Ldap Injection in Echo Go with Basic Auth

Ldap Injection occurs when an attacker can manipulate LDAP query construction, typically by injecting special characters into inputs that are used to build LDAP filters. In Go services using the Echo framework with HTTP Basic Authentication, this risk arises when the username provided in the Authorization header is passed directly into an LDAP search or bind without sanitization or parameterization. Basic Auth sends credentials as base64-encoded, not encrypted, and if the service decodes the username and uses it in an LDAP query, characters such as asterisks (*), parentheses, backslashes, or null bytes can alter the filter logic.

Consider an Echo handler that retrieves the username via basicAuth := req.Header.Get("Authorization") and then parses it. If the extracted username is concatenated into an LDAP filter like (&(objectClass=person)(uid(username))), an attacker supplying username as admin)(uid=*)(objectClass=*) can change the filter semantics, potentially bypassing authentication or extracting unintended directory data. Because Echo does not inherently sanitize inputs, the developer must treat the Basic Auth username as untrusted. The LDAP client library itself does not protect against injection; it reflects whatever string is provided. If the service performs an anonymous or low-privilege bind using the injected filter, the attack surface expands: attackers can probe directory attributes, trigger excessive resource consumption, or cause errors that leak stack traces or server information. Because the scan category Unauthenticated LLM endpoint detection is not relevant here, the concern is purely in how the application handles the decoded credentials before issuing the LDAP search.

In a black-box context, middleBrick tests such a flow by submitting a URL that triggers the authentication path and observing whether crafted Basic Auth credentials produce anomalous behavior, such as different HTTP status codes or response patterns that indicate filter manipulation. The 12 security checks run in parallel, and findings related to BOLA/IDOR, Input Validation, and Authentication are particularly relevant. A finding would highlight that user-controlled data from Basic Auth is reflected in LDAP query construction without escaping, encoding, or use of parameterized filters, and would map to OWASP API Top 10 #1 Broken Object Level Authorization and #5 Injection. The report includes remediation guidance rather than attempting to block or fix the endpoint automatically.

Remediation centers on never directly interpolating the Basic Auth username into LDAP filters. Instead, treat the decoded username as an opaque identifier, validate it against a strict pattern, and use parameterized or escaped constructs when interacting with LDAP. Below are two concrete approaches in Echo Go.

Approach 1: Reject non-safe usernames with strict validation

Define a validation function that permits only alphanumeric characters and a limited safe set. If the username does not match, reject the request before any LDAP interaction.

package main

import (
	"net/http"
	"regexp"

	"github.com/labstack/echo/v4"
)

var safeUsername = regexp.MustCompile(`^[a-zA-Z0-9._-]{1,64}$`)

func handleLogin(c echo.Context) error {
	// Extract Basic Auth
	username, password, ok := c.Request().BasicAuth()
	if !ok {
		return echo.NewHTTPError(http.StatusUnauthorized, "missing basic auth")
	}
	// Validate username strictly
	if !safeUsername.MatchString(username) {
		return echo.NewHTTPError(http.StatusBadRequest, "invalid username format")
	}
	// At this point, do NOT directly concatenate username into LDAP filter.
	// Use a parameterized bind or a safe search with proper escaping.
	// Placeholder for LDAP logic using username as a bound identity, not a filter component.
	return c.String(http.StatusOK, "auth validated")
}

func main() {
	e := echo.New()
	e.POST("/login", handleLogin)
	e.Start(":8080")
}

This approach ensures that characters which could manipulate LDAP syntax are rejected early, reducing the need for complex escaping and lowering the risk of injection.

Approach 2: Use ldap.Filter with proper escaping when constructing filters

If your workflow requires building a filter with the username as an attribute value, use a library that provides escaping for LDAP special characters. For example, with the go-ldap/ldap/v3 library, construct filters programmatically rather than via string concatenation.

package main

import (
	"net/http"

	"github.com/labstack/echo/v4"
	ldap "github.com/go-ldap/ldap/v3"
)

func handleLoginEscaped(c echo.Context) error {
	username, password, ok := c.Request().BasicAuth()
	if !ok {
		return echo.NewHTTPError(http.StatusUnauthorized, "missing basic auth")
	}
	// Build filter safely: username is used as the value of uid, not as part of the filter structure.
	filter := ldap.NewFilter()
	filter.And().
		Equal("objectClass", "person").
		Equal("uid", username)
	// Use filter.String() only if the library internally escapes; prefer parameterized binds.
	// Example bind (not executed here) using the username as the RDN or for binding:
	// l.Bind("uid=" + ldap.EscapeFilter(username) + ",ou=people,dc=example,dc=com", password)
	// For this example, we validate and then rely on a separate identity binding step.
	return c.String(http.StatusOK, "auth validated with escaped filter logic")
}

func main() {
	e := echo.New()
	e.POST("/login", handleLoginEscaped)
	e.Start(":8080")
}

Key points: avoid string concatenation for filters, use the library’s filter builder or escaping functions, and prefer binding with escaped DNs over injecting into search filters. These changes align with input validation and Authentication checks in middleBrick’s scan categories and help ensure that Basic Auth credentials do not become an injection vector.