Fix Command Injection in Buffalo

Buffalo applications are susceptible to Command Injection when user-controlled input (from params, headers, or body) is passed unsanitized into system execution functions. If you're invoking the shell to run binaries, you're inviting RCE. Real-world exploitation involves chaining shell metacharacters to hijack the execution flow.

The Vulnerable Pattern

func (v *HomeResource) Execute(c buffalo.Context) error {
	// DANGER: User input is concatenated directly into a shell string
	command := c.Param("cmd")
	cmd := exec.Command("sh", "-c", "echo " + command)
	out, _ := cmd.CombinedOutput()
	return c.Render(200, r.String(string(out)))
}

The Secure Implementation

The vulnerability exists because 'sh -c' treats the entire following string as a shell command, allowing an attacker to use characters like ';', '&', or '|' to execute arbitrary commands. By removing the shell intermediary and passing arguments directly to exec.Command, Go's syscalls treat the input as a literal string argument for the target binary rather than executable code. For maximum security, implement a strict allowlist for input and use absolute paths to prevent PATH hijacking.

func (v *HomeResource) Execute(c buffalo.Context) error {
	command := c.Param("cmd")
// 1. Avoid 'sh -c' entirely to prevent shell expansion
// 2. Pass arguments as distinct elements in the slice
// 3. Use an absolute path for the binary
cmd := exec.Command("/usr/bin/echo", command)

out, err := cmd.CombinedOutput()
if err != nil {
	return c.Error(500, err)
}
return c.Render(200, r.String(string(out)))
}