rspec/rules/S4639/csharp/rule.adoc

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== Noncompliant Code Example

----
using System.IO;
using System.IO.Compression;

public class ZipHelper
{
    public void Extract(ZipFile zipFile, string destinationDirectory)
    {
        foreach (var entry in zipFile.Entries)
        {
            var destinationFileName = Path.GetFullPath(Path.Combine(destinationDirectory, entry.FullName));
            entry.ExtractToFile(destinationFileName); // entry.FullName could contain parent directory references (..) and make the
                                                      // file to be extracted in an arbitrary directory, outside of destinationDirectory
        }
    }
}
----

== Compliant Solution

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using System.IO;
using System.IO.Compression;

public class ZipHelper
{
    public void Extract(ZipFile zipFile, string destinationDirectory)
    {
        foreach (var entry in zipFile.Entries)
        {
            var destinationFileName = Path.GetFullPath(Path.Combine(destinationDirectory, entry.FullName));
            if (destinationFullName.StartsWith(destinationDirectory)) // Do not extract files if the destination file path will be outside of destinationDirectory
            {
                entry.ExtractToFile(destinationFileName); // Compliant, destinationFileName is ensured to be under destinationDirectory
            }
        }
    }
}{code}
----

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