Broken Access Control in Echo Go with Bearer Tokens

Broken Access Control occurs when application logic fails to enforce proper authorization between different users or roles. In Echo Go, combining Bearer Tokens with insufficient route-level checks creates a common attack surface. Developers often validate the presence of a token but omit per-route ownership or role checks, enabling BOLA/IDOR-style access where one user can act on another’s resources.

Echo Go projects typically rely on middleware to extract and validate Bearer Tokens. If middleware attaches user claims (e.g., user ID, role) to the context but subsequent handlers do not verify that the requesting user is allowed to access the targeted resource, the API exposes a Broken Access Control flaw. For example, an endpoint like /users/{id} that returns user details must ensure the authenticated user’s ID matches the {id} path parameter, not just require any valid Bearer Token.

Real-world parallels exist in findings from scans testing unauthenticated attack surfaces: missing authorization checks in routes that accept Bearer Tokens are flagged under BOLA/IDOR and Property Authorization checks. Attackers can modify numeric or UUID identifiers in paths or query parameters to access other users’ data, even when tokens are valid. This aligns with OWASP API Top 10 A01:2023 broken access control, and can map to compliance frameworks such as PCI-DSS and SOC2 where access restrictions are required.

Consider an Echo Go route that retrieves account information without validating ownership:

// Insecure example: missing ownership check
func GetAccount(c echo.Context) error {
    userID := c.Get("user_id") // from middleware claim
    requestedID := c.Param("id")
    var account Account
    if err := db.Where("id = ?", requestedID).First(&account).Error; err != nil {
        return c.JSON(http.StatusNotFound, map[string]string{"error": "not found"})
    }
    return c.JSON(http.StatusOK, account)
}

In this snippet, any authenticated user with a valid Bearer Token can supply any numeric ID and potentially access accounts belonging to others. The fix is to compare userID and requestedID before proceeding. Without this check, the API’s authentication (Bearer Token presence) is decoupled from authorization (resource ownership), resulting in a Broken Access Control vulnerability.

Remediation centers on enforcing authorization at the handler or middleware level by comparing the authenticated subject with the requested resource. Below are concrete, secure patterns for Echo Go using Bearer Tokens.

1) Enforce ownership in the handler

After extracting user claims in middleware, always validate that the claim matches the resource identifier in the route.

// Secure example: enforce ownership
func GetAccount(c echo.Context) error {
    userID := c.Get("user_id") // e.g., string or numeric ID from JWT claims
    requestedID := c.Param("id")
    if userID != requestedID {
        return c.JSON(http.StatusForbidden, map[string]string{"error": "access denied"})
    }
    var account Account
    if err := db.Where("id = ?", requestedID).First(&account).Error; err != nil {
        return c.JSON(http.StatusNotFound, map[string]string{"error": "not found"})
    }
    return c.JSON(http.StatusOK, account)
}

This ensures that even with a valid Bearer Token, users can only access their own account records, mitigating BOLA/IDOR.

2) Centralized middleware authorization for role-based access

For role-based scenarios, use middleware to enforce policies before reaching handlers. This example demonstrates role checks with Bearer Tokens in Echo Go.

// Role-based authorization middleware
func RoleRequired(role string) echo.MiddlewareFunc {
    return func(next echo.HandlerFunc) echo.HandlerFunc {
        return func(c echo.Context) error {
            userRole := c.Get("role") // set by prior auth middleware
            if userRole != role {
                return c.JSON(http.StatusForbidden, map[string]string{"error": "insufficient permissions"})
            }
            return next(c)
        }
    }
}

// Usage on a route
app.GET("/admin/dashboard", RoleRequired("admin"), func(c echo.Context) error {
    return c.JSON(http.StatusOK, map[string]string{"message": "admin area"})
})

Ensure your authentication middleware that validates Bearer Tokens sets claims such as user_id and role on the context, so downstream handlers and middleware can rely on them.

3) Input validation and canonicalization

Normalize identifiers (e.g., trim spaces, case-fold when appropriate) and validate format before using them in queries. For UUID paths:

// Validate UUID format to avoid ID manipulation
func IsValidUUID(u string) bool {
    _, err := uuid.Parse(u)
    return err == nil
}

func GetProfile(c echo.Context) error {
    userID := c.Param("id")
    if !IsValidUUID(userID) {
        return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid id"})
    }
    // proceed only if authenticated user ID matches userID
    if c.Get("user_id") != userID {
        return c.JSON(http.StatusForbidden, map[string]string{"error": "access denied"})
    }
    var profile Profile
    if err := db.Where("id = ?", userID).First(&profile).Error; err != nil {
        return c.JSON(http.StatusNotFound, map[string]string{"error": "not found"})
    }
    return c.JSON(http.StatusOK, profile)
}

These patterns align with remediations reflected in scans that test unauthenticated attack surfaces, where weak or missing authorization checks are surfaced. Implementing ownership checks and role middleware reduces the risk of Broken Access Control while continuing to rely on Bearer Tokens for authentication.