46 lines
903 B
Go
46 lines
903 B
Go
|
// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
|
||
|
|
// SPDX-License-Identifier: MIT
|
||
|
|
|
||
|
|
package srtp
|
||
|
|
|
||
|
|
import (
|
||
|
|
"crypto/cipher"
|
||
|
|
|
||
|
|
"github.com/pion/transport/v2/utils/xor"
|
||
|
|
)
|
||
|
|
|
||
|
|
// incrementCTR increments a big-endian integer of arbitrary size.
|
||
|
|
func incrementCTR(ctr []byte) {
|
||
|
|
for i := len(ctr) - 1; i >= 0; i-- {
|
||
|
|
ctr[i]++
|
||
|
|
if ctr[i] != 0 {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// xorBytesCTR performs CTR encryption and decryption.
|
||
|
|
// It is equivalent to cipher.NewCTR followed by XORKeyStream.
|
||
|
|
func xorBytesCTR(block cipher.Block, iv []byte, dst, src []byte) error {
|
||
|
|
if len(iv) != block.BlockSize() {
|
||
|
|
return errBadIVLength
|
||
|
|
}
|
||
|
|
|
||
|
|
ctr := make([]byte, len(iv))
|
||
|
|
copy(ctr, iv)
|
||
|
|
bs := block.BlockSize()
|
||
|
|
stream := make([]byte, bs)
|
||
|
|
|
||
|
|
i := 0
|
||
|
|
for i < len(src) {
|
||
|
|
block.Encrypt(stream, ctr)
|
||
|
|
incrementCTR(ctr)
|
||
|
|
n := xor.XorBytes(dst[i:], src[i:], stream)
|
||
|
|
if n == 0 {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
i += n
|
||
|
|
}
|
||
|
|
return nil
|
||
|
|
}
|