From 541252afa701850f6691933d575c5c24ed0b17c1 Mon Sep 17 00:00:00 2001 From: Matthew Heon Date: Mon, 5 Apr 2021 15:49:35 -0400 Subject: Ensure that `--userns=keep-id` sets user in config One of the side-effects of the `--userns=keep-id` command is switching the default user of the container to the UID of the user running Podman (though this can still be overridden by the `--user` flag). However, it did this by setting the UID and GID in the OCI spec, and not by informing Libpod of its intention to switch users via the `WithUser()` option. Because of this, a lot of the code that should have triggered when the container ran with a non-root user was not triggering. In the case of the issue that this fixed, the code to remove capabilities from non-root users was not triggering. Adjust the keep-id code to properly inform Libpod of our intention to use a non-root user to fix this. Also, fix an annoying race around short-running exec sessions where Podman would always print a warning that the exec session had already stopped. Fixes #9919 Signed-off-by: Matthew Heon --- libpod/container_exec.go | 27 +++++++- libpod/container_validate.go | 6 ++ libpod/oci_conmon_exec_linux.go | 124 +++++++++++++++++++++++++++++++++++++ libpod/oci_conmon_linux.go | 120 ----------------------------------- pkg/specgen/generate/namespaces.go | 10 +++ test/e2e/exec_test.go | 14 ++++- 6 files changed, 178 insertions(+), 123 deletions(-) diff --git a/libpod/container_exec.go b/libpod/container_exec.go index bb43287d9..8d8ed14aa 100644 --- a/libpod/container_exec.go +++ b/libpod/container_exec.go @@ -696,6 +696,24 @@ func (c *Container) ExecResize(sessionID string, newSize define.TerminalSize) er return errors.Wrapf(define.ErrExecSessionStateInvalid, "cannot resize container %s exec session %s as it is not running", c.ID(), session.ID()) } + // The exec session may have exited since we last updated. + // Needed to prevent race conditions around short-running exec sessions. + running, err := c.ociRuntime.ExecUpdateStatus(c, session.ID()) + if err != nil { + return err + } + if !running { + session.State = define.ExecStateStopped + + if err := c.save(); err != nil { + logrus.Errorf("Error saving state of container %s: %v", c.ID(), err) + } + + return errors.Wrapf(define.ErrExecSessionStateInvalid, "cannot resize container %s exec session %s as it has stopped", c.ID(), session.ID()) + } + + // Make sure the exec session is still running. + return c.ociRuntime.ExecAttachResize(c, sessionID, newSize) } @@ -720,8 +738,13 @@ func (c *Container) Exec(config *ExecConfig, streams *define.AttachStreams, resi logrus.Debugf("Sending resize events to exec session %s", sessionID) for resizeRequest := range resize { if err := c.ExecResize(sessionID, resizeRequest); err != nil { - // Assume the exec session went down. - logrus.Warnf("Error resizing exec session %s: %v", sessionID, err) + if errors.Cause(err) == define.ErrExecSessionStateInvalid { + // The exec session stopped + // before we could resize. + logrus.Infof("Missed resize on exec session %s, already stopped", sessionID) + } else { + logrus.Warnf("Error resizing exec session %s: %v", sessionID, err) + } return } } diff --git a/libpod/container_validate.go b/libpod/container_validate.go index 245121a91..aae96ae85 100644 --- a/libpod/container_validate.go +++ b/libpod/container_validate.go @@ -126,5 +126,11 @@ func (c *Container) validate() error { } } + // If User in the OCI spec is set, require that c.config.User is set for + // security reasons (a lot of our code relies on c.config.User). + if c.config.User == "" && (c.config.Spec.Process.User.UID != 0 || c.config.Spec.Process.User.GID != 0) { + return errors.Wrapf(define.ErrInvalidArg, "please set User explicitly via WithUser() instead of in OCI spec directly") + } + return nil } diff --git a/libpod/oci_conmon_exec_linux.go b/libpod/oci_conmon_exec_linux.go index 173edba2b..b43316951 100644 --- a/libpod/oci_conmon_exec_linux.go +++ b/libpod/oci_conmon_exec_linux.go @@ -2,18 +2,23 @@ package libpod import ( "fmt" + "io/ioutil" "net/http" "os" "os/exec" "path/filepath" + "strings" "syscall" "time" + "github.com/containers/common/pkg/capabilities" "github.com/containers/common/pkg/config" "github.com/containers/podman/v3/libpod/define" "github.com/containers/podman/v3/pkg/errorhandling" + "github.com/containers/podman/v3/pkg/lookup" "github.com/containers/podman/v3/pkg/util" "github.com/containers/podman/v3/utils" + spec "github.com/opencontainers/runtime-spec/specs-go" "github.com/pkg/errors" "github.com/sirupsen/logrus" "golang.org/x/sys/unix" @@ -654,3 +659,122 @@ func attachExecHTTP(c *Container, sessionID string, r *http.Request, w http.Resp } } } + +// prepareProcessExec returns the path of the process.json used in runc exec -p +// caller is responsible to close the returned *os.File if needed. +func prepareProcessExec(c *Container, options *ExecOptions, env []string, sessionID string) (*os.File, error) { + f, err := ioutil.TempFile(c.execBundlePath(sessionID), "exec-process-") + if err != nil { + return nil, err + } + pspec := new(spec.Process) + if err := JSONDeepCopy(c.config.Spec.Process, pspec); err != nil { + return nil, err + } + pspec.SelinuxLabel = c.config.ProcessLabel + pspec.Args = options.Cmd + + // We need to default this to false else it will inherit terminal as true + // from the container. + pspec.Terminal = false + if options.Terminal { + pspec.Terminal = true + } + if len(env) > 0 { + pspec.Env = append(pspec.Env, env...) + } + + if options.Cwd != "" { + pspec.Cwd = options.Cwd + } + + var addGroups []string + var sgids []uint32 + + // if the user is empty, we should inherit the user that the container is currently running with + user := options.User + if user == "" { + logrus.Debugf("Set user to %s", c.config.User) + user = c.config.User + addGroups = c.config.Groups + } + + overrides := c.getUserOverrides() + execUser, err := lookup.GetUserGroupInfo(c.state.Mountpoint, user, overrides) + if err != nil { + return nil, err + } + + if len(addGroups) > 0 { + sgids, err = lookup.GetContainerGroups(addGroups, c.state.Mountpoint, overrides) + if err != nil { + return nil, errors.Wrapf(err, "error looking up supplemental groups for container %s exec session %s", c.ID(), sessionID) + } + } + + // If user was set, look it up in the container to get a UID to use on + // the host + if user != "" || len(sgids) > 0 { + if user != "" { + for _, sgid := range execUser.Sgids { + sgids = append(sgids, uint32(sgid)) + } + } + processUser := spec.User{ + UID: uint32(execUser.Uid), + GID: uint32(execUser.Gid), + AdditionalGids: sgids, + } + + pspec.User = processUser + } + + ctrSpec, err := c.specFromState() + if err != nil { + return nil, err + } + + allCaps, err := capabilities.BoundingSet() + if err != nil { + return nil, err + } + if options.Privileged { + pspec.Capabilities.Bounding = allCaps + } else { + pspec.Capabilities.Bounding = ctrSpec.Process.Capabilities.Bounding + } + 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 + pspec.Capabilities.Inheritable = ctrSpec.Process.Capabilities.Effective + pspec.Capabilities.Permitted = ctrSpec.Process.Capabilities.Effective + pspec.Capabilities.Ambient = ctrSpec.Process.Capabilities.Effective + } + } + + hasHomeSet := false + for _, s := range pspec.Env { + if strings.HasPrefix(s, "HOME=") { + hasHomeSet = true + break + } + } + if !hasHomeSet { + pspec.Env = append(pspec.Env, fmt.Sprintf("HOME=%s", execUser.Home)) + } + + processJSON, err := json.Marshal(pspec) + if err != nil { + return nil, err + } + + if err := ioutil.WriteFile(f.Name(), processJSON, 0644); err != nil { + return nil, err + } + return f, nil +} diff --git a/libpod/oci_conmon_linux.go b/libpod/oci_conmon_linux.go index 1c7089e5d..f26ca67ce 100644 --- a/libpod/oci_conmon_linux.go +++ b/libpod/oci_conmon_linux.go @@ -22,7 +22,6 @@ import ( "text/template" "time" - "github.com/containers/common/pkg/capabilities" "github.com/containers/common/pkg/config" conmonConfig "github.com/containers/conmon/runner/config" "github.com/containers/podman/v3/libpod/define" @@ -30,7 +29,6 @@ import ( "github.com/containers/podman/v3/pkg/cgroups" "github.com/containers/podman/v3/pkg/checkpoint/crutils" "github.com/containers/podman/v3/pkg/errorhandling" - "github.com/containers/podman/v3/pkg/lookup" "github.com/containers/podman/v3/pkg/rootless" "github.com/containers/podman/v3/pkg/util" "github.com/containers/podman/v3/utils" @@ -1195,124 +1193,6 @@ func (r *ConmonOCIRuntime) createOCIContainer(ctr *Container, restoreOptions *Co return nil } -// prepareProcessExec returns the path of the process.json used in runc exec -p -// caller is responsible to close the returned *os.File if needed. -func prepareProcessExec(c *Container, options *ExecOptions, env []string, sessionID string) (*os.File, error) { - f, err := ioutil.TempFile(c.execBundlePath(sessionID), "exec-process-") - if err != nil { - return nil, err - } - pspec := new(spec.Process) - if err := JSONDeepCopy(c.config.Spec.Process, pspec); err != nil { - return nil, err - } - pspec.SelinuxLabel = c.config.ProcessLabel - pspec.Args = options.Cmd - - // We need to default this to false else it will inherit terminal as true - // from the container. - pspec.Terminal = false - if options.Terminal { - pspec.Terminal = true - } - if len(env) > 0 { - pspec.Env = append(pspec.Env, env...) - } - - if options.Cwd != "" { - pspec.Cwd = options.Cwd - } - - var addGroups []string - var sgids []uint32 - - // if the user is empty, we should inherit the user that the container is currently running with - user := options.User - if user == "" { - user = c.config.User - addGroups = c.config.Groups - } - - overrides := c.getUserOverrides() - execUser, err := lookup.GetUserGroupInfo(c.state.Mountpoint, user, overrides) - if err != nil { - return nil, err - } - - if len(addGroups) > 0 { - sgids, err = lookup.GetContainerGroups(addGroups, c.state.Mountpoint, overrides) - if err != nil { - return nil, errors.Wrapf(err, "error looking up supplemental groups for container %s exec session %s", c.ID(), sessionID) - } - } - - // If user was set, look it up in the container to get a UID to use on - // the host - if user != "" || len(sgids) > 0 { - if user != "" { - for _, sgid := range execUser.Sgids { - sgids = append(sgids, uint32(sgid)) - } - } - processUser := spec.User{ - UID: uint32(execUser.Uid), - GID: uint32(execUser.Gid), - AdditionalGids: sgids, - } - - pspec.User = processUser - } - - ctrSpec, err := c.specFromState() - if err != nil { - return nil, err - } - - allCaps, err := capabilities.BoundingSet() - if err != nil { - return nil, err - } - if options.Privileged { - pspec.Capabilities.Bounding = allCaps - } else { - pspec.Capabilities.Bounding = ctrSpec.Process.Capabilities.Bounding - } - 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 - pspec.Capabilities.Inheritable = ctrSpec.Process.Capabilities.Effective - pspec.Capabilities.Permitted = ctrSpec.Process.Capabilities.Effective - pspec.Capabilities.Ambient = ctrSpec.Process.Capabilities.Effective - } - } - - hasHomeSet := false - for _, s := range pspec.Env { - if strings.HasPrefix(s, "HOME=") { - hasHomeSet = true - break - } - } - if !hasHomeSet { - pspec.Env = append(pspec.Env, fmt.Sprintf("HOME=%s", execUser.Home)) - } - - processJSON, err := json.Marshal(pspec) - if err != nil { - return nil, err - } - - if err := ioutil.WriteFile(f.Name(), processJSON, 0644); err != nil { - return nil, err - } - return f, nil -} - // configureConmonEnv gets the environment values to add to conmon's exec struct // TODO this may want to be less hardcoded/more configurable in the future func (r *ConmonOCIRuntime) configureConmonEnv(ctr *Container, runtimeDir string) ([]string, []*os.File) { diff --git a/pkg/specgen/generate/namespaces.go b/pkg/specgen/generate/namespaces.go index 845dfdad7..b52e8d100 100644 --- a/pkg/specgen/generate/namespaces.go +++ b/pkg/specgen/generate/namespaces.go @@ -157,6 +157,16 @@ func namespaceOptions(ctx context.Context, s *specgen.SpecGenerator, rt *libpod. case specgen.KeepID: if rootless.IsRootless() { toReturn = append(toReturn, libpod.WithAddCurrentUserPasswdEntry()) + + // If user is not overridden, set user in the container + // to user running Podman. + if s.User == "" { + _, uid, gid, err := util.GetKeepIDMapping() + if err != nil { + return nil, err + } + toReturn = append(toReturn, libpod.WithUser(fmt.Sprintf("%d:%d", uid, gid))) + } } else { // keep-id as root doesn't need a user namespace s.UserNS.NSMode = specgen.Host diff --git a/test/e2e/exec_test.go b/test/e2e/exec_test.go index df86eab15..e6f63a391 100644 --- a/test/e2e/exec_test.go +++ b/test/e2e/exec_test.go @@ -119,6 +119,19 @@ var _ = Describe("Podman exec", func() { Expect(session.ExitCode()).To(Equal(100)) }) + It("podman exec in keep-id container drops privileges", func() { + SkipIfNotRootless("This function is not enabled for rootful podman") + ctrName := "testctr1" + testCtr := podmanTest.Podman([]string{"run", "-d", "--name", ctrName, "--userns=keep-id", ALPINE, "top"}) + testCtr.WaitWithDefaultTimeout() + Expect(testCtr.ExitCode()).To(Equal(0)) + + session := podmanTest.Podman([]string{"exec", ctrName, "grep", "CapEff", "/proc/self/status"}) + session.WaitWithDefaultTimeout() + Expect(session.ExitCode()).To(Equal(0)) + Expect(session.OutputToString()).To(ContainSubstring("0000000000000000")) + }) + It("podman exec --privileged", func() { session := podmanTest.Podman([]string{"run", "--privileged", "--rm", ALPINE, "sh", "-c", "grep ^CapBnd /proc/self/status | cut -f 2"}) session.WaitWithDefaultTimeout() @@ -143,7 +156,6 @@ var _ = Describe("Podman exec", func() { session.WaitWithDefaultTimeout() Expect(session.ExitCode()).To(Equal(0)) Expect(session.OutputToString()).To(ContainSubstring(bndPerms)) - }) It("podman exec --privileged", func() { -- cgit v1.2.3-54-g00ecf