conf: Add --runas option, changing to given UID and GID if started as root

On some systems, user and group "nobody" might not be available. The
new --runas option allows to override the default "nobody" choice if
started as root.

Now that we allow this, drop the initgroups() call that was used to
add any additional groups for the given user, as that might now
grant unnecessarily broad permissions. For instance, several
distributions have a "kvm" group to allow regular user access to
/dev/kvm, and we don't need that in passt or pasta.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/passt.h b/passt.h
index 69e334d..e541341 100644
--- a/passt.h
+++ b/passt.h
@@ -106,6 +106,8 @@ enum passt_modes {
  * @sock_path:		Path for UNIX domain socket
  * @pcap:		Path for packet capture file
  * @pid_file:		Path to PID file, empty string if not configured
+ * @uid:		UID we should drop to, if started as root
+ * @gid:		GID we should drop to, if started as root
  * @pasta_netns_fd:	File descriptor for network namespace in pasta mode
  * @pasta_userns_fd:	Descriptor for user namespace to join, -1 once joined
  * @netns_only:		In pasta mode, don't join or create a user namespace
@@ -170,6 +172,9 @@ struct ctx {
 	char pcap[PATH_MAX];
 	char pid_file[PATH_MAX];
 
+	uid_t uid;
+	uid_t gid;
+
 	int pasta_netns_fd;
 	int pasta_userns_fd;
 	int netns_only;