source: zzuf/trunk/doc/zzuf.1 @ 1860

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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\-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\-F\fR \fIforks\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 \fImegabytes\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 [\fB\-\-\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
31If you want to specify flags for your application, put a \(oq\fB\-\-\fR\(cq
32marker before them on the command line (otherwise \fBzzuf\fR will try to
33interpret them as arguments for itself), eg:
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 process
80is considered to have crashed if any signal (such as, but not limited to,
81\fBSIGSEGV\fR) caused it to exit. If the \fB\-x\fR flag is used, this will
82also include processes that exit with a non-zero status.
83
84This option is only relevant if the \fB\-s\fR flag is used with a range
85argument.
86.TP
87\fB\-d\fR, \fB\-\-debug\fR
88Activate the display of debug messages.
89.TP
90\fB\-D\fR, \fB\-\-delay\fR=\fIdelay\fR
91Do not launch more than one process every \fIdelay\fR seconds. This option
92should be used together with \fB\-F\fR to avoid fork bombs.
93.TP
94\fB\-E\fR, \fB\-\-exclude\fR=\fIregex\fR
95Do not fuzz files whose name matches the \fIregex\fR regular expression. This
96option supersedes anything that is specified by the \fB\-I\fR flag. Use this
97for instance if you are unsure of what files your application is going to read
98and do not want it to fuzz files in the \fB/etc\fR directory.
99
100Multiple \fB\-E\fR flags can be specified, in which case files matching any one
101of the regular expressions will be ignored.
102.TP
103\fB\-f\fR, \fB\-\-fuzzing\fR=\fImode\fR
104Select how the input is fuzzed. Valid values for \fImode\fR are:
105.RS
106.TP
107\fBxor\fR
108randomly set and unset bits
109.TP
110\fBset\fR
111only set bits
112.TP
113\fBunset\fR
114only unset bits
115.RE
116.IP
117The default value for \fImode\fR is \fBxor\fR.
118.TP
119\fB\-F\fR, \fB\-\-max\-forks\fR=\fIforks\fR
120Specify the number of simultaneous children that can be run.
121
122This option is only relevant if the \fB\-s\fR flag is used with a range
123argument. See also the \fB\-D\fR flag.
124.TP
125\fB\-i\fR, \fB\-\-stdin\fR
126Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
127.TP
128\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
129Only fuzz files whose name matches the \fIregex\fR regular expression. Use
130this for instance if your application reads configuration files at startup
131and you only want specific files to be fuzzed.
132
133Multiple \fB\-I\fR flags can be specified, in which case files matching any one
134of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
135.TP
136\fB\-l\fR, \fB\-\-list\fR=\fIlist\fR
137Cherry-pick the list of file descriptors that get fuzzed. The Nth descriptor
138will really be fuzzed only if N is in \fIlist\fR.
139
140Values start at one and ranges are inclusive. Use dashes between values and
141commas between ranges. If the right-hand part of a range is ommited, it means
142all subsequent file descriptors. For instance, to restrict fuzzing to the
143first opened descriptor and all descriptors starting from the 10th, use
144\(oq\fB\-p1,10-\fR\(cq.
145
146Note that this option only affects file descriptors that would otherwise be
147fuzzed. Even if 10 write-only descriptors are opened at the beginning of the
148program, only the next descriptor with a read flag will be the first one
149considered by the \fB\-p\fR flag.
150.TP
151\fB\-m\fR, \fB\-\-md5\fR
152Instead of displaying the program's \fIstandard output\fR, just print its MD5
153digest to \fBzzuf\fR's standard output. The standard error channel is left
154untouched.
155.TP
156\fB\-M\fR, \fB\-\-max-memory\fR=\fImegabytes\fR
157Specify the maximum amount of memory, in megabytes, that children are allowed
158to allocate. This is useful to detect infinite loops that eat up a lot of
159memory. The value should set reasonably high so as not to interfer with normal
160program operation.
161
162\fBzzuf\fR uses the \fBsetrlimit\fR() call to set memory usage limitations and
163relies on the operating system's ability to enforce such limitations.
164.TP
165\fB\-n\fR, \fB\-\-network\fR
166Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
167.TP
168\fB\-p\fR, \fB\-\-ports\fR=\fIranges\fR
169Only fuzz network ports that are in \fIranges\fR. By default \fBzzuf\fR
170fuzzes all ports. The port considered is the listening port if the socket
171is listening and the destination port if the socket is connecting, because
172most of the time the source port cannot be predicted.
173
174Range values start at zero and are inclusive. Use dashes between range values
175and commas between ranges. If the right-hand part of a range is ommited, it
176means end of file. For instance, to restrict fuzzing to the HTTP and HTTPS
177ports and to all unprivileged ports, use \(oq\fB\-p80,443,1024-\fR\(cq.
178
179This option requires network fuzzing to be activated using \fB\-n\fR.
180.TP
181\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
182Protect a list of characters so that if they appear in input data that would
183normally be fuzzed, they are left unmodified instead.
184
185Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
186The sequences interpreted by \fBzzuf\fR are:
187.RS
188.TP
189\fB\\n\fR
190new line
191.TP
192\fB\\r\fR
193return
194.TP
195\fB\\t\fR
196tabulation
197.TP
198\fB\\\fR\fINNN\fR
199the byte whose octal value is \fINNN\fR
200.TP
201\fB\\x\fR\fINN\fR
202the byte whose hexadecimal value is \fINN\fR
203.TP
204\fB\\\\\fR
205backslash (\(oq\\\(cq)
206.RE
207.IP
208You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
209bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(aq\\001\-/\(aq\fR\(cq.
210
211The statistical outcome of this option should not be overlooked: if characters
212are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
213on the data being fuzzed. For instance, asking to fuzz 1% of input bits
214(\fB\-r0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
215result in an actual average fuzzing ratio of 0.9% with truly random data,
2160.3% with random ASCII data and 0.2% with standard English text.
217
218See also the \fB\-R\fR flag.
219.TP
220\fB\-q\fR, \fB\-\-quiet\fR
221Hide the output of the fuzzed application. This is useful if the application
222is very verbose but only its exit code or signaled status is really useful to
223you.
224.TP
225\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
226.PD 0
227.TP
228\fB\-r\fR, \fB\-\-ratio\fR=\fImin:max\fR
229.PD
230Specify the proportion of bits that will be randomly fuzzed. A value of 0
231will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
232bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
233the input files undiscernible from random data. The default fuzzing ratio
234is 0.004 (fuzz 0.4% of the files' bits).
235
236A range can also be specified. When doing so, \fBzzuf\fR will pick ratio
237values from the interval. The choice is deterministic and only depends on
238the interval bounds and the current seed.
239.TP
240\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
241Refuse a list of characters by not fuzzing bytes that would otherwise be
242changed to a character that is in \fIlist\fR. If the original byte is already
243in \fIlist\fR, it is left unchanged.
244
245See the \fB\-P\fR option for a description of \fIlist\fR.
246.TP
247\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
248.PD 0
249.TP
250\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
251.PD
252Specify the random seed to use for fuzzing, or a range of random seeds.
253Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
254the same way, even with a different target application. The purpose of this is
255to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
256causes the target application to crash.
257
258If a range is specified, \fBzzuf\fR will run the application several times,
259each time with a different seed, and report the behaviour of each run.
260.TP
261\fB\-S\fR, \fB\-\-signal\fR
262Prevent children from installing signal handlers for signals that usually
263cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
264\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
265platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
266\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
267simply crash. If you do not want core dumps, you should set appropriate limits
268with the \fBlimit coredumpsize\fR command. See your shell's documentation on
269how to set such limits.
270.TP
271\fB\-t\fR, \fB\-\-max\-time\fR=\fIn\fR
272Automatically terminate child processes that run for more than \fIn\fR
273seconds. This is useful to detect infinite loops or processes stuck in other
274situations. See also the \fB\-B\fR and \fB\-T\fR flags.
275.TP
276\fB\-T\fR, \fB\-\-max\-cpu\fR=\fIn\fR
277Automatically terminate child processes that use more than \fIn\fR seconds
278of CPU time.
279
280\fBzzuf\fR uses the \fBsetrlimit\fR() call to set CPU usage limitations and
281relies on the operating system's ability to enforce such limitations. If the
282system sends \fBSIGXCPU\fR signals and the application catches that signal,
283it will receive a \fBSIGKILL\fR signal after 5 seconds.
284
285This is more accurate than \fB\-t\fR because the behaviour should be
286independent from the system load, but it does not detect processes stuck into
287infinite \fBselect\fR() calls because they use very little CPU time. See also
288the \fB\-B\fR and \fB\-t\fR flags.
289.TP
290\fB\-v\fR, \fB\-\-verbose\fR
291Print information during the run, such as the current seed, what processes
292get run, their exit status, etc.
293.TP
294\fB\-x\fR, \fB\-\-check\-exit\fR
295Report processes that exit with a non-zero status. By default only processes
296that crash due to a signal are reported.
297.TP
298\fB\-h\fR, \fB\-\-help\fR
299Display a short help message and exit.
300.TP
301\fB\-V\fR, \fB\-\-version\fR
302Output version information and exit.
303.SH DIAGNOSTICS
304.PP
305Exit status is zero if no child process crashed. If one or several children
306crashed, \fBzzuf\fR exits with status 1.
307.SH EXAMPLES
308.PP
309Fuzz the input of the \fBcat\fR program using default settings:
310.PP
311\fB    zzuf cat /etc/motd\fR
312.PP
313Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
314.PP
315\fB    zzuf \-s94324 \-r0.01 cat /etc/motd\fR
316.PP
317Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
318and prevent non-ASCII characters from appearing in the output:
319.PP
320\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
321.PP
322Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
323original input and excluding \fB.xml\fR files from fuzzing (because
324\fBconvert\fR will also open its own XML configuration files and we do not
325want \fBzzuf\fR to fuzz them):
326.PP
327\fB    zzuf \-E \(aq\\.xml$\(aq convert \-\- foo.jpeg \-format tga /dev/null\fR
328.PP
329Fuzz the input of VLC, using file \fBmovie.avi\fR as the original input
330and restricting fuzzing to filenames that appear on the command line
331(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
332can be read by VLC to reproduce the same behaviour without using
333\fBzzuf\fR:
334.PP
335\fB    zzuf \-c \-s87423 \-r0.01 vlc movie.avi\fR
336.br
337\fB    zzuf \-c \-s87423 \-r0.01 <movie.avi >fuzzy\-movie.avi\fR
338.br
339\fB    vlc fuzzy\-movie.avi\fR
340.PP
341Fuzz between 0.1% and 2% of MPlayer's input bits (\fB\-r0.001:0.02\fR)
342with seeds 0 to 9999 (\fB\-s0:10000\fR), preserving the AVI 4-byte header
343by restricting fuzzing to offsets after 4 (\fB\-b4\-\fR), disabling its
344standard output messages (\fB\-q\fR), launching up to five simultaneous child
345processes (\fB\-F5\fR) but waiting at least half a second between launches
346(\fB\-D0.5\fR), killing MPlayer if it takes more than one minute to
347read the file (\fB\-T60\fR) and disabling its \fBSIGSEGV\fR signal handler
348(\fB\-S\fR):
349.PP
350\fB    zzuf \-c \-r0.001:0.02 \-s0:10000 \-b4\- \-q \-F5 \-D0.5 \-T60 \-S \\\fR
351.br
352\fB      mplayer \-\- \-benchmark \-vo null \-fps 1000 movie.avi\fR
353.PP
354Create an HTML-like file that loads 200 times the same \fBhello.jpg\fR image
355and open it in Firefox\(tm in auto-increment mode (\fB\-A\fR):
356.PP
357\fB    seq -f \(aq<img src="hello.jpg#%g">\(aq 1 200 > hello.html\fR
358.br
359      (or: \fBjot -w \(aq<img src="hello.jpg#%d">\(aq 200 1 > hello.html\fR)
360.br
361\fB    zzuf -A -I \(aqhello[.]jpg\(aq -r0.001 firefox hello.html\fR
362.PP
363Run a simple HTTP redirector on the local host using \fBsocat\fR and
364corrupt each network connection (\fB\-n\fR) in a different way (\fB\-A\fR)
365after one megabyte of data was received on it (\fB\-b1000000\-\fR):
366.PP
367\fB     zzuf \-n \-A \-b1000000\- \\\fR
368\fB       socat TCP4-LISTEN:8080,reuseaddr,fork TCP4:192.168.1.42:80\fR
369.SH RESTRICTIONS
370.PP
371Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR,
372\fB_RLD_LIST\fB, \fBDYLD_INSERT_LIBRARIES\fR, etc.) to run its child
373processes, it will fail in the presence of any mechanism that disables
374preloading. For instance setuid root binaries will not be fuzzed when run
375as an unprivileged user.
376.PP
377For the same reasons, \fBzzuf\fR will also not work with statically linked
378binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
379where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
380.PP
381Though best efforts are made, identical behaviour for different versions of
382\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
383different operating systems and with different target programs is only
384guaranteed when the same version of \fBzzuf\fR is being used.
385.SH BUGS
386.PP
387\fBzzuf\fR probably does not behave correctly with 64-bit offsets.
388.PP
389It is not yet possible to insert or drop bytes from the input, to fuzz
390according to the file format, to swap bytes, etc. More advanced fuzzing
391methods are planned.
392.PP
393As of now, \fBzzuf\fR does not really support multithreaded applications. The
394behaviour with multithreaded applications where more than one thread does file
395descriptor operations is undefined.
396.SH NOTES
397In order to intercept file and network operations, signal handlers and memory
398allocations, \fBzzuf\fR diverts and reimplements the following functions,
399which can be private libc symbols, too:
400.TP
401Unix file descriptor handling:
402\fBopen\fR(), \fBlseek\fR(), \fBread\fR(), \fBreadv\fR(), \fBpread\fR(),
403\fBaccept\fR(), \fBsocket\fR(), \fBrecv\fR(), \fBrecvfrom\fR(), \fBrecvmsg\fR(),
404\fBaio_read\fR(), \fBaio_return\fR(), \fBclose\fR()
405.TP
406Standard IO streams:
407\fBfopen\fR(), \fBfreopen\fR(), \fBfseek\fR(), \fBfseeko\fR(), \fBrewind\fR(),
408\fBfread\fR(), \fBgetc\fR(), \fBfgetc\fR(), \fBfgets\fR(), \fBungetc\fR(),
409\fBfclose\fR()
410.TP
411Memory management:
412\fBmmap\fR(), \fBmunmap\fR(), \fBmalloc\fR(), \fBcalloc\fR(), \fBvalloc\fR(),
413\fBfree\fR(), \fBmemalign\fR(), \fBposix_memalign\fR()
414.TP
415Linux-specific:
416\fBopen64\fR(), \fBlseek64\fR(), \fBmmap64\fR(), \fB_IO_getc\fR(),
417\fBgetline\fR(), \fBgetdelim\fR(), \fB__getdelim\fR()
418.TP
419BSD-specific:
420\fBfgetln\fR(), \fB__srefill\fR()
421.TP
422Mac OS X-specific:
423\fBmap_fd\fR()
424.TP
425Signal handling:
426\fBsignal\fR(), \fBsigaction\fR()
427.PP
428If an application manipulates file descriptors (reading data, seeking around)
429using functions that are not in that list, \fBzzuf\fR will not fuzz its
430input consistently and the results should not be trusted. You can use a tool
431such as \fBltrace(1)\fR on Linux to know the missing functions.
432.PP
433On BSD systems, such as FreeBSD or Mac OS X, \fB__srefill\fR() is enough to
434monitor all standard IO streams functions. On other systems, such as Linux,
435each function is reimplemented on a case by case basis. One important
436unimplemented function is \fBfscanf\fR(), because of its complexity. Missing
437functions will be added upon user request.
438.SH HISTORY
439.PP
440\fBzzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
441multimedia stream corrupter used to find bugs in the VLC media player.
442.SH AUTHOR
443.PP
444Copyright \(co 2002, 2007 Sam Hocevar <sam@zoy.org>.
445.PP
446\fBzzuf\fR and this manual page are free software. They come without any
447warranty, to the extent permitted by applicable law. You can redistribute
448them and/or modify them under the terms of the Do What The Fuck You Want
449To Public License, Version 2, as published by Sam Hocevar. See
450\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
451.PP
452\fBzzuf\fR's webpage can be found at \fBhttp://sam.zoy.org/zzuf/\fR.
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