Remove the deprecated RFC7523OAuthClientProvider

maxisbey · maxisbey · commit aeb0a57a6154 · 2026-07-25T19:49:23.000Z
The provider implemented the RFC 7523 §2.1 jwt-bearer authorization grant
with an SDK-minted or prebuilt JWT, which no MCP auth extension specifies,
and has been deprecated since 1.23.0 in favour of ClientCredentialsOAuthProvider,
PrivateKeyJWTOAuthProvider, and IdentityAssertionOAuthProvider. Drop it and its
JWTParameters model ahead of v2, with a migration entry mapping each of its
modes to a replacement.
diff --git a/docs/migration.md b/docs/migration.md
@@ -1920,6 +1920,32 @@ The WebSocket transport has been removed: `mcp.client.websocket.websocket_client
 
 ## OAuth and server auth
 
+### `RFC7523OAuthClientProvider` and `JWTParameters` removed
+
+`RFC7523OAuthClientProvider` (deprecated since 1.23.0) and its `JWTParameters` model have been
+removed from `mcp.client.auth.extensions.client_credentials`. The provider implemented the
+[RFC 7523](https://datatracker.ietf.org/doc/html/rfc7523) §2.1 `jwt-bearer` *authorization grant*
+with an SDK-minted or prebuilt JWT, which no MCP auth extension specifies. Replace it with the
+purpose-built provider for the flow you actually run:
+
+- Machine-to-machine with a client secret
+  ([`io.modelcontextprotocol/oauth-client-credentials`](https://modelcontextprotocol.io/extensions/auth/oauth-client-credentials)):
+  `ClientCredentialsOAuthProvider(server_url, storage, client_id, client_secret)`.
+- Machine-to-machine authenticating with a JWT instead of a secret (same extension, RFC 7523 §2.2
+  `private_key_jwt` client authentication on the `client_credentials` grant, which is the mode the
+  extension actually specifies for JWTs): `PrivateKeyJWTOAuthProvider(server_url, storage,
+  client_id, assertion_provider)`. Build the assertion with `SignedJWTParameters(issuer, subject,
+  signing_key).create_assertion_provider()` (replaces `JWTParameters` signing fields), or wrap a
+  prebuilt JWT with `static_assertion_provider(token)` (replaces `JWTParameters(assertion=...)`).
+- Presenting an enterprise ID-JAG under the `jwt-bearer` grant
+  ([SEP-990](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/990)):
+  `IdentityAssertionOAuthProvider` in `mcp.client.auth.extensions.identity_assertion`.
+
+The provider's third mode — the interactive `authorization_code` flow with `private_key_jwt`
+client authentication on the token exchange — has no replacement and is intentionally dropped; it
+was never exercised by the test suite and no MCP auth extension specifies it. If you depended on
+it, open an issue describing the deployment.
+
 ### OAuth metadata URLs no longer gain a trailing slash
 
 `OAuthMetadata`, `ProtectedResourceMetadata`, and `OAuthClientMetadata` now set
diff --git a/src/mcp/client/auth/extensions/client_credentials.py b/src/mcp/client/auth/extensions/client_credentials.py
@@ -4,11 +4,9 @@
 - ClientCredentialsOAuthProvider: For client_credentials with client_id + client_secret
 - PrivateKeyJWTOAuthProvider: For client_credentials with private_key_jwt authentication
   (typically using a pre-built JWT from workload identity federation)
-- RFC7523OAuthClientProvider: For jwt-bearer grant (RFC 7523 Section 2.1)
 """
 
 import time
-import warnings
 from collections.abc import Awaitable, Callable
 from typing import Any, Literal
 from uuid import uuid4
@@ -17,9 +15,8 @@
 import jwt
 from pydantic import BaseModel, Field
 
-from mcp.client.auth import OAuthClientProvider, OAuthFlowError, OAuthTokenError, TokenStorage
-from mcp.shared.auth import AuthorizationCodeResult, OAuthClientInformationFull, OAuthClientMetadata
-from mcp.shared.exceptions import MCPDeprecationWarning
+from mcp.client.auth import OAuthClientProvider, OAuthFlowError, TokenStorage
+from mcp.shared.auth import OAuthClientInformationFull, OAuthClientMetadata
 
 
 class ClientCredentialsOAuthProvider(OAuthClientProvider):
@@ -334,153 +331,3 @@ async def _exchange_token_client_credentials(self) -> httpx2.Request:
 
         token_url = self._get_token_endpoint()
         return httpx2.Request("POST", token_url, data=token_data, headers=headers)
-
-
-class JWTParameters(BaseModel):
-    """JWT parameters."""
-
-    assertion: str | None = Field(
-        default=None,
-        description="JWT assertion for JWT authentication. "
-        "Will be used instead of generating a new assertion if provided.",
-    )
-
-    issuer: str | None = Field(default=None, description="Issuer for JWT assertions.")
-    subject: str | None = Field(default=None, description="Subject identifier for JWT assertions.")
-    audience: str | None = Field(default=None, description="Audience for JWT assertions.")
-    claims: dict[str, Any] | None = Field(default=None, description="Additional claims for JWT assertions.")
-    jwt_signing_algorithm: str | None = Field(default="RS256", description="Algorithm for signing JWT assertions.")
-    jwt_signing_key: str | None = Field(default=None, description="Private key for JWT signing.")
-    jwt_lifetime_seconds: int = Field(default=300, description="Lifetime of generated JWT in seconds.")
-
-    def to_assertion(self, with_audience_fallback: str | None = None) -> str:
-        if self.assertion is not None:
-            # Prebuilt JWT (e.g. acquired out-of-band)
-            assertion = self.assertion
-        else:
-            if not self.jwt_signing_key:
-                raise OAuthFlowError("Missing signing key for JWT bearer grant")  # pragma: no cover
-            if not self.issuer:
-                raise OAuthFlowError("Missing issuer for JWT bearer grant")  # pragma: no cover
-            if not self.subject:
-                raise OAuthFlowError("Missing subject for JWT bearer grant")  # pragma: no cover
-
-            audience = self.audience if self.audience else with_audience_fallback
-            if not audience:
-                raise OAuthFlowError("Missing audience for JWT bearer grant")  # pragma: no cover
-
-            now = int(time.time())
-            claims: dict[str, Any] = {
-                "iss": self.issuer,
-                "sub": self.subject,
-                "aud": audience,
-                "exp": now + self.jwt_lifetime_seconds,
-                "iat": now,
-                "jti": str(uuid4()),
-            }
-            claims.update(self.claims or {})
-
-            assertion = jwt.encode(
-                claims,
-                self.jwt_signing_key,
-                algorithm=self.jwt_signing_algorithm or "RS256",
-            )
-        return assertion
-
-
-class RFC7523OAuthClientProvider(OAuthClientProvider):
-    """OAuth client provider for RFC 7523 jwt-bearer grant.
-
-    .. deprecated::
-        Use :class:`ClientCredentialsOAuthProvider` for client_credentials with
-        client_id + client_secret, or :class:`PrivateKeyJWTOAuthProvider` for
-        client_credentials with private_key_jwt authentication instead.
-
-    This provider supports the jwt-bearer authorization grant (RFC 7523 Section 2.1)
-    where the JWT itself is the authorization grant.
-    """
-
-    def __init__(
-        self,
-        server_url: str,
-        client_metadata: OAuthClientMetadata,
-        storage: TokenStorage,
-        redirect_handler: Callable[[str], Awaitable[None]] | None = None,
-        callback_handler: Callable[[], Awaitable[AuthorizationCodeResult]] | None = None,
-        timeout: float = 300.0,
-        jwt_parameters: JWTParameters | None = None,
-    ) -> None:
-        warnings.warn(
-            "RFC7523OAuthClientProvider is deprecated. Use ClientCredentialsOAuthProvider "
-            "or PrivateKeyJWTOAuthProvider instead.",
-            MCPDeprecationWarning,
-            stacklevel=2,
-        )
-        super().__init__(server_url, client_metadata, storage, redirect_handler, callback_handler, timeout)
-        self.jwt_parameters = jwt_parameters
-
-    async def _exchange_token_authorization_code(
-        self, auth_code: str, code_verifier: str, *, token_data: dict[str, Any] | None = None
-    ) -> httpx2.Request:  # pragma: no cover
-        """Build token exchange request for authorization_code flow."""
-        token_data = token_data or {}
-        if self.context.client_metadata.token_endpoint_auth_method == "private_key_jwt":
-            self._add_client_authentication_jwt(token_data=token_data)
-        return await super()._exchange_token_authorization_code(auth_code, code_verifier, token_data=token_data)
-
-    async def _perform_authorization(self) -> httpx2.Request:  # pragma: no cover
-        """Perform the authorization flow."""
-        if "urn:ietf:params:oauth:grant-type:jwt-bearer" in self.context.client_metadata.grant_types:
-            token_request = await self._exchange_token_jwt_bearer()
-            return token_request
-        else:
-            return await super()._perform_authorization()
-
-    def _add_client_authentication_jwt(self, *, token_data: dict[str, Any]):  # pragma: no cover
-        """Add JWT assertion for client authentication to token endpoint parameters."""
-        if not self.jwt_parameters:
-            raise OAuthTokenError("Missing JWT parameters for private_key_jwt flow")
-        if not self.context.oauth_metadata:
-            raise OAuthTokenError("Missing OAuth metadata for private_key_jwt flow")
-
-        # We need to set the audience to the issuer identifier of the authorization server
-        # https://datatracker.ietf.org/doc/html/draft-ietf-oauth-rfc7523bis-01#name-updates-to-rfc-7523
-        issuer = str(self.context.oauth_metadata.issuer)
-        assertion = self.jwt_parameters.to_assertion(with_audience_fallback=issuer)
-
-        # When using private_key_jwt, in a client_credentials flow, we use RFC 7523 Section 2.2
-        token_data["client_assertion"] = assertion
-        token_data["client_assertion_type"] = "urn:ietf:params:oauth:client-assertion-type:jwt-bearer"
-        # We need to set the audience to the resource server, the audience is different from the one in claims
-        # it represents the resource server that will validate the token
-        token_data["audience"] = self.context.get_resource_url()
-
-    async def _exchange_token_jwt_bearer(self) -> httpx2.Request:
-        """Build token exchange request for JWT bearer grant."""
-        if not self.context.client_info:
-            raise OAuthFlowError("Missing client info")  # pragma: no cover
-        if not self.jwt_parameters:
-            raise OAuthFlowError("Missing JWT parameters")  # pragma: no cover
-        if not self.context.oauth_metadata:
-            raise OAuthTokenError("Missing OAuth metadata")  # pragma: no cover
-
-        # We need to set the audience to the issuer identifier of the authorization server
-        # https://datatracker.ietf.org/doc/html/draft-ietf-oauth-rfc7523bis-01#name-updates-to-rfc-7523
-        issuer = str(self.context.oauth_metadata.issuer)
-        assertion = self.jwt_parameters.to_assertion(with_audience_fallback=issuer)
-
-        token_data = {
-            "grant_type": "urn:ietf:params:oauth:grant-type:jwt-bearer",
-            "assertion": assertion,
-        }
-
-        if self.context.should_include_resource_param(self.context.protocol_version):  # pragma: no branch
-            token_data["resource"] = self.context.get_resource_url()
-
-        if self.context.client_metadata.scope:  # pragma: no branch
-            token_data["scope"] = self.context.client_metadata.scope
-
-        token_url = self._get_token_endpoint()
-        return httpx2.Request(
-            "POST", token_url, data=token_data, headers={"Content-Type": "application/x-www-form-urlencoded"}
-        )
diff --git a/tests/client/auth/extensions/test_client_credentials.py b/tests/client/auth/extensions/test_client_credentials.py
@@ -1,26 +1,20 @@
 import urllib.parse
-import warnings
 
 import jwt
 import pytest
-from pydantic import AnyHttpUrl, AnyUrl
+from pydantic import AnyHttpUrl
 
 from mcp.client.auth.extensions.client_credentials import (
     ClientCredentialsOAuthProvider,
-    JWTParameters,
     PrivateKeyJWTOAuthProvider,
-    RFC7523OAuthClientProvider,
     SignedJWTParameters,
     static_assertion_provider,
 )
 from mcp.shared.auth import (
-    AuthorizationCodeResult,
     OAuthClientInformationFull,
-    OAuthClientMetadata,
     OAuthMetadata,
     OAuthToken,
 )
-from mcp.shared.exceptions import MCPDeprecationWarning
 
 
 class MockTokenStorage:
@@ -48,138 +42,6 @@ def mock_storage():
     return MockTokenStorage()
 
 
-@pytest.fixture
-def client_metadata():
-    return OAuthClientMetadata(
-        client_name="Test Client",
-        client_uri=AnyHttpUrl("https://example.com"),
-        redirect_uris=[AnyUrl("http://localhost:3030/callback")],
-        scope="read write",
-    )
-
-
-@pytest.fixture
-def rfc7523_oauth_provider(client_metadata: OAuthClientMetadata, mock_storage: MockTokenStorage):
-    async def redirect_handler(url: str) -> None:  # pragma: no cover
-        """Mock redirect handler."""
-        pass
-
-    async def callback_handler() -> AuthorizationCodeResult:  # pragma: no cover
-        """Mock callback handler."""
-        return AuthorizationCodeResult(code="test_auth_code", state="test_state")
-
-    with warnings.catch_warnings():
-        warnings.simplefilter("ignore", MCPDeprecationWarning)
-        return RFC7523OAuthClientProvider(
-            server_url="https://api.example.com/v1/mcp",
-            client_metadata=client_metadata,
-            storage=mock_storage,
-            redirect_handler=redirect_handler,
-            callback_handler=callback_handler,
-        )
-
-
-class TestOAuthFlowClientCredentials:
-    """Test OAuth flow behavior for client credentials flows."""
-
-    @pytest.mark.anyio
-    async def test_token_exchange_request_jwt_predefined(self, rfc7523_oauth_provider: RFC7523OAuthClientProvider):
-        """Test token exchange request building with a predefined JWT assertion."""
-        # Set up required context
-        rfc7523_oauth_provider.context.client_info = OAuthClientInformationFull(
-            grant_types=["urn:ietf:params:oauth:grant-type:jwt-bearer"],
-            token_endpoint_auth_method="private_key_jwt",
-            redirect_uris=None,
-            scope="read write",
-        )
-        rfc7523_oauth_provider.context.oauth_metadata = OAuthMetadata(
-            issuer=AnyHttpUrl("https://api.example.com"),
-            authorization_endpoint=AnyHttpUrl("https://api.example.com/authorize"),
-            token_endpoint=AnyHttpUrl("https://api.example.com/token"),
-            registration_endpoint=AnyHttpUrl("https://api.example.com/register"),
-        )
-        rfc7523_oauth_provider.context.client_metadata = rfc7523_oauth_provider.context.client_info
-        rfc7523_oauth_provider.context.protocol_version = "2025-06-18"
-        rfc7523_oauth_provider.jwt_parameters = JWTParameters(
-            # https://www.jwt.io
-            assertion="eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWUsImlhdCI6MTUxNjIzOTAyMn0.KMUFsIDTnFmyG3nMiGM6H9FNFUROf3wh7SmqJp-QV30"
-        )
-
-        request = await rfc7523_oauth_provider._exchange_token_jwt_bearer()
-
-        assert request.method == "POST"
-        assert str(request.url) == "https://api.example.com/token"
-        assert request.headers["Content-Type"] == "application/x-www-form-urlencoded"
-
-        # Check form data
-        content = urllib.parse.unquote_plus(request.content.decode())
-        assert "grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer" in content
-        assert "scope=read write" in content
-        assert "resource=https://api.example.com/v1/mcp" in content
-        assert (
-            "assertion=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiYWRtaW4iOnRydWUsImlhdCI6MTUxNjIzOTAyMn0.KMUFsIDTnFmyG3nMiGM6H9FNFUROf3wh7SmqJp-QV30"
-            in content
-        )
-
-    @pytest.mark.anyio
-    async def test_token_exchange_request_jwt(self, rfc7523_oauth_provider: RFC7523OAuthClientProvider):
-        """Test token exchange request building wiith a generated JWT assertion."""
-        # Set up required context
-        rfc7523_oauth_provider.context.client_info = OAuthClientInformationFull(
-            grant_types=["urn:ietf:params:oauth:grant-type:jwt-bearer"],
-            token_endpoint_auth_method="private_key_jwt",
-            redirect_uris=None,
-            scope="read write",
-        )
-        rfc7523_oauth_provider.context.oauth_metadata = OAuthMetadata(
-            issuer=AnyHttpUrl("https://api.example.com"),
-            authorization_endpoint=AnyHttpUrl("https://api.example.com/authorize"),
-            token_endpoint=AnyHttpUrl("https://api.example.com/token"),
-            registration_endpoint=AnyHttpUrl("https://api.example.com/register"),
-        )
-        rfc7523_oauth_provider.context.client_metadata = rfc7523_oauth_provider.context.client_info
-        rfc7523_oauth_provider.context.protocol_version = "2025-06-18"
-        rfc7523_oauth_provider.jwt_parameters = JWTParameters(
-            issuer="foo",
-            subject="1234567890",
-            claims={
-                "name": "John Doe",
-                "admin": True,
-                "iat": 1516239022,
-            },
-            jwt_signing_algorithm="HS256",
-            jwt_signing_key="a-string-secret-at-least-256-bits-long",
-            jwt_lifetime_seconds=300,
-        )
-
-        request = await rfc7523_oauth_provider._exchange_token_jwt_bearer()
-
-        assert request.method == "POST"
-        assert str(request.url) == "https://api.example.com/token"
-        assert request.headers["Content-Type"] == "application/x-www-form-urlencoded"
-
-        # Check form data
-        content = urllib.parse.unquote_plus(request.content.decode()).split("&")
-        assert "grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer" in content
-        assert "scope=read write" in content
-        assert "resource=https://api.example.com/v1/mcp" in content
-
-        # Check assertion
-        assertion = next(param for param in content if param.startswith("assertion="))[len("assertion=") :]
-        claims = jwt.decode(
-            assertion,
-            key="a-string-secret-at-least-256-bits-long",
-            algorithms=["HS256"],
-            audience="https://api.example.com/",
-            subject="1234567890",
-            issuer="foo",
-            verify=True,
-        )
-        assert claims["name"] == "John Doe"
-        assert claims["admin"]
-        assert claims["iat"] == 1516239022
-
-
 class TestClientCredentialsOAuthProvider:
     """Test ClientCredentialsOAuthProvider."""
 
diff --git a/tests/docs_src/test_oauth_clients.py b/tests/docs_src/test_oauth_clients.py
