LWP::Authen::OAuth2 - Make requests to OAuth2 APIs.
OAuth 2 is a protocol that let's 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.
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, # 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, \@parameters, %header); $oauth2->post($url, \@parameters, %header); $oauth2->put($url, \@parameters, %header); $oauth2->delete($url, \@parameters, %header); $oauth2->head($url, \@parameters, %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:
Here are those phases in more detail.
There are two ways to construct a service provider.
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.
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.
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
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_secret. And optionally can pass a
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.
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
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
By default this is not provided. However if you intend to access the API multiple times from multiple processes, it is recommended.
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.
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
client_id are defaulted, and all of
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
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.
get request to an OAuth 2 protected URL, just like you would using LWP::UserAgent to a normal URL.
head request to an OAuth 2 protected URL, just like you would using LWP::UserAgent to a normal URL.
post request to an OAuth 2 protected URL, just like you would using LWP::UserAgent to a normal URL.
delete request to an OAuth 2 protected URL, similar to the previous examples. (This shortcut is not by default available with LWP::UserAgent.)
put request to an OAuth 2 protected URL, similar to the previous examples. (This shortcut is not by default available with LWP::UserAgent.)
request that you could issue with LWP::UserAgent, except that it will be properly signed to go to an OAuth 2 protected URL.
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.
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.
<btilly at gmail.com>
Please report any bugs or feature requests to
bug-lwp-authen-oauth2 at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=LWP-Authen-OAuth2. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
You can find documentation for this module with the perldoc command.
You can also look for information at:
Thanks to Rent.com for their generous support in letting me develop and release this module. My thanks also to Nick Wellnhofer <firstname.lastname@example.org> 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 aka domm for reporting that client type specific parameters were not available when the client type was properly specified.
Copyright 2013 Rent.com.
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