Sanitize post for audit with preview links (#23745)

* sanitize post for audit with preview links

* add unit test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/post_metadata_test.go

@@ -2817,3 +2817,55 @@ func TestSanitizePostMetadataForUserAndChannel(t *testing.T) {
 	actual = th.App.sanitizePostMetadataForUserAndChannel(th.Context, post, previewedPost, directChannel, guest.Id)
 	assert.Nil(t, actual.Metadata.Embeds[0].Data)
 }
+
+func TestSanitizePostMetaDataForAudit(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	th.App.UpdateConfig(func(cfg *model.Config) {
+		*cfg.ServiceSettings.SiteURL = "http://mymattermost.com"
+	})
+
+	th.Context.Session().UserId = th.BasicUser.Id
+
+	referencedPost, err := th.App.CreatePost(th.Context, &model.Post{
+		UserId:    th.BasicUser.Id,
+		ChannelId: th.BasicChannel.Id,
+		Message:   "hello world",
+	}, th.BasicChannel, false, true)
+	require.Nil(t, err)
+	referencedPost.Metadata.Embeds = nil
+
+	link := fmt.Sprintf("%s/%s/pl/%s", *th.App.Config().ServiceSettings.SiteURL, th.BasicTeam.Name, referencedPost.Id)
+
+	previewPost, err := th.App.CreatePost(th.Context, &model.Post{
+		UserId:    th.BasicUser.Id,
+		ChannelId: th.BasicChannel.Id,
+		Message:   link,
+	}, th.BasicChannel, false, true)
+	require.Nil(t, err)
+	previewPost.Metadata.Embeds = nil
+	clientPost := th.App.PreparePostForClientWithEmbedsAndImages(th.Context, previewPost, false, false, false)
+	firstEmbed := clientPost.Metadata.Embeds[0]
+	preview := firstEmbed.Data.(*model.PreviewPost)
+	require.Equal(t, referencedPost.Id, preview.PostID)
+
+	// ensure the permalink metadata is sanitized for audit logging
+	m := clientPost.Auditable()
+	metaDataI, ok := m["metadata"]
+	require.True(t, ok)
+	metaData, ok := metaDataI.(map[string]any)
+	require.True(t, ok)
+	embedsI, ok := metaData["embeds"]
+	require.True(t, ok)
+	embeds, ok := embedsI.([]map[string]any)
+	require.True(t, ok)
+	for _, pe := range embeds {
+		// ensure all the PostEmbed maps only contain `type` and `url`
+		for k := range pe {
+			if k != "type" && k != "url" {
+				require.Fail(t, "PostEmbed should only contain 'type' and 'url fields'")
+			}
+		}
+	}
+}

server/public/model/post.go

@@ -120,6 +120,11 @@ type Post struct {
 }
 
 func (o *Post) Auditable() map[string]interface{} {
+	var metaData map[string]any
+	if o.Metadata != nil {
+		metaData = o.Metadata.Auditable()
+	}
+
 	return map[string]interface{}{
 		"id":              o.Id,
 		"create_at":       o.CreateAt,
@@ -139,7 +144,7 @@ func (o *Post) Auditable() map[string]interface{} {
 		"reply_count":     o.ReplyCount,
 		"last_reply_at":   o.LastReplyAt,
 		"is_following":    o.IsFollowing,
-		"metadata":        o.Metadata,
+		"metadata":        metaData,
 	}
 }
 

server/public/model/post_embed.go

@@ -23,3 +23,11 @@ type PostEmbed struct {
 	// Any additional data for the embedded content. Only used for OpenGraph embeds.
 	Data any `json:"data,omitempty"`
 }
+
+func (pe *PostEmbed) Auditable() map[string]any {
+	// filter out embedded content.
+	return map[string]any{
+		"type": pe.Type,
+		"url":  pe.URL,
+	}
+}

server/public/model/post_metadata.go

@@ -30,6 +30,26 @@ type PostMetadata struct {
 	Acknowledgements []*PostAcknowledgement `json:"acknowledgements,omitempty"`
 }
 
+func (pm *PostMetadata) Auditable() map[string]any {
+	embeds := make([]map[string]any, 0, len(pm.Embeds))
+	for _, pe := range pm.Embeds {
+		embeds = append(embeds, pe.Auditable())
+	}
+	if len(embeds) == 0 {
+		embeds = nil
+	}
+
+	return map[string]any{
+		"embeds":           embeds,
+		"emojis":           pm.Emojis,
+		"files":            pm.Files,
+		"images":           pm.Images,
+		"reactions":        pm.Reactions,
+		"priority":         pm.Priority,
+		"acknowledgements": pm.Acknowledgements,
+	}
+}
+
 type PostImage struct {
 	Width  int `json:"width"`
 	Height int `json:"height"`