83 lines
3.3 KiB
Swift
83 lines
3.3 KiB
Swift
import Foundation
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import CryptoKit
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/// Generates OpenSSH representations of Secrets.
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public struct OpenSSHKeyWriter {
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/// Initializes the writer.
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public init() {
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}
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/// Generates an OpenSSH data payload identifying the secret.
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/// - Returns: OpenSSH data payload identifying the secret.
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public func data<SecretType: Secret>(secret: SecretType) -> Data {
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lengthAndData(of: curveType(for: secret.algorithm, length: secret.keySize).data(using: .utf8)!) +
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lengthAndData(of: curveIdentifier(for: secret.algorithm, length: secret.keySize).data(using: .utf8)!) +
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lengthAndData(of: secret.publicKey)
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}
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/// Generates an OpenSSH string representation of the secret.
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/// - Returns: OpenSSH string representation of the secret.
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public func openSSHString<SecretType: Secret>(secret: SecretType, comment: String? = nil) -> String {
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[curveType(for: secret.algorithm, length: secret.keySize), data(secret: secret).base64EncodedString(), comment]
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.compactMap { $0 }
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.joined(separator: " ")
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}
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/// Generates an OpenSSH SHA256 fingerprint string.
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/// - Returns: OpenSSH SHA256 fingerprint string.
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public func openSSHSHA256Fingerprint<SecretType: Secret>(secret: SecretType) -> String {
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// OpenSSL format seems to strip the padding at the end.
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let base64 = Data(SHA256.hash(data: data(secret: secret))).base64EncodedString()
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let paddingRange = base64.index(base64.endIndex, offsetBy: -2)..<base64.endIndex
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let cleaned = base64.replacingOccurrences(of: "=", with: "", range: paddingRange)
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return "SHA256:\(cleaned)"
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}
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/// Generates an OpenSSH MD5 fingerprint string.
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/// - Returns: OpenSSH MD5 fingerprint string.
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public func openSSHMD5Fingerprint<SecretType: Secret>(secret: SecretType) -> String {
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Insecure.MD5.hash(data: data(secret: secret))
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.compactMap { ("0" + String($0, radix: 16, uppercase: false)).suffix(2) }
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.joined(separator: ":")
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}
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}
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extension OpenSSHKeyWriter {
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/// Creates an OpenSSH protocol style data object, which has a length header, followed by the data payload.
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/// - Parameter data: The data payload.
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/// - Returns: OpenSSH data.
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public func lengthAndData(of data: Data) -> Data {
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let rawLength = UInt32(data.count)
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var endian = rawLength.bigEndian
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return Data(bytes: &endian, count: UInt32.bitWidth/8) + data
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}
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/// The fully qualified OpenSSH identifier for the algorithm.
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/// - Parameters:
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/// - algorithm: The algorithm to identify.
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/// - length: The key length of the algorithm.
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/// - Returns: The OpenSSH identifier for the algorithm.
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public func curveType(for algorithm: Algorithm, length: Int) -> String {
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switch algorithm {
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case .ellipticCurve:
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return "ecdsa-sha2-nistp" + String(describing: length)
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}
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}
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/// The OpenSSH identifier for an algorithm.
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/// - Parameters:
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/// - algorithm: The algorithm to identify.
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/// - length: The key length of the algorithm.
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/// - Returns: The OpenSSH identifier for the algorithm.
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private func curveIdentifier(for algorithm: Algorithm, length: Int) -> String {
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switch algorithm {
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case .ellipticCurve:
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return "nistp" + String(describing: length)
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}
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}
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}
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