oidc authentication plugin: don't trim issuer URLs with trailing slashes

The issuer URL passed to the plugin must identically match the issuer
URL returned by OpenID Connect discovery. However, the plugin currently
trims all trailing slashes from issuer URLs, causing a mismatch. Since
the go-oidc client already handles this case correctly, don't trim the
path.

plugin/pkg/auth/authenticator/token/oidc/oidc.go

@@ -33,7 +33,6 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
-	"strings"
 	"sync"
 	"sync/atomic"
 
@@ -174,7 +173,7 @@ func (a *OIDCAuthenticator) client() (*oidc.Client, error) {
 	}
 
 	// Try to initialize client.
-	providerConfig, err := oidc.FetchProviderConfig(a.httpClient, strings.TrimSuffix(a.issuerURL, "/"))
+	providerConfig, err := oidc.FetchProviderConfig(a.httpClient, a.issuerURL)
 	if err != nil {
 		glog.Errorf("oidc authenticator: failed to fetch provider discovery data: %v", err)
 		return nil, fmt.Errorf("fetch provider config: %v", err)

plugin/pkg/auth/authenticator/token/oidc/oidc_test.go

@@ -110,14 +110,13 @@ func TestTLSConfig(t *testing.T) {
 
 	for _, tc := range tests {
 		func() {
-			op := oidctesting.NewOIDCProvider(t)
+			op := oidctesting.NewOIDCProvider(t, "")
 			srv, err := op.ServeTLSWithKeyPair(tc.serverCertFile, tc.serverKeyFile)
 			if err != nil {
 				t.Errorf("%s: %v", tc.testCase, err)
 				return
 			}
 			defer srv.Close()
-			op.AddMinimalProviderConfig(srv)
 
 			issuer := srv.URL
 			clientID := "client-foo"
@@ -178,8 +177,6 @@ func TestTLSConfig(t *testing.T) {
 }
 
 func TestOIDCAuthentication(t *testing.T) {
-	var err error
-
 	cert := path.Join(os.TempDir(), "oidc-cert")
 	key := path.Join(os.TempDir(), "oidc-key")
 
@@ -188,119 +185,120 @@ func TestOIDCAuthentication(t *testing.T) {
 
 	oidctesting.GenerateSelfSignedCert(t, "127.0.0.1", cert, key)
 
-	// Create a TLS server and a client.
+	// Ensure all tests pass when the issuer is not at a base URL.
-	op := oidctesting.NewOIDCProvider(t)
+	for _, path := range []string{"", "/path/with/trailing/slash/"} {
-	srv, err := op.ServeTLSWithKeyPair(cert, key)
-	if err != nil {
-		t.Fatalf("Cannot start server: %v", err)
-	}
-	defer srv.Close()
 
-	// A provider config with all required fields.
+		// Create a TLS server and a client.
-	op.AddMinimalProviderConfig(srv)
+		op := oidctesting.NewOIDCProvider(t, path)
-
+		srv, err := op.ServeTLSWithKeyPair(cert, key)
-	tests := []struct {
-		userClaim   string
-		groupsClaim string
-		token       string
-		userInfo    user.Info
-		verified    bool
-		err         string
-	}{
-		{
-			"sub",
-			"",
-			generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "sub", "user-foo", "", nil),
-			&user.DefaultInfo{Name: fmt.Sprintf("%s#%s", srv.URL, "user-foo")},
-			true,
-			"",
-		},
-		{
-			// Use user defined claim (email here).
-			"email",
-			"",
-			generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "email", "foo@example.com", "", nil),
-			&user.DefaultInfo{Name: "foo@example.com"},
-			true,
-			"",
-		},
-		{
-			// Use user defined claim (email here).
-			"email",
-			"",
-			generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "email", "foo@example.com", "groups", []string{"group1", "group2"}),
-			&user.DefaultInfo{Name: "foo@example.com"},
-			true,
-			"",
-		},
-		{
-			// Use user defined claim (email here).
-			"email",
-			"groups",
-			generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "email", "foo@example.com", "groups", []string{"group1", "group2"}),
-			&user.DefaultInfo{Name: "foo@example.com", Groups: []string{"group1", "group2"}},
-			true,
-			"",
-		},
-		{
-			"sub",
-			"",
-			generateMalformedToken(t, op, srv.URL, "client-foo", "client-foo", "sub", "user-foo", "", nil),
-			nil,
-			false,
-			"oidc: unable to verify JWT signature: no matching keys",
-		},
-		{
-			// Invalid 'aud'.
-			"sub",
-			"",
-			generateGoodToken(t, op, srv.URL, "client-foo", "client-bar", "sub", "user-foo", "", nil),
-			nil,
-			false,
-			"oidc: JWT claims invalid: invalid claims, 'aud' claim and 'client_id' do not match",
-		},
-		{
-			// Invalid issuer.
-			"sub",
-			"",
-			generateGoodToken(t, op, "http://foo-bar.com", "client-foo", "client-foo", "sub", "user-foo", "", nil),
-			nil,
-			false,
-			"oidc: JWT claims invalid: invalid claim value: 'iss'.",
-		},
-		{
-			"sub",
-			"",
-			generateExpiredToken(t, op, srv.URL, "client-foo", "client-foo", "sub", "user-foo", "", nil),
-			nil,
-			false,
-			"oidc: JWT claims invalid: token is expired",
-		},
-	}
-
-	for i, tt := range tests {
-		client, err := New(OIDCOptions{srv.URL, "client-foo", cert, tt.userClaim, tt.groupsClaim})
 		if err != nil {
-			t.Errorf("Unexpected error: %v", err)
+			t.Fatalf("Cannot start server: %v", err)
-			continue
+		}
+		defer srv.Close()
+
+		tests := []struct {
+			userClaim   string
+			groupsClaim string
+			token       string
+			userInfo    user.Info
+			verified    bool
+			err         string
+		}{
+			{
+				"sub",
+				"",
+				generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "sub", "user-foo", "", nil),
+				&user.DefaultInfo{Name: fmt.Sprintf("%s#%s", srv.URL, "user-foo")},
+				true,
+				"",
+			},
+			{
+				// Use user defined claim (email here).
+				"email",
+				"",
+				generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "email", "foo@example.com", "", nil),
+				&user.DefaultInfo{Name: "foo@example.com"},
+				true,
+				"",
+			},
+			{
+				// Use user defined claim (email here).
+				"email",
+				"",
+				generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "email", "foo@example.com", "groups", []string{"group1", "group2"}),
+				&user.DefaultInfo{Name: "foo@example.com"},
+				true,
+				"",
+			},
+			{
+				// Use user defined claim (email here).
+				"email",
+				"groups",
+				generateGoodToken(t, op, srv.URL, "client-foo", "client-foo", "email", "foo@example.com", "groups", []string{"group1", "group2"}),
+				&user.DefaultInfo{Name: "foo@example.com", Groups: []string{"group1", "group2"}},
+				true,
+				"",
+			},
+			{
+				"sub",
+				"",
+				generateMalformedToken(t, op, srv.URL, "client-foo", "client-foo", "sub", "user-foo", "", nil),
+				nil,
+				false,
+				"oidc: unable to verify JWT signature: no matching keys",
+			},
+			{
+				// Invalid 'aud'.
+				"sub",
+				"",
+				generateGoodToken(t, op, srv.URL, "client-foo", "client-bar", "sub", "user-foo", "", nil),
+				nil,
+				false,
+				"oidc: JWT claims invalid: invalid claims, 'aud' claim and 'client_id' do not match",
+			},
+			{
+				// Invalid issuer.
+				"sub",
+				"",
+				generateGoodToken(t, op, "http://foo-bar.com", "client-foo", "client-foo", "sub", "user-foo", "", nil),
+				nil,
+				false,
+				"oidc: JWT claims invalid: invalid claim value: 'iss'.",
+			},
+			{
+				"sub",
+				"",
+				generateExpiredToken(t, op, srv.URL, "client-foo", "client-foo", "sub", "user-foo", "", nil),
+				nil,
+				false,
+				"oidc: JWT claims invalid: token is expired",
+			},
 		}
 
-		user, result, err := client.AuthenticateToken(tt.token)
+		for i, tt := range tests {
-		if tt.err != "" {
+			client, err := New(OIDCOptions{srv.URL, "client-foo", cert, tt.userClaim, tt.groupsClaim})
-			if !strings.HasPrefix(err.Error(), tt.err) {
-				t.Errorf("#%d: Expecting: %v..., but got: %v", i, tt.err, err)
-			}
-		} else {
 			if err != nil {
-				t.Errorf("#%d: Unexpected error: %v", i, err)
+				t.Errorf("Unexpected error: %v", err)
+				continue
 			}
+
+			user, result, err := client.AuthenticateToken(tt.token)
+			if tt.err != "" {
+				if !strings.HasPrefix(err.Error(), tt.err) {
+					t.Errorf("#%d: Expecting: %v..., but got: %v", i, tt.err, err)
+				}
+			} else {
+				if err != nil {
+					t.Errorf("#%d: Unexpected error: %v", i, err)
+				}
+			}
+			if !reflect.DeepEqual(tt.verified, result) {
+				t.Errorf("#%d: Expecting: %v, but got: %v", i, tt.verified, result)
+			}
+			if !reflect.DeepEqual(tt.userInfo, user) {
+				t.Errorf("#%d: Expecting: %v, but got: %v", i, tt.userInfo, user)
+			}
+			client.Close()
 		}
-		if !reflect.DeepEqual(tt.verified, result) {
-			t.Errorf("#%d: Expecting: %v, but got: %v", i, tt.verified, result)
-		}
-		if !reflect.DeepEqual(tt.userInfo, user) {
-			t.Errorf("#%d: Expecting: %v, but got: %v", i, tt.userInfo, user)
-		}
-		client.Close()
 	}
 }

plugin/pkg/auth/authenticator/token/oidc/testing/provider.go

@@ -33,6 +33,7 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"os"
+	"path"
 	"path/filepath"
 	"testing"
 	"time"
@@ -43,7 +44,7 @@ import (
 )
 
 // NewOIDCProvider provides a bare minimum OIDC IdP Server useful for testing.
-func NewOIDCProvider(t *testing.T) *OIDCProvider {
+func NewOIDCProvider(t *testing.T, issuerPath string) *OIDCProvider {
 	privKey, err := key.GeneratePrivateKey()
 	if err != nil {
 		t.Fatalf("Cannot create OIDC Provider: %v", err)
@@ -51,20 +52,22 @@ func NewOIDCProvider(t *testing.T) *OIDCProvider {
 	}
 
 	op := &OIDCProvider{
-		Mux:     http.NewServeMux(),
+		Mux:        http.NewServeMux(),
-		PrivKey: privKey,
+		PrivKey:    privKey,
+		issuerPath: issuerPath,
 	}
 
-	op.Mux.HandleFunc("/.well-known/openid-configuration", op.handleConfig)
+	op.Mux.HandleFunc(path.Join(issuerPath, "/.well-known/openid-configuration"), op.handleConfig)
-	op.Mux.HandleFunc("/keys", op.handleKeys)
+	op.Mux.HandleFunc(path.Join(issuerPath, "/keys"), op.handleKeys)
 
 	return op
 }
 
 type OIDCProvider struct {
-	Mux     *http.ServeMux
+	Mux        *http.ServeMux
-	PCFG    oidc.ProviderConfig
+	PCFG       oidc.ProviderConfig
-	PrivKey *key.PrivateKey
+	PrivKey    *key.PrivateKey
+	issuerPath string
 }
 
 func (op *OIDCProvider) ServeTLSWithKeyPair(cert, key string) (*httptest.Server, error) {
@@ -77,20 +80,31 @@ func (op *OIDCProvider) ServeTLSWithKeyPair(cert, key string) (*httptest.Server,
 		return nil, fmt.Errorf("Cannot load cert/key pair: %v", err)
 	}
 	srv.StartTLS()
-	return srv, nil
-}
 
-func (op *OIDCProvider) AddMinimalProviderConfig(srv *httptest.Server) {
+	// The issuer's URL is extended by an optional path. This ensures that the plugin can
+	// handle issuers that use a non-root path for discovery (see kubernetes/kubernetes#29749).
+	srv.URL = srv.URL + op.issuerPath
+
+	u, err := url.Parse(srv.URL)
+	if err != nil {
+		return nil, err
+	}
+	pathFor := func(p string) *url.URL {
+		u2 := *u // Shallow copy.
+		u2.Path = path.Join(u2.Path, p)
+		return &u2
+	}
+
 	op.PCFG = oidc.ProviderConfig{
-		Issuer:                  MustParseURL(srv.URL),
+		Issuer:                  u,
-		AuthEndpoint:            MustParseURL(srv.URL + "/auth"),
+		AuthEndpoint:            pathFor("/auth"),
-		TokenEndpoint:           MustParseURL(srv.URL + "/token"),
+		TokenEndpoint:           pathFor("/token"),
-		KeysEndpoint:            MustParseURL(srv.URL + "/keys"),
+		KeysEndpoint:            pathFor("/keys"),
 		ResponseTypesSupported:  []string{"code"},
 		SubjectTypesSupported:   []string{"public"},
 		IDTokenSigningAlgValues: []string{"RS256"},
 	}
-
+	return srv, nil
 }
 
 func (op *OIDCProvider) handleConfig(w http.ResponseWriter, req *http.Request) {
@@ -122,14 +136,6 @@ func (op *OIDCProvider) handleKeys(w http.ResponseWriter, req *http.Request) {
 	w.Write(b)
 }
 
-func MustParseURL(s string) *url.URL {
-	u, err := url.Parse(s)
-	if err != nil {
-		panic(fmt.Errorf("Failed to parse url: %v", err))
-	}
-	return u
-}
-
 // generateSelfSignedCert generates a self-signed cert/key pairs and writes to the certPath/keyPath.
 // This method is mostly identical to crypto.GenerateSelfSignedCert except for the 'IsCA' and 'KeyUsage'
 // in the certificate template. (Maybe we can merge these two methods).

plugin/pkg/client/auth/oidc/oidc_test.go

@@ -51,13 +51,12 @@ func TestNewOIDCAuthProvider(t *testing.T) {
 	defer os.Remove(tempDir)
 
 	oidctesting.GenerateSelfSignedCert(t, "127.0.0.1", cert, key)
-	op := oidctesting.NewOIDCProvider(t)
+	op := oidctesting.NewOIDCProvider(t, "")
 	srv, err := op.ServeTLSWithKeyPair(cert, key)
 	if err != nil {
 		t.Fatalf("Cannot start server %v", err)
 	}
 	defer srv.Close()
-	op.AddMinimalProviderConfig(srv)
 
 	certData, err := ioutil.ReadFile(cert)
 	if err != nil {