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       lpd.perms - permissions control file for the LPRng line printer spooler


       The file lpd.perms is used to provide permission  information  for  the
       LPRng  Printer  spooler system.  Blank lines and all characters after a
       hash sign (‘‘#’’) to the end of line are ignored.  If a  hash  sign  is
       desired  in  the  permission  information,  it should be escaped with a
       backslash (‘‘\’’).  All  other  lines  specify  permissions  entry  and
       should be of the following form:
              ACCEPT [[not] key = value[,value]* ]*
              REJECT [[not] key = value[,value]* ]*
              DEFAULT ACCEPT
              DEFAULT REJECT

       Each  LPD  service  request  is  checked  against  the  entries  in the
       permissions database or file.  The following is a  typical  permissions
              # Set default permissions
              DEFAULT ACCEPT
              # Reject any connections from outside our subnet
              # Only accept spooling (LPR) from
              # Engineering Lab or the Dean’s office
              # Do not accept forwarded jobs for printing
              # Allow only the administrators control access
              ACCEPT SERVICE=C,M REMOTEUSER=root,papowell
              ACCEPT SERVICE=C,M SERVER REMOTEUSER=root,papowell
              # Allow only the user on the same host who spooled job to remove it
              # Allow users to check status
              ACCEPT SERVICE=C LPC=status
              # Require connection for other operations over UNIX socket
              # not TCP/IP port.  Effectively requiring them to be made from the
              # localhost
              REJECT SERVICE=C

              # Variation - accept all spooled jobs,  but then apply
              #  permissions checking when job is printed.  Allows
              #  prevents remote spoolers from locking up trying resend
              #  same request
              ACCEPT SERVICE=R

       Permission  checking  is  done  by using a set of keys (or fields) with
       associated values to check for permission.  The SERVICE key has value P
       for  printing (i.e.- unspooling), R for spooling (i.e.- LPR request), P
       for printing (i.e., after job has  been  spooled),  C  printer  control
       (i.e.  -  LPC),  M  for  removal  (i.e.- LPRM request), and Q for queue
       information (i.e.- LPQ request).  The X key is used when  checking  for
       connection information.

       Initially,  all  of  the  keys  have  undefined or NULL values, and are
       assigned values  during  the  permissions  checking  process.   When  a
       connection  is  made  to  the  server, it assigns The REMOTEHOST (alias
       REMOTEIP) key the list of IP  addresses  and  hostnames  determined  by
       doing  a  reverse Domain Name Service (DNS) lookup on the remote host’s
       IP address.  If the reverse DNS fails, then only the IP address will be
       used.  The REMOTEPORT (PORT is an alias for REMOTEPORT) is assigned the
       port number of the connection origination.   The  UNIXSOCKET  key  will
       match  (be  true)  if  the  connection  is  over  a  UNIX  socket.   By
       convention, this is from the localhost.  Finally, the SERVICE value  is
       assigned  X,  and  the lpd server will check the database to see if the
       connection is accepted or rejected.

       The server will then read the request information from the  connection.
       If  the  request is for an authenticated data transfer, the server will
       invoke the appropriate authentication mechanism which will assign  AUTH
       a  true  (or  matching)  value,  AUTHTYPE  the  type of authentication,
       AUTHUSER the authenticated user id value, which  may  differ  from  the
       actual  user name, and AUTHFROM the authenticated identification of the
       originator of the request, which may be a  server  if  the  request  is

       Next, the SERVICE value is set to R, C, M, or Q depending on whether it
       is an LPR, LPC, LPRM, or LPQ request, and the  LPC  value  set  to  the
       requested  LPC  command  if  it  was  an  LPC  request.  If the request
       contained a user name, then REMOTEUSER is set to  this  name.   If  the
       request  contained  a  printer name, then PRINTER is set to the printer
       name.  If the request is a print request, then the HOST value is set to
       the  list  of  host names and IP addresses given by a DNS lookup of the
       value in the H field of the job.  The  database  is  scanned  again  to
       determine if the operation can be performed on the requested queue.  To
       simplify the rule writing, if the operation  requires  modification  or
       checking  of  individual  jobs, such as the LPC, LPQ, or LPRM commands,
       then the various checks that depend on jobs will succeed in this  step.

       Finally,   if  the  operation  requires  modification  or  checking  of
       individual jobs, such as the LPC,  LPQ,  or  LPRM  commands,  then  the
       specified  print queue is scanned, and for each job in the print queue,
       the HOST and USER values are set to the host and  user  values  in  the
       control file for the job.

       The  database is checked as follows.  Each line of the permissions file
       is scanned for key names and values, and these are matched against  the
       request  keys  information.   When all matches on a line are made, then
       search terminates with the specified  action  (ACCEPT/REJECT).   If  no
       match  is  found the default permission value is used.  The DEFAULT key
       is used to specify the  current  default  permission  to  be  used  for
       successful  matches  or  if there is no match after scanning the entire
       permissions database.

       The following keys provide some additional checking capabilities.   The
       REMOTEGROUP  entry  checks that the REMOTEUSER value appears in a group
       or netgroup entry in the system database, and the GROUP entry  for  the
       USER  value.   For example, GROUP=student*,staff* would check to see if
       any of the group names matching student* or staff* have  the  specified
       user  name  in  them.   If  a  system  has  the netgroups capability, a
       printer, group, or remotegroup name starting with a @ will  be  treated
       as  a netgroup name, and specified user name or printer will be checked
       to see if it is in the group.

       The SERVER entry will be true (match) if the  request  originated  from
       the print server.  The SAMEHOST is true (matches) if the REMOTEHOST and
       HOST values have a common  entry,  i.e.  -  are  the  same  host.   The
       SAMEUSER  is  true  (matches)  if  the  REMOTEUSER  and USER values are
       identical.  The AUTHSAMEUSER is true (matches) if  the  AUTHUSER  value
       that originated the request and the AUTHUSER which was used to transfer
       a job are  identical.   AUTHJOB  is  true  (matches)  if  the  job  was
       transferred  using  authentication.   The FORWARD value is an alias for

       The CONTROLLINE value can be used to determine if there is  a  matching
       line  in  the control file.  This facility has been used to ensure that
       jobs contain various information fields in order to be printed.

       Key          Match Connect Job   Job    LPQ  LPRM  LPC
                                  Spool Print
       SERVICE      S     ’X’     ’R’   ’P’    ’Q’  ’M’   ’C,S’
       USER         S     -       JUSR  JUSR   JUSR JUSR  JUSR
       HOST         S     RH      JH    JH     JH   JH    JH
       GROUP        S     -       JUSR  JUSR   JUSR JUSR  JUSR
       REMOTEPORT   N     PORT    PORT  -      PORT PORT  PORT
       REMOTEUSER   S     -       JUSR  JUSR   JUSR CUSR  CUSR
       REMOTEHOST   S     RH      RH    JH     RH   RH    RH
       UNIXSOCKET   V     SK      SK    SK     SK   SK    SK
       CONTROLLINE  S     -       CL    CL     CL   CL    CL
       PRINTER      S     -       PR    PR     PR   PR    PR
       FORWARD      V     -       SA    -      -    SA    SA
       SAMEHOST     V     -       SA    -      SA   SA    SA
       SAMEUSER     V     -       -     -      SU   SU    SU
       SERVER       V     -       SV    -      SV   SV    SV
       AUTH         V     -       AU    -      AU   AU    AU
       AUTHTYPE     S     -       AU    -      AU   AU    AU
       AUTHUSER     S     -       AU    -      AU   AU    AU
       AUTHSAMEUSER S     -       AU    -      AU   AU    AU
       AUTHFROM     S     -       AU    -      AU   AU    AU
       AUTHJOB      V     -       AU    -      AU   AU    AU
         PORT is alias for REMOTEPORT
         REMOTEIP is alias for REMOTEHOST
         IP is alias for HOST

          JH = HOST          host in control file
          RH = REMOTEHOST    connecting host name/IP
          JUSR = USER        user in control file
          CUSR = REMOTEUSER  user from control request
          JIP= IP            host/IP addr of host in control file
          RIP= REMOTEIP      host/IP addr of requesting host
          PORT=              connecting host origination port
           SK=  match if connection over a UNIX socket
          CONTROLLINE=       pattern match of control line in control file
          FW= IP of source of request == IP of host in control file
          SA= IP of source of request == IP of host in control file
          SU= user from request == user in control file
          SA= IP of source of request == IP of server host
          SV= matches if from same address as server
          AU= value determined by server authentication operation
                             AUTH is true if authenticated transfer,
                             TYPE is set to the type of authentication (pgp, kerberos, etc)
                             AUTHUSER is user authentication id
                             AUTHFROM is sender authentication id (can be remote server)
                             AUTHSAMEUSER matches if remote user authentication id matches original
                             user authentication id
                             AUTHJOB it true if print job has authentication
       Match: S = string with wild card, IP = IP address[/netmask],
          N = low[-high] number range, V = exact value match
       SERVICE: ’X’ - Connection request; ’R’ - lpr request from remote host;
           ’P’ - print job in queue; ’Q’ - lpq request, ’M’ - lprm request;
           ’C’ - lpc spool control request; ’S’ - lpc spool status request
          ’U’ - administratively allowed user operation
       NOTE: when printing (P action), the remote and job check values
          (i.e. - RUSR, JUSR) are identical.

       The special key letter=patterns searches the control file line starting
       with  the  (upper  case)  letter, and is usually used with printing and
       spooling checks.  For example,  C=A*,B*  would  check  that  the  class
       information  (i.e.-  line  in  the  control file starting with C) had a
       value starting with A or B.

       A permission line consists of a list of tests and a result  value.   If
       all  of  the  tests  succeed,  then  a  match  has  been  found and the
       permission testing completes  with  the  result  value.   You  use  the
       DEFAULT  reserved  word to set the default ACCEPT/DENY result.  The NOT
       keyword will reverse the sense of a test.

       Each test can have one or more optional values separated by commas. For
       example  USER=john,paul,mark  has  3  test  values.   The  Match  value
       specifies how the matching is done.

       S = string type match - string match with glob.
           Format:  string with wildcards (*)
               * matches 0 or more chars
           Character comparison is case insensitive.
           For example - USER=th*s matches uTHS, This, This, Theses

       IP = IP address and submask.  IP address must be in dotted form.
           Format: x.x.x.x[/y.y.y.y or /z]
               x.x.x.x is IP address
               y.y.y.y is optional submask, default is
               z is a netmask with most significant z bits set.
           Match is done by IP address to a 32 bit value and using:
               success = ((x ^ IP ) & y) == 0   (C language notation)
           i.e.- only bits where mask is non-zero are used in comparison.
           For example - IP= matches all address 130.191.X.X
           IP= has the same value.

       N = numerical range  -  low-high integer range.
           Format: low[-high]
           Example: PORT=0-1023 matches a port in range 0 - 1023 (privileged)

       The authentication entries AUTH, AUTHTYPE, AUTHUSER,  AUTHSAMEUSER  and
       AUTHFROM can be used to check permissions for authenticated operations.
       AUTH is set (true) if authentication was done.   We  can  use  this  to
       reject non-authenticated transfers:
       The AUTHTYPE will match the authentication type being used or requested
       by the remote client or server.   The  AUTHUSER  matches  the  original
       client  authentication information used by the client to make a request
       to the server, and  the  AUTHFROM  matches  the  sender  authentication
       information.   The AUTHSAMEUSER will match if the remote client or user
       authentication id is the same as that used for the job generation.


       The  LPC=op  entry  is  useful  to  allow  various  users  to   perform
       administration  operations.   The  following  permissions  entry  would
       allows users to hold or release their own jobs:


       There is a subtle  problem  with  names  and  IP  addresses  which  are
       obtained  for  ’multi-homed hosts’, i.e. - those with multiple Ethernet
       interfaces,  and for IPV6 (IP Version 6),  in which  a  host  can  have
       multiple  addresses,   and  for  the  normal host which can have both a
       short name and a fully qualified domain name.

       When performing an IP address match,  the entire list of  IP  addresses
       for  a  system  will  now  be  checked.   If one of these matches, then
       success is reported.  Similarly,  the entire list  of  host  names  and
       aliases  will  be checked.  If one of these matches,  then success will
       be reported.


       The files used by LPRng are set by values in the printer  configuration
       file.  The following are a commonly used set of default values.
       //etc/lprng/lpd.conf                         LPRng configuration file
       ${HOME}/.printcap                            user printer description file
       //etc/printcap                               printer description file
       //etc/lprng/lpd.perms                        permissions
       /var/run/lprng/lpd                           lock file for queue control
       /var/spool/lpd                               spool directories
       /var/spool/lpd/QUEUE/control                 queue control
       /var/spool/lpd/QUEUE/log                     trace or debug log file
       /var/spool/lpd/QUEUE/acct                    accounting file
       /var/spool/lpd/QUEUE/status                  status file


       lpd.conf(5),  lpc(8),  lpd(8),  checkpc(8),  lpr(1),  lpq(1),  lprm(1),
       printcap(5), pr(1), lprng_certs(1), lprng_index_certs(1).


       Patrick Powell <>.


       LPRng is a enhanced printer spooler system with  functionality  similar
       to  the  Berkeley  LPR  software.   The LPRng developer mailing list is;      subscribe      by      visiting   or   sending
       mail to with the word subscribe  in
       the body.
       The software is available via