Fix presigned URL security vulnerabilities: enforce key/user status in SigV4 paths, remove duplicate verification, remove X-Forwarded-Host trust

app/iam.py

@@ -398,9 +398,11 @@ class IamService:
                     record = self._user_records.get(user_id)
                     if record:
                         self._check_expiry(access_key, record)
+                self._enforce_key_and_user_status(access_key)
                 return principal
 
         self._maybe_reload()
+        self._enforce_key_and_user_status(access_key)
         user_id = self._key_index.get(access_key)
         if not user_id:
             raise IamError("Unknown access key")
@@ -414,6 +416,7 @@ class IamService:
 
     def secret_for_key(self, access_key: str) -> str:
         self._maybe_reload()
+        self._enforce_key_and_user_status(access_key)
         secret = self._key_secrets.get(access_key)
         if not secret:
             raise IamError("Unknown access key")
@@ -1028,6 +1031,16 @@ class IamService:
         user, _ = self._resolve_raw_user(access_key)
         return user
 
+    def _enforce_key_and_user_status(self, access_key: str) -> None:
+        key_status = self._key_status.get(access_key, "active")
+        if key_status != "active":
+            raise IamError("Access key is inactive")
+        user_id = self._key_index.get(access_key)
+        if user_id:
+            record = self._user_records.get(user_id)
+            if record and not record.get("enabled", True):
+                raise IamError("User account is disabled")
+
     def get_secret_key(self, access_key: str) -> str | None:
         now = time.time()
         cached = self._secret_key_cache.get(access_key)
@@ -1039,6 +1052,7 @@ class IamService:
                     record = self._user_records.get(user_id)
                     if record:
                         self._check_expiry(access_key, record)
+                self._enforce_key_and_user_status(access_key)
                 return secret_key
 
         self._maybe_reload()
@@ -1049,6 +1063,7 @@ class IamService:
                 record = self._user_records.get(user_id)
                 if record:
                     self._check_expiry(access_key, record)
+            self._enforce_key_and_user_status(access_key)
             self._secret_key_cache[access_key] = (secret, now)
             return secret
         return None
@@ -1064,9 +1079,11 @@ class IamService:
                     record = self._user_records.get(user_id)
                     if record:
                         self._check_expiry(access_key, record)
+                self._enforce_key_and_user_status(access_key)
                 return principal
 
         self._maybe_reload()
+        self._enforce_key_and_user_status(access_key)
         user_id = self._key_index.get(access_key)
         if user_id:
             record = self._user_records.get(user_id)

app/s3_api.py

@@ -534,21 +534,6 @@ def _authorize_action(principal: Principal | None, bucket_name: str | None, acti
     raise iam_error or IamError("Access denied")
 
 
-def _enforce_bucket_policy(principal: Principal | None, bucket_name: str | None, object_key: str | None, action: str) -> None:
-    if not bucket_name:
-        return
-    policy_context = _build_policy_context()
-    decision = _bucket_policies().evaluate(
-        principal.access_key if principal else None,
-        bucket_name,
-        object_key,
-        action,
-        policy_context,
-    )
-    if decision == "deny":
-        raise IamError("Access denied by bucket policy")
-
-
 def _object_principal(action: str, bucket_name: str, object_key: str):
     principal, error = _require_principal()
     try:
@@ -557,121 +542,7 @@ def _object_principal(action: str, bucket_name: str, object_key: str):
     except IamError as exc:
         if not error:
             return None, _error_response("AccessDenied", str(exc), 403)
-    if not _has_presign_params():
         return None, error
-    try:
-        principal = _validate_presigned_request(action, bucket_name, object_key)
-        _enforce_bucket_policy(principal, bucket_name, object_key, action)
-        return principal, None
-    except IamError as exc:
-        return None, _error_response("AccessDenied", str(exc), 403)
-
-
-def _has_presign_params() -> bool:
-    return bool(request.args.get("X-Amz-Algorithm"))
-
-
-def _validate_presigned_request(action: str, bucket_name: str, object_key: str) -> Principal:
-    algorithm = request.args.get("X-Amz-Algorithm")
-    credential = request.args.get("X-Amz-Credential")
-    amz_date = request.args.get("X-Amz-Date")
-    signed_headers = request.args.get("X-Amz-SignedHeaders")
-    expires = request.args.get("X-Amz-Expires")
-    signature = request.args.get("X-Amz-Signature")
-    if not all([algorithm, credential, amz_date, signed_headers, expires, signature]):
-        raise IamError("Malformed presigned URL")
-    if algorithm != "AWS4-HMAC-SHA256":
-        raise IamError("Unsupported signing algorithm")
-
-    parts = credential.split("/")
-    if len(parts) != 5:
-        raise IamError("Invalid credential scope")
-    access_key, date_stamp, region, service, terminal = parts
-    if terminal != "aws4_request":
-        raise IamError("Invalid credential scope")
-    config_region = current_app.config["AWS_REGION"]
-    config_service = current_app.config["AWS_SERVICE"]
-    if region != config_region or service != config_service:
-        raise IamError("Credential scope mismatch")
-
-    try:
-        expiry = int(expires)
-    except ValueError as exc:
-        raise IamError("Invalid expiration") from exc
-    min_expiry = current_app.config.get("PRESIGNED_URL_MIN_EXPIRY_SECONDS", 1)
-    max_expiry = current_app.config.get("PRESIGNED_URL_MAX_EXPIRY_SECONDS", 604800)
-    if expiry < min_expiry or expiry > max_expiry:
-        raise IamError(f"Expiration must be between {min_expiry} second(s) and {max_expiry} seconds")
-
-    try:
-        request_time = datetime.strptime(amz_date, "%Y%m%dT%H%M%SZ").replace(tzinfo=timezone.utc)
-    except ValueError as exc:
-        raise IamError("Invalid X-Amz-Date") from exc
-    now = datetime.now(timezone.utc)
-    tolerance = timedelta(seconds=current_app.config.get("SIGV4_TIMESTAMP_TOLERANCE_SECONDS", 900))
-    if request_time > now + tolerance:
-        raise IamError("Request date is too far in the future")
-    if now > request_time + timedelta(seconds=expiry):
-        raise IamError("Presigned URL expired")
-
-    signed_headers_list = [header.strip().lower() for header in signed_headers.split(";") if header]
-    signed_headers_list.sort()
-    canonical_headers = _canonical_headers_from_request(signed_headers_list)
-    canonical_query = _canonical_query_from_request()
-    payload_hash = request.args.get("X-Amz-Content-Sha256", "UNSIGNED-PAYLOAD")
-    canonical_request = "\n".join(
-        [
-            request.method,
-            _canonical_uri(bucket_name, object_key),
-            canonical_query,
-            canonical_headers,
-            ";".join(signed_headers_list),
-            payload_hash,
-        ]
-    )
-    hashed_request = hashlib.sha256(canonical_request.encode()).hexdigest()
-    scope = f"{date_stamp}/{region}/{service}/aws4_request"
-    string_to_sign = "\n".join([
-        "AWS4-HMAC-SHA256",
-        amz_date,
-        scope,
-        hashed_request,
-    ])
-    secret = _iam().secret_for_key(access_key)
-    signing_key = _derive_signing_key(secret, date_stamp, region, service)
-    expected = hmac.new(signing_key, string_to_sign.encode(), hashlib.sha256).hexdigest()
-    if not hmac.compare_digest(expected, signature):
-        raise IamError("Signature mismatch")
-    return _iam().principal_for_key(access_key)
-
-
-def _canonical_query_from_request() -> str:
-    parts = []
-    for key in sorted(request.args.keys()):
-        if key == "X-Amz-Signature":
-            continue
-        values = request.args.getlist(key)
-        encoded_key = quote(str(key), safe="-_.~")
-        for value in sorted(values):
-            encoded_value = quote(str(value), safe="-_.~")
-            parts.append(f"{encoded_key}={encoded_value}")
-    return "&".join(parts)
-
-
-def _canonical_headers_from_request(headers: list[str]) -> str:
-    lines = []
-    for header in headers:
-        if header == "host":
-            api_base = current_app.config.get("API_BASE_URL")
-            if api_base:
-                value = urlparse(api_base).netloc
-            else:
-                value = request.host
-        else:
-            value = request.headers.get(header, "")
-        canonical_value = " ".join(value.strip().split()) if value else ""
-        lines.append(f"{header}:{canonical_value}")
-    return "\n".join(lines) + "\n"
 
 
 def _canonical_uri(bucket_name: str, object_key: str | None) -> str:
@@ -737,8 +608,8 @@ def _generate_presigned_url(
         host = parsed.netloc
         scheme = parsed.scheme
     else:
-        host = request.headers.get("X-Forwarded-Host", request.host)
+        host = request.host
-        scheme = request.headers.get("X-Forwarded-Proto", request.scheme or "http")
+        scheme = request.scheme or "http"
 
     canonical_headers = f"host:{host}\n"
     canonical_request = "\n".join(

tests/test_api.py

@@ -1,3 +1,56 @@
+import hashlib
+import hmac
+from datetime import datetime, timezone
+from urllib.parse import quote
+
+
+def _build_presigned_query(path: str, *, access_key: str = "test", secret_key: str = "secret", expires: int = 60) -> str:
+    now = datetime.now(timezone.utc)
+    amz_date = now.strftime("%Y%m%dT%H%M%SZ")
+    date_stamp = now.strftime("%Y%m%d")
+    region = "us-east-1"
+    service = "s3"
+    credential_scope = f"{date_stamp}/{region}/{service}/aws4_request"
+
+    query_items = [
+        ("X-Amz-Algorithm", "AWS4-HMAC-SHA256"),
+        ("X-Amz-Content-Sha256", "UNSIGNED-PAYLOAD"),
+        ("X-Amz-Credential", f"{access_key}/{credential_scope}"),
+        ("X-Amz-Date", amz_date),
+        ("X-Amz-Expires", str(expires)),
+        ("X-Amz-SignedHeaders", "host"),
+    ]
+    canonical_query = "&".join(
+        f"{quote(k, safe='-_.~')}={quote(v, safe='-_.~')}" for k, v in sorted(query_items)
+    )
+
+    canonical_request = "\n".join([
+        "GET",
+        quote(path, safe="/-_.~"),
+        canonical_query,
+        "host:localhost\n",
+        "host",
+        "UNSIGNED-PAYLOAD",
+    ])
+    hashed_request = hashlib.sha256(canonical_request.encode("utf-8")).hexdigest()
+    string_to_sign = "\n".join([
+        "AWS4-HMAC-SHA256",
+        amz_date,
+        credential_scope,
+        hashed_request,
+    ])
+
+    def _sign(key: bytes, msg: str) -> bytes:
+        return hmac.new(key, msg.encode("utf-8"), hashlib.sha256).digest()
+
+    k_date = _sign(("AWS4" + secret_key).encode("utf-8"), date_stamp)
+    k_region = _sign(k_date, region)
+    k_service = _sign(k_region, service)
+    signing_key = _sign(k_service, "aws4_request")
+    signature = hmac.new(signing_key, string_to_sign.encode("utf-8"), hashlib.sha256).hexdigest()
+    return canonical_query + f"&X-Amz-Signature={signature}"
+
+
 def test_bucket_and_object_lifecycle(client, signer):
     headers = signer("PUT", "/photos")
     response = client.put("/photos", headers=headers)
@@ -114,6 +167,45 @@ def test_missing_credentials_denied(client):
     assert response.status_code == 403
 
 
+def test_presigned_url_denied_for_disabled_user(client, signer):
+    headers = signer("PUT", "/secure")
+    assert client.put("/secure", headers=headers).status_code == 200
+
+    payload = b"hello"
+    headers = signer("PUT", "/secure/file.txt", body=payload)
+    assert client.put("/secure/file.txt", headers=headers, data=payload).status_code == 200
+
+    iam = client.application.extensions["iam"]
+    iam.disable_user("test")
+
+    query = _build_presigned_query("/secure/file.txt")
+    response = client.get(f"/secure/file.txt?{query}", headers={"Host": "localhost"})
+    assert response.status_code == 403
+    assert b"User account is disabled" in response.data
+
+
+def test_presigned_url_denied_for_inactive_key(client, signer):
+    headers = signer("PUT", "/secure2")
+    assert client.put("/secure2", headers=headers).status_code == 200
+
+    payload = b"hello"
+    headers = signer("PUT", "/secure2/file.txt", body=payload)
+    assert client.put("/secure2/file.txt", headers=headers, data=payload).status_code == 200
+
+    iam = client.application.extensions["iam"]
+    for user in iam._raw_config.get("users", []):
+        for key_info in user.get("access_keys", []):
+            if key_info.get("access_key") == "test":
+                key_info["status"] = "inactive"
+    iam._save()
+    iam._load()
+
+    query = _build_presigned_query("/secure2/file.txt")
+    response = client.get(f"/secure2/file.txt?{query}", headers={"Host": "localhost"})
+    assert response.status_code == 403
+    assert b"Access key is inactive" in response.data
+
+
 def test_bucket_policies_deny_reads(client, signer):
     import json