75 lines
2.3 KiB
C#
75 lines
2.3 KiB
C#
/*
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* Copyright (c) 2022 ETH Zürich, Educational Development and Technology (LET)
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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using System;
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using System.Security.Cryptography;
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using System.Text;
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using SafeExamBrowser.Configuration.Contracts;
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using SafeExamBrowser.Configuration.Contracts.Cryptography;
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using SafeExamBrowser.Logging.Contracts;
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using SafeExamBrowser.Settings;
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namespace SafeExamBrowser.Configuration.Cryptography
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{
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public class KeyGenerator : IKeyGenerator
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{
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private readonly SHA256Managed algorithm;
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private readonly AppConfig appConfig;
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private readonly ILogger logger;
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private readonly AppSettings settings;
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private string browserExamKey;
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public KeyGenerator(AppConfig appConfig, ILogger logger, AppSettings settings)
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{
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this.algorithm = new SHA256Managed();
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this.appConfig = appConfig;
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this.logger = logger;
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this.settings = settings;
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}
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public string CalculateBrowserExamKeyHash(string url)
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{
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var urlWithoutFragment = url.Split('#')[0];
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var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(urlWithoutFragment + (browserExamKey ?? ComputeBrowserExamKey())));
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var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
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return key;
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}
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public string CalculateConfigurationKeyHash(string url)
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{
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var urlWithoutFragment = url.Split('#')[0];
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var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(urlWithoutFragment + settings.Browser.ConfigurationKey));
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var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
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return key;
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}
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private string ComputeBrowserExamKey()
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{
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var salt = settings.Browser.BrowserExamKeySalt;
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if (salt == default(byte[]))
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{
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salt = new byte[0];
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logger.Warn("The current configuration does not contain a salt value for the browser exam key!");
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}
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using (var algorithm = new HMACSHA256(salt))
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{
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var hash = algorithm.ComputeHash(Encoding.UTF8.GetBytes(appConfig.CodeSignatureHash + appConfig.ProgramBuildVersion + settings.Browser.ConfigurationKey));
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var key = BitConverter.ToString(hash).ToLower().Replace("-", string.Empty);
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browserExamKey = key;
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return browserExamKey;
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}
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}
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}
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}
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