Ensure correct SSH permissions check for private and restricted users (#17370)

Repositories owned by private users and organisations and pulls by restricted users
need to have permissions checked. Previously Serv would simply assumed that if the
user could log in and the repository was not private then it would be visible.

Fix #17364

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

routers/private/serv.go

@@ -279,7 +279,12 @@ func ServCommand(ctx *context.PrivateContext) {
 	}
 
 	// Permissions checking:
-	if repoExist && (mode > models.AccessModeRead || repo.IsPrivate || setting.Service.RequireSignInView) {
+	if repoExist &&
+		(mode > models.AccessModeRead ||
+			repo.IsPrivate ||
+			owner.Visibility.IsPrivate() ||
+			user.IsRestricted ||
+			setting.Service.RequireSignInView) {
 		if key.Type == models.KeyTypeDeploy {
 			if deployKey.Mode < mode {
 				ctx.JSON(http.StatusUnauthorized, private.ErrServCommand{
@@ -289,7 +294,7 @@ func ServCommand(ctx *context.PrivateContext) {
 				return
 			}
 		} else {
-			// Because of special ref "refs/for" .. , need delay write permission check
+			// Because of the special ref "refs/for" we will need to delay write permission check
 			if git.SupportProcReceive && unitType == models.UnitTypeCode {
 				mode = models.AccessModeRead
 			}