前几天我遇到了GZipStream doesn't detect corrupt data (even CRC32 passes)?这个问题(这很可能是一个“重复”，我对这个问题百感交集。我也是在标题中添加CRC32的人，但现在回想起来感觉与帖子的其余部分不相称)。在我自己探索了这个问题之后，我认为这个问题比另一个问题最初描述的要严重得多。
我扩展了另一个问题，并使测试代码可以在 LINQPad 下运行，并尝试更好地展示 CRC32 (Cyclic Redundancy Check) 问题(如果确实存在)。 (由于代码只是基于原始代码的轻微修改，因此测试设置/方法可能有缺陷，或者两者都存在另一个奇怪的怪癖/PEBCAK。)
结果很奇怪，因为损坏的数据并不总是导致引发(任何!)异常。请注意，仅有时 CRC32 检查看起来确实“有效”。导致索引超出范围/错误页眉/错误页脚的损坏字节可以被忽略，因为我们可以假设这些字节正在终止 CRC32 检查之前的解压缩(这是完美的)可以理解，即使 IndexOutOfRangeException 可能应该被 InvalidDataException 包装)，所以，
为什么CRC32检查的可靠性明显低于应有的可靠性？(为什么下面会出现“无效数据(无异常)”？)
由于 GZip footer contains CRC32 和未压缩数据的长度似乎是 error detection rate should be "significantly higher" - 也就是说，我不会期望下面是一个失败的案例，更不用说一些未检测到的损坏流了。 (当然，尽快检测到损坏的 Steam 是件好事:但在某些情况下，最终的安全校验和似乎会被完全忽略。)
格式为CorruptByteIndex+FailedDetections:消息:
0+0: System.IO.InvalidDataException:The magic number in GZip header is not correct. Make sure you are passing in a GZip stream. 1+0: System.IO.InvalidDataException:The magic number in GZip header is not correct. Make sure you are passing in a GZip stream. 2+0: System.IO.InvalidDataException:The compression mode specified in GZip header is unknown. 3+0: Good data (No Exception) 4+0: Good data (No Exception) 5+0: Good data (No Exception) 6+0: Good data (No Exception) 7+0: Good data (No Exception) 8+0: Good data (No Exception) 9+0: Good data (No Exception) 10+0: System.IO.InvalidDataException:Unknown block type. Stream might be corrupted. 11+1: Invalid data (No Exception) 12+1: System.IO.InvalidDataException:Found invalid data while decoding. 13+1: System.IO.InvalidDataException:Found invalid data while decoding. 14+1: System.IO.InvalidDataException:Found invalid data while decoding. 15+1: System.IO.InvalidDataException:Found invalid data while decoding. 16+1: System.IO.InvalidDataException:Found invalid data while decoding. 17+2: Invalid data (No Exception) 18+2: System.IO.InvalidDataException:Found invalid data while decoding. 19+2: System.IndexOutOfRangeException:Index was outside the bounds of the array. 20+2: System.IndexOutOfRangeException:Index was outside the bounds of the array. 21+3: Invalid data (No Exception) 22+3: System.IndexOutOfRangeException:Index was outside the bounds of the array. 23+3: System.IndexOutOfRangeException:Index was outside the bounds of the array. 24+4: Invalid data (No Exception) 25+4: System.IndexOutOfRangeException:Index was outside the bounds of the array. 26+4: System.IndexOutOfRangeException:Index was outside the bounds of the array. 27+4: System.IndexOutOfRangeException:Index was outside the bounds of the array. 28+4: System.IndexOutOfRangeException:Index was outside the bounds of the array. 29+5: Invalid data (No Exception) 30+5: System.IndexOutOfRangeException:Index was outside the bounds of the array. 31+6: Invalid data (No Exception) 32+7: Invalid data (No Exception) 33+7: System.IndexOutOfRangeException:Index was outside the bounds of the array. 34+7: System.IndexOutOfRangeException:Index was outside the bounds of the array. 35+7: System.IndexOutOfRangeException:Index was outside the bounds of the array. 36+8: Invalid data (No Exception) 37+8: System.IndexOutOfRangeException:Index was outside the bounds of the array. 38+8: System.IndexOutOfRangeException:Index was outside the bounds of the array. 39+9: Invalid data (No Exception) 40+9: System.IndexOutOfRangeException:Index was outside the bounds of the array. 41+9: System.IndexOutOfRangeException:Index was outside the bounds of the array. 42+10: Invalid data (No Exception) 43+10: System.IO.InvalidDataException:Found invalid data while decoding. 44+10: System.IndexOutOfRangeException:Index was outside the bounds of the array. 45+10: System.IO.InvalidDataException:Found invalid data while decoding. 46+11: Invalid data (No Exception) 47+11: System.IndexOutOfRangeException:Index was outside the bounds of the array. 48+11: System.IndexOutOfRangeException:Index was outside the bounds of the array. 49+11: System.IndexOutOfRangeException:Index was outside the bounds of the array. 50+12: Invalid data (No Exception) 51+12: System.IndexOutOfRangeException:Index was outside the bounds of the array. 52+12: System.IndexOutOfRangeException:Index was outside the bounds of the array. 53+13: Invalid data (No Exception) 54+13: System.IndexOutOfRangeException:Index was outside the bounds of the array. 55+14: Invalid data (No Exception) 56+14: System.IndexOutOfRangeException:Index was outside the bounds of the array. 57+15: Invalid data (No Exception) 58+15: System.IndexOutOfRangeException:Index was outside the bounds of the array. 59+15: System.IndexOutOfRangeException:Index was outside the bounds of the array. 60+16: Invalid data (No Exception) 61+17: Invalid data (No Exception) 62+18: Invalid data (No Exception) 63+19: Invalid data (No Exception) 64+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 65+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 66+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 67+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 68+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 69+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 70+19: System.IO.InvalidDataException:Found invalid data while decoding. 71+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 72+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 73+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 74+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 75+19: System.IO.InvalidDataException:Found invalid data while decoding. 76+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 77+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 78+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 79+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 80+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 81+19: System.IO.InvalidDataException:Found invalid data while decoding. 82+19: System.IndexOutOfRangeException:Index was outside the bounds of the array. 83+20: Invalid data (No Exception) 84+21: Invalid data (No Exception) 85+22: Invalid data (No Exception) 86+22: System.IndexOutOfRangeException:Index was outside the bounds of the array. 87+23: Invalid data (No Exception) 88+24: Invalid data (No Exception) 89+25: Invalid data (No Exception) 90+25: System.IndexOutOfRangeException:Index was outside the bounds of the array. 91+26: Invalid data (No Exception) 92+26: System.IO.InvalidDataException:Found invalid data while decoding. 93+26: System.IndexOutOfRangeException:Index was outside the bounds of the array. 94+27: Invalid data (No Exception) 95+27: System.IndexOutOfRangeException:Index was outside the bounds of the array. 96+27: System.IndexOutOfRangeException:Index was outside the bounds of the array. 97+28: Invalid data (No Exception) 98+28: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 99+28: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 100+29: Invalid data (No Exception) 101+30: Invalid data (No Exception) 102+31: Invalid data (No Exception) 103+32: Invalid data (No Exception) 104+32: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 105+33: Invalid data (No Exception) 106+34: Invalid data (No Exception) 107+35: Invalid data (No Exception) 108+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 109+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 110+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 111+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 112+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 113+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 114+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 115+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 116+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 117+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 118+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 119+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 120+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 121+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 122+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 123+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 124+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 125+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 126+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 127+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 128+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 129+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 130+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 131+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 132+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 133+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 134+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 135+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 136+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 137+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 138+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 139+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 140+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 141+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 142+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 143+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 144+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 145+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 146+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 147+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 148+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 149+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 150+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 151+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 152+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 153+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 154+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 155+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 156+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 157+35: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 158+36: Invalid data (No Exception) 159+36: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 160+36: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 161+37: Invalid data (No Exception) 162+38: Invalid data (No Exception) 163+39: Invalid data (No Exception) 164+40: Invalid data (No Exception) 165+41: Invalid data (No Exception) 166+41: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 167+41: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 168+41: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 169+41: System.IO.InvalidDataException:The CRC in GZip footer does not match the CRC calculated from the decompressed data. 170+41: System.IO.InvalidDataException:The stream size in GZip footer does not match the real stream size. 171+41: System.IO.InvalidDataException:The stream size in GZip footer does not match the real stream size. 172+41: System.IO.InvalidDataException:The stream size in GZip footer does not match the real stream size. 173+41: System.IO.InvalidDataException:The stream size in GZip footer does not match the real stream size.
Here is the test which is copy'n'paste runnable in LINQPad (for .NET 3.5 and 4, use "as C# statements" mode):
string sample = "This is a compression test of microsoft .net gzip compression method and decompression methods";
var encoding = new ASCIIEncoding();
var data = encoding.GetBytes(sample);
string sampleOut = null;
byte[] cmpData;
// Compress
using (var cmpStream = new MemoryStream())
{
using (var hgs = new System.IO.Compression.GZipStream(cmpStream, System.IO.Compression.CompressionMode.Compress))
{
hgs.Write(data, 0, data.Length);
}
cmpData = cmpStream.ToArray();
}
int corruptBytesNotDetected = 0;
// corrupt data byte by byte
for (var byteToCorrupt = 0; byteToCorrupt < cmpData.Length; byteToCorrupt++)
{
var corruptData = new List<byte>(cmpData).ToArray();
// corrupt the data
corruptData[byteToCorrupt]++;
using (var decomStream = new MemoryStream(corruptData))
{
using (var hgs = new System.IO.Compression.GZipStream(decomStream, System.IO.Compression.CompressionMode.Decompress))
{
using (var reader = new StreamReader(hgs))
{
string message;
try
{
sampleOut = reader.ReadToEnd();
// if we get here, the corrupt data was not detected by GZipStream
// ... okay so long as the correct data is extracted
if (!sample.SequenceEqual(sampleOut)) {
corruptBytesNotDetected++;
message = "Invalid data (No Exception)";
} else {
message = "Good data (No Exception)";
}
}
catch(Exception ex)
{
message = (ex.GetType() + ":" + ex.Message);
}
string.Format("{0}+{1}: {2}",
byteToCorrupt, corruptBytesNotDetected, message).Dump();
}
}
}
}
这是 .NET 3.5 中的压缩数据(众所周知，GZipStream 不擅长“压缩”小有效负载，但这是一个“无法修复”问题，因为该流在技术上仍然有效):
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
(而且，只是为了咯咯笑，在 .NET 4 中它会生成一个稍大/不同的压缩流。)
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
附加说明:
在这种情况下，测试可能存在细微缺陷。当 GZipStream “未能检测到损坏”(无异常)时，从 StreamReader 读取的数据为“”(空字符串):在这种情况下，为什么 ReadToEnd() 不 引发异常(IOException 或其他)？
这是否是GZipStream，而是这里“古怪”的StreamReader，或者这仍然是GZipStream的问题(因为不抛出异常)？是否有一些正确的方法可以可靠地处理这个用例？ (考虑当前位置的输入流何时确实为空。)
最佳答案
前言
.NET [4 及以前的版本] 用户在任何情况下都不应使用 Microsoft 提供的 GZipStream 或 DeflateStream 类，除非 Microsoft 将它们完全替换为可用的东西。请改用 DotNetZip 库。
更新前言
.NET Framework 4.5 及更高版本已修复压缩问题，并且 GZipStream 和 DeflateStream 在这些版本中使用 zlib。我不知道下面引用的 CRC 问题是否已修复。
另一个更新
CRC 错误不仅没有得到修复，而且微软已经决定 won't fix它!
我在 Why does my C# gzip produce a larger file than Fiddler or PHP? 中的回复表明此行为并未反射(reflect)出 gzip 损坏检测的正确实现。在所有测试的情况下，正确的实现都会检测到错误。 (该回复还指出了为什么其中七个案例会产生良好的数据。)
另一个问题是:这种“压缩”方法如何从 94 字节字符串产生 174 字节输出？特别是考虑到字符串是如何压缩的——gzip 将其减少到 84 字节，即使有 18 字节 header 和标尾的开销。您能提供 174 字节的十六进制转储吗？
关于.net - 为什么 BCL GZipStream(带有 StreamReader)不能可靠地检测 CRC32 的数据错误？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9471826/