Only applying angled brackets to sip: uris. (#1247)

Author: alexlivekit

livekit/sip.go

@@ -700,21 +700,29 @@ func (p *TransferSIPParticipantRequest) Validate() error {
 	}
 
 	// Validate TransferTo URI format and ensure RFC compliance
-	var uriToValidate string
+	var innerURI string
 	if strings.HasPrefix(p.TransferTo, "<") && strings.HasSuffix(p.TransferTo, ">") {
 		// Extract inner URI for validation
-		uriToValidate = p.TransferTo[1 : len(p.TransferTo)-1]
+		innerURI = p.TransferTo[1 : len(p.TransferTo)-1]
 	} else {
-		uriToValidate = p.TransferTo
+		innerURI = p.TransferTo
 	}
 
-	if !strings.HasPrefix(uriToValidate, "sip:") && !strings.HasPrefix(uriToValidate, "tel:") {
+	if !strings.HasPrefix(innerURI, "sip:") && !strings.HasPrefix(innerURI, "tel:") {
+		// In theory the Refer-To header can receive the full name-addr.
+		// This can make this check inaccurate, but we want to limit to just SIP and TEL URIs.
 		return errors.New("transfer_to must be a valid SIP or TEL URI (sip: or tel:)")
 	}
 
-	// Ensure RFC compliance by wrapping in angle brackets if not already wrapped
-	if !strings.HasPrefix(p.TransferTo, "<") || !strings.HasSuffix(p.TransferTo, ">") {
-		p.TransferTo = fmt.Sprintf("<%s>", p.TransferTo)
+	if strings.HasPrefix(innerURI, "sip:") {
+		// addr-spec = sip:...
+		// name-addr = [ display-name ] <addr-spec>
+		// Both name-addr and addr-spec are allowed in RFC3515 (section-2.1).
+		// However, name-addr is more premissive and widely-supported, so we convert.
+		p.TransferTo = fmt.Sprintf("<%s>", innerURI)
+	} else {
+		// tel: URIs are not explicitly allowed in spec, but are generally supported.
+		p.TransferTo = innerURI
 	}
 
 	if err := validateHeaderKeys(p.Headers); err != nil {

livekit/sip_test.go

@@ -387,7 +387,7 @@ func TestTransferSIPParticipantRequestValidate(t *testing.T) {
 				TransferTo:          "tel:+15105550100",
 			},
 			expectError: false,
-			expectedURI: "<tel:+15105550100>",
+			expectedURI: "tel:+15105550100",
 		},
 		{
 			name: "valid sip URI with brackets",
@@ -407,7 +407,7 @@ func TestTransferSIPParticipantRequestValidate(t *testing.T) {
 				TransferTo:          "<tel:+15105550100>",
 			},
 			expectError: false,
-			expectedURI: "<tel:+15105550100>",
+			expectedURI: "tel:+15105550100",
 		},
 		{
 			name: "invalid URI - http",
@@ -520,7 +520,7 @@ func TestTransferSIPParticipantRequestValidate(t *testing.T) {
 				TransferTo:          "tel:+1234567890;ext=123",
 			},
 			expectError: false,
-			expectedURI: "<tel:+1234567890;ext=123>",
+			expectedURI: "tel:+1234567890;ext=123",
 		},
 		{
 			name: "tel URI with parameters",
@@ -530,7 +530,7 @@ func TestTransferSIPParticipantRequestValidate(t *testing.T) {
 				TransferTo:          "tel:+1234567890;phone-context=example.com",
 			},
 			expectError: false,
-			expectedURI: "<tel:+1234567890;phone-context=example.com>",
+			expectedURI: "tel:+1234567890;phone-context=example.com",
 		},
 		{
 			name: "sip URI with headers",