cron not honoring pam_group.so groups

[Jorge Rocha Gualtieri]

When a job is invoked from cron and the pam_group.so is configured to add supplementary groups it DOES NOT work as expected.

pam_group should provide membership based /etc/security/group.conf and it is working fine if you test with login or sudo.

After some tests I've compiled pam_group.so in DEBUG and I can confirm that pam_setcred in being called by cron and the module is adding the expected groups membership.

Then, checking do_command.c of cron I found there is need to call pam_setcred(pamh, PAM_REINITIALIZE_CRED | PAM_SILENT) after fork()

the final patch should be something like

#if defined(USE_PAM)
                if (pamh != NULL) {
                        pam_setcred(pamh, PAM_REINITIALIZE_CRED | PAM_SILENT);
                }
#endif

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: cron 3.0pl1-136ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-65.73-generic 5.4.78
Uname: Linux 5.4.0-65-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: pass
Date: Mon Mar 1 15:49:42 2021
InstallationDate: Installed on 2021-01-21 (39 days ago)
InstallationMedia: Ubuntu-Server 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: cron
UpgradeStatus: No upgrade log present (probably fresh install)