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Pacom 1000 CCU Crypto Shortcomings

Pacom 1000 CCU Crypto Shortcomings
Posted Dec 11, 2015
Authored by Peter Norin, Fredrik Soderblom, Joachim Strombergson

Pacom 1000 CCU suffers from a multiple cryptography implementation vulnerabilities.

tags | advisory, vulnerability
advisories | CVE-2014-3260
SHA-256 | 8ffb6582450cc66bf6ede0f129ed03b875df1b0ccd435a123b1858fbdab968f4

Pacom 1000 CCU Crypto Shortcomings

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XPD - XPD Advisory
https://xpd.se

Crypto implementation flaws in Pacom GMS System

Advisory ID: XPD-2015-001
CVE reference: CVE-2014-3260
Affected platforms: Pacom 1000 CCU ("Base Station") and Controllers
(RTU)
Version: All versions are affected
Date: 2013-Oktober-10
Security risk: High
Vulnerability: Crypto implementation flaws in Pacom GMS System
Researcher: Joachim Strombergson, Fredrik Soderblom, Peter Norin
Vendor Status: Notified / Patch available
Vulnerability Disclosure Policy:
https://xpd.se/advisories/xpd-disclosure-policy-01.txt
Permanent URL:
https://xpd.se/advisories/XPD-2015-001.txt

=====================================================================

Summary:

The Pacom 1000 CCU and controllers (RTU) is used in security alarm
installations all over the world. The flaws we have found can bypass
the security of any unpatched installation.

"The purpose of a Pacom Controller is to control, monitor, and maintain
security for a remote site. It is located at the site itself and
performs
all alarm and door control functions."
- http://www.pacom.com/field-controllers.php

"Pacom security solutions are installed in over twenty countries on
seven
continents." - http://www.pacom.com/our-customers.php

Detailed description:

The Pacom 1000 implementation have several serious implementation flaws.

These vulnerabilities could in a worst case scenario lead to a full
compromise of the protocol between the controller and the base station,
rendering an alarm system useless.

Potentially a large number of sites could be affected by the described
flaws.

PRNG:

The PRNG used is of a type known as a Linear Congruential Generator.
This type of generator are known to provide random numbers with less
than perfect uniform distribution. The PRNG is a 16-bit generator.
This means that the generator can only generate 2**16 numbers in a
sequence before it must be reseeded. There is no information about
how the generator is seeded from start nor how it is reseeded.

A simulation in Dieharder shows that the used algorithm fails every
test except for one, where it receives the result 'Weak'.

The Linear Congruential Generator can be broken by observing values
generated by consecutive iterations of the PRNG. The system creates
32-bit random numbers by extracting 8-bits from four consecutive
16-bit words numbers generated by the PRNG. This means that by
observing a single 32-bit word, an attacker has in fact half the state
information (8 out of 16 bits) from four iterations of the generator.

MAC:

A Message Authentication Code (MAC) is generated and added to each
message sent between CCU and Controller. The MAC generator generator
used is not based on any well-known secure MAC functionality such as
HMAC or OMAC. Furthermore the generated MAC is only 32 bit.

Master Code:

There is a functionality for substitution detection. According to
Pacom the functionality is based on a proprietary Pacom encryption
method. Key to the functionality is a a 24-bit randomly generated
value called Master Code. The Master Code is also used to generate
the 128-bit AES key used with the substitution detection algorithm.
Hence the effective strength of the key is not 128 bits, nor 104 bits
(128 - 24) but 24 bits. A very short key with low security.

Unfortunately it appears that the aforementioned (16 bit only),
less than optimal, PRNG is used to generate the Master Code, thus
reducing it's effective strength to 16 bit.

The Master Code is distributed from CCU to CPU-cards and other CCUs
as well as GMS units (for logging purposes) in clear text. This means
that the code potentially is sent unprotected over private networks,
corporate networks, public networks etc.

Substitution detection:

According to Pacom documentation the "substitution detection involves
appending a 128-bit check code to the controller heartbeat response
messages. The check code is calculated from a combination of a
hard-coded constant value, the controllers master code, and the
message data. In essence it is another type of MAC, but one that
employs the master code."

The implementation of the substitution detection uses a "check code"
which is said to be 128-bits long and is appended to response messages.
However due to a design flaw, the code is only 64 bit.

In total the heartbeat response message is 5 bytes (40 bits) long:

Byte 1: The message type (e.g. heartbeat response)
Byte 2: A value based on random numbers sent in the heartbeat command
from the CCU
Byte 3: The controller summary status
Byte 4: The heartbeat sequence number (zero or one)
Byte 5: Always zero

Of the five bytes in the heartbeat response message, two bytes (4 and 5)
are either one or zero, or always zero. Byte 3 is a simple status. So,
of 40 bits, 32 bits are most likely predictable and the remaining 8
bits
is probably choosen based on the weak PRNG. This means that a big part
of the response message can be guessed.

The so called "128-bit check code" is then calculated over these 5 bytes
using the aforementioned flawed Master Code and a 2 byte address of the
controller, forming a 40 bit key, which is used with a hard coded
constant
to form an AES-128 key.

The resulting "128-bit check code" from the AES encryption is XOR:ed
with
its own cleartext. This means that there is a direct path from
cleartext to
ciphertext bypassing the AES encryption. This leaks information about
the cleartext as well as opening up for chosen plaintext attacks.

Hard coded constants:

The security functionality uses several hard coded, secret constants for
random number generation, MAC calculation, Substitution detection
algorithm etc. Unfortunately, the way these constants are used,
information about them are leaked through the very messages, which
opens up for recovery of the constants. If the constants are recovered
and thus system security is lost, the units must be reprogrammed in
the field or even replaced.

=====================================================================
Conclusion:

We do not recommend relying on the security features in the system and
the system should be viewed as an unprotected system.

If the system is to be used, separate communication security mechanism
should be added.

However, the usage of hard coded constants in the units and the
associated
need for field service or replacement if a breach occurs, makes us
recommend that the system needs severe redesign before it is ready for
production use.

We questions if the system has been designed with any knowledge of what
has been known good security practices since at least 30 years, nor
good
engineering practice.

=====================================================================
Versions affected:

All versions of Pacom 1000 (CCU & RTU) - According to Pacom, this
firmware
will not be fixed. Customers are advised to switch to the EMCS
platform instead.

All versions of EMCS (Pacom .is) prior to 1.3

The vendor reports that the following versions are patched:
EMCS (Pacom .is) version 1.3 and above

=====================================================================
Credits

This vulnerability was discovered and researched by Joachim Strombergson
from Assured AB, Fredrik Soderblom and Peter Norin from XPD AB.

=====================================================================
References

https://en.wikipedia.org/wiki/Linear_congruential_generator
https://en.wikipedia.org/wiki/Diehard_tests

=====================================================================
History

2013-10-10 Initial Discovery
2013-10-22 Initial attempt to contact the vendor
2013-11-12 Reply from Niscayah, case is assigned to internal resource
2014-05-07 CVE-2014-3260 is assigned
2014-06-05 Draft of the advisory sent to the vendor
2014-09-01 Pacom notifies us that fixed firmware (EMCS only) is ready
2015-12-08 Public disclosure

=====================================================================
About Assured

Assured AB is a privately held company with headquarters in Gothenburg,
Sweden. Established in 2015, Assured is an independant security
consultancy firm that provides expert knowledge, advisory and
design of IT- security solutions.

http://assured.se

About XPD

XPD AB is a privately held company with Headquarters in Stockholm,
Sweden.
Established in 2002, XPD AB is an independent security consulting and
research firm, with a focus on security and perimeter security
solutions.

https://xpd.se

=====================================================================
Disclaimer and Copyright

Copyright (c)2015 XPD AB and Assured AB. All rights reserved.
This advisory may be distributed as long as its distribution is
free-of-charge and proper credit is given.

The information provided in this advisory is provided "as is" without
warranty of any kind. XPD AB and Assured AB disclaims all warranties,
either express or implied, including the warranties of merchantability
and
fitness for a particular purpose. In no event shall XPD AB or Assured
AB,
or its suppliers be liable for any damages whatsoever including direct,
indirect, incidental, consequential, loss of business profits or
special damages, even if XPD AB or Assured AB, or its suppliers have
been
advised of the possibility of such damages.

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