Privilege Escalation in Chi with Jwt Tokens

Privilege escalation in Chi via JWT tokens typically occurs when an application embeds authorization or role information in the token but does not enforce authorization checks on each request. Chi is a lightweight HTTP router for Go, often used to build APIs where JWTs carry claims such as role or scope. If routes rely solely on the presence of a valid JWT without verifying that the token’s claims permit the specific action, an authenticated user can access admin endpoints or perform privileged operations by manipulating route parameters or guessing unguarded paths.

Attackers exploit this by intercepting or guessing IDs in URLs (Broken Level Authorization/IDOR) and leveraging a valid low-privilege JWT to access or modify other users’ data, or by tampering with the token’s claims if the token is unsigned or uses a weak secret. For example, changing a role: user claim to role: admin in a manually constructed token and reusing it to call admin-only routes in Chi. Because Chi does not inherently validate claims beyond authentication, the request proceeds as if the user legitimately possessed elevated privileges.

Insecure token handling compounds the risk. If tokens lack an iss (issuer) or aud (audience) validation, or if the application does not check token expiry and revocation, an attacker can reuse an old token or inject a token intended for another service. Additionally, if the application uses path-based routing in Chi without correlating the subject or tenant identifier in the JWT with the resource being accessed, horizontal privilege escalation occurs: one user can act on another user’s resources simply by iterating over known IDs.

Real-world parallels include findings where scanners detect endpoints like GET /admin/users/{id} protected only by JWT verification in Chi, yet lacking role checks. Combined with weak token configuration (e.g., algorithm confusion or missing signing), this can lead to unauthorized data access or control-plane operations. Such gaps align with OWASP API Top 10 A01:2023 broken authentication and A05:2023 insufficient logging and monitoring, and can be surfaced as high-severity findings in a middleBrick scan, which correlates results to frameworks like PCI-DSS and SOC2.

middleBrick identifies these patterns by correlating OpenAPI declarations of protected routes in Chi with runtime behavior, flagging endpoints where JWT presence does not enforce per-method or per-claim authorization. The scanner also probes for missing issuer/audience validation and excessive agency patterns (e.g., token introspection misuse), providing prioritized findings with remediation guidance rather than attempting to fix the service itself.

Remediation focuses on strict validation of JWT claims and integrating authorization checks directly into Chi middleware. Always verify the token signature using a trusted key or JWKS, validate standard claims such as iss, aud, exp, and nbf, and enforce role or scope checks per route and method.

Example: Verified JWT parsing and role enforcement in Chi

//go
package main

import (
	"context"
	"fmt"
	"net/http"

	"github.com/go-chi/chi/v5"
	"github.com/golang-jwt/jwt/v5"
)

type Claims struct {
	Role string `json:"role"`
	jwt.RegisteredClaims
}

func jwtAuth(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		tokenString := r.Header.Get("Authorization")
		if tokenString == "" {
			http.Error(w, `"authorization header required"`, http.StatusUnauthorized)
			return
		}
		// Replace with your key retrieval logic (e.g., JWKS)
		keyFunc := func(token *jwt.Token) (interface{}, error) {
			// Validate signing method
			if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
				return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
			}
			return []byte("your-256-bit-secret"), nil
		}

		claims := &Claims{}
		token, err := jwt.ParseWithClaims(tokenString, claims, keyFunc)
		if err !=nbsp;nil || !token.Valid {
			http.Error(w, `"invalid token"`, http.StatusUnauthorized)
			return
		}

		// Attach claims to context for downstream use
		ctx := context.WithValue(r.Context(), "claims", claims)
		r = r.WithContext(ctx)
		next.ServeHTTP(w, r)
	})
}

func adminHandler(w http.ResponseWriter, r *http.Request) {
	claims, _ := r.Context().Value("claims").(*Claims)
	if claims.Role != "admin" {
		http.Error(w, `"insufficient permissions"`, http.StatusForbidden)
		return
	}
	fmt.Fprintf(w, "admin access granted")
}

func main() {
	r := chi.NewRouter()
	r.Use(jwtAuth)

	// Admin route with role check enforced
	r.Get("/admin/users/{id}", adminHandler)

	// Example public or user-scoped route
	r.Get("/profile/{id}", func(w http.ResponseWriter, r *http.Request) {
		// Ensure the user can only access their own ID when not admin
		claims := r.Context().Value("claims").(*Claims)
		userID := chi.URLParam(r, "id")
		if claims.Role != "admin" && claims.Subject != userID {
			http.Error(w, `"forbidden"`, http.StatusForbidden)
			return
		}
		fmt.Fprintf(w, "profile for %s", userID)
	})

	http.ListenAndServe(":8080", r)
}

The example validates the JWT signature, standard claims, and explicitly checks the role claim before allowing access to admin routes. For user-specific resources, it also ensures the subject (sub) matches the requested ID to prevent horizontal escalation.

Complementary checks with middleBrick

Use the CLI to validate your configuration: middlebrick scan <url>. The scan will flag endpoints where JWT authentication exists but role or ownership checks are missing, aligning findings with compliance mappings in the Web Dashboard. The Pro plan enables continuous monitoring to catch regressions, and the GitHub Action can fail builds if the risk score drops below your chosen threshold.