Add support for the Binary Content extension [RFC3516].

Unfortunately as of Debian Wheezy it doesn't work for Dovecot with
COMPRESS=DEFLATE [RFC4978] and non-synchronizing literals.

    perl -e 'use Compress::Raw::Zlib;
             print "a COMPRESS DEFLATE\r\n";
             sleep 1;
             my $d = new Compress::Raw::Zlib::Deflate( -WindowBits => -15 );
             $d->deflate("b APPEND TRASH ~{1+}\r\nx\r\n", my $buf);
             print $buf;
             $d->flush($buf, Z_SYNC_FLUSH);
             print $buf;
             sleep 1;
    ' | /usr/lib/dovecot/imap
    imap(guilhem): Panic: stream doesn't support seeking backwards

Interestingly, it works just fine for non-binary literals:

    perl -e 'use Compress::Raw::Zlib;
             print "a COMPRESS DEFLATE\r\n";
             sleep 1;
             my $d = new Compress::Raw::Zlib::Deflate( -WindowBits => -15 );
             $d->deflate("b APPEND TRASH {1+}\r\nx\r\n", my $buf);
             print $buf;
             $d->flush($buf, Z_SYNC_FLUSH);
             print $buf;
             sleep 1;
    ' | /usr/lib/dovecot/imap

However I can't reproduce the problem Dovecot 2.2.18 and Debian Sid (but
it doesn't help to install Dovecot from testing to my Wheezy box.)

1 files changed, 11 insertions, 5 deletions

diff --git a/interimap b/interimap
index af2c510..81582f2 100755
--- a/interimap
+++ b/interimap
@@ -74,6 +74,7 @@ my $CONF = read_config( delete $CONFIG{config} // $NAME
                       , 'list-mailbox' => qr/\A([\x01-\x09\x0B\x0C\x0E-\x7F]+)\z/
                       , 'list-select-opts' => qr/\A([\x21\x23\x24\x26\x27\x2B-\x5B\x5E-\x7A\x7C-\x7E]+)\z/
                       , 'ignore-mailbox' => qr/\A([\x01-\x09\x0B\x0C\x0E-\x7F]+)\z/
+                      , 'use-binary' => qr/\A(YES|NO)\z/i,
                       );
 my ($DBFILE, $LOCKFILE, $LOGGER_FD);
 
@@ -511,6 +512,10 @@ sub sync_mailbox_list() {
 
 sync_mailbox_list();
 ($lIMAP, $rIMAP) = map {$IMAP->{$_}->{client}} qw/local remote/;
+my $ATTRS = 'MODSEQ FLAGS INTERNALDATE '.
+            (((!defined $CONF->{_} or uc ($CONF->{_}->{'use-binary'} // 'YES') eq 'YES') and
+             !$lIMAP->incapable('BINARY') and !$rIMAP->incapable('BINARY'))
+                ? 'BINARY' : 'BODY').'.PEEK[]';
 
 
 #############################################################################
@@ -592,10 +597,10 @@ sub download_missing($$$@) {
     my ($buff, $bufflen) = ([], 0);
     undef $buff if ($target eq 'local' ? $lIMAP : $rIMAP)->incapable('MULTIAPPEND');
 
-    my $attrs = join ' ', qw/MODSEQ FLAGS INTERNALDATE ENVELOPE BODY.PEEK[]/;
+    my $attrs = $ATTRS.' ENVELOPE';
     ($source eq 'local' ? $lIMAP : $rIMAP)->fetch(compact_set(@set), "($attrs)", sub($) {
         my $mail = shift;
-        return unless exists $mail->{RFC822}; # not for us
+        return unless exists $mail->{RFC822} or exists $mail->{BINARY}; # not for us
 
         my $uid = $mail->{UID};
         my $from = first { defined $_ and @$_ } @{$mail->{ENVELOPE}}[2,3,4];
@@ -964,9 +969,10 @@ sub sync_known_messages($$) {
 # after the FETCH.
 sub callback_new_message($$$$;$$$) {
     my ($idx, $mailbox, $name, $mail, $UIDs, $buff, $bufflen) = @_;
-    return unless exists $mail->{RFC822}; # not for us
 
-    my $length = length $mail->{RFC822};
+    my $length = defined $mail->{RFC822} ? length($mail->{RFC822})
+               : defined $mail->{BINARY} ? length($mail->{BINARY})
+               : return; # not for us
     if ($length == 0) {
         msg("$name($mailbox)", "WARNING: Ignoring new 0-length message (UID $mail->{UID})");
         return;
@@ -1030,7 +1036,7 @@ sub sync_messages($$;$$) {
             my $bufflen = 0;
             my @tUIDs;
 
-            ($source eq 'remote' ? $rIMAP : $lIMAP)->pull_new_messages(sub($) {
+            ($source eq 'remote' ? $rIMAP : $lIMAP)->pull_new_messages($ATTRS, sub($) {
                 callback_new_message($idx, $mailbox, $source, shift, \@tUIDs, $buff, \$bufflen)
             }, @{$ignore{$source}});