Advisory: Geo++(R) GNCASTER: Faulty implementation of HTTP Digest
Authentication

During a penetration test, RedTeam Pentesting discovered that the
GNCaster software has multiple bugs in its implementation of HTTP Digest
Authentication.

Details

Product: Geo++(R) GNCASTER
Affected Versions: <= 1.4.0.7
Fixed Versions: 1.4.0.8
Vulnerability Type: Various types
Security Risk: low
Vendor URL: http://www.geopp.de
Vendor Status: notified
Advisory URL: http://www.redteam-pentesting.de/advisories/rt-sa-2010-003
Advisory Status: published
CVE: TBA
CVE URL: TBA

Introduction

"Geo++(R) GNCASTER is the Geo++ implementation of a NTRIP caster. NTRIP
is a protocol within RTCM to provide GNSS information via Internet."

(from the vendor's homepage)

More Details

The authentication method required for requesting the path "/admin.htm"
is HTTP Digest. The following flaws were identified during a penetration
test:

a) Even though the server states that HTTP Digest is required for
authentication, a client can use HTTP Basic Authentication successfully.

b) The server software generates the nonce used for HTTP Digest
authentication only once when the server is started. This same nonce is
then used for all authentication until the server is restarted. This
makes the authentication prone to replay attacks. The nonce is the
base64-encoded concatenation of the date and time the server was started
and a 16 byte hex string.

c) The server's response to a failed authentication request contains 32
bytes of data from the service's memory. This data sometimes contains
parts of other users' HTTP requests. Which portion of memory is
disclosed depends on the length of the HTTP request sent. By changing
the length of e.g. any request header, attackers might also retrieve the
authentication headers sent by other users.

Workaround

None

Fix

Update GNCASTER to version 1.4.0.8.

Security Risk

Attackers that can record a user's login communication with the server
can replay this authentication information to gain access to the admin
interface. Attackers might also be able to gather other users'
authentication headers from portions of memory disclosed by the server.
However, the admin interface currently does not seem to offer much
functionality. Therefore the risk of these vulnerabilities is regarded
as low.

History

2009-07-07 Vulnerability identified during a penetration test
2009-07-14 Meeting with customer
2009-12-01 Vendor releases fixed version
2010-01-27 Advisory released

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