add functions for MPPE handshakes (RFC 3079)

This patch adds support for adding MPPE send/recv keys that are attached to MSCHAPv2 response packets, as described by RFC 3079. The results from MakeKey() can be used as input for NewTunnelPassword(). Code is tested with examples from section 3.5 of the RFC.
jarek-dz · Jul 20, 2020 · 39bb143 · 39bb143
1 parent b96a9ba
commit 39bb143
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diff --git a/rfc3079/mppe.go b/rfc3079/mppe.go
@@ -0,0 +1,117 @@
+package rfc3079
+
+import (
+	"crypto/sha1"
+	"errors"
+
+	"layeh.com/radius/rfc2759"
+)
+
+// KeyLength is the length of keys involved with the functions below
+type KeyLength uint
+
+const (
+	// KeyLength40Bit - 40-bit
+	KeyLength40Bit = KeyLength(8)
+	// KeyLength128Bit - 128-bit
+	KeyLength128Bit = KeyLength(16)
+)
+
+var (
+	shaPad1 = []byte{
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	}
+
+	shaPad2 = []byte{
+		0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+		0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+		0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+		0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+	}
+
+	magic1 = []byte{
+		0x54, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x74,
+		0x68, 0x65, 0x20, 0x4d, 0x50, 0x50, 0x45, 0x20, 0x4d,
+		0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x4b, 0x65, 0x79,
+	}
+
+	magic2 = []byte{
+		0x4f, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x69,
+		0x65, 0x6e, 0x74, 0x20, 0x73, 0x69, 0x64, 0x65, 0x2c, 0x20,
+		0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x74, 0x68,
+		0x65, 0x20, 0x73, 0x65, 0x6e, 0x64, 0x20, 0x6b, 0x65, 0x79,
+		0x3b, 0x20, 0x6f, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x73,
+		0x65, 0x72, 0x76, 0x65, 0x72, 0x20, 0x73, 0x69, 0x64, 0x65,
+		0x2c, 0x20, 0x69, 0x74, 0x20, 0x69, 0x73, 0x20, 0x74, 0x68,
+		0x65, 0x20, 0x72, 0x65, 0x63, 0x65, 0x69, 0x76, 0x65, 0x20,
+		0x6b, 0x65, 0x79, 0x2e,
+	}
+
+	magic3 = []byte{
+		0x4f, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x69,
+		0x65, 0x6e, 0x74, 0x20, 0x73, 0x69, 0x64, 0x65, 0x2c, 0x20,
+		0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x74, 0x68,
+		0x65, 0x20, 0x72, 0x65, 0x63, 0x65, 0x69, 0x76, 0x65, 0x20,
+		0x6b, 0x65, 0x79, 0x3b, 0x20, 0x6f, 0x6e, 0x20, 0x74, 0x68,
+		0x65, 0x20, 0x73, 0x65, 0x72, 0x76, 0x65, 0x72, 0x20, 0x73,
+		0x69, 0x64, 0x65, 0x2c, 0x20, 0x69, 0x74, 0x20, 0x69, 0x73,
+		0x20, 0x74, 0x68, 0x65, 0x20, 0x73, 0x65, 0x6e, 0x64, 0x20,
+		0x6b, 0x65, 0x79, 0x2e,
+	}
+)
+
+// GetMasterKey - rfc3079, 3.4
+func GetMasterKey(passwordHashHash, ntResponse []byte) []byte {
+	sha := sha1.New()
+	sha.Write(passwordHashHash)
+	sha.Write(ntResponse)
+	sha.Write(magic1)
+	digest := sha.Sum(nil)
+
+	return digest[:16]
+}
+
+// GetAsymmetricStartKey - rfc3079, 3.4
+func GetAsymmetricStartKey(masterKey []byte, sessionKeyLength KeyLength, isSend bool) ([]byte, error) {
+	if len(masterKey) != 16 {
+		return []byte{}, errors.New("masterKey must be 16 bytes long")
+	}
+
+	s := []byte{}
+
+	if isSend {
+		s = magic3
+	} else {
+		s = magic2
+	}
+
+	sha := sha1.New()
+	sha.Write(masterKey)
+	sha.Write(shaPad1)
+	sha.Write(s)
+	sha.Write(shaPad2)
+	digest := sha.Sum(nil)
+
+	return digest[:sessionKeyLength], nil
+}
+
+// MakeKey - rfc2548, 2.4.2
+func MakeKey(ntResponse []byte, password string, isSend bool) ([]byte, error) {
+	if len(ntResponse) != 24 {
+		return []byte{}, errors.New("ntresponse must be 24 bytes in size")
+	}
+
+	ucs2Password, err := rfc2759.ToUTF16(password)
+	if err != nil {
+		return []byte{}, err
+	}
+
+	passwordHash := rfc2759.HashPassword(ucs2Password)
+	passwordHashHash := rfc2759.HashPassword(passwordHash)
+	masterKey := GetMasterKey(passwordHashHash, ntResponse)
+
+	return GetAsymmetricStartKey(masterKey, KeyLength128Bit, isSend)
+}
diff --git a/rfc3079/mppe_test.go b/rfc3079/mppe_test.go
@@ -0,0 +1,92 @@
+package rfc3079
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestGetMasterKey(t *testing.T) {
+	type args struct {
+		passwordHashHash []byte
+		ntResponse       []byte
+	}
+	tests := []struct {
+		name string
+		args args
+		want []byte
+	}{
+		{
+			name: "rfc3079, 3.5.1",
+			args: args{
+				passwordHashHash: []byte{
+					0x41, 0xC0, 0x0C, 0x58, 0x4B, 0xD2, 0xD9, 0x1C, 0x40, 0x17, 0xA2, 0xA1, 0x2F, 0xA5, 0x9F, 0x3F,
+				},
+				ntResponse: []byte{
+					0x82, 0x30, 0x9E, 0xCD, 0x8D, 0x70, 0x8B, 0x5E, 0xA0, 0x8F, 0xAA, 0x39, 0x81, 0xCD, 0x83, 0x54, 0x42, 0x33,
+					0x11, 0x4A, 0x3D, 0x85, 0xD6, 0xDF,
+				},
+			},
+			want: []byte{
+				0xFD, 0xEC, 0xE3, 0x71, 0x7A, 0x8C, 0x83, 0x8C, 0xB3, 0x88, 0xE5, 0x27, 0xAE, 0x3C, 0xDD, 0x31,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := GetMasterKey(tt.args.passwordHashHash, tt.args.ntResponse); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("GetMasterKey() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestGetAsymmetricStartKey(t *testing.T) {
+	type args struct {
+		masterKey        []byte
+		sessionKeyLength KeyLength
+		isSend           bool
+	}
+	tests := []struct {
+		name string
+		args args
+		want []byte
+	}{
+		{
+			name: "40-bit, rfc3079, 3.5.1",
+			args: args{
+				masterKey: []byte{
+					0xFD, 0xEC, 0xE3, 0x71, 0x7A, 0x8C, 0x83, 0x8C, 0xB3, 0x88, 0xE5, 0x27, 0xAE, 0x3C, 0xDD, 0x31,
+				},
+				sessionKeyLength: KeyLength40Bit,
+				isSend:           true,
+			},
+			want: []byte{
+				0x8B, 0x7C, 0xDC, 0x14, 0x9B, 0x99, 0x3A, 0x1B,
+			},
+		},
+		{
+			name: "128-bit, rfc3079, 3.5.3",
+			args: args{
+				masterKey: []byte{
+					0xFD, 0xEC, 0xE3, 0x71, 0x7A, 0x8C, 0x83, 0x8C, 0xB3, 0x88, 0xE5, 0x27, 0xAE, 0x3C, 0xDD, 0x31,
+				},
+				sessionKeyLength: 16,
+				isSend:           true,
+			},
+			want: []byte{
+				0x8B, 0x7C, 0xDC, 0x14, 0x9B, 0x99, 0x3A, 0x1B, 0xA1, 0x18, 0xCB, 0x15, 0x3F, 0x56, 0xDC, 0xCB,
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := GetAsymmetricStartKey(tt.args.masterKey, tt.args.sessionKeyLength, tt.args.isSend)
+			if err != nil {
+				t.Errorf("err = %v", err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("GetAsymmetricStartKey() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}