Workload Identity

docs/admin/guides/_SUMMARY.md

@@ -3,6 +3,7 @@
     * [Using external service](auth/external.md)
     * [Using Keycloak](auth/keycloak.md)
     * [Using JSON Header](auth/json_header.md)
+    * [Using Workload Identity](auth/workload_identity.md)
     * auth/*.md
 * Configuration
     * [Introduction](configure-pulp/index.md)

docs/admin/guides/auth/workload_identity.md

@@ -0,0 +1,109 @@
+# Workload Identity Authentication
+
+A CI job can authenticate to Pulp with a short-lived OIDC token from a third-party provider (for example GitHub Actions),
+instead of a stored username and password.
+The token is verified against the provider's public keys,
+its claims are matched against a set of rules,
+and the request is granted roles for that request only.
+No user is created and nothing is written to the role tables.
+
+This suits supply-chain workflows where a pipeline pushes content
+and you want its permissions scoped to specific repositories without long-lived secrets.
+
+!!! note
+    The token is an OIDC token,
+    but this is unrelated to the user-facing SSO login covered in [Using external service](external.md).
+    It identifies a workload, not a person.
+
+## How it works
+
+On each request the token is read from the `Authorization: Bearer` header.
+The `iss` claim selects a configured provider,
+the signature is verified against the provider's JWKS,
+and `iss`, `aud` and `exp` are checked.
+The remaining claims are matched against the provider's rules to compute the roles and scopes for the request.
+A token that matches no rule is rejected with a 401.
+
+## Enabling
+
+Add the authentication class to `DEFAULT_AUTHENTICATION_CLASSES`,
+then populate `WORKLOAD_IDENTITY`:
+
+```python title="settings.py"
+REST_FRAMEWORK["DEFAULT_AUTHENTICATION_CLASSES"] = [
+    "pulpcore.app.workload_identity.authentication.WorkloadIdentityAuthentication",
+    "pulpcore.app.authentication.BasicAuthentication",
+    "rest_framework.authentication.SessionAuthentication",
+]
+```
+
+No change to `AUTHENTICATION_BACKENDS` is needed.
+The feature stays off while `WORKLOAD_IDENTITY` is empty,
+so adding the class alone changes nothing.
+
+With the example below,
+a push from the `main` branch of `my-org/app` is granted the `file.filerepository_owner` role on the repository named `prod`,
+and nothing else.
+See the configuration reference at the end for every option.
+
+## Roles for asynchronous tasks
+
+Operations that dispatch a task, such as a sync, return a task the client polls.
+A workload identity request is not a database user,
+so it is not automatically granted a role on the tasks it creates.
+Grant a role carrying `core.view_task` when the CI needs to read its own tasks.
+
+## Configuration reference
+
+Every option of the `WORKLOAD_IDENTITY` setting, annotated:
+
+```python title="settings.py"
+WORKLOAD_IDENTITY = {
+    # How matching rules combine.
+    # "union" (default) collects the grants of every matching rule.
+    # "first-match" stops at the first matching rule.
+    "strategy": "union",
+
+    # One entry per trusted provider. The key is a name for your own reference.
+    "providers": {
+        "github": {
+            # Required. Expected "iss" claim. Selects the provider and is verified while decoding.
+            "issuer": "https://token.actions.githubusercontent.com",
+
+            # Required. URL of the provider's JWKS. Keys are fetched and cached.
+            "jwks_url": "https://token.actions.githubusercontent.com/.well-known/jwks",
+
+            # Required. Expected "aud" claim.
+            "audience": "https://pulp.example.com",
+
+            # Optional. Allowed signing algorithms. Default: ["RS256"].
+            "algorithms": ["RS256"],
+
+            # Rules are evaluated in order. Each maps claims to grants.
+            "rules": [
+                {
+                    # Claim name to expected value. Values support "*" globbing.
+                    # Every entry must match (AND). A missing claim never matches.
+                    "match": {"repository": "my-org/app", "ref": "refs/heads/main"},
+
+                    # Grants awarded when the rule matches.
+                    "grants": [
+                        {
+                            # Required. Name of a role that already exists in Pulp.
+                            # A role that does not exist confers no permission.
+                            "role": "file.filerepository_owner",
+
+                            # Required. Where the role applies. One of:
+                            #   {"type": "global"}                       everywhere
+                            #   {"type": "domain", "domain": "<name>"}   objects in a domain
+                            #   {"type": "object", "name": "<name>"}     one object by name
+                            #   {"type": "object", "prn": "<prn>"}       one object by PRN
+                            "scope": {"type": "object", "name": "prod"},
+                        },
+                    ],
+                },
+            ],
+        },
+    },
+}
+```

pulpcore/app/access_policy.py

@@ -15,6 +15,13 @@ class DefaultAccessPolicy(AccessPolicy):
     An AccessPolicy that takes default statements from the view(set).
     """
 
+    def get_user_group_values(self, user):
+        """Let a stateless principal supply its groups via ``group_names`` instead of the ORM."""
+        group_names = getattr(user, "group_names", None)
+        if group_names is not None:
+            return list(group_names)
+        return super().get_user_group_values(user)
+
     @classmethod
     def get_access_policy(cls, view):
         """

pulpcore/app/checks.py

@@ -123,3 +123,33 @@ def check_artifact_checksums(app_configs, **kwargs):
         )
 
     return messages
+
+
+@register(deploy=True)
+def workload_identity_reserved_username(app_configs, **kwargs):
+    from pulpcore.app.workload_identity import config
+
+    messages = []
+    if not config.config():
+        return messages
+
+    username = config.basic_username()
+    try:
+        from django.contrib.auth import get_user_model
+
+        collides = get_user_model().objects.filter(username=username).exists()
+    except Exception:
+        return messages
+
+    if collides:
+        messages.append(
+            CheckWarning(
+                f"The WORKLOAD_IDENTITY basic_auth_username '{username}' is also a database user. "
+                "A token presented with this username over Basic auth is validated as a workload "
+                "identity token, not as that user's password. Set basic_auth_username to a name "
+                "that is not a real user to avoid ambiguity.",
+                id="pulpcore.W006",
+            )
+        )
+
+    return messages

pulpcore/app/role_util.py

@@ -173,6 +173,24 @@ def get_objects_for_user(
     accept_domain_perms=True,
     accept_global_perms=True,
 ):
+    from pulpcore.app.workload_identity.principal import WorkloadIdentityPrincipal
+
+    if isinstance(user, WorkloadIdentityPrincipal):
+        from pulpcore.app.workload_identity.authz import grants_queryset
+
+        grants = user.grants
+        if isinstance(perms, str):
+            return grants_queryset(grants, perms, qs)
+        if any_perm:
+            result = qs.none()
+            for permission_name in perms:
+                result |= grants_queryset(grants, permission_name, qs)
+            return result
+        result = qs.all()
+        for permission_name in perms:
+            result &= grants_queryset(grants, permission_name, qs)
+        return result
+
     new_qs = qs.none()
     replace = False
     if "pulpcore.backends.ObjectRolePermissionBackend" in settings.AUTHENTICATION_BACKENDS:

pulpcore/app/settings.py

@@ -316,6 +316,9 @@
 AUTHENTICATION_JSON_HEADER_JQ_FILTER = ""
 AUTHENTICATION_JSON_HEADER_OPENAPI_SECURITY_SCHEME = {}
 
+# Workload identity authentication for CI clients. Off while empty.
+WORKLOAD_IDENTITY = {}
+
 ALLOWED_IMPORT_PATHS = []
 
 ALLOWED_EXPORT_PATHS = []

pulpcore/app/workload_identity/__init__.py

@@ -0,0 +1,5 @@
+"""Workload identity authentication for CI clients.
+
+A short-lived OIDC token from a third-party provider (for example GitHub Actions) becomes a
+stateless principal whose grants are computed per request from the ``WORKLOAD_IDENTITY`` setting.
+"""

pulpcore/app/workload_identity/authentication.py

@@ -0,0 +1,100 @@
+"""DRF authentication that validates a third-party OIDC token against its provider's JWKS.
+
+The token arrives as a ``Bearer`` token, or as the password of a ``Basic`` header whose username
+is the reserved workload-identity name. On success its claims map to grants and a stateless
+``WorkloadIdentityPrincipal`` is returned.
+"""
+
+import base64
+import binascii
+import logging
+
+import jwt
+from rest_framework.authentication import BaseAuthentication
+from rest_framework.exceptions import AuthenticationFailed
+
+from pulpcore.app.workload_identity import config, rules
+from pulpcore.app.workload_identity.principal import WorkloadIdentityPrincipal
+
+_logger = logging.getLogger("pulpcore.workload_identity")
+
+
+class WorkloadIdentityAuthentication(BaseAuthentication):
+    """Authenticate requests bearing a third-party OIDC token.
+
+    On success this returns a stateless ``WorkloadIdentityPrincipal`` whose permissions are
+    derived entirely from the grants earned by the token's claims. When the
+    request carries no token, or a token that is not meant for us, the
+    authenticator returns ``None`` so that other authenticators may run.
+    """
+
+    def _get_token(self, request):
+        """Return the token from the Authorization header, or None.
+
+        Accepts a ``Bearer`` token, or a token carried as the password of a ``Basic`` header whose
+        username is the reserved workload-identity name. Any other ``Basic`` header is left for the
+        regular authenticators.
+        """
+        header = request.META.get("HTTP_AUTHORIZATION", "")
+        parts = header.split()
+        if len(parts) != 2:
+            return None
+        scheme, value = parts
+        scheme = scheme.lower()
+        if scheme == "bearer":
+            return value
+        if scheme == "basic":
+            try:
+                decoded = base64.b64decode(value).decode("utf-8")
+            except (binascii.Error, ValueError, UnicodeDecodeError):
+                return None
+            username, sep, password = decoded.partition(":")
+            if not sep or username != config.basic_username():
+                return None
+            return password
+        return None
+
+    def authenticate(self, request):
+        """Validate an OIDC token and return ``(WorkloadIdentityPrincipal, claims)``, or ``None`` if not ours."""
+        token = self._get_token(request)
+        if not token:
+            return None
+
+        try:
+            unverified = jwt.decode(token, options={"verify_signature": False})
+        except jwt.PyJWTError:
+            return None
+        issuer = unverified.get("iss")
+
+        provider = config.provider_for_issuer(issuer)
+        if provider is None:
+            return None
+
+        try:
+            signing_key = config.jwks_client(provider).get_signing_key_from_jwt(token)
+            claims = jwt.decode(
+                token,
+                signing_key.key,
+                algorithms=provider.get("algorithms", ["RS256"]),
+                issuer=provider["issuer"],
+                audience=provider["audience"],
+                options={"require": ["exp", "iss", "aud"]},
+            )
+        except jwt.PyJWTError as exc:
+            _logger.info("Rejecting OIDC token from %s: %s", issuer, exc)
+            raise AuthenticationFailed("Invalid OIDC token.")
+
+        grants = rules.grants_for(provider, claims)
+        if not grants:
+            _logger.info(
+                "No matching OIDC rule for sub=%r repository=%r",
+                claims.get("sub"),
+                claims.get("repository"),
+            )
+            raise AuthenticationFailed("No matching OIDC rule.")
+
+        return (WorkloadIdentityPrincipal(grants, username=""), claims)
+
+    def authenticate_header(self, request):
+        """Return the ``WWW-Authenticate`` value so failures are 401, not 403."""
+        return "Bearer"