Add Matrix username spoofing (#1875)

* Matrix username spoofing

* Add config sample

2 files changed, 36 insertions, 12 deletions

diff --git a/bridge/matrix/helpers.go b/bridge/matrix/helpers.go
index b8e848a2..5a91f748 100644
--- a/bridge/matrix/helpers.go
+++ b/bridge/matrix/helpers.go
@@ -51,7 +51,7 @@ func interface2Struct(in interface{}, out interface{}) error {
 	return json.Unmarshal(jsonObj, out)
 }
 
-// getDisplayName retrieves the displayName for mxid, querying the homserver if the mxid is not in the cache.
+// getDisplayName retrieves the displayName for mxid, querying the homeserver if the mxid is not in the cache.
 func (b *Bmatrix) getDisplayName(mxid string) string {
 	if b.GetBool("UseUserName") {
 		return mxid[1:]
diff --git a/bridge/matrix/matrix.go b/bridge/matrix/matrix.go
index 702f4c8d..49fc33b3 100644
--- a/bridge/matrix/matrix.go
+++ b/bridge/matrix/matrix.go
@@ -148,12 +148,37 @@ func (b *Bmatrix) Send(msg config.Message) (string, error) {
 
 	username := newMatrixUsername(msg.Username)
 
+	body := username.plain + msg.Text
+	formattedBody := username.formatted + helper.ParseMarkdown(msg.Text)
+
+	if b.GetBool("SpoofUsername") {
+		// https://spec.matrix.org/v1.3/client-server-api/#mroommember
+		type stateMember struct {
+			AvatarURL   string `json:"avatar_url,omitempty"`
+			DisplayName string `json:"displayname"`
+			Membership  string `json:"membership"`
+		}
+
+		// TODO: reset username afterwards with DisplayName: null ?
+		m := stateMember{
+			AvatarURL:   "",
+			DisplayName: username.plain,
+			Membership:  "join",
+		}
+
+		_, err := b.mc.SendStateEvent(channel, "m.room.member", b.UserID, m)
+		if err == nil {
+			body = msg.Text
+			formattedBody = helper.ParseMarkdown(msg.Text)
+		}
+	}
+
 	// Make a action /me of the message
 	if msg.Event == config.EventUserAction {
 		m := matrix.TextMessage{
 			MsgType:       "m.emote",
-			Body:          username.plain + msg.Text,
-			FormattedBody: username.formatted + helper.ParseMarkdown(msg.Text),
+			Body:          body,
+			FormattedBody: formattedBody,
 			Format:        "org.matrix.custom.html",
 		}
 
@@ -224,10 +249,10 @@ func (b *Bmatrix) Send(msg config.Message) (string, error) {
 	if msg.ID != "" {
 		rmsg := EditedMessage{
 			TextMessage: matrix.TextMessage{
-				Body:          username.plain + msg.Text,
+				Body:          body,
 				MsgType:       "m.text",
 				Format:        "org.matrix.custom.html",
-				FormattedBody: username.formatted + helper.ParseMarkdown(msg.Text),
+				FormattedBody: formattedBody,
 			},
 		}
 
@@ -266,8 +291,8 @@ func (b *Bmatrix) Send(msg config.Message) (string, error) {
 	if msg.Event == config.EventJoinLeave {
 		m := matrix.TextMessage{
 			MsgType:       "m.notice",
-			Body:          username.plain + msg.Text,
-			FormattedBody: username.formatted + msg.Text,
+			Body:          body,
+			FormattedBody: formattedBody,
 			Format:        "org.matrix.custom.html",
 		}
 
@@ -297,8 +322,8 @@ func (b *Bmatrix) Send(msg config.Message) (string, error) {
 		m := ReplyMessage{
 			TextMessage: matrix.TextMessage{
 				MsgType:       "m.text",
-				Body:          username.plain + msg.Text,
-				FormattedBody: username.formatted + helper.ParseMarkdown(msg.Text),
+				Body:          body,
+				FormattedBody: formattedBody,
 				Format:        "org.matrix.custom.html",
 			},
 		}
@@ -338,7 +363,7 @@ func (b *Bmatrix) Send(msg config.Message) (string, error) {
 		)
 
 		err = b.retry(func() error {
-			resp, err = b.mc.SendText(channel, username.plain+msg.Text)
+			resp, err = b.mc.SendText(channel, body)
 
 			return err
 		})
@@ -356,8 +381,7 @@ func (b *Bmatrix) Send(msg config.Message) (string, error) {
 	)
 
 	err = b.retry(func() error {
-		resp, err = b.mc.SendFormattedText(channel, username.plain+msg.Text,
-			username.formatted+helper.ParseMarkdown(msg.Text))
+		resp, err = b.mc.SendFormattedText(channel, body, formattedBody)
 
 		return err
 	})