llb: avoid duplicate instances of sourcemaps in provenance

If build contains multiple subbuilds all of their sources
are tracked in provenance attestations. When some subbuilds
are coming from same source file (eg. same Dockerfile but
different targets) currently the same file would appear
in multiple times. This detects such duplicates and makes
sure definitions from multiple subbuilds can map to same file.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

client/llb/sourcemap.go

@@ -1,6 +1,7 @@
 package llb
 
 import (
+	"bytes"
 	"context"
 
 	"github.com/moby/buildkit/solver/pb"
@@ -47,6 +48,33 @@ func (s *SourceMap) Location(r []*pb.Range) ConstraintsOpt {
 	})
 }
 
+func equalSourceMap(sm1, sm2 *SourceMap) (out bool) {
+	if sm1 == nil || sm2 == nil {
+		return false
+	}
+	if sm1.Filename != sm2.Filename {
+		return false
+	}
+	if sm1.Language != sm2.Language {
+		return false
+	}
+	if len(sm1.Data) != len(sm2.Data) {
+		return false
+	}
+	if !bytes.Equal(sm1.Data, sm2.Data) {
+		return false
+	}
+	if sm1.Definition != nil && sm2.Definition != nil {
+		if len(sm1.Definition.Def) != len(sm2.Definition.Def) && len(sm1.Definition.Def) != 0 {
+			return false
+		}
+		if !bytes.Equal(sm1.Definition.Def[len(sm1.Definition.Def)-1], sm2.Definition.Def[len(sm2.Definition.Def)-1]) {
+			return false
+		}
+	}
+	return true
+}
+
 type SourceLocation struct {
 	SourceMap *SourceMap
 	Ranges    []*pb.Range
@@ -69,8 +97,18 @@ func (smc *sourceMapCollector) Add(dgst digest.Digest, ls []*SourceLocation) {
 	for _, l := range ls {
 		idx, ok := smc.index[l.SourceMap]
 		if !ok {
-			idx = len(smc.maps)
-			smc.maps = append(smc.maps, l.SourceMap)
+			idx = -1
+			// slow equality check
+			for i, m := range smc.maps {
+				if equalSourceMap(m, l.SourceMap) {
+					idx = i
+					break
+				}
+			}
+			if idx == -1 {
+				idx = len(smc.maps)
+				smc.maps = append(smc.maps, l.SourceMap)
+			}
 		}
 		smc.index[l.SourceMap] = idx
 	}

frontend/dockerfile/dockerfile_provenance_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -16,16 +17,20 @@ import (
 
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/content/local"
+	"github.com/containerd/containerd/content/proxy"
 	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/continuity/fs/fstest"
 	intoto "github.com/in-toto/in-toto-golang/in_toto"
 	provenanceCommon "github.com/in-toto/in-toto-golang/in_toto/slsa_provenance/common"
+	controlapi "github.com/moby/buildkit/api/services/control"
 	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/client/llb"
 	"github.com/moby/buildkit/exporter/containerimage/exptypes"
 	"github.com/moby/buildkit/frontend/dockerui"
 	gateway "github.com/moby/buildkit/frontend/gateway/client"
+	"github.com/moby/buildkit/identity"
 	"github.com/moby/buildkit/solver/llbsolver/provenance"
+	"github.com/moby/buildkit/solver/pb"
 	"github.com/moby/buildkit/util/contentutil"
 	"github.com/moby/buildkit/util/testutil"
 	"github.com/moby/buildkit/util/testutil/integration"
@@ -1113,3 +1118,153 @@ func testDockerIgnoreMissingProvenance(t *testing.T, sb integration.Sandbox) {
 	}, "", frontend, nil)
 	require.NoError(t, err)
 }
+
+func testFrontendDeduplicateSources(t *testing.T, sb integration.Sandbox) {
+	ctx := sb.Context()
+
+	c, err := client.New(ctx, sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	dockerfile := []byte(`
+FROM scratch as base
+COPY foo foo2
+
+FROM linked
+COPY bar bar2
+`)
+
+	dir := integration.Tmpdir(
+		t,
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+		fstest.CreateFile("foo", []byte("data"), 0600),
+		fstest.CreateFile("bar", []byte("data2"), 0600),
+	)
+
+	f := getFrontend(t, sb)
+
+	b := func(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
+		res, err := f.SolveGateway(ctx, c, gateway.SolveRequest{
+			FrontendOpt: map[string]string{
+				"target": "base",
+			},
+		})
+		if err != nil {
+			return nil, err
+		}
+		ref, err := res.SingleRef()
+		if err != nil {
+			return nil, err
+		}
+		st, err := ref.ToState()
+		if err != nil {
+			return nil, err
+		}
+
+		def, err := st.Marshal(ctx)
+		if err != nil {
+			return nil, err
+		}
+
+		dt, ok := res.Metadata["containerimage.config"]
+		if !ok {
+			return nil, errors.Errorf("no containerimage.config in metadata")
+		}
+
+		dt, err = json.Marshal(map[string][]byte{
+			"containerimage.config": dt,
+		})
+		if err != nil {
+			return nil, err
+		}
+
+		res, err = f.SolveGateway(ctx, c, gateway.SolveRequest{
+			FrontendOpt: map[string]string{
+				"context:linked":        "input:baseinput",
+				"input-metadata:linked": string(dt),
+			},
+			FrontendInputs: map[string]*pb.Definition{
+				"baseinput": def.ToPB(),
+			},
+		})
+		if err != nil {
+			return nil, err
+		}
+		return res, nil
+	}
+
+	product := "buildkit_test"
+
+	destDir := t.TempDir()
+
+	ref := identity.NewID()
+
+	_, err = c.Build(ctx, client.SolveOpt{
+		LocalDirs: map[string]string{
+			dockerui.DefaultLocalNameDockerfile: dir,
+			dockerui.DefaultLocalNameContext:    dir,
+		},
+		Exports: []client.ExportEntry{
+			{
+				Type:      client.ExporterLocal,
+				OutputDir: destDir,
+			},
+		},
+		Ref: ref,
+	}, product, b, nil)
+	require.NoError(t, err)
+
+	dt, err := os.ReadFile(filepath.Join(destDir, "foo2"))
+	require.NoError(t, err)
+	require.Equal(t, "data", string(dt))
+
+	dt, err = os.ReadFile(filepath.Join(destDir, "bar2"))
+	require.NoError(t, err)
+	require.Equal(t, "data2", string(dt))
+
+	history, err := c.ControlClient().ListenBuildHistory(ctx, &controlapi.BuildHistoryRequest{
+		Ref:       ref,
+		EarlyExit: true,
+	})
+	require.NoError(t, err)
+
+	store := proxy.NewContentStore(c.ContentClient())
+
+	var provDt []byte
+	for {
+		ev, err := history.Recv()
+		if err != nil {
+			require.Equal(t, io.EOF, err)
+			break
+		}
+		require.Equal(t, ref, ev.Record.Ref)
+
+		for _, prov := range ev.Record.Result.Attestations {
+			if len(prov.Annotations) == 0 || prov.Annotations["in-toto.io/predicate-type"] != "https://slsa.dev/provenance/v0.2" {
+				t.Logf("skipping non-slsa provenance: %s", prov.MediaType)
+				continue
+			}
+
+			provDt, err = content.ReadBlob(ctx, store, ocispecs.Descriptor{
+				MediaType: prov.MediaType,
+				Digest:    prov.Digest,
+				Size:      prov.Size_,
+			})
+			require.NoError(t, err)
+		}
+	}
+
+	require.NotEqual(t, len(provDt), 0)
+
+	var pred provenance.ProvenancePredicate
+	require.NoError(t, json.Unmarshal(provDt, &pred))
+
+	sources := pred.Metadata.BuildKitMetadata.Source.Infos
+
+	require.Equal(t, 1, len(sources))
+	require.Equal(t, "Dockerfile", sources[0].Filename)
+	require.Equal(t, "Dockerfile", sources[0].Language)
+
+	require.Equal(t, dockerfile, sources[0].Data)
+	require.NotEqual(t, 0, len(sources[0].Definition))
+}

frontend/dockerfile/dockerfile_test.go

@@ -170,6 +170,7 @@ var allTests = integration.TestFuncs(
 	testMultiPlatformWarnings,
 	testNilContextInSolveGateway,
 	testCopyUnicodePath,
+	testFrontendDeduplicateSources,
 )
 
 // Tests that depend on the `security.*` entitlements