Use PODMAN_USERNS environment variable when running as a service

Fixes: https://github.com/containers/podman/issues/11350#issuecomment-1011562526

Also add inspect information about the idmappings if they exists.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

libpod/container_inspect.go

@@ -9,6 +9,7 @@ import (
 	"github.com/containers/podman/v3/libpod/define"
 	"github.com/containers/podman/v3/libpod/driver"
 	"github.com/containers/podman/v3/pkg/util"
+	"github.com/containers/storage/types"
 	units "github.com/docker/go-units"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/opencontainers/runtime-tools/generate"
@@ -403,6 +404,17 @@ func (c *Container) generateInspectContainerConfig(spec *spec.Spec) *define.Insp
 	return ctrConfig
 }
 
+func generateIDMappings(idMappings types.IDMappingOptions) *define.InspectIDMappings {
+	var inspectMappings define.InspectIDMappings
+	for _, uid := range idMappings.UIDMap {
+		inspectMappings.UIDMap = append(inspectMappings.UIDMap, fmt.Sprintf("%d:%d:%d", uid.ContainerID, uid.HostID, uid.Size))
+	}
+	for _, gid := range idMappings.GIDMap {
+		inspectMappings.GIDMap = append(inspectMappings.GIDMap, fmt.Sprintf("%d:%d:%d", gid.ContainerID, gid.HostID, gid.Size))
+	}
+	return &inspectMappings
+}
+
 // Generate the InspectContainerHostConfig struct for the HostConfig field of
 // Inspect.
 func (c *Container) generateInspectContainerHostConfig(ctrSpec *spec.Spec, namedVolumes []*ContainerNamedVolume, mounts []spec.Mount) (*define.InspectContainerHostConfig, error) {
@@ -815,7 +827,9 @@ func (c *Container) generateInspectContainerHostConfig(ctrSpec *spec.Spec, named
 		}
 	}
 	hostConfig.UsernsMode = usernsMode
-
+	if c.config.IDMappings.UIDMap != nil && c.config.IDMappings.GIDMap != nil {
+		hostConfig.IDMappings = generateIDMappings(c.config.IDMappings)
+	}
 	// Devices
 	// Do not include if privileged - assumed that all devices will be
 	// included.

libpod/define/container_inspect.go

@@ -6,6 +6,11 @@ import (
 	"github.com/containers/image/v5/manifest"
 )
 
+type InspectIDMappings struct {
+	UIDMap []string `json:"UidMap"`
+	GIDMap []string `json:"GidMap"`
+}
+
 // InspectContainerConfig holds further data about how a container was initially
 // configured.
 type InspectContainerConfig struct {
@@ -401,7 +406,10 @@ type InspectContainerHostConfig struct {
 	// TODO Rootless has an additional 'keep-id' option, presently not
 	// reflected here.
 	UsernsMode string `json:"UsernsMode"`
+	// IDMappings is the UIDMapping and GIDMapping used within the container
+	IDMappings *InspectIDMappings `json:"IDMappings,omitempty"`
 	// ShmSize is the size of the container's SHM device.
+
 	ShmSize int64 `json:"ShmSize"`
 	// Runtime is provided purely for Docker compatibility.
 	// It is set unconditionally to "oci" as Podman does not presently

pkg/specgenutil/specgen.go

@@ -205,9 +205,13 @@ func setNamespaces(s *specgen.SpecGenerator, c *entities.ContainerCreateOptions)
 			return err
 		}
 	}
-	// userns must be treated differently
+	userns := os.Getenv("PODMAN_USERNS")
 	if c.UserNS != "" {
-		s.UserNS, err = specgen.ParseUserNamespace(c.UserNS)
+		userns = c.UserNS
+	}
+	// userns must be treated differently
+	if userns != "" {
+		s.UserNS, err = specgen.ParseUserNamespace(userns)
 		if err != nil {
 			return err
 		}

test/e2e/run_userns_test.go

@@ -301,5 +301,34 @@ var _ = Describe("Podman UserNS support", func() {
 			Expect(inspectGID).Should(Exit(0))
 			Expect(inspectGID.OutputToString()).To(Equal(tt.gid))
 		}
+
+	})
+	It("podman PODMAN_USERNS", func() {
+		SkipIfNotRootless("keep-id only works in rootless mode")
+
+		podmanUserns, podmanUserusSet := os.LookupEnv("PODMAN_USERNS")
+		os.Setenv("PODMAN_USERNS", "keep-id")
+		defer func() {
+			if podmanUserusSet {
+				os.Setenv("PODMAN_USERNS", podmanUserns)
+			} else {
+				os.Unsetenv("PODMAN_USERNS")
+			}
+		}()
+		if IsRemote() {
+			podmanTest.RestartRemoteService()
+		}
+
+		result := podmanTest.Podman([]string{"create", ALPINE, "true"})
+		result.WaitWithDefaultTimeout()
+		Expect(result).Should(Exit(0))
+
+		inspect := podmanTest.Podman([]string{"inspect", "--format", "{{ .HostConfig.IDMappings }}", result.OutputToString()})
+		inspect.WaitWithDefaultTimeout()
+		Expect(inspect.OutputToString()).To(Not(Equal("<nil>")))
+
+		if IsRemote() {
+			podmanTest.RestartRemoteService()
+		}
 	})
 })