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Raku bindings for radamsa, a general purpose fuzzer

When you have to start fuzzing RIGHT NOW, radamsa is hard to beat. However, hidden under a mountain of parentheses in the radamsa git repo is real black magic, libradamsa, which is what these bindings are actually for. This is multithreaded fuzzing on easy mode.


zef install Radamsa

The build fetches radamsa source from and builds It'll take a minute.

Using it

use Radamsa;

There is one class, radamsa. You'll need to initialize it with good input(s).

There are three convenience constructors:

new(Str $s)

seeds radamsa with a single string

my $r ="fuzz me");

new(IO::Path $p)

If $p is a file, then $p's contents are the seed. If $p is a directory, radamsa adds every file and recurses through subdirectories. Use this to fuzz file formats.

new(buf8 @inputs)

Inputs are stored as an array of buf8s, so this sets it directly.

my $r =;

Optional parameters

:maxoutsz This sets a byte limit for the length of radamsa's output. If you don't specify it, radamsa will set it to the length of the longest input provided to the constructor.


Radamsa tries to avoid idle workers by keeping a minimum number of ouputs in the queue. More detail is provided below. You can ignore this.

Changing inputs

You can modify the inputs at runtime if you'd like to guide the fuzzer. The array of inputs is directly accessible through $r.inputs (an array of buf8s) or through addinput(Blob), addinput(Str), or addinput(IO::Path).

Radamsa will randomly choose one input for each ouput it generates, so choose your inputs wisely.

Getting output

All results are buf8 because there's no telling what you'll get.


Returns a single item of output.

> for ^10 { say $r.gen1.decode }
fuzzfzzfuzzfuzz mefuzz me mefuzme
fuzz me mefuzz me
fuzz me mefuzz me mefuzz me
  mefuzz me
fuzz mefuzz me

fuz me
Malformed UTF-8 at line 1 col 1
  in block <unit> at <unknown file> line 1

Getting a lot of ouput

The radamsa class is a Raku Channel, so you can call .receive on it. The queue will be empty until you initialize it with .startchannel. This starts a worker thread that tries to keep at least $.minqsz items available on the channel. Radamsa will naively increase its minqsz whenever the queue gets too short. It's not PID control, but it works for most usecases. You can outrun libradamsa with very quick tests. If that happens, ignore it or use fewer threads; libradamsa isn't thread safe.

Here is an example that writes to some temp files.

use Radamsa;
my $r ="go fuzz your software", :maxoutsz(100), :minqsz(100));
my $keepgoing = True;
my @workers;
for ^10 {                                           # starting 10 threads
    my $fh = ('/tmp/libradtest'~$_);
        start {
            while ?$keepgoing {
                my $b = $r.receive;
                $b.append(0x0a);                    # newline to make it somewhat readable
sleep 5;
$keepgoing = False;
await @workers;

and some of it's output

> head -n 5 /tmp/libradtest*
==> /tmp/libradtest0 <==
go fuzó   z your software
go fuzzˑ ʵyour software
â€ó  ƒ‡go óʶ  §fuzz your sr sofï¿¿twaâ §ró  še
go fuzz your softwó  ³are
go fuzz your softwarego fuzz your só  ›oftware

==> /tmp/libradtest1 <==
go fuzz your ÷dLsoftware
g„1•259ó  €o fó €»uzzó  Žó  «ó  ´ your só ó  „ žoâ ¥ftware
go fuzz yoâ€ó €²‡ur sof twaró €¢ó € e
go fuzz y só  ›o fuzz your software
go fuzz your softward

==> /tmp/libradtest2 <==
go fuzó  »z your software
go fuzz softwarego fuzz your software
ó  ­go fuzz your software
go fuzz your softwarego fuzz your softwarego fuzz your softwarego fuzz your softwaregoï¼  fuzz your
go fuzz xour softw`re

==> /tmp/libradtest3 <==
go fuzz your ‬software
go fuzz your softwarego fuzz your só  ›oftwarer software
go fuzzó  … your software
go fu fuzz youzz your softwarego fuzz your só  ›oftwarego fuzz your só  ›oftware
go ftware

==> /tmp/libradtest4 <==
à¿­go fuó  «zz yougo fuzz fuô 	¿¾zz your sÂ·ó  ›oftware
go fuzz your software
go fuzz yoó  ”ur software
go fuzz your sofó €¼tware
go fuzz your softwarego fuz

==> /tmp/libradtest5 <==
go fuzz your softwarego fuzz your softwarego fuzz your softwarego fuzz your softwarego fuzz your sof
go fuzz  your só  ¿oftwaró·  ˜e
go fuzz your sof tware
âó  »€ó  •á Žóó  ” €½„óשּׁ ó ó  ’ Ÿgo fuzz yo fuzz your só  ›oftwarer software
go ftó  ›ware

==> /tmp/libradtest6 <==
go fuzó  ó  ©•z your software
go fuzz yoó €¹ur software
go fuzz your softwarego fuzz your só  ›oftware
goó  ur software
go your softwaretó  šsoftó  ‘ó  šsoftó  šsoftó  šsoftó  šsoftware

==> /tmp/libradtest7 <==
go fuz z your so fuzz your software
go Ê°f�þÿuzz your so‮ftâ §warego fuó  ³zz y󠀯our só  ›ó  ‰oftware
go fuzz your software
go fuzz your software
ó  šsoftó  ftware

==> /tmp/libradtest8 <==
go fuzz yo ur ó  ™software
go fuzz your softwarego fuzz your software
go f󠀤uzz yó  †our software
go fuzz your softwarez your software
go fuzz your softó  ›ware

==> /tmp/libradtest9 <==
go fuzz you
go fuzz your softwarego fuzzgo fuzz your softwarego fuzz your só  ›oftware
go fuzz your softwaregoe
go fuzz your softwarego fuzz your só  ›oftware
go fuï· zz your ó  šsofuzz ougo ‪fuzz your softwarego fuzz your softwarego fuzz your só ó €± ›oftw


Raku bindings for radamsa, a magical general purpose fuzzer






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