SUPPORT // –°ertificate key usage violation in Subversion clients built against GnuTLS

Applies to: VisualSVN Server 2.5

Symptoms

Subversion clients receive the following error message when attempting to connect to VisualSVN Server:

svn: OPTIONS of 'https://server.domain.local/svn/repo': SSL handshake failed: SSL error:
Key usage violation in certificate has been detected. (https://server.domain.local)

You may experience the issue if both of the following conditions are met:

  • VisualSVN Server has a self-signed certificate applied and
  • Subversion client is built against the GnuTLS library.
Note
Note GnuTLS library is an alternative to OpenSSL. Most Subversion clients for Windows are built against OpenSSL and are not affected by this issue. While some Subversion packages (available mostly on Linux-based operating systems such as Ubuntu and Debian) are built against GnuTLS and are affected.

Technical background

During the initial setup VisualSVN Server 2.5 generates a self-signed certificate and adds it to the Trusted Root Certification Authorities store on the local machine. To avoid possible security issues, VisualSVN Server makes this self-signed certificate to be valid for server authentication only (by specifying the 'Key Usage' extension). Subversion clients built against GnuTLS don't recognize such certificate and the error occurs.

Workaround

It's not recommended to use a self-signed certificate in a production environment. We advise to use a certificate issued by your domain or a third-party certificate authority instead of a self-signed one.

If you have to use a self-signed certificate please follow the instruction to generate a cerificate without specifying 'Key Usage' extension:

  1. Add the following registry value to the Windows registry:
    • for 32-bit system:

      [HKEY_LOCAL_MACHINE\SOFTWARE\VisualSVN\VisualSVN Server]
      "CreateGnuTLSCompatibleCertificate"=dword:00000001
            
    • for 64-bit system:

      [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\VisualSVN\VisualSVN Server]
      "CreateGnuTLSCompatibleCertificate"=dword:00000001
            
  2. Start VisualSVN Server Manager.
  3. Go to Action | Properties | Certificate.
  4. Click Change certificate... and follow the wizard instructions to generate a new self-signed certificate.

The certificate will be generated without the 'Key Usage' extension and will be compatible both with GnuTLS and OpenSSL.