server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none

Source : https://stackoverflow.com/questions/21181231/server-certificate-verification-failed-cafile-etc-ssl-certs-ca-certificates-c#

TLDR:

hostname=XXX
port=443
trust_cert_file_location=`curl-config --ca`

sudo bash -c "echo -n | openssl s_client -showcerts -connect $hostname:$port \
    2>/dev/null  | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'  \
    >> $trust_cert_file_location"

Long answer

The basic reason is that your computer doesn't trust the certificate authority that signed the certificate used on the Gitlab server. This doesn't mean the certificate is suspicious, but it could be self-signed or signed by an institution/company that isn't in the list of your OS's list of CAs. What you have to do to circumvent the problem on your computer is telling it to trust that certificate - if you don't have any reason to be suspicious about it.

You need to check the web certificate used for your gitLab server, and add it to your 

/bin/curl-ca-bundle.crt.

To check if at least the clone works without checking said certificate, you can set:

export GIT_SSL_NO_VERIFY=1
#or
git config --global http.sslverify false

But that would be for testing only, as illustrated in "SSL works with browser, wget, and curl, but fails with git", or in this blog post.

Check your GitLab settings, a in issue 4272.

---

To get that certificate (that you would need to add to your curl-ca-bundle.crt file), type a:

echo -n | openssl s_client -showcerts -connect yourserver.com:YourHttpGilabPort \
  2>/dev/null  | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'

(with 'yourserver.com' being your GitLab server name)

To check the CA (Certificate Authority issuer), type a:

echo -n | openssl s_client -showcerts -connect yourserver.com:YourHttpGilabPort \
  2>/dev/null  | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' \
  | openssl x509 -noout -text | grep "CA Issuers" | head -1

---

Findekano adds in the comments:

to identify the location of curl-ca-bundle.crt, you could use the command

curl-config --ca

---

Also, see my more recent answer "github: server certificate verification failed": you might have to renistall those certificates:

sudo apt-get install --reinstall ca-certificates
sudo mkdir /usr/local/share/ca-certificates/cacert.org
sudo wget -P /usr/local/share/ca-certificates/cacert.org http://www.cacert.org/certs/root.crt http://www.cacert.org/certs/class3.crt
sudo update-ca-certificates
git config --global http.sslCAinfo /etc/ssl/certs/ca-certificates.crt