rootless: raise error if newuidmap/newgidmap are not installed

it was reported on IRC that Podman on Ubuntu failed as
newuidmap/newgidmap were not installed by default.

Raise an error if we are not allowing single mappings (used only by
the tests suite) and any of the binaries is not present.

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

1 files changed, 20 insertions, 6 deletions

diff --git a/pkg/rootless/rootless_linux.go b/pkg/rootless/rootless_linux.go
index 85b0ef392..07002da3f 100644
--- a/pkg/rootless/rootless_linux.go
+++ b/pkg/rootless/rootless_linux.go
@@ -74,7 +74,7 @@ func GetRootlessUID() int {
 func tryMappingTool(tool string, pid int, hostID int, mappings []idtools.IDMap) error {
 	path, err := exec.LookPath(tool)
 	if err != nil {
-		return err
+		return errors.Wrapf(err, "cannot find %s", tool)
 	}
 
 	appendTriplet := func(l []string, a, b, c int) []string {
@@ -92,7 +92,11 @@ func tryMappingTool(tool string, pid int, hostID int, mappings []idtools.IDMap)
 		Path: path,
 		Args: args,
 	}
-	return cmd.Run()
+
+	if err := cmd.Run(); err != nil {
+		return errors.Wrapf(err, "cannot setup namespace using %s", tool)
+	}
+	return nil
 }
 
 // JoinNS re-exec podman in a new userNS and join the user namespace of the specified
@@ -191,11 +195,13 @@ func BecomeRootInUserNS() (bool, int, error) {
 		return false, -1, errors.Errorf("cannot re-exec process")
 	}
 
+	allowSingleIDMapping := os.Getenv("PODMAN_ALLOW_SINGLE_ID_MAPPING_IN_USERNS") != ""
+
 	var uids, gids []idtools.IDMap
 	username := os.Getenv("USER")
 	if username == "" {
 		user, err := user.LookupId(fmt.Sprintf("%d", os.Getuid()))
-		if err != nil && os.Getenv("PODMAN_ALLOW_SINGLE_ID_MAPPING_IN_USERNS") == "" {
+		if err != nil && !allowSingleIDMapping {
 			if os.IsNotExist(err) {
 				return false, 0, errors.Wrapf(err, "/etc/subuid or /etc/subgid does not exist, see subuid/subgid man pages for information on these files")
 			}
@@ -206,7 +212,7 @@ func BecomeRootInUserNS() (bool, int, error) {
 		}
 	}
 	mappings, err := idtools.NewIDMappings(username, username)
-	if os.Getenv("PODMAN_ALLOW_SINGLE_ID_MAPPING_IN_USERNS") == "" {
+	if !allowSingleIDMapping {
 		if err != nil {
 			return false, -1, err
 		}
@@ -236,7 +242,11 @@ func BecomeRootInUserNS() (bool, int, error) {
 
 	uidsMapped := false
 	if mappings != nil && uids != nil {
-		uidsMapped = tryMappingTool("newuidmap", pid, os.Getuid(), uids) == nil
+		err := tryMappingTool("newuidmap", pid, os.Getuid(), uids)
+		if !allowSingleIDMapping && err != nil {
+			return false, 0, err
+		}
+		uidsMapped = err == nil
 	}
 	if !uidsMapped {
 		setgroups := fmt.Sprintf("/proc/%d/setgroups", pid)
@@ -254,7 +264,11 @@ func BecomeRootInUserNS() (bool, int, error) {
 
 	gidsMapped := false
 	if mappings != nil && gids != nil {
-		gidsMapped = tryMappingTool("newgidmap", pid, os.Getgid(), gids) == nil
+		err := tryMappingTool("newgidmap", pid, os.Getgid(), gids)
+		if !allowSingleIDMapping && err != nil {
+			return false, 0, err
+		}
+		gidsMapped = err == nil
 	}
 	if !gidsMapped {
 		gidMap := fmt.Sprintf("/proc/%d/gid_map", pid)