Symlink Attack in Fiber with Cockroachdb

A Symlink Attack in a Fiber service that uses Cockroachdb typically occurs when an API endpoint accepts user-supplied paths or filenames and uses them to build filesystem operations that affect Cockroachdb-related files, backups, or external storage mounts. In this combination, the web framework (Fiber) may pass unchecked user input to file system utilities or command execution routines that interact with Cockroachdb data directories, configuration files, or backup scripts. An attacker can supply a path that traverses directories and points to a sensitive location, such as a Cockroachdb TLS certificate file or a node startup configuration, and then trigger downstream behavior that exposes or modifies critical database assets.

Because Cockroachdb often runs as a separate cluster with its own data directories and configuration, a symlink crafted via a vulnerable Fiber endpoint can redirect writes or reads to attacker-controlled locations. For example, if the application uses a user-provided filename to construct a Cockroachdb connection string or a backup archive path, a malicious path like ../../../cockroach-data/cluster.crt can cause the application to read or overwrite sensitive files. This can lead to unauthorized access to encryption materials, credential leakage, or manipulation of backup artifacts. The vulnerability is not in Cockroachdb itself but in how the Fiber application handles paths before invoking Cockroachdb tooling or scripts.

OpenAPI/Swagger spec analysis can reveal endpoints that accept path-like parameters without strict schema constraints. When such parameters are used to invoke Cockroachdb-related scripts or configure runtime paths, the unauthenticated attack surface includes the possibility of symlink-based information disclosure or unauthorized file operations. Because scanning with middleBrick includes checks for BOLA/IDOR and Property Authorization alongside Input Validation, it can highlight endpoints where user-controlled data influences filesystem interactions with Cockroachdb resources. This helps identify whether a Symlink Attack vector exists in the integration between Fiber and Cockroachdb.

To remediate symlink risks in a Fiber application that interacts with Cockroachdb, validate and sanitize all user input used in filesystem paths or command construction. Use strict allowlists for filenames and reject path traversal sequences. When generating paths to Cockroachdb assets, resolve and restrict them to a predefined base directory.

package main

import (
	"fmt"
	"io/fs"
	"net/http"
	"path/filepath"
	"strings"

	"github.com/gofiber/fiber/v2"
)

// baseDir is the only directory allowed for Cockroachdb-related files.
const baseDir = "/safe/cockroach/assets"

func safeCockroachHandler(c *fiber.Ctx) error {
	filename := c.Query("file")
	if filename == "" {
		return c.Status(http.StatusBadRequest).SendString("file query parameter is required")
	}

	// Reject path traversal and disallowed separators
	if strings.Contains(filename, "..") || strings.Contains(filename, "\x00") {
		return c.Status(http.StatusBadRequest).SendString("invalid filename")
	}

	// Clean and resolve path strictly under baseDir
	cleanName := filepath.Clean(filename)
	target := filepath.Join(baseDir, cleanName)
	if !strings.HasPrefix(target, filepath.Clean(baseDir)+string(fs.Separator)) && target != filepath.Clean(baseDir) {
		return c.Status(http.StatusForbidden).SendString("path outside allowed directory")
	}

	// Use target only for allowed Cockroachdb asset types
	ext := strings.ToLower(filepath.Ext(target))
	if ext != ".crt" && ext != ".key" && ext != ".sql" {
		return c.Status(http.StatusBadRequest).SendString("file type not allowed")
	}

	// Example: read a Cockroachdb certificate safely
	data, err := os.ReadFile(target)
	if err != nil {
		return c.Status(http.StatusInternalServerError).SendString("unable to read file")
	}

	return c.Send(data)
}

func main() {
	app := fiber.New()
	app.Get("/cockroach-asset", safeCockroachHandler)
	app.Listen(":3000")
}

This approach ensures that any request for a Cockroachdb asset cannot escape the designated directory, mitigating symlink risks. middleBrick’s scans can verify that endpoints like this enforce strict path validation and do not expose sensitive directories. For ongoing protection, use the middleBrick CLI to scan from terminal with middlebrick scan <url> or integrate the GitHub Action to add API security checks to your CI/CD pipeline, failing builds if risky path handling is detected. In distributed setups, the Pro plan supports continuous monitoring and can alert teams when changes affect how endpoints interact with Cockroachdb configurations.