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Add support for byte range requests for DRM protected resources
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,143 @@ | ||
| // | ||
| // CBCDRMInputStream.swift | ||
| // r2-streamer-swift | ||
| // | ||
| // Created by Mickaël Menu on 04.07.19. | ||
| // | ||
| // Copyright 2019 Readium Foundation. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license which is detailed | ||
| // in the LICENSE file present in the project repository where this source code is maintained. | ||
| // | ||
|
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| import Foundation | ||
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| private let AESBlockSize: Int64 = 16 // bytes | ||
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| /// A DRM input stream to read content encrypted with the CBC algorithm. Support random access for byte range requests. | ||
| final class CBCDRMInputStream: DRMInputStream { | ||
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| enum Error: Swift.Error { | ||
| case invalidStream | ||
| case emptyDecryptedData | ||
| case readOutOfRange | ||
| case readEncryptedOutOfRange | ||
| case readFailed | ||
| case decryptionFailed | ||
| } | ||
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| private lazy var plainTextSize: Int64 = { | ||
| guard stream.length >= 2 * AESBlockSize else { | ||
| fail(with: Error.invalidStream) | ||
| return 0 | ||
| } | ||
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| do { | ||
| let readPosition = Int64(stream.length) - 2 * AESBlockSize | ||
| let bufferSize = 2 * AESBlockSize | ||
| var buffer = Array<UInt8>(repeating: 0, count: Int(bufferSize)) | ||
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| stream.open() | ||
| try stream.seek(offset: readPosition, whence: .startOfFile) | ||
| let numberOfBytesRead = stream.read(&buffer, maxLength: Int(bufferSize)) | ||
| let data = Data(bytes: buffer, count: numberOfBytesRead) | ||
| stream.close() | ||
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| guard let decryptedData = try license.decipher(data) else { | ||
| fail(with: Error.emptyDecryptedData) | ||
| return 0 | ||
| } | ||
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| return Int64(stream.length) | ||
| - AESBlockSize // Minus IV or previous block | ||
| - (AESBlockSize - Int64(decryptedData.count)) % AESBlockSize // Minus padding part | ||
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| } catch { | ||
| fail(with: error) | ||
| return 0 | ||
| } | ||
| }() | ||
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| override var length: UInt64 { | ||
| return UInt64(plainTextSize) | ||
| } | ||
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| override func read(_ buffer: UnsafeMutablePointer<UInt8>, maxLength len: Int) -> Int { | ||
| guard hasBytesAvailable else { | ||
| return 0 | ||
| } | ||
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| let len = Int64(len) | ||
| let offset = Int64(self.offset) | ||
| guard offset + len <= length else { | ||
| fail(with: Error.readOutOfRange) | ||
| return -1 | ||
| } | ||
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| // Get offset result offset in the block. | ||
| let blockOffset = offset % AESBlockSize | ||
| // For beginning of the cipher text, IV used for XOR. | ||
| // For cipher text in the middle, previous block used for XOR. | ||
| let readPosition = offset - blockOffset | ||
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| // Count blocks to read. | ||
| // First block for IV or previous block to perform XOR. | ||
| var blocksCount: Int64 = 1 | ||
| var bytesInFirstBlock: Int64 = (AESBlockSize - blockOffset) % AESBlockSize | ||
| if len < bytesInFirstBlock { | ||
| bytesInFirstBlock = 0 | ||
| } | ||
| if bytesInFirstBlock > 0 { | ||
| blocksCount += 1 | ||
| } | ||
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| blocksCount += (len - bytesInFirstBlock) / AESBlockSize | ||
| if (len - bytesInFirstBlock) % AESBlockSize != 0 { | ||
| blocksCount += 1 | ||
| } | ||
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| // Read data from the stream | ||
| var data: Data | ||
| do { | ||
| let bufferSize = blocksCount * AESBlockSize | ||
| var buffer = Array<UInt8>(repeating: 0, count: Int(bufferSize)) | ||
| guard readPosition + bufferSize <= stream.length else { | ||
| fail(with: Error.readEncryptedOutOfRange) | ||
| return -1 | ||
| } | ||
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| stream.open() | ||
| try stream.seek(offset: Int64(readPosition), whence: .startOfFile) | ||
| let numberOfBytesRead = stream.read(&buffer, maxLength: Int(bufferSize)) | ||
| assert(numberOfBytesRead >= 0) | ||
| data = Data(bytes: buffer, count: numberOfBytesRead) | ||
| stream.close() | ||
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| } catch { | ||
| fail(with: Error.readFailed) | ||
| return -1 | ||
| } | ||
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| do { | ||
| guard let decryptedData = try license.decipher(data) else { | ||
| fail(with: Error.emptyDecryptedData) | ||
| return -1 | ||
| } | ||
| data = decryptedData | ||
| } catch { | ||
| fail(with: Error.decryptionFailed) | ||
| return -1 | ||
| } | ||
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| if data.count > len { | ||
| data = data[0..<min(data.count, Int(len))] | ||
| } | ||
| data.copyBytes(to: buffer, count: data.count) | ||
| _offset += UInt64(data.count) | ||
| if _offset >= length { | ||
| _streamStatus = .atEnd | ||
| } | ||
| return data.count | ||
| } | ||
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| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,47 @@ | ||
| // | ||
| // DRMDecoder.swift | ||
| // r2-streamer-swift | ||
| // | ||
| // Created by Alexandre Camilleri on 10/11/17. | ||
| // | ||
| // Copyright 2018 Readium Foundation. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license which is detailed | ||
| // in the LICENSE file present in the project repository where this source code is maintained. | ||
| // | ||
|
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| import Foundation | ||
| import R2Shared | ||
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| /// Decrypt DRM encrypted content. | ||
| class DRMDecoder: Loggable { | ||
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| /// Decode the given stream using DRM. If it fails, just return the | ||
| /// stream unchanged. | ||
| /// | ||
| /// - Parameters: | ||
| /// - input: The input stream. | ||
| /// - resourceLink: The link represented by the stream. | ||
| /// - drm: The DRM object used for decryption. | ||
| /// - Returns: The decrypted stream. | ||
| static func decoding(_ input: SeekableInputStream, of resourceLink: Link, with drm: DRM?) -> SeekableInputStream { | ||
| /// Check if the resource is encrypted. | ||
| guard let drm = drm, | ||
| let license = drm.license, | ||
| let encryption = resourceLink.properties.encryption, | ||
| let originalLength = encryption.originalLength, | ||
| let scheme = encryption.scheme, | ||
| // Check that the encryption schemes of ressource and DRM are the same. | ||
| scheme == drm.scheme.rawValue else | ||
| { | ||
| return input | ||
| } | ||
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| let isDeflated = (encryption.compression == "deflate") | ||
| let isCBC = (encryption.algorithm == "http://www.w3.org/2001/04/xmlenc#aes256-cbc") | ||
| return (isDeflated || !isCBC) | ||
| ? FullDRMInputStream(stream: input, link: resourceLink, license: license, originalLength: originalLength, isDeflated: isDeflated) | ||
| : CBCDRMInputStream(stream: input, link: resourceLink, license: license, originalLength: originalLength) | ||
| } | ||
|
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||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| // | ||
| // DRMInputStream.swift | ||
| // r2-streamer-swift | ||
| // | ||
| // Created by Mickaël Menu on 04.07.19. | ||
| // | ||
| // Copyright 2019 Readium Foundation. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style license which is detailed | ||
| // in the LICENSE file present in the project repository where this source code is maintained. | ||
| // | ||
|
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| import Foundation | ||
| import R2Shared | ||
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| class DRMInputStream: SeekableInputStream, Loggable { | ||
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| let stream: SeekableInputStream | ||
| let link: Link | ||
| let license: DRMLicense | ||
| let originalLength: Int | ||
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| init(stream: SeekableInputStream, link: Link, license: DRMLicense, originalLength: Int) { | ||
| self.stream = stream | ||
| self.link = link | ||
| self.license = license | ||
| self.originalLength = originalLength | ||
| super.init() | ||
| } | ||
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| // MARK: - Seekable | ||
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| override var length: UInt64 { | ||
| return UInt64(originalLength) | ||
| } | ||
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| var _offset: UInt64 = 0 | ||
| override var offset: UInt64 { return _offset } | ||
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| override func seek(offset: Int64, whence: SeekWhence) throws { | ||
| let length = Int64(self.length) | ||
| switch whence { | ||
| case .startOfFile: | ||
| assert(0...length ~= offset) | ||
| _offset = UInt64(offset) | ||
| case .endOfFile: | ||
| assert(-length...0 ~= offset) | ||
| _offset = UInt64(length + offset) | ||
| case .currentPosition: | ||
| let newOffset = Int64(_offset) + offset | ||
| assert(0...length ~= newOffset) | ||
| _offset = UInt64(offset) | ||
| } | ||
| } | ||
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| // MARK: - Stream | ||
|
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| var _streamStatus: Stream.Status = .notOpen | ||
| override var streamStatus: Stream.Status { return _streamStatus } | ||
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| private var _streamError: Error? | ||
| override var streamError: Error? { return _streamError } | ||
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| func fail(with error: Error) { | ||
| _streamStatus = .error | ||
| _streamError = error | ||
| log(.error, "\(type(of: self)): \(link.href): \(error.localizedDescription)") | ||
| } | ||
|
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| override func open() { | ||
| _streamStatus = .open | ||
| } | ||
|
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| override func close() { | ||
| _offset = 0 | ||
| _streamStatus = .notOpen | ||
| } | ||
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| // MARK: - InputStream | ||
|
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| override var hasBytesAvailable: Bool { | ||
| return offset < length | ||
| } | ||
|
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| override func getBuffer(_ buffer: UnsafeMutablePointer<UnsafeMutablePointer<UInt8>?>, length len: UnsafeMutablePointer<Int>) -> Bool { | ||
| return false | ||
| } | ||
|
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| } |
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