git - How do I use GitHub through harsh proxies?

Question

Given the following constraints, how can I use GitHub from Windows and Unix?

• All access to the internet is restricted to a proxy
• The proxy only allows connections out on port 80 and 443
• CONNECT method is only enabled for 443
• Proxy Authentication is required (NTLM or Basic)

Answer 1

See a “Using Github Through Draconian Proxies (Windows And Unix)” by Jeff Tchang (formerly available from another location), which includes instructions for both Windows and Unix platforms, summarized below.

Unix

1. Download Git.
2. Download and install corkscrew.

3. Edit or create the file ~/.ssh/config and put the following:

   ProxyCommand /usr/bin/corkscrew proxy.example.com 443 %h %p ~/.ssh/myauth
   
   Host github.com
   User git
   Port 22
   Hostname github.com
   IdentityFile "/media/truecrypt1/Keys/GitHubKey.private"
   TCPKeepAlive yes
   IdentitiesOnly yes
   
   Host ssh.github.com
   User git
   Port 443
   Hostname ssh.github.com
   IdentityFile "/media/truecrypt1/Keys/GitHubKey.private"
   TCPKeepAlive yes
   IdentitiesOnly yes
   

4. If everything is setup correctly you should be able to run ssh github.com and see

   Hi user! You’ve successfully authenticated, but GitHub does not provide shell access.
   Connection to github.com closed.

   If this doesn’t work you can run ssh ssh.github.com and get the exact same thing. If the first command didn’t work it means you are using a proxy that blocks CONNECT on port 22. Almost no proxies block CONNECT on port 443 because you need that for SSL.

Windows

1. Download msysgit. Some settings:
   • “Run Git from the Windows Command Prompt”
   • “Use OpenSSH” (this one is very important)
   • Pick your line endings
2. Download connect.c. This tool deserves its own post mostly because of its utter simplicity. It mirrors the open source tool corkscrew and is used for tunneling through proxies. Yes the tool’s name is really called “connect.c.” For Windows users, a pre-compiled binary is available. I put my connect.exe in C:Windowsconnect.exe.
3. Decide whether you like to use the Windows cmd.exe to do stuff or the Cygwin style shell. Or both.

4. Set up the Cygwin Git bash shell.

   For the Cygwin style shell start up the Git icon and edit the file ~/.ssh/config and make sure the file has no extension. Put the following in that file, and note how the paths are specified.

   ProxyCommand /c/windows/connect.exe -H [email protected]:443 %h %p
   
   Host github.com
   User git
   Port 22
   Hostname github.com
   IdentityFile "/c/Keys/GitHubKey.private"
   TCPKeepAlive yes
   IdentitiesOnly yes
   
   Host ssh.github.com
   User git
   Port 443
   Hostname ssh.github.com
   IdentityFile "/c/Keys/GitHubKey.private"
   TCPKeepAlive yes
   IdentitiesOnly yes
   

5. Set up the Windows cmd.exe shell.

   Suppose you don’t like the Git Bash shell. You prefer the cmd.exe interpreter.

   • Go to your config file at C:Documents and Settings.sshconfig
   • Make a copy of it or make a new one. I called mine config-windows

   Put the following in the file, again paying careful attention to path separators and styles.

   ProxyCommand C:/Windows/connect.exe -H [email protected]:443 %h %p
   
   Host github.com
   User git
   Port 22
   Hostname github.com
   IdentityFile "C:KeysGitHubKey.private"
   TCPKeepAlive yes
   IdentitiesOnly yes
   
   Host ssh.github.com
   User git
   Port 443
   Hostname ssh.github.com
   IdentityFile "C:KeysGitHubKey.private"
   TCPKeepAlive yes
   IdentitiesOnly yes
   

For full details, see the full blog post.