install go2rtc on bob

installs_on_host/go2rtc/pkg/tutk/dtls/auth.go

@@ -0,0 +1,35 @@
+package dtls
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"strings"
+)
+
+func CalculateAuthKey(enr, mac string) []byte {
+	data := enr + strings.ToUpper(mac)
+	hash := sha256.Sum256([]byte(data))
+	b64 := base64.StdEncoding.EncodeToString(hash[:6])
+	b64 = strings.ReplaceAll(b64, "+", "Z")
+	b64 = strings.ReplaceAll(b64, "/", "9")
+	b64 = strings.ReplaceAll(b64, "=", "A")
+	return []byte(b64)
+}
+
+func DerivePSK(enr string) []byte {
+	// DerivePSK derives the DTLS PSK from ENR
+	// TUTK SDK treats the PSK as a NULL-terminated C string, so if SHA256(ENR)
+	// contains a 0x00 byte, the PSK is truncated at that position.
+	hash := sha256.Sum256([]byte(enr))
+	pskLen := 32
+	for i := range 32 {
+		if hash[i] == 0x00 {
+			pskLen = i
+			break
+		}
+	}
+
+	psk := make([]byte, 32)
+	copy(psk[:pskLen], hash[:pskLen])
+	return psk
+}