specgen: keep capabilities with --userns=keep-id

if --userns=keep-id is specified and not --user is specified, take the
unprivileged capabilities code path so that ambient capabilities are
honored in the container.

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

pkg/specgen/generate/security.go

@@ -137,7 +137,7 @@ func securityConfigureGenerator(s *specgen.SpecGenerator, g *generate.Generator,
 
 	user := strings.Split(s.User, ":")[0]
 
-	if user == "" || user == "root" || user == "0" {
+	if (user == "" && s.UserNS.NSMode != specgen.KeepID) || user == "root" || user == "0" {
 		configSpec.Process.Capabilities.Effective = caplist
 		configSpec.Process.Capabilities.Permitted = caplist
 	} else {

test/e2e/run_test.go

@@ -335,6 +335,19 @@ var _ = Describe("Podman run", func() {
 		session.WaitWithDefaultTimeout()
 		Expect(session.ExitCode()).To(Equal(0))
 		Expect(session.OutputToString()).To(ContainSubstring("0000000000000000"))
+
+		if os.Geteuid() > 0 {
+			if os.Getenv("SKIP_USERNS") != "" {
+				Skip("Skip userns tests.")
+			}
+			if _, err := os.Stat("/proc/self/uid_map"); err != nil {
+				Skip("User namespaces not supported.")
+			}
+			session = podmanTest.Podman([]string{"run", "--userns=keep-id", "--cap-add=DAC_OVERRIDE", "--rm", ALPINE, "grep", "CapAmb", "/proc/self/status"})
+			session.WaitWithDefaultTimeout()
+			Expect(session.ExitCode()).To(Equal(0))
+			Expect(session.OutputToString()).To(ContainSubstring("0000000000000002"))
+		}
 	})
 
 	It("podman run user capabilities test with image", func() {