source: zzuf/trunk/doc/zzuf.1 @ 1854 Tweet

.TH zzuf 1 "2006-12-22" "zzuf"
.SH NAME
zzuf \- multiple purpose fuzzer
.SH SYNOPSIS
\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]
.br
       [\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]
.br
       [\fB\-t\fR \fIseconds\fR] [\fB\-T\fR \fIseconds\fR] [\fB\-M\fR \fImegabytes\fR] [\fB\-b\fR \fIranges\fR]
.br
       [\fB\-P\fR \fIprotect\fR] [\fB\-R\fR \fIrefuse\fR] [\fB\-p\fR \fIpick\fR] [\fB\-I\fR \fIinclude\fR] [\fB\-E\fR \fIexclude\fR]
.br
       [\fIPROGRAM\fR [\fB\-\-\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 error channel, 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\-A\fR, \fB\-\-autoinc\fR
Increment random seed each time a new file is opened. This is only required
if one instance of the application is expected to open the same file several
times and you want to test a different seed each time.
.TP
\fB\-b\fR, \fB\-\-bytes\fR=\fIranges\fR
Restrict fuzzing to bytes whose offsets in the file are within \fIranges\fR.

Range values start at zero and are inclusive. Use dashes between range values
and commas between ranges. If the right-hand part of a range is ommited, it
means end of file. For instance, to restrict fuzzing to bytes 0, 3, 4, 5 and
all bytes after offset 31, use \(oq\fB\-r0,3-5,31-\fR\(cq.

This option is useful to preserve file headers or corrupt only a specific
portion of a file.
.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 and \fB\-T\fR flags.
.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 specifying 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. If the \fB\-x\fR flag is used, this will
also include processes that exit with a non-zero status.

This option is only relevant if the \fB\-s\fR flag is used with a range
argument.
.TP
\fB\-d\fR, \fB\-\-debug\fR
Activate the display of debug messages.
.TP
\fB\-D\fR, \fB\-\-delay\fR=\fIdelay\fR
Do not launch more than one process every \fIdelay\fR seconds. This option
should be used together with \fB\-F\fR to avoid fork bombs.
.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\-\-fuzzing\fR=\fImode\fR
Select how the input is fuzzed. Valid values for \fImode\fR are:
.RS
.TP
\fBxor\fR
randomly set and unset bits
.TP
\fBset\fR
only set bits
.TP
\fBunset\fR
only unset bits
.RE
.IP
The default value for \fImode\fR is \fBxor\fR.
.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 a range
argument. See also the \fB\-D\fR flag.
.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 \fIstandard output\fR, just print its MD5
digest to \fBzzuf\fR's standard output. The standard error channel is left
untouched.
.TP
\fB\-M\fR, \fB\-\-max-memory\fR=\fImegabytes\fR
Specify the maximum amount of memory, in megabytes, that children are allowed
to allocate. This is useful to detect infinite loops that eat up a lot of
memory. The value should set reasonably high so as not to interfer with normal
program operation.

\fBzzuf\fR uses the \fBsetrlimit\fR() call to set memory usage limitations and
relies on the operating system's ability to enforce such limitations.
.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\-\-pick\fR=\fIlist\fR
Cherry-pick the file descriptors that get fuzzed. The Nth descriptor will
really be fuzzed only if N is in \fIlist\fR.

Values start at one and ranges are inclusive. Use dashes between values and
commas between ranges. If the right-hand part of a range is ommited, it means
all subsequent file descriptors. For instance, to restrict fuzzing to the
first opened descriptor and all descriptors starting from the 10th, use
\(oq\fB\-p1,10-\fR\(cq.

Note that this option only affects file descriptors that would otherwise be
fuzzed. Even if 10 write-only descriptors are opened at the beginning of the
program, the next read-write or read-only descriptor will be the first one
considered by the \fB\-p\fR flag.
.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\ \(aq\\001\-/\(aq\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\-r0.01\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
.PD 0
.TP
\fB\-r\fR, \fB\-\-ratio\fR=\fImin:max\fR
.PD
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).

A range can also be specified. When doing so, \fBzzuf\fR will pick ratio
values from the interval. The choice is deterministic and only depends on
the interval bounds and the current seed.
.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 a range 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 a range 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 and \fB\-T\fR flags.
.TP
\fB\-T\fR, \fB\-\-max\-cpu\fR=\fIn\fR
Automatically terminate child processes that use more than \fIn\fR seconds
of CPU time.

\fBzzuf\fR uses the \fBsetrlimit\fR() call to set CPU usage limitations and
relies on the operating system's ability to enforce such limitations. If the
system sends \fBSIGXCPU\fR signals and the application catches that signal,
it will receive a \fBSIGKILL\fR signal after 5 seconds.

This is more accurate than \fB\-t\fR because the behaviour should be
independent from the system load, but it does not detect processes stuck into
infinite \fBselect\fR() calls because they use very little CPU time. See also
the \fB\-B\fR and \fB\-t\fR flags.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
Print information during the run, such as the current seed, what processes
get run, their exit status, etc.
.TP
\fB\-x\fR, \fB\-\-check\-exit\fR
Report processes that exit with a non-zero status. By default only processes
that crash due to a signal are reported.
.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 DIAGNOSTICS
.PP
Exit status is zero if no child process crashed. If one or several children
crashed, \fBzzuf\fR exits with status 1.
.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 \-s94324 \-r0.01 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 VLC, 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 VLC to reproduce the same behaviour without using
\fBzzuf\fR:
.PP
\fB    zzuf \-c \-s87423 \-r0.01 vlc movie.avi\fR
.br
\fB    zzuf \-c \-s87423 \-r0.01 <movie.avi >fuzzy\-movie.avi\fR
.br
\fB    vlc fuzzy\-movie.avi\fR
.PP
Fuzz between 0.1% and 2% of MPlayer's input bits (\fB\-r0.001:0.02\fR)
with seeds 0 to 9999 (\fB\-s0:10000\fR), preserving the AVI 4-byte header
by restricting fuzzing to offsets after 4 (\fB\-b4\-\fR), disabling its
standard output messages (\fB\-q\fR), launching up to five simultaneous child
processes (\fB\-F5\fR) but waiting at least half a second between launches
(\fB\-D0.5\fR), killing MPlayer if it takes more than one minute to
read the file (\fB\-T60\fR) and disabling its \fBSIGSEGV\fR signal handler
(\fB\-S\fR):
.PP
\fB    zzuf \-c \-r0.001:0.02 \-s0:10000 \-b4\- \-q \-F5 \-D0.5 \-T60 \-S \\\fR
.br
\fB      mplayer \-\- \-benchmark \-vo null \-fps 1000 movie.avi\fR
.PP
Create an HTML-like file that loads 200 times the same \fBhello.jpg\fR image
and open it in Firefox\(tm in auto-increment mode (\fB\-A\fR):
.PP
\fB    seq -f \(aq<img src="hello.jpg#%g">\(aq 1 200 > hello.html\fR
.br
      (or: \fBjot -w \(aq<img src="hello.jpg#%d">\(aq 200 1 > hello.html\fR)
.br
\fB    zzuf -A -I \(aqhello[.]jpg\(aq -r0.001 firefox hello.html\fR
.PP
Run a simple HTTP redirector on the local host using \fBsocat\fR and
corrupt each network connection (\fB\-n\fR) in a different way (\fB\-A\fR)
after one megabyte of data was received on it (\fB\-b1000000\-\fR):
.PP
\fB     zzuf \-n \-A \-b1000000\- \\\fR
\fB       socat TCP4-LISTEN:8080,reuseaddr,fork TCP4:192.168.1.42:80\fR
.SH RESTRICTIONS
.PP
Due to \fBzzuf\fR using shared object preloading (\fBLD_PRELOAD\fR,
\fB_RLD_LIST\fB, \fBDYLD_INSERT_LIBRARIES\fR, etc.) 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, signal handlers and memory
allocations, \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(), \fBreadv\fR(), \fBpread\fR(),
\fBaccept\fR(), \fBsocket\fR(), \fBrecv\fR(), \fBrecvfrom\fR(), \fBrecvmsg\fR(),
\fBaio_read\fR(), \fBaio_return\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
Memory management:
\fBmmap\fR(), \fBmunmap\fR(), \fBmalloc\fR(), \fBcalloc\fR(), \fBvalloc\fR(),
\fBfree\fR(), \fBmemalign\fR(), \fBposix_memalign\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
Mac OS X-specific:
\fBmap_fd\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 VLC 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.