145 lines
3.6 KiB
C#
145 lines
3.6 KiB
C#
/*
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* Copyright (c) 2018 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.IO;
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using System.Text;
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using SafeExamBrowser.Contracts.Configuration;
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using SafeExamBrowser.Contracts.Configuration.Settings;
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using SafeExamBrowser.Contracts.Logging;
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namespace SafeExamBrowser.Configuration.DataFormats
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{
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public partial class BinaryFormat : IDataFormat
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{
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private const int PREFIX_LENGTH = 4;
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private IDataCompressor compressor;
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private ILogger logger;
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public BinaryFormat(IDataCompressor compressor, ILogger logger)
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{
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this.compressor = compressor;
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this.logger = logger;
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}
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public bool CanParse(Stream data)
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{
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try
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{
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var longEnough = data.Length > PREFIX_LENGTH;
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if (longEnough)
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{
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var prefix = ParsePrefix(data);
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var success = TryDetermineFormat(prefix, out FormatType format);
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logger.Debug($"'{data}' starting with '{prefix}' does {(success ? string.Empty : "not ")}match the binary format.");
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return success;
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}
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logger.Debug($"'{data}' is not long enough ({data.Length} bytes) to match the binary format.");
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}
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catch (Exception e)
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{
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logger.Error($"Failed to determine whether '{data}' with {data.Length / 1000.0} KB data matches the binary format!", e);
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}
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return false;
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}
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public LoadStatus TryParse(Stream data, out Settings settings, string password = null)
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{
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var prefix = ParsePrefix(data);
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var success = TryDetermineFormat(prefix, out FormatType format);
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settings = default(Settings);
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if (success)
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{
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if (compressor.IsCompressed(data))
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{
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data = compressor.Decompress(data);
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}
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data = new SubStream(data, PREFIX_LENGTH, data.Length - PREFIX_LENGTH);
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// TODO: Try to abstract (Parser -> Binary, Xml, ...; DataBlock -> Password, PlainData, ...) once fully implemented!
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switch (format)
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{
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case FormatType.Password:
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case FormatType.PasswordConfigureClient:
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return ParsePassword(data, format, out settings, password);
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case FormatType.PlainData:
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return ParsePlainData(data, out settings);
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case FormatType.PublicKeyHash:
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return ParsePublicKeyHash(data, out settings, password);
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case FormatType.PublicKeyHashSymmetricKey:
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return ParsePublicKeyHashWithSymmetricKey(data, out settings, password);
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}
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}
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logger.Error($"'{data}' starting with '{prefix}' does not match the binary format!");
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return LoadStatus.InvalidData;
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}
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private string ParsePrefix(Stream data)
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{
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var prefixData = new byte[PREFIX_LENGTH];
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if (compressor.IsCompressed(data))
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{
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prefixData = compressor.Peek(data, PREFIX_LENGTH);
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}
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else
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{
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data.Seek(0, SeekOrigin.Begin);
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data.Read(prefixData, 0, PREFIX_LENGTH);
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}
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return Encoding.UTF8.GetString(prefixData);
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}
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private bool TryDetermineFormat(string prefix, out FormatType format)
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{
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format = default(FormatType);
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switch (prefix)
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{
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case "pswd":
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format = FormatType.Password;
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return true;
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case "pwcc":
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format = FormatType.PasswordConfigureClient;
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return true;
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case "plnd":
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format = FormatType.PlainData;
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return true;
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case "pkhs":
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format = FormatType.PublicKeyHash;
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return true;
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case "phsk":
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format = FormatType.PublicKeyHashSymmetricKey;
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return true;
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}
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return false;
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}
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private enum FormatType
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{
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Password = 1,
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PasswordConfigureClient,
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PlainData,
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PublicKeyHash,
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PublicKeyHashSymmetricKey
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}
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}
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}
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