Supplemental groups not added for 'podman exec -u <user>'

[owtaylor]

/kind bug

Description

When a container is created with one user, and you run: podman exec -u <otheruser> groups you don't see supplemental groups from /etc/group.

Looking at the code with @mheon, it appears that the intention is that these supplemental groups are supposed to be added - see https://github.com/containers/podman/blob/master/libpod/oci_conmon_exec_linux.go#L719

I initially encountered this in the context of rootless with --userns=keep-id, but it seems to be the same running rootfull and without --userns.

Steps to reproduce the issue:

Run the following script

#!/bin/bash

container=$(podman create -u root fedora:33 sleep 1000)

cleanup() {
    podman stop --time=1 "$container" > /dev/null
    podman rm -f "$container" > /dev/null
}
trap cleanup EXIT

podman start "$container" > /dev/null
podman exec "$container" useradd testuser
podman exec "$container" usermod -G wheel testuser
echo -n "Running 'groups': "
podman exec -u testuser "$container" groups
echo -n "Running 'su -u testuser sh -c groups': "
podman exec -u root "$container" su - testuser sh -c groups

Describe the results you received:

Running 'groups': testuser
Running 'su -u testuser sh -c groups': testuser wheel

Describe the results you expected:

The bare groups command should have shown the right supplemental groups.

Output of podman version:

Version:      3.0.1
API Version:  3.0.0
Go Version:   go1.15.8
Built:        Fri Feb 19 11:56:17 2021
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.19.4
  cgroupManager: cgroupfs
  cgroupVersion: v2
  conmon:
    package: conmon-2.0.26-1.fc33.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.0.26, commit: 777074ecdb5e883b9bec233f3630c5e7fa37d521'
  cpus: 8
  distribution:
    distribution: fedora
    version: "33"
  eventLogger: journald
  hostname: localhost.localdomain
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 1000000
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 1000000
  kernel: 5.10.19-200.fc33.x86_64
  linkmode: dynamic
  memFree: 1262637056
  memTotal: 33436405760
  ociRuntime:
    name: crun
    package: crun-0.18-1.fc33.x86_64
    path: /usr/bin/crun
    version: |-
      crun version 0.18
      commit: 808420efe3dc2b44d6db9f1a3fac8361dde42a95
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    path: /run/user/1000/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    selinuxEnabled: true
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.1.8-1.fc33.x86_64
    version: |-
      slirp4netns version 1.1.8
      commit: d361001f495417b880f20329121e3aa431a8f90f
      libslirp: 4.3.1
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.5.0
  swapFree: 21010198528
  swapTotal: 21082660864
  uptime: 156h 32m 55.35s (Approximately 6.50 days)
registries:
  search:
  - registry.fedoraproject.org
  - registry.access.redhat.com
  - registry.centos.org
  - docker.io
store:
  configFile: /var/home/otaylor/.config/containers/storage.conf
  containerStore:
    number: 10
    paused: 0
    running: 2
    stopped: 8
  graphDriverName: overlay
  graphOptions:
    overlay.mount_program:
      Executable: /usr/bin/fuse-overlayfs
      Package: fuse-overlayfs-1.4.0-1.fc33.x86_64
      Version: |-
        fusermount3 version: 3.9.3
        fuse-overlayfs: version 1.4
        FUSE library version 3.9.3
        using FUSE kernel interface version 7.31
  graphRoot: /var/home/otaylor/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: btrfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 393
  runRoot: /run/user/1000/containers
  volumePath: /var/home/otaylor/.local/share/containers/storage/volumes
version:
  APIVersion: 3.0.0
  Built: 1613753777
  BuiltTime: Fri Feb 19 11:56:17 2021
  GitCommit: ""
  GoVersion: go1.15.8
  OsArch: linux/amd64
  Version: 3.0.1

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

podman-3.0.1-1.fc33.x86_64

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide?

No

[mheon]

Self-assigning

[github-actions]

A friendly reminder that this issue had no activity for 30 days.

[rhatdan]

I just ran your test script and it worked correctly.

$ podman -v
podman version 3.2.0-rc1

$ sh /tmp/test.sh 
Resolved "fedora" as an alias (/etc/containers/registries.conf.d/000-shortnames.conf)
Trying to pull registry.fedoraproject.org/fedora:33...
Getting image source signatures
CopyingCopying blob 863033e5d074 [===============================>--] 60.5MiB / Copying blob 863033e5d074 done  
Copying config 5a4884db42 done  
Writing manifest to image destination
Storing signatures
Running 'groups': testuser wheel
Running 'su -u testuser sh -c groups': testuser wheel