source: zzuf/trunk/doc/zzuf.1 @ 2331

Last change on this file since 2331 was 2331, checked in by sam, 6 years ago
  • Implement fgets_unlocked() and fread_unlocked().
File size: 18.9 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\-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 [\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 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. By default,
121\fBzzuf\fR only launches one process at a time.
122
123This option is only relevant if the \fB\-s\fR flag is used with a range
124argument. See also the \fB\-D\fR flag.
125.TP
126\fB\-i\fR, \fB\-\-stdin\fR
127Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
128.TP
129\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
130Only fuzz files whose name matches the \fIregex\fR regular expression. Use
131this for instance if your application reads configuration files at startup
132and you only want specific files to be fuzzed.
133
134Multiple \fB\-I\fR flags can be specified, in which case files matching any one
135of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
136.TP
137\fB\-l\fR, \fB\-\-list\fR=\fIlist\fR
138Cherry-pick the list of file descriptors that get fuzzed. The Nth descriptor
139will really be fuzzed only if N is in \fIlist\fR.
140
141Values start at 1 and ranges are inclusive. Use dashes between values and
142commas between ranges. If the right-hand part of a range is ommited, it means
143all subsequent file descriptors. For instance, to restrict fuzzing to the
144first opened descriptor and all descriptors starting from the 10th, use
145\(oq\fB\-l1,10\-\fR\(cq.
146
147Note that this option only affects file descriptors that would otherwise be
148fuzzed. Even if 10 write-only descriptors are opened at the beginning of the
149program, only the next descriptor with a read flag will be the first one
150considered by the \fB\-l\fR flag.
151.TP
152\fB\-m\fR, \fB\-\-md5\fR
153Instead of displaying the program's \fIstandard output\fR, just print its MD5
154digest to \fBzzuf\fR's standard output. The standard error channel is left
155untouched.
156.TP
157\fB\-M\fR, \fB\-\-max\-memory\fR=\fImegabytes\fR
158Specify the maximum amount of memory, in megabytes, that children are allowed
159to allocate. This is useful to detect infinite loops that eat up a lot of
160memory. The value should set reasonably high so as not to interfer with normal
161program operation.
162
163\fBzzuf\fR uses the \fBsetrlimit\fR() call to set memory usage limitations and
164relies on the operating system's ability to enforce such limitations.
165.TP
166\fB\-n\fR, \fB\-\-network\fR
167Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
168
169Only INET (IPv4) and INET6 (IPv6) connections are fuzzed. Other protocol
170families are not yet supported.
171.TP
172\fB\-p\fR, \fB\-\-ports\fR=\fIranges\fR
173Only fuzz network ports that are in \fIranges\fR. By default \fBzzuf\fR
174fuzzes all ports. The port considered is the listening port if the socket
175is listening and the destination port if the socket is connecting, because
176most of the time the source port cannot be predicted.
177
178Range values start at zero and are inclusive. Use dashes between range values
179and commas between ranges. If the right-hand part of a range is ommited, it
180means end of file. For instance, to restrict fuzzing to the HTTP and HTTPS
181ports and to all unprivileged ports, use \(oq\fB\-p80,443,1024\-\fR\(cq.
182
183This option requires network fuzzing to be activated using \fB\-n\fR.
184.TP
185\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
186Protect a list of characters so that if they appear in input data that would
187normally be fuzzed, they are left unmodified instead.
188
189Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
190The sequences interpreted by \fBzzuf\fR are:
191.RS
192.TP
193\fB\\n\fR
194new line
195.TP
196\fB\\r\fR
197return
198.TP
199\fB\\t\fR
200tabulation
201.TP
202\fB\\\fR\fINNN\fR
203the byte whose octal value is \fINNN\fR
204.TP
205\fB\\x\fR\fINN\fR
206the byte whose hexadecimal value is \fINN\fR
207.TP
208\fB\\\\\fR
209backslash (\(oq\\\(cq)
210.RE
211.IP
212You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
213bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(aq\\001\-/\(aq\fR\(cq.
214
215The statistical outcome of this option should not be overlooked: if characters
216are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
217on the data being fuzzed. For instance, asking to fuzz 1% of input bits
218(\fB\-r0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
219result in an actual average fuzzing ratio of 0.9% with truly random data,
2200.3% with random ASCII data and 0.2% with standard English text.
221
222See also the \fB\-R\fR flag.
223.TP
224\fB\-q\fR, \fB\-\-quiet\fR
225Hide the output of the fuzzed application. This is useful if the application
226is very verbose but only its exit code or signaled status is really useful to
227you.
228.TP
229\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
230.PD 0
231.TP
232\fB\-r\fR, \fB\-\-ratio\fR=\fImin:max\fR
233.PD
234Specify the proportion of bits that will be randomly fuzzed. A value of 0
235will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
236bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
237the input files undiscernible from random data. The default fuzzing ratio
238is 0.004 (fuzz 0.4% of the files' bits).
239
240A range can also be specified. When doing so, \fBzzuf\fR will pick ratio
241values from the interval. The choice is deterministic and only depends on
242the interval bounds and the current seed.
243.TP
244\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
245Refuse a list of characters by not fuzzing bytes that would otherwise be
246changed to a character that is in \fIlist\fR. This does not prevent characters
247from appearing in the output if the original byte was already in \fIlist\fR.
248
249See the \fB\-P\fR option for a description of \fIlist\fR.
250.TP
251\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
252.PD 0
253.TP
254\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
255.PD
256Specify the random seed to use for fuzzing, or a range of random seeds.
257Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
258the same way, even with a different target application. The purpose of this is
259to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
260causes the target application to crash.
261
262If a range is specified, \fBzzuf\fR will run the application several times,
263each time with a different seed, and report the behaviour of each run.
264.TP
265\fB\-S\fR, \fB\-\-signal\fR
266Prevent children from installing signal handlers for signals that usually
267cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
268\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
269platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
270\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
271simply crash. If you do not want core dumps, you should set appropriate limits
272with the \fBlimit coredumpsize\fR command. See your shell's documentation on
273how to set such limits.
274.TP
275\fB\-t\fR, \fB\-\-max\-time\fR=\fIn\fR
276Automatically terminate child processes that run for more than \fIn\fR
277seconds. This is useful to detect infinite loops or processes stuck in other
278situations. See also the \fB\-B\fR and \fB\-T\fR flags.
279.TP
280\fB\-T\fR, \fB\-\-max\-cpu\fR=\fIn\fR
281Automatically terminate child processes that use more than \fIn\fR seconds
282of CPU time.
283
284\fBzzuf\fR uses the \fBsetrlimit\fR() call to set CPU usage limitations and
285relies on the operating system's ability to enforce such limitations. If the
286system sends \fBSIGXCPU\fR signals and the application catches that signal,
287it will receive a \fBSIGKILL\fR signal after 5 seconds.
288
289This is more accurate than \fB\-t\fR because the behaviour should be
290independent from the system load, but it does not detect processes stuck into
291infinite \fBselect\fR() calls because they use very little CPU time. See also
292the \fB\-B\fR and \fB\-t\fR flags.
293.TP
294\fB\-v\fR, \fB\-\-verbose\fR
295Print information during the run, such as the current seed, what processes
296get run, their exit status, etc.
297.TP
298\fB\-x\fR, \fB\-\-check\-exit\fR
299Report processes that exit with a non-zero status. By default only processes
300that crash due to a signal are reported.
301.TP
302\fB\-h\fR, \fB\-\-help\fR
303Display a short help message and exit.
304.TP
305\fB\-V\fR, \fB\-\-version\fR
306Output version information and exit.
307.SH DIAGNOSTICS
308.PP
309Exit status is zero if no child process crashed. If one or several children
310crashed, \fBzzuf\fR exits with status 1.
311.SH EXAMPLES
312.PP
313Fuzz the input of the \fBcat\fR program using default settings:
314.PP
315\fB    zzuf cat /etc/motd\fR
316.PP
317Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
318.PP
319\fB    zzuf \-s94324 \-r0.01 cat /etc/motd\fR
320.PP
321Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
322and prevent non-ASCII characters from appearing in the output:
323.PP
324\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
325.PP
326Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
327original input and excluding \fB.xml\fR files from fuzzing (because
328\fBconvert\fR will also open its own XML configuration files and we do not
329want \fBzzuf\fR to fuzz them):
330.PP
331\fB    zzuf \-E \(aq\\.xml$\(aq convert foo.jpeg \-format tga /dev/null\fR
332.PP
333Fuzz the input of VLC, using file \fBmovie.avi\fR as the original input
334and restricting fuzzing to filenames that appear on the command line
335(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
336can be read by VLC to reproduce the same behaviour without using
337\fBzzuf\fR:
338.PP
339\fB    zzuf \-c \-s87423 \-r0.01 vlc movie.avi\fR
340.br
341\fB    zzuf \-c \-s87423 \-r0.01 <movie.avi >fuzzy\-movie.avi\fR
342.br
343\fB    vlc fuzzy\-movie.avi\fR
344.PP
345Fuzz between 0.1% and 2% of MPlayer's input bits (\fB\-r0.001:0.02\fR)
346with seeds 0 to 9999 (\fB\-s0:10000\fR), preserving the AVI 4-byte header
347by restricting fuzzing to offsets after 4 (\fB\-b4\-\fR), disabling its
348standard output messages (\fB\-q\fR), launching up to five simultaneous child
349processes (\fB\-F5\fR) but waiting at least half a second between launches
350(\fB\-D0.5\fR), killing MPlayer if it takes more than one minute to
351read the file (\fB\-T60\fR) and disabling its \fBSIGSEGV\fR signal handler
352(\fB\-S\fR):
353.PP
354\fB    zzuf \-c \-r0.001:0.02 \-s0:10000 \-b4\- \-q \-F5 \-D0.5 \-T60 \-S \\\fR
355.br
356\fB      mplayer \-benchmark \-vo null \-fps 1000 movie.avi\fR
357.PP
358Create an HTML-like file that loads 200 times the same \fBhello.jpg\fR image
359and open it in Firefox\(tm in auto-increment mode (\fB\-A\fR):
360.PP
361\fB    seq \-f \(aq<img src="hello.jpg#%g">\(aq 1 200 > hello.html\fR
362.br
363      (or: \fBjot \-w \(aq<img src="hello.jpg#%d">\(aq 200 1 > hello.html\fR)
364.br
365\fB    zzuf \-A \-I \(aqhello[.]jpg\(aq \-r0.001 firefox hello.html\fR
366.PP
367Run a simple HTTP redirector on the local host using \fBsocat\fR and
368corrupt each network connection (\fB\-n\fR) in a different way (\fB\-A\fR)
369after one megabyte of data was received on it (\fB\-b1000000\-\fR):
370.PP
371\fB     zzuf \-n \-A \-b1000000\- \\\fR
372\fB       socat TCP4\-LISTEN:8080,reuseaddr,fork TCP4:192.168.1.42:80\fR
373.PP
374Browse the intarweb (\fB\-n\fR) using Firefox\(tm without fuzzing local files
375(\fB\-E.\fR) or non-HTTP connections (\fB\-p80,8010,8080\fR), preserving
376the beginning of the data sent with each HTTP response (\fB\-b4000\-\fR)
377and using another seed on each connection (\fB\-A\fR):
378.PP
379\fB    zzuf \-r 0.0001 \-n \-E. \-p80,8010,8080 \-b4000\- \-A firefox\fR
380.SH RESTRICTIONS
381.PP
382Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR,
383\fB_RLD_LIST\fB, \fBDYLD_INSERT_LIBRARIES\fR, etc.) to run its child
384processes, it will fail in the presence of any mechanism that disables
385preloading. For instance setuid root binaries will not be fuzzed when run
386as an unprivileged user.
387.PP
388For the same reasons, \fBzzuf\fR will also not work with statically linked
389binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
390where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
391.PP
392Though best efforts are made, identical behaviour for different versions of
393\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
394different operating systems and with different target programs is only
395guaranteed when the same version of \fBzzuf\fR is being used.
396.SH BUGS
397.PP
398\fBzzuf\fR probably does not behave correctly with 64-bit offsets.
399.PP
400It is not yet possible to insert or drop bytes from the input, to fuzz
401according to the file format, to swap bytes, etc. More advanced fuzzing
402methods are planned.
403.PP
404As of now, \fBzzuf\fR does not really support multithreaded applications. The
405behaviour with multithreaded applications where more than one thread does file
406descriptor operations is undefined.
407.SH NOTES
408In order to intercept file and network operations, signal handlers and memory
409allocations, \fBzzuf\fR diverts and reimplements the following functions,
410which can be private libc symbols, too:
411.TP
412Unix file descriptor handling:
413\fBopen\fR(), \fBdup\fR(), \fBdup2\fR(), \fBlseek\fR(), \fBread\fR(),
414\fBreadv\fR(), \fBpread\fR(), \fBaccept\fR(), \fBsocket\fR(), \fBrecv\fR(),
415\fBrecvfrom\fR(), \fBrecvmsg\fR(), \fBaio_read\fR(), \fBaio_return\fR(),
416\fBclose\fR()
417.TP
418Standard IO streams:
419\fBfopen\fR(), \fBfreopen\fR(), \fBfseek\fR(), \fBfseeko\fR(), \fBrewind\fR(),
420\fBfread\fR(), \fBgetc\fR(), \fBfgetc\fR(), \fBfgets\fR(), \fBungetc\fR(),
421\fBfclose\fR()
422.TP
423Memory management:
424\fBmmap\fR(), \fBmunmap\fR(), \fBmalloc\fR(), \fBcalloc\fR(), \fBvalloc\fR(),
425\fBfree\fR(), \fBmemalign\fR(), \fBposix_memalign\fR()
426.TP
427Linux-specific:
428\fBopen64\fR(), \fBlseek64\fR(), \fBmmap64\fR(), \fB_IO_getc\fR(),
429\fBgetline\fR(), \fBgetdelim\fR(), \fB__getdelim\fR(), \fBgetc_unlocked\fR(),
430\fBfgetc_unlocked\fR(), \fBfgets_unlocked\fR(), \fBfread_unlocked\fR()
431.TP
432BSD-specific:
433\fBfgetln\fR(), \fB__srefill\fR()
434.TP
435Mac OS X-specific:
436\fBmap_fd\fR()
437.TP
438Signal handling:
439\fBsignal\fR(), \fBsigaction\fR()
440.PP
441If an application manipulates file descriptors (reading data, seeking around)
442using functions that are not in that list, \fBzzuf\fR will not fuzz its
443input consistently and the results should not be trusted. You can use a tool
444such as \fBltrace(1)\fR on Linux to know the missing functions.
445.PP
446On BSD systems, such as FreeBSD or Mac OS X, \fB__srefill\fR() is enough to
447monitor all standard IO streams functions. On other systems, such as Linux,
448each function is reimplemented on a case by case basis. One important
449unimplemented function is \fBfscanf\fR(), because of its complexity. Missing
450functions will be added upon user request.
451.SH HISTORY
452.PP
453\fBzzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
454multimedia stream corrupter used to find bugs in the VLC media player.
455.SH AUTHOR
456.PP
457Copyright \(co 2002, 2007\-2008 Sam Hocevar <sam@zoy.org>.
458.PP
459\fBzzuf\fR and this manual page are free software. They come without any
460warranty, to the extent permitted by applicable law. You can redistribute
461them and/or modify them under the terms of the Do What The Fuck You Want
462To Public License, Version 2, as published by Sam Hocevar. See
463\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
464.PP
465\fBzzuf\fR's webpage can be found at \fBhttp://libcaca.zoy.org/wiki/zzuf/\fR.
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