passwd

Purpose

     Contains passwords.

Library

     Standard C Library (libc.a)

Synopsis

     #include (pwd.h)

Description

     The passwd  file is an  ASCII file that contains  all the
     information that defines  a user on the  system.  It con-
     tains the following information:

     o   Login name
     o   Encrypted password
     o   Numerical user ID
     o   Numerical group ID
     o   Additional data for each user
     o   Initial current directory
     o   Program to use as shell.

     Each field  is separated from  the next by a  colon.  The
     file has  general read  permission and the  passwords are
     encrypted.  Therefore,  a user  can use  the file  to map
     numerical user  IDs to names without  potentially compro-
     mising the security of other users.

     The adduser command is used  to maintain this file.  Pro-
     grams  should use  the  getpwent  subroutines to  extract
     various fields in this file.

     &c2del.  If the user password field is null, the user has
     no password.   &c2off.  &c2ins.  The user  password field
     is  empty.    Encrypted  passwords  are  stored   in  the
     /etc/security/s_user  file (see  "s_user").  &c2off.   If
     the program field  is null, the shell  (/bin/sh) is used.
     The program field can  contain parameters passed when the
     exec system call is  issued.  Parameters are separated by
     space (such  as a space  or tab characters).  A  \ (back-
     slash) is used for escapement when a parameter contains a
     space.  The login command accepts the program name and as
     many as 14  parameters.  Any more than  14 parameters are
     ignored.  A  maximum of 4096  characters can be  used for
     the  program name  and  its parameters.   More than  4096
     characters  causes login  to  exit.   Parameters in  this
     field  can  use  symbolic escapement  for  the  following
     special characters:  \n, \r,  \v (produces 013),  \b, \t,

     and \f.   Additionally, \0  through \7 builds  a one-byte
     octal number.   Anything else that  is preceded with  a \
     (backslash) passes through.

     The contents of the additional data for each user has the
     following format:

     full_name / file_limit ; site_info

     where:

     full_name   Contains   the  name   of   the  user   whose
                 8-character (or  fewer) login name is  in the
                 first field.

                 If a  user group list  is used, the  list may
                 not exceed 500 eight-character login names.

     file_limit  Specifies  the maximum  length file  the user
                 can  create.  See  the login  command in  AIX
                 Operating System  Commands Reference  and the
                 ulimit system call.

     site_info   Contains any printable character other than a
                 colon.  This subfield is unused by the system
                 software and is available for information for
                 each  user as  required by  applications spe-
                 cific to the site.

     Any  or all  of the  subfields  can be  omitted.  If  the
     file_limit subfield  is omitted, the preceding  / (slash)
     is omitted and the system-wide default limit is used.  If
     the site_info subfield is omitted, the preceding ; (semi-
     colon) is also omitted.  &c2ins.  &c2off.

     Passwords

     The encrypted password is  13 characters long.  The char-
     acters used come from  the extended characters (code page
     P0, see "data stream") and  may be uppercase or lowercase
     characters, numerals,  and the  . (period) and  / (slash)
     characters  except when  the password  is null.   In this
     case,  the encrypted  password  is  also null.   Password
     aging affects a  particular user if a comma  and a string
     of characters that are not null follows the user password
     in this file.  Such a string must be initially introduced
     by a person with superuser authority.

     The first  character of  the age, M  for example,  is the
     maximum number  of weeks a  password is valid.   The next
     character, m for example, is the minimum number of weeks,
     before the password can  be changed.  The remaining char-
     acters indicate when the password was last changed, given
     as the number of weeks since the beginning of 1970 to the
     time of the password change.  A null string is equivalent
     to  0.  M  and m  have numerical  values in  the range  0
     through 63.  If m  = M = 0, the user  is forced to change
     the password at  the next login.  This causes  the age to

     disappear from the  password file entry.  If m  > M, only
     someone with  superuser authority  is able to  change the
     password.

File

     /etc/passwd
     &c2ins.
     /etc/security/s_user
     &c2off.

Related Information

     In   this  book:    "a64l,  l64a,"    "crypt,  encrypt,"
     "getpwent,   getpwuid,  getpwnam,   setpwent,  endpwent,"
     "ulimit," "group," &c2ins.   "s_user," &c2off.  and "data
     stream."

     The  login and  passwd commands  in AIX  Operating System
     Commands Reference.

     "Overview of International Character Support" in Managing
     the AIX Operating System.

     &c2ins.