Feature: Allowing relative redirect url though an option (#2183)

* Adding relative redirect url option

* Updating CHANGELOG.md

* tests: adding unit test for getOAuthRedirectURI

---------

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

CHANGELOG.md

@@ -7,10 +7,12 @@
 ## Breaking Changes
 
 ## Changes since v7.5.1
+
 - [#2128](https://github.com/oauth2-proxy/oauth2-proxy/pull/2128) Update dependencies (@vllvll)
 - [#2274](https://github.com/oauth2-proxy/oauth2-proxy/pull/2274) Upgrade golang.org/x/net to v0.17.0 (@pierluigilenoci)
 - [#2282](https://github.com/oauth2-proxy/oauth2-proxy/pull/2282) Fixed checking Google Groups membership using Google Application Credentials (@kvanzuijlen)
-
+- [#2183](https://github.com/oauth2-proxy/oauth2-proxy/pull/2183) Allowing relative redirect url though an option
+- 
 # V7.5.1
 
 ## Release Highlights

docs/docs/configuration/overview.md

@@ -165,6 +165,7 @@ An example [oauth2-proxy.cfg](https://github.com/oauth2-proxy/oauth2-proxy/blob/
 | `--real-client-ip-header` | string | Header used to determine the real IP of the client, requires `--reverse-proxy` to be set (one of: X-Forwarded-For, X-Real-IP, or X-ProxyUser-IP) | X-Real-IP                                                        |
 | `--redeem-url` | string | Token redemption endpoint |                                                                  |
 | `--redirect-url` | string | the OAuth Redirect URL, e.g. `"https://internalapp.yourcompany.com/oauth2/callback"` |                                                                  |
+| `--relative-redirect-url` | bool | allow relative OAuth Redirect URL.` |                                                                  |
 | `--redis-cluster-connection-urls` | string \| list | List of Redis cluster connection URLs (e.g. `redis://HOST[:PORT]`). Used in conjunction with `--redis-use-cluster` |                                                                  |
 | `--redis-connection-url` | string | URL of redis server for redis session storage (e.g. `redis://HOST[:PORT]`) |                                                                  |
 | `--redis-insecure-skip-tls-verify` | bool | skip TLS verification when connecting to Redis | false                                                            |

oauthproxy.go

@@ -86,6 +86,7 @@ type OAuthProxy struct {
 	allowedRoutes       []allowedRoute
 	apiRoutes           []apiRoute
 	redirectURL         *url.URL // the url to receive requests at
+	relativeRedirectURL bool
 	whitelistDomains    []string
 	provider            providers.Provider
 	sessionStore        sessionsapi.SessionStore
@@ -216,6 +217,7 @@ func NewOAuthProxy(opts *options.Options, validator func(string) bool) (*OAuthPr
 		provider:            provider,
 		sessionStore:        sessionStore,
 		redirectURL:         redirectURL,
+		relativeRedirectURL: opts.RelativeRedirectURL,
 		apiRoutes:           apiRoutes,
 		allowedRoutes:       allowedRoutes,
 		whitelistDomains:    opts.WhitelistDomains,
@@ -1018,7 +1020,7 @@ func prepareNoCacheMiddleware(next http.Handler) http.Handler {
 // This is usually the OAuthProxy callback URL.
 func (p *OAuthProxy) getOAuthRedirectURI(req *http.Request) string {
 	// if `p.redirectURL` already has a host, return it
-	if p.redirectURL.Host != "" {
+	if p.relativeRedirectURL || p.redirectURL.Host != "" {
 		return p.redirectURL.String()
 	}
 

oauthproxy_test.go

@@ -3257,3 +3257,90 @@ func TestAuthOnlyAllowedEmails(t *testing.T) {
 		})
 	}
 }
+
+func TestGetOAuthRedirectURI(t *testing.T) {
+	tests := []struct {
+		name      string
+		setupOpts func(*options.Options) *options.Options
+		req       *http.Request
+		want      string
+	}{
+		{
+			name: "redirect with https schema",
+			setupOpts: func(baseOpts *options.Options) *options.Options {
+				return baseOpts
+			},
+			req: &http.Request{
+				Host: "example",
+				URL: &url.URL{
+					Scheme: schemeHTTPS,
+				},
+			},
+			want: "https://example/oauth2/callback",
+		},
+		{
+			name: "redirect with http schema",
+			setupOpts: func(baseOpts *options.Options) *options.Options {
+				baseOpts.Cookie.Secure = false
+				return baseOpts
+			},
+			req: &http.Request{
+				Host: "example",
+				URL: &url.URL{
+					Scheme: schemeHTTP,
+				},
+			},
+			want: "http://example/oauth2/callback",
+		},
+		{
+			name: "relative redirect url",
+			setupOpts: func(baseOpts *options.Options) *options.Options {
+				baseOpts.RelativeRedirectURL = true
+				return baseOpts
+			},
+			req:  &http.Request{},
+			want: "/oauth2/callback",
+		},
+		{
+			name: "proxy prefix",
+			setupOpts: func(baseOpts *options.Options) *options.Options {
+				baseOpts.ProxyPrefix = "/prefix"
+				return baseOpts
+			},
+			req: &http.Request{
+				Host: "example",
+				URL: &url.URL{
+					Scheme: schemeHTTP,
+				},
+			},
+			want: "https://example/prefix/callback",
+		},
+		{
+			name: "proxy prefix with relative redirect",
+			setupOpts: func(baseOpts *options.Options) *options.Options {
+				baseOpts.ProxyPrefix = "/prefix"
+				baseOpts.RelativeRedirectURL = true
+				return baseOpts
+			},
+			req: &http.Request{
+				Host: "example",
+				URL: &url.URL{
+					Scheme: schemeHTTP,
+				},
+			},
+			want: "/prefix/callback",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			baseOpts := baseTestOptions()
+			err := validation.Validate(baseOpts)
+			assert.NoError(t, err)
+
+			proxy, err := NewOAuthProxy(tt.setupOpts(baseOpts), func(string) bool { return true })
+			assert.NoError(t, err)
+
+			assert.Equalf(t, tt.want, proxy.getOAuthRedirectURI(tt.req), "getOAuthRedirectURI(%v)", tt.req)
+		})
+	}
+}

pkg/apis/options/options.go

@@ -27,6 +27,7 @@ type Options struct {
 	TrustedIPs          []string `flag:"trusted-ip" cfg:"trusted_ips"`
 	ForceHTTPS          bool     `flag:"force-https" cfg:"force_https"`
 	RawRedirectURL      string   `flag:"redirect-url" cfg:"redirect_url"`
+	RelativeRedirectURL bool     `flag:"relative-redirect-url" cfg:"relative_redirect_url"`
 
 	AuthenticatedEmailsFile string   `flag:"authenticated-emails-file" cfg:"authenticated_emails_file"`
 	EmailDomains            []string `flag:"email-domain" cfg:"email_domains"`
@@ -117,6 +118,7 @@ func NewFlagSet() *pflag.FlagSet {
 	flagSet.StringSlice("trusted-ip", []string{}, "list of IPs or CIDR ranges to allow to bypass authentication. WARNING: trusting by IP has inherent security flaws, read the configuration documentation for more information.")
 	flagSet.Bool("force-https", false, "force HTTPS redirect for HTTP requests")
 	flagSet.String("redirect-url", "", "the OAuth Redirect URL. ie: \"https://internalapp.yourcompany.com/oauth2/callback\"")
+	flagSet.Bool("relative-redirect-url", false, "allow relative OAuth Redirect URL.")
 	flagSet.StringSlice("skip-auth-regex", []string{}, "(DEPRECATED for --skip-auth-route) bypass authentication for requests path's that match (may be given multiple times)")
 	flagSet.StringSlice("skip-auth-route", []string{}, "bypass authentication for requests that match the method & path. Format: method=path_regex OR method!=path_regex. For all methods: path_regex OR !=path_regex")
 	flagSet.StringSlice("api-route", []string{}, "return HTTP 401 instead of redirecting to authentication server if token is not valid. Format: path_regex")