*: add an OpenID Connect provider

Godeps

@@ -8,3 +8,6 @@ golang.org/x/oauth2                      7fdf09982454086d5570c7db3e11f360194830c
 golang.org/x/net/context                 242b6b35177ec3909636b6cf6a47e8c2c6324b5d
 google.golang.org/api/admin/directory/v1 650535c7d6201e8304c92f38c922a9a3a36c6877
 cloud.google.com/go/compute/metadata     v0.7.0
+github.com/coreos/go-oidc                c797a55f1c1001ec3169f1d0fbb4c5523563bec6
+gopkg.in/square/go-jose.v2               v2.1.1
+github.com/pquerna/cachecontrol          9299cc36e57c32f83e47ffb3c25d8a3dec10ea0b

README.md

@@ -139,6 +139,22 @@ For adding an application to the Microsoft Azure AD follow [these steps to add a
 
 Take note of your `TenantId` if applicable for your situation. The `TenantId` can be used to override the default `common` authorization server with a tenant specific server.
 
+### OpenID Connect Provider
+
+OpenID Connect is a spec for OAUTH 2.0 + identity that is implemented by many major providers and several open source projects. This provider was originally built against CoreOS Dex and we will use it as an example.
+
+1. Launch a Dex instance using the [getting started guide](https://github.com/coreos/dex/blob/master/Documentation/getting-started.md).
+2. Setup oauth2_proxy with the correct provider and using the default ports and callbacks.
+3. Login with the fixture use in the dex guide and run the oauth2_proxy with the following args:
+
+    -provider oidc
+    -client-id oauth2_proxy
+    -client-secret proxy
+    -redirect-url http://127.0.0.1:4180/oauth2/callback
+    -oidc-issuer-url http://127.0.0.1:5556
+    -cookie-secure=false
+    -email-domain example.com
+
 ## Email Authentication
 
 To authorize by email domain use `--email-domain=yourcompany.com`. To authorize individual email addresses use `--authenticated-emails-file=/path/to/file` with one email per line. To authorize all email addresses use `--email-domain=*`.

main.go

@@ -69,6 +69,7 @@ func main() {
 	flagSet.Bool("request-logging", true, "Log requests to stdout")
 
 	flagSet.String("provider", "google", "OAuth provider")
+	flagSet.String("oidc-issuer-url", "", "OpenID Connect issuer URL (ie: https://accounts.google.com)")
 	flagSet.String("login-url", "", "Authentication endpoint")
 	flagSet.String("redeem-url", "", "Token redemption endpoint")
 	flagSet.String("profile-url", "", "Profile access endpoint")

options.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"crypto"
 	"crypto/tls"
 	"encoding/base64"
@@ -14,6 +15,7 @@ import (
 
 	"github.com/18F/hmacauth"
 	"github.com/bitly/oauth2_proxy/providers"
+	oidc "github.com/coreos/go-oidc"
 )
 
 // Configuration Options that can be set by Command Line Flag, or Config File
@@ -63,6 +65,7 @@ type Options struct {
 	// These options allow for other providers besides Google, with
 	// potential overrides.
 	Provider          string `flag:"provider" cfg:"provider"`
+	OIDCIssuerURL     string `flag:"oidc-issuer-url" cfg:"oidc_issuer_url"`
 	LoginURL          string `flag:"login-url" cfg:"login_url"`
 	RedeemURL         string `flag:"redeem-url" cfg:"redeem_url"`
 	ProfileURL        string `flag:"profile-url" cfg:"profile_url"`
@@ -81,6 +84,7 @@ type Options struct {
 	CompiledRegex []*regexp.Regexp
 	provider      providers.Provider
 	signatureData *SignatureData
+	oidcVerifier  *oidc.IDTokenVerifier
 }
 
 type SignatureData struct {
@@ -120,6 +124,14 @@ func parseURL(to_parse string, urltype string, msgs []string) (*url.URL, []strin
 }
 
 func (o *Options) Validate() error {
+	if o.SSLInsecureSkipVerify {
+		// TODO: Accept a certificate bundle.
+		insecureTransport := &http.Transport{
+			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+		}
+		http.DefaultClient = &http.Client{Transport: insecureTransport}
+	}
+
 	msgs := make([]string, 0)
 	if len(o.Upstreams) < 1 {
 		msgs = append(msgs, "missing setting: upstream")
@@ -137,6 +149,22 @@ func (o *Options) Validate() error {
 		msgs = append(msgs, "missing setting for email validation: email-domain or authenticated-emails-file required.\n      use email-domain=* to authorize all email addresses")
 	}
 
+	if o.OIDCIssuerURL != "" {
+		// Configure discoverable provider data.
+		provider, err := oidc.NewProvider(context.Background(), o.OIDCIssuerURL)
+		if err != nil {
+			return err
+		}
+		o.oidcVerifier = provider.Verifier(&oidc.Config{
+			ClientID: o.ClientID,
+		})
+		o.LoginURL = provider.Endpoint().AuthURL
+		o.RedeemURL = provider.Endpoint().TokenURL
+		if o.Scope == "" {
+			o.Scope = "openid email profile"
+		}
+	}
+
 	o.redirectURL, msgs = parseURL(o.RedirectURL, "redirect", msgs)
 
 	for _, u := range o.Upstreams {
@@ -210,13 +238,6 @@ func (o *Options) Validate() error {
 	msgs = parseSignatureKey(o, msgs)
 	msgs = validateCookieName(o, msgs)
 
-	if o.SSLInsecureSkipVerify {
-		insecureTransport := &http.Transport{
-			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
-		}
-		http.DefaultClient = &http.Client{Transport: insecureTransport}
-	}
-
 	if len(msgs) != 0 {
 		return fmt.Errorf("Invalid configuration:\n  %s",
 			strings.Join(msgs, "\n  "))
@@ -252,6 +273,12 @@ func parseProviderInfo(o *Options, msgs []string) []string {
 				p.SetGroupRestriction(o.GoogleGroups, o.GoogleAdminEmail, file)
 			}
 		}
+	case *providers.OIDCProvider:
+		if o.oidcVerifier == nil {
+			msgs = append(msgs, "oidc provider requires an oidc issuer URL")
+		} else {
+			p.Verifier = o.oidcVerifier
+		}
 	}
 	return msgs
 }

providers/oidc.go

@@ -0,0 +1,84 @@
+package providers
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"golang.org/x/oauth2"
+
+	oidc "github.com/coreos/go-oidc"
+)
+
+type OIDCProvider struct {
+	*ProviderData
+
+	Verifier *oidc.IDTokenVerifier
+}
+
+func NewOIDCProvider(p *ProviderData) *OIDCProvider {
+	return &OIDCProvider{ProviderData: p}
+}
+
+func (p *OIDCProvider) Redeem(redirectURL, code string) (s *SessionState, err error) {
+	ctx := context.Background()
+	c := oauth2.Config{
+		ClientID:     p.ClientID,
+		ClientSecret: p.ClientSecret,
+		Endpoint: oauth2.Endpoint{
+			TokenURL: p.RedeemURL.String(),
+		},
+		RedirectURL: redirectURL,
+	}
+	token, err := c.Exchange(ctx, code)
+	if err != nil {
+		return nil, fmt.Errorf("token exchange: %v", err)
+	}
+
+	rawIDToken, ok := token.Extra("id_token").(string)
+	if !ok {
+		return nil, fmt.Errorf("token response did not contain an id_token")
+	}
+
+	// Parse and verify ID Token payload.
+	idToken, err := p.Verifier.Verify(ctx, rawIDToken)
+	if err != nil {
+		return nil, fmt.Errorf("could not verify id_token: %v", err)
+	}
+
+	// Extract custom claims.
+	var claims struct {
+		Email    string `json:"email"`
+		Verified *bool  `json:"email_verified"`
+	}
+	if err := idToken.Claims(&claims); err != nil {
+		return nil, fmt.Errorf("failed to parse id_token claims: %v", err)
+	}
+
+	if claims.Email == "" {
+		return nil, fmt.Errorf("id_token did not contain an email")
+	}
+	if claims.Verified != nil && !*claims.Verified {
+		return nil, fmt.Errorf("email in id_token (%s) isn't verified", claims.Email)
+	}
+
+	s = &SessionState{
+		AccessToken:  token.AccessToken,
+		RefreshToken: token.RefreshToken,
+		ExpiresOn:    token.Expiry,
+		Email:        claims.Email,
+	}
+
+	return
+}
+
+func (p *OIDCProvider) RefreshSessionIfNeeded(s *SessionState) (bool, error) {
+	if s == nil || s.ExpiresOn.After(time.Now()) || s.RefreshToken == "" {
+		return false, nil
+	}
+
+	origExpiration := s.ExpiresOn
+	s.ExpiresOn = time.Now().Add(time.Second).Truncate(time.Second)
+	fmt.Printf("refreshed access token %s (expired on %s)\n", s, origExpiration)
+	return false, nil
+}

providers/providers.go

@@ -30,6 +30,8 @@ func New(provider string, p *ProviderData) Provider {
 		return NewAzureProvider(p)
 	case "gitlab":
 		return NewGitLabProvider(p)
+	case "oidc":
+		return NewOIDCProvider(p)
 	default:
 		return NewGoogleProvider(p)
 	}