Command Injection in Fiber with Cockroachdb

Command injection occurs when untrusted input is concatenated into an operating system command executed by the application. In a Fiber application that interacts with CockroachDB, this risk arises when query parameters or request payloads are improperly passed to shell commands—such as during dynamic schema migrations, backup orchestration, or external tooling invoked via exec.Command. For example, if a handler builds a CockroachDB SQL string by directly interpolating user-controlled values (e.g., table names or filter values) into a shell command, an attacker can inject additional shell operators like ; or && to execute arbitrary system instructions.

Fiber’s fast, unopinionated routing can inadvertently encourage concatenation patterns that mix HTTP input with system commands. Consider a scenario where an endpoint triggers a CockroachDB logical backup using an external binary, and the backup target is derived from a request parameter. If the parameter is not strictly validated, an attacker might supply ?target=injected; drop table users--, causing the shell to execute malicious instructions. Even when using CockroachDB’s native drivers, unsafe usage of os/exec to run cockroach CLI utilities introduces a path for injection. The database driver itself is not at fault, but the surrounding orchestration layer becomes vulnerable when input is treated as code rather than data.

Common vulnerable patterns include:

• Using sh -c with string interpolation to pass SQL statements or identifiers.
• Building cockroach sql or cockroach dump commands by concatenating user input into command arguments.
• Relying on default shell splitting behavior when passing multi-token arguments.

Because middleBrick scans test the unauthenticated attack surface, endpoints that expose command-injection-prone behavior—such as debug or administrative endpoints interacting with CockroachDB—can be detected through runtime probes that monitor unexpected process execution or error patterns.

To eliminate command injection when using CockroachDB with Fiber, avoid constructing shell commands from user input entirely. Instead, use the CockroachDB Go driver to send parameterized queries directly, and restrict any external command invocation to strictly controlled inputs. Below are concrete, safe implementations.

1. Use the CockroachDB Go driver with parameterized queries

Always use prepared statements or parameterized queries to separate SQL logic from data. This prevents injection at the database layer and removes the need for shell-based command construction.

package main

import (
	"context"
	"fmt"
	"log"
	"net/http"

	"github.com/gofiber/fiber/v2"
	"github.com/lib/pq"
	_ "github.com/cockroachdb/postgresdriver"
)

func main() {
	app := fiber.New()

	app.Get("/user/:id", func(c *fiber.Ctx) error {
		userID := c.Params("id")
		// Safe: parameterized query with CockroachDB-compatible driver
		query := "SELECT username, email FROM users WHERE id = $1"
		row := db.QueryRowContext(c.Context(), query, userID)

		var username, email string
		if err := row.Scan(&username, &email); err != nil {
			return c.Status(http.StatusInternalServerError).SendString("Database error")
		}
		return c.JSON(fiber.Map{"username": username, "email": email})
	})

	log.Fatal(app.Listen(":3000"))
}

2. Avoid shell execution for CockroachDB operations

If you must invoke cockroach CLI (for instance, to run diagnostics), validate and sanitize all inputs and avoid the shell. Use explicit argument lists instead of a single command string.

package main

import (
	"context"
	"log"
	"os/exec"

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

func runCockroachSQL(args ...string) error {
	// Safe: explicit arguments, no shell interpretation
	cmd := exec.CommandContext(context.Background(), "cockroach", args...)
	// cmd.Env can be set if needed
	out, err := cmd.Output()
	if err != nil {
		return fmt.Errorf("cockroach command failed: %w, output: %s", err, out)
	}
	return nil
}

func main() {
	app := fiber.New()

	app.Post("/migrate", func(c *fiber.Ctx) error {
		// Validate input strictly: allow only alphanumeric and underscores for table names
		tableName := c.FormValue("table")
		if !isValidTableName(tableName) {
			return c.Status(fiber.StatusBadRequest).SendString("invalid table name")
		}
		if err := runCockroachSQL("sql", "--execute", fmt.Sprintf("ALTER TABLE %s ADD COLUMN migrated BOOLEAN", tableName)); err != nil {
			return c.Status(fiber.StatusInternalServerError).SendString("migration failed")
		}
		return c.SendStatus(fiber.StatusOK)
	})

	log.Fatal(app.Listen(":3000"))
}

func isValidTableName(s string) bool {
	for _, r := range s {
		if !(r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z' || r == '_') {
			return false
		}
	}
	return s != ""
}

3. Apply defense-in-depth with input validation and least privilege

Define strict allowlists for identifiers, use context timeouts, and ensure the CockroachDB role used by Fiber has minimal required privileges. This reduces impact even if an injection vector is overlooked.

middleBrick’s scans can help identify endpoints that invoke external processes or exhibit patterns consistent with command injection, providing prioritized findings and remediation guidance aligned with frameworks such as OWASP API Top 10.