forked from fritob/Camper-Monitor
47 lines
1.9 KiB
Swift
47 lines
1.9 KiB
Swift
import CommonCrypto
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import Foundation
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/// AES-128 im Counter-Modus. CryptoKit bietet CTR nicht an, deshalb CommonCrypto.
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enum AESCounterMode {
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/// - Parameters:
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/// - data: Der verschlüsselte Nutzteil des Advertisements.
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/// - key: 16 Byte Geräteschlüssel aus VictronConnect.
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/// - nonce: Der 16-Byte-Zählerblock (Victron: Nonce little-endian in den
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/// ersten beiden Bytes, Rest 0).
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static func crypt(_ data: [UInt8], key: [UInt8], nonce: [UInt8]) -> [UInt8]? {
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guard key.count == kCCKeySizeAES128, nonce.count == kCCBlockSizeAES128 else { return nil }
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var cryptor: CCCryptorRef?
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let createStatus = key.withUnsafeBytes { keyBuffer in
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nonce.withUnsafeBytes { ivBuffer in
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CCCryptorCreateWithMode(
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CCOperation(kCCEncrypt), // CTR ist symmetrisch
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CCMode(kCCModeCTR),
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CCAlgorithm(kCCAlgorithmAES),
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CCPadding(ccNoPadding),
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ivBuffer.baseAddress,
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keyBuffer.baseAddress, key.count,
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nil, 0, 0,
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CCModeOptions(kCCModeOptionCTR_BE),
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&cryptor
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)
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}
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}
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guard createStatus == kCCSuccess, let cryptor else { return nil }
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defer { CCCryptorRelease(cryptor) }
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var output = [UInt8](repeating: 0, count: data.count)
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var moved = 0
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let updateStatus = data.withUnsafeBytes { input in
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output.withUnsafeMutableBytes { out in
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CCCryptorUpdate(cryptor,
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input.baseAddress, data.count,
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out.baseAddress, data.count,
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&moved)
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}
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}
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guard updateStatus == kCCSuccess else { return nil }
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return Array(output.prefix(moved))
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}
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}
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