NAME
lpd.perms - permissions control file for the LPRng line printer spooler
system
DESCRIPTION
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
file:
# Set default permissions
DEFAULT ACCEPT
# Reject any connections from outside our subnet
REJECT SERVICE=X NOT REMOTEIP=130.191.0.0/255.255.0.0
# Only accept spooling (LPR) from
# Engineering Lab or the Dean’s office
REJECT SERVICE=R NOT REMOTEHOST=*.eng.sdsu.edu,dean.sdsu.edu
# Do not accept forwarded jobs for printing
REJECT SERVICE=R FORWARD
# Allow only the administrators control access
ACCEPT SERVICE=C,M REMOTEHOST=spooler.eng.sdsu.edu 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
ACCEPT SERVICE=M SAMEUSER SAMEHOST
# 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
ACCEPT SERVICE=C UNIXSOCKET
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
REJECT SERVICE=P NOT REMOTEHOST=*.eng.sdsu.edu,dean.sdsu.edu
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
forwarded.
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
NOT SAMEHOST.
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
REMOTEGROUP S - JUSR JUSR JUSR CUSR CUSR
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
KEY:
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 255.255.255.255
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=130.191.0.0/255.255.0.0 matches all address 130.191.X.X
IP=130.191.0.0/16 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:
REJECT NOT AUTH
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.
LPC=OP
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:
ACCEPT SERVICE=C SAMEUSER SAMEHOST LPC=release
DNS, IPV6, AND MULTIHOMED HOSTS
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.
FILES
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
SEE ALSO
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).
AUTHOR
Patrick Powell <papowell@lprng.com>.
HISTORY
LPRng is a enhanced printer spooler system with functionality similar
to the Berkeley LPR software. The LPRng developer mailing list is
lprng-devel@lists.sourceforge.net; subscribe by visiting
https://lists.sourceforge.net/lists/listinfo/lprng-devel or sending
mail to lprng-request@lists.sourceforge.net with the word subscribe in
the body.
The software is available via http://lprng.sourceforge.net