# Copyright (c) 2003-2009 Graham Barr, Djamel Boudjerda, Paul Connolly, Julian
# Onions, Nexor and Yann Kerherve.
# All rights reserved. This program is free software; you can redistribute
# it and/or modify it under the same terms as Perl itself.
# See http://www.ietf.org/rfc/rfc2831.txt for details
package Authen::SASL::Perl::DIGEST_MD5;
use strict;
use vars qw($VERSION @ISA $CNONCE $NONCE);
use Digest::MD5 qw(md5_hex md5);
use Digest::HMAC_MD5 qw(hmac_md5);
# TODO: complete qop support in server, should be configurable
$VERSION = "2.14";
@ISA = qw(Authen::SASL::Perl);
my %secflags = (
noplaintext => 1,
noanonymous => 1,
);
# some have to be quoted - some don't - sigh!
my (%cqdval, %sqdval);
@cqdval{qw(
username authzid realm nonce cnonce digest-uri
)} = ();
## ...and server behaves different than client - double sigh!
@sqdval{keys %cqdval, qw(qop cipher)} = ();
# username authzid realm nonce cnonce digest-uri qop cipher
#)} = ();
my %multi;
@{$multi{server}}{qw(realm auth-param)} = ();
@{$multi{client}}{qw()} = ();
my @server_required = qw(algorithm nonce);
my @client_required = qw(username nonce cnonce nc qop response);
# available ciphers
my @ourciphers = (
{
name => 'rc4',
ssf => 128,
bs => 1,
ks => 16,
pkg => 'Crypt::RC4',
key => sub { $_[0] },
iv => sub {},
fixup => sub {
# retrofit the Crypt::RC4 module with standard subs
*Crypt::RC4::encrypt = *Crypt::RC4::decrypt =
sub { goto &Crypt::RC4::RC4; };
*Crypt::RC4::keysize = sub {128};
*Crypt::RC4::blocksize = sub {1};
}
},
{
name => '3des',
ssf => 112,
bs => 8,
ks => 16,
pkg => 'Crypt::DES3',
key => sub {
pack('B8' x 16,
map { $_ . '0' }
map { unpack('a7' x 16, $_); }
unpack('B*', substr($_[0], 0, 14)) );
},
iv => sub { substr($_[0], -8, 8) },
},
{
name => 'des',
ssf => 56,
bs => 8,
ks => 16,
pkg => 'Crypt::DES',
key => sub {
pack('B8' x 8,
map { $_ . '0' }
map { unpack('a7' x 8, $_); }
unpack('B*',substr($_[0], 0, 7)) );
},
iv => sub { substr($_[0], -8, 8) },
},
{
name => 'rc4-56',
ssf => 56,
bs => 1,
ks => 7,
pkg => 'Crypt::RC4',
key => sub { $_[0] },
iv => sub {},
fixup => sub {
*Crypt::RC4::encrypt = *Crypt::RC4::decrypt =
sub { goto &Crypt::RC4::RC4; };
*Crypt::RC4::keysize = sub {56};
*Crypt::RC4::blocksize = sub {1};
}
},
{
name => 'rc4-40',
ssf => 40,
bs => 1,
ks => 5,
pkg => 'Crypt::RC4',
key => sub { $_[0] },
iv => sub {},
fixup => sub {
*Crypt::RC4::encrypt = *Crypt::RC4::decrypt =
sub { goto &Crypt::RC4::RC4; };
*Crypt::RC4::keysize = sub {40};
*Crypt::RC4::blocksize = sub {1};
}
},
);
## The system we are on, might not be able to crypt the stream
our $NO_CRYPT_AVAILABLE = 1;
for (@ourciphers) {
eval "require $_->{pkg}";
unless ($@) {
$NO_CRYPT_AVAILABLE = 0;
last;
}
}
sub _order { 3 }
sub _secflags {
shift;
scalar grep { $secflags{$_} } @_;
}
sub mechanism { 'DIGEST-MD5' }
sub _init {
my ($pkg, $self) = @_;
bless $self, $pkg;
# set default security properties
$self->property('minssf', 0);
$self->property('maxssf', int 2**31 - 1); # XXX - arbitrary "high" value
$self->property('maxbuf', 0xFFFFFF); # maximum supported by GSSAPI mech
$self->property('externalssf', 0);
$self;
}
sub _init_server {
my $server = shift;
my $options = shift || {};
if (!ref $options or ref $options ne 'HASH') {
warn "options for DIGEST_MD5 should be a hashref";
$options = {};
}
## new server, means new nonce_counts
$server->{nonce_counts} = {};
## determine supported qop
my @qop = ('auth');
push @qop, 'auth-int' unless $options->{no_integrity};
push @qop, 'auth-conf' unless $options->{no_integrity}
or $options->{no_confidentiality}
or $NO_CRYPT_AVAILABLE;
$server->{supported_qop} = { map { $_ => 1 } @qop };
}
sub init_sec_layer {
my $self = shift;
$self->{cipher} = undef;
$self->{khc} = undef;
$self->{khs} = undef;
$self->{sndseqnum} = 0;
$self->{rcvseqnum} = 0;
# reset properties for new session
$self->property(maxout => undef);
$self->property(ssf => undef);
}
# no initial value passed to the server
sub client_start {
my $self = shift;
$self->{need_step} = 1;
$self->{error} = undef;
$self->{state} = 0;
$self->init_sec_layer;
'';
}
sub server_start {
my $self = shift;
my $challenge = shift;
my $cb = shift || sub {};
$self->{need_step} = 1;
$self->{error} = undef;
$self->{nonce} = md5_hex($NONCE || join (":", $$, time, rand));
$self->init_sec_layer;
my $qop = [ sort keys %{$self->{supported_qop}} ];
## get the realm using callbacks but default to the host specified
## during the instanciation of the SASL object
my $realm = $self->_call('realm');
$realm ||= $self->host;
my %response = (
nonce => $self->{nonce},
charset => 'utf-8',
algorithm => 'md5-sess',
realm => $realm,
maxbuf => $self->property('maxbuf'),
## IN DRAFT ONLY:
# If this directive is present multiple times the client MUST treat
# it as if it received a single qop directive containing a comma
# separated value from all instances. I.e.,
# 'qop="auth",qop="auth-int"' is the same as 'qop="auth,auth-int"
'qop' => $qop,
'cipher' => [ map { $_->{name} } @ourciphers ],
);
my $final_response = _response(\%response);
$cb->($final_response);
return;
}
sub client_step { # $self, $server_sasl_credentials
my ($self, $challenge) = @_;
$self->{server_params} = \my %sparams;
# Parse response parameters
$self->_parse_challenge(\$challenge, server => $self->{server_params})
or return $self->set_error("Bad challenge: '$challenge'");
if ($self->{state} == 1) {
# check server's `rspauth' response
return $self->set_error("Server did not send rspauth in step 2")
unless ($sparams{rspauth});
return $self->set_error("Invalid rspauth in step 2")
unless ($self->{rspauth} eq $sparams{rspauth});
# all is well
$self->set_success;
return '';
}
# check required fields in server challenge
if (my @missing = grep { !exists $sparams{$_} } @server_required) {
return $self->set_error("Server did not provide required field(s): @missing")
}
my %response = (
nonce => $sparams{'nonce'},
cnonce => md5_hex($CNONCE || join (":", $$, time, rand)),
'digest-uri' => $self->service . '/' . $self->host,
# calc how often the server nonce has been seen; server expects "00000001"
nc => sprintf("%08d", ++$self->{nonce_counts}{$sparams{'nonce'}}),
charset => $sparams{'charset'},
);
return $self->set_error("Server qop too weak (qop = $sparams{'qop'})")
unless ($self->_client_layer(\%sparams,\%response));
# let caller-provided fields override defaults: authorization ID, service name, realm
my $s_realm = $sparams{realm} || [];
my $realm = $self->_call('realm', @$s_realm);
unless (defined $realm) {
# If the user does not pick a realm, use the first from the server
$realm = $s_realm->[0];
}
if (defined $realm) {
$response{realm} = $realm;
}
my $authzid = $self->_call('authname');
if (defined $authzid) {
$response{authzid} = $authzid;
}
my $serv_name = $self->_call('serv');
if (defined $serv_name) {
$response{'digest-uri'} .= '/' . $serv_name;
}
my $user = $self->_call('user');
return $self->set_error("Username is required")
unless defined $user;
$response{username} = $user;
my $password = $self->_call('pass');
return $self->set_error("Password is required")
unless defined $password;
$self->property('maxout', $sparams{maxbuf} || 65536);
# Generate the response value
$self->{state} = 1;
my ($response, $rspauth)
= $self->_compute_digests_and_set_keys($password, \%response);
$response{response} = $response;
$self->{rspauth} = $rspauth;
# finally, return our response token
return _response(\%response, "is_client");
}
sub _compute_digests_and_set_keys {
my $self = shift;
my $password = shift;
my $params = shift;
if (defined $params->{realm} and ref $params->{realm} eq 'ARRAY') {
$params->{realm} = $params->{realm}[0];
}
my $realm = $params->{realm};
$realm = "" unless defined $realm;
my $A1 = join (":",
md5(join (":", $params->{username}, $realm, $password)),
@$params{defined($params->{authzid})
? qw(nonce cnonce authzid)
: qw(nonce cnonce)
}
);
# pre-compute MD5(A1) and HEX(MD5(A1)); these are used multiple times below
my $hdA1 = unpack("H*", (my $dA1 = md5($A1)) );
# derive keys for layer encryption / integrity
$self->{kic} = md5($dA1,
'Digest session key to client-to-server signing key magic constant');
$self->{kis} = md5($dA1,
'Digest session key to server-to-client signing key magic constant');
if (my $cipher = $self->{cipher}) {
&{ $cipher->{fixup} || sub{} };
# compute keys for encryption
my $ks = $cipher->{ks};
$self->{kcc} = md5(substr($dA1,0,$ks),
'Digest H(A1) to client-to-server sealing key magic constant');
$self->{kcs} = md5(substr($dA1,0,$ks),
'Digest H(A1) to server-to-client sealing key magic constant');
# get an encryption and decryption handle for the chosen cipher
$self->{khc} = $cipher->{pkg}->new($cipher->{key}->($self->{kcc}));
$self->{khs} = $cipher->{pkg}->new($cipher->{key}->($self->{kcs}));
# initialize IVs
$self->{ivc} = $cipher->{iv}->($self->{kcc});
$self->{ivs} = $cipher->{iv}->($self->{kcs});
}
my $A2 = "AUTHENTICATE:" . $params->{'digest-uri'};
$A2 .= ":00000000000000000000000000000000" if ($params->{qop} ne 'auth');
my $response = md5_hex(
join (":", $hdA1, @$params{qw(nonce nc cnonce qop)}, md5_hex($A2))
);
# calculate server `rspauth' response, so we can check in step 2
# the only difference here is in the A2 string which from which
# `AUTHENTICATE' is omitted in the calculation of `rspauth'
$A2 = ":" . $params->{'digest-uri'};
$A2 .= ":00000000000000000000000000000000" if ($params->{qop} ne 'auth');
my $rspauth = md5_hex(
join (":", $hdA1, @$params{qw(nonce nc cnonce qop)}, md5_hex($A2))
);
return ($response, $rspauth);
}
sub server_step {
my $self = shift;
my $challenge = shift;
my $cb = shift || sub {};
$self->{client_params} = \my %cparams;
unless ( $self->_parse_challenge(\$challenge, client => $self->{client_params}) ) {
$self->set_error("Bad challenge: '$challenge'");
return $cb->();
}
# check required fields in server challenge
if (my @missing = grep { !exists $cparams{$_} } @client_required) {
$self->set_error("Client did not provide required field(s): @missing");
return $cb->();
}
my $count = hex ($cparams{'nc'} || 0);
unless ($count == ++$self->{nonce_counts}{$cparams{nonce}}) {
$self->set_error("nonce-count doesn't match: $count");
return $cb->();
}
my $qop = $cparams{'qop'} || "auth";
unless ($self->is_qop_supported($qop)) {
$self->set_error("Client qop not supported (qop = '$qop')");
return $cb->();
}
my $username = $cparams{'username'};
unless ($username) {
$self->set_error("Client didn't provide a username");
return $cb->();
}
# "The authzid MUST NOT be an empty string."
if (exists $cparams{authzid} && $cparams{authzid} eq '') {
$self->set_error("authzid cannot be empty");
return $cb->();
}
my $authzid = $cparams{authzid};
# digest-uri: "Servers SHOULD check that the supplied value is correct.
# This will detect accidental connection to the incorrect server, as well as
# some redirection attacks"
my $digest_uri = $cparams{'digest-uri'};
my ($cservice, $chost, $cservname) = split '/', $digest_uri, 3;
if ($cservice ne $self->service or $chost ne $self->host) {
# XXX deal with serv_name
$self->set_error("Incorrect digest-uri");
return $cb->();
}
unless (defined $self->callback('getsecret')) {
$self->set_error("a getsecret callback MUST be defined");
$cb->();
return;
}
my $realm = $self->{client_params}->{'realm'};
my $response_check = sub {
my $password = shift;
return $self->set_error("Cannot get the passord for $username")
unless defined $password;
## configure the security layer
$self->_server_layer($qop)
or return $self->set_error("Cannot negociate the security layer");
my ($expected, $rspauth)
= $self->_compute_digests_and_set_keys($password, $self->{client_params});
return $self->set_error("Incorrect response $self->{client_params}->{response} <> $expected")
unless $expected eq $self->{client_params}->{response};
my %response = (
rspauth => $rspauth,
);
# I'm not entirely sure of what I am doing
$self->{answer}{$_} = $self->{client_params}->{$_} for qw/username authzid realm serv/;
$self->set_success;
return _response(\%response);
};
$self->callback('getsecret')->(
$self,
{ user => $username, realm => $realm, authzid => $authzid },
sub { $cb->( $response_check->( shift ) ) },
);
}
sub is_qop_supported {
my $self = shift;
my $qop = shift;
return $self->{supported_qop}{$qop};
}
sub _response {
my $response = shift;
my $is_client = shift;
my @out;
for my $k (sort keys %$response) {
my $is_array = ref $response->{$k} && ref $response->{$k} eq 'ARRAY';
my @values = $is_array ? @{$response->{$k}} : ($response->{$k});
# Per spec, one way of doing it: multiple k=v
#push @out, [$k, $_] for @values;
# other way: comma separated list
push @out, [$k, join (',', @values)];
}
return join (",", map { _qdval($_->[0], $_->[1], $is_client) } @out);
}
sub _parse_challenge {
my $self = shift;
my $challenge_ref = shift;
my $type = shift;
my $params = shift;
while($$challenge_ref =~
s/^(?:\s*,)*\s* # remaining or crap
([\w-]+) # key, eg: qop
=
("([^\\"]+|\\.)*"|[^,]+) # value, eg: auth-conf or "NoNcE"
\s*(?:,\s*)* # remaining
//x) {
my ($k, $v) = ($1,$2);
if ($v =~ /^"(.*)"$/s) {
($v = $1) =~ s/\\(.)/$1/g;
}
if (exists $multi{$type}{$k}) {
my $aref = $params->{$k} ||= [];
push @$aref, $v;
}
elsif (defined $params->{$k}) {
return $self->set_error("Bad challenge: '$$challenge_ref'");
}
else {
$params->{$k} = $v;
}
}
return length $$challenge_ref ? 0 : 1;
}
sub _qdval {
my ($k, $v, $is_client) = @_;
my $qdval = $is_client ? \%cqdval : \%sqdval;
if (!defined $v) {
return;
}
elsif (exists $qdval->{$k}) {
$v =~ s/([\\"])/\\$1/g;
return qq{$k="$v"};
}
return "$k=$v";
}
sub _server_layer {
my ($self, $auth) = @_;
# XXX dupe
# construct our qop mask
my $maxssf = $self->property('maxssf') - $self->property('externalssf');
$maxssf = 0 if ($maxssf < 0);
my $minssf = $self->property('minssf') - $self->property('externalssf');
$minssf = 0 if ($minssf < 0);
return undef if ($maxssf < $minssf); # sanity check
my $ciphers = [ map { $_->{name} } @ourciphers ];
if (( $auth eq 'auth-conf')
and $self->_select_cipher($minssf, $maxssf, $ciphers )) {
$self->property('ssf', $self->{cipher}->{ssf});
return 1;
}
if ($auth eq 'auth-int') {
$self->property('ssf', 1);
return 1;
}
if ($auth eq 'auth') {
$self->property('ssf', 0);
return 1;
}
return undef;
}
sub _client_layer {
my ($self, $sparams, $response) = @_;
# construct server qop mask
# qop in server challenge is optional: if not there "auth" is assumed
my $smask = 0;
map {
m/^auth$/ and $smask |= 1;
m/^auth-int$/ and $smask |= 2;
m/^auth-conf$/ and $smask |= 4;
} split(/,/, $sparams->{qop}||'auth'); # XXX I think we might have a bug here bc. of LWS
# construct our qop mask
my $cmask = 0;
my $maxssf = $self->property('maxssf') - $self->property('externalssf');
$maxssf = 0 if ($maxssf < 0);
my $minssf = $self->property('minssf') - $self->property('externalssf');
$minssf = 0 if ($minssf < 0);
return undef if ($maxssf < $minssf); # sanity check
# ssf values > 1 mean integrity and confidentiality
# ssf == 1 means integrity but no confidentiality
# ssf < 1 means neither integrity nor confidentiality
# no security layer can be had if buffer size is 0
$cmask |= 1 if ($minssf < 1);
$cmask |= 2 if ($minssf <= 1 and $maxssf >= 1);
$cmask |= 4 if ($maxssf > 1);
# find common bits
$cmask &= $smask;
# parse server cipher options
my @sciphers = split(/,/, $sparams->{'cipher-opts'}||$sparams->{cipher}||'');
if (($cmask & 4) and $self->_select_cipher($minssf,$maxssf,\@sciphers)) {
$response->{qop} = 'auth-conf';
$response->{cipher} = $self->{cipher}->{name};
$self->property('ssf', $self->{cipher}->{ssf});
return 1;
}
if ($cmask & 2) {
$response->{qop} = 'auth-int';
$self->property('ssf', 1);
return 1;
}
if ($cmask & 1) {
$response->{qop} = 'auth';
$self->property('ssf', 0);
return 1;
}
return undef;
}
sub _select_cipher {
my ($self, $minssf, $maxssf, $ciphers) = @_;
# compose a subset of candidate ciphers based on ssf and peer list
my @a = map {
my $c = $_;
(grep { $c->{name} eq $_ } @$ciphers and
$c->{ssf} >= $minssf and $c->{ssf} <= $maxssf) ? $_ : ()
} @ourciphers;
# from these, select the first one we can create an instance of
for (@a) {
next unless eval "require $_->{pkg}";
$self->{cipher} = $_;
return 1;
}
return 0;
}
use Digest::HMAC_MD5 qw(hmac_md5);
sub encode { # input: self, plaintext buffer,length (length not used here)
my $self = shift;
my $seqnum = pack('N', $self->{sndseqnum}++);
my $mac = substr(hmac_md5($seqnum . $_[0], $self->{kic}), 0, 10);
# if integrity only, return concatenation of buffer, MAC, TYPE and SEQNUM
return $_[0] . $mac.pack('n',1) . $seqnum unless ($self->{khc});
# must encrypt, block ciphers need padding bytes
my $pad = '';
my $bs = $self->{cipher}->{bs};
if ($bs > 1) {
# padding is added in between BUF and MAC
my $n = $bs - ((length($_[0]) + 10) & ($bs - 1));
$pad = chr($n) x $n;
}
# XXX - for future AES cipher support, the currently used common _crypt()
# function probably wont do; we might to switch to per-cipher routines
# like so:
# return $self->{khc}->encrypt($_[0] . $pad . $mac) . pack('n', 1) . $seqnum;
return $self->_crypt(0, $_[0] . $pad . $mac) . pack('n', 1) . $seqnum;
}
sub decode { # input: self, cipher buffer,length
my ($self, $buf, $len) = @_;
return if ($len <= 16);
# extract TYPE/SEQNUM from end of buffer
my ($type,$seqnum) = unpack('na[4]', substr($buf, -6, 6, ''));
# decrypt remaining buffer, if necessary
if ($self->{khs}) {
# XXX - see remark above in encode() #$buf = $self->{khs}->decrypt($buf);
$buf = $self->_crypt(1, $buf);
}
return unless ($buf);
# extract 10-byte MAC from the end of (decrypted) buffer
my ($mac) = unpack('a[10]', substr($buf, -10, 10, ''));
if ($self->{khs} and $self->{cipher}->{bs} > 1) {
# remove padding
my $n = ord(substr($buf, -1, 1));
substr($buf, -$n, $n, '');
}
# check the MAC
my $check = substr(hmac_md5($seqnum . $buf, $self->{kis}), 0, 10);
return if ($mac ne $check);
return if (unpack('N', $seqnum) != $self->{rcvseqnum});
$self->{rcvseqnum}++;
return $buf;
}
sub _crypt { # input: op(decrypting=1/encrypting=0)), buffer
my ($self,$d) = (shift,shift);
my $bs = $self->{cipher}->{bs};
if ($bs <= 1) {
# stream cipher
return $d ? $self->{khs}->decrypt($_[0]) : $self->{khc}->encrypt($_[0])
}
# the remainder of this sub is for block ciphers
# get current IV
my $piv = \$self->{$d ? 'ivs' : 'ivc'};
my $iv = $$piv;
my $result = join '', map {
my $x = $d
? $iv ^ $self->{khs}->decrypt($_)
: $self->{khc}->encrypt($iv ^ $_);
$iv = $d ? $_ : $x;
$x;
} unpack("a$bs "x(int(length($_[0])/$bs)), $_[0]);
# store current IV
$$piv = $iv;
return $result;
}
1;
__END__
=head1 NAME
Authen::SASL::Perl::DIGEST_MD5 - Digest MD5 Authentication class
=head1 SYNOPSIS
use Authen::SASL qw(Perl);
$sasl = Authen::SASL->new(
mechanism => 'DIGEST-MD5',
callback => {
user => $user,
pass => $pass,
serv => $serv
},
);
=head1 DESCRIPTION
This method implements the client and server parts of the DIGEST-MD5 SASL
algorithm, as described in RFC 2831.
=head2 CALLBACK
The callbacks used are:
=head3 client
=over 4
=item authname
The authorization id to use after successful authentication
=item user
The username to be used in the response
=item pass
The password to be used to compute the response.
=item serv
The service name when authenticating to a replicated service
=item realm
The authentication realm when overriding the server-provided default.
If not given the server-provided value is used.
The callback will be passed the list of realms that the server provided
in the initial response.
=back
=head3 server
=over4
=item realm
The default realm to provide to the client
=item getsecret(username, realm, authzid)
returns the password associated with C<username> and C<realm>
=back
=head2 PROPERTIES
The properties used are:
=over 4
=item maxbuf
The maximum buffer size for receiving cipher text
=item minssf
The minimum SSF value that should be provided by the SASL security layer.
The default is 0
=item maxssf
The maximum SSF value that should be provided by the SASL security layer.
The default is 2**31
=item externalssf
The SSF value provided by an underlying external security layer.
The default is 0
=item ssf
The actual SSF value provided by the SASL security layer after the SASL
authentication phase has been completed. This value is read-only and set
by the implementation after the SASL authentication phase has been completed.
=item maxout
The maximum plaintext buffer size for sending data to the peer.
This value is set by the implementation after the SASL authentication
phase has been completed and a SASL security layer is in effect.
=back
=head1 SEE ALSO
L<Authen::SASL>,
L<Authen::SASL::Perl>
=head1 AUTHORS
Graham Barr, Djamel Boudjerda (NEXOR), Paul Connolly, Julian Onions (NEXOR),
Yann Kerherve.
Please report any bugs, or post any suggestions, to the perl-ldap mailing list
<perl-ldap@perl.org>
=head1 COPYRIGHT
Copyright (c) 2003-2009 Graham Barr, Djamel Boudjerda, Paul Connolly,
Julian Onions, Nexor, Peter Marschall and Yann Kerherve.
All rights reserved. This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.
=cut