Created
May 17, 2020 19:08
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TCP-MD5 client and server in Golang (RFC 2385). Written and tested using Go 1.14.3 on Ubuntu 18.04 x64 running kernel 4.15. See accompanying blog post: https://covert.sh/2020/05/17/golang-tcp-md5/
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package main | |
import ( | |
"context" | |
"golang.org/x/sys/unix" | |
"io" | |
"log" | |
"net" | |
"os" | |
"syscall" | |
"time" | |
"unsafe" | |
) | |
func main() { | |
key := []byte("sup3rsecretkey") | |
var keyArray [80]byte | |
copy(keyArray[0:], key) | |
saStorage := unix.SockaddrStorage{ | |
Family: unix.AF_INET, | |
} | |
tcpMD5Sig := unix.TCPMD5Sig{ | |
Addr: saStorage, | |
Flags: unix.TCP_MD5SIG_FLAG_PREFIX, | |
Prefixlen: 0, | |
Keylen: uint16(len(key)), | |
Key: keyArray, | |
} | |
var d net.Dialer | |
ctx, cancel := context.WithTimeout(context.Background(), time.Minute) | |
defer cancel() | |
d.Control = func(network, address string, c syscall.RawConn) error { | |
var err error | |
c.Control(func(fdPtr uintptr) { | |
fd := int(fdPtr) | |
b := *(*[unsafe.Sizeof(tcpMD5Sig)]byte)(unsafe.Pointer(&tcpMD5Sig)) | |
err = unix.SetsockoptString(fd, unix.IPPROTO_TCP, unix.TCP_MD5SIG_EXT, string(b[:])) | |
}) | |
return err | |
} | |
conn, err := d.DialContext(ctx, "tcp", "127.0.0.1:8081") | |
if err != nil { | |
log.Fatal(err) | |
} | |
go func() { | |
io.Copy(os.Stdout, conn) | |
}() | |
io.Copy(conn, os.Stdin) | |
conn.Close() | |
} |
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package main | |
import ( | |
"context" | |
"golang.org/x/sys/unix" | |
"io" | |
"log" | |
"net" | |
"syscall" | |
"time" | |
"unsafe" | |
) | |
func main() { | |
key := []byte("sup3rsecretkey") | |
var keyArray [80]byte | |
copy(keyArray[0:], key) | |
saStorage := unix.SockaddrStorage{ | |
Family: unix.AF_INET, | |
} | |
tcpMD5Sig := unix.TCPMD5Sig{ | |
Addr: saStorage, | |
Flags: unix.TCP_MD5SIG_FLAG_PREFIX, | |
Prefixlen: 0, | |
Keylen: uint16(len(key)), | |
Key: keyArray, | |
} | |
var lc net.ListenConfig | |
ctx, cancel := context.WithTimeout(context.Background(), time.Minute) | |
defer cancel() | |
lc.Control = func(network, address string, c syscall.RawConn) error { | |
var err error | |
c.Control(func(fdPtr uintptr) { | |
fd := int(fdPtr) | |
b := *(*[unsafe.Sizeof(tcpMD5Sig)]byte)(unsafe.Pointer(&tcpMD5Sig)) | |
err = unix.SetsockoptString(fd, unix.IPPROTO_TCP, unix.TCP_MD5SIG_EXT, string(b[:])) | |
}) | |
return err | |
} | |
l, err := lc.Listen(ctx, "tcp", "127.0.0.1:8081") | |
if err != nil { | |
log.Fatal(err) | |
} | |
for { | |
conn, err := l.Accept() | |
if err != nil { | |
log.Fatal(err) | |
} | |
go func(c net.Conn) { | |
io.Copy(c, c) | |
c.Close() | |
}(conn) | |
} | |
} |
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