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1.TH zzuf 1 "2010-01-06" "zzuf @PACKAGE_VERSION@"
2.SH NAME
3zzuf \- multiple purpose fuzzer
4.SH SYNOPSIS
5\fBzzuf\fR [\fB\-AcdimnqSvx\fR] [\fB\-s\fR \fIseed\fR|\fB\-s\fR \fIstart:stop\fR] [\fB\-r\fR \fIratio\fR|\fB\-r\fR \fImin:max\fR]
6.br
7       [\fB\-f\fR \fIfuzzing\fR] [\fB\-D\fR \fIdelay\fR] [\fB\-j\fR \fIjobs\fR] [\fB\-C\fR \fIcrashes\fR] [\fB\-B\fR \fIbytes\fR]
8.br
9       [\fB\-t\fR \fIseconds\fR] [\fB\-T\fR \fIseconds\fR] [\fB\-M\fR \fImebibytes\fR] [\fB\-b\fR \fIranges\fR] [\fB\-p\fR \fIports\fR]
10.br
11       [\fB\-P\fR \fIprotect\fR] [\fB\-R\fR \fIrefuse\fR] [\fB\-l\fR \fIlist\fR] [\fB\-I\fR \fIinclude\fR] [\fB\-E\fR \fIexclude\fR]
12.br
13       [\fIPROGRAM\fR [\fIARGS\fR]...]
14.br
15\fBzzuf \-h\fR | \fB\-\-help\fR
16.br
17\fBzzuf \-V\fR | \fB\-\-version\fR
18.SH DESCRIPTION
19.PP
20\fBzzuf\fR is a transparent application input fuzzer. It works by intercepting
21file and network operations and changing random bits in the program's input.
22\fBzzuf\fR's behaviour is deterministic, making it easy to reproduce bugs.
23.SH USAGE
24.PP
25\fBzzuf\fR will run an application specified on its command line, one or
26several times, with optional arguments, and will report the application's
27relevant behaviour on the standard error channel, eg:
28.PP
29\fB    zzuf cat /dev/zero\fR
30.PP
31Flags found after the application name are considered arguments for the
32application, not for \fBzzuf\fR. For instance, \fB\-v\fR below is an
33argument for \fBcat\fR:
34.PP
35\fB    zzuf \-B 1000 cat \-v /dev/zero\fR
36.PP
37When no program is specified, \fBzzuf\fR simply fuzzes the standard input, as
38if the \fBcat\fR utility had been called:
39.PP
40\fB    zzuf < /dev/zero\fR
41.SH OPTIONS
42.TP
43\fB\-A\fR, \fB\-\-autoinc\fR
44Increment random seed each time a new file is opened. This is only required
45if one instance of the application is expected to open the same file several
46times and you want to test a different seed each time.
47.TP
48\fB\-b\fR, \fB\-\-bytes\fR=\fIranges\fR
49Restrict fuzzing to bytes whose offsets in the file are within \fIranges\fR.
50
51Range values start at zero and are inclusive. Use dashes between range values
52and commas between ranges. If the right-hand part of a range is ommited, it
53means end of file. For instance, to restrict fuzzing to bytes 0, 3, 4, 5 and
54all bytes after offset 31, use \(oq\fB\-b0,3\-5,31\-\fR\(cq.
55
56This option is useful to preserve file headers or corrupt only a specific
57portion of a file.
58.TP
59\fB\-B\fR, \fB\-\-max\-bytes\fR=\fIn\fR
60Automatically stop after \fIn\fR bytes have been output.
61
62This either terminates child processes that output more than \fIn\fR bytes
63on the standard output and standard error channels, or stop reading from
64standard input if no program is being fuzzed.
65
66This is useful to detect infinite loops. See also the \fB\-t\fR and \fB\-T\fR
67flags.
68.TP
69\fB\-c\fR, \fB\-\-cmdline\fR
70Only fuzz files whose name is specified in the target application's command
71line. This is mostly a shortcut to avoid specifying twice the argument:
72
73\fB    zzuf \-c cat file.txt\fR
74
75has the same effect as
76
77\fB    zzuf \-I \(aq^file\\.txt$\(aq cat file.txt\fR
78
79See the \fB\-I\fR flag for more information on restricting fuzzing to
80specific files.
81.TP
82\fB\-C\fR, \fB\-\-max\-crashes\fR=\fIn\fR
83Stop forking when at least \fIn\fR children have crashed. The default value
84is 1, meaning \fBzzuf\fR will stop as soon as one child has crashed. A value
85of 0 tells \fBzzuf\fR to never stop.
86
87A process is considered to have crashed if any signal (such as, but not limited
88to, \fBSIGSEGV\fR) caused it to exit. If the \fB\-x\fR flag is used, this will
89also include processes that exit with a non-zero status.
90
91This option is only relevant if the \fB\-s\fR flag is used with a range
92argument.
93.TP
94\fB\-d\fR, \fB\-\-debug\fR
95Activate the display of debug messages. Can be specified multiple times for
96increased verbosity.
97.TP
98\fB\-D\fR, \fB\-\-delay\fR=\fIdelay\fR
99Do not launch more than one process every \fIdelay\fR seconds. This option
100should be used together with \fB\-j\fR to avoid fork bombs.
101.TP
102\fB\-E\fR, \fB\-\-exclude\fR=\fIregex\fR
103Do not fuzz files whose name matches the \fIregex\fR regular expression. This
104option supersedes anything that is specified by the \fB\-I\fR flag. Use this
105for instance if you are unsure of what files your application is going to read
106and do not want it to fuzz files in the \fB/etc\fR directory.
107
108Multiple \fB\-E\fR flags can be specified, in which case files matching any one
109of the regular expressions will be ignored.
110.TP
111\fB\-f\fR, \fB\-\-fuzzing\fR=\fImode\fR
112Select how the input is fuzzed. Valid values for \fImode\fR are:
113.RS
114.TP
115\fBxor\fR
116randomly set and unset bits
117.TP
118\fBset\fR
119only set bits
120.TP
121\fBunset\fR
122only unset bits
123.RE
124.IP
125The default value for \fImode\fR is \fBxor\fR.
126.TP
127\fB\-j\fR, \fB\-\-jobs\fR=\fIjobs\fR
128Specify the number of simultaneous children that can be run. By default,
129\fBzzuf\fR only launches one process at a time.
130
131This option is only relevant if the \fB\-s\fR flag is used with a range
132argument. See also the \fB\-D\fR flag.
133.TP
134\fB\-i\fR, \fB\-\-stdin\fR
135Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
136.TP
137\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
138Only fuzz files whose name matches the \fIregex\fR regular expression. Use
139this for instance if your application reads configuration files at startup
140and you only want specific files to be fuzzed.
141
142Multiple \fB\-I\fR flags can be specified, in which case files matching any one
143of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
144.TP
145\fB\-l\fR, \fB\-\-list\fR=\fIlist\fR
146Cherry-pick the list of file descriptors that get fuzzed. The Nth descriptor
147will really be fuzzed only if N is in \fIlist\fR.
148
149Values start at 1 and ranges are inclusive. Use dashes between values and
150commas between ranges. If the right-hand part of a range is ommited, it means
151all subsequent file descriptors. For instance, to restrict fuzzing to the
152first opened descriptor and all descriptors starting from the 10th, use
153\(oq\fB\-l1,10\-\fR\(cq.
154
155Note that this option only affects file descriptors that would otherwise be
156fuzzed. Even if 10 write-only descriptors are opened at the beginning of the
157program, only the next descriptor with a read flag will be the first one
158considered by the \fB\-l\fR flag.
159.TP
160\fB\-m\fR, \fB\-\-md5\fR
161Instead of displaying the program's \fIstandard output\fR, just print its MD5
162digest to \fBzzuf\fR's standard output. The standard error channel is left
163untouched.
164.TP
165\fB\-M\fR, \fB\-\-max\-memory\fR=\fImebibytes\fR
166Specify the maximum amount of memory, in mebibytes (1 MiB = 1,048,576 bytes),
167that children are allowed to allocate. This is useful to detect infinite loops
168that eat up a lot of memory.
169
170The value should be set reasonably high so as not to interfer with normal
171program operation. By default, it is set to 1024 MiB in order to avoid
172accidental excessive swapping. To disable the limitation, set the maximum
173memory usage to -1 instead.
174
175\fBzzuf\fR uses the \fBsetrlimit\fR() call to set memory usage limitations and
176relies on the operating system's ability to enforce such limitations.
177.TP
178\fB\-n\fR, \fB\-\-network\fR
179Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
180
181Only INET (IPv4) and INET6 (IPv6) connections are fuzzed. Other protocol
182families are not yet supported.
183.TP
184\fB\-p\fR, \fB\-\-ports\fR=\fIranges\fR
185Only fuzz network ports that are in \fIranges\fR. By default \fBzzuf\fR
186fuzzes all ports. The port considered is the listening port if the socket
187is listening and the destination port if the socket is connecting, because
188most of the time the source port cannot be predicted.
189
190Range values start at zero and are inclusive. Use dashes between range values
191and commas between ranges. If the right-hand part of a range is ommited, it
192means end of file. For instance, to restrict fuzzing to the HTTP and HTTPS
193ports and to all unprivileged ports, use \(oq\fB\-p80,443,1024\-\fR\(cq.
194
195This option requires network fuzzing to be activated using \fB\-n\fR.
196.TP
197\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
198Protect a list of characters so that if they appear in input data that would
199normally be fuzzed, they are left unmodified instead.
200
201Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
202The sequences interpreted by \fBzzuf\fR are:
203.RS
204.TP
205\fB\\n\fR
206new line
207.TP
208\fB\\r\fR
209return
210.TP
211\fB\\t\fR
212tabulation
213.TP
214\fB\\\fR\fINNN\fR
215the byte whose octal value is \fINNN\fR
216.TP
217\fB\\x\fR\fINN\fR
218the byte whose hexadecimal value is \fINN\fR
219.TP
220\fB\\\\\fR
221backslash (\(oq\\\(cq)
222.RE
223.IP
224You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
225bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(aq\\001\-/\(aq\fR\(cq.
226
227The statistical outcome of this option should not be overlooked: if characters
228are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
229on the data being fuzzed. For instance, asking to fuzz 1% of input bits
230(\fB\-r0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
231result in an actual average fuzzing ratio of 0.9% with truly random data,
2320.3% with random ASCII data and 0.2% with standard English text.
233
234See also the \fB\-R\fR flag.
235.TP
236\fB\-q\fR, \fB\-\-quiet\fR
237Hide the output of the fuzzed application. This is useful if the application
238is very verbose but only its exit code or signaled status is really useful to
239you.
240.TP
241\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
242.PD 0
243.TP
244\fB\-r\fR, \fB\-\-ratio\fR=\fImin:max\fR
245.PD
246Specify the proportion of bits that will be randomly fuzzed. A value of 0
247will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
248bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
249the input files undiscernible from random data. The default fuzzing ratio
250is 0.004 (fuzz 0.4% of the files' bits).
251
252A range can also be specified. When doing so, \fBzzuf\fR will pick ratio
253values from the interval. The choice is deterministic and only depends on
254the interval bounds and the current seed.
255.TP
256\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
257Refuse a list of characters by not fuzzing bytes that would otherwise be
258changed to a character that is in \fIlist\fR. This does not prevent characters
259from appearing in the output if the original byte was already in \fIlist\fR.
260
261See the \fB\-P\fR option for a description of \fIlist\fR.
262.TP
263\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
264.PD 0
265.TP
266\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
267.PD
268Specify the random seed to use for fuzzing, or a range of random seeds.
269Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
270the same way, even with a different target application. The purpose of this is
271to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
272causes the target application to crash.
273
274If a range is specified, \fBzzuf\fR will run the application several times,
275each time with a different seed, and report the behaviour of each run. If the
276\(oq:\(cq character is used but the second part of the range is omitted,
277\fBzzuf\fR will increment the seed value indefinitely.
278.TP
279\fB\-S\fR, \fB\-\-signal\fR
280Prevent children from installing signal handlers for signals that usually
281cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
282\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
283platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
284\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
285simply crash. If you do not want core dumps, you should set appropriate limits
286with the \fBlimit coredumpsize\fR command. See your shell's documentation on
287how to set such limits.
288.TP
289\fB\-t\fR, \fB\-\-max\-time\fR=\fIn\fR
290Automatically terminate child processes that run for more than \fIn\fR
291seconds. This is useful to detect infinite loops or processes stuck in other
292situations. See also the \fB\-B\fR and \fB\-T\fR flags.
293.TP
294\fB\-T\fR, \fB\-\-max\-cputime\fR=\fIn\fR
295Automatically terminate child processes that use more than \fIn\fR seconds
296of CPU time.
297
298\fBzzuf\fR uses the \fBsetrlimit\fR() call to set CPU usage limitations and
299relies on the operating system's ability to enforce such limitations. If the
300system sends \fBSIGXCPU\fR signals and the application catches that signal,
301it will receive a \fBSIGKILL\fR signal after 5 seconds.
302
303This is more accurate than \fB\-t\fR because the behaviour should be
304independent from the system load, but it does not detect processes stuck into
305infinite \fBselect\fR() calls because they use very little CPU time. See also
306the \fB\-B\fR and \fB\-t\fR flags.
307.TP
308\fB\-v\fR, \fB\-\-verbose\fR
309Print information during the run, such as the current seed, what processes
310get run, their exit status, etc.
311.TP
312\fB\-x\fR, \fB\-\-check\-exit\fR
313Report processes that exit with a non-zero status. By default only processes
314that crash due to a signal are reported.
315.TP
316\fB\-h\fR, \fB\-\-help\fR
317Display a short help message and exit.
318.TP
319\fB\-V\fR, \fB\-\-version\fR
320Output version information and exit.
321.SH DIAGNOSTICS
322.PP
323Exit status is zero if no child process crashed. If one or several children
324crashed, \fBzzuf\fR exits with status 1.
325.SH EXAMPLES
326.PP
327Fuzz the input of the \fBcat\fR program using default settings:
328.PP
329\fB    zzuf cat /etc/motd\fR
330.PP
331Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
332.PP
333\fB    zzuf \-s94324 \-r0.01 cat /etc/motd\fR
334.PP
335Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
336and prevent non-ASCII characters from appearing in the output:
337.PP
338\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
339.PP
340Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
341original input and excluding \fB.xml\fR files from fuzzing (because
342\fBconvert\fR will also open its own XML configuration files and we do not
343want \fBzzuf\fR to fuzz them):
344.PP
345\fB    zzuf \-E \(aq\\.xml$\(aq convert foo.jpeg \-format tga /dev/null\fR
346.PP
347Fuzz the input of VLC, using file \fBmovie.avi\fR as the original input
348and restricting fuzzing to filenames that appear on the command line
349(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
350can be read by VLC to reproduce the same behaviour without using
351\fBzzuf\fR:
352.PP
353\fB    zzuf \-c \-s87423 \-r0.01 vlc movie.avi\fR
354.br
355\fB    zzuf \-c \-s87423 \-r0.01 <movie.avi >fuzzy\-movie.avi\fR
356.br
357\fB    vlc fuzzy\-movie.avi\fR
358.PP
359Fuzz between 0.1% and 2% of MPlayer's input bits (\fB\-r0.001:0.02\fR)
360with seeds 0 to 9999 (\fB\-s0:10000\fR), preserving the AVI 4-byte header
361by restricting fuzzing to offsets after 4 (\fB\-b4\-\fR), disabling its
362standard output messages (\fB\-q\fR), launching up to five simultaneous child
363processes (\fB\-j5\fR) but waiting at least half a second between launches
364(\fB\-D0.5\fR), killing MPlayer if it takes more than one minute to
365read the file (\fB\-T60\fR) and disabling its \fBSIGSEGV\fR signal handler
366(\fB\-S\fR):
367.PP
368\fB    zzuf \-c \-r0.001:0.02 \-s0:10000 \-b4\- \-q \-j5 \-D0.5 \-T60 \-S \\\fR
369.br
370\fB      mplayer \-benchmark \-vo null \-fps 1000 movie.avi\fR
371.PP
372A more advanced VLC fuzzing example, stopping only at the first crash:
373.PP
374\fB    zzuf \-j4 \-vqc \-r0.000001:0.01 \-s0: vlc \-v \-I dummy movie.avi \\\fR
375.br
376\fB       \-\-sout \(aq#transcode{acodec=s16l,vcodec=I420}:dummy\(aq vlc:quit
377.PP
378Create an HTML-like file that loads 200 times the same \fBhello.jpg\fR image
379and open it in Firefox\(tm in auto-increment mode (\fB\-A\fR):
380.PP
381\fB    seq \-f \(aq<img src="hello.jpg#%g">\(aq 1 200 > hello.html\fR
382.br
383      (or: \fBjot \-w \(aq<img src="hello.jpg#%d">\(aq 200 1 > hello.html\fR)
384.br
385\fB    zzuf \-A \-I \(aqhello[.]jpg\(aq \-r0.001 firefox hello.html\fR
386.PP
387Run a simple HTTP redirector on the local host using \fBsocat\fR and
388corrupt each network connection (\fB\-n\fR) in a different way (\fB\-A\fR)
389after one megabyte of data was received on it (\fB\-b1000000\-\fR):
390.PP
391\fB     zzuf \-n \-A \-b1000000\- \\\fR
392\fB       socat TCP4\-LISTEN:8080,reuseaddr,fork TCP4:192.168.1.42:80\fR
393.PP
394Browse the intarweb (\fB\-n\fR) using Firefox\(tm without fuzzing local files
395(\fB\-E.\fR) or non-HTTP connections (\fB\-p80,8010,8080\fR), preserving
396the beginning of the data sent with each HTTP response (\fB\-b4000\-\fR)
397and using another seed on each connection (\fB\-A\fR):
398.PP
399\fB    zzuf \-r 0.0001 \-n \-E. \-p80,8010,8080 \-b4000\- \-A firefox\fR
400.SH RESTRICTIONS
401.PP
402Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR,
403\fB_RLD_LIST\fB, \fBDYLD_INSERT_LIBRARIES\fR, etc.) to run its child
404processes, it will fail in the presence of any mechanism that disables
405preloading. For instance setuid root binaries will not be fuzzed when run
406as an unprivileged user.
407.PP
408For the same reasons, \fBzzuf\fR will also not work with statically linked
409binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
410where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
411.PP
412Though best efforts are made, identical behaviour for different versions of
413\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
414different operating systems and with different target programs is only
415guaranteed when the same version of \fBzzuf\fR is being used.
416.SH BUGS
417.PP
418\fBzzuf\fR probably does not behave correctly with 64-bit offsets.
419.PP
420It is not yet possible to insert or drop bytes from the input, to fuzz
421according to the file format, to swap bytes, etc. More advanced fuzzing
422methods are planned.
423.PP
424As of now, \fBzzuf\fR does not really support multithreaded applications. The
425behaviour with multithreaded applications where more than one thread does file
426descriptor operations is undefined.
427.SH HISTORY
428.PP
429\fBzzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
430multimedia stream corrupter used to find bugs in the VLC media player.
431.SH SEE ALSO
432.PP
433\fBlibzzuf(3)\fR, \fBzzcat(1)\fR
434.SH AUTHOR
435.PP
436Copyright \(co 2002, 2007\-2010 Sam Hocevar <sam@hocevar.net>.
437.PP
438\fBzzuf\fR and this manual page are free software. They come without any
439warranty, to the extent permitted by applicable law. You can redistribute
440them and/or modify them under the terms of the Do What The Fuck You Want
441To Public License, Version 2, as published by Sam Hocevar. See
442\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
443.PP
444\fBzzuf\fR's webpage can be found at \fBhttp://caca.zoy.org/wiki/zzuf\fR.
445An overview of the architecture and inner works is at
446\fBhttp://caca.zoy.org/wiki/zzuf/internals\fR.
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