+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+#
+# Each instance of this represents an IMAP client connected to
+# public-inbox-imapd. Much of this was taken from NNTP, but
+# further refined while experimenting on future ideas to handle
+# slow storage.
+#
+# data notes:
+# * NNTP article numbers are UIDs and message sequence numbers (MSNs)
+# * Message sequence numbers (MSNs) can be stable since we're read-only.
+# Most IMAP clients use UIDs (I hope), and we can return a dummy
+# message if a client requests a non-existent MSN.
+
+package PublicInbox::IMAP;
+use strict;
+use base qw(PublicInbox::DS);
+use fields qw(imapd logged_in ibx long_cb -login_tag);
+use PublicInbox::Eml;
+use PublicInbox::DS qw(now);
+use PublicInbox::Syscall qw(EPOLLIN EPOLLONESHOT);
+use Errno qw(EAGAIN);
+my $Address;
+for my $mod (qw(Email::Address::XS Mail::Address)) {
+ eval "require $mod" or next;
+ $Address = $mod and last;
+}
+die "neither Email::Address::XS nor Mail::Address loaded: $@" if !$Address;
+
+sub LINE_MAX () { 512 } # does RFC 3501 have a limit like RFC 977?
+
+my %FETCH_NEED_BLOB = ( # for future optimization
+ 'BODY.PEEK[HEADER]' => 1,
+ 'BODY.PEEK[TEXT]' => 1,
+ 'BODY.PEEK[]' => 1,
+ 'BODY[HEADER]' => 1,
+ 'BODY[TEXT]' => 1,
+ 'BODY[]' => 1,
+ 'RFC822.HEADER' => 1,
+ 'RFC822.SIZE' => 1, # needs CRLF conversion :<
+ 'RFC822.TEXT' => 1,
+ BODY => 1,
+ BODYSTRUCTURE => 1,
+ ENVELOPE => 1,
+ FLAGS => 0,
+ INTERNALDATE => 0,
+ RFC822 => 1,
+ UID => 0,
+);
+my %FETCH_ATT = map { $_ => [ $_ ] } keys %FETCH_NEED_BLOB;
+
+# aliases (RFC 3501 section 6.4.5)
+$FETCH_ATT{FAST} = [ qw(FLAGS INTERNALDATE RFC822.SIZE) ];
+$FETCH_ATT{ALL} = [ @{$FETCH_ATT{FAST}}, 'ENVELOPE' ];
+$FETCH_ATT{FULL} = [ @{$FETCH_ATT{ALL}}, 'BODY' ];
+
+for my $att (keys %FETCH_ATT) {
+ my %h = map { $_ => 1 } @{$FETCH_ATT{$att}};
+ $FETCH_ATT{$att} = \%h;
+}
+
+sub greet ($) {
+ my ($self) = @_;
+ my $capa = capa($self);
+ $self->write(\"* OK [$capa] public-inbox-imapd ready\r\n");
+}
+
+sub new ($$$) {
+ my ($class, $sock, $imapd) = @_;
+ my $self = fields::new($class);
+ my $ev = EPOLLIN;
+ my $wbuf;
+ if ($sock->can('accept_SSL') && !$sock->accept_SSL) {
+ return CORE::close($sock) if $! != EAGAIN;
+ $ev = PublicInbox::TLS::epollbit();
+ $wbuf = [ \&PublicInbox::DS::accept_tls_step, \&greet ];
+ }
+ $self->SUPER::new($sock, $ev | EPOLLONESHOT);
+ $self->{imapd} = $imapd;
+ if ($wbuf) {
+ $self->{wbuf} = $wbuf;
+ } else {
+ greet($self);
+ }
+ $self->update_idle_time;
+ $self;
+}
+
+sub capa ($) {
+ my ($self) = @_;
+ my $capa = 'CAPABILITY IMAP4rev1';
+ if ($self->{logged_in}) {
+ $capa .= ' COMPRESS=DEFLATE';
+ } else {
+ if (!($self->{sock} // $self)->can('accept_SSL') &&
+ $self->{imapd}->{accept_tls}) {
+ $capa .= ' STARTTLS';
+ }
+ $capa .= ' AUTH=ANONYMOUS';
+ }
+}
+
+sub login_success ($$) {
+ my ($self, $tag) = @_;
+ $self->{logged_in} = 1;
+ my $capa = capa($self);
+ "$tag OK [$capa] Logged in\r\n";
+}
+
+sub auth_challenge_ok ($) {
+ my ($self) = @_;
+ my $tag = delete($self->{-login_tag}) or return;
+ login_success($self, $tag);
+}
+
+sub cmd_login ($$$$) {
+ my ($self, $tag) = @_; # ignore ($user, $password) = ($_[2], $_[3])
+ login_success($self, $tag);
+}
+
+sub cmd_logout ($$) {
+ my ($self, $tag) = @_;
+ delete $self->{logged_in};
+ $self->write(\"* BYE logging out\r\n$tag OK logout completed\r\n");
+ $self->shutdn; # PublicInbox::DS::shutdn
+ undef;
+}
+
+sub cmd_authenticate ($$$) {
+ my ($self, $tag) = @_; # $method = $_[2], should be "ANONYMOUS"
+ $self->{-login_tag} = $tag;
+ "+\r\n"; # challenge
+}
+
+sub cmd_capability ($$) {
+ my ($self, $tag) = @_;
+ '* '.capa($self)."\r\n$tag OK\r\n";
+}
+
+sub cmd_noop ($$) { "$_[1] OK NOOP completed\r\n" }
+
+sub cmd_examine ($$$) {
+ my ($self, $tag, $mailbox) = @_;
+ my $ibx = $self->{imapd}->{groups}->{$mailbox} or
+ return "$tag NO Mailbox doesn't exist: $mailbox\r\n";
+ my $mm = $ibx->mm;
+ my $max = $mm->num_highwater // 0;
+ # RFC 3501 2.3.1.1 - "A good UIDVALIDITY value to use in
+ # this case is a 32-bit representation of the creation
+ # date/time of the mailbox"
+ my $uidvalidity = $mm->created_at or return "$tag BAD UIDVALIDITY\r\n";
+ my $uidnext = $max + 1;
+
+ # XXX: do we need this? RFC 5162/7162
+ my $ret = $self->{ibx} ? "* OK [CLOSED] previous closed\r\n" : '';
+ $self->{ibx} = $ibx;
+ $ret .= <<EOF;
+* $max EXISTS\r
+* $max RECENT\r
+* FLAGS (\\Seen)\r
+* OK [PERMANENTFLAGS ()] Read-only mailbox\r
+EOF
+ $ret .= "* OK [UNSEEN $max]\r\n" if $max;
+ $ret .= "* OK [UIDNEXT $uidnext]\r\n" if defined $uidnext;
+ $ret .= "* OK [UIDVALIDITY $uidvalidity]\r\n" if defined $uidvalidity;
+ $ret .= "$tag OK [READ-ONLY] EXAMINE/SELECT complete\r\n";
+}
+
+sub _esc ($) {
+ my ($v) = @_;
+ if (!defined($v)) {
+ 'NIL';
+ } elsif ($v =~ /[{"\r\n%*\\\[]/) { # literal string
+ '{' . length($v) . "}\r\n" . $v;
+ } else { # quoted string
+ qq{"$v"}
+ }
+}
+
+sub addr_envelope ($$;$) {
+ my ($eml, $x, $y) = @_;
+ my $v = $eml->header_raw($x) //
+ ($y ? $eml->header_raw($y) : undef) // return 'NIL';
+
+ my @x = $Address->parse($v) or return 'NIL';
+ '(' . join('',
+ map { '(' . join(' ',
+ _esc($_->name), 'NIL',
+ _esc($_->user), _esc($_->host)
+ ) . ')'
+ } @x) .
+ ')';
+}
+
+sub eml_envelope ($) {
+ my ($eml) = @_;
+ '(' . join(' ',
+ _esc($eml->header_raw('Date')),
+ _esc($eml->header_raw('Subject')),
+ addr_envelope($eml, 'From'),
+ addr_envelope($eml, 'Sender', 'From'),
+ addr_envelope($eml, 'Reply-To', 'From'),
+ addr_envelope($eml, 'To'),
+ addr_envelope($eml, 'Cc'),
+ addr_envelope($eml, 'Bcc'),
+ _esc($eml->header_raw('In-Reply-To')),
+ _esc($eml->header_raw('Message-ID')),
+ ) . ')';
+}
+
+sub uid_fetch_cb { # called by git->cat_async
+ my ($bref, $oid, $type, $size, $fetch_m_arg) = @_;
+ my ($self, undef, $ibx, undef, undef, $msgs, $want) = @$fetch_m_arg;
+ my $smsg = shift @$msgs or die 'BUG: no smsg';
+ $smsg->{blob} eq $oid or die "BUG: $smsg->{blob} != $oid";
+ $$bref =~ s/(?<!\r)\n/\r\n/sg; # make strict clients happy
+
+ # fixup old bug from import (pre-a0c07cba0e5d8b6a)
+ $$bref =~ s/\A[\r\n]*From [^\r\n]*\r\n//s;
+
+ $self->msg_more("* $smsg->{num} FETCH (UID $smsg->{num}");
+
+ $want->{'RFC822.SIZE'} and
+ $self->msg_more(' RFC822.SIZE '.length($$bref));
+ $want->{INTERNALDATE} and
+ $self->msg_more(' INTERNALDATE "'.$smsg->internaldate.'"');
+ $want->{FLAGS} and $self->msg_more(' FLAGS ()');
+ for ('RFC822', 'BODY[]', 'BODY.PEEK[]') {
+ next unless $want->{$_};
+ $self->msg_more(" $_ {".length($$bref)."}\r\n");
+ $self->msg_more($$bref);
+ }
+
+ my $eml = PublicInbox::Eml->new($bref);
+
+ $want->{ENVELOPE} and
+ $self->msg_more(' ENVELOPE '.eml_envelope($eml));
+
+ for my $f ('RFC822.HEADER', 'BODY[HEADER]', 'BODY.PEEK[HEADER]') {
+ next unless $want->{$f};
+ $self->msg_more(" $f {".length(${$eml->{hdr}})."}\r\n");
+ $self->msg_more(${$eml->{hdr}});
+ }
+ for my $f ('RFC822.TEXT', 'BODY[TEXT]') {
+ next unless $want->{$f};
+ $self->msg_more(" $f {".length($$bref)."}\r\n");
+ $self->msg_more($$bref);
+ }
+ # TODO BODY/BODYSTRUCTURE, specific headers
+ $self->msg_more(")\r\n");
+}
+
+sub uid_fetch_m { # long_response
+ my ($self, $tag, $ibx, $beg, $end, $msgs, $want) = @_;
+ if (!@$msgs) { # refill
+ @$msgs = @{$ibx->over->query_xover($$beg, $end)};
+ if (!@$msgs) {
+ $self->write(\"$tag OK Fetch done\r\n");
+ return;
+ }
+ $$beg = $msgs->[-1]->{num} + 1;
+ }
+ my $git = $ibx->git;
+ $git->cat_async_begin; # TODO: actually make async
+ $git->cat_async($msgs->[0]->{blob}, \&uid_fetch_cb, \@_);
+ $git->cat_async_wait;
+ 1;
+}
+
+sub cmd_uid_fetch ($$$;@) {
+ my ($self, $tag, $range, @want) = @_;
+ my $ibx = $self->{ibx} or return "$tag BAD No mailbox selected\r\n";
+ if ($want[0] =~ s/\A\(//s) {
+ $want[-1] =~ s/\)\z//s or return "$tag BAD no rparen\r\n";
+ }
+ my %want = map {;
+ my $x = $FETCH_ATT{uc($_)} or return "$tag BAD param: $_\r\n";
+ %$x;
+ } @want;
+ my ($beg, $end);
+ my $msgs = [];
+ if ($range =~ /\A([0-9]+):([0-9]+)\z/s) {
+ ($beg, $end) = ($1, $2);
+ } elsif ($range =~ /\A([0-9]+):\*\z/s) {
+ ($beg, $end) = ($1, $ibx->mm->num_highwater // 0);
+ } elsif ($range =~ /\A[0-9]+\z/) {
+ my $smsg = $ibx->over->get_art($range) or return "$tag OK\r\n";
+ push @$msgs, $smsg;
+ ($beg, $end) = ($range, 0);
+ } else {
+ return "$tag BAD\r\n";
+ }
+ long_response($self, \&uid_fetch_m, $tag, $ibx,
+ \$beg, $end, $msgs, \%want);
+}
+
+sub uid_search_all { # long_response
+ my ($self, $tag, $ibx, $num) = @_;
+ my $uids = $ibx->mm->ids_after($num);
+ if (scalar(@$uids)) {
+ $self->msg_more(join(' ', '', @$uids));
+ } else {
+ $self->write(\"\r\n$tag OK\r\n");
+ undef;
+ }
+}
+
+sub uid_search_uid_range { # long_response
+ my ($self, $tag, $ibx, $beg, $end) = @_;
+ my $uids = $ibx->mm->msg_range($beg, $end, 'num');
+ if (@$uids) {
+ $self->msg_more(join('', map { " $_->[0]" } @$uids));
+ } else {
+ $self->write(\"\r\n$tag OK\r\n");
+ undef;
+ }
+}
+
+sub cmd_uid_search ($$$;) {
+ my ($self, $tag, $arg, @rest) = @_;
+ my $ibx = $self->{ibx} or return "$tag BAD No mailbox selected\r\n";
+ $arg = uc($arg);
+ if ($arg eq 'ALL' && !@rest) {
+ $self->msg_more('* SEARCH');
+ my $num = 0;
+ long_response($self, \&uid_search_all, $tag, $ibx, \$num);
+ } elsif ($arg eq 'UID' && scalar(@rest) == 1) {
+ if ($rest[0] =~ /\A([0-9]+):([0-9]+|\*)\z/s) {
+ my ($beg, $end) = ($1, $2);
+ $end = ($ibx->mm->minmax)[1] if $end eq '*';
+ $self->msg_more('* SEARCH');
+ long_response($self, \&uid_search_uid_range,
+ $tag, $ibx, \$beg, $end);
+ } elsif ($rest[0] =~ /\A[0-9]+\z/s) {
+ my $uid = $rest[0];
+ $uid = $ibx->over->get_art($uid) ? " $uid" : '';
+ "* SEARCH$uid\r\n$tag OK\r\n";
+ } else {
+ "$tag BAD\r\n";
+ }
+ } else {
+ "$tag BAD\r\n";
+ }
+}
+
+sub args_ok ($$) { # duplicated from PublicInbox::NNTP
+ my ($cb, $argc) = @_;
+ my $tot = prototype $cb;
+ my ($nreq, undef) = split(';', $tot);
+ $nreq = ($nreq =~ tr/$//) - 1;
+ $tot = ($tot =~ tr/$//) - 1;
+ ($argc <= $tot && $argc >= $nreq);
+}
+
+# returns 1 if we can continue, 0 if not due to buffered writes or disconnect
+sub process_line ($$) {
+ my ($self, $l) = @_;
+ my ($tag, $req, @args) = split(/[ \t]+/, $l);
+ if (@args && uc($req) eq 'UID') {
+ $req .= "_".(shift @args);
+ }
+ my $res = eval {
+ if (my $cmd = $self->can('cmd_'.lc($req // ''))) {
+ $cmd->($self, $tag, @args);
+ } else { # this is weird
+ auth_challenge_ok($self) //
+ "$tag BAD Error in IMAP command $req: ".
+ "Unknown command\r\n";
+ }
+ };
+ my $err = $@;
+ if ($err && $self->{sock}) {
+ $l =~ s/\r?\n//s;
+ err($self, 'error from: %s (%s)', $l, $err);
+ $res = "$tag BAD program fault - command not performed\r\n";
+ }
+ return 0 unless defined $res;
+ $self->write($res);
+}
+
+sub long_step {
+ my ($self) = @_;
+ # wbuf is unset or empty, here; {long} may add to it
+ my ($fd, $cb, $t0, @args) = @{$self->{long_cb}};
+ my $more = eval { $cb->($self, @args) };
+ if ($@ || !$self->{sock}) { # something bad happened...
+ delete $self->{long_cb};
+ my $elapsed = now() - $t0;
+ if ($@) {
+ err($self,
+ "%s during long response[$fd] - %0.6f",
+ $@, $elapsed);
+ }
+ out($self, " deferred[$fd] aborted - %0.6f", $elapsed);
+ $self->close;
+ } elsif ($more) { # $self->{wbuf}:
+ $self->update_idle_time;
+
+ # COMPRESS users all share the same DEFLATE context.
+ # Flush it here to ensure clients don't see
+ # each other's data
+ $self->zflush;
+
+ # no recursion, schedule another call ASAP, but only after
+ # all pending writes are done. autovivify wbuf:
+ my $new_size = push(@{$self->{wbuf}}, \&long_step);
+
+ # wbuf may be populated by $cb, no need to rearm if so:
+ $self->requeue if $new_size == 1;
+ } else { # all done!
+ delete $self->{long_cb};
+ my $elapsed = now() - $t0;
+ my $fd = fileno($self->{sock});
+ out($self, " deferred[$fd] done - %0.6f", $elapsed);
+ my $wbuf = $self->{wbuf}; # do NOT autovivify
+
+ $self->requeue unless $wbuf && @$wbuf;
+ }
+}
+
+sub err ($$;@) {
+ my ($self, $fmt, @args) = @_;
+ printf { $self->{imapd}->{err} } $fmt."\n", @args;
+}
+
+sub out ($$;@) {
+ my ($self, $fmt, @args) = @_;
+ printf { $self->{imapd}->{out} } $fmt."\n", @args;
+}
+
+sub long_response ($$;@) {
+ my ($self, $cb, @args) = @_; # cb returns true if more, false if done
+
+ my $sock = $self->{sock} or return;
+ # make sure we disable reading during a long response,
+ # clients should not be sending us stuff and making us do more
+ # work while we are stream a response to them
+ $self->{long_cb} = [ fileno($sock), $cb, now(), @args ];
+ long_step($self); # kick off!
+ undef;
+}
+
+# callback used by PublicInbox::DS for any (e)poll (in/out/hup/err)
+sub event_step {
+ my ($self) = @_;
+
+ return unless $self->flush_write && $self->{sock};
+
+ $self->update_idle_time;
+ # only read more requests if we've drained the write buffer,
+ # otherwise we can be buffering infinitely w/o backpressure
+
+ my $rbuf = $self->{rbuf} // (\(my $x = ''));
+ my $r = 1;
+
+ if (index($$rbuf, "\n") < 0) {
+ my $off = length($$rbuf);
+ $r = $self->do_read($rbuf, LINE_MAX, $off) or return;
+ }
+ while ($r > 0 && $$rbuf =~ s/\A[ \t]*([^\n]*?)\r?\n//) {
+ my $line = $1;
+ return $self->close if $line =~ /[[:cntrl:]]/s;
+ my $t0 = now();
+ my $fd = fileno($self->{sock});
+ $r = eval { process_line($self, $line) };
+ my $pending = $self->{wbuf} ? ' pending' : '';
+ out($self, "[$fd] %s - %0.6f$pending", $line, now() - $t0);
+ }
+
+ return $self->close if $r < 0;
+ my $len = length($$rbuf);
+ return $self->close if ($len >= LINE_MAX);
+ $self->rbuf_idle($rbuf);
+ $self->update_idle_time;
+
+ # maybe there's more pipelined data, or we'll have
+ # to register it for socket-readiness notifications
+ $self->requeue unless $self->{wbuf};
+}
+
+sub compressed { undef }
+
+sub zflush {} # overridden by IMAPdeflate
+
+# RFC 4978
+sub cmd_compress ($$$) {
+ my ($self, $tag, $alg) = @_;
+ return "$tag BAD DEFLATE only\r\n" if uc($alg) ne "DEFLATE";
+ return "$tag BAD COMPRESS active\r\n" if $self->compressed;
+
+ # CRIME made TLS compression obsolete
+ # return "$tag NO [COMPRESSIONACTIVE]\r\n" if $self->tls_compressed;
+
+ PublicInbox::IMAPdeflate->enable($self, $tag);
+ $self->requeue;
+ undef
+}
+
+sub cmd_starttls ($$) {
+ my ($self, $tag) = @_;
+ my $sock = $self->{sock} or return;
+ if ($sock->can('stop_SSL') || $self->compressed) {
+ return "$tag BAD TLS or compression already enabled\r\n";
+ }
+ my $opt = $self->{imapd}->{accept_tls} or
+ return "$tag BAD can not initiate TLS negotiation\r\n";
+ $self->write(\"$tag OK begin TLS negotiation now\r\n");
+ $self->{sock} = IO::Socket::SSL->start_SSL($sock, %$opt);
+ $self->requeue if PublicInbox::DS::accept_tls_step($self);
+ undef;
+}
+
+# for graceful shutdown in PublicInbox::Daemon:
+sub busy {
+ my ($self, $now) = @_;
+ ($self->{rbuf} || $self->{wbuf} || $self->not_idle_long($now));
+}
+
+# we're read-only, so SELECT and EXAMINE do the same thing
+no warnings 'once';
+*cmd_select = \&cmd_examine;
+
+1;