/// <summary>
/// Tests the content checksum for validity, throws an exception if it is invalid.
/// </summary>
/// <param name="lines"></param>
private static void EnforceContentChecksum(List <string> lines)
{
if (lines.Count == 0)
{
throw new InvalidOperationException("The checksums file is empty");
}
var contentLine = lines[0];
var contentEntry = CreateFromLine(contentLine);
if (contentEntry == null || contentEntry.FileName != "\\**CONTENT CHECKSUM**")
{
throw new InvalidOperationException($@"""{contentLine}"" is not a valid content checksum line");
}
lines.RemoveAt(0);
var checksumBytes = Encoding.UTF8.GetBytes(String.Concat(lines));
var checksum = ChecksumFileEntry.GenerateChecksum(checksumBytes);
var checksumSize = lines.Sum(r => r.Length);
if (contentEntry.FileSize != checksumSize)
{
throw new InvalidOperationException($"The lines in the checksums file have been altered - was expecting {contentEntry.FileSize} bytes, the lines added up to {checksumSize}");
}
if (contentEntry.Checksum != checksum)
{
throw new InvalidOperationException($"The checksums file has been altered - was expecting a checksum of {contentEntry.Checksum}, it was actually {checksum}");
}
}
private static ChecksumFileEntry CreateFromLine(string line)
{
ChecksumFileEntry result = null;
var slashPosn = line.IndexOf('\\');
if (slashPosn != -1)
{
var chunks = line.Substring(0, slashPosn).Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
if (chunks.Length == 2)
{
result = new ChecksumFileEntry()
{
Checksum = chunks[0],
FileSize = long.Parse(chunks[1]),
FileName = line.Substring(slashPosn)
};
}
}
return(result);
}
