source: zzuf/trunk/doc/zzuf.1 @ 1623 Tweet

.TH zzuf 1 "2006-12-22" "zzuf"
.SH NAME
zzuf \- multiple purpose fuzzer
.SH SYNOPSIS
\fBzzuf\fR [\fB\-cdiMnqS\fR] [\fB\-r\fR \fIratio\fR] [\fB\-s\fR \fIseed\fR | \fB\-s\fR \fIstart:stop\fR]
.br
                [\fB\-F\fR \fIforks\fR] [\fB\-C\fR \fIcrashes\fR] [\fB\-B\fR \fIbytes\fR] [\fB\-T\fR \fIseconds\fR]
.br
                [\fB\-P\fR \fIprotect\fR] [\fB\-R\fR \fIrefuse\fR]
.br
                [\fB\-I\fR \fIinclude\fR] [\fB\-E\fR \fIexclude\fR] [\fIPROGRAM\fR [\fIARGS\fR]...]
.br
\fBzzuf \-h\fR | \fB\-\-help\fR
.br
\fBzzuf \-v\fR | \fB\-\-version\fR
.SH DESCRIPTION
.PP
\fBZzuf\fR is a transparent application input fuzzer. It works by intercepting
file and network operations and changing random bits in the program's input.
\fBZzuf\fR's behaviour is deterministic, making it easy to reproduce bugs.
.SH USAGE
.PP
\fBZzuf\fR will run an application specified on its command line, one or
several times, with optional arguments, and will report the application's
relevant behaviour on the standard output, eg:
.PP
\fB    zzuf cat /dev/zero\fR
.PP
If you want to specify flags for your application, put a \(oq\fB\-\-\fR\(cq
marker before them on the command line (otherwise \fBzzuf\fR will try to
interpret them as arguments for itself), eg:
.PP
\fB    zzuf \-B 1000 cat \-\- \-v /dev/zero\fR
.PP
When no program is specified, \fBzzuf\fR simply fuzzes the standard input, as
if the \fBcat\fR utility had been called:
.PP
\fB    zzuf < /dev/zero\fR
.SH OPTIONS
.TP
\fB\-B\fR, \fB\-\-max\-bytes\fR=\fIn\fR
Automatically terminate child processes that output more than \fIn\fR bytes
on the standard output and standard error channels. This is useful to detect
infinite loops. See also the \fB\-T\fR flag.
.TP
\fB\-c\fR, \fB\-\-cmdline\fR
Only fuzz files whose name is specified in the target application's command
line. This is mostly a shortcut to avoid specifiying twice the argument:

\fB    zzuf \-c cat file.txt\fR

has the same effect as

\fB    zzuf \-I \(aq^file\\.txt$\(aq cat file.txt\fR

See the \fB\-I\fR flag for more information on restricting fuzzing to
specific files.
.TP
\fB\-C\fR, \fB\-\-max\-crashes\fR=\fIn\fR
Stop forking when at least \fIn\fR children have crashed. The default value
is 1, meaning \fBzzuf\fR will stop as soon as one child has crashed. A process
is considered to have crashed if any signal (such as, but not limited to,
\fBSIGSEGV\fR) caused it to exit.

This option is only relevant if the \fB\-s\fR flag is used with an interval
argument.
.TP
\fB\-d\fR, \fB\-\-debug\fR
Activate the display of debug messages.
.TP
\fB\-E\fR, \fB\-\-exclude\fR=\fIregex\fR
Do not fuzz files whose name matches the \fIregex\fR regular expression. This
option supersedes anything that is specified by the \fB\-I\fR flag. Use this
for instance if you are unsure of what files your application is going to read
and do not want it to fuzz files in the \fB/etc\fR directory.

Multiple \fB\-E\fR flags can be specified, in which case files matching any one
of the regular expressions will be ignored.
.TP
\fB\-F\fR, \fB\-\-max\-forks\fR=\fIforks\fR
Specify the number of simultaneous children that can be run.

This option is only relevant if the \fB\-s\fR flag is used with an interval
argument.
.TP
\fB\-i\fR, \fB\-\-stdin\fR
Fuzz the application's standard input. By default \fBzzuf\fR only fuzzes files.
.TP
\fB\-I\fR, \fB\-\-include\fR=\fIregex\fR
Only fuzz files whose name matches the \fIregex\fR regular expression. Use
this for instance if your application reads configuration files at startup
and you only want specific files to be fuzzed.

Multiple \fB\-I\fR flags can be specified, in which case files matching any one
of the regular expressions will be fuzzed. See also the \fB\-c\fR flag.
.TP
\fB\-M\fR, \fB\-\-md5\fR
Instead of displaying the program's output, just print the MD5 digest of that
output.
.TP
\fB\-n\fR, \fB\-\-network\fR
Fuzz the application's network input. By default \fBzzuf\fR only fuzzes files.
.TP
\fB\-P\fR, \fB\-\-protect\fR=\fIlist\fR
Protect a list of characters so that if they appear in input data that would
normally be fuzzed, they are left unmodified instead.

Characters in \fIlist\fR can be expressed verbatim or through escape sequences.
The sequences interpreted by \fBzzuf\fR are:
.RS
.TP
\fB\\n\fR
new line
.TP
\fB\\r\fR
return
.TP
\fB\\t\fR
tabulation
.TP
\fB\\\fR\fINNN\fR
the byte whose octal value is \fINNN\fR
.TP
\fB\\x\fR\fINN\fR
the byte whose hexadecimal value is \fINN\fR
.TP
\fB\\\\\fR
backslash (\(oq\\\(cq)
.RE
.IP
You can use \(oq\fB\-\fR\(cq to specify ranges. For instance, to protect all
bytes from \(oq\\001\(cq to \(oq/\(cq, use \(oq\fB\-P\ \(dq\\001\-/\(dq\fR\(cq.

The statistical outcome of this option should not be overlooked: if characters
are protected, the effect of the \(oq\fB\-r\fR\(cq flag will vary depending
on the data being fuzzed. For instance, asking to fuzz 1% of input bits
(\fB\-r\ 0.01\fR) and to protect lowercase characters (\fB\-P\ a\-z\fR) will
result in an actual average fuzzing ratio of 0.9% with truly random data,
0.3% with random ASCII data and 0.2% with standard English text.

See also the \fB\-R\fR flag.
.TP
\fB\-q\fR, \fB\-\-quiet\fR
Hide the output of the fuzzed application. This is useful if the application
is very verbose but only its exit code or signaled status is really useful to
you.
.TP
\fB\-r\fR, \fB\-\-ratio\fR=\fIratio\fR
Specify the proportion of bits that will be randomly fuzzed. A value of 0
will not fuzz anything. A value of 0.05 will fuzz 5% of the open files'
bits. A value of 1.0 or more will fuzz all the bytes, theoretically making
the input files undiscernible from random data. The default fuzzing ratio
is 0.004 (fuzz 0.4% of the files' bits).
.TP
\fB\-R\fR, \fB\-\-refuse\fR=\fIlist\fR
Refuse a list of characters by not fuzzing bytes that would otherwise be
changed to a character that is in \fIlist\fR. If the original byte is already
in \fIlist\fR, it is left unchanged.

See the \fB\-P\fR option for a description of \fIlist\fR.
.TP
\fB\-s\fR, \fB\-\-seed\fR=\fIseed\fR
.PD 0
.TP
\fB\-s\fR, \fB\-\-seed\fR=\fIstart:stop\fR
.PD
Specify the random seed to use for fuzzing, or an interval of random seeds.
Running \fBzzuf\fR twice with the same random seed will fuzz the files exactly
the same way, even with a different target application. The purpose of this is
to use simple utilities such as \fBcat\fR or \fBcp\fR to generate a file that
causes the target application to crash.

If an interval is specified, \fBzzuf\fR will run the application several times,
each time with a different seed, and report the behaviour of each run.
.TP
\fB\-S\fR, \fB\-\-signal\fR
Prevent children from installing signal handlers for signals that usually
cause coredumps. These signals are \fBSIGABRT\fR, \fBSIGFPE\fR, \fBSIGILL\fR,
\fBSIGQUIT\fR, \fBSIGSEGV\fR, \fBSIGTRAP\fR and, if available on the running
platform, \fBSIGSYS\fR, \fBSIGEMT\fR, \fBSIGBUS\fR, \fBSIGXCPU\fR and
\fBSIGXFSZ\fR. Instead of calling the signal handler, the application will
simply crash. If you do not want core dumps, you should set appropriate limits
with the \fBlimit coredumpsize\fR command. See your shell's documentation on
how to set such limits.
.TP
\fB\-T\fR, \fB\-\-max\-time\fR=\fIn\fR
Automatically terminate child processes that run for more than \fIn\fR
seconds. This is useful to detect infinite loops or processes stuck in other
situations. See also the \fB\-B\fR flag.
.TP
\fB\-h\fR, \fB\-\-help\fR
Display a short help message and exit.
.TP
\fB\-v\fR, \fB\-\-version\fR
Output version information and exit.
.SH EXAMPLES
.PP
Fuzz the input of the \fBcat\fR program using default settings:
.PP
\fB    zzuf cat /etc/motd\fR
.PP
Fuzz 1% of the input bits of the \fBcat\fR program using seed 94324:
.PP
\fB    zzuf \-s 94324 \-r 0.01 cat /etc/motd\fR
.PP
Fuzz the input of the \fBcat\fR program but do not fuzz newline characters
and prevent non-ASCII characters from appearing in the output:
.PP
\fB    zzuf \-P \(aq\\n\(aq \-R \(aq\\x00\-\\x1f\\x7f\-\\xff\(aq cat /etc/motd\fR
.PP
Fuzz the input of the \fBconvert\fR program, using file \fBfoo.jpeg\fR as the
original input and excluding \fB.xml\fR files from fuzzing (because
\fBconvert\fR will also open its own XML configuration files and we do not
want \fBzzuf\fR to fuzz them):
.PP
\fB    zzuf \-E \(aq\\.xml$\(aq convert \-\- foo.jpeg \-format tga /dev/null\fR
.PP
Fuzz the input of \fBVLC\fR, using file \fBmovie.avi\fR as the original input
and restricting fuzzing to filenames that appear on the command line
(\fB\-c\fR), then generate \fBfuzzy\-movie.avi\fR which is a file that
can be read by \fBVLC\fR to reproduce the same behaviour without using
\fBzzuf\fR:
.PP
\fB    zzuf \-c \-s 87423 \-r 0.01 vlc movie.avi\fR
\fB    zzuf \-c \-s 87423 \-r 0.01 cp movie.avi fuzzy\-movie.avi\fR
\fB    vlc fuzzy\-movie.avi\fR
.PP
Fuzz 2% of \fBMPlayer\fR's input bits (\fB\-r\ 0.02\fR) with seeds 0 to 9999
(\fB\-s\ 0:10000\fR), disabling its standard output messages (\fB\-q\fR),
launching up to three simultaneous child processes (\fB\-F\ 3\fR), killing
\fBMPlayer\fR if it takes more than one minute to read the file (\fB\-T\ 60\fR)
and disabling its \fBSIGSEGV\fR signal handler (\fB\-S\fR):
.PP
\fB    zzuf \-c \-r 0.02 \-q \-s 0:10000 \-F 3 \-T 60 \-S \\\fR
\fB      mplayer \-\- \-benchmark \-vo null \-fps 1000 movie.avi\fR
.SH RESTRICTIONS
.PP
Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR on most
Unix systems, \fBDYLD_INSERT_LIBRARIES\fR on Mac OS X) to run its child
processes, it will fail in the presence of any mechanism that disables
preloading. For instance setuid root binaries will not be fuzzed when run
as an unprivileged user.
.PP
For the same reasons, \fBzzuf\fR will also not work with statically linked
binaries. Bear this in mind when using \fBzzuf\fR on the OpenBSD platform,
where \fBcat\fR, \fBcp\fR and \fBdd\fR are static binaries.
.PP
Though best efforts are made, identical behaviour for different versions of
\fBzzuf\fR is not guaranteed. The reproducibility for subsequent calls on
different operating systems and with different target programs is only
guaranteed when the same version of \fBzzuf\fR is being used.
.SH BUGS
.PP
\fBZzuf\fR probably does not behave correctly with 64-bit offsets.
.PP
It is not yet possible to insert or drop bytes from the input, to fuzz
according to the file format, to swap bytes, etc. More advanced fuzzing
methods are planned.
.PP
As of now, \fBzzuf\fR does not really support multithreaded applications. The
behaviour with multithreaded applications where more than one thread does file
descriptor operations is undefined.
.SH NOTES
In order to intercept file and network operations and signal handlers,
\fBzzuf\fR diverts and reimplements the following functions, which can
be private libc symbols, too:
.TP
Unix file descriptor handling:
\fBopen\fR(), \fBlseek\fR(), \fBread\fR(), \fBaccept\fR(), \fBsocket\fR(),
\fBmmap\fR(), \fBmunmap\fR(), \fBclose\fR()
.TP
Standard IO streams:
\fBfopen\fR(), \fBfreopen\fR(), \fBfseek\fR(), \fBfseeko\fR(), \fBrewind\fR(),
\fBfread\fR(), \fBgetc\fR(), \fBfgetc\fR(), \fBfgets\fR(), \fBungetc\fR(),
\fBfclose\fR()
.TP
Linux-specific:
\fBopen64\fR(), \fBlseek64\fR(), \fBmmap64\fR(), \fB_IO_getc\fR(),
\fBgetline\fR(), \fBgetdelim\fR(), \fB__getdelim\fR()
.TP
BSD-specific:
\fBfgetln\fR(), \fB__srefill\fR()
.TP
Signal handling:
\fBsignal\fR(), \fBsigaction\fR()
.PP
If an application manipulates file descriptors (reading data, seeking around)
using functions that are not in that list, \fBzzuf\fR will not fuzz its
input consistently and the results should not be trusted. You can use a tool
such as \fBltrace(1)\fR on Linux to know the missing functions.
.PP
On BSD systems, such as FreeBSD or Mac OS X, \fB__srefill\fR() is enough to
monitor all standard IO streams functions. On other systems, such as Linux,
each function is reimplemented on a case by case basis. One important
unimplemented function is \fBfscanf\fR(), because of its complexity. Missing
functions will be added upon user request.
.SH HISTORY
.PP
\fBZzuf\fR started its life in 2002 as the \fBstreamfucker\fR tool, a small
multimedia stream corrupter used to find bugs in the \fBVLC\fR media player.
.SH AUTHOR
.PP
Copyright \(co 2002, 2007 Sam Hocevar <sam@zoy.org>.
.PP
\fBZzuf\fR and this manual page are free software. They come without any
warranty, to the extent permitted by applicable law. You can redistribute
them and/or modify them under the terms of the Do What The Fuck You Want
To Public License, Version 2, as published by Sam Hocevar. See
\fBhttp://sam.zoy.org/wtfpl/COPYING\fR for more details.
.PP
\fBZzuf\fR's webpage can be found at \fBhttp://sam.zoy.org/zzuf/\fR.