Ldap Injection in Buffalo with Firestore

Ldap Injection occurs when untrusted input is concatenated into an LDAP query without validation or escaping, allowing an attacker to manipulate the query structure. In the Buffalo web framework, this typically arises when building LDAP search filters in Go code using string concatenation or fmt.Sprintf. Firestore, as a backend data store, may hold user records that include LDAP-related configuration or mapped attributes (such as uid, mail, or group memberships). When Buffalo reads from Firestore to construct LDAP queries, if the data from Firestore or from client request parameters is not properly sanitized, an attacker can inject LDAP metacharacters such as * (wildcard), & (AND), | (OR), ! (NOT), and parentheses to alter the query logic.

For example, suppose Firestore contains a mapping of usernames to base DNs, and Buffalo retrieves this mapping to build a search request. If the username is taken directly from user input and used in a filter like (&(uid=%s)(objectClass=person)), an attacker could supply admin*)( as the uid, resulting in the filter (&(uid=admin*)( as)(objectClass=person)), which can bypass authentication or enumerate entries. This becomes a security risk when the constructed LDAP query is executed against an upstream LDAP server. The exposure is not in Firestore itself, which is a NoSQL database, but in the way Buffalo uses Firestore-derived or user-supplied data to form LDAP filters. Without input validation, encoding, or parameterized filter construction, the unauthenticated attack surface includes authentication bypass and potential information disclosure through LDAP error messages or data returned by the directory.

middleBrick detects this class of issue under the BOLA/IDOR and Input Validation checks, highlighting how untrusted data flows from storage or request into directory operations. The scanner does not assume a particular backend; it flags places where user-influenced data reaches LDAP query construction. Remediation centers on strict input validation, using parameterized filters or prepared search templates, and ensuring Firestore-stored configuration values are treated as untrusted. Developers should avoid concatenating strings to build LDAP filters and instead use libraries that support proper escaping. Additionally, applying principle of least privilege to the LDAP service account and monitoring for unusual query patterns reduces impact even if injection vectors exist.

To remediate Ldap Injection in Buffalo when Firestore is involved, treat all data used in LDAP query construction as untrusted, regardless of its source. Use parameterized approaches and avoid string interpolation. Below are concrete Go examples for Buffalo that demonstrate safe handling when integrating with Firestore. These examples assume you retrieve configuration or user mapping from Firestore and then build an LDAP filter.

First, define a struct to represent the Firestore-stored mapping and use the Firestore client to fetch values safely:

import (
    "context"
    firestore "cloud.google.com/go/firestore"
    "github.com/gobuffalo/buffalo"
)

type LDAPMapping struct {
    UID        string `"uid"`
    BaseDN     string `"base_dn"`
    Email      string `"email"`
}

func getMapping(ctx context.Context, client *firestore.Client, key string) (*LDAPMapping, error) {
    doc, err := client.Collection("ldap_mappings").Doc(key).Get(ctx)
    if err != nil {
        return nil, err
    }
    var m LDAPMapping
    if err := doc.DataTo(&m); err != nil {
        return nil, err
    }
    return &m, nil
}

Next, build the LDAP filter using proper escaping rather than concatenation. Use a dedicated LDAP filter encoder or manually escape special characters. Here is an example using manual escaping for common metacharacters:

import (
    "strings"
)

func escapeLDAPFilter(value string) string {
    // Basic escaping for RFC 4515: replace * with \2a, ( with \28, ) with \29, \ with \5c, etc.
    value = strings.ReplaceAll(value, "\", "\\5c")
    value = strings.ReplaceAll(value, "*", "\2a")
    value = strings.ReplaceAll(value, "(", "\28")
    value = strings.ReplaceAll(value, ")", "\29")
    value = strings.ReplaceAll(value, "\000", "\000")
    return value
}

func buildSafeFilter(uid string) string {
    safeUID := escapeLDAPFilter(uid)
    return "(&(uid=" + safeUID + ")(objectClass=person))"
}

In a Buffalo handler, you would fetch the mapping, escape incoming identifiers, and construct the filter safely:

func AuthHandler(c buffalo.Context) error {
    ctx := c.Request().Context()
    client := // initialized Firestore client
    rawUID := c.Param("username")
    mapping, err := getMapping(ctx, client, rawUID)
    if err != nil {
        return c.Render(401, r.JSON(map[string]string{"error": "invalid"}))
    }
    filter := buildSafeFilter(mapping.UID)
    // Use filter with your LDAP client; do not directly interpolate rawUID
    _ = filter
    return c.Render(200, r.JSON(map[string]string{"status": "ok"}))
}

These examples emphasize that the data pulled from Firestore should not be trusted and must be escaped before inclusion in LDAP filters. For higher assurance, prefer an LDAP library that provides a filter builder with automatic escaping. In addition, apply least-privilege service accounts for Firestore and LDAP, and validate that returned mappings are within expected formats using strict schema checks. middleBrick’s scans can verify that no concatenated LDAP filter patterns exist and that input validation is present, giving you prioritized remediation guidance.