NAME
Crypt::SRP - Secure Remote Protocol (SRP6a)
SYNOPSIS
Example 1 - SRP login handshake:
###CLIENT###
my $I = '...'; # login entered by user
my $P = '...'; # password entered by user
my $cli = Crypt::SRP->new('RFC5054-1024bit', 'SHA1');
my ($A, $a) = $cli->client_compute_A;
# request[1] to server: ---> /auth/srp_step1 ($I, $A) --->
###SERVER###
my %USERS; # sort of "user database"
my %TOKENS; # sort of temporary "token database"
my $v = $USERS{$I}->{verifier};
my $s = $USERS{$I}->{salt};
my $srv = Crypt::SRP->new('RFC5054-1024bit', 'SHA1');
return unless $srv->server_verify_A($A);
$srv->server_init($I, $v, $s);
my ($B, $b) = $srv->server_compute_B;
my $token = $srv->random_bytes(32);
$TOKENS{$token} = [$I, $A, $B, $b];
# response[1] from server: <--- ($B, $s, $token) <---
###CLIENT###
return unless $cli->client_verify_B($B);
$cli->client_init($I, $P, $s);
my $M1 = $cli->client_compute_M1;
# request[2] to server: ---> /auth/srp_step2 ($M1, $token) --->
###SERVER###
my $M2 = '';
return unless $M1 && $token && $TOKENS{$token};
my ($I, $A, $B, $b) = @{delete $TOKENS{$token}};
return unless $I && $A && $B && $b && $USERS{$I};
my $s = $USERS{$I}->{salt};
my $v = $USERS{$I}->{verifier};
return unless $s && $v;
my $srv = Crypt::SRP->new('RFC5054-1024bit', 'SHA1');
$srv->server_init($I, $v, $s, $A, $B, $b);
return unless $srv->server_verify_M1($M1);
$M2 = $srv->server_compute_M2;
my $K = $srv->get_secret_K; # shared secret
# response[2] from server: <--- ($M2) <---
###CLIENT###
if ($M2 && $cli->client_verify_M2($M2)) {
my $K = $cli->get_secret_K; # shared secret
print "SUCCESS";
}
else {
print "ERROR";
}Example 2 - creating a new user and his/her password verifier:
###CLIENT###
my $I = '...'; # login entered by user
my $P = '...'; # password entered by user
my $cli = Crypt::SRP->new('RFC5054-1024bit', 'SHA1');
my ($v, $s) = $cli->compute_verifier_and_salt($I, $P);
# request to server: ---> /auth/create_user [$I, $s, $v] --->
###SERVER###
my %USERS; # sort of "user database"
die "user already exists" unless $USERS{$I};
$USERS{$I}->{salt} = $s;
$USERS{$I}->{verifier} = $v;Working sample implementation of SRP authentication on client and server side is available in examples subdirectory: srp_server.pl, srp_client.pl.
DESCRIPTION
More info about SRP protocol:
This module implements SRP version 6a.
METHODS
Login and password ($I, $P) can be ASCII strings (without utf8 flag) or raw octets. If you want special characters in login and/or password then you have to encode them from Perl's internal from like this: $I = encode('utf8', $I) or $P = encode('utf8', $P)
All SRP related variables ($s, $v, $A, $a, $B, $b, $M1, $M2, $S, $K) are by defaults raw octets (no BigInts, no strings with utf8 flag). However if you set new's optional parameter $format to 'hex', 'base64' or 'base64url' SRP related input parameters (not $I or $P) are expected in given encoding and return values are converted into the same encoding as well.
new
my $srp = Crypt::SRP->new(); #or my $srp = Crypt::SRP->new({ group => $group, hash => $hash, format => $format }); # group - DEFAULT='RFC5054-2048bit' # 'RFC5054-1024bit' or 'RFC5054-1536bit' or 'RFC5054-2048bit' or # 'RFC5054-3072bit' or 'RFC5054-4096bit' or 'RFC5054-6144bit' or # 'RFC5054-8192bit' see rfc5054 (appendix A) # hash - DEFAULT='SHA256' # 'SHA1' or 'SHA256' or 'SHA384' or 'SHA512' # format - DEFAULT='raw' # 'raw' or 'hex' or 'base64' or 'base64url' # interleaved - DEFAULT=0 # indicates whether the final shared secret K will be computed # as SHAx(S) or SHAx_Interleaved(S) see rfc2945 (3.1 Interleaved SHA) # saltlen - DEFAULT=32 # default length (in bytes) for generated salt # srptools - DEFAULT=0 (since v0.018) # operate in a mode compatible with python package srptools # appletv - DEFAULT=0 (since v0.018) # operate in a mode compatible with SRP6a used by AppleTV / AirPlayAuth #or (OLD interface) my $srp = Crypt::SRP->new($group, $hash, $format, $interleaved, $default_salt_len);reset
$srp->reset(); #or $srp->reset({ group => $group, hash => $hash, format => $format }); # see new() #or $srp->reset($group, $hash, $format, $interleaved, $default_salt_len); # see new() # returns $srp (itself)dump
my $serialized_state = $srp->dump();load
$srp->load($serialized_state);compute_verifier
my $v = $srp->compute_verifier($I, $P, $s);compute_verifier_and_salt
my ($v, $s) = $srp->compute_verifier_and_salt($I, $P); #or my ($v, $s) = $srp->compute_verifier_and_salt($I, $P, $s_len);client_init
$srp->client_init($I, $P, $s, $B); # returns $srp (itself)client_compute_A
my ($A, $a) = $srp->client_compute_A(); #or my ($A, $a) = $srp->client_compute_A($a_len);client_compute_M1
my $M1 = $srp->client_compute_M1($B);client_verify_M2
my $valid = $srp->client_verify_M2($M2);client_verify_B
my $valid = client_verify_B($B);server_init
$srp->server_init($I, $v, $s); #or $srp->server_init($I, $v, $s, $A, $B, $b); # returns $srp (itself)server_compute_B
my ($B, $b) = $srp->server_compute_B(); #or my ($B, $b) = $srp->server_compute_B($b_len);server_fake_B_s
my ($B, $s) = $srp->server_fake_B_s($I); #or my ($B, $s) = $srp->server_fake_B_s($I, $nonce); #or my ($B, $s) = $srp->server_fake_B_s($I, $nonce, $s_len);server_verify_M1
my $valid = $srp->server_verify_M1($M1);server_compute_M2
my $M2 = $srp->server_compute_M2();server_verify_A
my $valid = server_verify_A($A);get_secret_S
my $S = $srp->get_secret_S(); #or my $S = $srp->get_secret_S($format); # $format can me 'raw' or 'hex' or 'base64' or 'base64url'get_secret_K
my $K = $srp->get_secret_K(); #or my $K = $srp->get_secret_K($format); # $format can me 'raw' or 'hex' or 'base64' or 'base64url'random_bytes
my $rand = $srp->random_bytes(); # $rand formated according to $format passed to new() #or my $rand = $srp->random_bytes($len); my $rand = Crypt::SRP->random_bytes(); # $rand always raw bytes #or my $rand = Crypt::SRP->random_bytes($len);
LICENSE
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
COPYRIGHT
Copyright (c) 2012+ DCIT, a.s. https://www.dcit.cz / Karel Miko