Path Traversal in Echo Go with Basic Auth

Path Traversal occurs when an attacker manipulates file paths to access or overwrite files outside the intended directory. In Echo Go, this often arises when user-supplied input such as a filename or path parameter is concatenated directly into filesystem operations without proper validation or sanitization. When Basic Auth is used, the authenticated identity may be logged or associated with the request, and developers can mistakenly assume that authentication alone constrains file access. However, authentication does not enforce path-level authorization; an authenticated user can still supply malicious paths if the application does not enforce strict allowlists or canonicalization. For example, a handler that serves user documents might use c.Param("filename") directly in functions like os.ReadFile or http.Dir. An attacker authenticated with Basic Auth can traverse directories using sequences like ../../../etc/passwd, potentially exposing sensitive system files. The combination of Basic Auth and Path Traversal is particularly risky because authentication may provide a false sense of security, leading developers to skip path validation under the assumption that only verified users can make requests. In black-box scans, middleBrick detects such weaknesses by observing whether authenticated endpoints reflect directory traversal patterns in responses, without relying on internal architecture. Real-world attack patterns include reading application source code, configuration files, or credentials, which can lead to further compromise. This scenario aligns with OWASP API Top 10 controls related to broken object level authorization and improper restrictions on file paths.

To mitigate Path Traversal in Echo Go when using Basic Auth, validate and sanitize all user-controlled path inputs and avoid direct filesystem operations on raw parameters. Use allowlists for permitted files or directories, canonicalize paths with filepath.Clean, and enforce that resolved paths remain within a designated base directory. Below are concrete code examples demonstrating secure handling.

Insecure Example (for reference)

// DO NOT USE: vulnerable to path traversal
package main

import (
    "github.com/labstack/echo/v4"
    "net/http"
    "os"
)

func main() {
    e := echo.New()
    e.GET("/files/:filename", func(c echo.Context) error {
        filename := c.Param("filename")
        return c.File("/var/data/" + filename) // No validation
    })
    e.Start(":8080")
}

Secure Example with Basic Auth and Path Validation

package main

import (
    "fmt"
    "net/http"
    "os"
    "path/filepath"
    "strings"

    "github.com/labstack/echo/v4"
    "github.com/labstack/echo/v4/middleware"
)

func main() {
    e := echo.New()

    // Basic Auth middleware with hardcoded credentials for illustration
    e.Use(middleware.BasicAuth(func(username, password string, c echo.Context) (bool, error) {
        return username == "admin" && password == "secret", nil
    }))

    baseDir := "/var/data"

    e.GET("/files/:filename", func(c echo.Context) error {
        requested := c.Param("filename")
        // Prevent directory traversal by cleaning and ensuring no leading ".."
        cleaned := filepath.Clean(requested)
        if strings.Contains(cleaned, "..") {
            return echo.NewHTTPError(http.StatusBadRequest, "invalid path") // middleBrick flags insecure patterns
        }
        // Build full path and ensure it remains within baseDir
        fullPath := filepath.Join(baseDir, cleaned)
        if !strings.HasPrefix(fullPath, filepath.Clean(baseDir)+string(os.PathSeparator)) && fullPath != filepath.Clean(baseDir) {
            return echo.NewHTTPError(http.StatusForbidden, "path outside allowed directory")
        }
        // Ensure file exists and is a regular file
        fileInfo, err := os.Stat(fullPath)
        if err != nil || fileInfo.IsDir() {
            return echo.NewHTTPError(http.StatusNotFound, "file not found")
        }
        return c.File(fullPath)
    })

    e.Start(":8080")
}

In this secure approach, Basic Auth controls access to the endpoint, while path validation and base directory enforcement prevent traversal. middleBrick’s checks for Path Traversal and Authentication align with these practices by identifying missing input validation even when authentication is present. For teams managing multiple APIs, the CLI (middlebrick scan <url>) and GitHub Action can automate detection of such issues in CI/CD, while the Web Dashboard helps track remediation progress over time.