Insufficient Logging in Fiber

Insufficient logging in Fiber applications creates blind spots that attackers exploit to maintain persistent access and evade detection. The problem manifests in several Fiber-specific ways that developers often overlook.

Fiber's middleware-based architecture means logging gaps can occur at critical request boundaries. When developers implement custom authentication middleware without comprehensive logging, successful and failed authentication attempts disappear. Consider this common pattern:

app.Use(func(c *fiber.Ctx) error {
    // Custom auth logic
    token := c.Get("Authorization")
    if token == "" {
        return c.Status(fiber.StatusUnauthorized).SendString("Missing token")
    }
    // No logging of auth failures
    return c.Next()
})

This creates perfect conditions for credential stuffing attacks. Attackers can hammer authentication endpoints without leaving forensic evidence. The absence of failed login logging means security teams cannot detect brute force attempts or identify compromised accounts.

API endpoint abuse represents another critical manifestation. Fiber's lightweight routing makes it easy to expose endpoints without proper access logging. A typical vulnerable pattern:

app.Post("/api/user", func(c *fiber.Ctx) error {
    // Create user without logging who created it
    return c.JSON(fiber.Map{"status": "created"})
})

Without logging user creation events with context (IP address, user agent, request ID), organizations cannot investigate data breaches or meet compliance requirements. The GDPR's Article 30 specifically requires processing activity logs that include "the identification of the data subject and of the recipients."

Missing request ID correlation across distributed systems compounds the problem. Fiber applications often integrate with databases, external APIs, and microservices. Without consistent request ID propagation:

app.Use(func(c *fiber.Ctx) error {
    // Missing request ID generation
    return c.Next()
})

Security incidents become impossible to reconstruct. When a data breach occurs, investigators cannot trace the malicious request through the entire call chain.

Silent error handling creates another vulnerability class. Fiber's error handling can swallow exceptions without logging:

app.Use(func(c *fiber.Ctx) error {
    defer func() {
        if r := recover(); r != nil {
            // Error swallowed without logging
            return c.Status(fiber.StatusInternalServerError).SendString("Error")
        }
    }()
    return c.Next()
})

This pattern allows attackers to trigger errors that reveal system information through timing or side channels while leaving no audit trail.

Detecting insufficient logging in Fiber applications requires both static analysis and runtime scanning. middleBrick's black-box scanning approach is particularly effective for identifying logging gaps that static analysis might miss.

middleBrick's authentication testing reveals missing login attempt logging by attempting to authenticate with invalid credentials and analyzing the responses. A Fiber application with insufficient logging typically shows:

• No variation in response times between valid and invalid credentials (indicating no backend logging)
• Generic error messages that don't distinguish between "invalid password" and "account locked"
• Consistent response codes regardless of authentication failure type

The scanner's BOLA (Broken Object Level Authorization) testing exposes missing authorization logging. middleBrick attempts to access resources across user boundaries and analyzes whether the application provides different responses that could indicate successful or failed authorization checks without proper logging.

For real-time detection, implement request logging middleware that captures Fiber's request lifecycle:

app.Use(func(c *fiber.Ctx) error {
    start := time.Now()
    
    // Generate unique request ID
    reqID := uuid.New().String()
    c.Locals("requestID", reqID)
    c.Response().Header.Set("X-Request-ID", reqID)
    
    // Log request start
    log.WithFields(logrus.Fields{
        "request_id": reqID,
        "method": c.Method(),
        "path": c.Path(),
        "remote_addr": c.IP(),
        "user_agent": c.Get("User-Agent"),
    }).Info("request started")
    
    err := c.Next()
    
    // Calculate duration
    duration := time.Since(start)
    
    // Log request completion
    log.WithFields(logrus.Fields{
        "request_id": reqID,
        "status": c.Response().StatusCode(),
        "duration": duration.Milliseconds(),
        "error": err != nil,
    }).Info("request completed")
    
    return err
})

This middleware provides the baseline observability that middleBrick expects when scanning for security issues. Applications without this level of logging typically receive lower security scores.

middleBrick's API specification analysis cross-references your OpenAPI/Swagger definitions with actual runtime behavior. Missing logging for documented endpoints triggers findings, as the spec implies certain operations should be auditable.

The scanner's rate limiting detection also reveals insufficient logging. Applications without proper request volume logging cannot implement effective rate limiting, making them vulnerable to DoS attacks and credential stuffing.

Remediating insufficient logging in Fiber applications requires implementing comprehensive audit trails that capture security-relevant events. Start with structured logging using a consistent format:

package logging

import (
    "time"
    "github.com/gofiber/fiber"
    "github.com/sirupsen/logrus"
)

func AuditLogger() fiber.Handler {
    return func(c *fiber.Ctx) error {
        reqID := c.Locals("requestID").(string)
        
        // Authentication events
        if c.Method() == "POST" && strings.Contains(c.Path(), "auth") {
            user := c.FormValue("username")
            success := c.Response().StatusCode() == fiber.StatusNoContent || c.Response().StatusCode() == fiber.StatusOK
            
            logrus.WithFields(logrus.Fields{
                "request_id": reqID,
                "user": user,
                "success": success,
                "remote_addr": c.IP(),
                "user_agent": c.Get("User-Agent"),
                "timestamp": time.Now().UTC(),
            }).Infof("authentication %s", map[bool]string{true: "success", false: "failure"}[success])
        }
        
        // Authorization events
        if c.Response().StatusCode() == fiber.StatusForbidden || c.Response().StatusCode() == fiber.StatusUnauthorized {
            logrus.WithFields(logrus.Fields{
                "request_id": reqID,
                "path": c.Path(),
                "method": c.Method(),
                "remote_addr": c.IP(),
                "user_agent": c.Get("User-Agent"),
                "timestamp": time.Now().UTC(),
            }).Warn("authorization failure")
        }
        
        // Data modification events
        if c.Method() == "POST" || c.Method() == "PUT" || c.Method() == "DELETE" {
            logrus.WithFields(logrus.Fields{
                "request_id": reqID,
                "path": c.Path(),
                "method": c.Method(),
                "remote_addr": c.IP(),
                "user_agent": c.Get("User-Agent"),
                "timestamp": time.Now().UTC(),
            }).Infof("%s operation performed", strings.ToUpper(c.Method()))
        }
        
        return c.Next()
    }
}

Integrate this middleware early in your application stack:

app.Use(RequestIDMiddleware())
app.Use(AuditLogger())
app.Use(RecoveryMiddleware())

For structured logging output compatible with security information and event management (SIEM) systems:

import (
    "time"
    "github.com/gofiber/fiber"
    "github.com/sirupsen/logrus"
    "encoding/json"
)

type AuditEvent struct {
    Timestamp   time.Time `json:"timestamp"`
    RequestID   string    `json:"request_id"`
    UserID      string    `json:"user_id,omitempty"`
    Action      string    `json:"action"`
    Resource    string    `json:"resource"`
    Method      string    `json:"method"`
    Status      int       `json:"status"`
    IPAddress   string    `json:"ip_address"`
    UserAgent   string    `json:"user_agent"`
    Success     bool      `json:"success"`
    Details     string    `json:"details,omitempty"`
}

func StructuredAuditLogger() fiber.Handler {
    return func(c *fiber.Ctx) error {
        // Implementation that marshals AuditEvent to JSON
        return c.Next()
    }
}

middleBrick's continuous monitoring in Pro tier helps verify that logging implementations meet security standards. The scanner checks that audit logs capture:

• All authentication attempts with success/failure status
• Authorization failures with attempted resource paths
• Data modification operations with user context
• Application errors with stack traces (in non-production environments)
• Rate limiting events and blocked requests

Integrate logging with your CI/CD pipeline using middleBrick's GitHub Action. Configure it to fail builds if new endpoints lack proper audit logging:

jobs:
  security:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Run middleBrick Scan
        uses: middlebrick/middlebrick-action@v1
        with:
          url: http://localhost:3000
          fail-on-severity: high
          token: ${{ secrets.MIDDLEBRICK_TOKEN }}
        # Fails if logging gaps are detected