Ldap Injection in Buffalo with Basic Auth

LDAP Injection is a web security concern that arises when an application passes unsanitized user input into LDAP queries. In the Buffalo web framework for Go, this typically occurs when constructing LDAP filter strings using parameters from HTTP requests, such as username or password fields. When Basic Authentication is used, the Authorization header is often parsed and its credentials are forwarded to an LDAP server for verification. If the application directly interpolates the provided username or password into an LDAP search filter without escaping special characters, an attacker can manipulate the filter syntax to bypass authentication or extract data.

For example, a developer might build an LDAP filter like (&(uid=USER)(password=PASS)), where USER and PASS are taken directly from the request. An attacker supplying a username of admin)(uid=*) could alter the filter to (&(uid=admin)(uid=*)(password=PASS)), potentially returning all entries and enabling unauthorized access. This occurs because Basic Auth transmits credentials in a base64-encoded header that, if decoded and used in an LDAP query without sanitization, exposes the injection surface.

Buffalo does not inherently sanitize inputs used in LDAP construction; it relies on the developer to handle escaping. The framework’s middleware for parsing Basic Auth headers can inadvertently pass raw values to LDAP libraries. Attack patterns relevant here include CVE-adjacent techniques such as filter injection (CWE-90) and authentication bypass, which map to the OWASP API Top 10 category of Broken Authentication. Because LDAP servers often permit complex filter expressions, unsanitized input can lead to privilege escalation or data exposure. middleBrick’s checks for Authentication and Input Validation would flag such issues by correlating runtime behavior with spec definitions, highlighting missing escaping in OpenAPI operations that involve security schemes of type basic.

To remediate LDAP Injection in Buffalo when using Basic Auth, ensure that any user-controlled values used in LDAP filters are properly escaped. Use Go’s golang.org/x/exp/ldap package (or equivalent) to construct filters programmatically, or apply strict escaping to special characters such as *, (, ), and \. Avoid string concatenation for building filters; prefer parameterized approaches that separate filter structure from data.

Below are concrete code examples for safely handling Basic Auth in Buffalo.

Example 1: Parsing Basic Auth safely

package actions

import (
	"encoding/base64"
	"strings"
)

// parseBasicAuth extracts username and password from the Authorization header.
// It returns empty strings if the header is missing or malformed.
func parseBasicAuth(header string) (username, password string) {
	if header == "" || !strings.HasPrefix(header, "Basic ") {
		return "", ""
	}
	payload, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(header, "Basic "))
	if err != nil {
		return "", ""
	}
	parts := strings.SplitN(string(payload), ":", 2)
	if len(parts) != 2 {
		return "", ""
	}
	return parts[0], parts[1]
}

Example 2: Building an escaped LDAP filter

package ldaputil

import (
	"github.com/golang/ldap/ldap"
)

// BuildAuthFilter creates an LDAP AND filter with escaped values.
// It ensures that username and password are safely incorporated.
func BuildAuthFilter(username, password string) string {
	escapedUser := ldap.EscapeFilter(username)
	escapedPass := ldap.EscapeFilter(password)
	return ldap.FormatFilter("(&(uid=%s)(userPassword=%s))", escapedUser, escapedPass)
}

In your Buffalo login action, you would call parseBasicAuth to obtain credentials, then pass them to before performing the LDAP bind. This approach prevents injection by neutralizing metacharacters and keeping the filter structure intact. middleBrick’s scans will validate that inputs are properly sanitized and that authentication mechanisms align with the declared security scheme, reducing risk across the Authentication and Input Validation checks.