-
Notifications
You must be signed in to change notification settings - Fork 29
/
imap.rb
2657 lines (2545 loc) · 104 KB
/
imap.rb
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
# frozen_string_literal: true
#
# = net/imap.rb
#
# Copyright (C) 2000 Shugo Maeda <shugo@ruby-lang.org>
#
# This library is distributed under the terms of the Ruby license.
# You can freely distribute/modify this library.
#
# Documentation: Shugo Maeda, with RDoc conversion and overview by William
# Webber.
#
# See Net::IMAP for documentation.
#
require "socket"
require "monitor"
require 'net/protocol'
begin
require "openssl"
rescue LoadError
end
module Net
# Net::IMAP implements Internet Message Access Protocol (\IMAP) client
# functionality. The protocol is described in
# [IMAP4rev1[https://tools.ietf.org/html/rfc3501]] and
# [IMAP4rev2[https://tools.ietf.org/html/rfc9051]].
#
# == \IMAP Overview
#
# An \IMAP client connects to a server, and then authenticates
# itself using either #authenticate or #login. Having
# authenticated itself, there is a range of commands
# available to it. Most work with mailboxes, which may be
# arranged in an hierarchical namespace, and each of which
# contains zero or more messages. How this is implemented on
# the server is implementation-dependent; on a UNIX server, it
# will frequently be implemented as files in mailbox format
# within a hierarchy of directories.
#
# To work on the messages within a mailbox, the client must
# first select that mailbox, using either #select or #examine
# (for read-only access). Once the client has successfully
# selected a mailbox, they enter the "_selected_" state, and that
# mailbox becomes the _current_ mailbox, on which mail-item
# related commands implicitly operate.
#
# === Sequence numbers and UIDs
#
# Messages have two sorts of identifiers: message sequence
# numbers and UIDs.
#
# Message sequence numbers number messages within a mailbox
# from 1 up to the number of items in the mailbox. If a new
# message arrives during a session, it receives a sequence
# number equal to the new size of the mailbox. If messages
# are expunged from the mailbox, remaining messages have their
# sequence numbers "shuffled down" to fill the gaps.
#
# To avoid sequence number race conditions, servers must not expunge messages
# when no command is in progress, nor when responding to #fetch, #store, or
# #search. Expunges _may_ be sent during any other command, including
# #uid_fetch, #uid_store, and #uid_search. The #noop and #idle commands are
# both useful for this side-effect: they allow the server to send all mailbox
# updates, including expunges.
#
# UIDs, on the other hand, are permanently guaranteed not to
# identify another message within the same mailbox, even if
# the existing message is deleted. UIDs are required to
# be assigned in ascending (but not necessarily sequential)
# order within a mailbox; this means that if a non-IMAP client
# rearranges the order of mail items within a mailbox, the
# UIDs have to be reassigned. An \IMAP client thus cannot
# rearrange message orders.
#
# === Examples of Usage
#
# ==== List sender and subject of all recent messages in the default mailbox
#
# imap = Net::IMAP.new('mail.example.com')
# imap.authenticate('LOGIN', 'joe_user', 'joes_password')
# imap.examine('INBOX')
# imap.search(["RECENT"]).each do |message_id|
# envelope = imap.fetch(message_id, "ENVELOPE")[0].attr["ENVELOPE"]
# puts "#{envelope.from[0].name}: \t#{envelope.subject}"
# end
#
# ==== Move all messages from April 2003 from "Mail/sent-mail" to "Mail/sent-apr03"
#
# imap = Net::IMAP.new('mail.example.com')
# imap.authenticate('LOGIN', 'joe_user', 'joes_password')
# imap.select('Mail/sent-mail')
# if not imap.list('Mail/', 'sent-apr03')
# imap.create('Mail/sent-apr03')
# end
# imap.search(["BEFORE", "30-Apr-2003", "SINCE", "1-Apr-2003"]).each do |message_id|
# imap.copy(message_id, "Mail/sent-apr03")
# imap.store(message_id, "+FLAGS", [:Deleted])
# end
# imap.expunge
#
# == Capabilities
#
# Most Net::IMAP methods do not _currently_ modify their behaviour according
# to the server's advertised #capabilities. Users of this class must check
# that the server is capable of extension commands or command arguments before
# sending them. Special care should be taken to follow the #capabilities
# requirements for #starttls, #login, and #authenticate.
#
# See #capable?, #auth_capable, #capabilities, #auth_mechanisms to discover
# server capabilities. For relevant capability requirements, see the
# documentation on each \IMAP command.
#
# imap = Net::IMAP.new("mail.example.com")
# imap.capable?(:IMAP4rev1) or raise "Not an IMAP4rev1 server"
# imap.capable?(:starttls) or raise "Cannot start TLS"
# imap.starttls
#
# if imap.auth_capable?("PLAIN")
# imap.authenticate "PLAIN", username, password
# elsif !imap.capability?("LOGINDISABLED")
# imap.login username, password
# else
# raise "No acceptable authentication mechanisms"
# end
#
# # Support for "UTF8=ACCEPT" implies support for "ENABLE"
# imap.enable :utf8 if imap.auth_capable?("UTF8=ACCEPT")
#
# namespaces = imap.namespace if imap.capable?(:namespace)
# mbox_prefix = namespaces&.personal&.first&.prefix || ""
# mbox_delim = namespaces&.personal&.first&.delim || "/"
# mbox_path = prefix + %w[path to my mailbox].join(delim)
# imap.create mbox_path
#
# === Basic IMAP4rev1 capabilities
#
# IMAP4rev1 servers must advertise +IMAP4rev1+ in their capabilities list.
# IMAP4rev1 servers must _implement_ the +STARTTLS+, <tt>AUTH=PLAIN</tt>,
# and +LOGINDISABLED+ capabilities. See #starttls, #login, and #authenticate
# for the implications of these capabilities.
#
# === Caching +CAPABILITY+ responses
#
# Net::IMAP automatically stores and discards capability data according to the
# the requirements and recommendations in
# {IMAP4rev2 §6.1.1}[https://www.rfc-editor.org/rfc/rfc9051#section-6.1.1],
# {§6.2}[https://www.rfc-editor.org/rfc/rfc9051#section-6.2], and
# {§7.1}[https://www.rfc-editor.org/rfc/rfc9051#section-7.1].
# Use #capable?, #auth_capable?, or #capabilities to use this cache and avoid
# sending the #capability command unnecessarily.
#
# The server may advertise its initial capabilities using the +CAPABILITY+
# ResponseCode in a +PREAUTH+ or +OK+ #greeting. When TLS has started
# (#starttls) and after authentication (#login or #authenticate), the server's
# capabilities may change and cached capabilities are discarded. The server
# may send updated capabilities with an +OK+ TaggedResponse to #login or
# #authenticate, and these will be cached by Net::IMAP. But the
# TaggedResponse to #starttls MUST be ignored--it is sent before TLS starts
# and is unprotected.
#
# When storing capability values to variables, be careful that they are
# discarded or reset appropriately, especially following #starttls.
#
# === Using IMAP4rev1 extensions
#
# See the {IANA IMAP4 capabilities
# registry}[http://www.iana.org/assignments/imap4-capabilities] for a list of
# all standard capabilities, and their reference RFCs.
#
# IMAP4rev1 servers must not activate behavior that is incompatible with the
# base specification until an explicit client action invokes a capability,
# e.g. sending a command or command argument specific to that capability.
# Servers may send data with backward compatible behavior, such as response
# codes or mailbox attributes, at any time without client action.
#
# Invoking capabilities which are unknown to Net::IMAP may cause unexpected
# behavior and errors. For example, ResponseParseError is raised when
# unknown response syntax is received. Invoking commands or command
# parameters that are unsupported by the server may raise NoResponseError,
# BadResponseError, or cause other unexpected behavior.
#
# Some capabilities must be explicitly activated using the #enable command.
# See #enable for details.
#
# == Thread Safety
#
# Net::IMAP supports concurrent threads. For example,
#
# imap = Net::IMAP.new("imap.foo.net", "imap2")
# imap.authenticate("cram-md5", "bar", "password")
# imap.select("inbox")
# fetch_thread = Thread.start { imap.fetch(1..-1, "UID") }
# search_result = imap.search(["BODY", "hello"])
# fetch_result = fetch_thread.value
# imap.disconnect
#
# This script invokes the FETCH command and the SEARCH command concurrently.
#
# == Errors
#
# An \IMAP server can send three different types of responses to indicate
# failure:
#
# NO:: the attempted command could not be successfully completed. For
# instance, the username/password used for logging in are incorrect;
# the selected mailbox does not exist; etc.
#
# BAD:: the request from the client does not follow the server's
# understanding of the \IMAP protocol. This includes attempting
# commands from the wrong client state; for instance, attempting
# to perform a SEARCH command without having SELECTed a current
# mailbox. It can also signal an internal server
# failure (such as a disk crash) has occurred.
#
# BYE:: the server is saying goodbye. This can be part of a normal
# logout sequence, and can be used as part of a login sequence
# to indicate that the server is (for some reason) unwilling
# to accept your connection. As a response to any other command,
# it indicates either that the server is shutting down, or that
# the server is timing out the client connection due to inactivity.
#
# These three error response are represented by the errors
# Net::IMAP::NoResponseError, Net::IMAP::BadResponseError, and
# Net::IMAP::ByeResponseError, all of which are subclasses of
# Net::IMAP::ResponseError. Essentially, all methods that involve
# sending a request to the server can generate one of these errors.
# Only the most pertinent instances have been documented below.
#
# Because the IMAP class uses Sockets for communication, its methods
# are also susceptible to the various errors that can occur when
# working with sockets. These are generally represented as
# Errno errors. For instance, any method that involves sending a
# request to the server and/or receiving a response from it could
# raise an Errno::EPIPE error if the network connection unexpectedly
# goes down. See the socket(7), ip(7), tcp(7), socket(2), connect(2),
# and associated man pages.
#
# Finally, a Net::IMAP::DataFormatError is thrown if low-level data
# is found to be in an incorrect format (for instance, when converting
# between UTF-8 and UTF-16), and Net::IMAP::ResponseParseError is
# thrown if a server response is non-parseable.
#
# == What's here?
#
# * {Connection control}[rdoc-ref:Net::IMAP@Connection+control+methods]
# * {Server capabilities}[rdoc-ref:Net::IMAP@Server+capabilities]
# * {Handling server responses}[rdoc-ref:Net::IMAP@Handling+server+responses]
# * {Core IMAP commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands]
# * {for any state}[rdoc-ref:Net::IMAP@Any+state]
# * {for the "not authenticated" state}[rdoc-ref:Net::IMAP@Not+Authenticated+state]
# * {for the "authenticated" state}[rdoc-ref:Net::IMAP@Authenticated+state]
# * {for the "selected" state}[rdoc-ref:Net::IMAP@Selected+state]
# * {for the "logout" state}[rdoc-ref:Net::IMAP@Logout+state]
# * {IMAP extension support}[rdoc-ref:Net::IMAP@IMAP+extension+support]
#
# === Connection control methods
#
# - Net::IMAP.new: Creates a new \IMAP client which connects immediately and
# waits for a successful server greeting before the method returns.
# - #starttls: Asks the server to upgrade a clear-text connection to use TLS.
# - #logout: Tells the server to end the session. Enters the "_logout_" state.
# - #disconnect: Disconnects the connection (without sending #logout first).
# - #disconnected?: True if the connection has been closed.
#
# === Server capabilities
#
# - #capable?: Returns whether the server supports a given capability.
# - #capabilities: Returns the server's capabilities as an array of strings.
# - #auth_capable?: Returns whether the server advertises support for a given
# SASL mechanism, for use with #authenticate.
# - #auth_mechanisms: Returns the #authenticate SASL mechanisms which
# the server claims to support as an array of strings.
# - #clear_cached_capabilities: Clears cached capabilities.
#
# <em>The capabilities cache is automatically cleared after completing
# #starttls, #login, or #authenticate.</em>
# - #capability: Sends the +CAPABILITY+ command and returns the #capabilities.
#
# <em>In general, #capable? should be used rather than explicitly sending a
# +CAPABILITY+ command to the server.</em>
#
# === Handling server responses
#
# - #greeting: The server's initial untagged response, which can indicate a
# pre-authenticated connection.
# - #responses: Yields unhandled UntaggedResponse#data and <em>non-+nil+</em>
# ResponseCode#data.
# - #clear_responses: Deletes unhandled data from #responses and returns it.
# - #add_response_handler: Add a block to be called inside the receiver thread
# with every server response.
# - #response_handlers: Returns the list of response handlers.
# - #remove_response_handler: Remove a previously added response handler.
#
# === Core \IMAP commands
#
# The following commands are defined either by
# the [IMAP4rev1[https://tools.ietf.org/html/rfc3501]] base specification, or
# by one of the following extensions:
# [IDLE[https://tools.ietf.org/html/rfc2177]],
# [NAMESPACE[https://tools.ietf.org/html/rfc2342]],
# [UNSELECT[https://tools.ietf.org/html/rfc3691]],
# [ENABLE[https://tools.ietf.org/html/rfc5161]],
# [MOVE[https://tools.ietf.org/html/rfc6851]].
# These extensions are widely supported by modern IMAP4rev1 servers and have
# all been integrated into [IMAP4rev2[https://tools.ietf.org/html/rfc9051]].
# <em>*NOTE:* Net::IMAP doesn't support IMAP4rev2 yet.</em>
#
# ==== Any state
#
# - #capability: Returns the server's capabilities as an array of strings.
#
# <em>In general, #capable? should be used rather than explicitly sending a
# +CAPABILITY+ command to the server.</em>
# - #noop: Allows the server to send unsolicited untagged #responses.
# - #logout: Tells the server to end the session. Enters the "_logout_" state.
#
# ==== Not Authenticated state
#
# In addition to the commands for any state, the following commands are valid
# in the "<em>not authenticated</em>" state:
#
# - #starttls: Upgrades a clear-text connection to use TLS.
#
# <em>Requires the +STARTTLS+ capability.</em>
# - #authenticate: Identifies the client to the server using the given
# {SASL mechanism}[https://www.iana.org/assignments/sasl-mechanisms/sasl-mechanisms.xhtml]
# and credentials. Enters the "_authenticated_" state.
#
# <em>The server should list <tt>"AUTH=#{mechanism}"</tt> capabilities for
# supported mechanisms.</em>
# - #login: Identifies the client to the server using a plain text password.
# Using #authenticate is generally preferred. Enters the "_authenticated_"
# state.
#
# <em>The +LOGINDISABLED+ capability</em> <b>must NOT</b> <em>be listed.</em>
#
# ==== Authenticated state
#
# In addition to the commands for any state, the following commands are valid
# in the "_authenticated_" state:
#
# - #enable: Enables backwards incompatible server extensions.
# <em>Requires the +ENABLE+ or +IMAP4rev2+ capability.</em>
# - #select: Open a mailbox and enter the "_selected_" state.
# - #examine: Open a mailbox read-only, and enter the "_selected_" state.
# - #create: Creates a new mailbox.
# - #delete: Permanently remove a mailbox.
# - #rename: Change the name of a mailbox.
# - #subscribe: Adds a mailbox to the "subscribed" set.
# - #unsubscribe: Removes a mailbox from the "subscribed" set.
# - #list: Returns names and attributes of mailboxes matching a given pattern.
# - #namespace: Returns mailbox namespaces, with path prefixes and delimiters.
# <em>Requires the +NAMESPACE+ or +IMAP4rev2+ capability.</em>
# - #status: Returns mailbox information, e.g. message count, unseen message
# count, +UIDVALIDITY+ and +UIDNEXT+.
# - #append: Appends a message to the end of a mailbox.
# - #idle: Allows the server to send updates to the client, without the client
# needing to poll using #noop.
# <em>Requires the +IDLE+ or +IMAP4rev2+ capability.</em>
# - *Obsolete* #lsub: <em>Replaced by <tt>LIST-EXTENDED</tt> and removed from
# +IMAP4rev2+.</em> Lists mailboxes in the "subscribed" set.
#
# <em>*Note:* Net::IMAP hasn't implemented <tt>LIST-EXTENDED</tt> yet.</em>
#
# ==== Selected state
#
# In addition to the commands for any state and the "_authenticated_"
# commands, the following commands are valid in the "_selected_" state:
#
# - #close: Closes the mailbox and returns to the "_authenticated_" state,
# expunging deleted messages, unless the mailbox was opened as read-only.
# - #unselect: Closes the mailbox and returns to the "_authenticated_" state,
# without expunging any messages.
# <em>Requires the +UNSELECT+ or +IMAP4rev2+ capability.</em>
# - #expunge: Permanently removes messages which have the Deleted flag set.
# - #uid_expunge: Restricts expunge to only remove the specified UIDs.
# <em>Requires the +UIDPLUS+ or +IMAP4rev2+ capability.</em>
# - #search, #uid_search: Returns sequence numbers or UIDs of messages that
# match the given searching criteria.
# - #fetch, #uid_fetch: Returns data associated with a set of messages,
# specified by sequence number or UID.
# - #store, #uid_store: Alters a message's flags.
# - #copy, #uid_copy: Copies the specified messages to the end of the
# specified destination mailbox.
# - #move, #uid_move: Moves the specified messages to the end of the
# specified destination mailbox, expunging them from the current mailbox.
# <em>Requires the +MOVE+ or +IMAP4rev2+ capability.</em>
# - #check: <em>*Obsolete:* removed from +IMAP4rev2+.</em>
# Can be replaced with #noop or #idle.
#
# ==== Logout state
#
# No \IMAP commands are valid in the "_logout_" state. If the socket is still
# open, Net::IMAP will close it after receiving server confirmation.
# Exceptions will be raised by \IMAP commands that have already started and
# are waiting for a response, as well as any that are called after logout.
#
# === \IMAP extension support
#
# ==== RFC9051: +IMAP4rev2+
#
# Although IMAP4rev2[https://tools.ietf.org/html/rfc9051] is not supported
# yet, Net::IMAP supports several extensions that have been folded into it:
# +ENABLE+, +IDLE+, +MOVE+, +NAMESPACE+, +SASL-IR+, +UIDPLUS+, and +UNSELECT+.
# Commands for these extensions are listed with the {Core IMAP
# commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands], above.
#
# >>>
# <em>The following are folded into +IMAP4rev2+ but are currently
# unsupported or incompletely supported by</em> Net::IMAP<em>: RFC4466
# extensions, +ESEARCH+, +SEARCHRES+, +LIST-EXTENDED+,
# +LIST-STATUS+, +LITERAL-+, +BINARY+ fetch, and +SPECIAL-USE+. The
# following extensions are implicitly supported, but will be updated with
# more direct support: RFC5530 response codes, <tt>STATUS=SIZE</tt>, and
# <tt>STATUS=DELETED</tt>.</em>
#
# ==== RFC2087: +QUOTA+
# - #getquota: returns the resource usage and limits for a quota root
# - #getquotaroot: returns the list of quota roots for a mailbox, as well as
# their resource usage and limits.
# - #setquota: sets the resource limits for a given quota root.
#
# ==== RFC2177: +IDLE+
# Folded into IMAP4rev2[https://tools.ietf.org/html/rfc9051] and also included
# above with {Core IMAP commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands].
# - #idle: Allows the server to send updates to the client, without the client
# needing to poll using #noop.
#
# ==== RFC2342: +NAMESPACE+
# Folded into IMAP4rev2[https://tools.ietf.org/html/rfc9051] and also included
# above with {Core IMAP commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands].
# - #namespace: Returns mailbox namespaces, with path prefixes and delimiters.
#
# ==== RFC2971: +ID+
# - #id: exchanges client and server implementation information.
#
# ==== RFC3691: +UNSELECT+
# Folded into IMAP4rev2[https://tools.ietf.org/html/rfc9051] and also included
# above with {Core IMAP commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands].
# - #unselect: Closes the mailbox and returns to the "_authenticated_" state,
# without expunging any messages.
#
# ==== RFC4314: +ACL+
# - #getacl: lists the authenticated user's access rights to a mailbox.
# - #setacl: sets the access rights for a user on a mailbox
# >>>
# *NOTE:* +DELETEACL+, +LISTRIGHTS+, and +MYRIGHTS+ are not supported yet.
#
# ==== RFC4315: +UIDPLUS+
# Folded into IMAP4rev2[https://tools.ietf.org/html/rfc9051] and also included
# above with {Core IMAP commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands].
# - #uid_expunge: Restricts #expunge to only remove the specified UIDs.
# - Updates #select, #examine with the +UIDNOTSTICKY+ ResponseCode
# - Updates #append with the +APPENDUID+ ResponseCode
# - Updates #copy, #move with the +COPYUID+ ResponseCode
#
# ==== RFC4959: +SASL-IR+
# Folded into IMAP4rev2[https://tools.ietf.org/html/rfc9051].
# - Updates #authenticate with the option to send an initial response.
#
# ==== RFC5161: +ENABLE+
# Folded into IMAP4rev2[https://tools.ietf.org/html/rfc9051] and also included
# above with {Core IMAP commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands].
# - #enable: Enables backwards incompatible server extensions.
#
# ==== RFC5256: +SORT+
# - #sort, #uid_sort: An alternate version of #search or #uid_search which
# sorts the results by specified keys.
# ==== RFC5256: +THREAD+
# - #thread, #uid_thread: An alternate version of #search or #uid_search,
# which arranges the results into ordered groups or threads according to a
# chosen algorithm.
#
# ==== +XLIST+ (non-standard, deprecated)
# - #xlist: replaced by +SPECIAL-USE+ attributes in #list responses.
#
# ==== RFC6851: +MOVE+
# Folded into IMAP4rev2[https://tools.ietf.org/html/rfc9051] and also included
# above with {Core IMAP commands}[rdoc-ref:Net::IMAP@Core+IMAP+commands].
# - #move, #uid_move: Moves the specified messages to the end of the
# specified destination mailbox, expunging them from the current mailbox.
#
# ==== RFC6855: <tt>UTF8=ACCEPT</tt>, <tt>UTF8=ONLY</tt>
#
# - See #enable for information about support for UTF-8 string encoding.
#
# == References
#
# [{IMAP4rev1}[https://www.rfc-editor.org/rfc/rfc3501.html]]::
# Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - \VERSION 4rev1",
# RFC 3501, DOI 10.17487/RFC3501, March 2003,
# <https://www.rfc-editor.org/info/rfc3501>.
#
# [IMAP-ABNF-EXT[https://www.rfc-editor.org/rfc/rfc4466.html]]::
# Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4 ABNF",
# RFC 4466, DOI 10.17487/RFC4466, April 2006,
# <https://www.rfc-editor.org/info/rfc4466>.
#
# <em>Note: Net::IMAP cannot parse the entire RFC4466 grammar yet.</em>
#
# [{IMAP4rev2}[https://www.rfc-editor.org/rfc/rfc9051.html]]::
# Melnikov, A., Ed., and B. Leiba, Ed., "Internet Message Access Protocol
# (\IMAP) - Version 4rev2", RFC 9051, DOI 10.17487/RFC9051, August 2021,
# <https://www.rfc-editor.org/info/rfc9051>.
#
# <em>Note: Net::IMAP is not fully compatible with IMAP4rev2 yet.</em>
#
# [IMAP-IMPLEMENTATION[https://www.rfc-editor.org/info/rfc2683]]::
# Leiba, B., "IMAP4 Implementation Recommendations",
# RFC 2683, DOI 10.17487/RFC2683, September 1999,
# <https://www.rfc-editor.org/info/rfc2683>.
#
# [IMAP-MULTIACCESS[https://www.rfc-editor.org/info/rfc2180]]::
# Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", RFC 2180, DOI
# 10.17487/RFC2180, July 1997, <https://www.rfc-editor.org/info/rfc2180>.
#
# [UTF7[https://tools.ietf.org/html/rfc2152]]::
# Goldsmith, D. and M. Davis, "UTF-7 A Mail-Safe Transformation Format of
# Unicode", RFC 2152, DOI 10.17487/RFC2152, May 1997,
# <https://www.rfc-editor.org/info/rfc2152>.
#
# === Message envelope and body structure
#
# [RFC5322[https://tools.ietf.org/html/rfc5322]]::
# Resnick, P., Ed., "Internet Message Format",
# RFC 5322, DOI 10.17487/RFC5322, October 2008,
# <https://www.rfc-editor.org/info/rfc5322>.
#
# <em>Note: obsoletes</em>
# RFC-2822[https://tools.ietf.org/html/rfc2822]<em> (April 2001) and</em>
# RFC-822[https://tools.ietf.org/html/rfc822]<em> (August 1982).</em>
#
# [CHARSET[https://tools.ietf.org/html/rfc2978]]::
# Freed, N. and J. Postel, "IANA Charset Registration Procedures", BCP 19,
# RFC 2978, DOI 10.17487/RFC2978, October 2000,
# <https://www.rfc-editor.org/info/rfc2978>.
#
# [DISPOSITION[https://tools.ietf.org/html/rfc2183]]::
# Troost, R., Dorner, S., and K. Moore, Ed., "Communicating Presentation
# Information in Internet Messages: The Content-Disposition Header
# Field", RFC 2183, DOI 10.17487/RFC2183, August 1997,
# <https://www.rfc-editor.org/info/rfc2183>.
#
# [MIME-IMB[https://tools.ietf.org/html/rfc2045]]::
# Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions
# (MIME) Part One: Format of Internet Message Bodies",
# RFC 2045, DOI 10.17487/RFC2045, November 1996,
# <https://www.rfc-editor.org/info/rfc2045>.
#
# [MIME-IMT[https://tools.ietf.org/html/rfc2046]]::
# Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions
# (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046,
# November 1996, <https://www.rfc-editor.org/info/rfc2046>.
#
# [MIME-HDRS[https://tools.ietf.org/html/rfc2047]]::
# Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part Three:
# Message Header Extensions for Non-ASCII Text",
# RFC 2047, DOI 10.17487/RFC2047, November 1996,
# <https://www.rfc-editor.org/info/rfc2047>.
#
# [RFC2231[https://tools.ietf.org/html/rfc2231]]::
# Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word
# Extensions: Character Sets, Languages, and Continuations",
# RFC 2231, DOI 10.17487/RFC2231, November 1997,
# <https://www.rfc-editor.org/info/rfc2231>.
#
# [I18n-HDRS[https://tools.ietf.org/html/rfc6532]]::
# Yang, A., Steele, S., and N. Freed, "Internationalized Email Headers",
# RFC 6532, DOI 10.17487/RFC6532, February 2012,
# <https://www.rfc-editor.org/info/rfc6532>.
#
# [LANGUAGE-TAGS[https://www.rfc-editor.org/info/rfc3282]]::
# Alvestrand, H., "Content Language Headers",
# RFC 3282, DOI 10.17487/RFC3282, May 2002,
# <https://www.rfc-editor.org/info/rfc3282>.
#
# [LOCATION[https://www.rfc-editor.org/info/rfc2557]]::
# Palme, J., Hopmann, A., and N. Shelness, "MIME Encapsulation of
# Aggregate Documents, such as HTML (MHTML)",
# RFC 2557, DOI 10.17487/RFC2557, March 1999,
# <https://www.rfc-editor.org/info/rfc2557>.
#
# [MD5[https://tools.ietf.org/html/rfc1864]]::
# Myers, J. and M. Rose, "The Content-MD5 Header Field",
# RFC 1864, DOI 10.17487/RFC1864, October 1995,
# <https://www.rfc-editor.org/info/rfc1864>.
#
# [RFC3503[https://tools.ietf.org/html/rfc3503]]::
# Melnikov, A., "Message Disposition Notification (MDN)
# profile for Internet Message Access Protocol (IMAP)",
# RFC 3503, DOI 10.17487/RFC3503, March 2003,
# <https://www.rfc-editor.org/info/rfc3503>.
#
# === \IMAP Extensions
#
# [QUOTA[https://tools.ietf.org/html/rfc9208]]::
# Melnikov, A., "IMAP QUOTA Extension", RFC 9208, DOI 10.17487/RFC9208,
# March 2022, <https://www.rfc-editor.org/info/rfc9208>.
#
# <em>Note: obsoletes</em>
# RFC-2087[https://tools.ietf.org/html/rfc2087]<em> (January 1997)</em>.
# <em>Net::IMAP does not fully support the RFC9208 updates yet.</em>
# [IDLE[https://tools.ietf.org/html/rfc2177]]::
# Leiba, B., "IMAP4 IDLE command", RFC 2177, DOI 10.17487/RFC2177,
# June 1997, <https://www.rfc-editor.org/info/rfc2177>.
# [NAMESPACE[https://tools.ietf.org/html/rfc2342]]::
# Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
# DOI 10.17487/RFC2342, May 1998, <https://www.rfc-editor.org/info/rfc2342>.
# [ID[https://tools.ietf.org/html/rfc2971]]::
# Showalter, T., "IMAP4 ID extension", RFC 2971, DOI 10.17487/RFC2971,
# October 2000, <https://www.rfc-editor.org/info/rfc2971>.
# [ACL[https://tools.ietf.org/html/rfc4314]]::
# Melnikov, A., "IMAP4 Access Control List (ACL) Extension", RFC 4314,
# DOI 10.17487/RFC4314, December 2005,
# <https://www.rfc-editor.org/info/rfc4314>.
# [UIDPLUS[https://www.rfc-editor.org/rfc/rfc4315.html]]::
# Crispin, M., "Internet Message Access Protocol (\IMAP) - UIDPLUS
# extension", RFC 4315, DOI 10.17487/RFC4315, December 2005,
# <https://www.rfc-editor.org/info/rfc4315>.
# [SORT[https://tools.ietf.org/html/rfc5256]]::
# Crispin, M. and K. Murchison, "Internet Message Access Protocol - SORT and
# THREAD Extensions", RFC 5256, DOI 10.17487/RFC5256, June 2008,
# <https://www.rfc-editor.org/info/rfc5256>.
# [THREAD[https://tools.ietf.org/html/rfc5256]]::
# Crispin, M. and K. Murchison, "Internet Message Access Protocol - SORT and
# THREAD Extensions", RFC 5256, DOI 10.17487/RFC5256, June 2008,
# <https://www.rfc-editor.org/info/rfc5256>.
# [RFC5530[https://www.rfc-editor.org/rfc/rfc5530.html]]::
# Gulbrandsen, A., "IMAP Response Codes", RFC 5530, DOI 10.17487/RFC5530,
# May 2009, <https://www.rfc-editor.org/info/rfc5530>.
# [MOVE[https://tools.ietf.org/html/rfc6851]]::
# Gulbrandsen, A. and N. Freed, Ed., "Internet Message Access Protocol
# (\IMAP) - MOVE Extension", RFC 6851, DOI 10.17487/RFC6851, January 2013,
# <https://www.rfc-editor.org/info/rfc6851>.
# [UTF8=ACCEPT[https://tools.ietf.org/html/rfc6855]]::
# [UTF8=ONLY[https://tools.ietf.org/html/rfc6855]]::
# Resnick, P., Ed., Newman, C., Ed., and S. Shen, Ed.,
# "IMAP Support for UTF-8", RFC 6855, DOI 10.17487/RFC6855, March 2013,
# <https://www.rfc-editor.org/info/rfc6855>.
#
# === IANA registries
# * {IMAP Capabilities}[http://www.iana.org/assignments/imap4-capabilities]
# * {IMAP Response Codes}[https://www.iana.org/assignments/imap-response-codes/imap-response-codes.xhtml]
# * {IMAP Mailbox Name Attributes}[https://www.iana.org/assignments/imap-mailbox-name-attributes/imap-mailbox-name-attributes.xhtml]
# * {IMAP and JMAP Keywords}[https://www.iana.org/assignments/imap-jmap-keywords/imap-jmap-keywords.xhtml]
# * {IMAP Threading Algorithms}[https://www.iana.org/assignments/imap-threading-algorithms/imap-threading-algorithms.xhtml]
# * {SASL Mechanisms and SASL SCRAM Family Mechanisms}[https://www.iana.org/assignments/sasl-mechanisms/sasl-mechanisms.xhtml]
# * {Service Name and Transport Protocol Port Number Registry}[https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml]:
# +imap+: tcp/143, +imaps+: tcp/993
# * {GSSAPI/Kerberos/SASL Service Names}[https://www.iana.org/assignments/gssapi-service-names/gssapi-service-names.xhtml]:
# +imap+
# * {Character sets}[https://www.iana.org/assignments/character-sets/character-sets.xhtml]
# ===== For currently unsupported features:
# * {IMAP Quota Resource Types}[http://www.iana.org/assignments/imap4-capabilities#imap-capabilities-2]
# * {LIST-EXTENDED options and responses}[https://www.iana.org/assignments/imap-list-extended/imap-list-extended.xhtml]
# * {IMAP METADATA Server Entry and Mailbox Entry Registries}[https://www.iana.org/assignments/imap-metadata/imap-metadata.xhtml]
# * {IMAP ANNOTATE Extension Entries and Attributes}[https://www.iana.org/assignments/imap-annotate-extension/imap-annotate-extension.xhtml]
# * {IMAP URLAUTH Access Identifiers and Prefixes}[https://www.iana.org/assignments/urlauth-access-ids/urlauth-access-ids.xhtml]
# * {IMAP URLAUTH Authorization Mechanism Registry}[https://www.iana.org/assignments/urlauth-authorization-mechanism-registry/urlauth-authorization-mechanism-registry.xhtml]
#
class IMAP < Protocol
VERSION = "0.3.4"
# Aliases for supported capabilities, to be used with the #enable command.
ENABLE_ALIASES = {
utf8: "UTF8=ACCEPT",
"UTF8=ONLY" => "UTF8=ACCEPT",
}.freeze
autoload :SASL, File.expand_path("imap/sasl", __dir__)
autoload :StringPrep, File.expand_path("imap/stringprep", __dir__)
include MonitorMixin
if defined?(OpenSSL::SSL)
include OpenSSL
include SSL
end
# Returns the initial greeting the server, an UntaggedResponse.
attr_reader :greeting
# Seconds to wait until a connection is opened.
# If the IMAP object cannot open a connection within this time,
# it raises a Net::OpenTimeout exception. The default value is 30 seconds.
attr_reader :open_timeout
# Seconds to wait until an IDLE response is received.
attr_reader :idle_response_timeout
# The hostname this client connected to
attr_reader :host
# The port this client connected to
attr_reader :port
# Returns the debug mode.
def self.debug
return @@debug
end
# Sets the debug mode.
def self.debug=(val)
return @@debug = val
end
# The default port for IMAP connections, port 143
def self.default_port
return PORT
end
# The default port for IMAPS connections, port 993
def self.default_tls_port
return SSL_PORT
end
class << self
alias default_imap_port default_port
alias default_imaps_port default_tls_port
alias default_ssl_port default_tls_port
end
def client_thread # :nodoc:
warn "Net::IMAP#client_thread is deprecated and will be removed soon."
@client_thread
end
# Disconnects from the server.
#
# Related: #logout
def disconnect
return if disconnected?
begin
begin
# try to call SSL::SSLSocket#io.
@sock.io.shutdown
rescue NoMethodError
# @sock is not an SSL::SSLSocket.
@sock.shutdown
end
rescue Errno::ENOTCONN
# ignore `Errno::ENOTCONN: Socket is not connected' on some platforms.
rescue Exception => e
@receiver_thread.raise(e)
end
@receiver_thread.join
synchronize do
@sock.close
end
raise e if e
end
# Returns true if disconnected from the server.
#
# Related: #logout, #disconnect
def disconnected?
return @sock.closed?
end
# Returns whether the server supports a given +capability+. When available,
# cached #capabilities are used without sending a new #capability command to
# the server.
#
# <em>*NOTE:* Net::IMAP does not</em> currently <em>modify its behaviour
# according to the server's advertised capabilities.</em>
#
# See Net::IMAP@Capabilities for more about \IMAP capabilities.
#
# Related: #auth_capable?, #capabilities, #capability, #enable
#
def capable?(capability) capabilities.include? capability.to_s.upcase end
alias capability? capable?
# Returns the server capabilities. When available, cached capabilities are
# used without sending a new #capability command to the server.
#
# To ensure a case-insensitive comparison, #capable? can be used instead.
#
# <em>*NOTE:* Net::IMAP does not</em> currently <em>modify its behaviour
# according to the server's advertised capabilities.</em>
#
# See Net::IMAP@Capabilities for more about \IMAP capabilities.
#
# Related: #capable?, #auth_capable?, #capability
def capabilities
@capabilities || capability
end
# Returns the #authenticate mechanisms that the server claims to support.
# These are derived from the #capabilities with an <tt>AUTH=</tt> prefix.
#
# This may be different when the connection is cleartext or using TLS. Most
# servers will drop all <tt>AUTH=</tt> mechanisms from #capabilities after
# the connection has authenticated.
#
# imap = Net::IMAP.new(hostname, ssl: false)
# imap.capabilities # => ["IMAP4REV1", "LOGINDISABLED"]
# imap.auth_mechanisms # => []
#
# imap.starttls
# imap.capabilities # => ["IMAP4REV1", "AUTH=PLAIN", "AUTH=XOAUTH2",
# # "AUTH=OAUTHBEARER"]
# imap.auth_mechanisms # => ["PLAIN", "XOAUTH2", "OAUTHBEARER"]
#
# imap.authenticate("XOAUTH2", username, oauth2_access_token)
# imap.auth_mechanisms # => []
#
# <em>*NOTE:* Net::IMAP does not</em> currently <em>modify its behaviour
# according to the server's advertised capabilities.</em>
#
# See Net::IMAP@Capabilities for more about \IMAP capabilities.
#
# Related: #auth_capable?, #capabilities
#
def auth_mechanisms
capabilities
.grep(/\AAUTH=/i)
.map { _1.delete_prefix("AUTH=") }
end
# Returns whether the server supports a given SASL +mechanism+ for use with
# the #authenticate command. The +mechanism+ is supported when
# #capabilities includes <tt>"AUTH=#{mechanism.to_s.upcase}"</tt>. When
# available, cached capabilities are used without sending a new #capability
# command to the server.
#
# imap.capable? "AUTH=PLAIN" # => true
# imap.auth_capable? "PLAIN" # => true
# imap.auth_capable? "blurdybloop" # => false
#
# <em>*NOTE:* Net::IMAP does not</em> currently <em>modify its behaviour
# according to the server's advertised capabilities.</em>
#
# See Net::IMAP@Capabilities for more about \IMAP capabilities.
#
# Related: #authenticate, #capable?, #capabilities
def auth_capable?(mechanism)
capable? "AUTH=#{mechanism}"
end
# Returns whether capabilities have been cached. When true, #capable? and
# #capabilities don't require sending a #capability command to the server.
#
# See Net::IMAP@Capabilities for more about \IMAP capabilities.
#
# Related: #capable?, #capability, #clear_cached_capabilities
def capabilities_cached?
!!@capabilities
end
# Clears capabilities that have been remembered by the Net::IMAP client.
# This forces a #capability command to be sent the next time a #capabilities
# query method is called.
#
# Net::IMAP automatically discards its cached capabilities when they can
# change. Explicitly calling this _should_ be unnecessary for well-behaved
# servers.
#
# Related: #capable?, #capability, #capabilities_cached?
def clear_cached_capabilities
synchronize do
clear_responses("CAPABILITY")
@capabilities = nil
end
end
# Sends a {CAPABILITY command [IMAP4rev1 §6.1.1]}[https://www.rfc-editor.org/rfc/rfc3501#section-6.1.1]
# and returns an array of capabilities that are supported by the server.
# The result is stored for use by #capable? and #capabilities.
#
# <em>*NOTE:* Net::IMAP does not</em> currently <em>modify its behaviour
# according to the server's advertised capabilities.</em>
#
# Net::IMAP automatically stores and discards capability data according to
# the requirements and recommendations in
# {IMAP4rev2 §6.1.1}[https://www.rfc-editor.org/rfc/rfc9051#section-6.1.1],
# {§6.2}[https://www.rfc-editor.org/rfc/rfc9051#section-6.2], and
# {§7.1}[https://www.rfc-editor.org/rfc/rfc9051#section-7.1].
# Use #capable?, #auth_capable?, or #capabilities to this cache and avoid
# sending the #capability command unnecessarily.
#
# See Net::IMAP@Capabilities for more about \IMAP capabilities.
#
# Related: #capable?, #auth_capable?, #capability, #enable
def capability
synchronize do
send_command("CAPABILITY")
@capabilities = @responses.delete("CAPABILITY").last.freeze
end
end
# Sends an {ID command [RFC2971 §3.1]}[https://www.rfc-editor.org/rfc/rfc2971#section-3.1]
# and returns a hash of the server's response, or nil if the server does not
# identify itself.
#
# Note that the user should first check if the server supports the ID
# capability. For example:
#
# if capable?(:ID)
# id = imap.id(
# name: "my IMAP client (ruby)",
# version: MyIMAP::VERSION,
# "support-url": "mailto:bugs@example.com",
# os: RbConfig::CONFIG["host_os"],
# )
# end
#
# See [ID[https://tools.ietf.org/html/rfc2971]] for field definitions.
#
# ===== Capabilities
#
# The server's capabilities must include +ID+
# [RFC2971[https://tools.ietf.org/html/rfc2971]]
def id(client_id=nil)
synchronize do
send_command("ID", ClientID.new(client_id))
@responses.delete("ID")&.last
end
end
# Sends a {NOOP command [IMAP4rev1 §6.1.2]}[https://www.rfc-editor.org/rfc/rfc3501#section-6.1.2]
# to the server.
#
# This allows the server to send unsolicited untagged EXPUNGE #responses,
# but does not execute any client request. \IMAP servers are permitted to
# send unsolicited untagged responses at any time, except for `EXPUNGE`.
#
# * +EXPUNGE+ can only be sent while a command is in progress.
# * +EXPUNGE+ must _not_ be sent during #fetch, #store, or #search.
# * +EXPUNGE+ may be sent during #uid_fetch, #uid_store, or #uid_search.
#
# Related: #idle, #check
def noop
send_command("NOOP")
end
# Sends a {LOGOUT command [IMAP4rev1 §6.1.3]}[https://www.rfc-editor.org/rfc/rfc3501#section-6.1.3]
# to inform the command to inform the server that the client is done with
# the connection.
#
# Related: #disconnect
def logout
send_command("LOGOUT")
end
# Sends a {STARTTLS command [IMAP4rev1 §6.2.1]}[https://www.rfc-editor.org/rfc/rfc3501#section-6.2.1]
# to start a TLS session.
#
# Any +options+ are forwarded to OpenSSL::SSL::SSLContext#set_params.
#
# This method returns after TLS negotiation and hostname verification are
# both successful. Any error indicates that the connection has not been
# secured.
#
# *Note:*
# >>>
# Any #response_handlers added before STARTTLS should be aware that the
# TaggedResponse to STARTTLS is sent clear-text, _before_ TLS negotiation.
# TLS starts immediately _after_ that response. Any response code sent
# with the response (e.g. CAPABILITY) is insecure and cannot be trusted.
#
# Related: Net::IMAP.new, #login, #authenticate
#
# ===== Capability
# Clients should not call #starttls unless the server advertises the
# +STARTTLS+ capability.
#
# Server capabilities may change after #starttls, #login, and #authenticate.
# Cached #capabilities will be cleared when this method completes.
#
def starttls(options = {}, verify = true)
send_command("STARTTLS") do |resp|
if resp.kind_of?(TaggedResponse) && resp.name == "OK"
begin
# for backward compatibility
certs = options.to_str
options = create_ssl_params(certs, verify)
rescue NoMethodError
end
clear_cached_capabilities
clear_responses
start_tls_session(options)
end
end
end
# :call-seq:
# authenticate(mechanism, ...) -> ok_resp
# authenticate(mech, *creds, sasl_ir: true, **attrs, &callback) -> ok_resp
#
# Sends an {AUTHENTICATE command [IMAP4rev1 §6.2.2]}[https://www.rfc-editor.org/rfc/rfc3501#section-6.2.2]
# to authenticate the client. If successful, the connection enters the
# "_authenticated_" state.
#
# +mechanism+ is the name of the \SASL authentication mechanism to be used.
# +sasl_ir+ allows or disallows sending an "initial response" (see the
# +SASL-IR+ capability, below). All other arguments are forwarded to the
# registered SASL authenticator for the requested mechanism. <em>The