smbpasswd (5)

Samba

23 Oct 1998

NAME

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 "NO PASSWORD" as the start of the hex string. If the hex string is equal to 32 '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 '[' and ']' characters and is always 13 characters in length (including the '[' and ']' characters). The contents of this field may be any of the characters.

  
  

  
  

  • '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.

    
    

  • '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.

    
    

  • '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 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.

  
  

• 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 bin/ 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 <old smbpasswd file> with the <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-bugs@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-bugs@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.