From thegnome@NMRC.ORG Sat Oct 17 21:26:04 1998 From: Simple Nomad To: BUGTRAQ@netspace.org Date: Tue, 6 Oct 1998 02:36:11 -0500 Subject: NMRC Advisory - "Decryption" of the RCONSOLE Password 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 _______________________________________________________________________________ Nomad Mobile Research Centre A D V I S O R Y www.nmrc.org Simple Nomad [thegnome@nmrc.org] 06Oct1998 _______________________________________________________________________________ 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. _______________________________________________________________________________