Injection Flaws in Echo Go with Basic Auth

When an Echo Go service uses HTTP Basic Authentication and also builds dynamic responses or queries using user-influenced data, the two controls interact in ways that can amplify injection risks. Basic Auth provides a simple authentication layer, but it does not prevent an authenticated handler from introducing injection problems. If credentials are accepted in a header and then concatenated into a shell command, SQL string, LDAP filter, or system call, the combination can expose the application to command injection, SQL injection, and LDAP injection.

Consider a scenario where the username or password extracted from the Basic Auth header is used to construct a command or a query without proper validation or parameterization. For example, extracting credentials via the Authorization header and passing them directly into a system command or a raw SQL string creates a path for attackers to escape intended boundaries. Even when the endpoint returns a 401 for invalid credentials, the handler logic that processes credentials becomes the attack surface if it is not isolated from data execution paths.

Input validation and output encoding must be applied to any data derived from the request, including the identity expressed through Basic Auth. Without encoding, an attacker who can influence the credentials (e.g., via a compromised client or a misconfigured reverse proxy) may be able to inject malicious content into logs, error messages, or downstream systems. In distributed setups, misconfigured proxies might inadvertently forward headers in a way that exposes credentials to components that do not expect them, increasing the likelihood of injection through trusted internal channels.

In the context of the 12 checks run by middleBrick, the scanner tests unauthenticated attack surfaces and looks for indicators that credentials or other identifiers are used in constructing executable commands or queries. Even without authentication, patterns such as command concatenation with user-controlled strings or unsafe string formatting can be detected. The scanner also examines whether sensitive data derived from authentication contexts is properly protected and whether error handling leaks information that could aid injection or bypass attempts.

For LLM-related endpoints, injection concerns extend to prompt injection when credentials or identifiers are reflected in prompts used by language models. If Basic Auth-derived values are included in prompts without sanitization, an attacker may attempt prompt injection or data exfiltration. middleBrick’s LLM/AI Security checks include active prompt injection testing and output scanning to detect whether credentials or other sensitive data appear in model responses, helping identify cases where authentication data interacts with AI components insecurely.

Secure handling of Basic Authentication in Echo Go requires strict separation between authentication and business logic, along with canonicalization and parameterization of any data used in commands, queries, or external interfaces. Avoid using credentials directly in system commands or raw SQL strings. Instead, map credentials to internal identifiers or permissions and use prepared statements and structured queries.

Below are concrete Go code examples illustrating secure approaches. The first example shows how to safely extract and validate credentials without exposing them to injection-prone contexts. The second demonstrates using parameterized SQL queries, and the third shows how to avoid concatenating credentials into shell commands.

// Safe extraction and validation in Echo Go
func validateCredentials(username, password string) bool {
    // Canonicalize inputs: trim spaces, enforce length limits, and normalize encoding
    username = strings.TrimSpace(username)
    password = strings.TrimSpace(password)
    if username == "" || password == "" {
        return false
    }
    // Use constant-time comparison for secrets when possible
    return checkPasswordHash(username, password)
}

func loginHandler(c echo.Context) error {
    auth := c.Request().Header.Get("Authorization")
    if auth == "" {
        return c.JSON(http.StatusUnauthorized, map[string]string{"error": "authorization header required"})
    }
    const prefix = "Basic "
    if !strings.HasPrefix(auth, prefix) {
        return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid authorization type"})
    }
    payload, err := base64.StdEncoding.DecodeString(auth[len(prefix):])
    if err != nil {
        return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid authorization encoding"})
    }
    parts := strings.SplitN(string(payload), ":", 2)
    if len(parts) != 2 {
        return c.JSON(http.StatusBadRequest, map[string]string{"error": "malformed credentials"})
    }
    if !validateCredentials(parts[0], parts[1]) {
        return c.JSON(http.StatusUnauthorized, map[string]string{"error": "invalid credentials"})
    }
    // Proceed with authenticated logic using mapped identities, not raw credentials
    return c.JSON(http.StatusOK, map[string]string{"status": "authenticated"})
}

// Parameterized query example
db, err := sql.Open("postgres", connStr)
if err != nil {
    log.Fatal(err)
}
defer db.Close()

var userRole string
err = db.QueryRow("SELECT role FROM users WHERE username = $1", canonicalUsername).Scan(&userRole)
if err != nil {
    log.Printf("query error: %v", err)
    return c.JSON(http.StatusInternalServerError, map[string]string{"error": "unable to load permissions"})
}

// Avoid shell commands with credentials; if needed, use exec.Command with explicit arguments
cmd := exec.Command("/usr/bin/some-tool", "--option", value)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
err = cmd.Run()
if err != nil {
    log.Printf("command failed: %v", err)
}

// Structured error handling to avoid leaking sensitive context
func safeError(err error, c echo.Context) error {
    // Log detailed error internally with structured context, return generic message externally
    if err != nil {
        log.Printf("auth error: %v", err)
        return c.JSON(http.StatusInternalServerError, map[string]string{"error": "request failed"})
    }
    return nil
}