[#7252] support ed25519 oidc id_token signature validation

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 - Visualize presentable multiple `relation` fields ([#7260](https://github.com/pocketbase/pocketbase/issues/7260)).
 
+- Support Ed25519 in the optional OIDC id_token signature validation ([#7252](https://github.com/pocketbase/pocketbase/issues/7252); thanks @shynome).
+
 
 ## v0.30.4
 

tools/auth/internal/jwk/jwk.go

@@ -0,0 +1,120 @@
+// Package jwk implements some common utilities for interacting with JWKs
+// (mostly used with OIDC providers).
+package jwk
+
+import (
+	"context"
+	"crypto/ed25519"
+	"crypto/rsa"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"math/big"
+	"net/http"
+	"strings"
+)
+
+type JWK struct {
+	Kty string `json:"kty"`
+	Kid string `json:"kid"`
+	Use string `json:"use"`
+	Alg string `json:"alg"`
+	// RS256 (RSA)
+	E string `json:"e"`
+	N string `json:"n"`
+	// Ed25519 (OKP)
+	Crv string `json:"crv"`
+	X   string `json:"x"`
+}
+
+// PublicKey reconstructs and returns the public key from the current JWK.
+func (key *JWK) PublicKey() (any, error) {
+	switch key.Kty {
+	case "RSA":
+		// RFC 7518
+		// https://datatracker.ietf.org/doc/html/rfc7518#section-6.3
+		// https://datatracker.ietf.org/doc/html/rfc7517#appendix-A.1
+		exponent, err := base64.RawURLEncoding.DecodeString(strings.TrimRight(key.E, "="))
+		if err != nil {
+			return nil, err
+		}
+
+		modulus, err := base64.RawURLEncoding.DecodeString(strings.TrimRight(key.N, "="))
+		if err != nil {
+			return nil, err
+		}
+
+		return &rsa.PublicKey{
+			E: int(big.NewInt(0).SetBytes(exponent).Uint64()),
+			N: big.NewInt(0).SetBytes(modulus),
+		}, nil
+	case "OKP":
+		// RFC 8037
+		// https://datatracker.ietf.org/doc/html/rfc8037#section-2
+		// https://datatracker.ietf.org/doc/html/rfc8037#appendix-A
+		if key.Crv != "Ed25519" {
+			return nil, fmt.Errorf("unsupported OKP curve (must be Ed25519): %q", key.Crv)
+		}
+
+		x, err := base64.RawURLEncoding.DecodeString(strings.TrimRight(key.X, "="))
+		if err != nil {
+			return nil, err
+		}
+
+		if l := len(x); l != ed25519.PublicKeySize {
+			return nil, fmt.Errorf("invalid Ed25519 key length: %d", l)
+		}
+
+		return ed25519.PublicKey(x), nil
+	default:
+		return nil, fmt.Errorf("unsupported kty (must be RSA or OKP): %q", key.Kty)
+	}
+}
+
+// Fetch retrieves the JSON Web Key Set located at jwksURL and returns
+// the first key that matches the specified kid.
+func Fetch(ctx context.Context, jwksURL string, kid string) (*JWK, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", jwksURL, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+
+	rawBody, err := io.ReadAll(res.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	// http.Client.Get doesn't treat non 2xx responses as error
+	if res.StatusCode >= 400 {
+		return nil, fmt.Errorf(
+			"failed to JSON Web Key Set from %s (%d):\n%s",
+			jwksURL,
+			res.StatusCode,
+			string(rawBody),
+		)
+	}
+
+	jwks := struct {
+		Keys []*JWK
+	}{}
+
+	err = json.Unmarshal(rawBody, &jwks)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, key := range jwks.Keys {
+		if key.Kid == kid {
+			return key, nil
+		}
+	}
+
+	return nil, fmt.Errorf("jwk with kid %q was not found", kid)
+}

tools/auth/internal/jwk/jwk_test.go

@@ -0,0 +1,211 @@
+package jwk_test
+
+import (
+	"context"
+	"crypto"
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/rsa"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"math/big"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/pocketbase/pocketbase/tools/auth/internal/jwk"
+)
+
+type publicKey interface {
+	Equal(x crypto.PublicKey) bool
+}
+
+func TestJWK_PublicKey(t *testing.T) {
+	t.Parallel()
+
+	rsaPrivate, err := rsa.GenerateKey(rand.Reader, 1024)
+	if err != nil {
+		t.Fatalf("failed to generate test RSA private key: %v", err)
+	}
+
+	scenarios := []struct {
+		name        string
+		key         *jwk.JWK
+		expectError bool
+		expectKey   crypto.PublicKey
+	}{
+		{
+			"empty",
+			&jwk.JWK{},
+			true,
+			nil,
+		},
+		{
+			"invalid kty",
+			&jwk.JWK{
+				Kty: "invalid",
+				Alg: "RS256",
+				E:   base64.RawURLEncoding.EncodeToString(big.NewInt(int64(rsaPrivate.E)).Bytes()),
+				N:   base64.RawURLEncoding.EncodeToString(rsaPrivate.N.Bytes()),
+			},
+			true,
+			nil,
+		},
+		{
+			"RSA",
+			&jwk.JWK{
+				Kty: "RSA",
+				Alg: "RS256",
+				E:   base64.RawURLEncoding.EncodeToString(big.NewInt(int64(rsaPrivate.E)).Bytes()),
+				N:   base64.RawURLEncoding.EncodeToString(rsaPrivate.N.Bytes()),
+			},
+			false,
+			&rsaPrivate.PublicKey,
+		},
+		{
+			"OKP with unsupported curve",
+			&jwk.JWK{
+				Kty: "OKP",
+				Crv: "invalid",
+				X:   base64.RawURLEncoding.EncodeToString([]byte(strings.Repeat("a", ed25519.PublicKeySize))),
+			},
+			true,
+			nil,
+		},
+		{
+			"OKP with invalid public key length",
+			&jwk.JWK{
+				Kty: "OKP",
+				Crv: "Ed25519",
+				X:   base64.RawURLEncoding.EncodeToString([]byte(strings.Repeat("a", ed25519.PublicKeySize-1))),
+			},
+			true,
+			nil,
+		},
+		{
+			"valid OKP",
+			&jwk.JWK{
+				Kty: "OKP",
+				Crv: "Ed25519",
+				X:   base64.RawURLEncoding.EncodeToString([]byte(strings.Repeat("a", ed25519.PublicKeySize))),
+			},
+			false,
+			ed25519.PublicKey([]byte(strings.Repeat("a", ed25519.PublicKeySize))),
+		},
+	}
+
+	for _, s := range scenarios {
+		t.Run(s.name, func(t *testing.T) {
+			result, err := s.key.PublicKey()
+
+			hasErr := err != nil
+			if hasErr != s.expectError {
+				t.Fatalf("Expected hasErr %v, got %v (%v)", s.expectError, hasErr, err)
+			}
+
+			if hasErr && result == nil {
+				return
+			}
+
+			k, ok := result.(publicKey)
+			if !ok {
+				t.Fatalf("The returned public key %T doesn't satisfy the expected common interface", k)
+			}
+
+			if !k.Equal(s.expectKey) {
+				t.Fatalf("The returned public key doesn't match with the expected one:\n%v\n%v", k, s.expectKey)
+			}
+		})
+	}
+}
+
+func TestFetch(t *testing.T) {
+	t.Parallel()
+
+	server := httptest.NewServer(http.HandlerFunc(func(res http.ResponseWriter, req *http.Request) {
+		if req.URL.Query().Has("error") {
+			res.WriteHeader(http.StatusBadRequest)
+		}
+
+		fmt.Fprintf(res, `{
+			"keys": [
+				{
+					"kid": "abc",
+					"kty": "OKP",
+					"crv": "Ed25519",
+					"x":   "test_x"
+				},
+				{
+					"kid": "def",
+					"kty": "RSA",
+					"alg": "RS256",
+					"n":   "test_n",
+					"e":   "test_e"
+				}
+			]
+		}`)
+	}))
+	defer server.Close()
+
+	scenarios := []struct {
+		name        string
+		kid         string
+		expectError bool
+		contains    []string
+	}{
+		{
+			"error response",
+			"def",
+			true,
+			nil,
+		},
+		{
+			"non-matching kid",
+			"missing",
+			true,
+			nil,
+		},
+		{
+			"matching kid",
+			"def",
+			false,
+			[]string{
+				`"kid":"def"`,
+				`"kty":"RSA"`,
+				`"alg":"RS256"`,
+				`"n":"test_n"`,
+				`"e":"test_e"`,
+			},
+		},
+	}
+
+	for _, s := range scenarios {
+		t.Run(s.name, func(t *testing.T) {
+			url := server.URL
+			if s.expectError {
+				url += "?error"
+			}
+
+			key, err := jwk.Fetch(context.Background(), url, s.kid)
+
+			hasErr := err != nil
+			if hasErr != s.expectError {
+				t.Fatalf("Expected hasErr %v, got %v (%v)", s.expectError, hasErr, err)
+			}
+
+			raw, err := json.Marshal(key)
+			if err != nil {
+				t.Fatal(err)
+			}
+			rawStr := string(raw)
+
+			for _, substr := range s.contains {
+				if !strings.Contains(rawStr, substr) {
+					t.Fatalf("Missing expected substring\n%s\nin\n%s", substr, rawStr)
+				}
+			}
+		})
+	}
+}

tools/auth/oidc.go

@@ -2,20 +2,15 @@ package auth
 
 import (
 	"context"
-	"crypto/rsa"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io"
-	"math/big"
-	"net/http"
 	"os"
 	"strconv"
-	"strings"
 	"time"
 
 	"github.com/golang-jwt/jwt/v5"
+	"github.com/pocketbase/pocketbase/tools/auth/internal/jwk"
 	"github.com/pocketbase/pocketbase/tools/security"
 	"github.com/pocketbase/pocketbase/tools/types"
 	"github.com/spf13/cast"
@@ -198,36 +193,17 @@ func validateIdTokenSignature(ctx context.Context, idToken string, jwksURL strin
 		return errors.New("missing kid header value")
 	}
 
-	key, err := fetchJWK(ctx, jwksURL, kid)
+	key, err := jwk.Fetch(ctx, jwksURL, kid)
 	if err != nil {
 		return err
 	}
 
-	// decode the key params per RFC 7518 (https://tools.ietf.org/html/rfc7518#section-6.3)
-	// and construct a valid publicKey from them
-	// ---
-	exponent, err := base64.RawURLEncoding.DecodeString(strings.TrimRight(key.E, "="))
-	if err != nil {
-		return err
-	}
-
-	modulus, err := base64.RawURLEncoding.DecodeString(strings.TrimRight(key.N, "="))
-	if err != nil {
-		return err
-	}
-
-	publicKey := &rsa.PublicKey{
-		// https://tools.ietf.org/html/rfc7517#appendix-A.1
-		E: int(big.NewInt(0).SetBytes(exponent).Uint64()),
-		N: big.NewInt(0).SetBytes(modulus),
-	}
-
 	// verify the signiture
 	// ---
 	parser := jwt.NewParser(jwt.WithValidMethods([]string{key.Alg}))
 
 	parsedToken, err := parser.Parse(idToken, func(t *jwt.Token) (any, error) {
-		return publicKey, nil
+		return key.PublicKey()
 	})
 	if err != nil {
 		return err
@@ -239,54 +215,3 @@ func validateIdTokenSignature(ctx context.Context, idToken string, jwksURL strin
 
 	return nil
 }
-
-type jwk struct {
-	Kty string
-	Kid string
-	Use string
-	Alg string
-	N   string
-	E   string
-}
-
-func fetchJWK(ctx context.Context, jwksURL string, kid string) (*jwk, error) {
-	req, err := http.NewRequestWithContext(ctx, "GET", jwksURL, nil)
-	if err != nil {
-		return nil, err
-	}
-
-	res, err := http.DefaultClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer res.Body.Close()
-
-	rawBody, err := io.ReadAll(res.Body)
-	if err != nil {
-		return nil, err
-	}
-
-	// http.Client.Get doesn't treat non 2xx responses as error
-	if res.StatusCode >= 400 {
-		return nil, fmt.Errorf(
-			"failed to verify the provided id_token (%d):\n%s",
-			res.StatusCode,
-			string(rawBody),
-		)
-	}
-
-	jwks := struct {
-		Keys []*jwk
-	}{}
-	if err := json.Unmarshal(rawBody, &jwks); err != nil {
-		return nil, err
-	}
-
-	for _, key := range jwks.Keys {
-		if key.Kid == kid {
-			return key, nil
-		}
-	}
-
-	return nil, fmt.Errorf("jwk with kid %q was not found", kid)
-}