🛡️ Sentinel: [CRITICAL] Fix JWT 검증 정보 노출 및 crit 헤더 검증 누락

.jules/sentinel.md

@@ -2,3 +2,8 @@
 **Vulnerability:** User-provided string fields (like project and connection names) lacked strict validation against control characters, only relying on length constraints.
 **Learning:** This could potentially lead to Log Injection (CRLF injection), Null Byte Injection, or terminal escape injection if these strings are subsequently logged or rendered directly.
 **Prevention:** Use explicit regex validation `pattern=r'^[^\x00-\x1F\x7F]+$'` on Pydantic string fields to strictly reject control characters.
+
+## 2025-02-27 - JWT 검증 시 Critical (crit) 헤더 필수 검증 및 에러 메시지 정보 노출 방지
+**Vulnerability:** JWT 파싱 중 `crit` 헤더를 검증하지 않아 RFC 7515 요구사항과 STRIX 보안 점검을 우회할 수 있었고, JWT 검증 실패 시 자세한 에러 메시지가 반환되어 정보가 유출될 위험이 존재했습니다.
+**Learning:** `crit` 헤더는 안전하게 길이와 내용이 제한된 문자열 리스트로 검증되어야 하며, 인가 실패 시 공격자에게 너무 자세한 검증 실패 사유(예: "token missing exp" 등)를 노출해서는 안 됩니다.
+**Prevention:** `_validate_jwt_header`에서 `crit` 배열의 존재와 형태를 엄격하게 검증하고, 모든 JWT 예외 처리에서 자세한 사유 대신 HTTP 401 `"invalid token"`을 반환하여 내부 검증 로직 노출을 차단합니다.

backend/app/auth.py

@@ -166,7 +166,7 @@ def _jwt_expiry(claims: dict[str, Any]) -> dt.datetime:
 
     exp = claims.get("exp")
     if not isinstance(exp, int | float):
-        raise HTTPException(status_code=401, detail="token missing exp")
+        raise HTTPException(status_code=401, detail="invalid token")
     return dt.datetime.fromtimestamp(float(exp), tz=dt.timezone.utc)
 
 
@@ -179,15 +179,26 @@ def _validate_jwt_header(header: dict[str, Any]) -> str:
             not isinstance(token_type, str)
             or token_type.strip().lower() not in OIDC_ALLOWED_TOKEN_TYPES
         ):
-            raise HTTPException(status_code=401, detail="unsupported token type")
+            raise HTTPException(status_code=401, detail="invalid token")
 
     content_type = header.get("cty")
     if content_type is not None:
-        raise HTTPException(status_code=401, detail="unsupported token content type")
+        raise HTTPException(status_code=401, detail="invalid token")
+
+    crit = header.get("crit")
+    if crit is not None:
+        if not isinstance(crit, list) or len(crit) == 0 or len(crit) > 10:
+            raise HTTPException(status_code=401, detail="invalid token")
+        for item in crit:
+            if not isinstance(item, str):
+                raise HTTPException(status_code=401, detail="invalid token")
+            # For this app, we don't recognize ANY critical extensions.
+            # If `crit` is present and specifies any extensions, we MUST reject the token.
+            raise HTTPException(status_code=401, detail="invalid token")
 
     header_alg_raw = header.get("alg")
     if not isinstance(header_alg_raw, str) or not header_alg_raw:
-        raise HTTPException(status_code=401, detail="token missing alg")
+        raise HTTPException(status_code=401, detail="invalid token")
     return header_alg_raw.upper()
 
 
@@ -240,13 +251,13 @@ async def _decode_verified_oidc_token(token: str) -> dict[str, Any]:
     try:
         header = cast(dict[str, Any], jwt.get_unverified_header(token))
     except Exception:  # noqa: BLE001
-        raise HTTPException(status_code=401, detail="invalid token header")
+        raise HTTPException(status_code=401, detail="invalid token")
 
     header_alg = _validate_jwt_header(header)
     if header_alg not in OIDC_ALLOWED_ALGORITHMS:
         raise HTTPException(
             status_code=401,
-            detail="unsupported token algorithm",
+            detail="invalid token",
         )
 
     jwks = await _get_jwks()
@@ -255,20 +266,20 @@ async def _decode_verified_oidc_token(token: str) -> dict[str, Any]:
         jwks = await _get_jwks(force_refresh=True)
         jwk = _pick_jwk(jwks, header.get("kid"))
     if jwk is None:
-        raise HTTPException(status_code=401, detail="unknown signing key")
+        raise HTTPException(status_code=401, detail="invalid token")
 
     kty = jwk.get("kty")
     if not isinstance(kty, str):
-        raise HTTPException(status_code=401, detail="algorithm/key type mismatch")
+        raise HTTPException(status_code=401, detail="invalid token")
     jwk_kty = kty.upper()
     if jwk_kty == "RSA":
         if not (header_alg.startswith("RS") or header_alg.startswith("PS")):
-            raise HTTPException(status_code=401, detail="algorithm/key type mismatch")
+            raise HTTPException(status_code=401, detail="invalid token")
     elif jwk_kty == "EC":
         if not header_alg.startswith("ES"):
-            raise HTTPException(status_code=401, detail="algorithm/key type mismatch")
+            raise HTTPException(status_code=401, detail="invalid token")
     else:
-        raise HTTPException(status_code=401, detail="algorithm/key type mismatch")
+        raise HTTPException(status_code=401, detail="invalid token")
 
     try:
         claims = jwt.decode(
@@ -288,7 +299,7 @@ async def _decode_verified_oidc_token(token: str) -> dict[str, Any]:
         )
     except Exception as err:
         raise HTTPException(
-            status_code=401, detail="token verification failed"
+            status_code=401, detail="invalid token"
         ) from err
 
     return cast(dict[str, Any], claims)
@@ -303,13 +314,13 @@ async def _verified_token_from_claims(
     jwt_id = claims.get("jti")
     name = claims.get("name") or claims.get("preferred_username")
     if not isinstance(sub, str):
-        raise HTTPException(status_code=401, detail="token missing sub")
+        raise HTTPException(status_code=401, detail="invalid token")
     if not isinstance(jwt_id, str) or not jwt_id.strip():
-        raise HTTPException(status_code=401, detail="token missing jti")
+        raise HTTPException(status_code=401, detail="invalid token")
 
     expires_at = _jwt_expiry(claims)
     if verify_revocation and await is_token_jti_revoked(jwt_id):
-        raise HTTPException(status_code=401, detail="token revoked")
+        raise HTTPException(status_code=401, detail="invalid token")
 
     return VerifiedToken(
         subject=sub,

backend/tests/test_auth_crit.py

@@ -0,0 +1,33 @@
+import pytest
+from fastapi import HTTPException
+from app.auth import _validate_jwt_header
+
+def test_crit_validates_as_list():
+    with pytest.raises(HTTPException) as exc_info:
+        _validate_jwt_header({"alg": "RS256", "crit": "not-a-list"})
+    assert exc_info.value.status_code == 401
+    assert exc_info.value.detail == "invalid token"
+
+def test_crit_rejects_empty_list():
+    with pytest.raises(HTTPException) as exc_info:
+        _validate_jwt_header({"alg": "RS256", "crit": []})
+    assert exc_info.value.status_code == 401
+    assert exc_info.value.detail == "invalid token"
+
+def test_crit_rejects_long_list():
+    with pytest.raises(HTTPException) as exc_info:
+        _validate_jwt_header({"alg": "RS256", "crit": ["item"] * 11})
+    assert exc_info.value.status_code == 401
+    assert exc_info.value.detail == "invalid token"
+
+def test_crit_rejects_non_string_items():
+    with pytest.raises(HTTPException) as exc_info:
+        _validate_jwt_header({"alg": "RS256", "crit": [123]})
+    assert exc_info.value.status_code == 401
+    assert exc_info.value.detail == "invalid token"
+
+def test_crit_rejects_unrecognized_items():
+    with pytest.raises(HTTPException) as exc_info:
+        _validate_jwt_header({"alg": "RS256", "crit": ["b64"]})
+    assert exc_info.value.status_code == 401
+    assert exc_info.value.detail == "invalid token"

backend/tests/test_auth_security.py

@@ -207,7 +207,7 @@ def fail_decode(*_: object, **__: object) -> dict:
         )
 
     assert exc_info.value.status_code == 401
-    assert exc_info.value.detail == "unsupported token algorithm"
+    assert exc_info.value.detail == "invalid token"
 
 
 @pytest.mark.asyncio
@@ -244,7 +244,7 @@ def fail_decode(*_: object, **__: object) -> dict:
         await auth._decode_verified_oidc_token("ey...fake...")
 
     assert exc_info.value.status_code == 401
-    assert exc_info.value.detail == "algorithm/key type mismatch"
+    assert exc_info.value.detail == "invalid token"
 
 
 @pytest.mark.asyncio
@@ -307,11 +307,11 @@ async def mock_is_token_revoked(jti):
     [
         (
             {"kid": "key-1", "alg": "RS256", "typ": "nested+jwt"},
-            "unsupported token type",
+            "invalid token",
         ),
         (
             {"kid": "key-1", "alg": "RS256", "cty": "JWT"},
-            "unsupported token content type",
+            "invalid token",
         ),
     ],
 )
@@ -417,7 +417,7 @@ async def mock_is_token_revoked2(jti):
         )
 
     assert exc_info.value.status_code == 401
-    assert exc_info.value.detail == "token missing jti"
+    assert exc_info.value.detail == "invalid token"
 
 
 @pytest.mark.asyncio
@@ -464,7 +464,7 @@ async def mock_revoke(jti, ext):
         )
 
     assert exc_info.value.status_code == 401
-    assert exc_info.value.detail == "token revoked"
+    assert exc_info.value.detail == "invalid token"
 
 
 @pytest.mark.asyncio
@@ -560,7 +560,7 @@ def mock_get_unverified_header(token):
         await auth._decode_verified_oidc_token("invalid_token")
 
     assert excinfo.value.status_code == 401
-    assert excinfo.value.detail == "invalid token header"
+    assert excinfo.value.detail == "invalid token"
 
 
 @pytest.mark.asyncio
@@ -592,7 +592,7 @@ async def mock_is_token_revoked2(jti):
         await auth._decode_verified_oidc_token("Bearer token")
 
     assert exc_info.value.status_code == 401
-    assert exc_info.value.detail == "token verification failed"
+    assert exc_info.value.detail == "invalid token"
 
 @pytest.mark.asyncio
 async def test_oidc_rejects_algorithm_key_type_mismatch(
@@ -625,7 +625,7 @@ def fail_decode(*_: object, **__: object) -> dict:
         await auth._decode_verified_oidc_token("ey...")
 
     assert exc_info.value.status_code == 401
-    assert exc_info.value.detail == "algorithm/key type mismatch"
+    assert exc_info.value.detail == "invalid token"
 @pytest.mark.asyncio
 async def test_oidc_jwks_refresh_rate_limiting(
     monkeypatch: pytest.MonkeyPatch,