382 lines
14 KiB
Plaintext
382 lines
14 KiB
Plaintext
@(#)@(#)README 2.6 2.6 4/2/91
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The Post Office Protocol Server: Installation Guide
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Introduction
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The Post Office Protocol server runs on a variety of Unix[1] computers
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to manage electronic mail for Macintosh and MS-DOS computers. The
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server was developed at the University of California at Berkeley and
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conforms fully to the specifications in RFC 1081[2] and RFC 1082[3].
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The Berkeley server also has extensions to send electronic mail on
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behalf of a client.
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This guide explains how to install the POP server on your Unix
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computer. It assumes that you are not only familiar with Unix but also
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capable of performing Unix system administration.
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How to Obtain the Server
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The POP server is available via anonymous ftp from ftp.CC.Berkeley.EDU
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(128.32.136.9, 128.32.206.12). It is in two files in the pub directory:
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a compressed tar file popper-version.tar.Z and a Macintosh StuffIt archive
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in BinHex format called MacPOP.sit.hqx.
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Contents of the Distribution
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The distribution contains the following:
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+ All of the C source necessary to create the server program.
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+ A visual representation of how the POP system works.
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+ Reprints of RFC 1081 and RFC 1082.
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+ A HyperCard stack POP client implementation using MacTCP.
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+ A man page for the popper daemon.
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+ This guide.
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Compatibility
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The Berkeley POP server has been successfully tested on the following
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Unix operating systems:
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+ Berkeley Systems Distribution 4.3
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+ Sun Microsystems Operating System versions 3.5 and 4.0
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+ Ultrix version 2.3
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The following POP clients operate correctly with the Berkeley POP server:
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+ The Berkeley HyperMail HyperCard stack for the Apple Macintosh
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(distributed with the server).
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+ The Stanford University Macintosh Internet Protocol MacMH program.
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+ The Stanford University Personal Computer Internet Protocol MH
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program.
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+ The mh version 6.0 programs for Unix.
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Support
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The Berkeley POP server is not officially supported and is without any
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warranty, explicit or implied. However, we are interested in your
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experiences using the server. Bugs, comments and suggestions should be
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sent electronically to netinfo@garnet.Berkeley.EDU.
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Operational Characteristics
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The POP Transaction Cycle
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The Berkeley POP server is a single program (called popper) that is
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launched by inetd when it gets a service request on the POP TCP port.
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(The official port number specified in RFC 1081 for POP version 3 is
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port 110. However, some POP3 clients attempt to contact the server at
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port 109, the POP version 2 port. Unless you are running both POP2 and
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POP3 servers, you can simply define both ports for use by the POP3
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server. This is explained in the installation instructions later on.)
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The popper program initializes and verifies that the peer IP address is
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registered in the local domain, logging a warning message when a
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connection is made to a client whose IP address does not have a
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canonical name. For systems using BSD 4.3 bind, it also checks to see
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if a cannonical name lookup for the client returns the same peer IP
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address, logging a warning message if it does not. The the server
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enters the authorization state, during which the client must correctly
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identify itself by providing a valid Unix userid and password on the
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server's host machine. No other exchanges are allowed during this
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state (other than a request to quit.) If authentication fails, a
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warning message is logged and the session ends. Once the user is
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identified, popper changes its user and group ids to match that of the
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user and enters the transaction state. The server makes a temporary
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copy of the user's maildrop (ordinarily in /usr/spool/mail) which is
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used for all subsequent transactions. These include the bulk of POP
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commands to retrieve mail, delete mail, undelete mail, and so forth. A
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Berkeley extension also allows the user to submit a mail parcel to the
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server who mails it using the sendmail program (this extension is
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supported in the HyperMail client distributed with the server). When
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the client quits, the server enters the final update state during which
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the network connection is terminated and the user's maildrop is updated
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with the (possibly) modified temporary maildrop.
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Logging
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The POP server uses syslog to keep a record of its activities. On
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systems with BSD 4.3 syslogging, the server logs (by default) to the
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"local0" facility at priority "notice" for all messages except
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debugging which is logged at priority "debug". The default log file is
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/usr/spool/mqueue/POPlog. These can be changed, if desired. On
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systems with 4.2 syslogging all messages are logged to the local log
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file, usually /usr/spool/mqueue/syslog.
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Problems
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If the filesystem which holds the /usr/spool/mail fills up users will
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experience difficulties. The filesystem must have enough space to hold
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(approximately) two copies of the largest mail box. Popper (v1.81 and
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above) is designed to be robust in the face of this problem, but you may
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end up with a situation where some of the user's mail is in
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/usr/spool/mail/.userid.pop
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and some of the mail is in
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/usr/spool/mail/userid
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If this happens the System Administrator should clear enough disk space
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so that the filesystem has at least as much free disk as both mailboxes
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hold and probably a little more. Then the user should initiate a POP
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session, and do nothing but quit. If the POP session ends without an
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error the user can then use POP or another mail program to clean up his/her
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mailbox.
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Alternatively, the System Administrator can combine the two files (but
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popper will do this for you if there is enough disk space).
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Debugging
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The popper program will log debugging information when the -d parameter
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is specified after its invocation in the inetd.conf file. Care should
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be exercised in using this option since it generates considerable
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output in the syslog file. Alternatively, the "-t <file-name>" option
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will place debugging information into file "<file-name>" using fprintf
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instead of syslog. (To enable debugging, you must edit the Makefile
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to add -DDEBUG to the compiler options.)
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For SunOS version 3.5, the popper program is launched by inetd from
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/etc/servers. This file does not allow you to specify command line
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arguments. Therefore, if you want to enable debugging, you can specify
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a shell script in /etc/servers to be launched instead of popper and in
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this script call popper with the desired arguments.
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Installation
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1. Examine this file for the latest information, warnings, etc.
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2. Check the Makefile for conformity with your system.
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3. Issue the make command in the directory containing the popper
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source.
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4. Issue the make install command in the directory containing the
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popper source to copy the program to /usr/etc.
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5. Enable syslogging:
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+ For systems with 4.3 syslogging:
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Add the following line to the /etc/syslog.conf file:
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local0.notice;local0.debug /usr/spool/mqueue/POPlog
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Create the empty file /usr/spool/mqueue/POPlog.
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Kill and restart the syslogd daemon.
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+ For systems with 4.2 syslogging:
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Be sure that you are logging messages of priority 7 and higher.
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For example:
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7/usr/spool/mqueue/syslog
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9/dev/null
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6. Update /etc/services:
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Add the following line to the /etc/services file:
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pop 110/tcp
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Note: This is the official port number for version 3 of the
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Post Office Protocol as defined in RFC 1081. However, some
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POP3 clients use port 109, the port number for the previous
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version (2) of POP. Therefore you may also want to add the
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following line to the /etc/services file:
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pop2 109/tcp
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For Sun systems running yp, also do the following:
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+ Change to the /var/yp directory.
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+ Issue the make services command.
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7. Update the inetd daemon configuration. Include the second line ONLY if you
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are running the server at both ports.
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+ On BSD 4.3 and SunOS 4.0 systems, add the following line to the
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/etc/inetd.conf file:
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pop stream tcp nowait root /usr/etc/popper popper
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pop2 stream tcp nowait root /usr/etc/popper popper
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+ On Ultrix systems, add the following line to the
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/etc/inetd.conf file:
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pop stream tcp nowait /usr/etc/popper popper
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pop2 stream tcp nowait /usr/etc/popper popper
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+ On SunOS 3.5 systems, add the following line to the
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/etc/servers file:
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pop tcp /usr/etc/popper
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pop2 tcp /usr/etc/popper
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Kill and restart the inetd daemon.
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You can confirm that the POP server is running on Unix by telneting to
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port 110 (or 109 if you set it up that way). For example:
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%telnet myhost 110
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Trying...
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Connected to myhost.berkeley.edu.
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Escape character is '^]'.
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+OK UCB Pop server (version 1.6) at myhost starting.
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quit
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Connection closed by foreign host.
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Release Notes
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1.83 Make sure that everything we do as root is non-destructive.
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1.82 Make the /usr/spool/mail/.userid.pop file owned by the user rather
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than owned by root.
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1.81 There were two versions of 1.7 floating around, 1.7b4 and 1.7b5.
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The difference is that 1.7b5 attempted to save disk space on
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/usr/spool/mail by deleting the users permanent maildrop after
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making the temporary copy. Unfortunately, if compiled with
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-DDEBUG, this version could easily wipe out a users' mail file.
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This is now fixed.
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This version also fixes a security hole for systems that have
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/usr/spool/mail writeable by all users.
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With this version we go to all new SCCS IDs for all files. This
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is unfortunate, and we hope it is not too much of a problem.
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Thanks to Steve Dorner of UIUC for pointing out the major problem.
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1.7 Extensive re-write of the maildrop processing code contributed by
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Viktor Dukhovni <viktor@math.princeton.edu> that greatly reduces the
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possibility that the maildrop can be corrupted as the result of
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simultaneous access by two or more processes.
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Added "pop_dropcopy" module to create a temporary maildrop from
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the existing, standard maildrop as root before the setuid and
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setgid for the user is done. This allows the temporary maildrop
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to be created in a mail spool area that is not world read-writable.
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This version does *not* send the sendmail "From " delimiter line
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in response to a TOP or RETR command.
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Encased all debugging code in #ifdef DEBUG constructs. This code can
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be included by specifying the DEGUG compiler flag. Note: You still
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need to use the -d or -t option to obtain debugging output.
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1.6 Corrects a bug that causes the server to crash on SunOS
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4.0 systems.
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Uses varargs and vsprintf (if available) in pop_log and
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pop_msg. This is enabled by the "HAVE_VSPRINTF"
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compiler flag.
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For systems with BSD 4.3 bind, performs a cannonical
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name lookup and searches the returned address(es) for
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the client's address, logging a warning message if it
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is not located. This is enabled by the "BIND43"
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comiler flag.
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Removed all the includes from popper.h and distributed
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them throughout the porgrams files, as needed.
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Reformatted the source to convert tabs to spaces and
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shorten lines for display on 80-column terminals.
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1.5 Creates the temporary maildrop with mode "600" and
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immediately unlinks it.
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Uses client's IP address in lieu of a canonical name if
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the latter cannot be obtained.
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Added "-t <file-name>" option. The presence of this
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option causes debugging output to be placed in the file
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"file-name" using fprintf instead of the system log
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file using syslog.
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Corrected maildrop parsing problem.
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1.4 Copies user's mail into a temporary maildrop on which
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all subsequent activity is performed.
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Added "pop_log" function and replaced "syslog" calls
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throughout the code with it.
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1.3 Corrected updating of Status: header line.
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Added strncasecmp for systems that do not have one.
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Used strncasecmp in all appropriate places. This is
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enabled by the STRNCASECMP compiler flag.
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1.2 Support for version 4.2 syslogging added. This is
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enabled by the SYSLOG42 compiler flag.
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1.1 Several bugs fixed.
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1.0 Original version.
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Limitations
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+ The POP server copies the user's entire maildrop to /tmp and
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then operates on that copy. If the maildrop is particularly
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large, or inadequate space is available in /tmp, then the
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server will refuse to continue and terminate the connection.
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+ Simultaneous modification of a single maildrop can result in
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confusing results. For example, manipulating messages in a
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maildrop using the Unix /usr/ucb/mail command while a copy of
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it is being processed by the POP server can cause the changes
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made by one program to be lost when the other terminates. This
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problem is being worked on and will be fixed in a later
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release.
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Credits
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The POP server was written by Edward Moy and Austin Shelton with
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contributions from Robert Campbell (U.C. Berkeley) and Viktor Dukhovni
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(Princeton University). Edward Moy wrote the HyperMail stack and drew
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the POP operation diagram. This installation guide was written by
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Austin Shelton.
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Footnotes
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[1] Copyright (c) 1990 Regents of the University of California.
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All rights reserved. The Berkeley software License Agreement
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specifies the terms and conditions for redistribution. Unix is
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a registered trademark of AT&T corporation. HyperCard and
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Macintosh are registered trademarks of Apple Corporation.
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[2] M. Rose, Post Office Protocol - Version 3. RFC 1081, NIC,
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November 1988.
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[3] M. Rose, Post Office Protocol - Version 3 Extended Service
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Offerings. RFC 1082, NIC, November 1988.
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