=== How to fix it in python-ldap

The following noncompliant code is vulnerable to LDAP injection because untrusted data is
concatenated to an LDAP query without prior sanitization or validation.

==== Noncompliant code example

[source,python,diff-id=1,diff-type=noncompliant]
----
from flask import request
import ldap

@app.route("/user")
def user():
    username =  request.args['username']

    search_filter = "(&(objectClass=user)(uid="+username+"))"

    ldap_connection = ldap.initialize("ldap://localhost:389")
    user = ldap_connection.search_s("dc=example,dc=org", ldap.SCOPE_SUBTREE, search_filter) # Noncompliant

    return user[0]
----

==== Compliant solution

[source,python,diff-id=1,diff-type=compliant]
----
from flask import request
import ldap

@app.route("/user")
def user():
    username = ldap.filter.escape_filter_chars(request.args['username'])

    search_filter = "(&(objectClass=user)(uid="+username+"))"
    
    ldap_connection = ldap.initialize("ldap://localhost:389")
    user = ldap_connection.search_s("dc=example,dc=org", ldap.SCOPE_SUBTREE, search_filter)

    return user[0]
----

=== How does this work?

include::../../common/fix/validation.adoc[]

For Python, the python-ldap library functions
https://www.python-ldap.org/en/python-ldap-3.3.0/reference/ldap-filter.html[`escape_filter_chars`] and
https://www.python-ldap.org/en/python-ldap-3.3.0/reference/ldap-dn.html?highlight=escape_dn#ldap.dn.escape_dn_chars[`escape_dn_chars`] allow sanitizing these characters.

In the compliant solution example, the `escape_filter_chars`
is used to sanitize the search filter concatenated input.