source: zzuf/trunk/doc/zzuf.1 @ 2521

Last change on this file since 2521 was 2521, checked in by Sam Hocevar, 12 years ago
  • Set a default maximum memory usage value to avoid excessive swapping.
File size: 17.5 KB
Line 
1.TH zzuf 1 "2006-12-22" "zzuf"
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\-r0,3\-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 terminate child processes that output more than \fIn\fR bytes
61on the standard output and standard error channels. This is useful to detect
62infinite loops. See also the \fB\-t\fR and \fB\-T\fR flags.
63.TP
64\fB\-c\fR, \fB\-\-cmdline\fR
65Only fuzz files whose name is specified in the target application's command
66line. This is mostly a shortcut to avoid specifying twice the argument:
67
68\fB    zzuf \-c cat file.txt\fR
69
70has the same effect as
71
72\fB    zzuf \-I \(aq^file\\.txt$\(aq cat file.txt\fR
73
74See the \fB\-I\fR flag for more information on restricting fuzzing to
75specific files.
76.TP
77\fB\-C\fR, \fB\-\-max\-crashes\fR=\fIn\fR
78Stop forking when at least \fIn\fR children have crashed. The default value
79is 1, meaning \fBzzuf\fR will stop as soon as one child has crashed. A value
80of 0 tells \fBzzuf\fR to never stop.
81
82A process is considered to have crashed if any signal (such as, but not limited
83to, \fBSIGSEGV\fR) caused it to exit. If the \fB\-x\fR flag is used, this will
84also include processes that exit with a non-zero status.
85
86This option is only relevant if the \fB\-s\fR flag is used with a range
87argument.
88.TP
89\fB\-d\fR, \fB\-\-debug\fR
90Activate the display of debug messages.
91.TP
92\fB\-D\fR, \fB\-\-delay\fR=\fIdelay\fR
93Do not launch more than one process every \fIdelay\fR seconds. This option
94should be used together with \fB\-j\fR to avoid fork bombs.
95.TP
96\fB\-E\fR, \fB\-\-exclude\fR=\fIregex\fR
97Do not fuzz files whose name matches the \fIregex\fR regular expression. This
98option supersedes anything that is specified by the \fB\-I\fR flag. Use this
99for instance if you are unsure of what files your application is going to read
100and do not want it to fuzz files in the \fB/etc\fR directory.
101
102Multiple \fB\-E\fR flags can be specified, in which case files matching any one
103of the regular expressions will be ignored.
104.TP
105\fB\-f\fR, \fB\-\-fuzzing\fR=\fImode\fR
106Select how the input is fuzzed. Valid values for \fImode\fR are:
107.RS
108.TP
109\fBxor\fR
110randomly set and unset bits
111.TP
112\fBset\fR
113only set bits
114.TP
115\fBunset\fR
116only unset bits
117.RE
118.IP
119The default value for \fImode\fR is \fBxor\fR.
120.TP
121\fB\-j\fR, \fB\-\-jobs\fR=\fIjobs\fR
122Specify the number of simultaneous children that can be run. By default,
123\fBzzuf\fR only launches one process at a time.
124
125This option is only relevant if the \fB\-s\fR flag is used with a range
126argument. See also the \fB\-D\fR flag.
127.TP
128\fB\-i\fR, \fB\-\-stdin\fR
129Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
130.TP
131\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
132Only fuzz files whose name matches the \fIregex\fR regular expression. Use
133this for instance if your application reads configuration files at startup
134and you only want specific files to be fuzzed.
135
136Multiple \fB\-I\fR flags can be specified, in which case files matching any one
137of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
138.TP
139\fB\-l\fR, \fB\-\-list\fR=\fIlist\fR
140Cherry-pick the list of file descriptors that get fuzzed. The Nth descriptor
141will really be fuzzed only if N is in \fIlist\fR.
142
143Values start at 1 and ranges are inclusive. Use dashes between values and
144commas between ranges. If the right-hand part of a range is ommited, it means
145all subsequent file descriptors. For instance, to restrict fuzzing to the
146first opened descriptor and all descriptors starting from the 10th, use
147\(oq\fB\-l1,10\-\fR\(cq.
148
149Note that this option only affects file descriptors that would otherwise be
150fuzzed. Even if 10 write-only descriptors are opened at the beginning of the
151program, only the next descriptor with a read flag will be the first one
152considered by the \fB\-l\fR flag.
153.TP
154\fB\-m\fR, \fB\-\-md5\fR
155Instead of displaying the program's \fIstandard output\fR, just print its MD5
156digest to \fBzzuf\fR's standard output. The standard error channel is left
157untouched.
158.TP
159\fB\-M\fR, \fB\-\-max\-memory\fR=\fImebibytes\fR
160Specify the maximum amount of memory, in mebibytes (1 MiB = 1,048,576 bytes),
161that children are allowed to allocate. This is useful to detect infinite loops
162that eat up a lot of memory.
163
164The value should be set reasonably high so as not to interfer with normal
165program operation. By default, it is set to 1024 MiB in order to avoid
166accidental excessive swapping. To disable the limitation, set the maximum
167memory usage to -1 instead.
168
169\fBzzuf\fR uses the \fBsetrlimit\fR() call to set memory usage limitations and
170relies on the operating system's ability to enforce such limitations.
171.TP
172\fB\-n\fR, \fB\-\-network\fR
173Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
174
175Only INET (IPv4) and INET6 (IPv6) connections are fuzzed. Other protocol
176families are not yet supported.
177.TP
178\fB\-p\fR, \fB\-\-ports\fR=\fIranges\fR
179Only fuzz network ports that are in \fIranges\fR. By default \fBzzuf\fR
180fuzzes all ports. The port considered is the listening port if the socket
181is listening and the destination port if the socket is connecting, because
182most of the time the source port cannot be predicted.
183
184Range values start at zero and are inclusive. Use dashes between range values
185and commas between ranges. If the right-hand part of a range is ommited, it
186means end of file. For instance, to restrict fuzzing to the HTTP and HTTPS
187ports and to all unprivileged ports, use \(oq\fB\-p80,443,1024\-\fR\(cq.
188
189This option requires network fuzzing to be activated using \fB\-n\fR.
190.TP
191\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
192Protect a list of characters so that if they appear in input data that would
193normally be fuzzed, they are left unmodified instead.
194
195Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
196The sequences interpreted by \fBzzuf\fR are:
197.RS
198.TP
199\fB\\n\fR
200new line
201.TP
202\fB\\r\fR
203return
204.TP
205\fB\\t\fR
206tabulation
207.TP
208\fB\\\fR\fINNN\fR
209the byte whose octal value is \fINNN\fR
210.TP
211\fB\\x\fR\fINN\fR
212the byte whose hexadecimal value is \fINN\fR
213.TP
214\fB\\\\\fR
215backslash (\(oq\\\(cq)
216.RE
217.IP
218You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
219bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(aq\\001\-/\(aq\fR\(cq.
220
221The statistical outcome of this option should not be overlooked: if characters
222are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
223on the data being fuzzed. For instance, asking to fuzz 1% of input bits
224(\fB\-r0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
225result in an actual average fuzzing ratio of 0.9% with truly random data,
2260.3% with random ASCII data and 0.2% with standard English text.
227
228See also the \fB\-R\fR flag.
229.TP
230\fB\-q\fR, \fB\-\-quiet\fR
231Hide the output of the fuzzed application. This is useful if the application
232is very verbose but only its exit code or signaled status is really useful to
233you.
234.TP
235\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
236.PD 0
237.TP
238\fB\-r\fR, \fB\-\-ratio\fR=\fImin:max\fR
239.PD
240Specify the proportion of bits that will be randomly fuzzed. A value of 0
241will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
242bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
243the input files undiscernible from random data. The default fuzzing ratio
244is 0.004 (fuzz 0.4% of the files' bits).
245
246A range can also be specified. When doing so, \fBzzuf\fR will pick ratio
247values from the interval. The choice is deterministic and only depends on
248the interval bounds and the current seed.
249.TP
250\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
251Refuse a list of characters by not fuzzing bytes that would otherwise be
252changed to a character that is in \fIlist\fR. This does not prevent characters
253from appearing in the output if the original byte was already in \fIlist\fR.
254
255See the \fB\-P\fR option for a description of \fIlist\fR.
256.TP
257\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
258.PD 0
259.TP
260\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
261.PD
262Specify the random seed to use for fuzzing, or a range of random seeds.
263Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
264the same way, even with a different target application. The purpose of this is
265to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
266causes the target application to crash.
267
268If a range is specified, \fBzzuf\fR will run the application several times,
269each time with a different seed, and report the behaviour of each run. If the
270\(oq:\(cq character is used but the second part of the range is omitted,
271\fBzzuf\fR will increment the seed value indefinitely.
272.TP
273\fB\-S\fR, \fB\-\-signal\fR
274Prevent children from installing signal handlers for signals that usually
275cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
276\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
277platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
278\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
279simply crash. If you do not want core dumps, you should set appropriate limits
280with the \fBlimit coredumpsize\fR command. See your shell's documentation on
281how to set such limits.
282.TP
283\fB\-t\fR, \fB\-\-max\-time\fR=\fIn\fR
284Automatically terminate child processes that run for more than \fIn\fR
285seconds. This is useful to detect infinite loops or processes stuck in other
286situations. See also the \fB\-B\fR and \fB\-T\fR flags.
287.TP
288\fB\-T\fR, \fB\-\-max\-cpu\fR=\fIn\fR
289Automatically terminate child processes that use more than \fIn\fR seconds
290of CPU time.
291
292\fBzzuf\fR uses the \fBsetrlimit\fR() call to set CPU usage limitations and
293relies on the operating system's ability to enforce such limitations. If the
294system sends \fBSIGXCPU\fR signals and the application catches that signal,
295it will receive a \fBSIGKILL\fR signal after 5 seconds.
296
297This is more accurate than \fB\-t\fR because the behaviour should be
298independent from the system load, but it does not detect processes stuck into
299infinite \fBselect\fR() calls because they use very little CPU time. See also
300the \fB\-B\fR and \fB\-t\fR flags.
301.TP
302\fB\-v\fR, \fB\-\-verbose\fR
303Print information during the run, such as the current seed, what processes
304get run, their exit status, etc.
305.TP
306\fB\-x\fR, \fB\-\-check\-exit\fR
307Report processes that exit with a non-zero status. By default only processes
308that crash due to a signal are reported.
309.TP
310\fB\-h\fR, \fB\-\-help\fR
311Display a short help message and exit.
312.TP
313\fB\-V\fR, \fB\-\-version\fR
314Output version information and exit.
315.SH DIAGNOSTICS
316.PP
317Exit status is zero if no child process crashed. If one or several children
318crashed, \fBzzuf\fR exits with status 1.
319.SH EXAMPLES
320.PP
321Fuzz the input of the \fBcat\fR program using default settings:
322.PP
323\fB    zzuf cat /etc/motd\fR
324.PP
325Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
326.PP
327\fB    zzuf \-s94324 \-r0.01 cat /etc/motd\fR
328.PP
329Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
330and prevent non-ASCII characters from appearing in the output:
331.PP
332\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
333.PP
334Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
335original input and excluding \fB.xml\fR files from fuzzing (because
336\fBconvert\fR will also open its own XML configuration files and we do not
337want \fBzzuf\fR to fuzz them):
338.PP
339\fB    zzuf \-E \(aq\\.xml$\(aq convert foo.jpeg \-format tga /dev/null\fR
340.PP
341Fuzz the input of VLC, using file \fBmovie.avi\fR as the original input
342and restricting fuzzing to filenames that appear on the command line
343(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
344can be read by VLC to reproduce the same behaviour without using
345\fBzzuf\fR:
346.PP
347\fB    zzuf \-c \-s87423 \-r0.01 vlc movie.avi\fR
348.br
349\fB    zzuf \-c \-s87423 \-r0.01 <movie.avi >fuzzy\-movie.avi\fR
350.br
351\fB    vlc fuzzy\-movie.avi\fR
352.PP
353Fuzz between 0.1% and 2% of MPlayer's input bits (\fB\-r0.001:0.02\fR)
354with seeds 0 to 9999 (\fB\-s0:10000\fR), preserving the AVI 4-byte header
355by restricting fuzzing to offsets after 4 (\fB\-b4\-\fR), disabling its
356standard output messages (\fB\-q\fR), launching up to five simultaneous child
357processes (\fB\-j5\fR) but waiting at least half a second between launches
358(\fB\-D0.5\fR), killing MPlayer if it takes more than one minute to
359read the file (\fB\-T60\fR) and disabling its \fBSIGSEGV\fR signal handler
360(\fB\-S\fR):
361.PP
362\fB    zzuf \-c \-r0.001:0.02 \-s0:10000 \-b4\- \-q \-j5 \-D0.5 \-T60 \-S \\\fR
363.br
364\fB      mplayer \-benchmark \-vo null \-fps 1000 movie.avi\fR
365.PP
366Create an HTML-like file that loads 200 times the same \fBhello.jpg\fR image
367and open it in Firefox\(tm in auto-increment mode (\fB\-A\fR):
368.PP
369\fB    seq \-f \(aq<img src="hello.jpg#%g">\(aq 1 200 > hello.html\fR
370.br
371      (or: \fBjot \-w \(aq<img src="hello.jpg#%d">\(aq 200 1 > hello.html\fR)
372.br
373\fB    zzuf \-A \-I \(aqhello[.]jpg\(aq \-r0.001 firefox hello.html\fR
374.PP
375Run a simple HTTP redirector on the local host using \fBsocat\fR and
376corrupt each network connection (\fB\-n\fR) in a different way (\fB\-A\fR)
377after one megabyte of data was received on it (\fB\-b1000000\-\fR):
378.PP
379\fB     zzuf \-n \-A \-b1000000\- \\\fR
380\fB       socat TCP4\-LISTEN:8080,reuseaddr,fork TCP4:192.168.1.42:80\fR
381.PP
382Browse the intarweb (\fB\-n\fR) using Firefox\(tm without fuzzing local files
383(\fB\-E.\fR) or non-HTTP connections (\fB\-p80,8010,8080\fR), preserving
384the beginning of the data sent with each HTTP response (\fB\-b4000\-\fR)
385and using another seed on each connection (\fB\-A\fR):
386.PP
387\fB    zzuf \-r 0.0001 \-n \-E. \-p80,8010,8080 \-b4000\- \-A firefox\fR
388.SH RESTRICTIONS
389.PP
390Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR,
391\fB_RLD_LIST\fB, \fBDYLD_INSERT_LIBRARIES\fR, etc.) to run its child
392processes, it will fail in the presence of any mechanism that disables
393preloading. For instance setuid root binaries will not be fuzzed when run
394as an unprivileged user.
395.PP
396For the same reasons, \fBzzuf\fR will also not work with statically linked
397binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
398where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
399.PP
400Though best efforts are made, identical behaviour for different versions of
401\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
402different operating systems and with different target programs is only
403guaranteed when the same version of \fBzzuf\fR is being used.
404.SH BUGS
405.PP
406\fBzzuf\fR probably does not behave correctly with 64-bit offsets.
407.PP
408It is not yet possible to insert or drop bytes from the input, to fuzz
409according to the file format, to swap bytes, etc. More advanced fuzzing
410methods are planned.
411.PP
412As of now, \fBzzuf\fR does not really support multithreaded applications. The
413behaviour with multithreaded applications where more than one thread does file
414descriptor operations is undefined.
415.SH HISTORY
416.PP
417\fBzzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
418multimedia stream corrupter used to find bugs in the VLC media player.
419.SH SEE ALSO
420.PP
421\fBlibzzuf(3)\fR
422.SH AUTHOR
423.PP
424Copyright \(co 2002, 2007\-2008 Sam Hocevar <sam@zoy.org>.
425.PP
426\fBzzuf\fR and this manual page are free software. They come without any
427warranty, to the extent permitted by applicable law. You can redistribute
428them and/or modify them under the terms of the Do What The Fuck You Want
429To Public License, Version 2, as published by Sam Hocevar. See
430\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
431.PP
432\fBzzuf\fR's webpage can be found at \fBhttp://libcaca.zoy.org/wiki/zzuf\fR.
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