Handle additional JWT and JOSE error cases in token validation.

Expanded exception handling to cover more specific JWT and JOSE-related errors, including signature verification failures and malformed tokens. This ensures better error messaging and robustness in token validation.

backend/app/auth/security.py

@@ -7,6 +7,7 @@ from jose import jwt, ExpiredSignatureError, JWTError
 from passlib.context import CryptContext
 from app.core.config import settings
 from app.schemas.token import TokenPayload, TokenResponse
+from jose.exceptions import ExpiredSignatureError, JWTError, JOSEError
 
 # Configuration
 SECRET_KEY = settings.SECRET_KEY
@@ -116,12 +117,19 @@ def decode_token(token: str, required_type: str = "access") -> TokenPayload:
             jti=payload.get("jti")
         )
 
-    except KeyError as e:
-        raise JWTError("Malformed token. Missing required claim.") from e
-    except ExpiredSignatureError as e:
+    except ExpiredSignatureError as e:  # Expired token
         raise JWTError("Token expired. Please refresh your token to continue.") from e
     except JWTError as e:
+        # Handle signature verification and malformed token errors
+        if str(e) in ["Signature verification failed.", "Not enough segments"]:
+            raise JWTError("Invalid token.") from e
+        # Propagate other JWTError messages
         raise JWTError(str(e)) from e
+    except KeyError as e:  # Missing required claims
+        raise JWTError("Malformed token. Missing required claim.") from e
+    except JOSEError as e:  # All other JOSE-related errors
+        raise JWTError("Invalid token.") from e
+