TEL-1118 Allowing longer values for encrypted headers

.changeset/sip-encrypted-header-values.md

@@ -0,0 +1,5 @@
+---
+"github.com/livekit/protocol": patch
+---
+
+Allow SIP header values with the `lkenc:` prefix up to 8192 characters, so that encrypted header values pass validation

livekit/sip_validation.go

@@ -246,6 +246,14 @@ func ValidateHeaderName(name string, restrictNames bool) error {
 	return nil
 }
 
+// EncryptedHeaderValuePrefix marks a header value that was encrypted.
+const EncryptedHeaderValuePrefix = "lkenc:"
+
+const (
+	maxHeaderValueLen          = 1024
+	maxEncryptedHeaderValueLen = 8192
+)
+
 // ValidateHeaderValue validates a SIP header value per RFC 3261 Section 25.1
 func ValidateHeaderValue(name, value string) error {
 	return ValidateHeaderValueResult(name, value).Error()
@@ -257,8 +265,12 @@ func ValidateHeaderValueResult(name, value string) ValidationResult {
 		return ValidationResult{}
 	}
 
-	if len(value) > 1024 {
-		return ValidationFailure(fmt.Errorf("header %s: value too long (max 1024 characters)", name))
+	maxLen := maxHeaderValueLen
+	if strings.HasPrefix(value, EncryptedHeaderValuePrefix) {
+		maxLen = maxEncryptedHeaderValueLen
+	}
+	if len(value) > maxLen {
+		return ValidationFailure(fmt.Errorf("header %s: value too long (max %d characters)", name, maxLen))
 	}
 
 	// Basic character validation - printable ASCII. We're stricter than the spec here - no UTF-8 for now

livekit/sip_validation_test.go

@@ -100,6 +100,7 @@ var ValidHeaderValues = []string{
 	"Header with unicode 世界",               // Unicode
 	"Header with unicode émojis 🎉",         // Unicode with emojis
 	strings.Repeat("a", 1024),              // max length
+	EncryptedHeaderValuePrefix + strings.Repeat("a", 8192-len(EncryptedHeaderValuePrefix)), // encrypted max length
 }
 
 // Note: These restrictions are NOT in RFC 3261 but are applied for security/performance
@@ -111,6 +112,7 @@ var InvalidHeaderValues = []string{
 	"Header with\x1Funit separator", // control character
 	"Header with\x7Fdelete",         // delete character
 	strings.Repeat("a", 1025),       // too long
+	EncryptedHeaderValuePrefix + strings.Repeat("a", 8193-len(EncryptedHeaderValuePrefix)), // encrypted too long
 }
 
 // testCaseName truncates a test case name to maxLen and adds dots with total size