RFC Tests failing

[aarondl]

Hello there.

I added the RFC tests cited here: https://tools.ietf.org/html/rfc4269.html

It appears that this library fails all of them. I didn't want to fork & PR so here's the tests I wrote:

func TestRFCVectors(t *testing.T) {
	t.Parallel()

	tests := []struct {
		Key []byte
		PT  []byte
		CT  []byte
	}{
		{
			Key: []byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
			PT:  []byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F},
			CT:  []byte{0x5E, 0xBA, 0xC6, 0xE0, 0x05, 0x4E, 0x16, 0x68, 0x19, 0xAF, 0xF1, 0xCC, 0x6D, 0x34, 0x6C, 0xDB},
		},
		{
			Key: []byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F},
			PT:  []byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
			CT:  []byte{0xC1, 0x1F, 0x22, 0xF2, 0x01, 0x40, 0x50, 0x50, 0x84, 0x48, 0x35, 0x97, 0xE4, 0x37, 0x0F, 0x43},
		},
		{
			Key: []byte{0x47, 0x06, 0x48, 0x08, 0x51, 0xE6, 0x1B, 0xE8, 0x5D, 0x74, 0xBF, 0xB3, 0xFD, 0x95, 0x61, 0x85},
			PT:  []byte{0x83, 0xA2, 0xF8, 0xA2, 0x88, 0x64, 0x1F, 0xB9, 0xA4, 0xE9, 0xA5, 0xCC, 0x2F, 0x13, 0x1C, 0x7D},
			CT:  []byte{0xEE, 0x54, 0xD1, 0x3E, 0xBC, 0xAE, 0x70, 0x6D, 0x22, 0x6B, 0xC3, 0x14, 0x2C, 0xD4, 0x0D, 0x4A},
		},
		{
			Key: []byte{0x28, 0xDB, 0xC3, 0xBC, 0x49, 0xFF, 0xD8, 0x7D, 0xCF, 0xA5, 0x09, 0xB1, 0x1D, 0x42, 0x2B, 0xE7},
			PT:  []byte{0xB4, 0x1E, 0x6B, 0xE2, 0xEB, 0xA8, 0x4A, 0x14, 0x8E, 0x2E, 0xED, 0x84, 0x59, 0x3C, 0x5E, 0xC7},
			CT:  []byte{0x9B, 0x9B, 0x7B, 0xFC, 0xD1, 0x81, 0x3C, 0xB9, 0x5D, 0x0B, 0x36, 0x18, 0xF4, 0x0F, 0x51, 0x22},
		},
	}

	for i, test := range tests {
		c, err := NewCipher(test.Key)
		if err != nil {
			panic(err)
		}

		gotEncrypt := make([]byte, c.BlockSize())
		c.Encrypt(gotEncrypt, test.PT)

		if !bytes.Equal(gotEncrypt, test.CT) {
			t.Errorf("%d) failed encryption\nwant: %X\n got: %X\n", i, test.CT, gotEncrypt)
		}

		gotDecrypt := make([]byte, c.BlockSize())
		c.Decrypt(gotDecrypt, test.CT)

		if !bytes.Equal(gotDecrypt, test.PT) {
			t.Errorf("%d) failed decryption\nwant: %X\n got: %X\n", i, test.PT, gotDecrypt)
		}
	}
}