Ubuntu Manpage: smbpasswd - The Samba encrypted password file

Provided by: samba-common-bin_4.15.13+dfsg-0ubuntu1.10_amd64

NAME

       smbpasswd - The Samba encrypted password file

SYNOPSIS

       smbpasswd

DESCRIPTION

       This tool is part of the samba(7) suite.

       smbpasswd is the Samba encrypted password file. It contains the username, Unix user id and the SMB hashed
       passwords of the user, as well as account flag information and the time the password was last changed.
       This file format has been evolving with Samba and has had several different formats in the past.

FILE FORMAT

The format of the smbpasswd file used by Samba 2.2 is very similar to the familiar Unix passwd(5) file.
It is an ASCII file containing one line for each user. Each field within each line is separated from the
next by a colon. Any entry beginning with '#' is ignored. The smbpasswd file contains the following
information for each user:

name
This is the user name. It must be a name that already exists in the standard UNIX passwd file.

uid
This is the UNIX uid. It must match the uid field for the same user entry in the standard UNIX passwd
file. If this does not match then Samba will refuse to recognize this smbpasswd file entry as being
valid for a user.

Lanman Password Hash
This is the LANMAN hash of the user's password, encoded as 32 hex digits. The LANMAN hash is created
by DES encrypting a well known string with the user's password as the DES key. This is the same
password used by Windows 95/98 machines. Note that this password hash is regarded as weak as it is
vulnerable to dictionary attacks and if two users choose the same password this entry will be
identical (i.e. the password is not "salted" as the UNIX password is). If the user has a null
password this field will contain the characters "NO PASSWORD" as the start of the hex string. If the
hex string is equal to 32 'X' characters then the user's account is marked as disabled and the user
will not be able to log onto the Samba server.

WARNING !! Note that, due to the challenge-response nature of the SMB/CIFS authentication protocol,
anyone with a knowledge of this password hash will be able to impersonate the user on the network.
For this reason these hashes are known as plain text equivalents and must NOT be made available to
anyone but the root user. To protect these passwords the smbpasswd file is placed in a directory with
read and traverse access only to the root user and the smbpasswd file itself must be set to be
read/write only by root, with no other access.

NT Password Hash
This is the Windows NT hash of the user's password, encoded as 32 hex digits. The Windows NT hash is
created by taking the user's password as represented in 16-bit, little-endian UNICODE and then
applying the MD4 (internet rfc1321) hashing algorithm to it.

This password hash is considered more secure than the LANMAN Password Hash as it preserves the case
of the password and uses a much higher quality hashing algorithm. However, it is still the case that
if two users choose the same password this entry will be identical (i.e. the password is not "salted"
as the UNIX password is).

WARNING !!. Note that, due to the challenge-response nature of the SMB/CIFS authentication protocol,
anyone with a knowledge of this password hash will be able to impersonate the user on the network.
For this reason these hashes are known as plain text equivalents and must NOT be made available to
anyone but the root user. To protect these passwords the smbpasswd file is placed in a directory with
read and traverse access only to the root user and the smbpasswd file itself must be set to be
read/write only by root, with no other access.

Account Flags
This section contains flags that describe the attributes of the users account. This field is
bracketed by '[' and ']' characters and is always 13 characters in length (including the '[' and ']'
characters). The contents of this field may be any of the following characters:

• U - This means this is a "User" account, i.e. an ordinary user.

• N - This means the account has no password (the passwords in the fields LANMAN Password
Hash and NT Password Hash are ignored). Note that this will only allow users to log on
with no password if the
null passwords parameter is set in the smb.conf(5) config file.

• D - This means the account is disabled and no SMB/CIFS logins will be allowed for this
user.

• X - This means the password does not expire.

• W - This means this account is a "Workstation Trust" account. This kind of account is used
in the Samba PDC code stream to allow Windows NT Workstations and Servers to join a Domain
hosted by a Samba PDC.

Other flags may be added as the code is extended in future. The rest of this field space is filled in
with spaces. For further information regarding the flags that are supported please refer to the man
page for the pdbedit command.

Last Change Time
This field consists of the time the account was last modified. It consists of the characters 'LCT-'
(standing for "Last Change Time") followed by a numeric encoding of the UNIX time in seconds since
the epoch (1970) that the last change was made.

All other colon separated fields are ignored at this time.

VERSION

       This man page is part of version 4.15.13-Ubuntu of the Samba suite.

AUTHOR