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:

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

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

1. and the good and secure method which requires to install the certificate chain used here.
2. 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.

---

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 is not included in the default cURL installation. (See this page for further information about TU Claustha-CA)
The certificate chain looks like this:

"Deutsche Telekom Root CA 2" 
+--"DFV-Verein PCA Global -G01" 
   +--"TU Clausthal CA - G02"@
      +--"scm.in.tu-clausthal.de" 

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.

1. Locate the folder where the git executable is installed.
   In this folder there should be a file called "curl-ca-bundle.crt"
   On Windows this is most likely c:\Programs (x86)\Git\bin, on Debian-Linux it is located at /etc/ssl/certs/ca-certificates.crt
   #Download the certificate-chain file, which contains the Telekom-CA, the DFN-CA and the TUC-CA. #

1. Decide if the certificate-chain should be installed system-wide or just user- or account-wide.
   For user-wide installation make a copy of the *.crt file above and place it in your

https://pki.pca.dfn.de/tu-clausthal-ca/cgi-bin/pub/pki?cmd=getStaticPage;name=index;id=4&RA_ID=0

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