func s2v(key []byte, strings [][]byte) []byte {
if len(key) == 0 {
panic("Key must be non-empty.")
}
// RFC 5297 defines S2V to handle an empty array, but never actually uses it
// that way for encryption or decryption. Additionally, the s2v_* reference
// functions don't handle that case. So don't handle it here.
if len(strings) == 0 {
panic("strings must be non-empty.")
}
// siv_init requires a full SIV key, i.e. twice the length of the key used by
// S2V. It uses the first half for the S2V key.
tmpKey := make([]byte, 2*len(key))
copy(tmpKey, key)
key = tmpKey
// Initialize the context struct.
var ctx C.siv_ctx
callResult := C.siv_init(&ctx, (*C.uchar)(&key[0]), C.int(8*len(key)))
if callResult < 0 {
panic("Error from siv_init.")
}
// Call s2v_update the requisite number of times.
for i := 0; i < len(strings)-1; i++ {
data := strings[i]
dataLen := len(data)
// Avoid indexing into an empty slice.
if dataLen == 0 {
data = make([]byte, 1)
}
C.s2v_update(&ctx, (*C.uchar)(&data[0]), C.int(dataLen))
}
// Now finalize with the last string. Avoid indexing into an empty slice.
lastString := strings[len(strings)-1]
lastStringLen := len(lastString)
if lastStringLen == 0 {
lastString = make([]byte, 1)
}
cDigest := (*C.uchar)(C.malloc(16))
defer C.free(unsafe.Pointer(cDigest))
callResult = C.s2v_final(
&ctx,
(*C.uchar)(&lastString[0]),
C.int(lastStringLen),
cDigest)
if callResult < 0 {
panic("Error from s2v_final.")
}
return C.GoBytes(unsafe.Pointer(cDigest), 16)
}
func encrypt(key, plaintext []byte, associated [][]byte) []byte {
if len(key) == 0 {
panic("Key must be non-empty.")
}
// Initialize the context struct.
var ctx C.siv_ctx
callResult := C.siv_init(&ctx, (*C.uchar)(&key[0]), C.int(8*len(key)))
if callResult < 0 {
panic("Error from siv_init.")
}
// Grab the right pointer for the plaintext, taking care not to index an
// empty slice.
var cPlaintext *C.uchar
cPlaintextLen := C.int(len(plaintext))
if cPlaintextLen > 0 {
cPlaintext = (*C.uchar)(&plaintext[0])
}
// Create a buffer to store the SIV.
cCounter := (*C.uchar)(C.malloc(16))
defer C.free(unsafe.Pointer(cCounter))
// Create associated data-related arguments. Take care not to index empty
// slices.
cNumAssociated := C.int(len(associated))
adLens := make([]C.int, cNumAssociated)
ads := make([]*C.uchar, cNumAssociated)
if cNumAssociated == 0 {
adLens = make([]C.int, 1)
ads = make([]*C.uchar, 1)
}
for i, _ := range associated {
aLen := len(associated[i])
adLens[i] = C.int(aLen)
if aLen > 0 {
ads[i] = (*C.uchar)(&associated[i][0])
}
}
cAdLens := (*C.int)(&adLens[0])
cAds := (**C.uchar)(&ads[0])
// Call siv_encrypt.
cCiphertext := (*C.uchar)(C.malloc(C.size_t(cPlaintextLen)))
defer C.free(unsafe.Pointer(cCiphertext))
callResult = C.siv_encrypt(
&ctx,
cPlaintext,
cCiphertext,
cPlaintextLen,
cCounter,
cNumAssociated,
cAdLens,
cAds)
if callResult < 0 {
panic("Error from siv_encrypt.")
}
iv := C.GoBytes(unsafe.Pointer(cCounter), 16)
ciphertext := C.GoBytes(unsafe.Pointer(cCiphertext), cPlaintextLen)
return append(iv, ciphertext...)
}
