feat(osiris): add TCP and TLS fingerprinting

Signed-off-by: Xe Iaso <me@xeiaso.net>
2026-04-28 02:52:42 +00:00 · 2025-07-18 20:38:19 +00:00
parent 1eafebedbc
commit d9c4e37978
10 changed files with 773 additions and 11 deletions
@@ -0,0 +1,106 @@
+//go:build freebsd
+
+package fingerprint
+
+import (
+	"fmt"
+	"net"
+	"syscall"
+	"unsafe"
+)
+
+type tcpInfo struct {
+	State          uint8
+	Options        uint8
+	SndScale       uint8
+	RcvScale       uint8
+	__pad          [4]byte
+	Rto            uint32
+	Ato            uint32
+	SndMss         uint32
+	RcvMss         uint32
+	Unacked        uint32
+	Sacked         uint32
+	Lost           uint32
+	Retrans        uint32
+	Fackets        uint32
+	Last_data_sent uint32
+	Last_ack_sent  uint32
+	Last_data_recv uint32
+	Last_ack_recv  uint32
+	Pmtu           uint32
+	Rcv_ssthresh   uint32
+	RTT            uint32
+	RTTvar         uint32
+	Snd_ssthresh   uint32
+	Snd_cwnd       uint32
+	Advmss         uint32
+	Reordering     uint32
+	Rcv_rtt        uint32
+	Rcv_space      uint32
+	Total_retrans  uint32
+	Snd_wnd        uint32
+	// Truncated for brevity — add more fields if needed
+}
+
+// AssignTCPFingerprint extracts TCP fingerprint information from a connection
+func AssignTCPFingerprint(conn net.Conn) (*JA4T, error) {
+	tcpConn, ok := conn.(*net.TCPConn)
+	if !ok {
+		return nil, fmt.Errorf("not a TCPConn")
+	}
+
+	rawConn, err := tcpConn.SyscallConn()
+	if err != nil {
+		return nil, fmt.Errorf("SyscallConn failed: %w", err)
+	}
+
+	var info tcpInfo
+	var sysErr error
+
+	err = rawConn.Control(func(fd uintptr) {
+		size := uint32(unsafe.Sizeof(info))
+		_, _, errno := syscall.Syscall6(
+			syscall.SYS_GETSOCKOPT,
+			fd,
+			uintptr(syscall.IPPROTO_TCP),
+			uintptr(syscall.TCP_INFO),
+			uintptr(unsafe.Pointer(&info)),
+			uintptr(unsafe.Pointer(&size)),
+			0,
+		)
+		if errno != 0 {
+			sysErr = errno
+		}
+	})
+	if err != nil {
+		return nil, fmt.Errorf("SyscallConn.Control: %w", err)
+	}
+	if sysErr != nil {
+		return nil, fmt.Errorf("getsockopt TCP_INFO: %w", sysErr)
+	}
+
+	fp := &JA4T{
+		Window:      info.Snd_wnd,
+		MSS:         uint16(info.SndMss),
+		WindowScale: info.SndScale,
+	}
+
+	const (
+		TCPI_OPT_TIMESTAMPS = 1 << 0
+		TCPI_OPT_SACK       = 1 << 1
+		TCPI_OPT_WSCALE     = 1 << 2
+	)
+
+	if info.Options&TCPI_OPT_SACK != 0 {
+		fp.Options = append(fp.Options, 4, 1)
+	}
+	if info.Options&TCPI_OPT_TIMESTAMPS != 0 {
+		fp.Options = append(fp.Options, 8, 1)
+	}
+	if info.Options&TCPI_OPT_WSCALE != 0 {
+		fp.Options = append(fp.Options, 3)
+	}
+
+	return fp, nil
+}