77 lines
2.9 KiB
C#
77 lines
2.9 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="Utf16StringValidator.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//------------------------------------------------------------------------------
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namespace System.Web.Util {
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using System;
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// This class contains utility methods for dealing with security contexts when crossing AppDomain boundaries.
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internal static class Utf16StringValidator {
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private const char UNICODE_NULL_CHAR = '\0';
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private const char UNICODE_REPLACEMENT_CHAR = '\uFFFD';
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private static readonly bool _skipUtf16Validation = AppSettings.AllowRelaxedUnicodeDecoding;
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public static string ValidateString(string input) {
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return ValidateString(input, _skipUtf16Validation);
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}
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// only internal for unit testing
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internal static string ValidateString(string input, bool skipUtf16Validation) {
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if (skipUtf16Validation || String.IsNullOrEmpty(input)) {
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return input;
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}
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// locate the first surrogate character
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int idxOfFirstSurrogate = -1;
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for (int i = 0; i < input.Length; i++) {
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if (Char.IsSurrogate(input[i])) {
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idxOfFirstSurrogate = i;
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break;
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}
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}
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// fast case: no surrogates = return input string
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if (idxOfFirstSurrogate < 0) {
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return input;
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}
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// slow case: surrogates exist, so we need to validate them
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char[] chars = input.ToCharArray();
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for (int i = idxOfFirstSurrogate; i < chars.Length; i++) {
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char thisChar = chars[i];
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// If this character is a low surrogate, then it was not preceded by
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// a high surrogate, so we'll replace it.
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if (Char.IsLowSurrogate(thisChar)) {
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chars[i] = UNICODE_REPLACEMENT_CHAR;
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continue;
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}
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if (Char.IsHighSurrogate(thisChar)) {
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// If this character is a high surrogate and it is followed by a
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// low surrogate, allow both to remain.
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if (i + 1 < chars.Length && Char.IsLowSurrogate(chars[i + 1])) {
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i++; // skip the low surrogate also
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continue;
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}
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// If this character is a high surrogate and it is not followed
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// by a low surrogate, replace it.
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chars[i] = UNICODE_REPLACEMENT_CHAR;
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continue;
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}
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// Otherwise, this is a non-surrogate character and just move to the
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// next character.
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}
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return new String(chars);
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}
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}
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}
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