468 lines
18 KiB
Plaintext
468 lines
18 KiB
Plaintext
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SENDMAIL RELEASE 8
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This directory has the latest sendmail(TM) software from Sendmail, Inc.
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Report any bugs to sendmail-bugs-YYYY@support.sendmail.org
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where YYYY is the current year, e.g., 2005.
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There is a web site at http://www.sendmail.org/ -- see that site for
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the latest updates.
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+--------------+
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| INTRODUCTION |
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+--------------+
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0. The vast majority of queries about sendmail are answered in the
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README files noted below.
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1. Read this README file, especially this introduction, and the DIRECTORY
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PERMISSIONS sections.
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2. Read the INSTALL file in this directory.
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3. Read sendmail/README, especially:
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a. the introduction
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b. the BUILDING SENDMAIL section
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c. the relevant part(s) of the OPERATING SYSTEM AND COMPILE QUIRKS section
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You may also find these useful:
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d. sendmail/SECURITY
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e. devtools/README
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f. devtools/Site/README
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g. libmilter/README
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h. mail.local/README
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i. smrsh/README
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4. Read cf/README.
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Sendmail is a trademark of Sendmail, Inc.
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+-----------------------+
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| DIRECTORY PERMISSIONS |
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+-----------------------+
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Sendmail often gets blamed for many problems that are actually the
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result of other problems, such as overly permissive modes on directories.
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For this reason, sendmail checks the modes on system directories and
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files to determine if they can be trusted. For sendmail to run without
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complaining, you MUST execute the following command:
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chmod go-w / /etc /etc/mail /usr /var /var/spool /var/spool/mqueue
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chown root / /etc /etc/mail /usr /var /var/spool /var/spool/mqueue
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You will probably have to tweak this for your environment (for example,
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some systems put the spool directory into /usr/spool instead of
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/var/spool). If you set the RunAsUser option in your sendmail.cf, the
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/var/spool/mqueue directory will have to be owned by the RunAsUser user.
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As a general rule, after you have compiled sendmail, run the command
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sendmail -v -bi
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to initialize the alias database. If it gives messages such as
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WARNING: writable directory /etc
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WARNING: writable directory /var/spool/mqueue
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then the directories listed have inappropriate write permissions and
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should be secured to avoid various possible security attacks.
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Beginning with sendmail 8.9, these checks have become more strict to
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prevent users from being able to access files they would normally not
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be able to read. In particular, .forward and :include: files in unsafe
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directory paths (directory paths which are group or world writable) will
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no longer be allowed. This would mean that if user joe's home directory
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was writable by group staff, sendmail would not use his .forward file.
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This behavior can be altered, at the expense of system security, by
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setting the DontBlameSendmail option. For example, to allow .forward
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files in group writable directories:
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O DontBlameSendmail=forwardfileingroupwritabledirpath
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Or to allow them in both group and world writable directories:
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O DontBlameSendmail=forwardfileinunsafedirpath
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Items from these unsafe .forward and :include: files will be marked
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as unsafe addresses -- the items can not be deliveries to files or
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programs. This behavior can also be altered via DontBlameSendmail:
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O DontBlameSendmail=forwardfileinunsafedirpath,
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forwardfileinunsafedirpathsafe
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The first flag allows the .forward file to be read, the second allows
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the items in the file to be marked as safe for file and program
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delivery.
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Other files affected by this strengthened security include class
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files (i.e., Fw /etc/mail/local-host-names), persistent host status files,
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and the files specified by the ErrorHeader and HelpFile options. Similar
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DontBlameSendmail flags are available for the class, ErrorHeader, and
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HelpFile files.
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If you have an unsafe configuration of .forward and :include:
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files, you can make it safe by finding all such files, and doing
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a "chmod go-w $FILE" on each. Also, do a "chmod go-w $DIR" for
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each directory in the file's path.
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+--------------------------+
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| FILE AND MAP PERMISSIONS |
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+--------------------------+
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Any application which uses either flock() or fcntl() style locking or
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other APIs that use one of these locking methods (such as open() with
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O_EXLOCK and O_SHLOCK) on files readable by other local untrusted users
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may be susceptible to local denial of service attacks.
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File locking is used throughout sendmail for a variety of files
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including aliases, maps, statistics, and the pid file. Any user who
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can open one of these files can prevent sendmail or it's associated
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utilities, e.g., makemap or newaliases, from operating properly. This
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can also affect sendmail's ability to update status files such as
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statistics files. For system which use flock() for file locking, a
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user's ability to obtain an exclusive lock prevents other sendmail
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processes from reading certain files such as alias or map databases.
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A workaround for this problem is to protect all sendmail files such
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that they can't be opened by untrusted users. As long as users can
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not open a file, they can not lock it. Since queue files should
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already have restricted permissions, the only files that need
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adjustment are alias, map, statistics, and pid files. These files
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should be owned by root or the trusted user specified in the
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TrustedUser option. Changing the permissions to be only readable and
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writable by that user is sufficient to avoid the denial of service.
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For example, depending on the paths you use, these commands would be
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used:
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chmod 0640 /etc/mail/aliases /etc/mail/aliases.{db,pag,dir}
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chmod 0640 /etc/mail/*.{db,pag,dir}
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chmod 0640 /etc/mail/statistics /var/log/sendmail.st
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chmod 0600 /var/run/sendmail.pid /etc/mail/sendmail.pid
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If the permissions 0640 are used, be sure that only trusted users belong
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to the group assigned to those files. Otherwise, files should not even
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be group readable. As of sendmail 8.12.4, the permissions shown above
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are the default permissions for newly created files.
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Note that the denial of service on the plain text aliases file
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(/etc/mail/aliases) only prevents newaliases from rebuilding the
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aliases file. The same is true for the database files on systems which
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use fcntl() style locking. Since it does not interfere with normal
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operations, sites may chose to leave these files readable. Also, it is
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not necessary to protect the text files associated with map databases
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as makemap does not lock those files.
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+-----------------------+
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| RELATED DOCUMENTATION |
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+-----------------------+
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There are other files you should read. Rooted in this directory are:
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FAQ
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The FAQ (frequently answered questions) is no longer maintained
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with the sendmail release. It is available at
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http://www.sendmail.org/faq/ . The file FAQ is a reminder of
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this and a pointer to the web page.
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INSTALL
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Installation instructions for building and installing sendmail.
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KNOWNBUGS
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Known bugs in the current release.
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RELEASE_NOTES
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A detailed description of the changes in each version. This
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is quite long, but informative.
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sendmail/README
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Details on compiling and installing sendmail.
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cf/README
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Details on configuring sendmail.
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doc/op/op.me
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The sendmail Installation & Operations Guide. In addition
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to the shipped PostScript version, plain text and PDF versions
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can be generating using (assuming the required conversion software
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is installed on your system, see doc/op/Makefile):
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cd doc/op && make op.txt op.pdf
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Be warned: on some systems calling make in doc/op/ will cause
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errors due to nroff/groff problems. Known problems are:
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- running this off on systems with an old version of -me, you
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need to add the following macro to the macros:
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.de sm
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\s-1\\$1\\s0\\$2
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..
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This sets a word in a smaller pointsize.
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- with new groff versions (1.18 seems affected)
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GROFF_NO_SGR=1
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needs to be set, e.g., in doc/op/Makefile:
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ROFF_CMD= GROFF_NO_SGR=1 groff
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+--------------+
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| RELATED RFCS |
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+--------------+
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There are several related RFCs that you may wish to read -- they are
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available via anonymous FTP to several sites. For a list of the
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primary repositories see:
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http://www.isi.edu/in-notes/rfc-retrieval.txt
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They are also online at:
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http://www.ietf.org/
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They can also be retrieved via electronic mail by sending
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email to one of:
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mail-server@nisc.sri.com
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Put "send rfcNNN" in message body
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nis-info@nis.nsf.net
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Put "send RFCnnn.TXT-1" in message body
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sendrfc@jvnc.net
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Put "RFCnnn" as Subject: line
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For further instructions see:
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http://www.isi.edu/in-notes/rfc-editor/rfc-info
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Important RFCs for electronic mail are:
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RFC821 SMTP protocol
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RFC822 Mail header format
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RFC974 MX routing
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RFC976 UUCP mail format
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RFC1123 Host requirements (modifies 821, 822, and 974)
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RFC1344 Implications of MIME for Internet Mail Gateways
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RFC1413 Identification server
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RFC1428 Transition of Internet Mail from Just-Send-8 to
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8-bit SMTP/MIME
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RFC1652 SMTP Service Extension for 8bit-MIMEtransport
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RFC1869 SMTP Service Extensions (ESMTP spec)
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RFC1870 SMTP Service Extension for Message Size Declaration
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RFC1891 SMTP Service Extension for Delivery Status Notifications
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RFC1892 Multipart/Report Content Type for the Reporting of
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Mail System Administrative Messages
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RFC1893 Enhanced Mail System Status Codes
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RFC1894 An Extensible Message Format for Delivery Status
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Notifications
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RFC1985 SMTP Service Extension for Remote Message Queue Starting
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RFC2033 Local Mail Transfer Protocol (LMTP)
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RFC2034 SMTP Service Extension for Returning Enhanced Error Codes
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RFC2045 Multipurpose Internet Mail Extensions (MIME) Part One:
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Format of Internet Message Bodies
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RFC2476 Message Submission
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RFC2487 SMTP Service Extension for Secure SMTP over TLS
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RFC2554 SMTP Service Extension for Authentication
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RFC2821 Simple Mail Transfer Protocol
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RFC2822 Internet Message Format
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RFC2852 Deliver By SMTP Service Extension
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RFC2920 SMTP Service Extension for Command Pipelining
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Other standards that may be of interest (but which are less directly
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relevant to sendmail) are:
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RFC987 Mapping between RFC822 and X.400
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RFC1049 Content-Type header field (extension to RFC822)
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Warning to AIX users: this version of sendmail does not implement
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MB, MR, or MG DNS resource records, as defined (as experiments) in
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RFC1035.
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+---------+
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| WARNING |
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+---------+
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Since sendmail 8.11 and later includes hooks to cryptography, the
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following information from OpenSSL applies to sendmail as well.
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PLEASE REMEMBER THAT EXPORT/IMPORT AND/OR USE OF STRONG CRYPTOGRAPHY
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SOFTWARE, PROVIDING CRYPTOGRAPHY HOOKS OR EVEN JUST COMMUNICATING
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TECHNICAL DETAILS ABOUT CRYPTOGRAPHY SOFTWARE IS ILLEGAL IN SOME
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PARTS OF THE WORLD. SO, WHEN YOU IMPORT THIS PACKAGE TO YOUR
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COUNTRY, RE-DISTRIBUTE IT FROM THERE OR EVEN JUST EMAIL TECHNICAL
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SUGGESTIONS OR EVEN SOURCE PATCHES TO THE AUTHOR OR OTHER PEOPLE
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YOU ARE STRONGLY ADVISED TO PAY CLOSE ATTENTION TO ANY EXPORT/IMPORT
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AND/OR USE LAWS WHICH APPLY TO YOU. THE AUTHORS ARE NOT LIABLE FOR
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ANY VIOLATIONS YOU MAKE HERE. SO BE CAREFUL, IT IS YOUR RESPONSIBILITY.
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If you use OpenSSL then make sure you read their README file which
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contains information about patents etc.
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+-------------------+
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| DATABASE ROUTINES |
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+-------------------+
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IF YOU WANT TO RUN THE NEW BERKELEY DB SOFTWARE: **** DO NOT ****
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use the version that was on the Net2 tape -- it has a number of
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nefarious bugs that were bad enough when I got them; you shouldn't have
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to go through the same thing. Instead, get a new version via the web at
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http://www.sleepycat.com/. This software is highly recommended; it gets
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rid of several stupid limits, it's much faster, and the interface is
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nicer to animals and plants. If the Berkeley DB include files
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are installed in a location other than those which your compiler searches,
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you will need to provide that directory when building:
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Build -I/path/to/include/directory
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If you are using Berkeley DB versions 1.85 or 1.86, you are *strongly*
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urged to upgrade to DB version 2 or later, available from
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http://www.sleepycat.com/. Berkeley DB versions 1.85 and 1.86 are known to
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be broken in various nasty ways (see http://www.sleepycat.com/db.185.html),
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and can cause sendmail to dump core. In addition, the newest versions of
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gcc and the Solaris compilers perform optimizations in those versions that
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may cause fairly random core dumps.
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If you have no choice but to use Berkeley DB 1.85 or 1.86, and you are
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using both Berkeley DB and files in the UNIX ndbm format, remove ndbm.h
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and ndbm.o from the DB library after building it. You should also apply
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all of the patches for DB 1.85 and 1.86 found at the Sleepycat web site
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(see http://www.sleepycat.com/db.185.html), as they fix some of the known
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problems.
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If you are using a version of Berkeley DB 2 previous to 2.3.15, and you
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are using both Berkeley DB and files in the UNIX ndbm format, remove dbm.o
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from the DB library after building it. No other changes are necessary.
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If you are using Berkeley DB version 2.3.15 or greater, no changes are
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necessary.
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The underlying database file formats changed between Berkeley DB versions
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1.85 and 1.86, again between DB 1.86 and version 2.0, and finally between
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DB 2.X and 3.X. If you are upgrading from one of those versions, you must
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recreate your database file(s). Do this by rebuilding all maps with
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makemap and rebuilding the alias file with newaliases.
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+--------------------+
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| HOST NAME SERVICES |
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+--------------------+
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If you are using NIS or /etc/hosts, it is critical that you
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list the long (fully qualified) name somewhere (preferably first) in
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the /etc/hosts file used to build the NIS database. For example, the
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line should read
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128.32.149.68 mastodon.CS.Berkeley.EDU mastodon
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**** NOT ****
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128.32.149.68 mastodon
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If you do not include the long name, sendmail will complain loudly
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about ``unable to qualify my own domain name (mastodon) -- using
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short name'' and conclude that your canonical name is the short
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version and use that in messages. The name "mastodon" doesn't mean
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much outside of Berkeley, and so this creates incorrect and unreplyable
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messages.
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+-------------+
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| USE WITH MH |
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+-------------+
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This version of sendmail notices and reports certain kinds of SMTP
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protocol violations that were ignored by older versions. If you
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are running MH you may wish to install the patch in contrib/mh.patch
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that will prevent these warning reports. This patch also works
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with the old version of sendmail, so it's safe to go ahead and
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install it.
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+----------------+
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| USE WITH IDENT |
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+----------------+
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Sendmail 8 supports the IDENT protocol, as defined by RFC 1413.
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Note that the RFC states a client should wait at least 30 seconds
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for a response. As of 8.10.0, the default Timeout.ident is 5 seconds
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as many sites have adopted the practice of dropping IDENT queries.
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This has lead to delays processing mail.
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No ident server is included with this distribution. It is available
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from:
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ftp://ftp.lysator.liu.se/pub/ident/servers/
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http://sf.www.lysator.liu.se/~pen/pidentd/
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+-------------------------+
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| INTEROPERATION PROBLEMS |
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+-------------------------+
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Microsoft Exchange Server 5.0
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We have had a report that ``about 7% of messages from Sendmail
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to Exchange were not being delivered with status messages of
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"connection reset" and "I/O error".'' Upgrading Exchange from
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Version 5.0 to Version 5.5 Service Pack 2 solved this problem.
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CommuniGate Pro
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CommuniGate Pro 3.2.4 does not accept the AUTH= -parameter on
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the MAIL FROM command if the client is not authenticated. Use
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define(`confAUTH_OPTIONS', `A')
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in .mc file if you have compiled sendmail with Cyrus SASL
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and you communicate with CommuniGate Pro servers.
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+---------------------+
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| DIRECTORY STRUCTURE |
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+---------------------+
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The structure of this directory tree is:
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cf Source for sendmail configuration files. These are
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different than what you've seen before. They are a
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fairly dramatic rewrite, requiring the new sendmail
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(since they use new features).
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contrib Some contributed tools to help with sendmail. THESE
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ARE NOT SUPPORTED by sendmail -- contact the original
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authors if you have problems. (This directory is not
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on the 4.4BSD tape.)
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devtools Build environment. See devtools/README.
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doc Documentation. If you are getting source, read
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op.me -- it's long, but worth it.
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editmap A program to edit and query maps that have been created
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with makemap, e.g., adding and deleting entries.
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include Include files used by multiple programs in the distribution.
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libsmdb sendmail database library with support for Berkeley DB 1.X,
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Berkeley DB 2.X, Berkeley DB 3.X, and NDBM.
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libsmutil sendmail utility library with functions used by different
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programs.
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mail.local The source for the local delivery agent used for 4.4BSD.
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THIS IS NOT PART OF SENDMAIL! and may not compile
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everywhere, since it depends on some 4.4-isms. Warning:
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it does mailbox locking differently than other systems.
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mailstats Statistics printing program.
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makemap A program that creates the keyed maps used by the $( ... $)
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construct in sendmail. It is primitive but effective.
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It takes a very simple input format, so you will probably
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expect to preprocess must human-convenient formats
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using sed scripts before this program will like them.
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But it should be functionally complete.
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praliases A program to print the DBM or NEWDB version of the
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aliases file.
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rmail Source for rmail(8). This is used as a delivery
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agent for for UUCP, and could presumably be used by
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other non-socket oriented mailers. Older versions of
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rmail are probably deficient. RMAIL IS NOT PART OF
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SENDMAIL!!! The 4.4BSD source is included for you to
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look at or try to port to your system. There is no
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guarantee it will even compile on your operating system.
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smrsh The "sendmail restricted shell", which can be used as
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a replacement for /bin/sh in the prog mailer to provide
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increased security control. NOT PART OF SENDMAIL!
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sendmail Source for the sendmail program itself.
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test Some test scripts (currently only for compilation aids).
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vacation Source for the vacation program. NOT PART OF SENDMAIL!
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$Revision: 8.93 $, Last updated $Date: 2005/09/16 20:08:50 $
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