Zip Slip in Echo Go with Api Keys

Zip Slip is a path traversal vulnerability that occurs when an API constructs file paths using user-supplied input without proper validation. In Echo Go, this risk is amplified when API keys are handled through path-based parameters or when uploaded files are extracted without canonicalization. If an endpoint accepts a filename or archive entry name from a request header such as X-API-Key or uses the key as part of a filename, an attacker can supply crafted input like ../../../etc/passwd or a malicious archive containing path traversal sequences. During extraction, the server may resolve the path outside the intended directory, exposing configuration files, logs, or other sensitive artifacts that may themselves contain API keys or secrets.

Even when API keys are stored securely, the combination of Zip Slip and Echo Go routing can create indirect exposure. For example, an endpoint that downloads an archive using a key-derived subdirectory may traverse into parent directories if input is not sanitized, inadvertently exposing keys stored in parent folders or backup locations. Because Echo Go does not inherently sanitize archive entries, developers must explicitly validate and restrict file paths. Without such controls, an attacker who can influence archive contents or filenames can leverage Zip Slip to read arbitrary files, potentially discovering hardcoded or poorly managed API keys that should never be accessible through file reads.

In practice, this means any Echo Go service that accepts file uploads or archive processing alongside API key usage must treat user input as hostile. The vulnerability is not in Echo Go itself but in how developers integrate file handling with key management. A malicious archive with entries like ../../../../api-keys/production.txt can escape the extraction sandbox if path cleaning is omitted. Once outside the sandbox, sensitive data protected by API keys may be exposed through predictable file locations, especially when backups or configuration directories are co-located with application assets.

To mitigate Zip Slip in Echo Go when working with API keys, ensure all file paths are sanitized and confined to a designated directory. Use Go’s path/filepath package to clean and validate paths before extraction. The following example demonstrates a secure handler that prevents directory traversal and protects API key storage:

package main

import (
    "archive/zip"
    "io"
    "net/http"
    "os"
    "path/filepath"

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

const allowedPrefix = "uploads/keys/"

func safeExtractZip(c echo.Context) error {
    file, err := c.FormFile("archive")
    if err != nil {
        return echo.NewHTTPError(http.StatusBadRequest, "invalid archive")
    }

    src, err := file.Open()
    if err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError, "cannot open archive")
    }
    defer src.Close()

    zipReader, err := zip.NewReader(src, file.Size)
    if err != nil {
        return echo.NewHTTPError(http.StatusBadRequest, "not a valid zip")
    }

    for _, f := range zipReader.File {
        // Clean and validate each entry path
        cleaned := filepath.Clean(f.Name)
        if !filepath.IsAbs(cleaned) {
            cleaned = filepath.Join(allowedPrefix, cleaned)
        }
        if !filepath.HasPrefix(cleaned, filepath.Clean(allowedPrefix)) {
            return echo.NewHTTPError(http.StatusForbidden, "invalid file path")
        }

        if err := os.MkdirAll(filepath.Dir(cleaned), 0750); err != nil {
            return echo.NewHTTPError(http.StatusInternalServerError, "cannot create directory")
        }

        if f.FileInfo().IsDir() {
            continue
        }

        rc, err := f.Open()
        if err != nil {
            return echo.NewHTTPError(http.StatusInternalServerError, "cannot open file")
        }
        defer rc.Close()

        dst, err := os.OpenFile(cleaned, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, f.Mode())
        if err != nil {
            return echo.NewHTTPError(http.StatusInternalServerError, "cannot create file")
        }
        defer dst.Close()

        if _, err = io.Copy(dst, rc); err != nil {
            return echo.NewHTTPError(http.StatusInternalServerError, "extraction failed")
        }
    }
    return c.JSON(http.StatusOK, echo.Map{"status": "ok"})
}

func main() {
    e := echo.New()
    e.POST("/extract", safeExtractZip)
    e.Start(":8080")
}

Additionally, store API keys outside the web-accessible directory tree and avoid deriving storage paths from user-controlled values such as filenames or headers. If your service must use API keys in filenames, sanitize them by removing path separators and using a mapping table instead of raw key values. This prevents attackers from injecting traversal sequences even if they compromise key naming conventions.

For automated scanning of such patterns in CI/CD, the middleBrick GitHub Action can be configured to fail builds if risky file handling patterns are detected in your Echo Go codebase, helping catch Zip Slip and similar issues before deployment.