln\fR(), \fB__srefill\fR()
301.TP
302Mac OS X-specific:
303\fBmap_fd\fR()
304.TP
305Signal handling:
306\fBsignal\fR(), \fBsigaction\fR()
307.PP
308If an application manipulates file descriptors (reading data, seeking around)
309using functions that are not in that list, \fBzzuf\fR will not fuzz its
310input consistently and the results should not be trusted. You can use a tool
311such as \fBltrace(1)\fR on Linux to know the missing functions.
312.PP
313On BSD systems, such as FreeBSD or Mac OS X, \fB__srefill\fR() is enough to
314monitor all standard IO streams functions. On other systems, such as Linux,
315each function is reimplemented on a case by case basis. One important
316unimplemented function is \fBfscanf\fR(), because of its complexity. Missing
317functions will be added upon user request.
318.SH HISTORY
319.PP
320\fBzzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
321multimedia stream corrupter used to find bugs in the \fBVLC\fR media player.
322.SH AUTHOR
323.PP
324Copyright \(co 2002, 2007 Sam Hocevar <sam@zoy.org>.
325.PP
326\fBzzuf\fR and this manual page are free software. They come without any
327warranty, to the extent permitted by applicable law. You can redistribute
328them and/or modify them under the terms of the Do What The Fuck You Want
329To Public License, Version 2, as published by Sam Hocevar. See
330\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
331.PP
332\fBzzuf\fR's webpage can be found at \fBhttp://sam.zoy.org/zzuf/\fR.
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