Verify OAuth2 ID tokens before trusting claims
The compliance portal OAuth callback accepted ID tokens after only parsing claims, without checking the signature, issuer, audience, or expiry. Add RS256 verification helpers to the JOSE package, enforce those checks in ParseIDTokenIdentity, and thread JWKS, issuer, and client ID through the token response and callback handler. Signed-off-by: Bryan Frimin <bryan@probo.com>
This commit is contained in:
Bryan Frimin
@@ -29,6 +29,7 @@ import (
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"encoding/json"
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"fmt"
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"math/big"
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"strings"
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)
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type (
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@@ -103,3 +104,106 @@ func SignJWT(privateKey *rsa.PrivateKey, kid string, claims any) (string, error)
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return signingInput + "." + signatureB64, nil
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}
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// RSAPublicKeyFromJWK reconstructs an RSA public key from a JWK.
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func RSAPublicKeyFromJWK(jwk JWK) (*rsa.PublicKey, error) {
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if jwk.KeyType != "RSA" {
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return nil, fmt.Errorf("cannot convert jwk to rsa public key: unsupported key type %q", jwk.KeyType)
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}
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nBytes, err := base64.RawURLEncoding.DecodeString(jwk.N)
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if err != nil {
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return nil, fmt.Errorf("cannot decode rsa modulus: %w", err)
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}
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eBytes, err := base64.RawURLEncoding.DecodeString(jwk.E)
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if err != nil {
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return nil, fmt.Errorf("cannot decode rsa exponent: %w", err)
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}
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return &rsa.PublicKey{
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N: new(big.Int).SetBytes(nBytes),
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E: int(new(big.Int).SetBytes(eBytes).Int64()),
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}, nil
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}
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// PublicKeyFromJWKS returns the RSA public key matching the given key ID.
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func PublicKeyFromJWKS(jwks *JWKS, kid string) (*rsa.PublicKey, error) {
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for _, key := range jwks.Keys {
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if key.KeyID == kid {
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return RSAPublicKeyFromJWK(key)
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}
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}
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return nil, fmt.Errorf("cannot find signing key %q in jwks", kid)
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}
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// VerifyJWT verifies an RS256 JWT signature and returns the decoded payload.
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func VerifyJWT(raw string, pubKey *rsa.PublicKey) ([]byte, error) {
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parts := strings.Split(raw, ".")
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if len(parts) != 3 {
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return nil, fmt.Errorf("cannot verify jwt: invalid format")
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}
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headerJSON, err := base64.RawURLEncoding.DecodeString(parts[0])
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if err != nil {
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return nil, fmt.Errorf("cannot decode jwt header: %w", err)
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}
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var header JWTHeader
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if err := json.Unmarshal(headerJSON, &header); err != nil {
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return nil, fmt.Errorf("cannot parse jwt header: %w", err)
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}
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if header.Algorithm != "RS256" {
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return nil, fmt.Errorf("cannot verify jwt: unsupported algorithm %q", header.Algorithm)
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}
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payload, err := base64.RawURLEncoding.DecodeString(parts[1])
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if err != nil {
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return nil, fmt.Errorf("cannot decode jwt payload: %w", err)
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}
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signature, err := base64.RawURLEncoding.DecodeString(parts[2])
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if err != nil {
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return nil, fmt.Errorf("cannot decode jwt signature: %w", err)
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}
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signedContent := parts[0] + "." + parts[1]
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hash := sha256.Sum256([]byte(signedContent))
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if err := rsa.VerifyPKCS1v15(pubKey, crypto.SHA256, hash[:], signature); err != nil {
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return nil, fmt.Errorf("cannot verify jwt signature: %w", err)
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}
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return payload, nil
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}
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// VerifyJWTWithJWKS verifies an RS256 JWT using the matching key from a JWKS.
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func VerifyJWTWithJWKS(raw string, jwks *JWKS) ([]byte, error) {
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parts := strings.Split(raw, ".")
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if len(parts) != 3 {
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return nil, fmt.Errorf("cannot verify jwt: invalid format")
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}
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headerJSON, err := base64.RawURLEncoding.DecodeString(parts[0])
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if err != nil {
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return nil, fmt.Errorf("cannot decode jwt header: %w", err)
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}
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var header JWTHeader
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if err := json.Unmarshal(headerJSON, &header); err != nil {
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return nil, fmt.Errorf("cannot parse jwt header: %w", err)
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}
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if header.KeyID == "" {
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return nil, fmt.Errorf("cannot verify jwt: missing key id")
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}
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pubKey, err := PublicKeyFromJWKS(jwks, header.KeyID)
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if err != nil {
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return nil, err
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}
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return VerifyJWT(raw, pubKey)
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}
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@@ -297,3 +297,266 @@ func TestJWTHeader_JSON(t *testing.T) {
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},
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)
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}
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func TestRSAPublicKeyFromJWK(t *testing.T) {
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t.Parallel()
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key := testRSAKey(t)
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jwk := jose.RSAPublicKeyToJWK(&key.PublicKey, "kid-1")
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t.Run(
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"round trips rsa public key",
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func(t *testing.T) {
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t.Parallel()
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pubKey, err := jose.RSAPublicKeyFromJWK(jwk)
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require.NoError(t, err)
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assert.Equal(t, key.N, pubKey.N)
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assert.Equal(t, key.E, pubKey.E)
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},
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)
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t.Run(
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"rejects unsupported key type",
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func(t *testing.T) {
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t.Parallel()
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_, err := jose.RSAPublicKeyFromJWK(jose.JWK{KeyType: "EC"})
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require.Error(t, err)
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},
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)
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}
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func TestPublicKeyFromJWKS(t *testing.T) {
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t.Parallel()
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key := testRSAKey(t)
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jwks := &jose.JWKS{
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Keys: []jose.JWK{
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jose.RSAPublicKeyToJWK(&key.PublicKey, "kid-1"),
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jose.RSAPublicKeyToJWK(&key.PublicKey, "kid-2"),
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},
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}
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t.Run(
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"finds matching key",
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func(t *testing.T) {
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t.Parallel()
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pubKey, err := jose.PublicKeyFromJWKS(jwks, "kid-2")
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require.NoError(t, err)
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assert.Equal(t, key.E, pubKey.E)
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},
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)
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t.Run(
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"errors when kid is missing",
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func(t *testing.T) {
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t.Parallel()
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_, err := jose.PublicKeyFromJWKS(jwks, "missing")
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require.Error(t, err)
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},
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)
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}
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func TestVerifyJWT(t *testing.T) {
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t.Parallel()
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key := testRSAKey(t)
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t.Run(
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"verifies signed jwt",
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func(t *testing.T) {
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t.Parallel()
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claims := map[string]string{"sub": "test"}
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token, err := jose.SignJWT(key, "kid-1", claims)
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require.NoError(t, err)
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payload, err := jose.VerifyJWT(token, &key.PublicKey)
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require.NoError(t, err)
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var decoded map[string]string
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err = json.Unmarshal(payload, &decoded)
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require.NoError(t, err)
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assert.Equal(t, "test", decoded["sub"])
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},
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)
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t.Run(
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"rejects malformed jwt",
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func(t *testing.T) {
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t.Parallel()
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_, err := jose.VerifyJWT("", &key.PublicKey)
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require.Error(t, err)
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_, err = jose.VerifyJWT("only-one-part", &key.PublicKey)
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require.Error(t, err)
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_, err = jose.VerifyJWT("two.parts", &key.PublicKey)
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require.Error(t, err)
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_, err = jose.VerifyJWT("too.many.parts.here", &key.PublicKey)
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require.Error(t, err)
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},
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)
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t.Run(
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"rejects tampered payload",
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func(t *testing.T) {
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t.Parallel()
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token, err := jose.SignJWT(key, "kid-1", map[string]string{"sub": "test"})
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require.NoError(t, err)
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parts := strings.Split(token, ".")
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parts[1] = base64.RawURLEncoding.EncodeToString([]byte(`{"sub":"evil"}`))
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tampered := strings.Join(parts, ".")
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_, err = jose.VerifyJWT(tampered, &key.PublicKey)
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require.Error(t, err)
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},
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)
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t.Run(
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"rejects tampered header",
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func(t *testing.T) {
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t.Parallel()
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token, err := jose.SignJWT(key, "kid-1", map[string]string{"sub": "test"})
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require.NoError(t, err)
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parts := strings.Split(token, ".")
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parts[0] = base64.RawURLEncoding.EncodeToString([]byte(`{"alg":"HS256","typ":"JWT","kid":"kid-1"}`))
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tampered := strings.Join(parts, ".")
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_, err = jose.VerifyJWT(tampered, &key.PublicKey)
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require.Error(t, err)
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},
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)
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t.Run(
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"rejects unsupported algorithm",
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func(t *testing.T) {
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t.Parallel()
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cases := []struct {
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name string
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alg string
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}{
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{name: "hs256", alg: "HS256"},
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{name: "none", alg: "none"},
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{name: "lowercase rs256", alg: "rs256"},
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}
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for _, tc := range cases {
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t.Run(
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tc.name,
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func(t *testing.T) {
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t.Parallel()
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header := base64.RawURLEncoding.EncodeToString(
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[]byte(`{"alg":"` + tc.alg + `","typ":"JWT","kid":"kid-1"}`),
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)
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payload := base64.RawURLEncoding.EncodeToString([]byte(`{"sub":"test"}`))
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token := header + "." + payload + ".c2ln"
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_, err := jose.VerifyJWT(token, &key.PublicKey)
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require.Error(t, err)
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},
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)
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}
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},
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)
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t.Run(
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"rejects signature from different key",
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func(t *testing.T) {
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t.Parallel()
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otherKey := testRSAKey(t)
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token, err := jose.SignJWT(otherKey, "kid-1", map[string]string{"sub": "test"})
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require.NoError(t, err)
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_, err = jose.VerifyJWT(token, &key.PublicKey)
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require.Error(t, err)
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},
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)
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}
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func TestVerifyJWTWithJWKS(t *testing.T) {
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t.Parallel()
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key := testRSAKey(t)
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jwks := &jose.JWKS{
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Keys: []jose.JWK{
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jose.RSAPublicKeyToJWK(&key.PublicKey, "kid-1"),
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},
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}
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t.Run(
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"verifies signed jwt",
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func(t *testing.T) {
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t.Parallel()
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token, err := jose.SignJWT(key, "kid-1", map[string]string{"sub": "test"})
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require.NoError(t, err)
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payload, err := jose.VerifyJWTWithJWKS(token, jwks)
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require.NoError(t, err)
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var decoded map[string]string
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err = json.Unmarshal(payload, &decoded)
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require.NoError(t, err)
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assert.Equal(t, "test", decoded["sub"])
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},
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)
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t.Run(
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"rejects missing key id",
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func(t *testing.T) {
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t.Parallel()
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header := base64.RawURLEncoding.EncodeToString([]byte(`{"alg":"RS256","typ":"JWT"}`))
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payload := base64.RawURLEncoding.EncodeToString([]byte(`{"sub":"test"}`))
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token := header + "." + payload + ".c2ln"
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_, err := jose.VerifyJWTWithJWKS(token, jwks)
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require.Error(t, err)
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},
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)
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t.Run(
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"rejects unknown key id",
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func(t *testing.T) {
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t.Parallel()
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token, err := jose.SignJWT(key, "unknown-kid", map[string]string{"sub": "test"})
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require.NoError(t, err)
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_, err = jose.VerifyJWTWithJWKS(token, jwks)
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require.Error(t, err)
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},
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)
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t.Run(
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"rejects token signed with key outside jwks",
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func(t *testing.T) {
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t.Parallel()
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otherKey := testRSAKey(t)
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token, err := jose.SignJWT(otherKey, "kid-1", map[string]string{"sub": "test"})
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require.NoError(t, err)
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_, err = jose.VerifyJWTWithJWKS(token, jwks)
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require.Error(t, err)
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},
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)
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}
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Reference in New Issue
Block a user