Github authentication failed with user www-data

Question

I'm setting up a hook between Github and my server, which can auto pull new commits when the script triggered by Github requests.

It's all setting finished, like ssh-keys, git origin. I can pull a new commit from my private repo hosted on Github by running git pull origin master. It's works fine with the shell.

But when I write that command into a deploy.php file, it can be triggered by Github, but with error message.

Host key verification failed. fatal: Could not read from remote repository. 
Please make sure you have the correct access rights and the repository exists.

After that, I run a command whoami through the php file, it returns user www-data.

Actually, I generate a key for www-data user, and put them in /var/www/.ssh, also copied id_rsa.pub and pasted it to Github, still have an authentication failure.

• nginx
• All files are set to belong www-data:www-data
• I have add www-data's public key to the repo's deploy keys.

The deploy.php command

shell_exec("cd /var/www/html/tinfo/; git pull origin master 2>&1;");

My question is

1. How to create a key for www-data?
2. Is www-data's .ssh directory /var/www/.ssh?
3. If I'm not wrong, why does github refuse my connection? I guess it's related about the user www-data who execute deploy.php file and run commands through PHP.
4. When talk to Github server, does www-data not sent its private key to the server?

Thank you so much.

Answer 1

This problem solved with adding GitHub to known hosts according to Benyi's comment.

ssh-keyscan -t rsa github.com >> /var/www/.ssh/known_hosts

You should specify ssh key firstly. After that, you should do git tasks what you want.

1-) Ssh keys are not user specific. So you can create rsa key pair everywhere. Public key should be copied to github. Private key should be placed on your host.

2-) In linux environment, default .ssh folder path is under the users home directory. If you do not specify user's home folder, it should be in /home/www-data/.ssh. If you can not access this folder you should specify your ssh key that have written in my example.

3-) In linux environment, deploy.php runned by user who executing nginx process. Commonly apache2 and nginx processes executed by www-data user.

4-) You should specify your ssh key path for sending this key file for authorization when you talk with github server.