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diff --git a/WISHLIST b/WISHLIST new file mode 100644 index 0000000..d0a0db4 --- /dev/null +++ b/WISHLIST @@ -0,0 +1,1140 @@ +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 <dt>..</dt> 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 <addr>'' 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. |