Add U volume flag to chown source volumes

Signed-off-by: Eduardo Vega <[email protected]>

docs/buildah-bud.md

@@ -581,6 +581,7 @@ process.
    container. The `OPTIONS` are a comma delimited list and can be: <sup>[[1]](#Footnote1)</sup>
 
    * [rw|ro]
+   * [U]
    * [z|Z|O]
    * [`[r]shared`|`[r]slave`|`[r]private`]
 
@@ -593,10 +594,18 @@ and bind mounts that into the container.
 You can specify multiple  **-v** options to mount one or more mounts to a
 container.
 
+  `Write Protected Volume Mounts`
+
 You can add the `:ro` or `:rw` suffix to a volume to mount it read-only or
 read-write mode, respectively. By default, the volumes are mounted read-write.
 See examples.
 
+  `Chowning Volume Mounts`
+
+By default, Buildah does not change the owner and group of source volume directories mounted into containers. If a container is created in a new user namespace, the UID and GID in the container may correspond to another UID and GID on the host.
+
+The `:U` suffix tells Buildah to use the correct host UID and GID based on the UID and GID within the container, to change the owner and group of the source volume.
+
   `Labeling Volume Mounts`
 
 Labeling systems like SELinux require that proper labels are placed on volume
@@ -622,7 +631,7 @@ Only the current container can use a private volume.
 
   Note:
 
-     - The `O` flag is not allowed to be specified with the `Z` or `z` flags. Content mounted into the container is labeled with the private label.
+     - The `O` flag is not allowed to be specified with the `Z`, `z` or `U` flags. Content mounted into the container is labeled with the private label.
        On SELinux systems, labels in the source directory needs to be readable by the container label. If not, SELinux container separation must be disabled for the container to work.
      - Modification of the directory volume mounted into the container with an overlay mount can cause unexpected failures.  It is recommended that you do not modify the directory until the container finishes running.
 
@@ -689,6 +698,8 @@ buildah bud --security-opt label=level:s0:c100,c200 --cgroup-parent /path/to/cgr
 
 buildah bud --volume /home/test:/myvol:ro,Z -t imageName .
 
+buildah bud -v /home/test:/myvol:z,U -t imageName .
+
 buildah bud -v /var/lib/dnf:/var/lib/dnf:O -t imageName .
 
 buildah bud --layers -t imageName .

docs/buildah-from.md

@@ -449,6 +449,7 @@ process.
    container. The `OPTIONS` are a comma delimited list and can be: <sup>[[1]](#Footnote1)</sup>
 
    * [rw|ro]
+   * [U]
    * [z|Z|O]
    * [`[r]shared`|`[r]slave`|`[r]private`|`[r]unbindable`]
 
@@ -461,10 +462,18 @@ and bind mounts that into the container.
 You can specify multiple  **-v** options to mount one or more mounts to a
 container.
 
+  `Write Protected Volume Mounts`
+
 You can add the `:ro` or `:rw` suffix to a volume to mount it read-only or
 read-write mode, respectively. By default, the volumes are mounted read-write.
 See examples.
 
+  `Chowning Volume Mounts`
+
+By default, Buildah does not change the owner and group of source volume directories mounted into containers. If a container is created in a new user namespace, the UID and GID in the container may correspond to another UID and GID on the host.
+
+The `:U` suffix tells Buildah to use the correct host UID and GID based on the UID and GID within the container, to change the owner and group of the source volume.
+
   `Labeling Volume Mounts`
 
 Labeling systems like SELinux require that proper labels are placed on volume
@@ -490,7 +499,7 @@ Only the current container can use a private volume.
 
   Note:
 
-     - The `O` flag is not allowed to be specified with the `Z` or `z` flags. Content mounted into the container is labeled with the private label.
+     - The `O` flag is not allowed to be specified with the `Z`, `z` or `U` flags. Content mounted into the container is labeled with the private label.
        On SELinux systems, labels in the source directory needs to be readable by the container label. If not, SELinux container separation must be disabled for the container to work.
      - Modification of the directory volume mounted into the container with an overlay mount can cause unexpected failures.  It is recommended that you do not modify the directory until the container finishes running.
 
@@ -553,6 +562,8 @@ buildah from --ulimit nofile=1024:1028 --cgroup-parent /path/to/cgroup/parent my
 
 buildah from --volume /home/test:/myvol:ro,Z myregistry/myrepository/imagename:imagetag
 
+buildah from -v /home/test:/myvol:z,U myregistry/myrepository/imagename:imagetag
+
 buildah from -v /var/lib/yum:/var/lib/yum:O myregistry/myrepository/imagename:imagetag
 
 ## ENVIRONMENT

docs/buildah-run.md

@@ -188,6 +188,7 @@ bind mounts `/HOST-DIR` in the host to `/CONTAINER-DIR` in the Buildah
 container. The `OPTIONS` are a comma delimited list and can be: <sup>[[1]](#Footnote1)</sup>
 
    * [rw|ro]
+   * [U]
    * [z|Z]
    * [`[r]shared`|`[r]slave`|`[r]private`]
 
@@ -200,10 +201,20 @@ and bind mounts that into the container.
 You can specify multiple  **-v** options to mount one or more mounts to a
 container.
 
+  `Write Protected Volume Mounts`
+
 You can add the `:ro` or `:rw` suffix to a volume to mount it read-only or
 read-write mode, respectively. By default, the volumes are mounted read-write.
 See examples.
 
+  `Chowning Volume Mounts`
+
+By default, Buildah does not change the owner and group of source volume directories mounted into containers. If a container is created in a new user namespace, the UID and GID in the container may correspond to another UID and GID on the host.
+
+The `:U` suffix tells Buildah to use the correct host UID and GID based on the UID and GID within the container, to change the owner and group of the source volume.
+
+  `Labeling Volume Mounts`
+
 Labeling systems like SELinux require that proper labels are placed on volume
 content mounted into a container. Without a label, the security system might
 prevent the processes running inside the container from using the content. By
@@ -270,6 +281,8 @@ buildah run --tty=false containerID ls /
 
 buildah run --volume /path/on/host:/path/in/container:ro,z containerID sh
 
+buildah run -v /path/on/host:/path/in/container:z,U containerID sh
+
 buildah run --mount type=bind,src=/tmp/on:host,dst=/in:container,ro containerID sh
 
 ## SEE ALSO

pkg/parse/parse.go

@@ -486,7 +486,7 @@ func ValidateVolumeCtrDir(ctrDir string) error {
 
 // ValidateVolumeOpts validates a volume's options
 func ValidateVolumeOpts(options []string) ([]string, error) {
-	var foundRootPropagation, foundRWRO, foundLabelChange, bindType, foundExec, foundDev, foundSuid int
+	var foundRootPropagation, foundRWRO, foundLabelChange, bindType, foundExec, foundDev, foundSuid, foundChown int
 	finalOpts := make([]string, 0, len(options))
 	for _, opt := range options {
 		switch opt {
@@ -515,6 +515,11 @@ func ValidateVolumeOpts(options []string) ([]string, error) {
 			if foundLabelChange > 1 {
 				return nil, errors.Errorf("invalid options %q, can only specify 1 'z', 'Z', or 'O' option", strings.Join(options, ", "))
 			}
+		case "U":
+			foundChown++
+			if foundChown > 1 {
+				return nil, errors.Errorf("invalid options %q, can only specify 1 'U' option", strings.Join(options, ", "))
+			}
 		case "private", "rprivate", "shared", "rshared", "slave", "rslave", "unbindable", "runbindable":
 			foundRootPropagation++
 			if foundRootPropagation > 1 {

run_linux.go

@@ -506,8 +506,14 @@ func (b *Builder) setupMounts(mountPoint string, spec *specs.Spec, bundlePath st
 		return err
 	}
 
+	// Get host UID and GID of the container process.
+	processUID, processGID, err := util.GetHostIDs(spec.Linux.UIDMappings, spec.Linux.GIDMappings, spec.Process.User.UID, spec.Process.User.GID)
+	if err != nil {
+		return err
+	}
+
 	// Get the list of explicitly-specified volume mounts.
-	volumes, err := b.runSetupVolumeMounts(spec.Linux.MountLabel, volumeMounts, optionMounts, int(rootUID), int(rootGID))
+	volumes, err := b.runSetupVolumeMounts(spec.Linux.MountLabel, volumeMounts, optionMounts, int(rootUID), int(rootGID), int(processUID), int(processGID))
 	if err != nil {
 		return err
 	}
@@ -1687,7 +1693,7 @@ func (b *Builder) cleanupTempVolumes() {
 	}
 }
 
-func (b *Builder) runSetupVolumeMounts(mountLabel string, volumeMounts []string, optionMounts []specs.Mount, rootUID, rootGID int) (mounts []specs.Mount, Err error) {
+func (b *Builder) runSetupVolumeMounts(mountLabel string, volumeMounts []string, optionMounts []specs.Mount, rootUID, rootGID, processUID, processGID int) (mounts []specs.Mount, Err error) {
 
 	// Make sure the overlay directory is clean before running
 	containerDir, err := b.store.ContainerDirectory(b.ContainerID)
@@ -1699,7 +1705,7 @@ func (b *Builder) runSetupVolumeMounts(mountLabel string, volumeMounts []string,
 	}
 
 	parseMount := func(mountType, host, container string, options []string) (specs.Mount, error) {
-		var foundrw, foundro, foundz, foundZ, foundO bool
+		var foundrw, foundro, foundz, foundZ, foundO, foundU bool
 		var rootProp string
 		for _, opt := range options {
 			switch opt {
@@ -1713,6 +1719,8 @@ func (b *Builder) runSetupVolumeMounts(mountLabel string, volumeMounts []string,
 				foundZ = true
 			case "O":
 				foundO = true
+			case "U":
+				foundU = true
 			case "private", "rprivate", "slave", "rslave", "shared", "rshared":
 				rootProp = opt
 			}
@@ -1748,6 +1756,11 @@ func (b *Builder) runSetupVolumeMounts(mountLabel string, volumeMounts []string,
 			}
 			return overlayMount, err
 		}
+		if foundU {
+			if err := chownSourceVolume(host, processUID, processGID); err != nil {
+				return specs.Mount{}, err
+			}
+		}
 		if rootProp == "" {
 			options = append(options, "private")
 		}
@@ -1789,6 +1802,27 @@ func (b *Builder) runSetupVolumeMounts(mountLabel string, volumeMounts []string,
 	return mounts, nil
 }
 
+// chownSourceVolume changes the ownership of a volume source directory or file within the host.
+func chownSourceVolume(path string, UID, GID int) error {
+	fi, err := os.Lstat(path)
+	if err != nil {
+		return err
+	}
+
+	currentUID := int(fi.Sys().(*syscall.Stat_t).Uid)
+	currentGID := int(fi.Sys().(*syscall.Stat_t).Gid)
+
+	if UID != currentUID && GID != currentGID {
+		if err := filepath.Walk(path, func(filePath string, f os.FileInfo, err error) error {
+			return os.Lchown(filePath, UID, GID)
+		}); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func setupMaskedPaths(g *generate.Generator) {
 	for _, mp := range []string{
 		"/proc/acpi",

tests/from.bats

@@ -238,6 +238,38 @@ load helpers
   expect_output --substring " /myvol "
 }
 
+@test "from --volume with U flag" {
+  skip_if_no_runtime
+
+  # Check if we're running in an environment that can even test this.
+  run readlink /proc/self/ns/user
+  echo "readlink /proc/self/ns/user -> $output"
+  [ $status -eq 0 ] || skip "user namespaces not supported"
+
+  # Generate the mappings to use for using a user namespace.
+  uidbase=$((${RANDOM}+1024))
+  gidbase=$((${RANDOM}+1024))
+  uidsize=$((${RANDOM}+1024))
+  gidsize=$((${RANDOM}+1024))
+
+  # Create source volume.
+  mkdir ${TESTDIR}/testdata
+  touch ${TESTDIR}/testdata/testfile1.txt
+
+  # Create a container that uses that mapping and U volume flag.
+  _prefetch alpine
+  run_buildah from --signature-policy ${TESTSDIR}/policy.json --userns-uid-map 0:$uidbase:$uidsize --userns-gid-map 0:$gidbase:$gidsize --volume ${TESTDIR}/testdata:/mnt:z,U alpine
+  ctr="$output"
+
+  run_buildah run "$ctr" stat -c "%u:%g" /mnt/testfile1.txt
+  expect_output "0:0"
+
+  run_buildah run "$ctr" touch /mnt/testfile2.txt
+
+  run_buildah run "$ctr" stat -c "%u:%g" /mnt/testfile2.txt
+  expect_output "0:0"
+}
+
 @test "from shm-size test" {
   skip_if_chroot
   skip_if_no_runtime

tests/run.bats

@@ -252,6 +252,25 @@ function configure_and_check_user() {
 	run_buildah run -v ${TESTDIR}/was-empty/testfile:/var/different-multi-level/subdirectory/testfile        $cid touch /var/different-multi-level/subdirectory/testfile
 }
 
+@test "run --volume with U flag" {
+  skip_if_no_runtime
+
+  # Create source volume.
+  mkdir ${TESTDIR}/testdata
+
+  # Create the container.
+  _prefetch alpine
+  run_buildah from --signature-policy ${TESTSDIR}/policy.json alpine
+  ctr="$output"
+
+  # Test user can create file in the mounted volume.
+  run_buildah run --user 888:888 --volume ${TESTDIR}/testdata:/mnt:z,U "$ctr" touch /mnt/testfile1.txt
+
+  # Test user owns the file within the mounted volume.
+  run_buildah run --user 888:888 --volume ${TESTDIR}/testdata:/mnt:z,U "$ctr" stat -c "%u:%g" /mnt/testfile1.txt
+  expect_output "888:888"
+}
+
 @test "run --mount" {
 	skip_if_no_runtime