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imapserver: allow creating mailboxes with characters &#*%, and encode mailbox names in imap with imaputf7 when needed

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the imapserver started with imap4rev2-only and utf8=only.  to prevent potential
issues with imaputf7, which makes "&" special, we refused any mailbox with an
"&" in the name. we already tried decoding utf7, falling back to using a
mailbox name verbatim. that behaviour wasn't great. we now treat the enabled
extensions IMAP4rev2 and/or UTF8=ACCEPT as indication whether mailbox names are
in imaputf7. if they are, the encoding must be correct.

we now also send mailbox names in imaputf7 when imap4rev2/utf8=accept isn't
enabled.

and we now allow "*" and "%" (wildcard characters for matching) in mailbox
names. not ideal for IMAP LIST with patterns, but not enough reason to refuse
them in mailbox names. people that migrate may run into this, possibly as
blocker.

we also allow "#" in mailbox names, but not as first character, to prevent
potential clashes with IMAP namespaces in the future.

based on report from Damian Poddebniak using
https://github.com/duesee/imap-flow and issue #110, thanks for reporting!
This commit is contained in:
Mechiel Lukkien
2024-01-01 13:15:25 +01:00
parent a9940f9855
commit d84c96eca5
7 changed files with 150 additions and 51 deletions
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36
imapserver/server.go
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@ -13,12 +13,9 @@ LIST-EXTENDED, SPECIAL-USE, MOVE, UTF8=ONLY.
We take a liberty with UTF8=ONLY. We are supposed to wait for ENABLE of
UTF8=ACCEPT or IMAP4rev2 before we respond with quoted strings that contain
non-ASCII UTF-8. But we will unconditionally accept UTF-8 at the moment. See
non-ASCII UTF-8. Until that's enabled, we do use UTF-7 for mailbox names. See
../rfc/6855:251
We always respond with utf8 mailbox names. We do parse utf7 (only in IMAP4rev1,
not in IMAP4rev2). ../rfc/3501:964
- We never execute multiple commands at the same time for a connection. We expect a client to open multiple connections instead. ../rfc/9051:1110
- Do not write output on a connection with an account lock held. Writing can block, a slow client could block account operations.
- When handling commands that modify the selected mailbox, always check that the mailbox is not opened readonly. And always revalidate the selected mailbox, another session may have deleted the mailbox.
@ -161,7 +158,7 @@ var authFailDelay = time.Second // After authentication failure.
// TLS. The client should not be selecting PLUS variants on non-TLS connections,
// instead opting to do the bare SCRAM variant without indicating the server claims
// to support the PLUS variant (skipping the server downgrade detection check).
const serverCapabilities = "IMAP4rev2 IMAP4rev1 ENABLE LITERAL+ IDLE SASL-IR BINARY UNSELECT UIDPLUS ESEARCH SEARCHRES MOVE UTF8=ONLY LIST-EXTENDED SPECIAL-USE LIST-STATUS AUTH=SCRAM-SHA-256-PLUS AUTH=SCRAM-SHA-256 AUTH=SCRAM-SHA-1-PLUS AUTH=SCRAM-SHA-1 AUTH=CRAM-MD5 ID APPENDLIMIT=9223372036854775807 CONDSTORE QRESYNC"
const serverCapabilities = "IMAP4rev2 IMAP4rev1 ENABLE LITERAL+ IDLE SASL-IR BINARY UNSELECT UIDPLUS ESEARCH SEARCHRES MOVE UTF8=ACCEPT LIST-EXTENDED SPECIAL-USE LIST-STATUS AUTH=SCRAM-SHA-256-PLUS AUTH=SCRAM-SHA-256 AUTH=SCRAM-SHA-1-PLUS AUTH=SCRAM-SHA-1 AUTH=CRAM-MD5 ID APPENDLIMIT=9223372036854775807 CONDSTORE QRESYNC"
type conn struct {
cid int64
@ -387,6 +384,13 @@ func (c *conn) utf8strings() bool {
return c.enabled[capIMAP4rev2] || c.enabled[capUTF8Accept]
}
func (c *conn) encodeMailbox(s string) string {
if c.utf8strings() {
return s
}
return utf7encode(s)
}
func (c *conn) xdbwrite(fn func(tx *bstore.Tx)) {
err := c.account.DB.Write(context.TODO(), func(tx *bstore.Tx) error {
fn(tx)
@ -1311,19 +1315,19 @@ func (c *conn) applyChanges(changes []store.Change, initial bool) {
// unrecognized \NonExistent and interpret this as a newly created mailbox, while
// the goal was to remove it...
if c.enabled[capIMAP4rev2] {
c.bwritelinef(`* LIST (\NonExistent) "/" %s`, astring(ch.Name).pack(c))
c.bwritelinef(`* LIST (\NonExistent) "/" %s`, astring(c.encodeMailbox(ch.Name)).pack(c))
}
case store.ChangeAddMailbox:
c.bwritelinef(`* LIST (%s) "/" %s`, strings.Join(ch.Flags, " "), astring(ch.Mailbox.Name).pack(c))
c.bwritelinef(`* LIST (%s) "/" %s`, strings.Join(ch.Flags, " "), astring(c.encodeMailbox(ch.Mailbox.Name)).pack(c))
case store.ChangeRenameMailbox:
// OLDNAME only with IMAP4rev2 or NOTIFY ../rfc/9051:2726 ../rfc/5465:628
var oldname string
if c.enabled[capIMAP4rev2] {
oldname = fmt.Sprintf(` ("OLDNAME" (%s))`, string0(ch.OldName).pack(c))
oldname = fmt.Sprintf(` ("OLDNAME" (%s))`, string0(c.encodeMailbox(ch.OldName)).pack(c))
}
c.bwritelinef(`* LIST (%s) "/" %s%s`, strings.Join(ch.Flags, " "), astring(ch.NewName).pack(c), oldname)
c.bwritelinef(`* LIST (%s) "/" %s%s`, strings.Join(ch.Flags, " "), astring(c.encodeMailbox(ch.NewName)).pack(c), oldname)
case store.ChangeAddSubscription:
c.bwritelinef(`* LIST (%s) "/" %s`, strings.Join(append([]string{`\Subscribed`}, ch.Flags...), " "), astring(ch.Name).pack(c))
c.bwritelinef(`* LIST (%s) "/" %s`, strings.Join(append([]string{`\Subscribed`}, ch.Flags...), " "), astring(c.encodeMailbox(ch.Name)).pack(c))
default:
panic(fmt.Sprintf("internal error, missing case for %#v", change))
}
@ -2041,7 +2045,7 @@ func (c *conn) cmdSelectExamine(isselect bool, tag, cmd string, p *parser) {
}
c.bwritelinef(`* OK [UIDVALIDITY %d] x`, mb.UIDValidity)
c.bwritelinef(`* OK [UIDNEXT %d] x`, mb.UIDNext)
c.bwritelinef(`* LIST () "/" %s`, astring(mb.Name).pack(c))
c.bwritelinef(`* LIST () "/" %s`, astring(c.encodeMailbox(mb.Name)).pack(c))
if c.enabled[capCondstore] {
// ../rfc/7162:417
// ../rfc/7162-eid5055 ../rfc/7162:484 ../rfc/7162:1167
@ -2239,9 +2243,9 @@ func (c *conn) cmdCreate(tag, cmd string, p *parser) {
var oldname string
// OLDNAME only with IMAP4rev2 or NOTIFY ../rfc/9051:2726 ../rfc/5465:628
if c.enabled[capIMAP4rev2] && n == name && name != origName && !(name == "Inbox" || strings.HasPrefix(name, "Inbox/")) {
oldname = fmt.Sprintf(` ("OLDNAME" (%s))`, string0(origName).pack(c))
oldname = fmt.Sprintf(` ("OLDNAME" (%s))`, string0(c.encodeMailbox(origName)).pack(c))
}
c.bwritelinef(`* LIST (\Subscribed) "/" %s%s`, astring(n).pack(c), oldname)
c.bwritelinef(`* LIST (\Subscribed) "/" %s%s`, astring(c.encodeMailbox(n)).pack(c), oldname)
}
c.ok(tag, cmd)
}
@ -2526,7 +2530,7 @@ func (c *conn) cmdLsub(tag, cmd string, p *parser) {
continue
}
have[name] = true
line := fmt.Sprintf(`* LSUB () "/" %s`, astring(name).pack(c))
line := fmt.Sprintf(`* LSUB () "/" %s`, astring(c.encodeMailbox(name)).pack(c))
lines = append(lines, line)
}
@ -2541,7 +2545,7 @@ func (c *conn) cmdLsub(tag, cmd string, p *parser) {
if have[mb.Name] || !subscribedKids[mb.Name] || !re.MatchString(mb.Name) {
return nil
}
line := fmt.Sprintf(`* LSUB (\NoSelect) "/" %s`, astring(mb.Name).pack(c))
line := fmt.Sprintf(`* LSUB (\NoSelect) "/" %s`, astring(c.encodeMailbox(mb.Name)).pack(c))
lines = append(lines, line)
return nil
})
@ -2639,7 +2643,7 @@ func (c *conn) xstatusLine(tx *bstore.Tx, mb store.Mailbox, attrs []string) stri
xsyntaxErrorf("unknown attribute %q", a)
}
}
return fmt.Sprintf("* STATUS %s (%s)", astring(mb.Name).pack(c), strings.Join(status, " "))
return fmt.Sprintf("* STATUS %s (%s)", astring(c.encodeMailbox(mb.Name)).pack(c), strings.Join(status, " "))
}
func flaglist(fl store.Flags, keywords []string) listspace {