From 1a6d268e1dec2ef9d68e3662c4aa10c68b3011ba Mon Sep 17 00:00:00 2001
From: Mechiel Lukkien <mechiel@ueber.net>
Date: Fri, 11 Apr 2025 18:22:29 +0200
Subject: [PATCH] imapserver: check for UIDNEXT overflow when adding a message
 to a mailbox

Return an error, with instructions so a user may be able to work around the
issue.
---
 imapserver/server.go |  8 +++++---
 store/account.go     | 14 +++++++++++++-
 webops/xops.go       |  5 +++--
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/imapserver/server.go b/imapserver/server.go
index 16e5057..c94bafe 100644
--- a/imapserver/server.go
+++ b/imapserver/server.go
@@ -4733,7 +4733,8 @@ func (c *conn) cmdxCopy(isUID bool, tag, cmd string, p *parser) {
 
 			// Reserve the uids in the destination mailbox.
 			uidFirst := mbDst.UIDNext
-			mbDst.UIDNext += store.UID(len(uids))
+			err = mbDst.UIDNextAdd(len(uids))
+			xcheckf(err, "adding uid")
 
 			// Fetch messages from database.
 			q := bstore.QueryTx[store.Message](tx)
@@ -5043,7 +5044,8 @@ func (c *conn) xmoveMessages(tx *bstore.Tx, q *bstore.Query[store.Message], expe
 		nm := om
 		nm.MailboxID = mbDst.ID
 		nm.UID = mbDst.UIDNext
-		mbDst.UIDNext++
+		err := mbDst.UIDNextAdd(1)
+		xcheckf(err, "adding uid")
 		nm.ModSeq = modseq
 		nm.CreateSeq = modseq
 		nm.SaveDate = &now
@@ -5057,7 +5059,7 @@ func (c *conn) xmoveMessages(tx *bstore.Tx, q *bstore.Query[store.Message], expe
 
 		nm.JunkFlagsForMailbox(*mbDst, accConf)
 
-		err := tx.Update(&nm)
+		err = tx.Update(&nm)
 		xcheckf(err, "updating message with new mailbox")
 
 		mbDst.Add(nm.MailboxCounts())
diff --git a/store/account.go b/store/account.go
index f80f598..2406b2b 100644
--- a/store/account.go
+++ b/store/account.go
@@ -298,6 +298,16 @@ type SpecialUse struct {
 	Trash   bool
 }
 
+// UIDNextAdd increases the UIDNext value by n, returning an error on overflow.
+func (mb *Mailbox) UIDNextAdd(n int) error {
+	uidnext := mb.UIDNext + UID(n)
+	if uidnext < mb.UIDNext {
+		return fmt.Errorf("uid overflow on mailbox %q (id %d): uidnext %d, adding %d; consider recreating the mailbox and copying its messages to compact", mb.Name, mb.ID, mb.UIDNext, n)
+	}
+	mb.UIDNext = uidnext
+	return nil
+}
+
 // CalculateCounts calculates the full current counts for messages in the mailbox.
 func (mb *Mailbox) CalculateCounts(tx *bstore.Tx) (mc MailboxCounts, err error) {
 	q := bstore.QueryTx[Message](tx)
@@ -2218,7 +2228,9 @@ func (a *Account) MessageAdd(log mlog.Log, tx *bstore.Tx, mb *Mailbox, m *Messag
 	}
 	if m.UID == 0 {
 		m.UID = mb.UIDNext
-		mb.UIDNext++
+		if err := mb.UIDNextAdd(1); err != nil {
+			return fmt.Errorf("adding uid: %v", err)
+		}
 	}
 	if m.ModSeq == 0 {
 		modseq, err := a.NextModSeq(tx)
diff --git a/webops/xops.go b/webops/xops.go
index b089eab..cf7c154 100644
--- a/webops/xops.go
+++ b/webops/xops.go
@@ -473,7 +473,8 @@ func (x XOps) MessageMoveTx(ctx context.Context, log mlog.Log, acc *store.Accoun
 		nm := om
 		nm.MailboxID = mbDst.ID
 		nm.UID = mbDst.UIDNext
-		mbDst.UIDNext++
+		err := mbDst.UIDNextAdd(1)
+		x.Checkf(ctx, err, "adding uid")
 		nm.ModSeq = *modseq
 		nm.CreateSeq = *modseq
 		nm.SaveDate = &now
@@ -490,7 +491,7 @@ func (x XOps) MessageMoveTx(ctx context.Context, log mlog.Log, acc *store.Accoun
 
 		nm.JunkFlagsForMailbox(mbDst, accConf)
 
-		err := tx.Update(&nm)
+		err = tx.Update(&nm)
 		x.Checkf(ctx, err, "updating message with new mailbox")
 
 		mbDst.Add(nm.MailboxCounts())