Log Message:
mail/dovecot: update to 2.3.15

Security release.

v2.3.15 2021-06-21  Aki Tuomi <aki.tuomi@open-xchange.com>

* CVE-2021-29157: Dovecot does not correctly escape kid and azp fields in
  JWT tokens. This may be used to supply attacker controlled keys to
  validate tokens, if attacker has local access.
* CVE-2021-33515: On-path attacker could have injected plaintext commands
  before STARTTLS negotiation that would be executed after STARTTLS
  finished with the client.
* Disconnection log messages are now more standardized across services.
  They also always now start with "Disconnected" prefix.
* Dovecot now depends on libsystemd for systemd integration.
* Removed support for Lua 5.2. Use version 5.1 or 5.3 instead.
* config: Some settings are now marked as "hidden". It's discouraged to
  change these settings. They will no longer be visible in doveconf
  output, except if they have been changed or if doveconf -s parameter
  is used. See https://doc.dovecot.org/settings/advanced/ for details.
* imap-compress: Compression level is now algorithm specific.
  See https://doc.dovecot.org/settings/plugin/compress-plugin/
* indexer-worker: Convert "Indexed" info logs to an event named
  "indexer_worker_indexing_finished". See
  \ 
https://doc.dovecot.org/admin_manual/list_of_events/#indexer-worker-indexing-finished
+ Add TSLv1.3 support to min_protocols.
+ Allow configuring ssl_cipher_suites. (for TLSv1.3+)
+ acl: Add acl_ignore_namespace setting which allows to entirely ignore
  ACLs for the listed namespaces.
+ imap: Support official RFC8970 preview/snippet syntax. Old methods of
  retrieving preview information via IMAP commands ("SNIPPET and PREVIEW
  with explicit algorithm selection") have been deprecated.
+ imapc: Support INDEXPVT for imapc storage to enable private
  message flags for cluster wide shared mailboxes.
+ lib-storage: Add new events: mail_opened, mail_expunge_requested,
  mail_expunged, mail_cache_lookup_finished. See
  https://doc.dovecot.org/admin_manual/list_of_events/#mail
+ zlib, imap-compression, fs-compress: Support compression levels that
  the algorithm supports. Before, we would allow hardcoded value between
  1 to 9 and would default to 6. Now we allow using per-algorithm value
  range and default to whatever default the algorithm specifies.
- *-login: Commands pipelined together with and just after the authenticate
  command cause these commands to be executed twice. This applies to all
  protocols that involve user login, which currently comprises of imap,
  pop3, submisision and managesieve.
- *-login: Processes are supposed to disconnect the oldest non-logged in
  connection when process_limit was reached. This didn't actually happen
  with the default "high-security mode" (with service_count=1) where each
  connection is handled by a separate process.
- *-login: When login process reaches client/process limits, oldest
  client connections are disconnected. If one of these was still doing
  anvil lookup, this caused a crash. This could happen only if the login
  process limits were very low or if the server was overloaded.
- Fixed building with link time optimizations (-flto).
- auth: Userdb iteration with passwd driver does not always return all
  users with some nss drivers.
- dsync: Shared INBOX not synced when "mail_shared_explicit_inbox" was
  disabled. If a user has a shared mailbox which is another user's INBOX,
  dsync didn't include the mailbox in syncing unless explicit naming is
  enabled with "mail_shared_explicit_inbox" set to "yes".
- dsync: Shared namespaces were not synced with "-n" flag.
- dsync: Syncing shared INBOX failed if mail_attribute_dict was not set.
  If a user has a shared mailbox that is another user's INBOX, dsync
  failed to export the mailbox if mail attributes are disabled.
- fts-solr, fts-tika: Using both Solr FTS and Tika may have caused HTTP
  requests to assert-crash: Panic: file http-client-request.c: line 1232
  (http_client_request_send_more): assertion failed: (req->payload_input != NULL)
- fts-tika: 5xx errors returned by Tika server as indexing failures.
  However, Tika can return 5xx for some attachments every time.
  So the 5xx error should be retried once, but treated as success if it
  happens on the retry as well. v2.3 regression.
- fts-tika: v2.3.11 regression: Indexing messages with fts-tika may have
  resulted in Panic: file message-parser.c: line 802 \ 
(message_parser_deinit_from_parts):
  assertion failed: (ctx->nested_parts_count == 0 || \ 
i_stream_have_bytes_left(ctx->input))
- imap: SETMETADATA could not be used to unset metadata values.
  Instead NIL was handled as a "NIL" string. v2.3.14 regression.
- imap: IMAP BINARY FETCH crashes at least on empty base64 body:
  Panic: file index-mail-binary.c: line 358 (blocks_count_lines):
  assertion failed: (block_count == 0 || block_idx+1 == block_count)
- imap: If IMAP client using the NOTIFY command was disconnected while
  sending FETCH notifications to the client, imap could crash with
  Panic: Trying to close mailbox INBOX with open transactions.
- imap: Using IMAP COMPRESS extension can cause IMAP connection to hang
  when IMAP commands are >8 kB long.
- imapc: If remote server sent BYE but didn't immediately disconnect, it
  could cause infinite busy-loop.
- lib-index: Corrupted cache record size in dovecot.index.cache file
  could have caused a crash (segfault) when accessing it.
- lib-oauth2: JWT token time validation now works correctly with
  32-bit systems.
- lib-ssl-iostream: Checking hostnames against an SSL certificate was
  case-sensitive.
- lib-storage: Corrupted mime.parts in dovecot.index.cache may have
  resulted in Panic: file imap-bodystructure.c: line 206 (part_write_body):
  assertion failed: (text == ((part->flags & MESSAGE_PART_FLAG_TEXT) != 0))
- lib-storage: Index rebuilding (e.g. via doveadm force-resync) didn't
  preserve the "hdr-pop3-uidl" header. Because of this, the next pop3
  session could have accessed all of the emails' metadata to read their
  POP3 UIDL (opening dbox files).
- listescape: When using the listescape plugin and a shared namespace
  the plugin didn't work properly anymore resulting in errors like:
  "Invalid mailbox name: Name must not have '/' character."
- lmtp: Connection crashes if connection gets disconnected due to
  multiple bad commands and the last bad command is BDAT.
- lmtp: The Dovecot-specific LMTP parameter XRCPTFORWARD was blindly
  forwarded by LMTP proxy without checking that the backend has support.
  This caused a command parameter error from the backend if it was
  running an older Dovecot release. This could only occur in more complex
  setups where the message was proxied twice; when the proxy generated
  the XRCPTFORWARD parameter itself the problem did not occur, so this
  only happened when it was forwarded.
- lmtp: The LMTP proxy crashes with a panic when the remote server
  replies with an error while the mail is still being forwarded through
  a DATA/BDAT command.
- lmtp: Username may have been missing from lmtp log line prefixes when
  it was performing autoexpunging.
- master: Dovecot would incorrectly fail with haproxy 2.0.14 service
  checks.
- master: Systemd service: Dovecot announces readiness for accepting
  connections earlier than it should. The following environment variables
  are now imported automatically and can be omitted from
  import_environment setting: NOTIFY_SOCKET LISTEN_FDS LISTEN_PID.
- master: service { process_min_avail } was launching processes too
  slowly when master was forking a lot of processes.
- util: Make the health-check.sh example script POSIX shell compatible.