add AES-128-CFB mode and it's test code.

[jifanchn]

Hi kokke:

I write a small piece of code to support CFB mode.

I think the code style is quite like the CFB part.

And I generated the test sample by a small golang program and paste the results into test code.

May this is helpful to others.

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"encoding/hex"
	"fmt"
)

func main() {
	in := []byte{ 0x76, 0x49, 0xab, 0xac, 0x81, 0x19, 0xb2, 0x46, 0xce, 0xe9, 0x8e, 0x9b, 0x12, 0xe9, 0x19, 0x7d,
		0x50, 0x86, 0xcb, 0x9b, 0x50, 0x72, 0x19, 0xee, 0x95, 0xdb, 0x11, 0x3a, 0x91, 0x76, 0x78, 0xb2,
		0x73, 0xbe, 0xd6, 0xb8, 0xe3, 0xc1, 0x74, 0x3b, 0x71, 0x16, 0xe6, 0x9e, 0x22, 0x22, 0x95, 0x16,
		0x3f, 0xf1, 0xca, 0xa1, 0x68, 0x1f, 0xac, 0x09, 0x12, 0x0e, 0xca, 0x30, 0x75, 0x86, 0xe1, 0xa7 }
	key := []byte{0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c}
	iv := []byte{ 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f }
	encrypted := AesEncryptCFB(in, key, iv)
	print(fmt.Printf("%v\n", encrypted))
	line := 0
	for i:=0; i<len(encrypted); i++ {
		print("0x" + hex.EncodeToString(encrypted[i:i+1]) + ", ")
		line += 1
		if line == 16 {
			line = 0
			print("\n")
		}
	}

}

func AesEncryptCFB(origData []byte, key []byte, iv []byte) (encrypted []byte) {
	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}
	encrypted = make([]byte, len(origData))

	stream := cipher.NewCFBEncrypter(block, iv)
	stream.XORKeyStream(encrypted, origData)
	return encrypted
}

[wmjdgla]

Should revert to the original line since the #if is for CTR

[wmjdgla]

In aes.h/c, the code guarded by #if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1)) should also apply to CFB mode, so I think the guard should be updated to include CFB?

[jifanchn]

Already fixed

[lil-skelly]

I was looking for a CFB mode implementation, and thankfully, I found this.
The code looks well structured and seems functional, I don't see why this hasn't been merged yet. @kokke , perhaps you want to take a look at this.