                  . o O o . I N S I D E   N D S . o O o .

                              by Simple Nomad


                     . o O o . [ Abstract ] . o O o .

This document will present a technical view of the layout of Novell's Netware 
Directory Services (NDS). The emphasis here is mainly from a security 
perspective, and tries to point out several areas of weakness that need to be
reinforced. Novell has touted the advanced security features built into NDS 
as being superior to other network operating systems, including statements 
that passwords cannot be recovered, even by administrators. This document
will examine how to recover the passwords, and give a complete layout of NDS.


                     . o O o . [ Audience ] . o O o .

While I am probably more well known for the Netware Hack FAQ and presentation 
of security issues related to Netware from an intruder perspective, this 
document is geared more toward those simply interested in how things work. 
But due to the fact that I am covering security issues, the inference is still
there.

I do assume some basic Netware knowledge, and I make use of some examples of C
code to explain some concepts, therefore knowledge of C coding might be of 
some help. I have tried to make this as non-technical as possible, but due to
the material being covered, unless you are a bit head this is probably going
to be a very dry read.


                      . o O o . [ Credits ] . o O o .

If you read nothing, or just a paragraph or two, please at least read these
credits. I did have some support during this project, and I want to acknowledge
a few people. For some background help and some code snippets, itsme provided a
lot. Also I bounced ideas off of Greg Miller, Al Grant, and Rx2. Thanks a lot.

Lab assistance was provided by Mr. Wizard and Fourth Stooge. Mr. Wizard
provided several examples of BACKUP.DS so I had multiple copies to play with,
and Fourth Stooge provided hardware in the form of hard drives for the lab.
Without the drive space I would have been very limited, and without the
extra BACKUP.DS files I would not have been able to accurately cross check
the different 4.x Netware versions for consistancy.

Finally I would like to thank two more people, my wife for naming the project
Pandora after hearing my explanation of what the hell I was doing in the lab
for hours at a time, and Marcus Williamson for trying to keep me honest through
a series of email exchanges where he constantly tried to get me to admit that
this was NOT a security breach (that is left for you, the humble reader, to
decide).


                      . o O o . [ Tools ] . o O o .

There were a number of tools used in the preparation of this document. The two
main tools were a hex dump utility and a hex calculator. By examining the NDS 
files in the hex dump utility and playing with some of the values, a picture 
of how the files were tied together emerged. I also used a C compiler and 
wrote several utilities to extract and examine the data. Most of the utilities
were short programs of little use to the general public, but as I continued to
explore I wrote more useful utilities for NDS extraction. These utilities, 
along with a copy of this document were released as a set called Pandora. 
Pandora is available from http://www.nmrc.org/files/netware, or from a link 
on the Pandora Home Page at http://www.nmrc.org/pandora.


                    . o O o . [ Background ] . o O o .

NDS is a distributed database for Netware 4.x that provides access to all 
network resources. It allows a user to use a single login to a Netware 
environment and approach a group of Netware servers as a single entity. GUI 
interfaces provide easy management for administrators.

NDS itself consists of 4 core files. These files include PARTITIO.NDS, 
ENTRY.NDS, VALUE.NDS, and BLOCK.NDS. The files are stored on the SYS: volume 
in a hidden directory called _NETWARE. This directory cannot be directly 
accessed from a user login session, including an administrator.

All objects addressed by the server are located within the ENTRY.NDS file.
All named attributes have a record, and all administrator-created items
have a record. For example, there is a record called USER which contains
information about the USER property itself, and a record for a user called
Admin which contains information about that particular USER object.

Values associated with ENTRY records are stored in one and sometimes two
files. VALUE.NDS will contain up to 16 bytes of data about an ENTRY record.
Why so little? Well, 16 bytes is EXACTLY what is needed for one ACL entry.
ACL entries are the most common VALUE records. If more than 16 bytes of
information is needed, the VALUE record has a pointer to BLOCK.NDS. This
file's records can contain up to 120 bytes of data. If still more room is
needed, extra BLOCK records can be linked together via pointers.

The partition information is contained within PARTITIO.NDS, which is
basically used to keep track of a minimal amount of information that helps
NDS replicate and sync up the data between servers.


                   . o O o . [ Accessing NDS ] . o O o .

First off, to explore NDS one must retrieve a copy from a server. This is 
actually easier than it seems. The two main ways to get copies of NDS involve 
console access, and will interrupt server access during retrieval. If you are 
pulling a copy of NDS off of a server, make sure you wait until a time when 
user activity is at a minimal. The interruption will mean that access to 
network resources that have not been authenticated will not work. If users 
are already logged in, they should not notice any interruptions. This is 
similiar to the impact encountered during a DSREPAIR.

The first method involves using either RCONSOLE or direct console access and 
loading an NLM that allows access to SYS:_NETWARE to retrieve the copies. Two 
such NLMs are JCMD.NLM and NETBASIC.NLM. JCMD.NLM is freeware available on 
the Internet, but NETBASIC.NLM is the prefered method, as this NLM is bundled 
with Netware 4.11. Loading NETBASIC and typing "shell" drops you to a pseudo 
DOS-like environment. From here you can simply cd into SYS:_NETWARE, and copy 
the *.NDS files to another location on the server (for example SYS:LOGIN). 
Remember, DS.NLM must be unloaded to do this.

For the faint of heart, there is one other method using DSMAINT.NLM, or 
NDSCOPY.NLM that came with an older version of DSMAINT.NLM. These are 
available from Novell's web site. The by-product of running these NLMs is a 
file called BACKUP.DS that is placed in the SYS:SYSTEM directory. This is my 
prefered method of retrieval, and you get all of the NDS files in one package.

It should be obvious, but if your server console is compromised, an intruder 
could do this as well. And if the file system is compromised, BACKUP.DS will 
be a tempting target. So keep BACKUP.DS in a safe place if you wish to protect 
NDS, and if no longer needed, delete it.


                 . o O o . [ NDS File Structure ] . o O o .

The 4 files -- ENTRY.NDS, VALUE.NDS, BLOCK.NDS, and PARTITIO.NDS -- are binary 
files that consist of individual records. Here is the structure (as well as I 
can determine without the source code) for each record. Included are my 
comments:

typedef unsigned long uint32;
typedef unsigned int  uint16;
typedef unsigned char uint8;

/*
 * struct for ENTRY.NDS records
 */
typedef struct entry
{
	uint32          selfOffset;    /* Offset in ENTRY.NDS. If this is
					  the first record, it is 0x00000000
					  followed by 0x0000014e for the
					  second record, etc. */
	uint32          checkSum;      /* I assume a checksum */
	uint32          val1;          /* Unsure, 0xfeffffff. */
	uint32          val2;          /* Unsure, 0xffffffff. */
	uint32          peer;          /* Offset to a peer record. */
	uint32          firstChild;    /* Offset to first child record. If
					  no kids, 0xffffffff. */
	uint32          lastChild;     /* Offset to second child record. If
					  no kids, 0xffffffff. */
	uint32          firstValue;    /* Offset in VALUE.NDS of first
					  attribute. They are usually kept
					  in order in VALUE.NDS, but since
					  they are crossed referenced in
					  VALUE.NDS they don't have to be.*/
	uint32          id;            /* The Object ID of the record. */

	uint32          partitionID;   /* The partition ID of the record. */
	uint32          parentID;      /* The parent's Object ID, if no
					  parent it is 0xffffffff. */
	uint32          val3;          /* No idea. Usually a small number.*/
	uint32          val4;          /* No idea. 0x00000000. */
	uint32          subordinates;  /* Number of subordinates. This can
					  include other objects besides
					  children. */
	uint32          classID;       /* The "type" of Object ID. */
	uint32		creatTime1,    /* When object was created. */
			creatTime2;
	uint32		modTime1,      /* When object was last modified. */
			modTime2;
	uint8           name[258];     /* Dreaded unicode describing
					  the record. If a user object
					  it will be the common name. */
} ENTRY; /* size=334 */

/*
 * struct for VALUE.NDS records
 */
typedef struct value
{
	uint32          selfOffset;    /* Offset in VALUE.NDS. If this is
					  the first record, it is 0x00000000
					  followed by 0x00000040 for the
					  second record, etc. */
	uint32          checkSum;      /* I assume a checksum */
	uint32          val1;          /* Unsure, usually 0xfeffffff. */
	uint32          val2;          /* Unsure, usually 0xffffffff. */
	uint32          nextVal;       /* The next Value record's offset. */
	uint32          firstBlock;    /* Offset in BLOCK.NDS if used. */
	uint32          entryID;       /* Type of record in ENTRY.NDS. */
	uint32          typeID;        /* Type of VALUE record. */
	uint32          val3;          /* No idea. Usually a small number.*/
	uint32          creatTime1,    /* When object was created(?), */
			creatTime2;    /*  and modified(?). */
	uint32          length;        /* Length of data. */
	uint8           data[16];      /* Start of data, unless there is a
					  small amount of data, then it's
					  all here. */
} VALUE; /* size=64  */

/*
 * struct for BLOCK.NDS records
 */
typedef struct block
{
	uint32          selfOffset;    /* Offset in BLOCK.NDS. If this is
					  the first record, it is 0x00000000
					  followed by 0x00000080 for the
					  second record, etc. */
	uint32          checkSum;      /* I assume a checksum */
	uint32          val1;          /* Unsure. */
	uint32          nextBlock;     /* Next record if data>120. */
	uint32          valueOffset;   /* Offset in VALUE.NDS (backlink) */
	uint8           data[120];
} BLOCK; /* size=128 */

/*
 * struct for PARTITIO.NDS records
 */
typedef struct partition
{
	uint32          selfOffset;    /* Offset in PARTITIO.NDS. If this is
					  the first record, it is 0x00000000
					  followed by 0x00000028 for the
					  second record, etc. */
	uint32          checkSum;      /* I assume a checksum */
	uint32          val1;          /* Unsure. */
	uint32          id;            /* ID of record. */
	uint32          entryID;       /* ID in ENTRY.NDS */
	uint32          replicaID;     /* Replica ID (??) in ENTRY.NDS */
	uint32          val2;          /* Unsure. */
	uint32          val3;          /* Unsure. */
	uint32          timeStamp1,    /* Probably used to keep things in sync */
			timeStamp2;
} PARTITIO; /* size=40 */

As you can see I've had to guess at a lot of these, but I think there is
enough there to allow you to see what is in NDS. By comparing the BACKUP.DS
and *.NDS files, along with the selfOffset at the beginning of each record,
a picture begins to emerge. As we push through this document, you will need
to refer back to these structures.


                 . o O o . [ BACKUP.DS Structure ] . o O o .

If you retrieve BACKUP.DS, you need to reconstruct the NDS files into their
original 4 components. The structure of BACKUP.DS is as follows -

  |---------------|
  |    HEADER     | <------- Header.
  |---------------|
  | Offset to end | <------- This offset is located just past the header.
  | of ENTRY.NDS  |          (unsigned long int)n = Offset/sizeof(VALUE)
  |---------------|          gets the number of records.
  |   ENTRY.NDS   | 
  |---------------|
  | Offset to end | <------- (unsigned long int)n = Offset/sizeof(VALUE)
  | of VALUE.NDS  |          gets the number of records.
  |---------------|
  |   VALUE.NDS   | 
  |---------------|
  | Offset to end | <------- (unsigned long int)n = Offset/sizeof(BLOCK)
  | of BLOCK.NDS  |          gets the number of records.
  |---------------|
  |   BLOCK.NDS   |
  |---------------|
  | Offset to end | <------- (unsigned long int)n = Offset/sizeof(PARTITIO)
  |of PARTITIO.NDS|          gets the number of records.
  |---------------|
  | PARTITIO.NDS  |
  |---------------|


The BACKUP.DS header section has a rather odd structure consisting of
variable data. While I have taken a look at it, it is not that important
when searching for NDS files. It does contain the server and tree name,
and in multi-server environments you will get a copy of the SAP table,
or at least something with a lot of the same information. This is there,
I assume, so that if and/or when you recover NDS your server will have
a fairly clear view of what the network last looked like.
</P><P>
From this information you should be able to write a program in C that will
take a BACKUP.DS file and make the 4 NDS files. If you do not know how (or
do not have the time) to write such a program, use CONVERT.EXE from Pandora
to recreate NDS files from BACKUP.DS.


                   . o O o . [ Fun and Games ] . o O o .

It is possible, starting with PARTITIO.NDS and its reference to ENTRY.NDS,
to follow each cross reference and get a complete dump of NDS. I have not
written such a utility, nor would I care to. But one of the things that
interested me the first time I looked at BACKUP.DS in a hex viewer was that
I could possibly get user passwords. Novell has said that this was 
impossible, and that Netware 4.x uses a public key encryption scheme for
authentication. However this did not stop me from exploring and learning
about the size and structure of individual pieces and attributes. The
details of WHAT can be found are much more interesting than how I discovered
the location of the private key. So what follows is the process to get a 
private key.

The logical thing is to determine what ENTRY.classID value represents a
user object. This is fairly easy to determine by examining ENTRY records
until a user record is found (CN=Admin makes it easy to find). However this
may not be consistent between servers. Although I found that the classID for
users is usually 0x010000af, in one case I found this value to be different.
So to ensure that you have found the correct classID, search all of ENTRY.NDS
looking for objects with the name of "User". If there are two, the last one
is the correct one. This particular object's classID is the ID that says an
ENTRY.NDS record is a user record.

All objects are stored this way in NDS, so the next thing to do is determine
the classID associated with the Private Key object. This can be done by
searching for "Priv". Typically this is 0x01000045, although in one case I
found it was not. Therefore it is important to check to make sure.

To simplify searching of NDS records, all "system" related objects, such as
the User object and Private Key object, all have classIDs of 0xffffffff.
To quicken the search, simply look for ENTRY.NDS records with a classID of
0xffffffff and a name of "User" or "Priv" and you will have the object ID
at ENTRY.id needed for later searching.

Let's say that we have searched ENTRY.NDS and retrieved 0x010000af for User
objects and 0x01000045 for Private Key objects. To retrieve user and password
info from NDS, we first need to search ENTRY.NDS for records with a classID
of 0x010000af. This will get us all of the user records, and by dumping
ENTRY.name you will have the Common Name (CN) of each user. Getting the
ENTRY.id will help us in the next step.

Searching each VALUE.NDS record for the ENTRY.id in VALUE.entryID and
0x01000045 in VALUE.typeID will get us the start of the Private Key.

The private key's size=324, so you will have to follow the VALUE.firstBlock
offset in BLOCK.NDS to retrieve all of the data. Here is an example of the 
first several bytes of a private key:

User "Simple" (object ID=090000c3) private key:
c3 00 00 09 08 00 00 00 8d 49 e4 55 f2 5a 57 0e bb 8a f9 f6 ea 3a f6 88
01 00 00 00 01 00 60 00 20 01 19 01 38 74 08 89 02 c4 97 a3 43 5d 00 86
etc...

Comparing this private key to other private keys, a pattern begins to
emerge from them. The private key has the following structure:

typedef struct PRIV_KEY
{
	uint32		objectID;  /* Object ID of user. */
	uint16		pwLength;  /* Password length. */
	uint16		var1;      /* Unsure. Perhaps unused. */
	uint8		pw[16];    /* The password, one way hashed. */
	uint32          var2;      /* No idea, is always 0x00000001 */
	uint16		var3;      /* No idea, is always 0x0001 */
	uint16		var4;      /* No idea, is always 0x0006 */
	uint32		var5;      /* No idea, is always 0x01190120 */
	uint8		key[288];  /* The private key, encrypted. */
	uint32		var6;      /* No idea... */
	uint32		var7;      /* No idea... */
	uint32		var8;      /* No idea... */
	uint32		var9;      /* No idea... */
} PRIV_KEY; /* size=340 */

While it is interesting that on occassion you will see var8 and var9
equal the first four characters of the user's common name in unicode,
the thing that really looks interesting is the one way encrypted hash. 
From studying bindery files it is known that the Netware 3.x password is
this exact same length. By using the Netware 3.x algorithm that has been 
floating around on the Internet for a couple of years it turns out that
YES this is the one way hash.

Retrieving this info from ENTRY.NDS, VALUE.NDS, and BLOCK.NDS to
specifically grab info for password cracking could be done by simply
looking for the various IDs at the various offsets and writing them out
to a file. To simplify this process, you could use EXTRACT.EXE from
Pandora. EXTRACT.EXE creates an NDS-style password file.

               
             . o O o . [ Security Implications ] . o O o .

If you now have the user's common name, the object ID, the one way hash,
and the algorithm, it should simply be a matter of time to crack the
password. The algorithm used by Novell requires the length of the password,
the password itself, and the object ID to generate the one way hash.
Therefore a dictionary attack could be quite fruitful.

A hard-to-guess password will slow down the process of cracking the 
password considerably. However, the algorithm converts the password to
upper case before encryption, and we know the password length before
we even start cracking. While brute force attacks can be lengthy and 
tiresome, such an attack is not entirely out of the question.

To demonstrate this, you can use CRYPTO.EXE and CRYPTO2.EXE from Pandora 
to perform brute force and dictionary attacks respectively on the password 
file created from EXTRACT.EXE.

Other security implications include the fact that there are a number of
older bindery calls intended for Netware 3.x that may be used against
Netware 4.x, and these bindery calls could allow certain security
measures to be circumvented.

While verifying that the same algorithm from Netware 3.x is being used for
Netware 4.x, it was discovered that by performing a verify password call
you could dictionary or brute force attack an account on a Netware 4.x
server. By default, intruder detection is turned off on a freshly loaded 
Netware 4.x server. If bindery emulation is being used, a "verify password"
call can be used to check whether a user account exists, and whether a
guessed password is correct.

A number of examples of programs used for logging in can adapted over
to perform this type of attack. It has been reported that KNOCK.EXE has
been used by some hackers to gain access to a Netware 4.x server, and I
am aware of one development company of Netware utilities that had
discovered the same thing. To be included in the next version of Pandora 
is INTRUDE.EXE, which can brute force determine user accounts as well as 
passwords. To use INTRUDE.EXE you can be logged in, even with minimal 
rights, but you will not need to be logged to use it.


                   . o O o . [ Summary ] . o O o .

Pandora can be used by an intruder (or an adminsitrator) in the following
fashion to break in (or to determine vulnerability):

- Use INTRUDE.EXE (when available) to determine common user accounts. 
  If none are found, they can be brute forced.

- Use INTRUDE.EXE (when available) to determine passwords. These can be 
  done using either a dictionary or brute force attack. Any account could be 
  attacked, including Supervisor (if it exists) or Admin.

- By exploring using NLIST, NetAdmin, and by trying different accounts,
  determine an account that has read/write access to SYS:SYSTEM.

- If BACKUP.DS exists, it can be copied off of the server.

- By exploring the NCF files it should be possible to determine the remote
  console password, or possibly exploit the read/write access to an NCF file
  to gain console access.

- Once console access is gained, using Novell's DSMAINT a fresh BACKUP.DS
  can be created and copied down.

- BACKUP.DS can be converted into the original NDS files using CONVERT.EXE.

- The NDS files can have EXTRACT.EXE run against them to create the
  PASSWORD.NDS file.

- CRYPTO.EXE or CRYPTO2.EXE can be run against PASSWORD.NDS to do either a 
  brute force attack or a dictionary attack to obtain additional passwords. For
  the intruder, this is safer since these attacks can occur offline.


                   . o O o . . . . . . . . . o O o .


              Simple Nomad - Nomad Mobile Research Centre
                thegnome@nmrc.org - http://www.nmrc.org
                            June 27, 1997
