================
libgit2 / buster
================

Testing ssh backend:

libssh2 in buster has a problem with (RSA) public key authentifaction. [1]
Details about this can be found in [2] and [3], yielding the error message
"Unable to send userauth-publickey request" when e.g trying to clone
a git repo over ssh for testing purposes.

Workaround is to have the key in PEM format, e.g create it with

ssh-keygen -p -m PEM -f ~/.ssh/id_rsa

For testing, pygit2 or the examples in libgit2/examples can be used.
I've installed gitolite3 as something to connect too…

Note, when the server is in known_host, the host key type needs also
to be either rsa or dss… libssh won't understand others and validation
will fail. I've put into my test VM's .ssh/config::

	Host localhost
	    HostKeyAlgorithms ssh-dss,ssh-rsa

to hint ssh to use only supported keys and ssh'ed to localhost to populate
known_hosts.

----------------------------------
testing with the libgit2 examples:
----------------------------------

The build system is broken (it triee to link network/common.o two times, I've just manually linked it…)
and network/common.c, function cred_acquire_cb() needs to be adapted to utilize ssh auth, e.g::

	--- a/examples/network/common.c
	+++ b/examples/network/common.c
	@@ -55,13 +55,16 @@ error:
	 
	 int cred_acquire_cb(git_cred **out,
		        const char * UNUSED(url),
	-               const char * UNUSED(username_from_url),
	+               const char * username_from_url,
		        unsigned int UNUSED(allowed_types),
		        void * UNUSED(payload))
	 {
		char *username = NULL, *password = NULL;
		int error;
	 
	+        error = git_cred_ssh_key_new(out, username_from_url, "/home/tobi/.ssh/id_rsa.pub", "/home/tobi/.ssh/id_rsa", "");
	+        return error;
	+
		printf("Username: ");
		if (readline(&username) < 0) {
		        fprintf(stderr, "Unable to read username: %s", strerror(errno));

------
pygit2
------

simple test.py::

	import pygit2

	class MyCallbacks(pygit2.RemoteCallbacks):

	    def credentials(self, url, username_from_url, allowed_types):
		    return pygit2.Keypair("gitolite3", "/home/tobi/.ssh/id_rsa.pub", "/home/tobi/.ssh/id_rsa", "")

	print("Cloning pygit2 over ssh with the username in the URL")
	pygit2.clone_repository("ssh://gitolite3@localhost/gitolite-admin.git", "gitolite-admin.git",
		                callbacks=MyCallbacks())



[1] /usr/include/libssh2.h indicates it only supports RSA and DSS… I did not try DSS.
[2] https://www.libssh2.org/mail/libssh2-devel-archive-2019-03/0013.shtml
[3] https://github.com/libgit2/pygit2/issues/836

| Copyright (C) 2023  Tobias Frost