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Namesmbpasswd - The Samba encrypted password file
Synopsis
smbpasswd is the
Samba encrypted password file.
Description
This file is part of the Samba
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 2.0 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 users password, encoded as 32 hex digits.
The LANMAN hash is created by DES encrypting a well known string with the
users 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 CW"NO PASSWORD" as the start of the hex string. If the hex string
is equal to 32 CW'X' characters then the users 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 equivalent" 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 users password, encoded as 32 hex digits.
The Windows NT hash is created by taking the users 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 equivalent" 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.
In the Samba2.0 release this field is bracketed by CW'[' and CW']' characters
and is always 13 characters in length (including the CW'[' and CW']' characters).
The contents of this field may be any of the characters. o'U' This means this
is a "User" account, i.e. an ordinary user. Only User and Workstation Trust
accounts are currently supported in the smbpasswd file. o'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. o'D' This means the account is disabled and no SMB/CIFS
logins will be allowed for this user. o'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. Last Change Time
This field consists of the time the account was last modified. It consists
of the characters CWLCT- (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. Following fields
All other colon separated fields are ignored at this time.
Notes
In previous
versions of Samba (notably the 1.9.18 series) this file did not contain the
Account Flags or Last Change Time fields. The Samba 2.0 code will read and
write these older password files but will not be able to modify the old
entries to add the new fields. New entries added with smbpasswd (8) will
contain the new fields in the added accounts however. Thus an older smbpasswd
file used with Samba 2.0 may end up with some accounts containing the new
fields and some not.
In order to convert from an old-style smbpasswd file
to a new style, run the script convert_smbpasswd, installed in the Samba
CWbin/ directory (the same place that the smbd and nmbd binaries are installed)
as follows:
cat old_smbpasswd_file | convert_smbpasswd > new_smbpasswd_file
The convert_smbpasswd script reads from stdin and writes to stdout so
as not to overwrite any files by accident.
Once this script has been run,
check the contents of the new smbpasswd file to ensure that it has not
been damaged by the conversion script (which uses awk), and then replace
the CW<old smbpasswd file> with the CW<new smbpasswd file>.
Version
This man
page is correct for version 2.0 of the Samba suite.
See Also
smbpasswd (8),
samba (7), and the Internet RFC1321 for details on the MD4 algorithm.
Author
The
original Samba software and related utilities were created by Andrew Tridgell
samba@samba.org. Samba is now developed by the Samba Team as an Open Source
project similar to the way the Linux kernel is developed.
The original Samba
man pages were written by Karl Auer. The man page sources were converted
to YODL format (another excellent piece of Open Source software, available
at ftp://ftp.icce.rug.nl/pub/unix/) and updated for the Samba2.0 release by
Jeremy Allison, samba@samba.org.
See samba (7) to find out how to get a full
list of contributors and details on how to submit bug reports, comments
etc.
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