OAuth2 for Go - extended with advanced authentication

This repo is a drop-in replacement of golang.org/x/oauth2

It extends the original library with additional authentication methods:

private_key_jwt

Additionally, it also adds utility methods for easy use of PKCE.

Installation

When using go modules you can run:

go mod edit -replace golang.org/x/oauth2 github.com/cloudentity/oauth2

Usage

When using any of the originally supported authentication methods, there's no need to change anything. This library can be used as a drop-in replacement.

For new authentication methods see the examples below:

Private Key JWT

Client credentials

import (
	"context"
	"time"

	"golang.org/x/oauth2"
	"golang.org/x/oauth2/advancedauth"
	"golang.org/x/oauth2/clientcredentials"
)

    cfg := clientcredentials.Config{
        ClientID: "your client id",
        AuthStyle: oauth2.AuthStylePrivateKeyJWT,
        PrivateKeyAuth: advancedauth.PrivateKeyAuth{
    		Key:         "your PEM encoded private key",
    		Algorithm:   advancedauth.RS256,
    		Exp:         30 * time.Second,
        },
    }

    token, err := cfg.Token(context.Background())

Authorization code

import (
	"context"
	"time"

	"golang.org/x/oauth2"
	"golang.org/x/oauth2/advancedauth"
)

    cfg := oauth2.Config{
        ClientID: "your client id",
        Endpoint: oauth2.Endpoint{
            AuthStyle: oauth2.AuthStylePrivateKeyJWT,
        },
        PrivateKeyAuth: advancedauth.PrivateKeyAuth{
    		Key:         "your PEM encoded private key",
    		Algorithm:   advancedauth.RS256,
    		Exp:         30 * time.Second,
        },
        Scopes: []string{"scope1", "scope2"},
    },

    token, err := cfg.Exchange(context.Background(), "your authorization code")

TLS Auth

If you want to use tls_client_auth or self_signed_tls_client_auth there is no dedicated configuration for the client certificate and key.

You should create an appropriate *http.Client and pass it in the context.

One thing this library does is that it adds an AuthStyle AuthStyleTLS which appropriately sends the client_id but skips the client_secret.

Example:

import (
	"context"
	"time"

	"golang.org/x/oauth2"
	"golang.org/x/oauth2/advancedauth"
	"golang.org/x/oauth2/clientcredentials"
)

    // ... generate cert

    client := &http.Client{
        Transport: &http.Transport{
            TLSClientConfig: &tls.Config{
                Certificates: []tls.Certificate{cert},
            },
        },
    }

    cfg := clientcredentials.Config{
        ClientID: "your client id",
        AuthStyle: oauth2.AuthStyleTLS,
    }

    token, err := cfg.Token(context.WithValue(context.Background(), oauth2.HTTPClient, client))

PKCE

import (
	"context"
	"time"

	"golang.org/x/oauth2"
	"golang.org/x/oauth2/advancedauth/pkce"
)

Create PKCE with

    p, err := pkce.New()

or, if you want to specify the code challenge method and verifier length

    p, err := pkce.NewWithMethodVerifierLength(pkce.512, 84)

AuthCodeURL

PKCE exposes few utility methods to ease creating AuthCodeURL

You can use utility methods returning needed AuthCodeOption's

    url = conf.AuthCodeURL("state", p.AuthCodeURLOpts()...)

or, individual methods

    url := conf.AuthCodeURL("state", p.ChallengeOpt(), p.MethodOpt())

Exchange

PKCE also exposes similar methods for Exchange

    tok, err := conf.Exchange(context.Background(), "exchange-code", p.ExchangeOpts()...)

or, with individual methods

    tok, err := conf.Exchange(context.Background(), "exchange-code", p.VerifierOpt(), p.MethodOpt())

Implementation

This fork tries to limit changes to the original codebase to the minimum. All the new major changes are implemented in the advancedauth package.