source: zzuf/trunk/doc/zzuf.1 @ 1631

Last change on this file since 1631 was 1631, checked in by Sam Hocevar, 14 years ago
  • Implement map_fd for OS X.
File size: 12.5 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.
64
65This option is only relevant if the \fB\-s\fR flag is used with an interval
66argument.
67.TP
68\fB\-d\fR, \fB\-\-debug\fR
69Activate the display of debug messages.
70.TP
71\fB\-E\fR, \fB\-\-exclude\fR=\fIregex\fR
72Do not fuzz files whose name matches the \fIregex\fR regular expression. This
73option supersedes anything that is specified by the \fB\-I\fR flag. Use this
74for instance if you are unsure of what files your application is going to read
75and do not want it to fuzz files in the \fB/etc\fR directory.
76
77Multiple \fB\-E\fR flags can be specified, in which case files matching any one
78of the regular expressions will be ignored.
79.TP
80\fB\-F\fR, \fB\-\-max\-forks\fR=\fIforks\fR
81Specify the number of simultaneous children that can be run.
82
83This option is only relevant if the \fB\-s\fR flag is used with an interval
84argument.
85.TP
86\fB\-i\fR, \fB\-\-stdin\fR
87Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
88.TP
89\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
90Only fuzz files whose name matches the \fIregex\fR regular expression. Use
91this for instance if your application reads configuration files at startup
92and you only want specific files to be fuzzed.
93
94Multiple \fB\-I\fR flags can be specified, in which case files matching any one
95of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
96.TP
97\fB\-M\fR, \fB\-\-md5\fR
98Instead of displaying the program's standard output, just print the MD5 digest
99of that output. The standard error channel is left untouched.
100.TP
101\fB\-n\fR, \fB\-\-network\fR
102Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
103.TP
104\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
105Protect a list of characters so that if they appear in input data that would
106normally be fuzzed, they are left unmodified instead.
107
108Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
109The sequences interpreted by \fBzzuf\fR are:
110.RS
111.TP
112\fB\\n\fR
113new line
114.TP
115\fB\\r\fR
116return
117.TP
118\fB\\t\fR
119tabulation
120.TP
121\fB\\\fR\fINNN\fR
122the byte whose octal value is \fINNN\fR
123.TP
124\fB\\x\fR\fINN\fR
125the byte whose hexadecimal value is \fINN\fR
126.TP
127\fB\\\\\fR
128backslash (\(oq\\\(cq)
129.RE
130.IP
131You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
132bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(dq\\001\-/\(dq\fR\(cq.
133
134The statistical outcome of this option should not be overlooked: if characters
135are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
136on the data being fuzzed. For instance, asking to fuzz 1% of input bits
137(\fB\-r\ 0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
138result in an actual average fuzzing ratio of 0.9% with truly random data,
1390.3% with random ASCII data and 0.2% with standard English text.
140
141See also the \fB\-R\fR flag.
142.TP
143\fB\-q\fR, \fB\-\-quiet\fR
144Hide the output of the fuzzed application. This is useful if the application
145is very verbose but only its exit code or signaled status is really useful to
146you.
147.TP
148\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
149Specify the proportion of bits that will be randomly fuzzed. A value of 0
150will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
151bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
152the input files undiscernible from random data. The default fuzzing ratio
153is 0.004 (fuzz 0.4% of the files' bits).
154.TP
155\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
156Refuse a list of characters by not fuzzing bytes that would otherwise be
157changed to a character that is in \fIlist\fR. If the original byte is already
158in \fIlist\fR, it is left unchanged.
159
160See the \fB\-P\fR option for a description of \fIlist\fR.
161.TP
162\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
163.PD 0
164.TP
165\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
166.PD
167Specify the random seed to use for fuzzing, or an interval of random seeds.
168Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
169the same way, even with a different target application. The purpose of this is
170to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
171causes the target application to crash.
172
173If an interval is specified, \fBzzuf\fR will run the application several times,
174each time with a different seed, and report the behaviour of each run.
175.TP
176\fB\-S\fR, \fB\-\-signal\fR
177Prevent children from installing signal handlers for signals that usually
178cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
179\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
180platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
181\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
182simply crash. If you do not want core dumps, you should set appropriate limits
183with the \fBlimit coredumpsize\fR command. See your shell's documentation on
184how to set such limits.
185.TP
186\fB\-T\fR, \fB\-\-max\-time\fR=\fIn\fR
187Automatically terminate child processes that run for more than \fIn\fR
188seconds. This is useful to detect infinite loops or processes stuck in other
189situations. See also the \fB\-B\fR flag.
190.TP
191\fB\-h\fR, \fB\-\-help\fR
192Display a short help message and exit.
193.TP
194\fB\-v\fR, \fB\-\-version\fR
195Output version information and exit.
196.SH EXAMPLES
197.PP
198Fuzz the input of the \fBcat\fR program using default settings:
199.PP
200\fB    zzuf cat /etc/motd\fR
201.PP
202Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
203.PP
204\fB    zzuf \-s 94324 \-r 0.01 cat /etc/motd\fR
205.PP
206Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
207and prevent non-ASCII characters from appearing in the output:
208.PP
209\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
210.PP
211Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
212original input and excluding \fB.xml\fR files from fuzzing (because
213\fBconvert\fR will also open its own XML configuration files and we do not
214want \fBzzuf\fR to fuzz them):
215.PP
216\fB    zzuf \-E \(aq\\.xml$\(aq convert \-\- foo.jpeg \-format tga /dev/null\fR
217.PP
218Fuzz the input of \fBVLC\fR, using file \fBmovie.avi\fR as the original input
219and restricting fuzzing to filenames that appear on the command line
220(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
221can be read by \fBVLC\fR to reproduce the same behaviour without using
222\fBzzuf\fR:
223.PP
224\fB    zzuf \-c \-s 87423 \-r 0.01 vlc movie.avi\fR
225\fB    zzuf \-c \-s 87423 \-r 0.01 cp movie.avi fuzzy\-movie.avi\fR
226\fB    vlc fuzzy\-movie.avi\fR
227.PP
228Fuzz 2% of \fBMPlayer\fR's input bits (\fB\-r\ 0.02\fR) with seeds 0 to 9999
229(\fB\-s\ 0:10000\fR), disabling its standard output messages (\fB\-q\fR),
230launching up to three simultaneous child processes (\fB\-F\ 3\fR), killing
231\fBMPlayer\fR if it takes more than one minute to read the file (\fB\-T\ 60\fR)
232and disabling its \fBSIGSEGV\fR signal handler (\fB\-S\fR):
233.PP
234\fB    zzuf \-c \-r 0.02 \-q \-s 0:10000 \-F 3 \-T 60 \-S \\\fR
235\fB      mplayer \-\- \-benchmark \-vo null \-fps 1000 movie.avi\fR
236.SH RESTRICTIONS
237.PP
238Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR on most
239Unix systems, \fBDYLD_INSERT_LIBRARIES\fR on Mac OS X) to run its child
240processes, it will fail in the presence of any mechanism that disables
241preloading. For instance setuid root binaries will not be fuzzed when run
242as an unprivileged user.
243.PP
244For the same reasons, \fBzzuf\fR will also not work with statically linked
245binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
246where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
247.PP
248Though best efforts are made, identical behaviour for different versions of
249\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
250different operating systems and with different target programs is only
251guaranteed when the same version of \fBzzuf\fR is being used.
252.SH BUGS
253.PP
254\fBZzuf\fR probably does not behave correctly with 64-bit offsets.
255.PP
256It is not yet possible to insert or drop bytes from the input, to fuzz
257according to the file format, to swap bytes, etc. More advanced fuzzing
258methods are planned.
259.PP
260As of now, \fBzzuf\fR does not really support multithreaded applications. The
261behaviour with multithreaded applications where more than one thread does file
262descriptor operations is undefined.
263.SH NOTES
264In order to intercept file and network operations and signal handlers,
265\fBzzuf\fR diverts and reimplements the following functions, which can
266be private libc symbols, too:
267.TP
268Unix file descriptor handling:
269\fBopen\fR(), \fBlseek\fR(), \fBread\fR(), \fBaccept\fR(), \fBsocket\fR(),
270\fBmmap\fR(), \fBmunmap\fR(), \fBclose\fR()
271.TP
272Standard IO streams:
273\fBfopen\fR(), \fBfreopen\fR(), \fBfseek\fR(), \fBfseeko\fR(), \fBrewind\fR(),
274\fBfread\fR(), \fBgetc\fR(), \fBfgetc\fR(), \fBfgets\fR(), \fBungetc\fR(),
275\fBfclose\fR()
276.TP
277Linux-specific:
278\fBopen64\fR(), \fBlseek64\fR(), \fBmmap64\fR(), \fB_IO_getc\fR(),
279\fBgetline\fR(), \fBgetdelim\fR(), \fB__getdelim\fR()
280.TP
281BSD-specific:
282\fBfgetln\fR(), \fB__srefill\fR()
283.TP
284Mac OS X-specific:
285\fBmap_fd\fR()
286.TP
287Signal handling:
288\fBsignal\fR(), \fBsigaction\fR()
289.PP
290If an application manipulates file descriptors (reading data, seeking around)
291using functions that are not in that list, \fBzzuf\fR will not fuzz its
292input consistently and the results should not be trusted. You can use a tool
293such as \fBltrace(1)\fR on Linux to know the missing functions.
294.PP
295On BSD systems, such as FreeBSD or Mac OS X, \fB__srefill\fR() is enough to
296monitor all standard IO streams functions. On other systems, such as Linux,
297each function is reimplemented on a case by case basis. One important
298unimplemented function is \fBfscanf\fR(), because of its complexity. Missing
299functions will be added upon user request.
300.SH HISTORY
301.PP
302\fBZzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
303multimedia stream corrupter used to find bugs in the \fBVLC\fR media player.
304.SH AUTHOR
305.PP
306Copyright \(co 2002, 2007 Sam Hocevar <sam@zoy.org>.
307.PP
308\fBZzuf\fR and this manual page are free software. They come without any
309warranty, to the extent permitted by applicable law. You can redistribute
310them and/or modify them under the terms of the Do What The Fuck You Want
311To Public License, Version 2, as published by Sam Hocevar. See
312\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
313.PP
314\fBZzuf\fR's webpage can be found at \fBhttp://sam.zoy.org/zzuf/\fR.
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