pam_mkhomedir not handled during Dropbear session

[sefabre]

We are using Dropbear in a Scarthgap Yocto image (version 2022.83). Our system includes the following configuration in /etc/pam.d/common-session:

session required pam_mkhomedir.so skel=/etc/skel/ umask=0022

When connecting via SSH using Dropbear, we encounter the following error:

Failed chdir '/home/admin': No such file or directory

The home directory is expected to be automatically created by pam_mkhomedir.so, but this does not occur when using Dropbear. However, the directory is correctly created when using OpenSSH or when logging in via the local console.
We have also tested moving the pam_mkhomedir.so line to different PAM configuration files (/etc/pam.d/login, common-account, common-session, and dropbear) without success. In Yocto, pam_start seems to be invoked with /etc/pam.d/dropbear file.

This leads us to the following questions:

• Does Dropbear manage PAM sessions properly (given that Yocto configures common-auth and common-account by default)?
• Is there a way to enable pam_mkhomedir.so functionality with Dropbear, other than pre-creating the home directory?

[mkj]

Dropbear currently doesn't handle PAM sessions. Session open probably wouldn't be too hard to add, but pam_close_session() is hard since Dropbear is running with user privileges post-auth.