secretive/SecretKit/Common/OpenSSH/OpenSSHKeyWriter.swift

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import Foundation
import CryptoKit
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// For the moment, only supports ecdsa-sha2-nistp256 and ecdsa-sha2-nistp386 keys
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public struct OpenSSHKeyWriter {
public init() {
}
public func data<SecretType: Secret>(secret: SecretType) -> Data {
lengthAndData(of: curveType(for: secret.algorithm, length: secret.keySize).data(using: .utf8)!) +
lengthAndData(of: curveIdentifier(for: secret.algorithm, length: secret.keySize).data(using: .utf8)!) +
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lengthAndData(of: secret.publicKey)
}
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public func openSSHString<SecretType: Secret>(secret: SecretType, comment: String? = nil) -> String {
[curveType(for: secret.algorithm, length: secret.keySize), data(secret: secret).base64EncodedString(), comment]
.compactMap { $0 }
.joined(separator: " ")
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}
public func openSSHSHA256Fingerprint<SecretType: Secret>(secret: SecretType) -> String {
// OpenSSL format seems to strip the padding at the end.
let base64 = Data(SHA256.hash(data: data(secret: secret))).base64EncodedString()
let paddingRange = base64.index(base64.endIndex, offsetBy: -2)..<base64.endIndex
let cleaned = base64.replacingOccurrences(of: "=", with: "", range: paddingRange)
return "SHA256:\(cleaned)"
}
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: ":")
}
}
extension OpenSSHKeyWriter {
public func lengthAndData(of data: Data) -> Data {
let rawLength = UInt32(data.count)
var endian = rawLength.bigEndian
return Data(bytes: &endian, count: UInt32.bitWidth/8) + data
}
public func curveIdentifier(for algorithm: Algorithm, length: Int) -> String {
switch algorithm {
case .ellipticCurve:
return "nistp" + String(describing: length)
}
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}
public func curveType(for algorithm: Algorithm, length: Int) -> String {
switch algorithm {
case .ellipticCurve:
return "ecdsa-sha2-nistp" + String(describing: length)
}
}
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}