Refactor auth methods

De duplicate some common codepaths. Also, for routes accepting basic
authentication, allow bearer auth as an alternative. This allows
clients to switch to bearer auth opportunistically, but we won't
have to coordinate deployments.

Basic auth should be deprecated since we don't really use a
user/password auth scheme.

src/security.py

@@ -17,18 +17,19 @@ logger.info(f"{len(BLOCKED_EMAILS)=}")
 basic_security = HTTPBasic()
 bearer_security = HTTPBearer()
 
-# --------------------- Bearer Auth
 ALLOW_ANY_EMAIL = "*"
 
+def secure_compare(token, api_key):
+    return secrets.compare_digest(token.encode("utf8"), api_key.encode("utf8"))
 
+# --------------------- Bearer Auth
 API_BEARER_TOKEN = os.environ.get("API_BEARER_TOKEN", "")  # min length is 20 chars
 async def get_bearer_auth_token_or_jwt(credentials: HTTPAuthorizationCredentials = Depends(bearer_security)):
     # tries to use the static API_KEY and defaults to google JWT auth
     access_token = credentials.credentials
-    if len(API_BEARER_TOKEN) >= 20: 
-        current_token_bytes = access_token.encode("utf8")
-        is_correct_token = secrets.compare_digest(current_token_bytes, API_BEARER_TOKEN.encode("utf8"))
-        if is_correct_token: return ALLOW_ANY_EMAIL # any email works
+    if len(API_BEARER_TOKEN) >= 20:
+        is_correct_token = secure_compare(access_token, API_BEARER_TOKEN)
+        if is_correct_token: return ALLOW_ANY_EMAIL
     return await get_bearer_auth(credentials)
 
 async def get_bearer_auth(credentials: HTTPAuthorizationCredentials = Depends(bearer_security)):
@@ -64,35 +65,38 @@ def authenticate_user(access_token):
         logger.warning(f"EXCEPTION occurred: {e}")
         return False, f"EXCEPTION occurred"
 
+# Temporary method until all clients migrate from basic to bearer
+async def bearer_or_basic_auth(bearer: HTTPAuthorizationCredentials = Depends(HTTPBearer(auto_error = False)), basic: HTTPBasicCredentials = Depends(HTTPBasic(auto_error = False))):
+
+    if bearer: return bearer.credentials
+    if basic: return basic.password
+
+    raise HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Not authenticated",
+    )
+
+# Factory method to create an authentication dependency for a specific key
+def api_key_auth(api_key):
+
+    async def auth(challenge = Depends(bearer_or_basic_auth)):
+        assert len(api_key) >= 20, "Invalid API key, must be at least 20 chars"
+
+        is_correct = secure_compare(challenge, api_key)
+        if is_correct: return True
+
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Wrong auth credentials",
+        )
+
+    return auth
 
 # --------------------- Basic Auth
 SFP = os.environ.get("STATIC_FILE_PASSWORD", "")  # min length is 20 chars
-
-
-async def get_basic_auth(credentials: HTTPBasicCredentials = Depends(basic_security)):
-    # validates that the Basic token in the case that it requires it
-    assert len(SFP) >= 20, "Invalid STATIC_FILE_PASSWORD, must be at least 20 chars"
-    current_password_bytes = credentials.password.encode("utf8")
-    is_correct_password = secrets.compare_digest(current_password_bytes, SFP.encode("utf8"))
-    if is_correct_password: return True
-    raise HTTPException(
-        status_code=status.HTTP_401_UNAUTHORIZED,
-        detail="Wrong auth credentials",
-        headers={"WWW-Authenticate": "Basic"}
-    )
+get_basic_auth = api_key_auth(SFP)
 
 # --------------------- Server-side Auth
 SERVICE_PASSWORD = os.environ.get("SERVICE_PASSWORD", "")  # min length is 20 chars
+get_server_auth = api_key_auth(SERVICE_PASSWORD)
 
-
-async def get_server_auth(credentials: HTTPBasicCredentials = Depends(basic_security)):
-    # validates that the Basic token in the case that it requires it
-    assert len(SERVICE_PASSWORD) >= 20, "Invalid SERVICE_PASSWORD, must be at least 20 chars"
-    current_password_bytes = credentials.password.encode("utf8")
-    is_correct_password = secrets.compare_digest(current_password_bytes, SERVICE_PASSWORD.encode("utf8"))
-    if is_correct_password: return True
-    raise HTTPException(
-        status_code=status.HTTP_401_UNAUTHORIZED,
-        detail="Wrong auth credentials",
-        headers={"WWW-Authenticate": "Basic"}
-    )