rootless: store also the original GID in the host

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/rootless/rootless_linux.c

@@ -40,6 +40,7 @@ static const char *_unprivileged_user_namespaces = "/proc/sys/kernel/unprivilege
 static int open_files_max_fd;
 fd_set open_files_set;
 static uid_t rootless_uid_init;
+static gid_t rootless_gid_init;
 
 static int
 syscall_setresuid (uid_t ruid, uid_t euid, uid_t suid)
@@ -59,6 +60,12 @@ rootless_uid ()
   return rootless_uid_init;
 }
 
+uid_t
+rootless_gid ()
+{
+  return rootless_gid_init;
+}
+
 static void
 do_pause ()
 {
@@ -224,6 +231,7 @@ static void __attribute__((constructor)) init()
       long pid;
       char buf[12];
       uid_t uid;
+      gid_t gid;
       char path[PATH_MAX];
       const char *const suffix = "/libpod/pause.pid";
       char *cwd = getcwd (NULL, 0);
@@ -263,6 +271,7 @@ static void __attribute__((constructor)) init()
         }
 
       uid = geteuid ();
+      gid = getegid ();
 
       sprintf (path, "/proc/%d/ns/user", pid);
       fd = open (path, O_RDONLY);
@@ -310,6 +319,7 @@ static void __attribute__((constructor)) init()
 
       free (cwd);
       rootless_uid_init = uid;
+      rootless_gid_init = gid;
     }
 }
 
@@ -440,6 +450,7 @@ reexec_userns_join (int userns, int mountns, char *pause_pid_file_path)
 {
   pid_t ppid = getpid ();
   char uid[16];
+  char gid[16];
   char **argv;
   int pid;
   char *cwd = getcwd (NULL, 0);
@@ -451,6 +462,7 @@ reexec_userns_join (int userns, int mountns, char *pause_pid_file_path)
     }
 
   sprintf (uid, "%d", geteuid ());
+  sprintf (gid, "%d", getegid ());
 
   argv = get_cmd_line_args (ppid);
   if (argv == NULL)
@@ -477,6 +489,7 @@ reexec_userns_join (int userns, int mountns, char *pause_pid_file_path)
 
   setenv ("_CONTAINERS_USERNS_CONFIGURED", "init", 1);
   setenv ("_CONTAINERS_ROOTLESS_UID", uid, 1);
+  setenv ("_CONTAINERS_ROOTLESS_GID", gid, 1);
 
   if (prctl (PR_SET_PDEATHSIG, SIGTERM, 0, 0, 0) < 0)
     {
@@ -556,6 +569,7 @@ reexec_in_user_namespace (int ready, char *pause_pid_file_path)
   pid_t ppid = getpid ();
   char **argv;
   char uid[16];
+  char gid[16];
   char *listen_fds = NULL;
   char *listen_pid = NULL;
   bool do_socket_activation = false;
@@ -577,6 +591,7 @@ reexec_in_user_namespace (int ready, char *pause_pid_file_path)
   }
 
   sprintf (uid, "%d", geteuid ());
+  sprintf (gid, "%d", getegid ());
 
   pid = syscall_clone (CLONE_NEWUSER|CLONE_NEWNS|SIGCHLD, NULL);
   if (pid < 0)
@@ -621,6 +636,7 @@ reexec_in_user_namespace (int ready, char *pause_pid_file_path)
 
   setenv ("_CONTAINERS_USERNS_CONFIGURED", "init", 1);
   setenv ("_CONTAINERS_ROOTLESS_UID", uid, 1);
+  setenv ("_CONTAINERS_ROOTLESS_GID", gid, 1);
 
   do
     ret = read (ready, &b, 1) < 0;

pkg/rootless/rootless_linux.go

@@ -25,6 +25,7 @@ import (
 #cgo remoteclient CFLAGS: -DDISABLE_JOIN_SHORTCUT
 #include <stdlib.h>
 extern uid_t rootless_uid();
+extern uid_t rootless_gid();
 extern int reexec_in_user_namespace(int ready, char *pause_pid_file_path);
 extern int reexec_in_user_namespace_wait(int pid);
 extern int reexec_userns_join(int userns, int mountns, char *pause_pid_file_path);
@@ -49,10 +50,12 @@ var (
 func IsRootless() bool {
 	isRootlessOnce.Do(func() {
 		rootlessUIDInit := int(C.rootless_uid())
+		rootlessGIDInit := int(C.rootless_gid())
 		if rootlessUIDInit != 0 {
 			// This happens if we joined the user+mount namespace as part of
 			os.Setenv("_CONTAINERS_USERNS_CONFIGURED", "done")
 			os.Setenv("_CONTAINERS_ROOTLESS_UID", fmt.Sprintf("%d", rootlessUIDInit))
+			os.Setenv("_CONTAINERS_ROOTLESS_GID", fmt.Sprintf("%d", rootlessGIDInit))
 		}
 		isRootless = os.Geteuid() != 0 || os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != ""
 	})
@@ -69,6 +72,23 @@ func GetRootlessUID() int {
 	return os.Geteuid()
 }
 
+// GetRootlessGID returns the GID of the user in the parent userNS
+func GetRootlessGID() int {
+	gidEnv := os.Getenv("_CONTAINERS_ROOTLESS_GID")
+	if gidEnv != "" {
+		u, _ := strconv.Atoi(gidEnv)
+		return u
+	}
+
+	/* If the _CONTAINERS_ROOTLESS_UID is set, assume the gid==uid.  */
+	uidEnv := os.Getenv("_CONTAINERS_ROOTLESS_UID")
+	if uidEnv != "" {
+		u, _ := strconv.Atoi(uidEnv)
+		return u
+	}
+	return os.Getegid()
+}
+
 func tryMappingTool(tool string, pid int, hostID int, mappings []idtools.IDMap) error {
 	path, err := exec.LookPath(tool)
 	if err != nil {

pkg/rootless/rootless_unsupported.go

@@ -24,6 +24,11 @@ func GetRootlessUID() int {
 	return -1
 }
 
+// GetRootlessGID returns the GID of the user in the parent userNS
+func GetRootlessGID() int {
+	return -1
+}
+
 // JoinUserAndMountNS re-exec podman in a new userNS and join the user and mount
 // namespace of the specified PID without looking up its parent.  Useful to join directly
 // the conmon process.  It is a convenience function for JoinUserAndMountNSWithOpts