Insecure Direct Object Reference in Chi with Jwt Tokens

Insecure Direct Object Reference (IDOR) occurs when an API exposes internal object references, such as database keys or identifiers, without proper authorization checks. In Chi, a common pattern is to extract a resource identifier from the request path or query parameters and use it directly to fetch or modify a record. When Jwt Tokens are used for authentication but authorization is missing or incomplete, the presence of a valid token does not prove the caller is allowed to access the specific object. An attacker can take a valid Jwt issued for one user, change the identifier in the request (for example, incrementing an account ID), and access or act on another user’s data. This becomes especially risky when endpoints rely only on the token’s presence and do not enforce tenant or ownership checks tied to the subject or scopes encoded in the Jwt.

Consider a Chi route that retrieves a user profile by ID from the URL while validating the Jwt but not ensuring the profile belongs to the caller. The route might decode the token to obtain claims like subject and roles, then use the path parameter as a direct lookup key. Because the route trusts the identifier without verifying that the subject in the Jwt matches the requested identifier, the endpoint is vulnerable to IDOR. Attackers can automate enumeration by iterating over plausible IDs, and because the API returns 200 with data or 404 with minimal timing differences, they can infer existence and extract information. The use of Jwt in this context does not mitigate IDOR; it only establishes identity, not authorization for the specific resource.

Chi’s composability can unintentionally amplify IDOR when handlers share data models across multiple routes or when route parameters are reused across versions. If the Jwt is accepted but the authorization logic is scattered or implicit, developers might assume middleware has already enforced ownership. In reality, without explicit checks that bind the resource to the subject or group claims in the Jwt, each route must independently enforce authorization. Attack surfaces expand when endpoints accept identifiers via path, query, or body and skip verifying that the authenticated subject has the right to operate on that identifier. Runtime findings from scans often highlight endpoints where object-level authorization is absent despite Jwt validation, underscoring the need to align token claims with data access controls.

To remediate IDOR with Jwt in Chi, enforce explicit authorization that ties the resource to the token claims. Instead of trusting route parameters alone, map the identifier to the authenticated subject and verify equality or membership. Below is a concrete Chi handler in Common Lisp that demonstrates secure access control using Jwt claims.

(ql:quickload '(:chi :jonathan :jwt))

(defun get-current-subject (request)
  "Extract and return the subject claim from a validated Jwt."
  (let ((auth-header (hunchentoot:header "Authorization" request)))
    (when (and auth-header (cl-ppcre:scan "^Bearer " auth-header))
      (let ((token (subseq auth-header 7)))
        (jwt:decode token *public-key* :algorithm :rs256)))))

(defun user-handler (request user-id)
  (let* ((claims (get-current-subject request))
         (subject (gethash "sub" claims)))
    (if (or (null subject)
            (not (string= subject user-id)))
        (chi:response :status 403 :content "Forbidden")
        (let ((profile (fetch-profile-by-id user-id)))
          (chi:response :status 200 :content profile)))))

(chi:define-routes
  (GET "/profiles/:user-id" (user-id) (user-handler request user-id)))

This pattern ensures that the subject claim from the Jwt is compared directly with the user-id parameter. If they do not match, the request is rejected with 403 regardless of a valid token. It avoids IDOR by never using the parameter as an unchecked key for another user’s data.

For endpoints that operate on collections or where subjects belong to groups, include group or role checks derived from the Jwt claims. The following example shows how to verify scope or group membership before allowing access to shared resources.

(defun can-access-resource-p (claims resource-owner-id)
  (or (string= (gethash "sub" claims) resource-owner-id)
      (member "admin" (gethash "groups" claims) :test #'string=)
      (member "scope:read:profiles" (gethash "scope" claims) :test #'string=)))

(defun shared-item-handler (request item-id)
  (let* ((claims (get-current-subject request))
         (item (fetch-item-by-id item-id)))
    (if (and item (can-access-resource-p claims (gethash "owner_id" item)))
        (chi:response :status 200 :content item)
        (chi:response :status 403 :content "Access denied"))))

These examples illustrate how to align Jwt claims with data ownership to prevent IDOR. Remember that Jwt validation and signature verification are not authorization; you must explicitly compare claims to resource identifiers and enforce least privilege. The dashboard can help track endpoints where IDOR findings persist, and the CLI allows you to integrate checks into scripts. For teams managing many services, the Pro plan supports continuous monitoring of APIs, helping detect regressions where authorization logic might be bypassed. In CI/CD, the GitHub Action can fail builds if scans detect missing object-level checks, while the MCP Server enables you to query and test endpoints directly from your AI coding assistant during development.