NAME
Crypt::U2F::Server::Simple - Register and Authenticate U2F compatible security devices
SYNOPSIS
use Crypt::U2F::Server:Simple;
my $crypter = Crypt::U2F::Server::Simple->new(
appId => 'Perl',
origin => 'http://search.cpan.org'
);
# Generate a registration request
my $registerRequest = $crypter->registrationChallenge();
# Give $registerRequest to client, receive $registrationData from client
# NB: if Crypt::U2F::Server::Simple has been recreated (web process for example), challenge
# value must be restored (value only, not JSON blob):
#$crypter->setChallenge($challenge)
my ($keyHandle, $userKey) = $crypter->registrationVerify($registrationData)
# Generate an authentication request (using the previously generated key handle and user key)
my $authrequest = $crypter->authenticationChallenge();
# Send $authrequest to client, receive $authSignature
# NB: if Crypt::U2F::Server::Simple has been recreated (web process for example), challenge
# value must be restored (value only, not JSON blob):
#$crypter->setChallenge($challenge)
my $authok = $crypter->authenticationVerify($authSignature);DESCRIPTION
This module implements the server side of U2F authentication through Yubico's C library.
Both registration and authentication are two step processes that each must be run in the same instance of this perl module. To clarify You can run registration from another instance than authentication, or even in another program on another server. But, as far as it is currently implemented, you must run both registration steps in the same instance of this module, the same goes for authentication. Needs more testing, really.
A successful registration of a key yields to two scalars, a key handle and a public key. It is your responsibility to keep them safe somewhere and reload them into this module whenever you want to do authentication.
INSTALLATION
This module requires the Yubico u2f-server shared library installed, please see the official project page at https://developers.yubico.com/libu2f-server/ on how to do that.
NO MULTITHREADING
The way this is currently implemented, i doubt very much that multithreadingm will work. Multi-Forking should be OK as long as you only call new() after forking, though. Also using more than one instance of this module in your program. This isn't really tested at the moment, though...
ALPHA WARNING
As already stated above, at this time Crypt::U2F::Server and Crypt::U2F::Server::Simple have seen only very limited testing and the modules are still subject to change.
That isn't to say that you shouldn't use this at all. Rather, if you are interested, you should test this a lot and report any bugs you find!
FUNCTION DESCRIPTION
lastError()
Probably the most important function of all, therefore mention first. If something goes wrong (but not HorriblyWrong[tm]), you'll get the last error description of whatever happened.
If something fails during new(), call it with the full name:
my $oooops = Crypt::U2F::Server::Simple::lastError();If you already got an instance, you can use that as well:
my $oooops = $auth->lastError();Errors are global over all instances of this module.
If things go HorriblyWrong[tm], your program might crash. Or get remote-buffer-overflow-exploited or something. In these case, lastError() might not work reliably. You know, just the usual crypto stuff...
new()
This comes in two forms, depending if you do authentication in the same instance as the registration steps.
The simple form (only registration or registration+authentication) only requires the arguments appId and origin:
my $auth = Crypt::U2F::Server::Simple->new(
appId => 'Perl',
origin => 'http://search.cpan.org'
);If you only do authentication, you have to supply the keyHandle and publicKey data as well:
my $auth = Crypt::U2F::Server::Simple->new(
appId => 'Perl',
origin => 'http://search.cpan.org',
keyHandle => $keyHandleData
publicKey => $publicKeyData
);For security, i would recommend creating a new instance for each and every authentication request.
If something goes wrong during initialization, $auth will be undef.
To enable Yubico library debug, set debug to 1:
my $auth = Crypt::U2F::Server::Simple->new(
appId => 'Perl',
origin => 'http://search.cpan.org',
debug => 1
);registrationChallenge()
my $challenge = $auth->registrationChallenge();Gives you a unique registration challenge on every call. This is a JSON string and should be send to the client (called a "host" for whatever reason) as is.
If something goes wrong, $challenge will be undef.
$challenge is a JSON blob that contains a hash. Here are the main keys
registrationVerify()
my ($keyHandle, $publicKey) = $auth->registrationVerify($reply);If the client (the "host") accepts the challenge, it will send you another JSON blob ($reply).
If everything goes well and registration succeeds, you will get the key handle and public key of, well client key. If it fails, you will get undef.
$keyHandle and $publicKey will get set internally for direct following authentication in the same instance, you need to store it in some persistent way yourself for future authentication.
As an added bonus, $publicKey will be a binary blob, so you may have to convert it to something like Base64 for easier handling. See MIME::Base64 on how to do that. Make sure you un-encode before loading it into this module!
authenticationChallenge()
This function generates an authentication challenge. To do that, it needs keyHandle and publicKey, since this is key dependent.
my $challenge = $auth->authenticationChallenge();Otherwise, this works the same as the registration challenge. You get a JSON blob, send that to the client and get an answer.
The JSON blob structure is described in registrationChallenge() doc.
authenticationVerify()
After you get the authentication answer, you need to verify it:
my $isValid = $auth->authenticationVerify($reply);$isValid is true if authentication succeedsr. If something went wrong (library error, fake user), $isValid is false, in which case you can look into lastError() to see what went wrong.
setChallenge()
If Crypt::U2F::Server::Simple has been recreated since registrationChallenge() or authenticationChallenge() usage, challenge value must be restored:
$auth->setChallenge($challenge)Note that $challenge must be the string value of challenge, not the JSON blob. See registrationChallenge() doc to get challenge description.
SEE ALSO
See Crypt::U2F::Server for the low level library if you want better headaches.
There are two examples in the tarball for registration and authentication.
BUGS
Yes, there should be some in there. First of all, this is crypto stuff, so it's broken by default (it only depends on the time it takes to happen).
Also, at the moment, this module has seen only very limited testing.
AUTHOR
COPYRIGHT AND LICENSE
Adapted as a Perl library by Rene 'cavac' Schickbauer
This roughly based on u2f-server.c from Yubico's C library, see https://developers.yubico.com/libu2f-server/
In order for this to work, you need to install that library.
This adaption is (C) 2014-2018 Rene 'cavac' Schickbauer and 2018 Xavier Guimard, but as it is based on Yubico's code, the licence below applies!
We, the community, would hereby thank Yubico for open sourcing their code!
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