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/*
* Copyright (C) 2020 Square, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package okio.internal
import okio.ByteString
import okio.xor
internal class Hmac private constructor(
private val hashFunction: HashFunction,
private val outerKey: ByteArray
) : HashFunction {
override fun update(input: ByteArray, offset: Int, byteCount: Int) {
hashFunction.update(input, offset, byteCount)
}
override fun digest(): ByteArray {
val digest = hashFunction.digest()
hashFunction.update(outerKey)
hashFunction.update(digest)
return hashFunction.digest()
}
companion object {
private const val IPAD: Byte = 54
private const val OPAD: Byte = 92
fun sha1(key: ByteString) =
create(key, hashFunction = Sha1(), blockLength = 64)
fun sha256(key: ByteString) =
create(key, hashFunction = Sha256(), blockLength = 64)
fun sha512(key: ByteString) =
create(key, hashFunction = Sha512(), blockLength = 128)
private fun create(
key: ByteString,
hashFunction: HashFunction,
blockLength: Int
): Hmac {
val keySize = key.size
val paddedKey = when {
keySize == 0 -> throw IllegalArgumentException("Empty key")
keySize == blockLength -> key.data
keySize < blockLength -> key.data.copyOf(blockLength)
else -> hashFunction.apply { update(key.data) }.digest().copyOf(blockLength)
}
val innerKey = ByteArray(blockLength) { paddedKey[it] xor IPAD }
val outerKey = ByteArray(blockLength) { paddedKey[it] xor OPAD }
hashFunction.update(innerKey)
return Hmac(
hashFunction,
outerKey
)
}
}
}
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