rootless: fix exec

We cannot re-exec into a new user namespace to gain privileges and
access an existing as the new namespace is not the owner of the
existing container.

"unshare" is used to join the user namespace of the target container.

The current implementation assumes that the main process of the
container didn't create a new user namespace.

Since in the setup phase we are not running with euid=0, we must skip
the setup for containers/storage.

Closes: https://github.com/containers/libpod/issues/1329

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

Closes: #1331
Approved by: rhatdan

2 files changed, 23 insertions, 0 deletions

diff --git a/pkg/rootless/rootless_linux.go b/pkg/rootless/rootless_linux.go
index 490ddc33e..26f4b0b18 100644
--- a/pkg/rootless/rootless_linux.go
+++ b/pkg/rootless/rootless_linux.go
@@ -34,6 +34,20 @@ func IsRootless() bool {
 	return os.Getuid() != 0 || os.Getenv("_LIBPOD_USERNS_CONFIGURED") != ""
 }
 
+var (
+	skipStorageSetup = false
+)
+
+// SetSkipStorageSetup tells the runtime to not setup containers/storage
+func SetSkipStorageSetup(v bool) {
+	skipStorageSetup = v
+}
+
+// SkipStorageSetup tells if we should skip the containers/storage setup
+func SkipStorageSetup() bool {
+	return skipStorageSetup
+}
+
 // GetRootlessUID returns the UID of the user in the parent userNS
 func GetRootlessUID() int {
 	uidEnv := os.Getenv("_LIBPOD_ROOTLESS_UID")
diff --git a/pkg/rootless/rootless_unsupported.go b/pkg/rootless/rootless_unsupported.go
index b1f075045..11dfd5aa4 100644
--- a/pkg/rootless/rootless_unsupported.go
+++ b/pkg/rootless/rootless_unsupported.go
@@ -21,3 +21,12 @@ func BecomeRootInUserNS() (bool, int, error) {
 func GetRootlessUID() int {
 	return -1
 }
+
+// SetSkipStorageSetup tells the runtime to not setup containers/storage
+func SetSkipStorageSetup(bool) {
+}
+
+// SkipStorageSetup tells if we should skip the containers/storage setup
+func SkipStorageSetup() bool {
+	return false
+}