Ldap Injection in Django with Mongodb

Ldap Injection occurs when untrusted input is concatenated into LDAP queries without proper escaping, allowing an attacker to manipulate the query structure. In Django, this typically surfaces in authentication backends or user-management code that builds LDAP filter strings using Python string formatting. When the same application also uses Mongodb as a secondary data store—such as caching user sessions, storing audit logs, or persisting profile data—the unsafe LDAP query can indirectly affect Mongodb operations if the attacker-controlled data is later written to or read from Mongodb.

Consider a Django view that takes a username from a request and builds an LDAP filter using Python string interpolation:

username = request.GET.get('username', '')
ldap_filter = f'(uid={username})'  # vulnerable

An attacker can supply (uid=admin)(objectClass=*) as the username, changing the effective filter to (&(uid=admin)(objectClass=*)) or breaking out of intended scope to enumerate users. Because Django may later store the raw username or the resulting session identifiers in Mongodb—e.g., for analytics or tracking—malicious payloads can be persisted and reused in other contexts, such as log injection or secondary injection attacks against Mongodb.

Mongodb-specific risks arise when the same untrusted input is used to build queries against the database. For example, if the application constructs a Mongodb filter using unsanitized LDAP input without validation or parameterization, attackers can attempt NoSQL injection to bypass authentication or extract data:

doc = {'user': username, 'action': 'login'}  # username from LDAP input
collection.insert_one(doc)  # risk if username contains $where or $ne-like operators

Although Mongodb’s query language is distinct from LDAP, the pathway is clear: unescaped LDAP input reaching Mongodb queries can enable injection, especially when input is treated as executable rather than data. This is compounded if the application uses dynamic field names or eval-like operators. The combination of Django, LDAP, and Mongodb increases the attack surface because trust boundaries blur between authentication and persistence layers.

To mitigate, treat LDAP input as untrusted data, apply strict allow-listing, and use framework-provided parameterization for both LDAP and Mongodb. Avoid building queries by string concatenation in either context, and validate input against expected patterns before any storage or further processing.

Remediation focuses on preventing injection at both the LDAP and Mongodb layers. For LDAP, use parameterized filters instead of string interpolation. For Mongodb, use structured query objects and avoid operators derived from user input. Below are concrete, safe patterns.

Safe LDAP query construction

Use ldap.filter.escape_filter_chars to escape special characters in user input before building the filter:

from ldap.filter import escape_filter_chars

username = request.GET.get('username', '')
escaped_username = escape_filter_chars(username)
ldap_filter = f'(uid={escaped_username})'  # safe

Safe Mongodb operations in Django

Use PyMongo or an ODM like MongoEngine with parameterized queries. Do not embed raw input into query keys or values.

Example with PyMongo:

from pymongo import MongoClient
from ldap.filter import escape_filter_chars

client = MongoClient('mongodb://localhost:27017/')
db = client['audit']
collection = db['logins']

username = request.GET.get('username', '')
escaped_username = escape_filter_chars(username)
# Safe: use a dict with a literal key and escaped value
record = {'user': escaped_username, 'action': 'login'}
collection.insert_one(record)

Example with MongoEngine (if used):

from mongoengine import connect, Document, StringField
connect('mydb')

class LoginLog(Document):
    user = StringField(required=True)
    action = StringField(default='login')

username = request.GET.get('username', '')
escaped_username = escape_filter_chars(username)
safe_log = LoginLog(user=escaped_username, action='login')
safe_log.save()  # MongoEngine handles safe encoding

Additional hardening

• Apply allow-listing for usernames (e.g., alphanumeric and limited special characters) before using them in LDAP or Mongodb.
• Validate length and format early in the Django form or serializer to reject unexpected patterns.
• Avoid passing raw LDAP input to Mongodb operators such as $where or $eval; if dynamic querying is required, use predefined, parameterized query templates.
• Log rejected inputs for audit without echoing raw attacker data back into responses or databases.