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SubjectRe: [PATCH 14/16] X.509: Add an ASN.1 decoder
Date
David Howells <dhowells@redhat.com> wrote:

> > has it been fuzz tested extensively ?

Also, here's a generator of random binary ASN.1. I think it should mostly
produce valid X.509, but invalid ASN.1 is okay too.

Run with something like:

while :; do ./asn1random.pl | keyctl padd asymmetric vlad @s; done

David
---
#!/usr/bin/perl -w
use strict;

my $depth = 0;
my $maxdepth = 12;
my $num_elements = 0;
my $total_elements = 30 + int(rand(400));

print STDERR "SEED: ", srand(), "\n";

###############################################################################
#
# Generate a header
#
###############################################################################
sub emit_asn1_hdr($$)
{
my ($tag, $len) = @_;
my $output = "";
my $l;

if ($len < 0x80) {
$l = $len;
} elsif ($len <= 0xff) {
$l = 0x81;
} elsif ($len <= 0xffff) {
$l = 0x82;
} elsif ($len <= 0xffffff) {
$l = 0x83;
} else {
$l = 0x84;
}

$output .= pack("CC", $tag == -1 ? int(rand(255)) & ~0x20 : $tag, $l);
if ($len < 0x80) {
} elsif ($len <= 0xff) {
$output .= pack("C", $len);
} elsif ($len <= 0xffff) {
$output .= pack("n", $len);
} elsif ($len <= 0xffffff) {
$output .= pack("Cn", $len >> 16, $len & 0xffff);
} else {
$output .= pack("N", $len);
}

return $output;
}

###############################################################################
#
# Generate a random primitive
#
###############################################################################
sub emit_asn1_prim($)
{
my ($tag) = @_;
my $output;
my $len = int(rand(255));

$len = 4; #####################

$tag = int(rand(255)) & ~0x20
if ($tag == -1);

$output = emit_asn1_hdr($tag, $len);

my $i = $len;
while ($i > 16) {
$output .= "abcdefghijklmnop";
$i -= 16;
}

$output .= substr("abcdefghijklmnop", 0, $i);
return $output;
}

###############################################################################
#
# Generate a random construct
#
###############################################################################
sub emit_asn1_cons($);
sub emit_asn1_cons($)
{
my $output = "";
my $count = int(rand(20));
my ($tag) = @_;

if ($depth >= $maxdepth) {
return emit_asn1_prim($tag);
}

if ($tag == -1) {
$tag = int(rand(255)) & ~0x20;
if ($tag < 0x40 && $tag != 0x11) {
$tag = 0x10;
}
$tag |= 0x20;
}

$depth++;
while ($count > 0) {
if (int(rand(4 + $depth)) == 1) {
$output .= emit_asn1_cons(-1);
} else {
$output .= emit_asn1_prim(-1);
}
$count--;
}
$depth--;

return emit_asn1_hdr($tag, length($output)) . $output;
}

print emit_asn1_cons(-1);


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