Add support for multi-arch image indexes

The image loaded is based on the platform flag passed to the
structure test binary, which defaults to linux/GOARCH. On hosts that
are multi-platform capable, specifying an different platform flag will
result in an alternate image being loaded from the index.

Fixes #435

Author: jsing-canva

cmd/container-structure-test/app/cmd/test.go

@@ -15,10 +15,12 @@
 package cmd
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
 	"runtime"
+	"strings"
 
 	"github.com/GoogleContainerTools/container-structure-test/cmd/container-structure-test/app/cmd/test"
 	v1 "github.com/opencontainers/image-spec/specs-go/v1"
@@ -32,6 +34,7 @@ import (
 
 	docker "github.com/fsouza/go-dockerclient"
 	"github.com/google/go-containerregistry/pkg/name"
+	gcrv1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/daemon"
 	"github.com/google/go-containerregistry/pkg/v1/layout"
 	"github.com/sirupsen/logrus"
@@ -44,13 +47,60 @@ Be sure you know what you're doing before continuing!
 
 Continue? (y/n)`
 
+const maxSubIndexes = 5
+
 var (
 	opts = &config.StructureTestOptions{}
 
 	args       *drivers.DriverConfig
 	driverImpl func(drivers.DriverConfig) (drivers.Driver, error)
+
+	errNoImageFound = errors.New("no compatible image found")
 )
 
+func parsePlatform(s string) (*gcrv1.Platform, error) {
+	parts := strings.Split(s, "/")
+	if len(parts) != 2 {
+		return nil, fmt.Errorf("invalid platform %q", s)
+	}
+	os, arch := parts[0], parts[1]
+	platform := &gcrv1.Platform{
+		Architecture: arch,
+		OS:           os,
+	}
+	return platform, nil
+}
+
+func findImageInIndex(index gcrv1.ImageIndex, requirements *gcrv1.Platform, depth int) (gcrv1.Image, error) {
+	if depth > maxSubIndexes {
+		return nil, fmt.Errorf("too many subindexes (%d)", maxSubIndexes)
+	}
+
+	manifest, err := index.IndexManifest()
+	if err != nil {
+		return nil, fmt.Errorf("failed to read index manifest: %w", err)
+	}
+
+	for _, desc := range manifest.Manifests {
+		if desc.MediaType.IsImage() && desc.Platform.Satisfies(*requirements) {
+			return index.Image(desc.Digest)
+		}
+		if desc.MediaType.IsIndex() {
+			// Recursively check subindex.
+			childIndex, err := index.ImageIndex(desc.Digest)
+			if err != nil {
+				return nil, err
+			}
+			img, err := findImageInIndex(childIndex, requirements, depth+1)
+			if !errors.Is(err, errNoImageFound) {
+				return img, err
+			}
+		}
+	}
+
+	return nil, errNoImageFound
+}
+
 func NewCmdTest(out io.Writer) *cobra.Command {
 	var testCmd = &cobra.Command{
 		Use:   "test",
@@ -124,14 +174,22 @@ func run(out io.Writer) error {
 
 		desc := m.Manifests[0]
 
+		var img gcrv1.Image
 		if desc.MediaType.IsIndex() {
-			logrus.Fatal("multi-arch images are not supported yet.")
-		}
-
-		img, err := l.Image(desc.Digest)
+			platform, err := parsePlatform(opts.Platform)
+			if err != nil {
+				logrus.Fatalf("%s", err)
+			}
 
-		if err != nil {
-			logrus.Fatalf("could not get image from %s: %v", opts.ImageFromLayout, err)
+			img, err = findImageInIndex(l, platform, 0)
+			if err != nil {
+				logrus.Fatalf("could not get image from %s (platform %v): %v", opts.ImageFromLayout, opts.Platform, err)
+			}
+		} else {
+			img, err = l.Image(desc.Digest)
+			if err != nil {
+				logrus.Fatalf("could not get image from %s: %v", opts.ImageFromLayout, err)
+			}
 		}
 
 		var tag name.Tag

tests/amd64/fluent_bit_test.yaml

@@ -0,0 +1,19 @@
+schemaVersion: '2.0.0' # Make sure to test the latest schema version
+commandTests:
+- name: 'fluent-bit'
+  command: '/fluent-bit/bin/fluent-bit'
+  args: ['--version']
+  expectedOutput: ['Fluent Bit v4.0.4']
+fileContentTests:
+- name: 'Passwd file'
+  expectedContents: ['root:x:0:0:root:/root:/sbin/nologin']
+  path: '/etc/passwd'
+fileExistenceTests:
+- name: 'Root'
+  path: '/'
+  shouldExist: true
+  uid: 0
+  gid: 0
+- name: 'libc'
+  path: '/lib/x86_64-linux-gnu/libc.so.6'
+  shouldExist: true

tests/arm64/fluent_bit_test.yaml

@@ -0,0 +1,19 @@
+schemaVersion: '2.0.0' # Make sure to test the latest schema version
+commandTests:
+- name: 'fluent-bit'
+  command: '/fluent-bit/bin/fluent-bit'
+  args: ['--version']
+  expectedOutput: ['Fluent Bit v4.0.4']
+fileContentTests:
+- name: 'Passwd file'
+  expectedContents: ['root:x:0:0:root:/root:/sbin/nologin']
+  path: '/etc/passwd'
+fileExistenceTests:
+- name: 'Root'
+  path: '/'
+  shouldExist: true
+  uid: 0
+  gid: 0
+- name: 'libc'
+  path: '/lib/aarch64-linux-gnu/libc.so.6'
+  shouldExist: true

tests/structure_test_tests.sh

@@ -246,6 +246,41 @@ else
   echo "PASS: oci success test case"
 fi
 
+HEADER "OCI multi-arch image index test case"
+
+if [[ "$go_architecture" == "amd64" || "$go_architecture" == "arm64" ]]; then
+  test_index="cr.fluentbit.io/fluent/fluent-bit:4.0.4"
+
+  manifest=$(docker manifest inspect "$test_index")
+  if [[ $(echo "$manifest" | jq '.mediaType') != '"application/vnd.docker.distribution.manifest.list.v2+json"' ]]; then
+     echo "FAIL: multi-arch image index test case - $test_index is not an image index"
+     echo "$manifest" | jq '.mediaType'
+     failures=$((failures +1))
+  fi
+  image_count=$(echo "$manifest" | jq '.manifests | length')
+  if [[ $image_count < 2 ]]; then
+     echo "FAIL: multi-arch image index test case - $test_index only has $image_count image(s)"
+     failures=$((failures +1))
+  fi
+
+  tmp="$(mktemp -d)"
+  crane pull "$test_index" --format=oci "$tmp"
+
+  res=$(./out/container-structure-test test --image-from-oci-layout="$tmp" --default-image-tag="test.local/$test_index" --config "${test_config_dir}/fluent_bit_test.yaml" 2>&1)
+  code=$?
+  if ! [[ ("$res" =~ "PASS" && "$code" == "0") ]];
+  then
+    echo "FAIL: oci image index success test case"
+    echo "$res"
+    echo "$code"
+    failures=$((failures +1))
+  else
+    echo "PASS: oci image index test case"
+  fi
+else
+  echo "SKIP: oci image index text case not supported on $go_architecture"
+fi
+
 HEADER "Platform test cases"
 
 docker run --rm --privileged tonistiigi/binfmt --install all > /dev/null