This is feature is workaround for #2628 (JumpCloud) and some other services
that allow LDAP search only under BindDN user account, but not allow any LDAP
search query in logged user DN context.
Such approach is an alternative to minimal permissions security pattern for
BindDN user.
This commit adds the possibibility to use either the native golang
libraries or ssh-keygen to check public keys. The check is adjusted
depending on the settings, so that only supported keys are let through.
This commit also brings back the blacklist feature, which was removed in
7ef9a05588. This allows to blacklist
algorythms or keys based on the key length. This works with the native
and the ssh-keygen way.
Because of #2179 it also includes a way to adjust the path to
ssh-keygen and the working directory for ssh-keygen. With this,
sysadmins should be able to adjust the settings in a way, that SELinux
is okay with it. In the worst case, they can switch to the native
implementation and only loose support for ed25519 keys at the moment.
There are some other places which need adjustment to utilize the
parameters and the native implementation, but this sets the ground work.
Adam Strzelecki
Florian Kaiser
Gibheer
Unknwon
Martin Hartkorn
Josh Frye
Andrey Nering
techwolf12
Patrik
Saren Currie
Kim "BKC" Carlbäcker
Toni
Julien Pivotto