From 027274e2e832817e98adcad005a2536c46cc09b4 Mon Sep 17 00:00:00 2001
From: Leander Beernaert <leander.beernaert@proton.ch>
Date: Wed, 7 Jun 2023 10:17:37 +0200
Subject: [PATCH] fix(GODT-2683): Reduce validation checks when appending into
 Drafts

---
 internal/session/handle_append.go | 19 +++++++++++++----
 internal/state/mailbox.go         | 10 +++++++++
 rfc5322/validation.go             | 24 ++++++++++++++++++++++
 tests/append_test.go              | 34 +++++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 4 deletions(-)

diff --git a/internal/session/handle_append.go b/internal/session/handle_append.go
index 5b3b0426..ded5197e 100644
--- a/internal/session/handle_append.go
+++ b/internal/session/handle_append.go
@@ -26,11 +26,22 @@ func (s *Session) handleAppend(ctx context.Context, tag string, cmd *command.App
 		return response.Bad(tag).WithError(err)
 	}
 
-	if err := rfc5322.ValidateMessageHeaderFields(cmd.Literal); err != nil {
-		return response.Bad(tag).WithError(err)
-	}
-
 	if err := s.state.AppendOnlyMailbox(ctx, nameUTF8, func(mailbox state.AppendOnlyMailbox, isSameMBox bool) error {
+		isDrafts, err := mailbox.IsDrafts(ctx)
+		if err != nil {
+			return err
+		}
+
+		if !isDrafts {
+			if err := rfc5322.ValidateMessageHeaderFields(cmd.Literal); err != nil {
+				return response.Bad(tag).WithError(err)
+			}
+		} else {
+			if err := rfc5322.ValidateMessageHeaderFieldsDrafts(cmd.Literal); err != nil {
+				return response.Bad(tag).WithError(err)
+			}
+		}
+
 		messageUID, err := mailbox.Append(ctx, cmd.Literal, flags, cmd.DateTime)
 		if err != nil {
 			if shouldReportIMAPCommandError(err) {
diff --git a/internal/state/mailbox.go b/internal/state/mailbox.go
index 3746584e..92316c0d 100644
--- a/internal/state/mailbox.go
+++ b/internal/state/mailbox.go
@@ -37,6 +37,7 @@ type AppendOnlyMailbox interface {
 	Append(ctx context.Context, literal []byte, flags imap.FlagSet, date time.Time) (imap.UID, error)
 	Flush(ctx context.Context, permitExpunge bool) ([]response.Response, error)
 	UIDValidity() imap.UID
+	IsDrafts(ctx context.Context) (bool, error)
 }
 
 func newMailbox(mbox *db.Mailbox, state *State, snap *snapshot) *Mailbox {
@@ -251,6 +252,15 @@ func (m *Mailbox) Append(ctx context.Context, literal []byte, flags imap.FlagSet
 	return uid, err
 }
 
+func (m *Mailbox) IsDrafts(ctx context.Context) (bool, error) {
+	attrs, err := m.Attributes(ctx)
+	if err != nil {
+		return false, err
+	}
+
+	return attrs.Contains(imap.AttrDrafts), nil
+}
+
 // Copy copies the messages represented by the given sequence set into the mailbox with the given name.
 // If the context is a UID context, the sequence set refers to message UIDs.
 // If no items are copied the response object will be nil.
diff --git a/rfc5322/validation.go b/rfc5322/validation.go
index 136b2d99..a0c765b5 100644
--- a/rfc5322/validation.go
+++ b/rfc5322/validation.go
@@ -72,3 +72,27 @@ func ValidateMessageHeaderFields(literal []byte) error {
 
 	return nil
 }
+
+// ValidateMessageHeaderFieldsDrafts checks the headers of message to verify that at least a valid From header is
+// present.
+func ValidateMessageHeaderFieldsDrafts(literal []byte) error {
+	headerBytes, _ := rfc822.Split(literal)
+
+	header, err := rfc822.NewHeader(headerBytes)
+	if err != nil {
+		return err
+	}
+
+	// Check for from.
+	value := header.Get("From")
+	if len(value) == 0 {
+		return fmt.Errorf("%w: Required header field 'From' not found or empty", ErrInvalidMessage)
+	}
+
+	// Check if From is a multi address. If so, a sender filed must be present and non-empty.
+	if _, err := ParseAddressList(value); err != nil {
+		return fmt.Errorf("%w: failed to parse From header: %v", ErrInvalidMessage, err)
+	}
+
+	return nil
+}
diff --git a/tests/append_test.go b/tests/append_test.go
index 2585910c..4001ecb6 100644
--- a/tests/append_test.go
+++ b/tests/append_test.go
@@ -449,3 +449,37 @@ func TestGODT2007AppendInternalIDPresentOnDeletedMessage(t *testing.T) {
 		}
 	})
 }
+
+func TestAppendIntoDraftsWithFromOnly(t *testing.T) {
+	const (
+		literalWithFrom    = `From: Foo@bar`
+		literalWithoutFrom = `To: Foo@bar`
+		literalValid       = `From: Foo@bar
+Date: Wed, 26 Apr 2023 08:25:16 +0200
+`
+	)
+
+	runOneToOneTestClientWithAuth(t, defaultServerOptions(t), func(client *client.Client, s *testSession) {
+
+		s.mailboxCreatedWithAttributes("user", []string{"Drafts"}, imap.NewFlagSet(imap.AttrDrafts))
+		s.flush("user")
+
+		{
+			require.NoError(t, doAppendWithClient(client, "Drafts", literalWithFrom, time.Now()))
+			require.NoError(t, doAppendWithClient(client, "INBOX", literalValid, time.Now()))
+			require.Error(t, doAppendWithClient(client, "Drafts", literalWithoutFrom, time.Now()))
+			require.Error(t, doAppendWithClient(client, "INBOX", literalWithoutFrom, time.Now()))
+		}
+
+		{
+			status, err := client.Status("Drafts", []goimap.StatusItem{goimap.StatusMessages})
+			require.NoError(t, err)
+			require.Equal(t, uint32(1), status.Messages, "Expected message count does not match")
+		}
+		{
+			status, err := client.Status("INBOX", []goimap.StatusItem{goimap.StatusMessages})
+			require.NoError(t, err)
+			require.Equal(t, uint32(1), status.Messages, "Expected message count does not match")
+		}
+	})
+}