//
|
// 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.
|
//
|
// ASN1 Scanner code is from Asn1Parser.swift from SwiftyRSA
|
|
import Foundation
|
|
extension ASN1 {
|
/// Simple data scanner that consumes bytes from a raw data and keeps an updated position.
|
internal class Scanner {
|
|
enum ScannerError: Error {
|
case outOfBounds
|
}
|
|
let data: Data
|
var index: Int = 0
|
|
/// Returns whether there is no more data to consume
|
var isComplete: Bool {
|
return self.index >= self.data.count
|
}
|
|
/// Creates a scanner with provided data
|
///
|
/// - Parameter data: Data to consume
|
init(data: Data) {
|
self.data = data
|
}
|
|
/// Consumes data of provided length and returns it
|
///
|
/// - Parameter length: length of the data to consume
|
/// - Returns: data consumed
|
/// - Throws: ScannerError.outOfBounds error if asked to consume too many bytes
|
func consume(length: Int) throws -> Data {
|
|
guard length > 0 else {
|
return Data()
|
}
|
|
guard self.index + length <= self.data.count else {
|
throw ScannerError.outOfBounds
|
}
|
|
let subdata = self.data.subdata(in: self.index..<self.index + length)
|
self.index += length
|
return subdata
|
}
|
|
/// Consumes a primitive, definite ASN1 length and returns its value.
|
///
|
/// See http://luca.ntop.org/Teaching/Appunti/asn1.html,
|
///
|
/// - Short form. One octet. Bit 8 has value "0" and bits 7-1 give the length.
|
/// - Long form. Two to 127 octets. Bit 8 of first octet has value "1" and
|
/// bits 7-1 give the number of additional length octets.
|
/// Second and following octets give the length, base 256, most significant digit first.
|
///
|
/// - Returns: Length that was consumed
|
/// - Throws: ScannerError.outOfBounds error if asked to consume too many bytes
|
func consumeLength() throws -> Int {
|
|
let lengthByte = try consume(length: 1).firstByte
|
|
// If the first byte's value is less than 0x80, it directly contains the length
|
// so we can return it
|
guard lengthByte >= 0x80 else {
|
return Int(lengthByte)
|
}
|
|
// If the first byte's value is more than 0x80, it indicates how many following bytes
|
// will describe the length. For instance, 0x85 indicates that 0x85 - 0x80 = 0x05 = 5
|
// bytes will describe the length, so we need to read the 5 next bytes and get their integer
|
// value to determine the length.
|
let nextByteCount = lengthByte - 0x80
|
let length = try consume(length: Int(nextByteCount))
|
|
return length.integer
|
}
|
}
|
}
|
|
internal extension Data {
|
|
/// Returns the first byte of the current data
|
var firstByte: UInt8 {
|
var byte: UInt8 = 0
|
copyBytes(to: &byte, count: MemoryLayout<UInt8>.size)
|
return byte
|
}
|
|
/// Returns the integer value of the current data.
|
/// - Warning: This only supports data up to 4 bytes, as we can only extract 32-bit integers.
|
var integer: Int {
|
|
guard count > 0 else {
|
return 0
|
}
|
|
var int: UInt32 = 0
|
var offset: Int32 = Int32(count - 1)
|
forEach { byte in
|
let byte32 = UInt32(byte)
|
let shifted = byte32 << (UInt32(offset) * 8)
|
int = int | shifted
|
offset -= 1
|
}
|
|
return Int(int)
|
}
|
}
|
