[THRIFT-5238] GetHashCode can throw NullReferenceException

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.13.0
• Fix Version/s: 0.14.0
• Component/s: netstd - Compiler

Environment

OS: Windows 10 Pro Version 1903 Build 18362.900

 

• Assignee: Jens Geyer
• Reporter: Lewis Jackson
• Created: 24/Jun/20 11:15
• Updated: 11/Feb/21 22:27
• Resolved: 25/Jun/20 20:11

Description

Thrift generates a setter for each field like this:

    public string WebhooksSecret
    {
      get
      {
        return _WebhooksSecret;
      }
      set
      {
        __isset.WebhooksSecret = true;
        this._WebhooksSecret = value;
      }
    }

But if you set the field to null, it will be marked as set in the isset dictionary. Thrift also overrides GetHashCode() like this:

    public override int GetHashCode() {
      int hashcode = 157;
      unchecked {
        if(__isset.Url)
          hashcode = (hashcode * 397) + Url.GetHashCode();
        if(__isset.WebhooksSecret)
          hashcode = (hashcode * 397) + WebhooksSecret.GetHashCode();
        if(__isset.Username)
          hashcode = (hashcode * 397) + Username.GetHashCode();
        if(__isset.WebhooksTypes)
          hashcode = (hashcode * 397) + TCollections.GetHashCode(WebhooksTypes);
      }
      return hashcode;
    }

Note that it doesn't protect against null, where other overrides like ToString() do:

    public override string ToString()
    {
//...
      if (WebhooksSecret != null && __isset.WebhooksSecret)
      {
        if(!__first) { sb.Append(", "); }
        __first = false;
        sb.Append("WebhooksSecret: ");
        sb.Append(WebhooksSecret);
      }
//...
    }

This can result in the field being set to null then throwing a NullReferenceException if a consumer calls GetHashCode().

I've attached a repro in the form of a unit test library. There are instructions to run this in the README of the zip.

Issue Links

• links to: GitHub Pull Request #2187