56 lines
2.0 KiB
Swift
56 lines
2.0 KiB
Swift
// Copyright © 2022 Rangeproof Pty Ltd. All rights reserved.
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import Foundation
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import SessionUtilitiesKit
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// MARK: - Decoding
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public extension Data {
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func removePadding() -> Data {
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let bytes: [UInt8] = self.bytes
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var paddingStart: Int = self.count
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for i in 0..<(self.count - 1) {
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let targetIndex: Int = ((self.count - 1) - i)
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if bytes[targetIndex] == 0x80 {
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paddingStart = targetIndex
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break
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}
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else if bytes[targetIndex] != 0x00 {
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SNLog("Failed to remove padding, returning unstripped padding");
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return self
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}
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}
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return self.prefix(upTo: paddingStart)
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}
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func paddedMessageBody() -> Data {
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// From
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// https://github.com/signalapp/TextSecure/blob/master/libtextsecure/src/main/java/org/whispersystems/textsecure/internal/push/PushTransportDetails.java#L55
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// NOTE: This is dumb. We have our own padding scheme, but so does the cipher.
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// The +1 -1 here is to make sure the Cipher has room to add one padding byte,
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// otherwise it'll add a full 16 extra bytes.
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let paddedMessageLength: Int = (self.paddedMessageLength(self.count + 1) - 1)
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var paddedMessage: Data = Data(count: paddedMessageLength)
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let paddingByte: UInt8 = 0x80
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paddedMessage[0..<self.count] = Data(self.bytes)
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paddedMessage[self.count..<(self.count + 1)] = Data([paddingByte])
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return paddedMessage
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}
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private func paddedMessageLength(_ unpaddedLength: Int) -> Int {
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let messageLengthWithTerminator: Int = (unpaddedLength + 1)
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var messagePartCount: Int = (messageLengthWithTerminator / 160)
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if CGFloat(messageLengthWithTerminator).truncatingRemainder(dividingBy: 160) != 0 {
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messagePartCount += 1
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}
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return (messagePartCount * 160)
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}
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}
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