Using GZipStream from DotNetZip to decompress a response from IIS 7.x (HttpWebResponse) with activated gzip compression (Content-Encoding: gzip)
does not recognize data corruption in the stream.
 
I've been testing a lot of compression stuff in the last days and all went well so far. Then i came to the idea to test out the crc check of the data. I have saved the gzip compressed response received from iis to a file (without decompressing it). After i had manipulated those data with a hex editor i opened the file in my program and used GZipStream to decompress it which runs without an error thrown. In that case i had expected to get an exception thrown or something else which indicates that the data is not correct.
 
I then used the same compressed file now using the stream implementation from System.IO.Compression.GZipStream, run the same test and it threw an exception with the message "The CRC in GZip footer does not match the CRC calculated from the decompressed data"
 
It seems to be that DotNetZip is either not checking those CRC or there is an bug which lets the decompression run without any error.
 
Attached the compressed file i used to test the library.