Release v2.3.21.1

- CVE-2024-23184: A large number of address headers in email resulted
  in excessive CPU usage.
- CVE-2024-23185: Abnormally large email headers are now truncated or
  discarded, with a limit of 10MB on a single header and 50MB for all
  the headers of all the parts of an email.
- oauth2: Dovecot would send client_id and client_secret as POST parameters
  to introspection server. These need to be optionally in Basic auth
  instead as required by OIDC specification.
- oauth2: JWT key type check was too strict.
- oauth2: JWT token audience was not validated against client_id as
  required by OIDC specification.
- oauth2: XOAUTH2 and OAUTHBEARER mechanisms were not giving out
  protocol specific error message on all errors. This broke OIDC discovery.
- oauth2: JWT aud validation was not performed if aud was missing
  from token, but was configured on Dovecot.

Release v2.3.21

* lib-oauth2: Allow JWT tokens to be validated with missing typ field.
  The typ field is left out by some key issuers to conserve space,
  notably kubernetes. Now missing typ is tolerated, but if present, it
  still must be "jwt".
+ auth: Auth passdb and userdb reply can contain "event_<name>=value"
  which will be added to login event and mail user event respectively.
+ lib-master: Set process title during various initialization stages to
  clearly describe what the process is waiting on.
+ lib-storage: The mail_temp_scan_interval is now fuzzed incrementing it
  by 0..30% based on username's hash to reduce the chance of load spikes
.
+ lib-storage: The temp file scan has been moved from the open of the
  mailbox to the close, to reduce the latency perceived by users.
+ stats: If metric has fields specified, all these fields are
  exported as counters to prometheus exposition.
  See https://doc.dovecot.org/configuration_manual/stats/openmetrics/.
- *-login: Processes might have crashed when a SSL connection disconnect
s
  uncleanly.
- acl: When plugin was loaded \HasChildren and \HasNoChildren flags
  were calculated incorrectly for mailboxes containing '*' and '%'
  in their names.
- auth: Crash occured if a connection to PostgreSQL database server
  failed during startup.
- auth: Logins with invalid passwords (e.g. unknown scheme) in passdb
  were failing with "password mismatch" instead of "internal error".
- auth: XOAUTH2 and OAUTHBEARER mechanisms were not giving out protocol
  specific error message on all errors. This especially broke OIDC
  discovery.
- dbox: When last_temp_file_scan header wasn't set (especially after
  dsync migration), the next mailbox open always triggers the temp file
  scan. This could have caused a load spike after migrations. Fixed by
  using the mailbox directory's atime when the header isn't set, which
  usually moves the scan time into the future.
- dict-redis: A crash would occur on transaction rollback.
- dsync: Infinite loop causing out of memory would occur when handling
  mailbox deletion from remote end and hierarchy separators would differ.
- dsync: Incremental dsync failed for folder names ending with '%',
  unless BROKENCHAR was set. Also folder names with '%' elsewhere in
  them caused each incremental dsync to unnecessarily rename the folder
  to a temporary name and back. v2.3.19 regression.
- imap-hibernate: If an IMAP client unhibernation timed out with
  "(version received)", the unhibernation could still have successfully
  finished later on and continued working normally. This was rather
  confusing, because imap-hibernate already logged that the client got
  disconnected. Avoid this by forcing the connection to shutdown on
  unhibernation timeout.
- imapc: Crashed when a folder mapped through the virtual plugin
  disappears from the storage.
- imapc: EXPUNGE, EXISTS or FETCH replies from a server for a previously
  selected mailbox could have been processed as if they belonged to the
  new mailbox currently being selected. This could have caused warnings.
- lib-http: Dovecot HTTP server (doveadm, stats/openmetrics) may have
  disconnected HTTP clients before the response is fully sent. This
  happened only on busy servers where kernel's socket buffers were
  rather full.
- lib-http: Fixed a potential crash on http-server if a client
  disconnected early. v2.3.18 regression.
- lib-index: Index file corruption could have caused a crash. Fixes:
  Panic: file mail-transaction-log-view.c: line 165 (mail_transaction_log_view_set):
  assertion failed: (min_file_seq <= max_file_seq).
- lib-index: Purging an existing >1GB cache file can crash. Now cache
  files still above 1GB after purging are removed. Fixes:
  Panic: file mail-index-util.c: line 10 (mail_index_uint32_to_offset):
  assertion failed: (offset < 0x40000000)
- lib-lua: A HTTP client could not resolve DNS names in mail processes,
  because it expected "the dns-client" socket to exist in the current
  directory.
- lib-oauth2: Dovecot would send client_id and client_secret as POST
  parameters to the introspection server. These need to be optionally in
  Basic auth instead.
- lib-oauth2: JWT aud validation was not performed if aud was missing
  from a token, but was configured on Dovecot.
- lib-oauth2: JWT key type check was too strict.
- lib-oauth2: JWT token audience was not validated against client_id as
  required by the specification.
- lib-ssl-iostream: Using the ssl_require_crl=yes setting may have caused
  CRL check failures for outgoing SSL/TLS connections, although it was
  supposed to affect checking CRLs only for client-side SSL
  certificates. v2.3.17 regression.
- lib-sql: MySQL driver leaked memory when connection failed.
- lib-storage: Various fixes when running into out of disk space.
- master: Service idle_kill setting didn't work properly on busy
  servers. It was very unlikely that any process was idling long enough
  to become killed. Also the idle_kill handling code was using quite a
  lot of CPU on the master process when there were a lot of processes
  (e.g. imap). The new behavior is to track the lowest number of idling
  processes every idle_kill time interval and then kill that many idling
  processes.
- mdbox: Temp file scan was done for always empty directories.
- mdbox: The fdatasync() call was done in wrong parent directory when
  writing mails. Also on a failure it crashed instead of logging an error.
- notify_status: The plugin crashes if any user initialization fails.
- pop3: Sending command with the ':' character caused an assert-crash.
  v2.3.18 regression. Fixes: Panic: event_reason_code_prefix(): name has ':'
- stats: Fix panic when a nonexistent event exporter was referenced while
  adding a new metric dynamically via doveadm stats add. This produces
  a proper error now.
- stats: If process exported a lot of events and then exited, some of
  the last events may have become lost.
- stats: Invalid Prometheus label names were created with specific
  histogram group_by configurations. Prometheus rejected these labels.
- welcome: The plugin didn't execute in some situations that created
  INBOX but didn't open it, e.g. if GETMETADATA was used before the
  INBOX was opened.

Release v2.3.20

+ Add dsync_features=no-header-hashes. When this setting is enabled and
  one dsync side doesn't support mail GUIDs (i.e. imapc), there is no
  fallback to using header hashes. Instead, dsync assumes that all mails
  with identical IMAP UIDs contains the same mail contents. This can
  significantly improve dsync performance with some IMAP servers that
  don't support caching Date/Message-ID headers.
+ lua: HTTP client has more settings now, see
  https://doc.dovecot.org/admin_manual/lua/#dovecot.http.client
+ replicator: "doveadm replicator status" command now outputs when the
  next sync is expected for the user.
- LAYOUT=index: duplicate GUIDs were not cleaned out. Also the list
  recovery was not optimal.
- auth: Assert crash would occur when iterating multiple userdb
  backends.
- director: Logging into director using master user with
  auth_master_user_separator character redirected user to a wrong
  backend, unless master_user_separator setting was also set to the same
  value. Merged these into auth_master_user_separator.
- dsync: Couldn't always fix folder GUID conflicts automatically with
  Maildir format. This resulted in replication repeatedly failing
  with "Remote lost mailbox GUID".
- dsync: Failed to migrate INBOX when using namespace prefix=INBOX/,
  resulting in "Remote lost mailbox GUID" errors.
- dsync: INBOX was created too early with namespace prefix=INBOX/,
  resulting a GUID conflict. This may have been resolved automatically,
  but not always.
- dsync: v2.3.18 regression: Wrong imapc password with dsync caused
  Panic: file lib-event.c: line 506 (event_pop_global):
  assertion failed: (event == current_global_event)
- imapc: Requesting STATUS for a mailbox with imapc and INDEXPVT
  configured did not return correct (private) unseen counts.
- lib-dict: Process would crash when committing data to redis without
  dict proxy.
- lib-mail: Corrupted cached BODYSTRUCTURE caused panic during FETCH.
  Fixes: Panic: file message-part-data.c: line 579 (message_part_is_attachment):
  assertion failed: (data != NULL). v2.3.13 regression.
- lib-storage: mail_attribute_dict with dict-sql failed when it tried to
  lookup empty dict keys.
- lib: ioloop-kqueue was missing include breaking some BSD builds.
- lua-http: Dovecot Lua HTTP client could not resolve DNS names in mail
  processes, because it expected "dns-client" socket to exist in the
  current directory.
- oauth2: Using %{oauth2:name} variables could cause useless
  introspections.
- pop3: Sending POP3 command with ':' character caused an assert-crash.
  v2.3.18 regression.
- replicator: Replication queue had various issues, potentially causing
  replication requests to become stuck.
- stats: Invalid Prometheus label names were created with specific
  histogram group_by configurations. Prometheus rejected these labels.

Release v2.3.19.1

- doveadm deduplicate: Non-duplicate mails were deleted.
  v2.3.19 regression.
- auth: Crash would occur when iterating multiple backends.
  Fixes: Panic: file userdb-blocking.c:
  line 125 (userdb_blocking_iter_next): assertion failed: (ctx->conn != NULL)

Release v2.3.19

+ Added mail_user_session_finished event, which is emitted when the mail
  user session is finished (e.g. imap, pop3, lmtp). It also includes
  fields with some process statistics information.
  See https://doc.dovecot.org/admin_manual/list_of_events/ for more
  information.
+ Added process_shutdown_filter setting. When an event matches the filter,
  the process will be shutdown after the current connection(s) have
  finished. This is intended to reduce memory usage of long-running imap
  processes that keep a lot of memory allocated instead of freeing it to
  the OS.
+ auth: Add cache hit indicator to auth passdb/userdb finished events.
  See https://doc.dovecot.org/admin_manual/list_of_events/ for more
  information.
+ doveadm deduplicate: Performance is improved significantly.
+ imapc: COPY commands were sent one mail at a time to the remote IMAP
  server. Now the copying is buffered, so multiple mails can be copied
  with a single COPY command.
+ lib-lua: Add a Lua interface to Dovecot's HTTP client library. See
  https://doc.dovecot.org/admin_manual/lua/ for more information.
- auth: Cache lookup would use incorrect cache key after username change.
- auth: Improve handling unexpected LDAP connection errors/hangs.
  Try to fix up these cases by reconnecting to the LDAP server and
  aborting LDAP requests earlier.
- auth: Process crashed if userdb iteration was attempted while auth-workers
  were already full handling auth requests.
- auth: db-oauth2: Using %{oauth2:name} variables caused unnecessary
  introspection requests.
- dict: Timeouts may have been leaked at deinit.
- director: Ring may have become unstable if a backend's tag was changed.
  It could also have caused director process to crash.
- doveadm kick: Numeric parameter was treated as IP address.
- doveadm: Proxying can panic when flushing print output. Fixes
  Panic: file ioloop.c: line 865 (io_loop_destroy): assertion failed:
  (ioloop == current_ioloop).
- doveadm sync: BROKENCHAR was wrongly changed to '_' character when
  migrating mailboxes. This was set by default to %, so any mailbox
  names containing % characters were modified to "_25".
- imapc: Copying or moving mails with doveadm to an imapc mailbox could
  have produced "Error: Syncing mailbox '[...]' failed" Errors. The
  operation itself succeeded but attempting to sync the destination
  mailbox failed.
- imapc: Prevent index log synchronization errors when two or more imapc
  sessions are adding messages to the same mailbox index files, i.e.
  INDEX=MEMORY is not used.
- indexer: Process was slowly leaking memory for each indexing request.
- lib-fts: fts header filters caused binary content to be sent to the
  indexer with non-default configuration.
- doveadm-server: Process could hang in some situations when printing
  output to TCP client, e.g. when printing doveadm sync state.
- lib-index: dovecot.index.log files were often read and parsed entirely,
  rather than only the parts that were actually necessary. This mainly
  increased CPU usage.
- lmtp-proxy: Session ID forwarding would cause same session IDs being
  used when delivering same mail to multiple backends.
- log: Log prefix update may have been lost if log process was busy.
  This could have caused log prefixes to be empty or in some cases
  reused between sessions, i.e. log lines could have been logged for the
  wrong user/session.
- mail_crypt: Plugin crashes if it's loaded only for some users. Fixes
  Panic: Module context mail_crypt_user_module missing.
- mail_crypt: When LMTP was delivering mails to both recipients with mail
  encryption enabled and not enabled, the non-encrypted recipients may
  have gotten mails encrypted anyway. This happened when the first
  recipient was encrypted (mail_crypt_save_version=2) and the 2nd
  recipient was not encrypted (mail_crypt_save_version=0).
- pop3: Session would crash if empty line was sent.
- stats: HTTP server leaked memory.
- submission-login: Long credentials, such as OAUTH2 tokens, were refused
  during SASL interactive due to submission server applying line length
  limits.
- submission-login: When proxying to remote host, authentication was not
  using interactive SASL when logging in using long credentials such as
  OAUTH2 tokens. This caused authentication to fail due to line length
  constraints in SMTP protocol.
- submission: Terminating the client connection with QUIT command after
  mail transaction is started with MAIL command and before it is
  finished with DATA/BDAT can cause a segfault crash.
- virtual: doveadm search queries with mailbox-guid as the only parameter
  crashes: Panic: file virtual-search.c: line 77 (virtual_search_get_records):
  assertion failed: (result != 0)

Release v2.3.18

* Removed mail_cache_lookup_finished event. This event wasn't especially
  useful, but it increased CPU usage significantly.
* fts: Don't index inline base64 encoded content in FTS indexes using
  the generic tokenizer. This reduces the FTS index sizes by removing
  input that is very unlikely to be searched for. See
  https://doc.dovecot.org/configuration_manual/fts/tokenization for
  details on how base64 is detected. Only applies when using libfts.
* lmtp: Session IDs are now preserved through proxied connections, so
  LMTP sessions can be tracked. This slightly changes the LMTP session
  ID format by appending ":Tn" (transaction), ":Pn" (proxy connection)
  and ":Rn" (recipient) counters after the session ID prefix.
+ Events now have "reason_code" field, which can provide a list of
  reasons why the event is happening. See
  https://doc.dovecot.org/admin_manual/event_reasons/
+ New events are added. See https://doc.dovecot.org/admin_manual/list_of_events/
+ fts: Added fts_header_excludes and fts_header_includes settings to
  specify which headers to index. See
  https://doc.dovecot.org/settings/plugin/fts-plugin#plugin-fts-setting-fts-header-excludes
  for configuration details.
+ fts: Initialize the textcat language detection library only once per
  process. This can reduce CPU usage if fts_languages setting has multiple
  languages listed and service indexer-worker { service_count } isn't 1.
  Only applies when using libfts.
+ lib-storage: Reduced CPU usage significantly for some operations that
  accessed lots of emails (e.g. fetching all flags in a folder, SORT, ...)
+ lib: DOVECOT_PREREQ() - Add micro version which enables compiling
  external plugins against different versions of Dovecot.
+ lmtp: Added new lmtp_verbose_replies setting that makes errors sent to
  the LMTP client much more verbose with details about why exactly
  backend proxy connections or commands are failing.
+ submission: Support implicit SASL EXTERNAL with
  submission_client_workarounds=implicit-auth-external. This allows
  automatically logging in when SSL client certificate is present.
- *-login: Statistics were disabled if stats process connection was lost.
- auth: Authentication master user login fails with SCRAM-* SASL mechanisms.
- auth: With auth_cache_verify_password_with_worker=yes, passdb extra
  fields in the auth cache got lost.
- doveadm: Fixed crash if zlib_save_level setting was specified,
  but zlib_save was unset. v2.3.15 regression.
- doveadm: Proxying can panic when flushing print output. v2.3.17
  regression. Fixes:
  Panic: file ioloop.c: line 865 (io_loop_destroy): assertion failed:
  (ioloop == current_ioloop)
- doveadm: stats add --group-by parameter didn't work.
- fts: Using email-address fts tokenizer could result in excessive memory
  usage with garbage email input. This could cause the indexer-worker
  processes to fail due to reaching the VSZ memory size limit.
  Only applies when using libfts.
- imap: A SEARCH command timing out while fts returns indexes may timeout
  returning "NO [SERVERBUG]", while it should return "NO [INUSE]" instead.
- imap: LIST-EXTENDED doesn't return STATUS for all folders. Sending
  LIST .. RETURN (SUBSCRIBED STATUS (...)) did not return STATUS for
  folders that are not subscribed when they have a child folder that is
  subscribed as mandated by IMAP RFCs.
- imapc: Mailbox vsize calculation crashed with
  Panic: file index-mailbox-size.c: line 344 (index_mailbox_vsize_hdr_add_missing):
  assertion failed: (mails_left > 0)
- indexer: If indexer-worker crashes, the request it was processing gets
  stuck in the indexer process. This stops indexing for the folder until
  indexer process is restarted. v2.3.14 regression.
- indexer: Process was slowly leaking memory for each indexing request.
- lib-event: Unnamed events were wrongly filtered out for event/metric
  filters like "event=abc OR something_independent_of_event_name".
- lib-index: 64-bit big endian CPUs handle last_used field in
  dovecot.index.cache wrong.
- lib-ssl-iostream: Fix buggy OpenSSL error handling without assert-crashing.
  If there is no error available, log it as an error instead of crashing.
  The previous fix for this in v2.3.11 was incomplete. Fixes
  Panic: file istream-openssl.c: line 51 (i_stream_ssl_read_real):
  assertion failed: (errno != 0)
- lmtp: Out-of-memory issues can happen when proxying large messages to
  LMTP backend servers that accept the message data too slow.
- master: HAProxy header parsing has read buffer overflow if provided
  header size is invalid. This happens only if inet_listener
  { haproxy=yes } is configured and only if the remote IP address is in
  haproxy_trusted_networks.
- old_stats: Plugin kept increasing memory usage, which became
  noticeable with long-running imap sessions.
- stats: Dynamically adding same metric multiple times causes multiple stats.
- submission-login: Authentication does not accept OAUTH2 token (or
  other very long credentials) because it considers the line to be too long.
- submission-login: Process can crash if HELO is pipelined with an
  invalid domain.
- submission-proxy: Don't use SASL-IR if it would make the AUTH command
  line longer than 512 bytes.
- submission: Service would crash if relay server authentication failed.
- virtual: FTS search in a virtual folder could crash if there are
  duplicate mailbox GUIDs. This mainly happened when user had both INBOX
  and INBOX/INBOX folders and the namespace prefix was INBOX/. Fixes
  Panic: file hash.c: line 252 (hash_table_insert_node):
  assertion failed: (opcode == HASH_TABLE_OP_UPDATE)
- virtual: If mailbox opening fails, the backend mailbox is leaked and
  process crashes when client disconnects. Fixes
  Panic: file mail-user.c: line 232 (mail_user_deinit):
  assertion failed: ((*user)->refcount == 1)
- virtual: Searching headers in virtual folders didn't always use
  full-text search indexes, if fts_enforced=no or body.

Release v2.3.17.1

- dsync: Add back accidentically removed parameters.
- lib-ssl-iostream: Fix assert-crash when OpenSSL returned syscall error
  without errno.
- master: Dovecot failed to start if ssl_ca was too large.

Release v2.3.17

* Dovecot now logs a warning if time seems to jump forward at least
  100 milliseconds.
* dict: Lines logged by the dict process now contain the dict name as
  the prefix.
* lib-index: mail_cache_fields, mail_always_cache_fields and
  mail_never_cache_fields now verifies that the listed header names are
  valid. Especially the UTF8 "–" character has sometimes been wrongly
  used instead of the ASCII "-".
+ *-login: Added login_proxy_rawlog_dir setting to capture
  rawlogs between proxy and backend.
+ dict: The server process now keeps the last 10 idle dict backends
  cached for maximum of 30 seconds. Practically this acts as a
  connection pool for dict-redis and dict-ldap. Note that this doesn't
  affect dict-sql, because it already had its own internal cache.
+ doveadm: New stats add/remove commands added to support changing the
  metrics configuration on runtime.
+ lazy_expunge: Added lazy_expunge_exclude settings to disable
  lazy_expunge for specific folders. \Special-use flags can be used as
  folder names.
+ lib-lua: Added a new helper function dovecot.restrict_global_variables()
  to disable or enable defining new global variables.
- LAYOUT=index List index rebuild was missing.
- LAYOUT=index: Duplicate GUIDs were not detected.
- acl: When using acl_ignore_namespace Dovecot attempted to access or
  create dovecot-acl-list even when the namespace should have been
  ignored. For virtual namespaces this could have yielded errors about
  "Read-only file system" or "Permission denied".
- auth: Setting the "master" passdb field to empty value would
  cause proxying to fail with an authentication error.
  Now an empty "master" field is ignored.
- doveadm-server: Duplicate error lines were sent for failed commands.
  This didn't normally cause visible problems, except when using
  wildcards in usernames or -A parameter to go through multiple users.
- doveadm-server: Logs written by doveadm-server were often missing log
  prefixes, especially mail_log_prefix for mail commands. Logs sent to
  doveadm TCP client were also missing log prefixes.
- doveadm: v2.3 regression: batch command always crashes.
- doveadm: v2.3.11 regression: Commands failed if ssl_cert or
  ssl_key files weren't readable by the user running doveadm, even
  though doveadm didn't actually use these settings
- imap-hibernate: Process may crash at deinit:
  Panic: file ioloop.c: line 928 (io_loop_destroy): assertion failed:
  (ioloop->cur_ctx == NULL).
- imap: Using imap_fetch_failure=no-after can cause assert-crash
  with some IMAP commands if reading the mail fails (e.g. wrong cached
  mail size). Fixes:
  Panic: file index-mail-headers.c: line 198 (index_mail_parse_header_init):
  assertion failed: (!mail->data.header_parser_initialized)
- imap: v2.3.10 regression: When using INDEXPVT to enable private
  \Seen flags (for shared or public namespaces) the STORE command did
  not send untagged replies for the \Seen flag changes.
- imap: v2.3.15 regression: If PREVIEW/SNIPPET is not the final FETCH
  option in the command, the IMAP FETCH response is broken.
- imap: v2.3.15 regression: MOVE command leaks mailbox if it can't be
  opened and crashes at deinit:
  Panic: file mail-user.c: line 229 (mail_user_deinit): assertion failed:
  ((*user)->refcount == 1).
- imapc: Copying nonexistent mail via imapc could have crashed. Fixes:
  Panic: file mail-storage.c: line 2385 (mailbox_transaction_commit_get_changes):
  assertion failed: (ret < 0 || seq_range_count(&changes_r->saved_uids) == save_count ||
  array_count(&changes_r->saved_uids) == 0).
- indexer: v2.3.15 regression: Process crashes if indexer-client
  disconnects while it's waiting for command reply. This happened for
  example if IMAP SEARCH triggered long fts indexing and the IMAP
  client disconnected while waiting for the reply.
- indexer: v2.3.15 regression: Process may have crashed in some situations.
- indexer: v2.3.15 regression: indexer-worker processes may not have
  reached the process_limit in some situations, possibly even using just
  one indexer-worker process even though there were many indexing
  requests queued.
- lib-compression: Reading lz4 compressed mdbox mails may crash. Fixes:
  Panic: file istream.c: line 345 (i_stream_read_memarea):
  assertion failed: (!stream->blocking).
- lib-compression: bench-compress crashes due to xz being read-only.
- lib-lua: Fix linking libdict_lua for non-GNU linkers when Lua support
  is disabled.
- lib-mail: There was no limit on how large an email header name could be.
  Processable header names are now limited to 1000 bytes.
- lib-oauth2: Dovecot disallowed JWT tokens if their validity time was
  older than token creation time (nbf < iat).
- lib-storage: Reduce memory footprint of certain storage operations.
- lib-storage: When listing mailboxes with storage name escape
  characters (^ or .) as part of the mailbox name, the listing could
  show corrupted mailbox names. Due to an issue in handling escaped
  parent folders, the listing of other mailbox names would become
  corrupted by prepending parts of the previously listed mailboxes
  parent folder as prefix to the actual mailbox names. The corruption
  can occur when using LAYOUT=INDEX and maildir or obox, or when using
  the listescape plugin.
- mail-crypt: Fix "-O" argument for "doveadm mailbox cryptokey password"
  command to be a boolean, and not expect a string.
- submission-login: Add support for not authenticating to next hop in
  submission proxying.
- submission-login: EHLO was not sent again after XCLIENT when doing
  submission proxying.
- virtual: Mailboxes do not correctly detect underlying mailboxes
  getting re-created even though they have a different UIDVALIDITY or
  GUID.

v2.3.16

 * Any unexpected exit() will now result in a core dump. This can
   especially help notice problems when a Lua script causes exit(0).
 * auth-worker process is now restarted when the number of auth
   requests reaches service auth-worker { service_count }. The default
   is still unlimited.

 + Event improvements: Added data_stack_grow event and http-client
   category. See https://doc.dovecot.org/admin_manual/list_of_events/
 + oauth2: Support RFC 7628 openid-configuration element. This allows
   clients to support OAUTH2 for any server, not just a few hardcoded
   servers like they do now. See openid_configuration_url setting in
   dovecot-oauth2.conf.ext.
 + mysql: Single statements are no longer enclosed with BEGIN/COMMIT.
 + dovecot-sysreport --core supports multiple core files now and does
   not require specifying the binary path.
 + imapc: When imap_acl plugin is loaded and imapc_features=acl is used,
   IMAP ACL commands are proxied to the remote server. See
   https://doc.dovecot.org/configuration_manual/mail_location/imapc/
 + dict-sql now supports the "UPSERT" syntax for SQLite and PostgreSQL.
 + imap: If IMAP client disconnects during a COPY command, the copying
   is aborted, and changes are reverted. This may help to avoid many
   email duplicates if client disconnects during COPY and retries it
   after reconnecting.
 - master process was using 100% CPU if service attempted to create more
   processes due to process_min_avail, but process_limit was already
   reached. v2.3.15 regression.
 - Using attachment detection flags wrongly logged unnecessary "Failed
   to add attachment keywords" errors. v2.3.13 regression.
 - IMAP QRESYNC: Expunging UID 1 mail resulted in broken VANISHED
   response, which could have confused IMAP clients. v2.3.13 regression.
 - imap: STORE didn't send untagged replies for \Seen changes for
   (shared) mailboxes using INDEXPVT. v2.3.10 regression.
 - rawlog_dir setting would not log input that was pipelined after
   authentication command.
 - Fixed potential infinite looping with autoexpunging.
 - Log event exporter: Truncate long fields to 1000 bytes
 - LAYOUT=index: ACL inheritance didn't work when creating mailboxes
 - Event filters: Unquoted '?' wildcard caused a crash at startup
 - fs-metawrap: Fix to handling zero sized files
 - imap-hibernate: Fixed potential crash at deinit.
 - acl: dovecot-acl-list files were written for acl_ignore_namespaces
 - program-client (used by Sieve extprograms, director_flush_socket)
   may have missed status response from UNIX and network sockets,
   resulting in unexpected failures.

Release v2.3.15

 * 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.