Jeez I swear we'd be this productive all the time of fully funded. Anyway
this makes up for the last one's lameness. -SN
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Nomad Mobile Research Centre
A D V I S O R Y
www.nmrc.org
Simple Nomad [thegnomeat_private]
06Oct1998
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Platform : Netware 4.x
Application : REMOTE.NLM
Severity : Medium
Synopsis
--------
Due to the fact that the Remote Console password encryption scheme uses
a weak "salting", once the encrypted password is recovered from an NCF
file an intruder could decrypt the password.
Tested configuration
--------------------
The testing was done with the following configuration :
Netware 4.11
Service Pack 5
Also confirmed on Netware 4.1
Bug(s) report
-------------
The password for remotely accessing the Netware console is assigned as a
parameter passed to the REMOTE.NLM. Typically this would be stored in the
AUTOEXEC.NCF file as follows:
LOAD REMOTE NMRC
In the above example, the password is NMRC. Although the AUTOEXEC.NCF file
is stored in a protected directory by default, there is concern that any
administrator editing the AUTOEXEC.NCF file via Remote Console might
display the portion of the AUTOEXEC.NCF file with the password (Remote
Console sessions travel over the wire in plaintext). To address this
concern, Novell allows for the creation of an encrypted password.
It is created by typing REMOTE ENCRYPT at the console (assuming you've
already loaded REMOTE.NLM). After being prompted for the password to
encrypt, it is encrypted and displayed on the screen, and you are given
the option to create a file called LDREMOTE.NCF in the SYS:SYSTEM
directory. LDREMOTE.NCF can be called from AUTOEXEC.NCF or the LOAD REMOTE
line in the AUTOEXEC.NCF file can be altered as follows:
LOAD REMOTE NMRC
becomes:
LOAD REMOTE -E 0A1360A501608836FB
So far so good. You now no longer have a plaintext password, and it is
stored in a secure location.
Let's assume the worst - a potential intruder obtains the encrypted
password by sniffing a Remote Console session in which the file containing
the encrypted password is viewed by the administrator, or by using an
exploit (http://geek-girl.com/bugtraq/1997_2/0199.html is an older example
that could be adapted for this purpose, or perhaps using the INTRUDER
tool from Pandora, available from the NMRC web site). Once the intruder
has the encrypted password it can be decrypted, due to the fact that there
is no server-specific salt.
The salt is stored in the last two characters - in the above example the
salt is stored in FB (the actual salt is FF XORed with FB). The salt is
the seconds that have passed since some early date in the past, and yields
a possible 256 salts. Since these are tied to time and not the server
itself, the salt is non-system specific. Decrypting the password does not
require another check of the time - the salt is simply read in and used
during decryption.
A 4 character password called NMRC gets 5 bytes added and this would
become: 0A1360A501608836FB while a password of NMRC.ORG with the 5 bytes
added becomes: F9AEBF1C381855A5FFAA7FAD2D. This implies a symmetric
algorithm with those 5 bytes containing key and salting data. A plaintext
attack will be done at our leisure (mainly for fun), but there is a much
easier way to decrypt it.
To decrypt, the intruder must have console access to any Netware 4.x
server, such as one of the 2 user CD versions you can get in one of those
CNE classes or for $15.00 U.S. (1-800-395-7135, ask for the intraNetWare
2-user eval copy). Once at his/her own home server, the intruder performs
the following steps:
- The REMOTE.NLM is loaded with the -E option followed by the captured
encrypted password.
- Enter Netware's internal debugger by typing the following 4 keys
together: left shift - right shift - alt - esc
- Type in .M and enter, which will list the NLMs loaded along with their
addresses.
- Hit enter until you find the REMOTE.NLM, and write down the data
address.
- Type in D dataaddress and enter.
- 40 bytes (give or take, depending on NLM version) from the address you
typed in will be the unencrypted password, which is viewable as plain text
in the ascii dump area on the righthand side of the screen. Note that any
lower case letters will have been transferred to upper case, since Netware
converted all lower case to upper case during the original password
encryption.
Solution/Workaround
-------------------
Do not use Remote Console. It doesn't encrypt its session anyway, so all
work you do remotely flies across your LAN in plaintext. Novell recommends
not using Remote Console on critical servers, but we recommend not using
it at all. If any server's console is compromised, this can be leveraged
to obtain a copy of NDS and subsequent password hash retrieval for
cracking.
Comments
--------
Novell has been notified, unsure how they plan to handle this. Personally
we recommend not decrypting in RAM, but then the intruder simply uses an
older unpatched version of REMOTE.NLM. Obviously using NDS to store the
password would be prime location, and since Novell makes such a big deal
out of the security of NDS one would think they'd use it to safeguard the
password. Using a protocol scheme similiar to normal login authentication
would also be desired.
This was discovered after hearing a rumor that it could be done. We'd
reveal the rumor source but he's a respectable Fortune 500 type who has
requested anonymity. Besides, a lot of people have asked NMRC for this, so
here it is. For fun, decode this one:
7AB18DEFEFACF8EF58308102100210001698
It should be noted you can also recover the "Lock file server console"
password from the MONITOR.NLM roughly the same way -- it is stored
decrypted in RAM, but in an allocated block of RAM somewhere before the
last lowest NLM data segment. Hint: use the debugger's searching features
on a "test" server to learn approximately where.
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This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 14:18:47 PDT