LWP::Authen::OAuth2 - Make requests to OAuth2 APIs.

version 0.20

OAuth 2 is a protocol that lets a user tell a service provider that a consumer has permission to use the service provider's APIs to do things that require access to the user's account. This module tries to make life easier for someone who wants to write a consumer in Perl.

Specifically it provides convenience methods for all of the requests that are made to the service provider as part of the permission handshake, and after that will proxy off of LWP::UserAgent to let you send properly authenticated requests to the API that you are trying to use. When possible, this will include transparent refresh/retry logic for access tokens expiration.

For a full explanation of OAuth 2, common terminology, the requests that get made, and the necessary tasks that this module does not address, please see LWP::Authen::OAuth2::Overview

This module will not help with OAuth 1. See the similarly named but unrelated LWP::Authen::OAuth for a module that can help with that.

Currently LWP::Authen::OAuth2 provides ready-to-use classes to use OAuth2 with

• Dwolla

  LWP::Authen::OAuth2::ServiceProvider::Dwolla

  implemented by Adi Fairbank

• Google

  LWP::Authen::OAuth2::ServiceProvider::Google

• Line

  LWP::Authen::OAuth2::ServiceProvider::Line

  implemented by Adam Millerchip

• Strava

  LWP::Authen::OAuth2::ServiceProvider::Strava

  implemented by Leon Wright

• Withings

  LWP::Authen::OAuth2::ServiceProvider::Withings

  implemented by Brian Foley

• Yahoo

  LWP::Authen::OAuth2::ServiceProvider::Yahoo

  implemented by Michael Stevens

You can also access any other OAuth2 service by setting up a plain LWP::Authen::OAuth2 object. If you do, and the service provider might be of interest to other people, please submit a patch so we can include it in this distribution, or release it as a standalone package.

Here are examples of simple usage.

use LWP::Authen::OAuth2;

# Constructor
my $oauth2 = LWP::Authen::OAuth2->new(
                 client_id => "Public from service provider",
                 client_secret => "s3cr3t fr0m svc prov",
                 service_provider => "Google",
                 redirect_uri => "https://your.url.com/",

                 # Optional hook, but recommended.
                 save_tokens => \&save_tokens,
                 save_tokens_args => [ $dbh ],

                 # This is for when you have tokens from last time.
                 token_string => $token_string.
             );

# URL for user to go to to start the process.
my $url = $oauth2->authorization_url();

# The authorization_url sends the user to the service provider to
# say that you want to be authorized.  After the user confirms that
# request, the service provider sends the user back to you with a
# code.  This might be a CGI parameter, something that the user is
# supposed to paste to you - that's between you and the service
# provider.

# Assuming that you have your code, get your tokens from the service
# provider.
$oauth2->request_tokens(code => $code);

# Get your token as a string you can easily store, pass around, etc.
# If you have a save_tokens callback, that gets passed this string
# whenever the tokens change.
#
# This string bears a suspicious resemblance to serialized JSON.
my $token_string = $oauth2->token_string,

# Access the API.  Consult the service_provider's documentation for when
# to use which type of request.  Note that argument processing is the
# same as in LWP.  Thus the parameters array and headers hash are both
# optional.
$oauth2->get($url, %header);
$oauth2->post($url, \@parameters, %header);
$oauth2->put($url, %header);
$oauth2->delete($url, %header);
$oauth2->head($url, %header);

# And if you need more flexibility, you can use LWP::UserAgent's request
# method
$oauth2->request($http_request, $content_file);

# In some flows you can refresh tokens, in others you have to go through
# the handshake yourself.  This method lets you know whether a refresh
# looks possible.
$oauth2->can_refresh_tokens();

# This method lets you know when it is time to reauthorize so that you
# can find out in a nicer way than failing an API call.
$oauth2->should_refresh();

When you call LWP::Authen::OAuth2->new(...), arguments are passed as a key/value list. They are processed in the following phases:

• Construct service provider
• Service provider collects arguments it wants
• LWP::Authen::OAuth2 overrides defaults from arguments
• Sanity check

Here are those phases in more detail.

• Construct service provider

  There are two ways to construct a service provider.

  • Prebuilt class

    To load a prebuilt class you just need one or two arguments.

    • service_provider => $Foo,

      In the above construct, $Foo identifies the base class for your service provider. The actual class will be the first of the following two classes that can be loaded. Failure to find either is an error.

        LWP::Authen::OAuth2::ServiceProvider $Foo
        $Foo
      

      A list of prebuilt service provider classes is in LWP::Authen::OAuth2::ServiceProvider as well as instructions for making a new one.

    • client_type => $name_of_client_type

      Some service providers will keep track of your client type ("webserver" application, "installed" application, etc), and will treat them differently. A base service provider class can choose to accept a client_type parameter to let it know what to expect.

      Whether this is done, and the allowable values, are up to the service provider class.

  • Built on the fly

    The behavior of simple service providers can be described on the fly without needing a prebuilt class. To do that, the following arguments can be filled with arguments from your service provider:

    • authorization_endpoint => $auth_url,

      This is the URL which the user is directed to in the authorization request.

    • token_endpoint => $token_url,

      This is the URL which the consumer goes to for tokens.

    • Various optional fields

      LWP::Authen::OAuth2::ServiceProvider documents many methods that are available to customize the actual requests made, and defaults available. Simple service providers can likely get by without this, but here is a list of those methods that can be specified instead in the constructor:

        # Arrayrefs
        required_init
        optional_init
        authorization_required_params
        authorization_optional_params
        request_required_params
        request_optional_params
        refresh_required_params
        refresh_optional_params
      
        # Hashrefs
        authorization_default_params
        request_default_params
        refresh_default_params
      

  • Service provider collects arguments it wants

    In general, arguments passed into the constructor do not have to be passed into individual method calls. Furthermore in order to be able to do the automatic token refresh for you, the constructor must include the arguments that will be required.

    By default you are required to pass your client_id and client_secret. And optionally can pass a redirect_uri and scope. (The omission of state is a deliberate hint that if you use that field, you should be generating random values on the fly. And not trying to go to some reasonable default.)

    However what is required is up to the service provider.

  • LWP::Authen::OAuth2 overrides defaults from arguments

    The following defaults are available to be overridden in the constructor, or can be overridden later. In the unlikely event that there is a conflict with the service provider's arguments, these will have to be overridden later.

    • error_handler => \&error_handler,

      Specifies the function that will be called when errors happen. The default is Carp::croak.

    • is_strict => $bool,

      Is strict mode on? If it is, then excess parameters to requests that are part of the authorization process will trigger errors. If it is not, then excess arguments are passed to the service provider as is, who according to the specification is supposed to ignore them.

      Strict mode is the default.

    • early_refresh_time => $seconds,

      How many seconds before the end of estimated access token expiration you will have should_refresh start returning true.

    • prerefresh => \&prerefresh,

      A handler to be called before attempting to refresh tokens. It is passed the $oauth2 object. If it returns a token string, that will be used to generate tokens instead of going to the service provider.

      The purpose of this hook is so that, even if you have multiple processes accessing an API simultaneously, only one of them will try to refresh tokens with the service provider. (Service providers may dislike having multiple refresh requests arrive at once from the same consumer for the same user.)

      By default this is not provided.

    • save_tokens => \&save_tokens,

      Whenever tokens are returned from the service provider, this callback will receive a token string that can be stored and then retrieved in another process that needs to construct a $oauth2 object.

      By default this is not provided. However if you intend to access the API multiple times from multiple processes, it is recommended.

    • save_tokens_args => [ args ],

      Additional arguments passed to the save_tokens callback function after the token string. This can be used to pass things like database handles or other data to the callback along with the token string. Provide a reference to an array of arguments in the constructure. When the callback is called the arguments are passed to the callback as an array, so in the example below $arg1 will be "foo" and $arg2 will be "bar"

        ...
        save_tokens => \&save_tokens,
        save_tokens_args => [ "foo", "bar" ],
        ...
      
        sub save_tokens {
            my ($token_string, $arg1, $arg2) = @_;
      
            ...
        }
      

    • token_string => $token_string,

      Supply tokens generated in a previous request so that you don't have to ask the service provider for new ones. Some service providers refuse to hand out tokens too quickly, so this can be important.

    • user_agent => $ua,

      What user agent gets used under the hood? Defaults to a new LWP::UserAgent created on the fly.

  • Sanity check

    Any arguments that are left over are assumed to be mistakes and a fatal warning is generated.

Once you have an object, the following methods may be useful for writing a consumer.

Generate a URL for the user to go to to request permissions. By default the response_type and client_id are defaulted, and all of redirect_uri, state and scope are optional but not required. However in practice this all varies by service provider and client type, so look for documentation on that for the actual list that you need.

Request tokens from the service provider (if possible). By default the grant_type, client_id and client_secret are defaulted, and the scope is required. However in practice this all varies by service provider and client type, so look for documentation on that for the actual list that you need.

Issue a get request to an OAuth 2 protected URL, just like you would using LWP::UserAgent to a normal URL.

Issue a head request to an OAuth 2 protected URL, just like you would using LWP::UserAgent to a normal URL.

Issue a post request to an OAuth 2 protected URL, just like you would using LWP::UserAgent to a normal URL.

Issue a delete request to an OAuth 2 protected URL, similar to the previous examples. (This shortcut is not by default available with LWP::UserAgent.)

Issue a put request to an OAuth 2 protected URL, similar to the previous examples. (This shortcut is not by default available with LWP::UserAgent.)

Issue any request that you could issue with LWP::UserAgent, except that it will be properly signed to go to an OAuth 2 protected URL.

This is a convenience method which makes a call to an OAuth2 API endpoint given by $uri, and returns the JSON response decoded to a hash. If the $params hashref arg is set, its contents will be JSON encoded and sent as POST request content; otherwise it will make a GET request. Optional $headers may be sent which will be passed through to $oauth->get() or $oauth->post().

If the call succeeds, it will return the response's JSON content decoded as hash, or if no response body was returned, a value of 1 to indicate success. On failure returns undef, and error message is available from $oauth2->api_call_error().

If an error occurred in $oauth2->make_api_call(), this method will return it. The error message comes from HTTP::Response->error_as_HTML().

Returns the base URL of the service provider, which is sometimes useful to be used in the content of OAuth2 API calls.

Is sufficient information available to try to refresh tokens?

Is it time to refresh tokens?

Set how many seconds before the end of token expiration the method should_refresh will start turning true. Values over half the initial expiration time of access tokens will be ignored to avoid refreshing too often. This defaults to 300.

Returns the raw epoch expiration time of the current access token. Typically this is 3600 seconds greater than the time of token creation.

Set strict mode on/off. See the discussion of is_strict in the constructor for an explanation of what it does.

Set the error handler. See the discussion of error_handler in the constructor for an explanation of what it does.

Set the prerefresh handler. See the discussion of prerefresh_handler in the constructor for an explanation of what it does.

Set the save tokens handler. See the discussion of save_tokens in the constructor for an explanation of what it does.

Set the user agent. This should respond to the same methods that a LWP::UserAgent responds to.

Get the user agent. The default if none was explicitly set is a new LWP::UserAgent object.

• Leon Wright
• Thomas Klausner
• Alex Dutton
• Chris
• Adi Fairbank
• Adam Millerchip
• André Brás

Thanks to Rent.com for their generous support in letting me develop and release this module. My thanks also to Nick Wellnhofer wellnhofer@aevum.de for Net::Google::Analytics::OAuth2 which was very enlightening while I was trying to figure out the details of how to connect to Google with OAuth2.

Thanks to

• Thomas Klausner for reporting that client type specific parameters were not available when the client type was properly specified
• Alex Dutton for making ServiceProvider work without requiring subclassing.
• Leon Wright for adding a Strava Service Provider and various bug fixes
• Adi Fairbank for adding a Dwolla Service Provider and some other improvements
• Adam Millerchip for adding a Line Service Provider and some refactoring
• Michael Stevens for adding a Yahoo | https://developer.yahoo.com Service Provider and some dist cleanup
• Nick Morrott for fixing some documentation typos

• Ben Tilly, <btilly at gmail.com>
• Thomas Klausner domm@plix.at

This software is copyright (c) 2013 - 2022 by Ben Tilly, Rent.com, Thomas Klausner.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.