1 files changed, 92 insertions, 0 deletions
diff --git a/client/network.go b/client/network.go
new file mode 100644
index 0000000..b29928f
--- /dev/null
+++ b/client/network.go
@@ -0,0 +1,92 @@
+package client
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+	"time"
+
+	krbClient "github.com/jcmturner/gokrb5/v8/client"
+	"github.com/jcmturner/gokrb5/v8/kadmin"
+)
+
+// From here: https://github.com/jcmturner/gokrb5/blob/v8.4.4/v8/client/passwd.go#L51C1-L75C2
+// It would be really nice if this was public, but it isn't :(
+func sendToKAdmin(cl *krbClient.Client, msg kadmin.Request) (r kadmin.Reply, err error) {
+	_, kps, err := cl.Config.GetKpasswdServers(cl.Credentials.Domain(), true)
+	if err != nil {
+		return
+	}
+	b, err := msg.Marshal()
+	if err != nil {
+		return
+	}
+	var rb []byte
+	rb, err = dialSendTCP(kps, b)
+	if err != nil {
+		return
+	}
+	err = r.Unmarshal(rb)
+
+	return
+}
+
+// Below are from here: https://github.com/jcmturner/gokrb5/blob/master/v8/client/network.go
+// Likewise, it sucks that the change password API is so limited, and there is zero low-level exposure without copy-pasting code.
+// dialSendTCP establishes a TCP connection to a KDC.
+func dialSendTCP(kdcs map[int]string, b []byte) ([]byte, error) {
+	var errs []string
+	for i := 1; i <= len(kdcs); i++ {
+		conn, err := net.DialTimeout("tcp", kdcs[i], 5*time.Second)
+		if err != nil {
+			errs = append(errs, fmt.Sprintf("error establishing connection to %s: %v", kdcs[i], err))
+			continue
+		}
+		if err := conn.SetDeadline(time.Now().Add(5 * time.Second)); err != nil {
+			errs = append(errs, fmt.Sprintf("error setting deadline on connection to %s: %v", kdcs[i], err))
+			continue
+		}
+		// conn is guaranteed to be a TCPConn
+		rb, err := sendTCP(conn.(*net.TCPConn), b)
+		if err != nil {
+			errs = append(errs, fmt.Sprintf("error sending to %s: %v", kdcs[i], err))
+			continue
+		}
+		return rb, nil
+	}
+	return nil, fmt.Errorf("error sending: %s", strings.Join(errs, "; "))
+}
+
+// sendTCP sends bytes to connection over TCP.
+func sendTCP(conn *net.TCPConn, b []byte) ([]byte, error) {
+	defer conn.Close()
+	var r []byte
+	// RFC 4120 7.2.2 specifies the first 4 bytes indicate the length of the message in big endian order.
+	hb := make([]byte, 4, 4)
+	binary.BigEndian.PutUint32(hb, uint32(len(b)))
+	b = append(hb, b...)
+
+	_, err := conn.Write(b)
+	if err != nil {
+		return r, fmt.Errorf("error sending to %s: %v", conn.RemoteAddr().String(), err)
+	}
+
+	sh := make([]byte, 4, 4)
+	_, err = conn.Read(sh)
+	if err != nil {
+		return r, fmt.Errorf("error reading response size header: %v", err)
+	}
+	s := binary.BigEndian.Uint32(sh)
+
+	rb := make([]byte, s, s)
+	_, err = io.ReadFull(conn, rb)
+	if err != nil {
+		return r, fmt.Errorf("error reading response: %v", err)
+	}
+	if len(rb) < 1 {
+		return r, fmt.Errorf("no response data from %s", conn.RemoteAddr().String())
+	}
+	return rb, nil
+}