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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,117 @@ | ||
| // Copyright 2020 CoreOffice contributors | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| import Crypto | ||
| import CryptoSwift | ||
| import Foundation | ||
| import OLEKit | ||
|
|
||
| extension Crypto.Digest { | ||
| var data: Data { Data(makeIterator()) } | ||
| } | ||
|
|
||
| struct AgileInfo: Decodable { | ||
| struct KeyData: Decodable { | ||
| let saltValue: Data | ||
| let hashAlgorithm: String | ||
| } | ||
|
|
||
| struct EncryptedKey: Decodable { | ||
| let spinCount: UInt32 | ||
| let encryptedKeyValue: Data | ||
| let saltValue: Data | ||
| let hashAlgorithm: String | ||
| let keyBits: Int | ||
| } | ||
|
|
||
| struct KeyEncryptors: Decodable { | ||
| struct KeyEncryptor: Decodable { | ||
| let encryptedKey: EncryptedKey | ||
| } | ||
|
|
||
| let keyEncryptor: [KeyEncryptor] | ||
| } | ||
|
|
||
| let keyData: KeyData | ||
| let keyEncryptors: KeyEncryptors | ||
|
|
||
| func secretKey(password: String) throws -> [UInt8] { | ||
| let block3 = Data([0x14, 0x6E, 0x0B, 0xE7, 0xAB, 0xAC, 0xD0, 0xD6]) | ||
|
|
||
| guard let encryptedKey = keyEncryptors.keyEncryptor.first?.encryptedKey else { | ||
| throw CryptoOfficeError.encryptedKeyNotSpecifiedForAgileEncryption | ||
| } | ||
|
|
||
| let algorithm = encryptedKey.hashAlgorithm.lowercased() | ||
|
|
||
| guard algorithm == "sha512" else { | ||
| throw CryptoOfficeError.hashAlgorithmNotSupported(actual: algorithm, expected: ["sha512"]) | ||
| } | ||
| guard let passwordData = password.data(using: .utf16LittleEndian) | ||
| else { throw CryptoOfficeError.cantEncodePassword(encoding: .utf16LittleEndian) } | ||
|
|
||
| // Initial round sha512(salt + password) | ||
| var hash = SHA512.hash(data: encryptedKey.saltValue + passwordData) | ||
|
|
||
| // Iteration of 0 -> spincount-1; hash = sha512(iterator + hash) | ||
| for i in 0..<encryptedKey.spinCount { | ||
| let spin = DataWriter() | ||
| spin.write(i) | ||
| hash = SHA512.hash(data: spin.data + hash.data) | ||
| } | ||
|
|
||
| hash = SHA512.hash(data: hash.data + block3) | ||
|
|
||
| // truncate to bitsize | ||
| let decryptionKey = hash.data[0..<(encryptedKey.keyBits / 8)].bytes | ||
|
|
||
| let aes = try CryptoSwift.AES( | ||
| key: decryptionKey, | ||
| blockMode: CBC(iv: encryptedKey.saltValue.bytes), | ||
| padding: .noPadding | ||
| ) | ||
| let result = try aes.decrypt(encryptedKey.encryptedKeyValue.bytes) | ||
| return result | ||
| } | ||
|
|
||
| func decrypt(_ reader: DataReader, secretKey: [UInt8]) throws -> Data { | ||
| let segmentLength: UInt32 = 4096 | ||
|
|
||
| let totalSize: UInt32 = reader.read() | ||
| let lastSegmentSize = totalSize % segmentLength | ||
|
|
||
| reader.seek(toOffset: 8) | ||
|
|
||
| var result = Data() | ||
| let totalSegments = totalSize / segmentLength + (lastSegmentSize > 0 ? 1 : 0) | ||
|
|
||
| for i in 0..<totalSegments { | ||
| let segmentIndex = DataWriter() | ||
| segmentIndex.write(i) | ||
|
|
||
| let iv = (keyData.saltValue + segmentIndex.data).sha512()[0..<16].bytes | ||
| let aes = try AES(key: secretKey, blockMode: CBC(iv: iv)) | ||
|
|
||
| let chunk: Data | ||
| if i == totalSegments - 1 { | ||
| chunk = reader.readDataToEnd() | ||
| } else { | ||
| chunk = reader.readData(ofLength: Int(segmentLength)) | ||
| } | ||
| try result.append(Data(aes.decrypt(chunk.bytes))) | ||
| } | ||
|
|
||
| return result | ||
| } | ||
| } |
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