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C#

C# static code analysis

Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C# code

  • All rules 493
  • Vulnerability46
  • Bug88
  • Security Hotspot24
  • Code Smell335

  • Quick Fix 61
 
Tags
    Impact
      Clean code attribute
        1. Using unsafe code blocks is security-sensitive

           Security Hotspot
        2. Not specifying a timeout for regular expressions is security-sensitive

           Security Hotspot
        3. Hard-coded secrets are security-sensitive

           Security Hotspot
        4. Constructing arguments of system commands from user input is security-sensitive

           Security Hotspot
        5. Deserializing objects without performing data validation is security-sensitive

           Security Hotspot
        6. Disabling ASP.NET "Request Validation" feature is security-sensitive

           Security Hotspot
        7. Allowing requests with excessive content length is security-sensitive

           Security Hotspot
        8. Using publicly writable directories is security-sensitive

           Security Hotspot
        9. Using clear-text protocols is security-sensitive

           Security Hotspot
        10. Having a permissive Cross-Origin Resource Sharing policy is security-sensitive

           Security Hotspot
        11. Expanding archive files without controlling resource consumption is security-sensitive

           Security Hotspot
        12. Configuring loggers is security-sensitive

           Security Hotspot
        13. Using weak hashing algorithms is security-sensitive

           Security Hotspot
        14. Delivering code in production with debug features activated is security-sensitive

           Security Hotspot
        15. Disabling CSRF protections is security-sensitive

           Security Hotspot
        16. Searching OS commands in PATH is security-sensitive

           Security Hotspot
        17. Creating cookies without the "HttpOnly" flag is security-sensitive

           Security Hotspot
        18. Setting loose file permissions is security-sensitive

           Security Hotspot
        19. Using non-standard cryptographic algorithms is security-sensitive

           Security Hotspot
        20. Using pseudorandom number generators (PRNGs) is security-sensitive

           Security Hotspot
        21. Creating cookies without the "secure" flag is security-sensitive

           Security Hotspot
        22. Formatting SQL queries is security-sensitive

           Security Hotspot
        23. Hard-coded credentials are security-sensitive

           Security Hotspot
        24. Using hardcoded IP addresses is security-sensitive

           Security Hotspot

        Expanding archive files without controlling resource consumption is security-sensitive

        intentionality - complete
        security
        Security Hotspot
        • cwe

        Successful Zip Bomb attacks occur when an application expands untrusted archive files without controlling the size of the expanded data, which can lead to denial of service. A Zip bomb is usually a malicious archive file of a few kilobytes of compressed data but turned into gigabytes of uncompressed data. To achieve this extreme compression ratio, attackers will compress irrelevant data (eg: a long string of repeated bytes).

        Ask Yourself Whether

        Archives to expand are untrusted and:

        • There is no validation of the number of entries in the archive.
        • There is no validation of the total size of the uncompressed data.
        • There is no validation of the ratio between the compressed and uncompressed archive entry.

        There is a risk if you answered yes to any of those questions.

        Recommended Secure Coding Practices

        • Define and control the ratio between compressed and uncompressed data, in general the data compression ratio for most of the legit archives is 1 to 3.
        • Define and control the threshold for maximum total size of the uncompressed data.
        • Count the number of file entries extracted from the archive and abort the extraction if their number is greater than a predefined threshold, in particular it’s not recommended to recursively expand archives (an entry of an archive could be also an archive).

        Sensitive Code Example

        using var zipToOpen = new FileStream(@"ZipBomb.zip", FileMode.Open);
        using var archive = new ZipArchive(zipToOpen, ZipArchiveMode.Read);
        foreach (ZipArchiveEntry entry in archive.Entries)
        {
          entry.ExtractToFile("./output_onlyfortesting.txt", true); // Sensitive
        }
        

        Compliant Solution

        int THRESHOLD_ENTRIES = 10000;
        int THRESHOLD_SIZE = 1000000000; // 1 GB
        double THRESHOLD_RATIO = 10;
        int totalSizeArchive = 0;
        int totalEntryArchive = 0;
        
        using var zipToOpen = new FileStream(@"ZipBomb.zip", FileMode.Open);
        using var archive = new ZipArchive(zipToOpen, ZipArchiveMode.Read);
        foreach (ZipArchiveEntry entry in archive.Entries)
        {
          totalEntryArchive ++;
        
          using (Stream st = entry.Open())
          {
            byte[] buffer = new byte[1024];
            int totalSizeEntry = 0;
            int numBytesRead = 0;
        
            do
            {
              numBytesRead = st.Read(buffer, 0, 1024);
              totalSizeEntry += numBytesRead;
              totalSizeArchive += numBytesRead;
              double compressionRatio = totalSizeEntry / entry.CompressedLength;
        
              if(compressionRatio > THRESHOLD_RATIO) {
                // ratio between compressed and uncompressed data is highly suspicious, looks like a Zip Bomb Attack
                break;
              }
            }
            while (numBytesRead > 0);
          }
        
          if(totalSizeArchive > THRESHOLD_SIZE) {
              // the uncompressed data size is too much for the application resource capacity
              break;
          }
        
          if(totalEntryArchive > THRESHOLD_ENTRIES) {
              // too much entries in this archive, can lead to inodes exhaustion of the system
              break;
          }
        }
        

        See

        • OWASP - Top 10 2021 Category A1 - Broken Access Control
        • OWASP - Top 10 2021 Category A5 - Security Misconfiguration
        • OWASP - Top 10 2017 Category A5 - Broken Access Control
        • OWASP - Top 10 2017 Category A6 - Security Misconfiguration
        • CWE - CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)
        • bamsoftware.com - A better Zip Bomb
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