From 28091364514efe0080aabad2acfdacffa14cb38f Mon Sep 17 00:00:00 2001
From: Mechiel Lukkien <mechiel@ueber.net>
Date: Sun, 23 Feb 2025 20:19:07 +0100
Subject: [PATCH] imap metadata extension: allow keys in the /shared/ namespace
 too

not just /private. /shared/ is the more commonly implemented namespace, because
it is easier te implement: you don't need per-user/account storage of metadata.
i initially approached it from the other direction: we don't have a mechanism
to share metadata with other accounts, so everything is private, and i assumed
that would be what a user would prefer. but email clients make the decisions,
and they'll likely try the /shared/ namespace.
---
 imapserver/metadata.go      | 18 ++++++++++--------
 imapserver/metadata_test.go |  7 +++++--
 store/account.go            |  4 ++--
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/imapserver/metadata.go b/imapserver/metadata.go
index 5b82a27..dbfbe42 100644
--- a/imapserver/metadata.go
+++ b/imapserver/metadata.go
@@ -181,8 +181,8 @@ func (c *conn) cmdGetmetadata(tag, cmd string, p *parser) {
 
 // Set metadata annotation, per mailbox or globally.
 //
-// We only implement private annotations, not shared annotations. We don't
-// currently have a mechanism for determining if the user should have access.
+// We allow both /private/* and /shared/*, we store them in the same way since we
+// don't have ACL extension support yet or another mechanism for access control.
 //
 // State: Authenticated and selected.
 func (c *conn) cmdSetmetadata(tag, cmd string, p *parser) {
@@ -211,20 +211,22 @@ func (c *conn) cmdSetmetadata(tag, cmd string, p *parser) {
 
 	// Additional checks on entry names.
 	for _, a := range l {
-		// We only allow /private/* entry names, so check early and fail if we see anything
-		// else (the only other option is /shared/* at this moment).
 		// ../rfc/5464:217
-		if !strings.HasPrefix(a.Key, "/private/") {
+		if !strings.HasPrefix(a.Key, "/private/") && !strings.HasPrefix(a.Key, "/shared/") {
 			// ../rfc/5464:346
-			xuserErrorf("only /private/* entry names allowed")
+			xuserErrorf("only /private/* and /shared/* entry names allowed")
 		}
 
 		// We also enforce that /private/vendor/ is followed by at least 2 elements.
 		// ../rfc/5464:234
-		if a.Key == "/private/vendor" || strings.HasPrefix(a.Key, "/private/vendor/") {
+		switch {
+		case a.Key == "/private/vendor",
+			strings.HasPrefix(a.Key, "/private/vendor/"),
+			a.Key == "/shared/vendor", strings.HasPrefix(a.Key, "/shared/vendor/"):
+
 			t := strings.SplitN(a.Key[1:], "/", 4)
 			if len(t) < 4 {
-				xuserErrorf("entry names starting with /private/vendor must have at least 4 components")
+				xuserErrorf("entry names starting with /private/vendor or /shared/vendor must have at least 4 components")
 			}
 		}
 	}
diff --git a/imapserver/metadata_test.go b/imapserver/metadata_test.go
index 87c0de8..1144b7b 100644
--- a/imapserver/metadata_test.go
+++ b/imapserver/metadata_test.go
@@ -31,16 +31,18 @@ func TestMetadata(t *testing.T) {
 		},
 	})
 
+	tc.transactf("ok", `setmetadata Inbox (/shared/comment "share")`)
+
 	tc.transactf("ok", `getmetadata inbox (/private/comment /private/unknown /shared/comment)`)
 	tc.xuntagged(imapclient.UntaggedMetadataAnnotations{
 		Mailbox: "Inbox",
 		Annotations: []imapclient.Annotation{
 			{Key: "/private/comment", IsString: true, Value: []byte("mailbox value")},
+			{Key: "/shared/comment", IsString: true, Value: []byte("share")},
 		},
 	})
 
 	tc.transactf("no", `setmetadata doesnotexist (/private/comment "test")`) // Bad mailbox.
-	tc.transactf("no", `setmetadata Inbox (/shared/comment "")`)             // /shared/ not implemented.
 	tc.transactf("no", `setmetadata Inbox (/badprefix/comment "")`)
 	tc.transactf("no", `setmetadata Inbox (/private/vendor "")`)          // /*/vendor must have more components.
 	tc.transactf("no", `setmetadata Inbox (/private/vendor/stillbad "")`) // /*/vendor must have more components.
@@ -131,7 +133,7 @@ func TestMetadata(t *testing.T) {
 		},
 	})
 	// Same as previous, but ask for everything below /.
-	tc.transactf("ok", `getmetadata (depth infinity) inbox (/)`)
+	tc.transactf("ok", `getmetadata (depth infinity) inbox ("")`)
 	tc.xuntagged(imapclient.UntaggedMetadataAnnotations{
 		Mailbox: "Inbox",
 		Annotations: []imapclient.Annotation{
@@ -142,6 +144,7 @@ func TestMetadata(t *testing.T) {
 			{Key: "/private/another", IsString: true, Value: []byte("longer")},
 			{Key: "/private/comment", IsString: false, Value: []byte("test")},
 			{Key: "/private/vendor/a/b", IsString: true, Value: []byte("")},
+			{Key: "/shared/comment", IsString: true, Value: []byte("share")},
 		},
 	})
 
diff --git a/store/account.go b/store/account.go
index f7eff1c..804c8e3 100644
--- a/store/account.go
+++ b/store/account.go
@@ -229,8 +229,8 @@ type Annotation struct {
 	// Can be zero, indicates global (per-account) annotation.
 	MailboxID int64 `bstore:"ref Mailbox,unique MailboxID+Key"`
 
-	// "Entry name", always starts with "/private/". Stored lower-case, comparisons
-	// must be done case-insensitively.
+	// "Entry name", always starts with "/private/" or "/shared/". Stored lower-case,
+	// comparisons must be done case-insensitively.
 	Key string `bstore:"nonzero"`
 
 	IsString bool // If true, the value is a string instead of bytes.