Add support for --userns=nomap

From a security point of view, it would be nice to be able to map a
rootless usernamespace that does not use your own UID within the
container.

This would add protection against a hostile process escapping the
container and reading content in your homedir.

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

test/e2e/run_userns_test.go

@@ -78,12 +78,18 @@ var _ = Describe("Podman UserNS support", func() {
 	It("podman --userns=keep-id", func() {
 		session := podmanTest.Podman([]string{"run", "--userns=keep-id", "alpine", "id", "-u"})
 		session.WaitWithDefaultTimeout()
+		if os.Geteuid() == 0 {
+			Expect(session).Should(Exit(125))
+			return
+		}
+
 		Expect(session).Should(Exit(0))
 		uid := fmt.Sprintf("%d", os.Geteuid())
 		Expect(session.OutputToString()).To(ContainSubstring(uid))
 	})
 
 	It("podman --userns=keep-id check passwd", func() {
+		SkipIfNotRootless("keep-id only works in rootless mode")
 		session := podmanTest.Podman([]string{"run", "--userns=keep-id", "alpine", "id", "-un"})
 		session.WaitWithDefaultTimeout()
 		Expect(session).Should(Exit(0))
@@ -93,6 +99,7 @@ var _ = Describe("Podman UserNS support", func() {
 	})
 
 	It("podman --userns=keep-id root owns /usr", func() {
+		SkipIfNotRootless("keep-id only works in rootless mode")
 		session := podmanTest.Podman([]string{"run", "--userns=keep-id", "alpine", "stat", "-c%u", "/usr"})
 		session.WaitWithDefaultTimeout()
 		Expect(session).Should(Exit(0))
@@ -100,6 +107,7 @@ var _ = Describe("Podman UserNS support", func() {
 	})
 
 	It("podman --userns=keep-id --user root:root", func() {
+		SkipIfNotRootless("keep-id only works in rootless mode")
 		session := podmanTest.Podman([]string{"run", "--userns=keep-id", "--user", "root:root", "alpine", "id", "-u"})
 		session.WaitWithDefaultTimeout()
 		Expect(session).Should(Exit(0))
@@ -107,10 +115,7 @@ var _ = Describe("Podman UserNS support", func() {
 	})
 
 	It("podman run --userns=keep-id can add users", func() {
-		if os.Geteuid() == 0 {
-			Skip("Test only runs without root")
-		}
-
+		SkipIfNotRootless("keep-id only works in rootless mode")
 		userName := os.Getenv("USER")
 		if userName == "" {
 			Skip("Can't complete test if no username available")

test/e2e/toolbox_test.go

@@ -160,6 +160,7 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman create --userns=keep-id --user root:root - entrypoint - entrypoint is executed as root", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		session := podmanTest.Podman([]string{"run", "--userns=keep-id", "--user", "root:root", ALPINE,
 			"id"})
 		session.WaitWithDefaultTimeout()
@@ -168,6 +169,7 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman create --userns=keep-id + podman exec - correct names of user and group", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		var session *PodmanSessionIntegration
 		var err error
 
@@ -199,6 +201,7 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman create --userns=keep-id - entrypoint - adding user with useradd and then removing their password", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		var session *PodmanSessionIntegration
 
 		var username string = "testuser"
@@ -238,6 +241,7 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman create --userns=keep-id + podman exec - adding group with groupadd", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		var session *PodmanSessionIntegration
 
 		var groupName string = "testgroup"
@@ -268,6 +272,7 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman create --userns=keep-id - entrypoint - modifying existing user with usermod - add to new group, change home/shell/uid", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		var session *PodmanSessionIntegration
 		var badHomeDir string = "/home/badtestuser"
 		var badShell string = "/bin/sh"
@@ -315,6 +320,7 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman run --privileged --userns=keep-id --user root:root - entrypoint - (bind)mounting", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		var session *PodmanSessionIntegration
 
 		session = podmanTest.Podman([]string{"run", "--privileged", "--userns=keep-id", "--user", "root:root", ALPINE,
@@ -329,6 +335,7 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman create + start - with all needed switches for create - sleep as entry-point", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		var session *PodmanSessionIntegration
 
 		// These should be most of the switches that Toolbox uses to create a "toolbox" container
@@ -365,8 +372,8 @@ var _ = Describe("Toolbox-specific testing", func() {
 	})
 
 	It("podman run --userns=keep-id check $HOME", func() {
+		SkipIfNotRootless("only meaningful when run rootless")
 		var session *PodmanSessionIntegration
-
 		currentUser, err := user.Current()
 		Expect(err).To(BeNil())
 

test/system/030-run.bats

@@ -273,9 +273,11 @@ echo $rand        |   0 | $rand
 # symptom only manifests on a fedora container image -- we have no
 # reproducer on alpine. Checking directory ownership is good enough.
 @test "podman run : user namespace preserved root ownership" {
+    keep="--userns=keep-id"
+    is_rootless || keep=""
     for priv in "" "--privileged"; do
         for user in "--user=0" "--user=100"; do
-            for keepid in "" "--userns=keep-id"; do
+            for keepid in "" ${keep}; do
                 opts="$priv $user $keepid"
 
                 for dir in /etc /usr;do
@@ -290,6 +292,7 @@ echo $rand        |   0 | $rand
 
 # #6829 : add username to /etc/passwd inside container if --userns=keep-id
 @test "podman run : add username to /etc/passwd if --userns=keep-id" {
+    skip_if_not_rootless "--userns=keep-id only works in rootless mode"
     # Default: always run as root
     run_podman run --rm $IMAGE id -un
     is "$output" "root" "id -un on regular container"
@@ -340,6 +343,7 @@ echo $rand        |   0 | $rand
 
 # #6991 : /etc/passwd is modifiable
 @test "podman run : --userns=keep-id: passwd file is modifiable" {
+    skip_if_not_rootless "--userns=keep-id only works in rootless mode"
     run_podman run -d --userns=keep-id --cap-add=dac_override $IMAGE sh -c 'while ! test -e /tmp/stop; do sleep 0.1; done'
     cid="$output"
 
@@ -824,6 +828,9 @@ EOF
 
 # CVE-2022-1227 : podman top joins container mount NS and uses nsenter from image
 @test "podman top does not use nsenter from image" {
+    keepid="--userns=keep-id"
+    is_rootless || keepid=""
+
     tmpdir=$PODMAN_TMPDIR/build-test
     mkdir -p $tmpdir
     tmpbuilddir=$tmpdir/build
@@ -838,7 +845,7 @@ EOF
 
     test_image="cve_2022_1227_test"
     run_podman build -t $test_image $tmpbuilddir
-    run_podman run -d --userns=keep-id $test_image top
+    run_podman run -d ${keepid} $test_image top
     ctr="$output"
     run_podman top $ctr huser,user
     run_podman rm -f -t0 $ctr

test/system/065-cp.bats

@@ -119,7 +119,9 @@ load helpers
     echo "content" > $srcdir/hostfile
     userid=$(id -u)
 
-    run_podman run --user=$userid --userns=keep-id -d --name cpcontainer $IMAGE sleep infinity
+    keepid="--userns=keep-id"
+    is_rootless || keepid=""
+    run_podman run --user=$userid ${keepid} -d --name cpcontainer $IMAGE sleep infinity
     run_podman cp $srcdir/hostfile cpcontainer:/tmp/hostfile
     run_podman exec cpcontainer stat -c "%u" /tmp/hostfile
     is "$output" "$userid" "copied file is chowned to the container user"
@@ -138,7 +140,9 @@ load helpers
 
     userid=$(id -u)
 
-    run_podman run --user="$userid" --userns=keep-id -d --name cpcontainer $IMAGE sleep infinity
+    keepid="--userns=keep-id"
+    is_rootless || keepid=""
+    run_podman run --user=$userid ${keepid} -d --name cpcontainer $IMAGE sleep infinity
     run_podman cp -a=false - cpcontainer:/tmp/ < "${tmpdir}/a.tar"
     run_podman exec cpcontainer stat -c "%u:%g" /tmp/a.txt
     is "$output" "1042:1043" "copied file retains uid/gid from the tar"

test/system/075-exec.bats

@@ -87,6 +87,7 @@ load helpers
 
 # #6829 : add username to /etc/passwd inside container if --userns=keep-id
 @test "podman exec - with keep-id" {
+    skip_if_not_rootless "--userns=keep-id only works in rootless mode"
     # Multiple --userns options confirm command-line override (last one wins)
     run_podman run -d --userns=private --userns=keep-id $IMAGE sh -c \
                "echo READY;while [ ! -f /tmp/stop ]; do sleep 1; done"

test/system/160-volumes.bats

@@ -182,13 +182,14 @@ EOF
 
     run_podman volume rm $myvol
 
-    # Autocreated volumes should also work with keep-id
-    # All we do here is check status; podman 1.9.1 would fail with EPERM
-    myvol=myvol$(random_string)
-    run_podman run --rm -v $myvol:/myvol:z --userns=keep-id $IMAGE \
+    if is_rootless; then
+       # Autocreated volumes should also work with keep-id
+       # All we do here is check status; podman 1.9.1 would fail with EPERM
+       myvol=myvol$(random_string)
+       run_podman run --rm -v $myvol:/myvol:z --userns=keep-id $IMAGE \
                touch /myvol/myfile
-
-    run_podman volume rm $myvol
+       run_podman volume rm $myvol
+    fi
 }
 
 

test/system/170-run-userns.bats

@@ -94,3 +94,17 @@ EOF
     is ${output} ${secret_content} "Secrets should work with user namespace"
     run_podman secret rm ${test_name}
 }
+
+@test "podman userns=nomap" {
+    skip_if_not_rootless "--userns=nomap only works in rootless mode"
+    ns_user=$(id -un)
+    baseuid=$(egrep "${ns_user}:" /etc/subuid | cut -f2 -d:)
+    test ! -z ${baseuid} ||  skip "no IDs allocated for user ${ns_user}"
+
+    test_name="test_$(random_string 12)"
+    run_podman run -d --userns=nomap $IMAGE sleep 100
+    cid=${output}
+    run_podman top ${cid} huser
+    is "${output}" "HUSER.*${baseuid}" "Container should start with baseuid from /etc/subuid not user UID"
+    run_podman rm -t 0 --force ${cid}
+}

test/system/500-networking.bats

@@ -88,6 +88,7 @@ load helpers
 
 # Issue #5466 - port-forwarding doesn't work with this option and -d
 @test "podman networking: port with --userns=keep-id" {
+    skip_if_not_rootless "--userns=keep-id only works in rootless mode"
     for cidr in "" "$(random_rfc1918_subnet).0/24"; do
         myport=$(random_free_port 52000-52999)
         if [[ -z $cidr ]]; then