From aafa80918a245edcbdaceb1191d749570f1872d0 Mon Sep 17 00:00:00 2001 From: Giuseppe Scrivano Date: Mon, 28 Feb 2022 09:48:52 +0100 Subject: [PATCH] do not set the inheritable capabilities The kernel never sets the inheritable capabilities for a process, they are only set by userspace. Emulate the same behavior. Closes: CVE-2022-27649 Signed-off-by: Giuseppe Scrivano --- libpod/oci_conmon_exec_linux.go | 7 +++++-- pkg/specgen/generate/security.go | 7 +++++-- test/e2e/run_test.go | 6 +++--- 3 files changed, 13 insertions(+), 7 deletions(-) diff --git a/libpod/oci_conmon_exec_linux.go b/libpod/oci_conmon_exec_linux.go index aa970bbde2..65123b37e6 100644 --- a/libpod/oci_conmon_exec_linux.go +++ b/libpod/oci_conmon_exec_linux.go @@ -758,11 +758,14 @@ func prepareProcessExec(c *Container, options *ExecOptions, env []string, sessio } else { pspec.Capabilities.Bounding = ctrSpec.Process.Capabilities.Bounding } + + // Always unset the inheritable capabilities similarly to what the Linux kernel does + // They are used only when using capabilities with uid != 0. + pspec.Capabilities.Inheritable = []string{} + if execUser.Uid == 0 { pspec.Capabilities.Effective = pspec.Capabilities.Bounding - pspec.Capabilities.Inheritable = pspec.Capabilities.Bounding pspec.Capabilities.Permitted = pspec.Capabilities.Bounding - pspec.Capabilities.Ambient = pspec.Capabilities.Bounding } else { if user == c.config.User { pspec.Capabilities.Effective = ctrSpec.Process.Capabilities.Effective diff --git a/pkg/specgen/generate/security.go b/pkg/specgen/generate/security.go index 9c67099054..988c298326 100644 --- a/pkg/specgen/generate/security.go +++ b/pkg/specgen/generate/security.go @@ -146,6 +146,10 @@ func securityConfigureGenerator(s *specgen.SpecGenerator, g *generate.Generator, configSpec := g.Config configSpec.Process.Capabilities.Ambient = []string{} + + // Always unset the inheritable capabilities similarly to what the Linux kernel does + // They are used only when using capabilities with uid != 0. + configSpec.Process.Capabilities.Inheritable = []string{} configSpec.Process.Capabilities.Bounding = caplist user := strings.Split(s.User, ":")[0] @@ -153,7 +157,6 @@ func securityConfigureGenerator(s *specgen.SpecGenerator, g *generate.Generator, if (user == "" && s.UserNS.NSMode != specgen.KeepID) || user == "root" || user == "0" { configSpec.Process.Capabilities.Effective = caplist configSpec.Process.Capabilities.Permitted = caplist - configSpec.Process.Capabilities.Inheritable = caplist } else { mergedCaps, err := capabilities.MergeCapabilities(nil, s.CapAdd, nil) if err != nil { @@ -175,12 +178,12 @@ func securityConfigureGenerator(s *specgen.SpecGenerator, g *generate.Generator, } configSpec.Process.Capabilities.Effective = userCaps configSpec.Process.Capabilities.Permitted = userCaps - configSpec.Process.Capabilities.Inheritable = userCaps // Ambient capabilities were added to Linux 4.3. Set ambient // capabilities only when the kernel supports them. if supportAmbientCapabilities() { configSpec.Process.Capabilities.Ambient = userCaps + configSpec.Process.Capabilities.Inheritable = userCaps } } diff --git a/test/e2e/run_test.go b/test/e2e/run_test.go index 91a2eddadf..f4a6e57335 100644 --- a/test/e2e/run_test.go +++ b/test/e2e/run_test.go @@ -498,7 +498,7 @@ var _ = Describe("Podman run", func() { session = podmanTest.Podman([]string{"run", "--rm", "--user", "root", ALPINE, "grep", "CapInh", "/proc/self/status"}) session.WaitWithDefaultTimeout() Expect(session).Should(Exit(0)) - Expect(session.OutputToString()).To(ContainSubstring("00000000a80425fb")) + Expect(session.OutputToString()).To(ContainSubstring("0000000000000000")) session = podmanTest.Podman([]string{"run", "--rm", ALPINE, "grep", "CapBnd", "/proc/self/status"}) session.WaitWithDefaultTimeout() @@ -533,7 +533,7 @@ var _ = Describe("Podman run", func() { session = podmanTest.Podman([]string{"run", "--user=0:0", "--cap-add=DAC_OVERRIDE", "--rm", ALPINE, "grep", "CapInh", "/proc/self/status"}) session.WaitWithDefaultTimeout() Expect(session).Should(Exit(0)) - Expect(session.OutputToString()).To(ContainSubstring("00000000a80425fb")) + Expect(session.OutputToString()).To(ContainSubstring("0000000000000000")) if os.Geteuid() > 0 { if os.Getenv("SKIP_USERNS") != "" { @@ -550,7 +550,7 @@ var _ = Describe("Podman run", func() { session = podmanTest.Podman([]string{"run", "--userns=keep-id", "--privileged", "--rm", ALPINE, "grep", "CapInh", "/proc/self/status"}) session.WaitWithDefaultTimeout() Expect(session).Should(Exit(0)) - Expect(session.OutputToString()).To(ContainSubstring("0000000000000000")) + Expect(session.OutputToString()).To(ContainSubstring("0000000000000002")) session = podmanTest.Podman([]string{"run", "--userns=keep-id", "--cap-add=DAC_OVERRIDE", "--rm", ALPINE, "grep", "CapInh", "/proc/self/status"}) session.WaitWithDefaultTimeout()