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Merge pull request github#5444 from jorgectf/jorgectf/python/ldapimproperauth
Python: Add LDAP Improper Authentication query
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‎python/ql/src/experimental/Security/CWE-287/ImproperLdapAuth.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>If an LDAP query doesn't carry any kind of authentication, anonymous binds causes an empty or None-set password
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to result in a successful authentication.</p>
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</overview>
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<recommendation>
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<p>Use a non-empty password while establishing an LDAP connection.</p>
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</recommendation>
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<example>
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<p>In the following examples, the code builds a LDAP query whose execution carries no authentication or binds anonymously.</p>
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<sample src="examples/auth_bad_2.py" />
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<sample src="examples/auth_bad_3.py" />
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<p>In the third and fourth examples, the authentication is established using a password.</p>
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<sample src="examples/auth_good_2.py" />
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<sample src="examples/auth_good_3.py" />
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</example>
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<references>
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<li>SonarSource: <a href="https://rules.sonarsource.com/python/type/Vulnerability/RSPEC-4433">RSPEC-4433</a>.</li>
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<li>Python2: <a href="https://www.python-ldap.org/en/python-ldap-3.3.0/reference/ldap.html">LDAP Documentation</a>.</li>
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<li>Python3: <a href="https://ldap3.readthedocs.io/en/latest/">LDAP Documentation</a>.</li>
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</references>
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</qhelp>

‎python/ql/src/experimental/Security/CWE-287/ImproperLdapAuth.ql‎

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/**
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* @name Improper LDAP Authentication
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* @description A user-controlled query carries no authentication
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* @kind problem
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* @problem.severity warning
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* @id py/improper-ldap-auth
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* @tags experimental
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* security
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* external/cwe/cwe-287
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*/
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// Determine precision above
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import python
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import experimental.semmle.python.Concepts
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import semmle.python.dataflow.new.DataFlow
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predicate authenticatesImproperly(LDAPBind ldapBind) {
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(
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DataFlow::localFlow(DataFlow::exprNode(any(None noneName)), ldapBind.getPassword()) or
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not exists(ldapBind.getPassword())
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)
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or
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exists(StrConst emptyString |
24+
emptyString.getText() = "" and
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DataFlow::localFlow(DataFlow::exprNode(emptyString), ldapBind.getPassword())
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)
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}
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from LDAPBind ldapBind
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where authenticatesImproperly(ldapBind)
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select ldapBind, "The following LDAP bind operation is executed without authentication"

‎python/ql/src/experimental/Security/CWE-287/examples/auth_bad_2.py‎

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from flask import request, Flask
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import ldap
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import ldap.filter
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import ldap.dn
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6+
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@app.route("/bind_example")
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def bind_example():
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dn = "dc={}".format(ldap.dn.escape_dn_chars(request.args['dc']))
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search_filter = "(user={})".format(ldap.filter.escape_filter_chars(request.args['search']))
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ldap_connection = ldap.initialize("ldap://127.0.0.1:1337")
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ldap_connection.bind('cn=root', "")
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user = ldap_connection.search_s(dn, ldap.SCOPE_SUBTREE, search_filter)

‎python/ql/src/experimental/Security/CWE-287/examples/auth_bad_3.py‎

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from ldap3 import Server, Connection, ALL
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from flask import request, Flask
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from ldap3.utils.dn import escape_rdn
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from ldap3.utils.conv import escape_filter_chars
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@app.route("/passwordNone")
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def passwordNone():
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dn = "dc={}".format(escape_rdn(request.args['dc']))
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search_filter = "(user={})".format(escape_filter_chars(request.args['search']))
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11+
srv = Server('servername', get_info=ALL)
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conn = Connection(srv, user='user_dn', password=None)
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status, result, response, _ = conn.search(dn, search_filter)

‎python/ql/src/experimental/Security/CWE-287/examples/auth_good_2.py‎

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from flask import request, Flask
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import ldap
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import ldap.filter
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import ldap.dn
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6+
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@app.route("/bind_example")
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def bind_example():
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dn = "dc={}".format(ldap.dn.escape_dn_chars(request.args['dc']))
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search_filter = "(user={})".format(ldap.filter.escape_filter_chars(request.args['search']))
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ldap_connection = ldap.initialize("ldap://127.0.0.1:1337")
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ldap_connection.bind('cn=root', "SecurePa$$!")
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user = ldap_connection.search_s(dn, ldap.SCOPE_SUBTREE, search_filter)

‎python/ql/src/experimental/Security/CWE-287/examples/auth_good_3.py‎

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from ldap3 import Server, Connection, ALL
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from flask import request, Flask
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from ldap3.utils.dn import escape_rdn
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from ldap3.utils.conv import escape_filter_chars
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6+
@app.route("/passwordFromEnv")
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def passwordFromEnv():
8+
dn = "dc={}".format(escape_rdn(request.args['dc']))
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search_filter = "(user={})".format(escape_filter_chars(request.args['search']))
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11+
srv = Server('servername', get_info=ALL)
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conn = Connection(srv, user='user_dn',
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password="SecurePa$$!")
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status, result, response, _ = conn.search(dn, search_filter)

‎python/ql/src/experimental/semmle/python/Concepts.qll‎

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@@ -147,6 +147,36 @@ class LDAPEscape extends DataFlow::Node {
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DataFlow::Node getAnInput() { result = range.getAnInput() }
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}
149149

150+
/** Provides classes for modeling LDAP bind-related APIs. */
151+
module LDAPBind {
152+
/**
153+
* A data-flow node that collects methods binding a LDAP connection.
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*
155+
* Extend this class to model new APIs. If you want to refine existing API models,
156+
* extend `LDAPBind` instead.
157+
*/
158+
abstract class Range extends DataFlow::Node {
159+
/**
160+
* Gets the argument containing the binding expression.
161+
*/
162+
abstract DataFlow::Node getPassword();
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}
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}
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/**
167+
* A data-flow node that collects methods binding a LDAP connection.
168+
*
169+
* Extend this class to refine existing API models. If you want to model new APIs,
170+
* extend `LDAPBind::Range` instead.
171+
*/
172+
class LDAPBind extends DataFlow::Node {
173+
LDAPBind::Range range;
174+
175+
LDAPBind() { this = range }
176+
177+
DataFlow::Node getPassword() { result = range.getPassword() }
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}
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150180
/** Provides classes for modeling SQL sanitization libraries. */
151181
module SQLEscape {
152182
/**

‎python/ql/src/experimental/semmle/python/frameworks/LDAP.qll‎

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@@ -19,6 +19,20 @@ private module LDAP {
1919
* See https://www.python-ldap.org/en/python-ldap-3.3.0/index.html
2020
*/
2121
private module LDAP2 {
22+
/** Gets a reference to the `ldap` module. */
23+
API::Node ldap() { result = API::moduleImport("ldap") }
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25+
/** Returns a `ldap` module instance */
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API::Node ldapInitialize() { result = ldap().getMember("initialize") }
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28+
/** Gets a reference to a `ldap` operation. */
29+
private DataFlow::TypeTrackingNode ldapOperation(DataFlow::TypeTracker t) {
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t.start() and
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result.(DataFlow::AttrRead).getObject().getALocalSource() = ldapInitialize().getACall()
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or
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exists(DataFlow::TypeTracker t2 | result = ldapOperation(t2).track(t2, t))
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}
35+
2236
/**
2337
* List of `ldap` methods used to execute a query.
2438
*
@@ -30,32 +44,61 @@ private module LDAP {
3044
}
3145
}
3246

47+
/** Gets a reference to a `ldap` operation. */
48+
private DataFlow::Node ldapOperation() {
49+
ldapOperation(DataFlow::TypeTracker::end()).flowsTo(result)
50+
}
51+
52+
/** Gets a reference to a `ldap` query. */
53+
private DataFlow::Node ldapQuery() {
54+
result = ldapOperation() and
55+
result.(DataFlow::AttrRead).getAttributeName() instanceof LDAP2QueryMethods
56+
}
57+
3358
/**
3459
* A class to find `ldap` methods executing a query.
3560
*
3661
* See `LDAP2QueryMethods`
3762
*/
3863
private class LDAP2Query extends DataFlow::CallCfgNode, LDAPQuery::Range {
39-
DataFlow::Node ldapQuery;
40-
41-
LDAP2Query() {
42-
exists(DataFlow::AttrRead searchMethod |
43-
this.getFunction() = searchMethod and
44-
API::moduleImport("ldap").getMember("initialize").getACall() =
45-
searchMethod.getObject().getALocalSource() and
46-
searchMethod.getAttributeName() instanceof LDAP2QueryMethods and
47-
(
48-
ldapQuery = this.getArg(0)
49-
or
50-
(
51-
ldapQuery = this.getArg(2) or
52-
ldapQuery = this.getArgByName("filterstr")
53-
)
54-
)
55-
)
64+
LDAP2Query() { this.getFunction() = ldapQuery() }
65+
66+
override DataFlow::Node getQuery() {
67+
result in [this.getArg(0), this.getArg(2), this.getArgByName("filterstr")]
68+
}
69+
}
70+
71+
/**
72+
* List of `ldap` methods used for binding.
73+
*
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* See https://www.python-ldap.org/en/python-ldap-3.3.0/reference/ldap.html#functions
75+
*/
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private class LDAP2BindMethods extends string {
77+
LDAP2BindMethods() {
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this in [
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"bind", "bind_s", "simple_bind", "simple_bind_s", "sasl_interactive_bind_s",
80+
"sasl_non_interactive_bind_s", "sasl_external_bind_s", "sasl_gssapi_bind_s"
81+
]
5682
}
83+
}
5784

58-
override DataFlow::Node getQuery() { result = ldapQuery }
85+
/** Gets a reference to a `ldap` bind. */
86+
private DataFlow::Node ldapBind() {
87+
result = ldapOperation() and
88+
result.(DataFlow::AttrRead).getAttributeName() instanceof LDAP2BindMethods
89+
}
90+
91+
/**
92+
* A class to find `ldap` methods binding a connection.
93+
*
94+
* See `LDAP2BindMethods`
95+
*/
96+
private class LDAP2Bind extends DataFlow::CallCfgNode, LDAPBind::Range {
97+
LDAP2Bind() { this.getFunction() = ldapBind() }
98+
99+
override DataFlow::Node getPassword() {
100+
result in [this.getArg(1), this.getArgByName("cred")]
101+
}
59102
}
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61104
/**
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64107
* See https://github.com/python-ldap/python-ldap/blob/7ce471e238cdd9a4dd8d17baccd1c9e05e6f894a/Lib/ldap/dn.py#L17
65108
*/
66109
private class LDAP2EscapeDNCall extends DataFlow::CallCfgNode, LDAPEscape::Range {
67-
LDAP2EscapeDNCall() {
68-
this = API::moduleImport("ldap").getMember("dn").getMember("escape_dn_chars").getACall()
69-
}
110+
LDAP2EscapeDNCall() { this = ldap().getMember("dn").getMember("escape_dn_chars").getACall() }
70111

71112
override DataFlow::Node getAnInput() { result = this.getArg(0) }
72113
}
@@ -78,8 +119,7 @@ private module LDAP {
78119
*/
79120
private class LDAP2EscapeFilterCall extends DataFlow::CallCfgNode, LDAPEscape::Range {
80121
LDAP2EscapeFilterCall() {
81-
this =
82-
API::moduleImport("ldap").getMember("filter").getMember("escape_filter_chars").getACall()
122+
this = ldap().getMember("filter").getMember("escape_filter_chars").getACall()
83123
}
84124

85125
override DataFlow::Node getAnInput() { result = this.getArg(0) }
@@ -92,26 +132,40 @@ private module LDAP {
92132
* See https://pypi.org/project/ldap3/
93133
*/
94134
private module LDAP3 {
135+
/** Gets a reference to the `ldap3` module. */
136+
API::Node ldap3() { result = API::moduleImport("ldap3") }
137+
138+
/** Gets a reference to the `ldap3` `utils` module. */
139+
API::Node ldap3Utils() { result = ldap3().getMember("utils") }
140+
141+
/** Returns a `ldap3` module `Server` instance */
142+
API::Node ldap3Server() { result = ldap3().getMember("Server") }
143+
144+
/** Returns a `ldap3` module `Connection` instance */
145+
API::Node ldap3Connection() { result = ldap3().getMember("Connection") }
146+
95147
/**
96148
* A class to find `ldap3` methods executing a query.
97149
*/
98150
private class LDAP3Query extends DataFlow::CallCfgNode, LDAPQuery::Range {
99-
DataFlow::Node ldapQuery;
100-
101151
LDAP3Query() {
102-
exists(DataFlow::AttrRead searchMethod |
103-
this.getFunction() = searchMethod and
104-
API::moduleImport("ldap3").getMember("Connection").getACall() =
105-
searchMethod.getObject().getALocalSource() and
106-
searchMethod.getAttributeName() = "search" and
107-
(
108-
ldapQuery = this.getArg(0) or
109-
ldapQuery = this.getArg(1)
110-
)
111-
)
152+
this.getFunction().(DataFlow::AttrRead).getObject().getALocalSource() =
153+
ldap3Connection().getACall() and
154+
this.getFunction().(DataFlow::AttrRead).getAttributeName() = "search"
112155
}
113156

114-
override DataFlow::Node getQuery() { result = ldapQuery }
157+
override DataFlow::Node getQuery() { result in [this.getArg(0), this.getArg(1)] }
158+
}
159+
160+
/**
161+
* A class to find `ldap3` methods binding a connection.
162+
*/
163+
class LDAP3Bind extends DataFlow::CallCfgNode, LDAPBind::Range {
164+
LDAP3Bind() { this = ldap3Connection().getACall() }
165+
166+
override DataFlow::Node getPassword() {
167+
result in [this.getArg(2), this.getArgByName("password")]
168+
}
115169
}
116170

117171
/**
@@ -120,14 +174,7 @@ private module LDAP {
120174
* See https://github.com/cannatag/ldap3/blob/4d33166f0869b929f59c6e6825a1b9505eb99967/ldap3/utils/dn.py#L390
121175
*/
122176
private class LDAP3EscapeDNCall extends DataFlow::CallCfgNode, LDAPEscape::Range {
123-
LDAP3EscapeDNCall() {
124-
this =
125-
API::moduleImport("ldap3")
126-
.getMember("utils")
127-
.getMember("dn")
128-
.getMember("escape_rdn")
129-
.getACall()
130-
}
177+
LDAP3EscapeDNCall() { this = ldap3Utils().getMember("dn").getMember("escape_rdn").getACall() }
131178

132179
override DataFlow::Node getAnInput() { result = this.getArg(0) }
133180
}
@@ -139,12 +186,7 @@ private module LDAP {
139186
*/
140187
private class LDAP3EscapeFilterCall extends DataFlow::CallCfgNode, LDAPEscape::Range {
141188
LDAP3EscapeFilterCall() {
142-
this =
143-
API::moduleImport("ldap3")
144-
.getMember("utils")
145-
.getMember("conv")
146-
.getMember("escape_filter_chars")
147-
.getACall()
189+
this = ldap3Utils().getMember("conv").getMember("escape_filter_chars").getACall()
148190
}
149191

150192
override DataFlow::Node getAnInput() { result = this.getArg(0) }

‎python/ql/test/experimental/query-tests/Security/CWE-287/ImproperLdapAuth.expected‎

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| auth_bad_2.py:19:5:19:42 | ControlFlowNode for Attribute() | The following LDAP bind operation is executed without authentication |
2+
| auth_bad_2.py:33:5:33:44 | ControlFlowNode for Attribute() | The following LDAP bind operation is executed without authentication |
3+
| auth_bad_2.py:47:5:47:43 | ControlFlowNode for Attribute() | The following LDAP bind operation is executed without authentication |
4+
| auth_bad_2.py:60:5:60:52 | ControlFlowNode for Attribute() | The following LDAP bind operation is executed without authentication |
5+
| auth_bad_2.py:73:5:73:39 | ControlFlowNode for Attribute() | The following LDAP bind operation is executed without authentication |
6+
| auth_bad_2.py:87:5:87:48 | ControlFlowNode for Attribute() | The following LDAP bind operation is executed without authentication |
7+
| auth_bad_3.py:19:12:19:43 | ControlFlowNode for Connection() | The following LDAP bind operation is executed without authentication |
8+
| auth_bad_3.py:33:12:33:57 | ControlFlowNode for Connection() | The following LDAP bind operation is executed without authentication |
9+
| auth_bad_3.py:46:12:46:55 | ControlFlowNode for Connection() | The following LDAP bind operation is executed without authentication |
10+
| auth_bad_3.py:60:12:60:42 | ControlFlowNode for Connection() | The following LDAP bind operation is executed without authentication |

‎python/ql/test/experimental/query-tests/Security/CWE-287/ImproperLdapAuth.qlref‎

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experimental/Security/CWE-287/ImproperLdapAuth.ql

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