Vulnerable Components in Chi with Jwt Tokens

Chi is a lightweight HTTP router for Go that is commonly used to build APIs. When JWT tokens are used for authorization without strict validation, the combination can expose several classes of vulnerabilities. These include weak signature verification, missing audience/issuer checks, and improper handling of token claims, which can lead to IDOR, authentication bypass, and privilege escalation.

One common pattern is to retrieve the token from the Authorization header and parse it using a shared secret or public key. If the verification step omits required validation such as aud (audience), iss (issuer), or exp (expiration), an attacker can reuse a token issued for one resource to access another. This maps to the BOLA/IDOR category in middleBrick’s checks, where insecure direct object references arise from insufficient authorization at the token level.

Another risk arises when applications use insecure signing algorithms, such as none or HS256 when expecting RS256. An attacker who can control the key or algorithm parameters might forge valid JWT tokens. middleBrick’s Authentication and BFLA/Privilege Escalation checks test for these algorithm confusion and weak key management scenarios, which can lead to unauthorized access across user boundaries.

Claims manipulation is also a concern. If a token contains roles or scopes in the payload and the server does not re-verify authorization on each request, an attacker modifying claims (e.g., changing role from user to admin) can gain elevated permissions. This is especially risky when applications decode the JWT without verifying the signature or when using insecure libraries that do not enforce strict claim validation by default.

Unauthenticated LLM endpoints can compound these issues if JWT-protected routes are inadvertently exposed to public inference endpoints. middleBrick’s LLM/AI Security checks detect whether endpoints that should require authentication are accessible without valid tokens, which could allow an attacker to probe or interact with protected functionality through AI-assisted tooling.

Finally, token leakage in logs, error messages, or client-side storage can lead to data exposure. middleBrick’s Data Exposure and Encryption checks identify whether JWT tokens are transmitted over non-encrypted channels or reflected in responses, which could enable interception or replay attacks.

To secure JWT usage in Chi, enforce strict validation of all token claims and use strong, verified cryptographic signing. Below are concrete code examples that demonstrate secure handling using the github.com/golang-jwt/jwt/v5 package.

First, define a claims structure that includes standard fields and validation logic:

type CustomClaims struct {
    UserID string `json:"user_id"`
    Role   string `json:"role"`
    jwt.RegisteredClaims
}

When parsing and verifying a token, always specify the expected signing method, issuer, audience, and required claims:

func VerifyToken(tokenString, secret string, expectedIssuer, expectedAudience string) (*CustomClaims, error) {
    token, err := jwt.ParseWithClaims(tokenString, &CustomClaims{}, func(token *jwt.Token) (interface{}, error) {
        if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
            return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
        }
        return []byte(secret), nil
    }, jwt.WithIssuer(expectedIssuer), jwt.WithAudience(expectedAudience))

    if err != nil {
        return nil, err
    }
    if claims, ok := token.Claims.(*CustomClaims); ok && token.Valid {
        if claims.ExpiresAt == nil || claims.ExpiresAt.Before(time.Now()) {
            return nil, errors.New("token expired")
        }
        return claims, nil
    }
    return nil, errors.New("invalid claims")
}

This approach ensures that the token is not only properly signed but also bound to the expected issuer and audience, mitigating token reuse across services. It also explicitly checks expiration time to prevent use of stale tokens.

In Chi routes, integrate the verification function before allowing access to protected handlers:

func ProtectedHandler(c chi.Context) {
    tokenString := c.Request.Header.Get("Authorization")
    if tokenString == "" {
        http.Error(c.ResponseWriter, "missing authorization header", http.StatusUnauthorized)
        return
    }
    // Remove Bearer prefix if present
    tokenString = strings.TrimPrefix(tokenString, "Bearer ")

    claims, err := VerifyToken(tokenString, os.Getenv("JWT_SECRET"), "my-service", "api.example.com")
    if err != nil {
        http.Error(c.ResponseWriter, "invalid token", http.StatusUnauthorized)
        return
    }

    // Enforce role-based authorization at the handler level
    if claims.Role != "admin" {
        http.Error(c.ResponseWriter, "insufficient permissions", http.StatusForbidden)
        return
    }

    c.JSON(http.StatusOK, map[string]string{"user_id": claims.UserID, "role": claims.Role})
}

Additionally, prefer RS256 or ES256 over HS256 for asymmetric signing, and rotate keys according to your organization’s policy. When using public keys, load them securely (e.g., via JWKS endpoint) and validate the key ID (kid) in the header against an allowlist. middleBrick’s Pro plan supports continuous monitoring and CI/CD integration to ensure these practices are consistently enforced across your API surface.