Add containerenv information to /run/.containerenv

We have been asked to leak some information into the container
to indicate:
* The name and id of the container
* The version of podman used to launch the container
* The image name and ID the container is based on.
* Whether the container engine is running in rootless mode.

Fixes: https://github.com/containers/podman/issues/6192

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

3 files changed, 50 insertions, 7 deletions

diff --git a/docs/source/markdown/podman-run.1.md b/docs/source/markdown/podman-run.1.md
index 1038906c0..53c5b2d4b 100644
--- a/docs/source/markdown/podman-run.1.md
+++ b/docs/source/markdown/podman-run.1.md
@@ -26,9 +26,12 @@ Several files will be automatically created within the container. These include
 _/etc/hosts_, _/etc/hostname_, and _/etc/resolv.conf_ to manage networking.
 These will be based on the host's version of the files, though they can be
 customized with options (for example, **--dns** will override the host's DNS
-servers in the created _resolv.conf_). Additionally, an empty file is created in
-each container to indicate to programs they are running in a container. This file
-is located at _/run/.containerenv_.
+servers in the created _resolv.conf_). Additionally, a container environment
+file is created in each container to indicate to programs they are running in a
+container. This file is located at _/run/.containerenv_. When using the
+--privileged flag the .containerenv contains name/value pairs indicating the
+container engine version, whether the engine is running in rootless mode, the
+container name and id, as well as the image name and id that the container is based on.
 
 When running from a user defined network namespace, the _/etc/netns/NSNAME/resolv.conf_
 will be used if it exists, otherwise _/etc/resolv.conf_ will be used.
diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 56575c195..fb30192f1 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -35,6 +35,7 @@ import (
 	"github.com/containers/podman/v2/pkg/rootless"
 	"github.com/containers/podman/v2/pkg/util"
 	"github.com/containers/podman/v2/utils"
+	"github.com/containers/podman/v2/version"
 	"github.com/containers/storage/pkg/archive"
 	"github.com/containers/storage/pkg/idtools"
 	securejoin "github.com/cyphar/filepath-securejoin"
@@ -1423,11 +1424,26 @@ func (c *Container) makeBindMounts() error {
 		}
 	}
 
-	// Make .containerenv
-	// Empty file, so no need to recreate if it exists
+	// Make .containerenv if it does not exist
 	if _, ok := c.state.BindMounts["/run/.containerenv"]; !ok {
-		// Empty string for now, but we may consider populating this later
-		containerenvPath, err := c.writeStringToRundir(".containerenv", "")
+		var containerenv string
+		isRootless := 0
+		if rootless.IsRootless() {
+			isRootless = 1
+		}
+		imageID, imageName := c.Image()
+
+		if c.Privileged() {
+			// Populate the .containerenv with container information
+			containerenv = fmt.Sprintf(`engine="podman-%s"
+name=%q
+id=%q
+image=%q
+imageid=%q
+rootless=%d
+`, version.Version.String(), c.Name(), c.ID(), imageName, imageID, isRootless)
+		}
+		containerenvPath, err := c.writeStringToRundir(".containerenv", containerenv)
 		if err != nil {
 			return errors.Wrapf(err, "error creating containerenv file for container %s", c.ID())
 		}
diff --git a/test/system/030-run.bats b/test/system/030-run.bats
index 37695f205..6db6b76f1 100644
--- a/test/system/030-run.bats
+++ b/test/system/030-run.bats
@@ -536,6 +536,30 @@ json-file | f
     run_podman untag $IMAGE $newtag $newtag2
 }
 
+@test "Verify /run/.containerenv exist" {
+	run_podman run --rm $IMAGE ls -1 /run/.containerenv
+	is "$output" "/run/.containerenv"
+
+	run_podman run --privileged --rm $IMAGE sh -c '. /run/.containerenv; echo $engine'
+	is "$output" ".*podman.*" "failed to identify engine"
+
+	run_podman run --privileged  --name "testcontainerenv" --rm $IMAGE sh -c '. /run/.containerenv; echo $name'
+	is "$output" ".*testcontainerenv.*"
+
+	run_podman run --privileged  --rm $IMAGE sh -c '. /run/.containerenv; echo $image'
+	is "$output" ".*$IMAGE.*" "failed to idenitfy image"
+
+	run_podman run --privileged --rm $IMAGE sh -c '. /run/.containerenv; echo $rootless'
+	# FIXME: on some CI systems, 'run --privileged' emits a spurious
+	# warning line about dup devices. Ignore it.
+	remove_same_dev_warning
+	if is_rootless; then
+		is "$output" "1"
+	else
+		is "$output" "0"
+	fi
+}
+
 @test "podman run with --net=host and --port prints warning" {
     rand=$(random_string 10)