libsignal/swift/Sources/LibSignalClient/Kdf.swift

//
// Copyright 2020-2022 Signal Messenger, LLC.
// SPDX-License-Identifier: AGPL-3.0-only
//

import SignalFfi
import Foundation

public func hkdf<InputBytes, SaltBytes, InfoBytes>(outputLength: Int,
                                                   inputKeyMaterial: InputBytes,
                                                   salt: SaltBytes,
                                                   info: InfoBytes) throws -> [UInt8]
where InputBytes: ContiguousBytes, SaltBytes: ContiguousBytes, InfoBytes: ContiguousBytes {
    var output = Array(repeating: UInt8(0x00), count: outputLength)

    try output.withUnsafeMutableBytes { outputBuffer in
        try inputKeyMaterial.withUnsafeBorrowedBuffer { inputBuffer in
            try salt.withUnsafeBorrowedBuffer { saltBuffer in
                try info.withUnsafeBorrowedBuffer { infoBuffer in
                    try checkError(signal_hkdf_derive(.init(outputBuffer),
                                                      inputBuffer,
                                                      infoBuffer,
                                                      saltBuffer))
                }
            }
        }
    }

    return output
}

@available(*, deprecated, message: "Remove the 'version' parameter for standard HKDF behavior")
public func hkdf<InputBytes, SaltBytes, InfoBytes>(outputLength: Int,
                                                   version: UInt32,
                                                   inputKeyMaterial: InputBytes,
                                                   salt: SaltBytes,
                                                   info: InfoBytes) throws -> [UInt8]
where InputBytes: ContiguousBytes, SaltBytes: ContiguousBytes, InfoBytes: ContiguousBytes {
    precondition(version == 3, "HKDF versions other than 3 are no longer supported")
    return try hkdf(outputLength: outputLength,
                    inputKeyMaterial: inputKeyMaterial,
                    salt: salt,
                    info: info)
}