git pull SSL Certificate Problem

Source

git pull SSL Certificate Problem

When trying to git pull pkgsrc repo from GitHub I saw an SSL error:

user@host:~/opt/pkgsrc$ git pull
fatal: unable to access 'https://github.com/jsonn/pkgsrc.git/': SSL certificate problem: unable to get local issuer certificate

I tested this guide on Ubuntu 14.04 with Nix package manager.

Note: I was using a git version pulled in from Nix. The git from Ubuntu was working just fine.

Investigation

I remembered reading a blog post on a similar problem: How Expired Root Certificates Broke My Python App Build. It served as a great guide to figure out how to investigate the issue.

I used OpenSSL to establish a connection with GitHub:

user@host:~$ openssl s_client -connect www.github.com:443

And this was the output:

CONNECTED(00000003)
depth=1 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert SHA2 Extended Validation Server CA
verify error:num=20:unable to get local issuer certificate
verify return:0
---
Certificate chain
 0 s:/businessCategory=Private Organization/1.3.6.1.4.1.311.60.2.1.3=US/1.3.6.1.4.1.311.60.2.1.2=Delaware/serialNumber=5157550/street=548 4th Street/postalCode=94107/C=US/ST=California/L=San Francisco/O=GitHub, Inc./CN=github.com
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
 1 s:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=/businessCategory=Private Organization/1.3.6.1.4.1.311.60.2.1.3=US/1.3.6.1.4.1.311.60.2.1.2=Delaware/serialNumber=5157550/street=548 4th Street/postalCode=94107/C=US/ST=California/L=San Francisco/O=GitHub, Inc./CN=github.com
issuer=/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
---
No client certificate CA names sent
---
SSL handshake has read 3233 bytes and written 433 bytes
---
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : ECDHE-RSA-AES128-GCM-SHA256
    Session-ID: 97BB21B046B18D8C2B1943528B10D5111E778100D5F77383ADB1F7E551F238B6
    Session-ID-ctx:
    Master-Key: E2036EB4845D6EFFA7C74FBBE9DE0D0BD3187AAA6BE74D7C2914B8A691E6774D77019A9E1DE64C32E8054BC2CF8A7CA4
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1418841529
    Timeout   : 300 (sec)
    Verify return code: 20 (unable to get local issuer certificate)
---

The most significant line in the output was verify error:num=20:unable to get local issuer certificate. Somewhere along the way I found out that I needed to copy/paste from the above output all text between (and including) -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- and save to a file, say cert.pem.

Thus I embarked on a highly dangerous next step. I can't say for sure but I think this step is very risky because we'll be subverting the chain of trust necessary in TLS. Instead of using a trusted CA certificate provided by the OS we'll take the certificate above on its face value and trust that it's the right one.

Again, this was part of the investigation. DO NOT attempt to do this for your daily work:

user@host:~$ openssl s_client -CAfile cert.pem -connect www.github.com:443

Now the output was:

CONNECTED(00000003)
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert High Assurance EV Root CA
verify return:1
depth=1 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert SHA2 Extended Validation Server CA
verify return:1
depth=0 businessCategory = Private Organization, 1.3.6.1.4.1.311.60.2.1.3 = US, 1.3.6.1.4.1.311.60.2.1.2 = Delaware, serialNumber = 5157550, street = 548 4th Street, postalCode = 94107, C = US, ST = California, L = San Francisco, O = "GitHub, Inc.", CN = github.com
verify return:1
---
Certificate chain
 0 s:/businessCategory=Private Organization/1.3.6.1.4.1.311.60.2.1.3=US/1.3.6.1.4.1.311.60.2.1.2=Delaware/serialNumber=5157550/street=548 4th Street/postalCode=94107/C=US/ST=California/L=San Francisco/O=GitHub, Inc./CN=github.com
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
 1 s:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=/businessCategory=Private Organization/1.3.6.1.4.1.311.60.2.1.3=US/1.3.6.1.4.1.311.60.2.1.2=Delaware/serialNumber=5157550/street=548 4th Street/postalCode=94107/C=US/ST=California/L=San Francisco/O=GitHub, Inc./CN=github.com
issuer=/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
---
No client certificate CA names sent
---
SSL handshake has read 3233 bytes and written 433 bytes
---
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : ECDHE-RSA-AES128-GCM-SHA256
    Session-ID: 2F1D12E2A233BAC86EC18BB0DA99F58930EAEB7FC1A5F09C935DABCEC05E0F15
    Session-ID-ctx:
    Master-Key: 77B96521720C5603C66F32CB1A60393230E94BEBE924ACAC953C701791DEC90DEC45792940AA13AFCF67D70442A91981
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1418841619
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---

Note the Verify return code: 0 (ok) in the output above. Things were already looking better. But hold on. Did you notice "DigiCert High Assurance EV Root CA" and "DigiCert SHA2 Extended Validation Server CA" under CN fields towards the top of the output? This indicated to me that if I can use the OS provided CA certificates with either of these names then I'll be on the right path.

I looked under the /etc/ssl/certs directory:

user@host:~$ ls /etc/ssl/certs/Digi*

And found the following:

/etc/ssl/certs/DigiCert_Assured_ID_Root_CA.pem
/etc/ssl/certs/DigiCert_High_Assurance_EV_Root_CA.pem
/etc/ssl/certs/Digital_Signature_Trust_Co._Global_CA_3.pem
/etc/ssl/certs/DigiCert_Global_Root_CA.pem
/etc/ssl/certs/Digital_Signature_Trust_Co._Global_CA_1.pem

We have a match! /etc/ssl/certs/DigiCert_High_Assurance_EV_Root_CA.pem matches exactly what we are looking for.

Now we'll repeat our experiment above and instead of using cert.pem we'll use this certificate instead:

user@host:~$ openssl s_client -CAfile /etc/ssl/certs/DigiCert_High_Assurance_EV_Root_CA.pem -connect www.github.com:443

Success. The output was:

CONNECTED(00000003)
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert High Assurance EV Root CA
verify return:1
depth=1 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert SHA2 Extended Validation Server CA
verify return:1
depth=0 businessCategory = Private Organization, 1.3.6.1.4.1.311.60.2.1.3 = US, 1.3.6.1.4.1.311.60.2.1.2 = Delaware, serialNumber = 5157550, street = 548 4th Street, postalCode = 94107, C = US, ST = California, L = San Francisco, O = "GitHub, Inc.", CN = github.com
verify return:1
---
Certificate chain
 0 s:/businessCategory=Private Organization/1.3.6.1.4.1.311.60.2.1.3=US/1.3.6.1.4.1.311.60.2.1.2=Delaware/serialNumber=5157550/street=548 4th Street/postalCode=94107/C=US/ST=California/L=San Francisco/O=GitHub, Inc./CN=github.com
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
 1 s:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=/businessCategory=Private Organization/1.3.6.1.4.1.311.60.2.1.3=US/1.3.6.1.4.1.311.60.2.1.2=Delaware/serialNumber=5157550/street=548 4th Street/postalCode=94107/C=US/ST=California/L=San Francisco/O=GitHub, Inc./CN=github.com
issuer=/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert SHA2 Extended Validation Server CA
---
No client certificate CA names sent
---
SSL handshake has read 3233 bytes and written 433 bytes
---
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-GCM-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : ECDHE-RSA-AES128-GCM-SHA256
    Session-ID: 7217112B561A388D2B01DD424A05053E1715746C34928CAF2F33498DE957002F
    Session-ID-ctx:
    Master-Key: 29A03D8A9B3F49130B18342BD25D300193DB4EE54F39FCD4BEA5B5CD3563A951C242FE3C081928858DD1E2AB69FDA7C8
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1418846185
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---

We now know that git should use this CA certificate when connecting to GitHub.

Solution: Set env variable for git

I found two solutions from git problems (certificate).

The first solution is to specify which CA certificate file to use, similar to what we did above:

user@host:~/opt/pkgsrc$ env GIT_SSL_CAINFO=/etc/ssl/certs/DigiCert_High_Assurance_EV_Root_CA.pem git pull

The second solution is insecure and NOT recommended:

user@host:~/opt/pkgsrc$ env GIT_SSL_NO_VERIFY=true git pull

Install CA certificate bundle in Nix

If like me you're using the Nix package manager, first install cacert:

user@host:~$ nix-env -i cacert

Save the environment variable to use the CA certificate bundle in .bashrc:

user@host:~$ echo export GIT_SSL_CAINFO=$HOME/.nix-profile/etc/ca-bundle.crt >> $HOME/.bashrc
user@host:~$ source ~/.bashrc

Now git pull works successfully:

user@host:~$ cd ~/opt/pkgsrc
user@host:~/opt/pkgsrc$ git pull