Add new backend for LinkedIn OpenID Connect (#833)

* create linkedin openid connect backend

* add docstring with link to official docs and deprecation notice for oauth2

* define oidc endpoint for linkedin

* override token auth method to provide client id and secret in payload (not basic auth)

* copy and override validate_claims to remove not support nonce validation

* remove already disabled code section for nonce check

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add test case for linkedin openid (still breaking, inspired from google)

* skip invalid nonce test as linkedin does not provide any nonce

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

social_core/backends/linkedin.py

@@ -2,11 +2,47 @@
 LinkedIn OAuth1 and OAuth2 backend, docs at:
     https://python-social-auth.readthedocs.io/en/latest/backends/linkedin.html
 """
-from social_core.exceptions import AuthCanceled
+import datetime
+from calendar import timegm
+
+from social_core.backends.open_id_connect import OpenIdConnectAuth
+from social_core.exceptions import AuthCanceled, AuthTokenError
 
 from .oauth import BaseOAuth2
 
 
+class LinkedinOpenIdConnect(OpenIdConnectAuth):
+    """
+    Linkedin OpenID Connect backend. Oauth2 has been deprecated as of August 1, 2023.
+    https://learn.microsoft.com/en-us/linkedin/consumer/integrations/self-serve/sign-in-with-linkedin-v2?context=linkedin/consumer/context
+    """
+
+    name = "linkedin-openidconnect"
+    # Settings from https://www.linkedin.com/oauth/.well-known/openid-configuration
+    OIDC_ENDPOINT = "https://www.linkedin.com/oauth"
+
+    # https://developer.okta.com/docs/reference/api/oidc/#response-example-success-9
+    # Override this value as it is not provided by Linkedin.
+    # else our request falls back to basic auth which is not supported.
+    TOKEN_ENDPOINT_AUTH_METHOD = "client_secret_post"
+
+    def validate_claims(self, id_token):
+        """Copy of the regular validate_claims method without the nonce validation."""
+
+        utc_timestamp = timegm(datetime.datetime.utcnow().utctimetuple())
+
+        if "nbf" in id_token and utc_timestamp < id_token["nbf"]:
+            raise AuthTokenError(self, "Incorrect id_token: nbf")
+
+        # Verify the token was issued in the last 10 minutes
+        iat_leeway = self.setting("ID_TOKEN_MAX_AGE", self.ID_TOKEN_MAX_AGE)
+        if utc_timestamp > id_token["iat"] + iat_leeway:
+            raise AuthTokenError(self, "Incorrect id_token: iat")
+
+        # Skip the nonce validation for linkedin as it does not provide any nonce.
+        # https://stackoverflow.com/questions/76889585/issues-with-sign-in-with-linkedin-using-openid-connect
+
+
 class LinkedinOAuth2(BaseOAuth2):
     name = "linkedin-oauth2"
     AUTHORIZATION_URL = "https://www.linkedin.com/oauth/v2/authorization"

social_core/tests/backends/test_linkedin.py

@@ -1,6 +1,44 @@
 import json
 
 from .oauth import OAuth2Test
+from .test_open_id_connect import OpenIdConnectTestMixin
+
+
+class LinkedinOpenIdConnectTest(OpenIdConnectTestMixin, OAuth2Test):
+    backend_path = "social_core.backends.linkedin.LinkedinOpenIdConnect"
+    user_data_url = "https://api.linkedin.com/v2/userinfo"
+    issuer = "https://www.linkedin.com"
+    openid_config_body = json.dumps(
+        {
+            "issuer": "https://www.linkedin.com",
+            "authorization_endpoint": "https://www.linkedin.com/oauth/v2/authorization",
+            "token_endpoint": "https://www.linkedin.com/oauth/v2/accessToken",
+            "userinfo_endpoint": "https://api.linkedin.com/v2/userinfo",
+            "jwks_uri": "https://www.linkedin.com/oauth/openid/jwks",
+            "response_types_supported": ["code"],
+            "subject_types_supported": ["pairwise"],
+            "id_token_signing_alg_values_supported": ["RS256"],
+            "scopes_supported": ["openid", "profile", "email"],
+            "claims_supported": [
+                "iss",
+                "aud",
+                "iat",
+                "exp",
+                "sub",
+                "name",
+                "given_name",
+                "family_name",
+                "picture",
+                "email",
+                "email_verified",
+                "locale",
+            ],
+        }
+    )
+
+    def test_invalid_nonce(self):
+        """Skip the invalid nonce test as LinkedIn does not provide any nonce."""
+        pass
 
 
 class BaseLinkedinTest: