feat(osiris): add TCP and TLS fingerprinting

Signed-off-by: Xe Iaso <me@xeiaso.net>

internal/fingerprint/ja3n.go

@@ -0,0 +1,97 @@
+package fingerprint
+
+import (
+	"crypto/md5"
+	"crypto/tls"
+	"encoding/hex"
+	"slices"
+	"strconv"
+)
+
+// TLSFingerprintJA3N represents a JA3N fingerprint
+type TLSFingerprintJA3N [md5.Size]byte
+
+func (f TLSFingerprintJA3N) String() string {
+	return hex.EncodeToString(f[:])
+}
+
+func buildJA3N(hello *tls.ClientHelloInfo, sortExtensions bool) TLSFingerprintJA3N {
+	buf := make([]byte, 0, 256)
+
+	{
+		var sslVersion uint16
+		var hasGrease bool
+		for _, v := range hello.SupportedVersions {
+			if v&greaseMask != greaseValue {
+				if v > sslVersion {
+					sslVersion = v
+				}
+			} else {
+				hasGrease = true
+			}
+		}
+
+		// maximum TLS 1.2 as specified on JA3, as TLS 1.3 is put in SupportedVersions
+		if slices.Contains(hello.Extensions, extensionSupportedVersions) && hasGrease && sslVersion > tls.VersionTLS12 {
+			sslVersion = tls.VersionTLS12
+		}
+
+		buf = strconv.AppendUint(buf, uint64(sslVersion), 10)
+		buf = append(buf, ',')
+	}
+
+	n := 0
+	for _, cipher := range hello.CipherSuites {
+		//if !slices.Contains(greaseValues[:], cipher) {
+		if cipher&greaseMask != greaseValue {
+			buf = strconv.AppendUint(buf, uint64(cipher), 10)
+			buf = append(buf, '-')
+			n = 1
+		}
+	}
+
+	buf = buf[:len(buf)-n]
+	buf = append(buf, ',')
+	n = 0
+
+	extensions := hello.Extensions
+	if sortExtensions {
+		extensions = slices.Clone(extensions)
+		slices.Sort(extensions)
+	}
+
+	for _, extension := range extensions {
+		if extension&greaseMask != greaseValue {
+			buf = strconv.AppendUint(buf, uint64(extension), 10)
+			buf = append(buf, '-')
+			n = 1
+		}
+	}
+
+	buf = buf[:len(buf)-n]
+	buf = append(buf, ',')
+	n = 0
+
+	for _, curve := range hello.SupportedCurves {
+		if curve&greaseMask != greaseValue {
+			buf = strconv.AppendUint(buf, uint64(curve), 10)
+			buf = append(buf, '-')
+			n = 1
+		}
+	}
+
+	buf = buf[:len(buf)-n]
+	buf = append(buf, ',')
+	n = 0
+
+	for _, point := range hello.SupportedPoints {
+		buf = strconv.AppendUint(buf, uint64(point), 10)
+		buf = append(buf, '-')
+		n = 1
+	}
+
+	buf = buf[:len(buf)-n]
+
+	sum := md5.Sum(buf)
+	return TLSFingerprintJA3N(sum[:])
+}