I don't think this can be done easily

The way pam works is the program (sshd in this case) starts the pam context with a specific name. Looking at sshd source it seems this is __progname for sshd which should be the basename of the executable. There does not seem to be a separate authentication stack for sftp part specifically. So it does not matter if you create a pam.d/sftp configuration as sshd is not programmed to look for it.

sshd can however be configured to limit ssh access and allow sftp based on a users group. So this could be achieved by having the sftp only users in a specific user group.

Kontakt Kevin Vasko via FreeIPA-users (<freeipa-users@lists.fedorahosted.org>) kirjutas kuupäeval T, 16. mai 2023 kell 19:45:

Try to make this simple.

Have a HBAC, have the "Who" set to a user, have the "Accessing" set to a server.

Have the "Via Service" set to "sshd". The user can ssh into the server no issue.

I want to limit this user to only being able to sftp into this server (no direct ssh).

If I swap the "Via Service" from the sshd service to sftp that user is now denied. They cannot access the server via sftp or ssh. I would expect it to deny ssh access but allow sftp.

I did copy "cp /etc/pam.d/sshd /etc/pam.d/sftp" as I saw it mentioned here https://freeipa-users.redhat.narkive.com/tFQFZmNu/hbac-service-allowed-despite-not-listed but that didn't seem to work.

Can you point me to the instructions on how to make the HBAC work with a particular service (e.g. sftp)?
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