//Oracle for set 2 challenge 12
func ECBChosenPrefix(input []byte, key []byte) []byte {
secret := encoding.Base64ToBytes(`Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkgaGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBqdXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUgYnkK`)
data := append(input, secret...)
data = aes.Pad(data, 16)
return aes.ECBEncrypt(key, data)
}
//Test case for Set 2 Challenge 11
func TestDetectionOracle(t *testing.T) {
//Simulating data i would send myself
testcase := []byte("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA")
//Big ugly oracle function.
oracle := func(plaintext []byte) (result []byte, mode string) {
key := make([]byte, 16)
_, err := rand.Read(key)
if err != nil {
t.Errorf("DetectionOracle: Reading random bytes failed.")
}
//"Coin flip"
var number byte
binary.Read(rand.Reader, binary.LittleEndian, &number)
cbc := false
if number%2 == 0 {
cbc = true
}
//Random prefix and postfix
var pre uint32
var post uint32
binary.Read(rand.Reader, binary.LittleEndian, &pre)
binary.Read(rand.Reader, binary.LittleEndian, &post)
predata := make([]byte, pre%10)
postdata := make([]byte, post%10)
rand.Read(predata)
rand.Read(postdata)
data := append(predata, plaintext...)
data = append(data, postdata...)
data = aes.Pad(data, 16)
if cbc {
iv := make([]byte, 16)
_, err := rand.Read(iv)
if err != nil {
t.Errorf("DetectionOracle: Reading random bytes failed.")
}
result = aes.CBCEncrypt(key, iv, data)
mode = "CBC"
return
} else {
result = aes.ECBEncrypt(key, data)
mode = "ECB"
return
}
}
//Iterate oracle
for i := 0; i < 40; i++ {
data, mode := oracle(testcase)
if output := AESModeDetectionOracle(data); output != mode {
t.Errorf("DetectionOracle: Detection oracle failed to guess correctly.")
t.Errorf("\tExpected: %v", mode)
t.Errorf("\tGuessed: %v", output)
}
}
}
//For simplicity sake, return key and iv too.
func EncryptComment(comment string) (key, iv, ciphertext []byte) {
pre := []byte("comment1=cooking%20MCs;userdata=")
//Eat illegal characters
comment = strings.Split(comment, ";")[0]
comment = strings.Split(comment, "=")[0]
combytes := []byte(comment)
post := []byte(";comment2=%20like%20a%20pound%20of%20bacon")
plaintext := append(pre, combytes...)
plaintext = append(plaintext, post...)
plaintext = aes.Pad(plaintext, 16)
key = aes.RandBytes(16)
iv = aes.RandBytes(16)
ciphertext = aes.CBCEncrypt(key, iv, plaintext)
return
}
func ProfileFor(key []byte, profile string) []byte {
u := User{role: "user", uid: "17", email: profile}
ue := []byte(u.Encode())
return aes.ECBEncrypt(key, aes.Pad(ue, 16))
}