diff --git a/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/keyDerivation.go b/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/keyDerivation.go
new file mode 100644
index 0000000..8c637a2
--- /dev/null
+++ b/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/keyDerivation.go
@@ -0,0 +1,178 @@
+package rfc3961
+
+import (
+	"bytes"
+
+	"gopkg.in/jcmturner/gokrb5.v7/crypto/etype"
+)
+
+const (
+	prfconstant = "prf"
+)
+
+// DeriveRandom implements the RFC 3961 defined function: DR(Key, Constant) = k-truncate(E(Key, Constant, initial-cipher-state)).
+//
+// key: base key or protocol key. Likely to be a key from a keytab file.
+//
+// usage: a constant.
+//
+// n: block size in bits (not bytes) - note if you use something like aes.BlockSize this is in bytes.
+//
+// k: key length / key seed length in bits. Eg. for AES256 this value is 256.
+//
+// e: the encryption etype function to use.
+func DeriveRandom(key, usage []byte, e etype.EType) ([]byte, error) {
+	n := e.GetCypherBlockBitLength()
+	k := e.GetKeySeedBitLength()
+	//Ensure the usage constant is at least the size of the cypher block size. Pass it through the nfold algorithm that will "stretch" it if needs be.
+	nFoldUsage := Nfold(usage, n)
+	//k-truncate implemented by creating a byte array the size of k (k is in bits hence /8)
+	out := make([]byte, k/8)
+
+	/*If the output	of E is shorter than k bits, it is fed back into the encryption as many times as necessary.
+	The construct is as follows (where | indicates concatenation):
+
+	K1 = E(Key, n-fold(Constant), initial-cipher-state)
+	K2 = E(Key, K1, initial-cipher-state)
+	K3 = E(Key, K2, initial-cipher-state)
+	K4 = ...
+
+	DR(Key, Constant) = k-truncate(K1 | K2 | K3 | K4 ...)*/
+	_, K, err := e.EncryptData(key, nFoldUsage)
+	if err != nil {
+		return out, err
+	}
+	for i := copy(out, K); i < len(out); {
+		_, K, _ = e.EncryptData(key, K)
+		i = i + copy(out[i:], K)
+	}
+	return out, nil
+}
+
+// DeriveKey derives a key from the protocol key based on the usage and the etype's specific methods.
+func DeriveKey(protocolKey, usage []byte, e etype.EType) ([]byte, error) {
+	r, err := e.DeriveRandom(protocolKey, usage)
+	if err != nil {
+		return nil, err
+	}
+	return e.RandomToKey(r), nil
+}
+
+// RandomToKey returns a key from the bytes provided according to the definition in RFC 3961.
+func RandomToKey(b []byte) []byte {
+	return b
+}
+
+// DES3RandomToKey returns a key from the bytes provided according to the definition in RFC 3961 for DES3 etypes.
+func DES3RandomToKey(b []byte) []byte {
+	r := fixWeakKey(stretch56Bits(b[:7]))
+	r2 := fixWeakKey(stretch56Bits(b[7:14]))
+	r = append(r, r2...)
+	r3 := fixWeakKey(stretch56Bits(b[14:21]))
+	r = append(r, r3...)
+	return r
+}
+
+// DES3StringToKey returns a key derived from the string provided according to the definition in RFC 3961 for DES3 etypes.
+func DES3StringToKey(secret, salt string, e etype.EType) ([]byte, error) {
+	s := secret + salt
+	tkey := e.RandomToKey(Nfold([]byte(s), e.GetKeySeedBitLength()))
+	return e.DeriveKey(tkey, []byte("kerberos"))
+}
+
+// PseudoRandom function as defined in RFC 3961
+func PseudoRandom(key, b []byte, e etype.EType) ([]byte, error) {
+	h := e.GetHashFunc()()
+	h.Write(b)
+	tmp := h.Sum(nil)[:e.GetMessageBlockByteSize()]
+	k, err := e.DeriveKey(key, []byte(prfconstant))
+	if err != nil {
+		return []byte{}, err
+	}
+	_, prf, err := e.EncryptData(k, tmp)
+	if err != nil {
+		return []byte{}, err
+	}
+	return prf, nil
+}
+
+func stretch56Bits(b []byte) []byte {
+	d := make([]byte, len(b), len(b))
+	copy(d, b)
+	var lb byte
+	for i, v := range d {
+		bv, nb := calcEvenParity(v)
+		d[i] = nb
+		if bv != 0 {
+			lb = lb | (1 << uint(i+1))
+		} else {
+			lb = lb &^ (1 << uint(i+1))
+		}
+	}
+	_, lb = calcEvenParity(lb)
+	d = append(d, lb)
+	return d
+}
+
+func calcEvenParity(b byte) (uint8, uint8) {
+	lowestbit := b & 0x01
+	// c counter of 1s in the first 7 bits of the byte
+	var c int
+	// Iterate over the highest 7 bits (hence p starts at 1 not zero) and count the 1s.
+	for p := 1; p < 8; p++ {
+		v := b & (1 << uint(p))
+		if v != 0 {
+			c++
+		}
+	}
+	if c%2 == 0 {
+		//Even number of 1s so set parity to 1
+		b = b | 1
+	} else {
+		//Odd number of 1s so set parity to 0
+		b = b &^ 1
+	}
+	return lowestbit, b
+}
+
+func fixWeakKey(b []byte) []byte {
+	if weak(b) {
+		b[7] ^= 0xF0
+	}
+	return b
+}
+
+func weak(b []byte) bool {
+	// weak keys from https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-67r1.pdf
+	weakKeys := [4][]byte{
+		{0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01},
+		{0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE, 0xFE},
+		{0xE0, 0xE0, 0xE0, 0xE0, 0xF1, 0xF1, 0xF1, 0xF1},
+		{0x1F, 0x1F, 0x1F, 0x1F, 0x0E, 0x0E, 0x0E, 0x0E},
+	}
+	semiWeakKeys := [12][]byte{
+		{0x01, 0x1F, 0x01, 0x1F, 0x01, 0x0E, 0x01, 0x0E},
+		{0x1F, 0x01, 0x1F, 0x01, 0x0E, 0x01, 0x0E, 0x01},
+		{0x01, 0xE0, 0x01, 0xE0, 0x01, 0xF1, 0x01, 0xF1},
+		{0xE0, 0x01, 0xE0, 0x01, 0xF1, 0x01, 0xF1, 0x01},
+		{0x01, 0xFE, 0x01, 0xFE, 0x01, 0xFE, 0x01, 0xFE},
+		{0xFE, 0x01, 0xFE, 0x01, 0xFE, 0x01, 0xFE, 0x01},
+		{0x1F, 0xE0, 0x1F, 0xE0, 0x0E, 0xF1, 0x0E, 0xF1},
+		{0xE0, 0x1F, 0xE0, 0x1F, 0xF1, 0x0E, 0xF1, 0x0E},
+		{0x1F, 0xFE, 0x1F, 0xFE, 0x0E, 0xFE, 0x0E, 0xFE},
+		{0xFE, 0x1F, 0xFE, 0x1F, 0xFE, 0x0E, 0xFE, 0x0E},
+		{0xE0, 0xFE, 0xE0, 0xFE, 0xF1, 0xFE, 0xF1, 0xFE},
+		{0xFE, 0xE0, 0xFE, 0xE0, 0xFE, 0xF1, 0xFE, 0xF1},
+	}
+	for _, k := range weakKeys {
+		if bytes.Equal(b, k) {
+			return true
+		}
+	}
+	for _, k := range semiWeakKeys {
+		if bytes.Equal(b, k) {
+			return true
+		}
+	}
+	return false
+}