feat(osiris): add TCP and TLS fingerprinting

Signed-off-by: Xe Iaso <me@xeiaso.net>
2026-04-18 06:15:00 +00:00 · 2025-07-18 20:38:19 +00:00
parent 1eafebedbc
commit d9c4e37978
10 changed files with 773 additions and 11 deletions
--- a/internal/fingerprint/tcp_linux.go
+++ b/internal/fingerprint/tcp_linux.go
@@ -0,0 +1,132 @@
+//go:build linux
+
+package fingerprint
+
+import (
+	"fmt"
+	"net"
+	"syscall"
+	"unsafe"
+)
+
+type tcpInfo struct {
+	State                     uint8
+	Ca_state                  uint8
+	Retransmits               uint8
+	Probes                    uint8
+	Backoff                   uint8
+	Options                   uint8
+	Wnd_scale                 uint8
+	Delivery_rate_app_limited uint8
+
+	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
+	Pacing_rate     uint64
+	Max_pacing_rate uint64
+	Bytes_acked     uint64
+	Bytes_received  uint64
+	Segs_out        uint32
+	Segs_in         uint32
+	Notsent_bytes   uint32
+	Min_rtt         uint32
+	Data_segs_in    uint32
+	Data_segs_out   uint32
+	Delivery_rate   uint64
+	Busy_time       uint64
+	Rwnd_limited    uint64
+	Sndbuf_limited  uint64
+	Delivered       uint32
+	Delivered_ce    uint32
+	Bytes_sent      uint64
+	Bytes_retrans   uint64
+	DSACK_dups      uint32
+	Reord_seen      uint32
+	Rcv_ooopack     uint32
+	Snd_wnd         uint32
+}
+
+// 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),
+	}
+
+	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)
+		fp.WindowScale = info.Wnd_scale
+	}
+
+	return fp, nil
+}