Redmine, Git, Svn Help

h1. SSL certificate handling with GIT

GIT uses cURL internally for transfering files. Unfortunately cURL uses its own certificate-store

and the certificate-chain (Telekom-CA-->DFN-CA-->TU-Clausthal) isn't included by default.

Now, when you try to access a GIT-repository you will get an error similar to this:

Windows

<pre>

$ git clone https://scm.in.tu-clausthal.de/git/stuko1

Cloning into 'stuko1'...

fatal: unable to access 'https://scm.in.tu-clausthal.de/git/stuko1/': SSL certificate problem: unable to get local issuer certificate

</pre>

Linux

<pre>

git clone https://scm.in.tu-clausthal.de/git/testgit

Cloning into 'testgit'...

error: server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt 

CRLfile: none while accessing https://scm.in.tu-clausthal.de/git/testgit/info/refs

</pre>

This is because by default cURL does not know the used certificate chain and rejects the GIT operation.

There are several possibilities to avoid this

# and [[Certificate handling with GIT#the good and secure method|the good and secure method]] which requires to install the certificate chain used here.

# [[the bad and insecure method]] which are based on the fact that GIT/cURL bypasses the SSL certificate verification.

The [[bad and insecure method]] allows a man-in-the-middle-attack and really should be used. You have been warned! Don't even think about using it. 

---

h3(#the good and secure method). The good and secure method to use GIT over HTTPS

GIT uses cURL for transfering files. Unfortunately the root certificate of the certificate chain used here at the "Clausthal University of Technologoy":http://www.tu-clausthal.de is not included in the default cURL installation. ("See this page for further information about TU Claustha-CA":https://doku.tu-clausthal.de/doku.php?id=ssl-zertifikate:start)

The certificate chain looks like this: 

!TUC-Certificate-Chain.png!

<pre>

"Deutsche Telekom Root CA 2"

+--"DFV-Verein PCA Global -G01"

   +--"TU Clausthal CA - G02"@

      +--"scm.in.tu-clausthal.de"

</pre>

In order to securely work with GIT you need to import the certificate chain.

We will provide the step-by-step-manual for most operating systems.

# Download the certificate-chain from the DFN (Deutsches Forschungs Netz)

Right-click on "Zertifikatkette anzeigen" and select "Save target on"

https://pki.pca.dfn.de/tu-clausthal-ca/pub/cacert/chain.txt

# Locate the folder where the git executable is installed.

## On Windows this file is called @curl-ca-bundle.crt@ and its located most likely at @c:\Programs (x86)\Git\bin@

## On Debian-Linux it is is located at @/etc/ssl/certs/ca-certificates.crt@

# Decide if the certificate-chain should be installed system-wide or just user- or account-wide.

## For a system-wide installation just append the certificate-chain from above to this file-

### On Windows open a administrator console. (Windows-Key->Type "cmd"->right-click on it and select "Run as Administrator" from the pop-up)

@cd@ to the download location and type @type chain.txt >> "c:\Program Files (x86)\Git\bin\curl-ca-bundle.crt"@

### On Debian-Linux (as root or sudo)

@cd@ to the doenload location and type @echo chain.txt >> /etc/ssl/certs/ca-certificates.crt@

For user-wide installation make a copy of the @*.crt@ file above and place it in your 

To import the certificate chain for GIT follow these steps:

 1. Locate the file

https://pki.pca.dfn.de/tu-clausthal-ca/pub/cacert/chain_sha1.txt

To import the certificate chain for GIT follow these steps:

or choose one of the following options to skip the certificate verification:

- Temporary ignore ssl certificate verification:

  env GIT_SSL_NO_VERIFY=true git clone https://scm.in.tu-clausthal.de/git/PROJECTNAME

- Disable ssl verfication for one GIT repository (works after first clone):

  git config http.sslVerify false

- Globally disable ssl verification (not recommended!)

  git config --global http.sslVerify false