Wish list:
Things to do before the stable release:
make pre-release-check, HTML validator check.
Disable -DSNAPSHOT and -DNONPROD in makedefs.
Alias htable(3) calls to equivalent binhash(3) calls,
and obsolete the htable(3) module.
FILTER_README needs some text on multi-instance implementations,
and existing multi-instance references need to be updated.
Fix code that still uses "long" for data_size and data_offset,
and that uses "%ld" in sscanf().
A smart query service for live Postfix tables that outputs JSON?
Add a pointer to
http://mmogilvi.users.sourceforge.net/software/oauthbearer.html
in documentation or on-line howtos.
Read http://mmogilvi.users.sourceforge.net/software/oauthbearer.html
and see how we can improve on the Postfix side.
Add verp=+= to the qmgr "from=" logging. This is already
implemented but not yet integrated.
Need canonical Dovecot example that has virtual_mailbox_domains,
(virtual_mailbox_maps or reject unverified_recipient), and
virtual_transport.
Make smtpd_relay_before_recipient_restrictions settable
in smtpd_checks tests.
Make the DNS resolver library pluggable, so that we can a)
plug in a fake resolver library for DNS-related regression
tests and make DNS tests hermetic (no external dependency;
b) add support for non-libbind resolvers. Gracefully handle
requests for unsupported functionality; return an error status,
instead of terminating.
Add a robust dnssec_probe regression test (success and fail)
that does not break existing regression tests.
smtp_sasl_tls_security_options = noanonymous, and make
smtp_sasl_security_options the default dependent on the
smtp_sasl_tls_security_options default (i.e. reverse the
dependency). Or make them independent.
Try to make the master throttle more distrusting. Currently,
the master throttles a service after a child process cannot be
created (fork() fails), or if a child process fails upon its
first use. The master always unthrottles the service if a process
handles a client successfully. This is sufficient to mitigate
local errors that break all attempts to use a service. It also
slows down stupid remote attacks as long as malicious traffic
dominates benign traffic. Perhaps monitor a crashing percentage?
If 50% of all connections to a service result in abnormal
termination, that would be bad even under a non-attack scenario.
More accurate address verification: do a quota check before
reporting that a local(8) or virtual(8) recipient is deliverable.
Eliminate duplicate mail submission permission checks from
sendmail, so that they happen in postdrop only. Then, pass the
result through the postdrop-to-sendmail protocol. This requires
that postdrop reads all inputs before responding (the
local_login_sender_maps check depends on the envelope
sender). Then sendmail can save input to dead.letter (no setgid
privilege, but it would still have to use safe_open() to avoid
clobbering files).
Consider removing compat_level_from_numbers() and aliases,
because they are no longer used anywhere.
Allow '}' at the beginning of a line. This would make multi-line
configuration settings easier to enter. This may be true
for main.cf, master.cf and similar files (such as database
configuration files, but not necessarily elsewhere). So it
may have to be a readlline flag.
Understand what happens with DNSSEC related status fields
in posttls-finger when resolv.conf points to a host that
runs no DNS server.
Hardening the half-dane behavior: some sites may rely on
current behavior which allows original MX domain name for
certificate matches. Requires a new (compatibility) parameter
setting?
Code deduplication: migrate multi_server applications to
event_server, because the multi_server and event_server
skeletons are much more similar than other skeletons. In
addition to the default event_server accept() handler, also
register a read event callback for handling post_accept
events. But the currrent multi_server API fits typical usage
better.
When a secondary instance has no multi_instance_name set,
postmulti -i won't be able to find it.
nbbio: exercise the sanity checks with fake msg(3) functions.
optreset (bsd-ism) how badly do we need it?
transport policy protocol (clone of check_policy).
See also postscreen event-driven client for policy delegation
below.
smtp_line_length_limit can insert a line break in the middle
of a multi-byte character (which is not necessarily UTF-8,
so we can't simply look at the 8th bit). Also, note that a
multi-byte character may span queue file record boundaries,
for example if line_length_limit == smtp_line_length_limit.
The only way to fix this is to make the smtp_text_out()
routine aware of every possible multi-byte encoding.
Replace ad-hoc code for pipe(8) flags handling, with
infrastructure that was built for smtp(8).
Move map descriptions from postconf(1) to DATABASE_README
and point there. The text in DATABASE_README is less complete
than that in postconf(1).
make tls_pre_jail_init() safe by design for use in programs
that implement both clients and servers.
In smtpd(8) and postscreen(8), set the ehlo_discard_mask
to ~0 so that STARTTLS, BDAT, DSN, etc. work only for clients
that send EHLO.
Wordsmithing: "replace by X" -> "replace with X" unless X
is "responsible" for making the substitution.
In postscreen, don't fork after 'postfix reload' when
psc_check_queue_length (and psc_post_queue_length?) is zero.
After I/O error, store errno in VSTREAM object before errno
may be overwritten.
Add some tips for logging from container:
https://www.projectatomic.io/blog/2016/10/playing-with-docker-logging/;
syslog_name = $myhostname/postfix; mkdir queue and data
dir; postfix check to create queue subdirectories.
Add postwhite as a postscreen-related project.
https://github.com/stevejenkins/postwhite/blob/master/README.md
XFORWARD attributes in policy protocol?
Document postsrsd and postforward for srs-ifying. Would
more fine-grained smtp_generic_maps support help?
Decide whether to deprecate database configuration pathnames
that start with ".", for example, ldap:./file/name. These forms
are documented for ldap:, memcache:, mysql:, pgsql:, and sqlite:
maps. Postfix daemon processes will look up files relative to the
queue directory, but with postmap command-line processes it would
be more natural to interpret relative pathnames relative to the
current directory of the calling process (it would be a surprise
if "postmap hash:./foo" would access "/var/spool/postfix/foo",
or if "postmap hash:foo" and or "postmap hash:./foo" would access
different files).
Convert postalias(1) to store external-form keys, and convert
aliases(5) to perform external-first lookup with fallback to
internal form, to make it consistent with the rest of Postfix.
In several years we may remove the internal-form fallbacks
with a compatibility_level safety net.
In the bounce daemon, set util_utf8_enable if returning an
SMTPUTF8 message. This is wrong; if SMTPUTF8 is disabled,
then Postfix must not turn it on.
Add a header_body_checks extension callback in smtp_proto.c
that implements the PASS action.
Propagate SMTPD_PEER_CODE_XXX from smtpd(8) to cleanup(8),
so that {client_resolve} and {_} produce consistent results.
NO_IP_CYRUS_SASL_AUTH should be a main.cf parameter.
Modeline support in config files to enable/disable trailing
#comment, and to give hints about how to handle an LHS or
RHS. This will not preserve trailing comments in lines that
are modified with "postconf -e" and the like.
Maintainability: replace lengthy libmilter-API argument lists
with named parameters, as with the libtls API.
Fix buflen integer overflow detection in dict*sql.c.
Fix "make test" bitrot.
Move DNS-based tests from porcupine.org to postfix.org, or use
a mock DNS library (a library that presents the same API as the
real library, but that produces canned responses).
Document dns_ncache_ttl_fix_enable use case in POSTSCREEN_README
and RELEASE_NOTES.
Remove this file from the stable release.
Things to do after the stable release:
Specify WARN_UNUSED_RESULT for all library functions that
pass, deliver, bounce or defer a delivery request.
Invent some kind of type-checking wrappers for htable(3),
ctable(3) and other modules that take and return a void*
pointer. We already did that for variadic functions.
TLS certificate provenance: indicate whether a subject
name/issuer are verified or not (for example, change the
attribute name to unverified_ccert_subject etc.). This is
relevant only for fingerprint-based authentication including
DANE, and affects logging, SMTPD policy, and Milters.
Generalize the daemon '-S' stand-alone mode, so that it can
be used with custom configuration settings for request/reply
regression testing. This would use the existing "-o name=value"
support to override parameters. For example, queue_directory
would point to a directory with sockets for fake versions of
Postfix-internal services.
Update the list of Sendmail macros that Postfix can send
to Milters (auth_ssf and TLS-related).
Update smtpd command count when rejecting or skipping input
before command-table lookup. But then we need to count
commands that are rejected (malformed UTF-8, tokenizer
error, forbidden command), or skipped (noop).
What is the best place to detect spaces in pathnames during
installation/upgrade/packaging? postfix-install for early
warning, and post-install as a safety net?
When the service basename differs from the program file
basename, either prepend the service name to the syslogname (as
if syslog_name=postfix/service/program), or prepend the service
name to the process name (perhaps too confusing). The service
indication is desirable for mail delivery transports (smtp
versus relay) as it identifies what scheduler parameters are
in effect, but it is also desirable for mail receiving services
(smtp versus submission verus smtps as configured in the stock
master.cf file). This requires exceptions for some program names
(exclude smtpd to avoid logging postfix/smtp/smtpd which could
result in more confusion, and maybe other program names).
UTF8 DNS[BW]L domain name.
Consolidate maps flags in mail_params.h instead of having
multiple copies scattered across programs.
Try to allow UTF-8 myhostname/mydomain, at least in bounce
template expansion.
In the SMTP server, do not issue an enhanced status code when
rejecting a connection before the HELO handshake is completed.
Maybe don't whitelist a client that has maxed out its
per-MTA connection count limit.
Inline support for pcre:{/pattern/=action, ...} and ditto
support for regexp: and cidr: tables. Factor out and reuse
code that already exists in inline: and other tables.
Log command=good/bad statistics in postscreen?
smtpd_checks tests either must use a DNS dummy resolver
(override the res_search API) or all names must be under
test.postfix.org (but that does not work for address->name
lookups, and cannot simulate some errors).
Reporting the original Message-ID in a bounce message
In-Reply-To: or References: header. In the cleanup daemon,
grab a copy of the Message-ID and export it along with other
header-extracted information at the top of the "extracted"
queue file segment. In the queue manager, extract this
along with other header-extracted information, and forward
the Message-ID in the bounce server notification request.
Clobber ORCPT when sender is owner-mumble?
Add milter_mumble_macros to the list of per-macro features.
The pickup daemon logs warnings only when the cleanup daemon
dit not provide a "reason" attribute. Is this logic right?
up-convert myhostname to UTF-8 in MIME boundary strings?
Eliminate code duplication between pcf_print_master_field()
and pcf_print_master_entry().
Error reporting: see if pcf_check_master_entry() and children
can return error descriptions instead of terminating with
a fatal error.
Add a switch to consider postscreen deep protocol tests as
"completed" when receiving "RSET" after "RCPT TO" and the
session has passed all tests up to that point. RSET becomes
like QUIT except perhaps that it does not hang up.
apipe: map, splits results into address lists and performs
lookups for the invidual addresses, converting back and
forth between external and internal forms.
Clarify that receive_override_options have no effect with
smtpd_proxy_filter.
Document the relative order of header_checks, address
rewriting, milters.
NOT: Table-driven case folding and case-insensitive string
comparison specifically for UTF-8. Use libicu functions
instead.
When downgrading message/global to 7bit, is quoted-printable
the appropriate encoding? Should it be base64?
Should we encode headers with RFC 2047, when that is the
only reason that Postfix cannot deliver to a non-UTF8SMTP
server? Probably not in the general case. What about
Postfix as a gateway server that converts UTF8SMTP
for delivery to non-UTF8SMTP environments?
Document and test restriction_classes example for
smtpd_policy_service_default_action.
Don't accept AUTH or other features that are not announced
in the EHLO response.
Suggested at Mailserver conference: Postscreen RDNS-based
reputation (but this makes postscreen performance highly
unpredicable because it introduces a dependency on random
DNS servers).
Suggested at Mailserver conference: a way to select a
specific field in a table, presumably as the result value.
This may be done with a filtermap{i,j,...}: table that propagates
only the specified field(s).
Discourage the use of "after 220" tests in POSTSCREEN_README
and the documentation of individual parameter settings.
To un-break "make tests" under src/smtpd, make tests
independent from the DNS and native routines for host
name/address lookup.
Make been_here flag BH_FLAG_FOLD configurable for masochists.
Replace some redundant TLS_README sections with pointers
to FORWARD_SECRECY_README.
Move html/index.html source to proto/.
How hard is it to follow canonical or virtual mapping
for the purpose of address validation? We must never
reject a valid address.
Preserve case in smtpd_resolve_addr() and add a structure
member for the case-folded address. IIRC some Milter macro
needs to show the unfolded address.
Per SASL account rate limits. This requires new infrastructure
that maintains stats by SASL account instead of client IP
address.
Watchdog timer in postmap/postalias.
Begin code revision, after DANE support stabilizes. This
should be one pass that changes only names and no code.
recipient_delimiters = $recipient_delimiter for BC
All source code must specify its original author and
license statement. Some code modules specify Lutz Jaenicke
as the original author and fall under his liberal license.
Code that is added to such a module has the same license
(or at least something that is not more restrictive). Code
modules without input from Lutz Jaenicke must state its
original author and license (preferably no more restrictive
than Postfix's own license). Currently, too many files list
Wietse as the original author, and Lutz Jaenicke's license,
which is wrong.
We have smtp_host_lookup, smtp_dns_resolver_options, and
now smtp_dns_support_level. Of these, smtp_dns_resolver_options
is orthogonal but the rest has overlap.
There needs to be support for automatic migration from the
deprecated disable_dns_lookups feature to the preferred
smtp_dns_support_level feature. This support needs to exist
for several releases before the deprecated feature can be
removed.
End code revision, after DANE support stabilizes.
It would be nice if "bare username" lookup is not hard-coded
for domains in the local address class.
Don't forget Apple's code donation for fetching mail from
IMAP server.
Should postconf -o refuse to work without the -x option?
Make 30s caching (feature 20070414) configurable, such that
0 means no caching.
Make errno white/blacklist for getpwnam_r etc. and mailbox
write errors.
smtpd_muble_restrictions rule names are case-insensitive.
restriction_classes values are case-sensitive but should
be case-insensitive for consistency with smtpd_muble_restrictions.
Make "rename" the default when postmapping a DB file
(later: use copy+rename for postmap -i, postmap -d).
Service-name parameters aren't documented in daemon manpages.
When faking up the DSN ORCPT, don't send bare usernames
from local command-line submission.
lmtp_assume_final is broken. A 2XX response does not imply
final delivery. The Sieve language implements accept-then-bounce.
postscreen event-driven plug-in interface to send out a
query in parallel with the Pregreet and DNSBL tests, using
a simplified version of the policy delegation protocol.
Parallelized queue preprocessing: rip out the queue manager
code to read queue files and resolve recipients, and run
it in parallel processes. The queue manager then processes
their results as they become available. This would eliminate
the qmgr<->trivial-rewrite bottleneck. This can also eliminate
much of the scheduling disadvantage of a single queue manager
compared to hundreds of mail receiving or sending processes
(especially if there is a way to scan the queue in parallel).
Memory pools for same-type memory objects. This can be
used to either increase memory locality for frequently-allocated
objects (MRU allocation) or to make use-after-free bugs
more detectable (use LRU allocation and wipe the object
immediately after free(). Finally, same-type memory pools
prevent object type errors with use-after-free bugs.
"no-cache" option for selected postscreen tests?
Need a new DICT flag to indicate that a map handle supports
locking. If it doesn't (as with memcache or proxymap
handles), then postscreen etc. don't need to close a cache
file after "postfix reload". After a fork() it is OK to
keep using a memcache or proxymap handle, because the parent
exits immediately. For this to work, the memcache client
needs to propagate the flag from a persistent backup map,
but the proxymap protocol should not propagate this to the
client.
Different TTL values for different DNSBL sources?
Replace master(8) SIGHUP by very simple socket protocol to
allow reload of a specific service.
postscreen: in the dummy SMTP engine, log the protocol state
at time of violation (like smtpd, set state->where initially
to CONNECT, then update it with the name of the last "known"
command, or set it to "unimplemented").
The discussion of postscreen cache configuration is in the
wrong place (how whitelisting works). Move it to the section
about configuring postscreen.
Before proxymap can be exposed to the network (primarily
to share postscreen or verify caches), need to enforce
limits on attribute string name and value length in IPC
protocols. 10-20KB seems OK. We need to enforce content
sanity checks (for example, no control characters; Postfix
does not pass around multi-line data in table lookups). The
VSTREAM library already supports read/write deadlines. We
need to use attack-resistant code for numeric conversion.
move flush_init() etc. from defer service clients to the
bounce daemon? Postfix works best when work can be spread
out over many clients, instead of over a few servers.
multi_connect() function that takes a list of inet:host:port
and/or unix:pathname specs, with an explicit "inet" prefix
argument to handle applications that use host:port only.
This will simplify multi-host implementation for memcache
client, dovecot client, and other.
dict_memcache: treat "bad" key as cache miss, i.e. read/write
the backup database as if the cache did not exist. This
does not help because most Postfix maps (virtual, canonical,
access, transport, ...) also don't support spaces in keys.
postscreen: keep the cache open after "postfix reload" when
it is remote (type memcache: or proxy:). This does not work
because memcache can use a non-proxied file as backup).
What is the feasibility of adding an mta_name (personality)
attribute that is propagated via queue files and delivery
agent requests? It would default to myhostname.
Major performance improvement opportunity (that is until
everyone runs Postfix queues on SSDs). Investigate the
viability of a daemon that produces incoming and postdrop
queue files on request (in reality it would maintain a
limited queue of "spare" files). Central queue file allocation
reduces the I/O performance disadvantage that qmgr has when
100 smtpd processes are receiving mail, or when lots of
mail is submitted with the sendmail command line. When an
smtpd process accepts MAIL FROM, a cleanup daemon requests
a queue file and receives a queue ID + file handle from the
queue file daemon. If the queue file daemon is down, the
cleanup daemon creates the file itself like it does now;
this can be hidden in the mail_stream library module. If
the mail transaction is aborted, then the cleanup daemon
gives the queue file back to the queue file daemon's "spare"
file pool, saving most of the overhead of creating and
deleting a queue file (the file would still need to be
renamed at the start of the next mail transaction). If the
cleanup daemon is unable to give a file back, then it can
delete the file like it does now; this can be hidden in the
mail_stream library module. The whole thing can be
transparently added to Postfix by adding calls to a
queue-file-service client to the mail_queue_enter() and
mail_queue_remove() library routines. Other advantages:
1) negligible performance hit when queue file allocation
happens earlier, so that logging and milters have a queue
ID for the whole transaction not just the first valid
recipient; 2) by not removing every queue files we get most
of the performance gain of a queue based on append/truncate
instead of the much more expensive create/delete.
Investigate viability of Sendmail dns maps.
Make the rules for how to use close-on-exec more explicit.
Provide separate timeout control for dict_proxy client,
rewrite client, resolve client, cleanup client, and so on.
Perhaps a timeout argument to the mail_connect() routines.
Trick from amavisd: save listen socket/fifo/etc state, clear
their close-on-exec flags, exec the same program file to
re-initialize (with saved socket state on command line or
in environment), then restore the listen socket/fifo/etc
close-on-exec flags. This could be a way to mitigate the
impact of memory/file leaks, and to implement "postfix
reload" support for master(8) features that currently don't
support this.
Sub-second time resolution. The first benefit is to make
per-destination rate delays more usable. Other applications
will come up once the support exists. The straightforward
approach is to represent all time intervals in milliseconds,
and to update all code that makes system calls with a time
argument (as well as the compiled-in upper and lower time
parameter bounds, which are currently in seconds).
Unfortunately, that limits he maximum time interval to less
than 25 days on 32-bit systems, and is likely to break
compatibility (for starters, it cannot even deal with the
compiled-in 100d upper bound on the queue file lifetime).
A second option is to have a "compatibility" time base
switch between milliseconds and seconds; this means extra
changes to all code that makes system calls with a time
argument, and the way that the compiled-in upper and lower
bounds are specified. Some of this can be encapsulated in
macros like time_to_sec(t), time_to_msec(t) and sec_to_time(t).
Finally, it is relatively easy to replace the events(3)
interface to use "double" for the time delay arguments, but
it is a major pain to convert all main.cf time parameters
into doubles (converting only some leads to a documentation
nightmare).
Address verify cache: allow a negative cache "refresh"
result to purge a "positive" cache entry in some safe manner.
Currently, the negative cache "refresh" result is discarded,
address verify cache lookup returns OK, and each lookup
forces a "refresh" probe until the entry expires.
Some Sendmail configurations trigger sub-optimal behavior
when the postscreen_whitelist_interfaces parameter lists
primary MX addresses only. When postscreen's "deep protocol
tests" are successful on the primary MX address (i.e. they
result in 4XX responses to RCPT TO), some Sendmail
configurations keep the primary MX connection open until
AFTER they finish talking to the backup MX address. The
problem is that the backup connection runs into a WHITELIST
VETO condition because the whitelisting database has not
yet been updated with the PASS NEW result for the primary
MX connection. Unfortunately postscreen can't update the
whitelisting database before the primary MX connection is
closed, because a client may still make a mistake.
In the SMTP server, check if the connection is closed before
replying to ".", and discard the message if the reply can't
be sent. This reduces the time window for RFC 1047 message
duplication, and may even prevent the delivery of some spam.
http://www.exim.org/lurker/message/20070416.103159.9d5ff0ce.en.html
This requires splitting the SMTP server's commit operation
into two operations: first, a tentative commit operation
that performs most of the I/O and processing in milters and
in the cleanup server; second, a final commit operation
that is executed only if the remote SMTP client hasn't hung
up in the mean time. Unfortunately, SMTP-based before-queue
content filters don't support a tentative commit operation.
Find out how to reproduce Berkeley DB bogus ENOENT errors.
postscreen does not log this with Berkeley DB 1 (FreeBSD
4..8), 4.7.25 (Ubuntu 9.04) and 4.8.24 (Ubuntu 10.04).
postconf command-line option to show the compile-time
settings (CCARGS, AUXLIBS) in case binary packages
don't install the makedefs.out file.
events.c: cache the side effects of file descriptor event
enable/disable operations in user space, and do bulk kernel
updates at event_loop() time. This can eliminate costly
system calls with successive event disable/enable operations
on the same file descriptor. This can also eliminate the
need for tricky code that tries to avoid the expense of
successive disable/enable operations. Such code is likely
to introduce bugs.
When does it pay off to send domains in the active queue
to a DNS prefetch daemon? Could this generalize to a dynamic
transport map that piggy-backs domains with the same MX
host into the same mail delivery transaction?
tlsproxy(8) should receive TLS preferences from postscreen(8)
and smtpd(8), instead of reading them from main.cf. This
means that many tlsproxy_ parameters become postscreen_
parameters, and that tls_server_init() parameters move to
to tls_server_start(). That is a significant API change.
It also means tlsproxy can't open all files before chroot().
anvil rate limit for sasl_username.
Encapsulate nbbio buffer access and update by tlsproxy.
Full-duplex support for tlsproxy(8). This requires updating
events(3) and nbbio(3).
Register automagic destructor for object attached to VSTREAM.
Use different ipc time limits for email message transactions
(smtpd, pickup)->cleanup and for quick query/reply transactions
such as address rewriting/resolution. Beware of large time
limits for local or virtual alias expansion.
permit_tempfail_action (default: defer_if_reject) to be
used as the default value for dnswl_tempfail_action and
rhswl_tempfail_action. Steal liberally from the code that
implements unverified_recipient_tempfail_action etc.
Support filtering of messages that are generated by Postfix:
This would apply to postmaster notices and bounce messages
(DKIM), and address verification (BATV).
Consistency: in postconf.proto make .. tags bold.
Would it help if there were different cleanup_service
parameter names for different message paths? smtpd(8) uses
the same cleanup_service value for receiving remote mail
and for submitting postmaster problem reports. Do we need
separate mumble_cleanup_service_name parameters for "inject",
"notify" and "forward" (with backwards compatible defaults)?
IF/ENDIF support for CIDR tables.
Need a regular expression table to translate address
verification responses into hard/soft/accept reply codes.
Is there a way to make sendmail -V work after local alias
expansion? Majordomo-like mailing lists would benefit from
this; the example in VERP_README does not work in the general
case.
When an alias is a member of an :include: list with owner-
alias, local(8) needs an option to deliver alias or alias->user
indirectly. What happens when an :include: list with owner-
alias includes another list?
Don't allow empty result values in pcre and regexp maps.
Postfix doesn't allow them anywhere else (check this).
Make PCRE_MAX_CAPTURE configurable.
Add some checks for tokens starting with #. A challenge
is to report sensible context from the guts of some low-level
parser, without introducing a great deal of clumsiness.
Add sendmail macros for {verify} and maybe other TLS info.
Find out if we are doing the correct thing by looking at
state->milter_reject_text when expanding {rcpt_addr} or
{rcpt_host}.
Find out why post_mail() etc. block when the qmgr fifo is
full (answer: trigger_timeout). How can this cause delays
in the queue manager? When a recipient bounces during
(transport, nexthop, address) resolution, it is redirected
to the error or retry mailer; and bounce-after-delivery is
asynchrounous so it can't block the queue manager, either.
How to ensure that proxy_read_maps is processed after all
its dependencies are initialized, or just bite the bullet
and rewrite the parameter initialization code.
The cleanup virtual alias expansion limit does not really
deliver on its promises. 1) It promises to truncate the
result without aborting delivery, which would be undesirable
anyway, but that is not what it does, so that is good. 2)
It keeps all the recipients from multi-recipient database
lookup, then terminates further recursion when the result
exceeds the expansion limit. This behavior achieves the
original goal that all things shall have a finite size (even
though but we don'really care how large they are) but may
result in surprises when recipients are listed in virtual
alias domains or need expansion for other reasons. In a
phone call with Victor, a reasonable way out is to set the
limit to some large number (100000) and abort delivery when
the result exceeds the limit.
Should the postscreen save permanent white/black list lookup
results to the temporary cache, and query the temporary
cache first? Skipping white/black list lookups will speed
up the handling of "good" clients without a permanent
whitelist entry. Of course, this means that updates to the
white/black lists do not immediately take effect. Workarounds:
1) use a shorter temporary cache TTL for clients on the
permanent black/white lists; 2) ignore cached white/black
list lookup results after "postfix reload"; 2) adjust the
logging, for example "WHITELISTED address (cached)" and
"BLACKLISTED address (cached)" to eliminate surprises.
Comparing the cache entry time with the white/blacklist
file modification time is not foolproof: for example, pcre
or CIDR tables are read only once.
It would be nice if the generic dict_cache(3) cache manager
could postpone process suicide until cache cleanup is
completed (but that is not possible when postscreen forks
into the background to finish already-accepted connections,
and it is not desirable when a host is being shut down).
When postscreen drops a connection, a 521 "greeting" should
be of the form "521 servername..." and not have an enhanced
status code. The "521 5.7.1" form can be used after EHLO.
Of course no spammer is going to complain about Postfix
SMTP compliance.
Find a place to document all the mail routing mechanisms
in one place so people can figure out how Postfix works.
The access map BCC action is marked "not stable", perhaps
because people would also expect BCC actions in header/body_checks.
How much would it take to make the queue file editing code
generally usable?
Move smtpd_command_filter into smtpd_chat_query() and update
the session transcript (see smtp_chat_reply() for an example).
SMTP connection caching without storing connections, to
improve TLS mail delivery performance.
Should not milter8_mail_event() unset the "hold" default
reply? Better, the default reply should not be used for
this purpose.
Don't send MASTER_STAT_TAKEN/MASTER_STAT_AVAIL when a server
runs with process limit of 1. But this means the master
never learns that the process is successful and will always
pause $service_throttle_time before restarting a failed service.
Don't bother maintaining a per-service lockfile when a
server runs with process limit of 1. The purpose of the
lockfile is to avoid thundering herd problems when the kernel
wakes up multiple processes for each new client connection.
Implement PREPEND action for milter_header_checks. Save the
to-be-prepended text to buffer, then emit it along with the
new header.
Fix the header_body_checks API, so that the name of the map
class (e.g. milter_header_checks) is available for logging.
Fix the mime_state and header_body_checks APIs, so that
they use VSTRINGs. This simplifies REPLACE actions.
Update FILTER_README for multi-instance support, and rename
the old document to FILTER_LEGACY_README.
Need to sign delivery status notifications, to avoid surprises
when eventually people start enforcing DKIM etc. signatures.
Either document or remove the internal_mail_filter_classes
feature (it's disabled by default).
Make the "unknown recipient" test configurable as
first|last|never, with "yes"=="last" for backwards
compatibility. The "first" setting is good for performance
(stress=yes) when all users are defined in local files; but
it may perform worse when users are in networked tables.
Cleanup: make DNSBL query format configurable beyond the
client's reversed IP address.
With 'final delivery' in the LMTP client, need an option
to also add delivered-to and other pipe(8) features. This
requires making mail_copy() functionality available in
non-mailbox context.
Cleanup: modernize the "add missing From: header" code, to
``phrase '' form. Most likely, quote the entire phrase
if it contains any text that is special, then rfc822_externalize
the whole thing.
SMTP server: make the server_addr and server_port available
to policy server, Dovecot, and perhaps Milters.
Med: local and remote source port and IP address for smtpd
policy hook.
Maybe change maps_rbl_reject_code default to 521, and
update wording in STRESS_README.
Encapsulate time_t comparisons so that they can be made
system dependent (use difftime() where available).
Encapsulate time_t conversions (e.g. REC_TYPE_TIME) so that
they can be made system dependent.
Plan for time_t larger than long, or wait for LP64 to
dominate the world?
Make "AUTH=<>" appendage to MAIL FROM configurable, enabled
by default.
To support ternary operator without a huge parsing effort,
consider ${value?{xxx}:{yyy}} where ${name} is existing
syntax, and where ?{text} and :{text} are new syntax that
is unlikely to break existing configurations. Or perhaps
it's just too ugly.
Write delivery rate delay example (which _README?) and auth
failure cache example (SASL_README). Then include them in
SOHO_README.
Look for alternatives for the use of non_smtpd_milters.
This involves some way to force local submissions to go
through a local SMTP client and server, without triggering
"mail loops back to myself" false alarms. The advantage is
that it makes smtpd_mumble_restrictions available for local
and remote mail; the disadvantage is that it makes local
submissions more dependent on networking. One possibility
is to use "pickup -o content_filter=smtp:127.0.0.1:10025",
or a dedicated SMTP client/server on UNIX-domain sockets;
we could also decide to always suppress "mail loop" detection
for loopback connections. Another option is to have the
pickup or cleanup server drive an SMTP client directly;
this would require extension of the mail_stream() interface,
plus a way to handle bounced/deferred recipients intelligently,
but it would be at odds with Postfix design where delivery
agents access queue files directly; exposing delivery agents
to raw queue files violates another Postfix design principle.
Consolidate duplicated code in *_server_accept_{pass,inet}().
Consolidate duplicated code in {inet,unix,upass}_trigger.c.
In the SMTP client, handle 421 replies in smtp_loop() by
having the input function raise a flag after detecting 421
(kill connection caching and be sure to do the right thing
with RSET probes), leave the smtp_loop() per-command reply
handlers unchanged, and have the smtp_loop() reader loop
bail out with smtp_site_fail("server disconnected after
%s", where), but only in the case that it isn't already in
the final state. But first we need to clean up the handling
of do/don't cache, expired, bad and dead sessions.
Combine smtpd_peer.c and qmqpd_peer.c into a single function
that produces a client context object, and provide attribute
print/scan routines that pass these client context objects
around. With this, we no longer have to update multiple
pieces of code when a client attribute is added. Ditto for
SASL and TLS context.
Don't log "warning: XXXXX: undeliverable postmaster
notification discarded" for spam from outside.
Really need a cleanup driver that allows testing against
Milter applications instead of synthetic events. This would
have to provide stubs for clients that talk to Postfix
daemon processes. See if this approach can also be used for
other daemons.
smtpd(8) exempts $address_verify_sender from access controls,
but it doesn't know whether cleanup(8) or delivery agents
modify the sender. Would it be possible to "calibrate" this
exemption, perhaps by having delivery agents pass the probe
sender to the verify server, keeping in mind that the probe
sender may differ per delivery agent due to output rewriting.
Update attr_print/scan() so they can send/receive file
descriptors. This simplifies kludgy code in many daemons.
Would there be a problem adding $smtpd_mumble_restrictions
and $smtpd_sender_login_maps to the default proxy_read_maps
settings?
Remove defer(8) and trace(8) references and man pages. These
are services not program names. On the other hand we have
man pages for lmtp(8) and smtp(8), but not for relay(8).
Likewise, retry(8) does not have a man page.
Bind all deliveries to the same local delivery process,
making Postfix perform as poorly as monolithic mailers, but
giving a possibility to eliminate duplicate deliveries.
Maybe declare loop when resolve_local(mxhost) is true?
Update message content length when adding/removing headers.
Need scache size limit.
REDIRECT should override original recipient info, and
probably override DSN as well.
Update FILTER_README with mailing list suggestions to tag
with a badness indicator and then filter down-stream.
Make null local-part handling configurable: either expand
into mailer-daemon (current behavior) or disallow (strict
behavior, currently implemented only in the SMTP server).
Add M flag (enable multi-recipient delivery) to pipe daemon.
The usage of TLScontext->cache_type is unclear. It specifies
a TLS session cache type (smtpd, smtp, or lmtp), but it is
sometimes used as an indicator that TLS session caching is
unavailable. In reality, that decision is made by not
registering call-back functions for cache maintenance.
Postfix TLS library code should copy any strings that it
receives from the application, instead of passing them
around as pointers. TLScontext->cache_type is a case in
point.
Are transport:nexthop null fields the same as in the case
of default_transport etc. parameters?
Don't lose bits when converting st_dev into maildir file
name. It's 64 bits on Linux. Found with the BEAM source
code analyzer. Is this really a problem, or are they just
using 64 bits for upwards compatibility with LP64 systems?
Do or don't introduce unknown_reverse_client_reject_code.
Check that "UINT32 == unsigned int" choice is ok (i.e. LP64
UNIX).
Tempfail when a Milter application tries to negotiate content
access, while it is configured in an SMTP server that runs
before the smtpd_proxy filter.
Log DSN original recipient when rejecting mail.
Keep whitespace between label and ":"?
Make the map case folding/locking options configurable, if
not at run-time then at least at compile time so we get
consistent behavior across applications.
Investigate what it would take to eliminate oqmgr, and to
make the old behavior configurable in a unified queue
manager. This would shave another 2.7 KLOC from the source
footprint.
Document the case folding strategy for match_list like
features.
Eliminate the (incoming,deferred)->active rename operation.
This requires an in-memory hash of queue file names to avoid
duplicate open() operations.
Softbounce fallback-to-ISP for SOHO users. This heuristic
assumes that when direct-to-MX delivery fails with 5XX,
delivery via the ISP may still succeed. This could be
implemented by enabling soft bounces for destinations other
than the smtp_fallback_relay. So the only benefit of this
over the existing soft_bounce feature is that it has no
effect on smtp_fallback_relay deliveries.
Centralize main.cf parameter input so that defaults work
consistently. What about parameter names that are prefixed
with mail delivery transport names?
Fix default time unit handling so that we can have a default
bounce lifetime of $maximal_queue_lifetime, without causing
panics when a non-default maximal_queue_lifetime setting
includes no time unit.
After the 20051222 ISASCII paranoia, lowercase() lowercases
ASCII text only.
Privacy: remove local command/pathname details from remote
delivery status reports, and log them via local msg_warn().
Is it safe to cache a connection after it has been used for
more than some number of address verification probes?
Try to recognize that Resent- headers appear in blocks,
newest block first. But don't break on incorrect header
block organization.
Hard limits on cache sizes (anvil, specifically).
Laptop friendliness: make the qmgr remember when the next
deferred queue scan needs to be done, and have the pickup
server stat() the maildrop directory before searching it.
Low: replace_sender/replace_recipient actions in access
maps, so they can be used in policy servers?
Low: configurable order of local(8) delivery methods.
Med: smtp_connect_timeout_budget (default: 3x smtp_connect_timeout)
to limit the total time spent trying to connect.
Med: transform IPv4-in-IPv6 address literals to IPv4 form
when comparing against local IP addresses?
Med: transform IPv4-in-IPv6 address literals to IPv4 form
when eliminating MX mailer loops?
Med: Postfix requires [] around IPv6 address information
in match lists such as mynetworks, debug_peer_list etc.,
but the [] must not be specified in access(5) maps. Other
places don't care. For now, this gotcha is documented in
IPV6_README and in postconf(5) with each feature that may
use IPv6 address information. The general recommendation
is not to use [] unless absolutely necessary.
Med: the partial address matching of IPv6 addresses in
access(5) maps is a bit lame: it repeatedly truncates the
last ":octetpair" from the printable address representation
until a match is found or until truncation is no longer
possible. Since one or more ":" are usually omitted from
the printable IPv6 address representation, this does not
really try all the possibilities that one might expect to
be tried. For now, this gotcha is documented in access(5).
Low: reject HELO with any domain name or IP address that
this MTA is the final destination for.
Low: should the Delivered-To: test in local(8) be configurable?
Low: make mail_addr_find() lookup configurable.
Low: update events.c so that 1-second timer requests do not
suffer from rounding errors. This is needed for 1-second
SMTP session caching time limits. A 1-second interval would
become arbitrarily short when an event is scheduled just
before the current second rolls over.
Low: configurable internal/system locking method.
Low: add INSTALL section for pre-existing Postfix systems.
Low: add INSTALL section for pre-existing RPM Postfixes.
Low: disallow smtpd_recipient_limit < 100 (the RFC minimum).
Low: noise filter: allow smtp(8) to retry immediately if
all MXes return a quick ECONNRESET or 4xx reply during the
initial handshake. Retry once? How many times?
Low: make post-install a "postfix-only script" so it can
take data from the environment instead of main.cf.
Low: randomize deferred mail backoff.
Med: separate ulimit for delivery to command?
Med: postsuper -r should do something with recipients in
bounce logfiles, to make sure the sender will be notified.
To be perfectly safe, no process other than the queue manager
should move a queue file away from the active queue.
This could involve tagging a queue file, and use up another
permission bit (postsuper tags a "hot" file, qmgr requeues it).
Low: postsuper re-run after renaming files, but only a
limited number of times.
Low: smtp-source may block when sending large test messages.
Med: find a way to log the sender address when MAIL FROM
is rejected due to lack of disk space.
Low: revise other local delivery agent duplicate filters.
Low: all table lookups should consistently use internalized
(unquoted) or externalized (quoted) forms as lookup keys.
smtpd, qmgr, local, etc. use unquoted address forms as keys.
cleanup uses quoted forms.
Low: have a configurable list of errno values for mailbox
or maildir delivery that result in deferral rather than
bouncing mail. What about "killed by signal" exits?
Low: after reorganizing configuration parameters, add flags
to all parameters whose value can be read from file.
Medium: need in-process caching for map lookups. LDAP servers
seem to need this in particular. Need a way to expire cached
results that are too old.
Low: generic showq protocol, to allow for more intelligent
processing than just mailq. Maybe marry this with postsuper.
Low: default domain for appending to unqualified recipients,
so that unqualified names can be delivered locally.
Low: The $process_id_directory setting is not used anywhere
in Postfix. Problem reported by Michael Smith, texas.net.
This should be documented, or better, the code should warn
about attempts to set read-only parameters.
Low: while converting 8bit text to quoted-printable, perhaps
use =46rom to avoid having to produce >From when delivering
to mailbox.
virtual_mailbox_path expression like forward_path, so that
people can specify prefix and suffix.