Podman uses incorrect path to auth.json

[mtrmac]

/kind bug

Description

After https://github.com/containers/libpod/pull/3760/files , podman always hard-codes SystemContext.AuthFilePath to a non-empty value, overriding the built-in defaults in c/image — but different from the built-in defaults.

E.g. for the ordinary case of an unprivileged user with XDG_RUNTIME_DIR set, the c/image default is /run/user/$UID/containers/auth.json, while the Podman default is /run/user/$UID/auth.json.

This breaks podman login+skopeo, as well as Skopeo integration tests, and presumably any other non-Podman software that relies on podman login.

Steps to reproduce the issue:

1. podman login $registry
2. skopeo inspect docker://$registry/$image
   (or use strace -e 'trace=%file' … |& grep auth to confirm)

Describe the results you received:

In Skopeo debug output,

level=debug msg="Credentials not found"

+ a failure to read data.

Describe the results you expected:

Successful image use.

Additional information you deem important (e.g. issue happens only occasionally):

This does not show up as a Podman failure as long as Podman is consuming its own podman login effects because both the writer and the readers use the same incorrect path.

Package info (e.g. output of rpm -q podman or apt list podman):

podman-1.6.1-2.fc30 as well as current master ( f61e399 ).

[vrothberg]

Thanks for the detailed explanation, @mtrmac! We need to check when we regressed on that and maybe need to backport the fix (Cc: @mheon). It's unlikely that I will find time to look into this today. If others want to pick it up, feel free.