DERCodable Protocols

Sources/CryptoSwift/PEM/DER.swift

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+//
+//  CryptoSwift
+//
+//  Copyright (C) Marcin Krzyżanowski <marcin@krzyzanowskim.com>
+//  This software is provided 'as-is', without any express or implied warranty.
+//
+//  In no event will the authors be held liable for any damages arising from the use of this software.
+//
+//  Permission is granted to anyone to use this software for any purpose,including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:
+//
+//  - The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation is required.
+//  - Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+//  - This notice may not be removed or altered from any source or binary distribution.
+//
+
+import Foundation
+
+/// Conform to this protocol if your type can both be instantiated and expressed as an ASN1 DER representation.
+public protocol DERCodable: DERDecodable, DEREncodable { }
+
+/// Conform to this protocol if your type can be instantiated from a ASN1 DER representation
+public protocol DERDecodable {
+  /// The keys primary ASN1 object identifier (ex: for RSA Keys --> 'rsaEncryption' --> [0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01])
+  static var primaryObjectIdentifier: Array<UInt8> { get }
+  /// The keys secondary ASN1 object identifier (ex: for RSA Keys --> 'null' --> nil)
+  static var secondaryObjectIdentifier: Array<UInt8>? { get }
+
+  /// Instantiates an instance of your Public Key when given a DER representation of your Public Key
+  init(publicDER: Array<UInt8>) throws
+  /// Instantiates an instance of your Private Key when given a DER representation of your Private Key
+  init(privateDER: Array<UInt8>) throws
+}
+
+/// Conform to this protocol if your type can be described in an ASN1 DER representation
+public protocol DEREncodable {
+  /// The keys primary ASN1 object identifier (ex: for RSA Keys --> 'rsaEncryption' --> [0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01])
+  static var primaryObjectIdentifier: Array<UInt8> { get }
+  /// The keys secondary ASN1 object identifier (ex: for RSA Keys --> 'null' --> nil)
+  static var secondaryObjectIdentifier: Array<UInt8>? { get }
+
+  /// Returns the DER encoded representation of the Public Key
+  func publicKeyDER() throws -> Array<UInt8>
+  /// Returns the DER encoded representation of the Private Key
+  func privateKeyDER() throws -> Array<UInt8>
+
+  /// A semantically similar function that mimics the functionality of Apple's `Security` framework's `SecKeyCopyExternalRepresentation` function
+  /// - Note: If called on a Private Key, this method will return the Private Keys DER Representation. Likewise, if called on a Public Key, this method will return the Public Keys DER Representation
+  /// - Note: If you'd like to export the Public Keys DER from a Private Key, use the `publicKeyExternalRepresentation()` function
+  func externalRepresentation() throws -> Data
+  /// A semantically similar function that mimics the functionality of Apple's `Security` framework's `SecKeyCopyExternalRepresentation` function
+  /// - Note: This function only ever exports the Public Key's DER representation. If called on a Private Key, the corresponding Public Key will be extracted and exported.
+  func publicKeyExternalRepresentation() throws -> Data
+}
+
+extension DEREncodable {
+  func externalRepresentation() throws -> Data {
+    do { return try Data(self.privateKeyDER()) } catch {
+      return try Data(self.publicKeyDER())
+    }
+  }
+
+  func publicKeyExternalRepresentation() throws -> Data {
+    try Data(self.publicKeyDER())
+  }
+}
+
+struct DER {
+  /// Integer to Octet String Primitive
+  /// - Parameters:
+  ///   - x: nonnegative integer to be converted
+  ///   - size: intended length of the resulting octet string
+  /// - Returns: corresponding octet string of length xLen
+  /// - Note: https://datatracker.ietf.org/doc/html/rfc3447#section-4.1
+  internal static func i2osp(x: [UInt8], size: Int) -> [UInt8] {
+    var modulus = x
+    while modulus.count < size {
+      modulus.insert(0x00, at: 0)
+    }
+    if modulus[0] >= 0x80 {
+      modulus.insert(0x00, at: 0)
+    }
+    return modulus
+  }
+
+  /// Integer to Octet String Primitive
+  /// - Parameters:
+  ///   - x: nonnegative integer to be converted
+  ///   - size: intended length of the resulting octet string
+  /// - Returns: corresponding octet string of length xLen
+  /// - Note: https://datatracker.ietf.org/doc/html/rfc3447#section-4.1
+  internal static func i2ospData(x: [UInt8], size: Int) -> Data {
+    return Data(DER.i2osp(x: x, size: size))
+  }
+}