build: set record provenance in response

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

build/provenance.go

@@ -0,0 +1,157 @@
+package build
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"io"
+	"strings"
+	"sync"
+
+	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/content/proxy"
+	"github.com/docker/buildx/util/confutil"
+	"github.com/docker/buildx/util/progress"
+	controlapi "github.com/moby/buildkit/api/services/control"
+	"github.com/moby/buildkit/client"
+	provenancetypes "github.com/moby/buildkit/solver/llbsolver/provenance/types"
+	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
+	"github.com/pkg/errors"
+	"golang.org/x/sync/errgroup"
+)
+
+type provenancePredicate struct {
+	Builder *provenanceBuilder `json:"builder,omitempty"`
+	provenancetypes.ProvenancePredicate
+}
+
+type provenanceBuilder struct {
+	ID string `json:"id,omitempty"`
+}
+
+func setRecordProvenance(ctx context.Context, c *client.Client, sr *client.SolveResponse, ref string, pw progress.Writer) error {
+	mode := confutil.MetadataProvenance()
+	if mode == confutil.MetadataProvenanceModeDisabled {
+		return nil
+	}
+	pw = progress.ResetTime(pw)
+	return progress.Wrap("resolving provenance for metadata file", pw.Write, func(l progress.SubLogger) error {
+		res, err := fetchProvenance(ctx, c, ref, mode)
+		if err != nil {
+			return err
+		}
+		for k, v := range res {
+			sr.ExporterResponse[k] = v
+		}
+		return nil
+	})
+}
+
+func fetchProvenance(ctx context.Context, c *client.Client, ref string, mode confutil.MetadataProvenanceMode) (out map[string]string, err error) {
+	cl, err := c.ControlClient().ListenBuildHistory(ctx, &controlapi.BuildHistoryRequest{
+		Ref:       ref,
+		EarlyExit: true,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	var mu sync.Mutex
+	eg, ctx := errgroup.WithContext(ctx)
+	store := proxy.NewContentStore(c.ContentClient())
+	for {
+		ev, err := cl.Recv()
+		if errors.Is(err, io.EOF) {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+		if ev.Record == nil {
+			continue
+		}
+		if ev.Record.Result != nil {
+			desc := lookupProvenance(ev.Record.Result)
+			if desc == nil {
+				continue
+			}
+			eg.Go(func() error {
+				dt, err := content.ReadBlob(ctx, store, *desc)
+				if err != nil {
+					return errors.Wrapf(err, "failed to load provenance blob from build record")
+				}
+				prv, err := encodeProvenance(dt, mode)
+				if err != nil {
+					return err
+				}
+				mu.Lock()
+				if out == nil {
+					out = make(map[string]string)
+				}
+				out["buildx.build.provenance"] = prv
+				mu.Unlock()
+				return nil
+			})
+		} else if ev.Record.Results != nil {
+			for platform, res := range ev.Record.Results {
+				platform := platform
+				desc := lookupProvenance(res)
+				if desc == nil {
+					continue
+				}
+				eg.Go(func() error {
+					dt, err := content.ReadBlob(ctx, store, *desc)
+					if err != nil {
+						return errors.Wrapf(err, "failed to load provenance blob from build record")
+					}
+					prv, err := encodeProvenance(dt, mode)
+					if err != nil {
+						return err
+					}
+					mu.Lock()
+					if out == nil {
+						out = make(map[string]string)
+					}
+					out["buildx.build.provenance/"+platform] = prv
+					mu.Unlock()
+					return nil
+				})
+			}
+		}
+	}
+	return out, eg.Wait()
+}
+
+func lookupProvenance(res *controlapi.BuildResultInfo) *ocispecs.Descriptor {
+	for _, a := range res.Attestations {
+		if a.MediaType == "application/vnd.in-toto+json" && strings.HasPrefix(a.Annotations["in-toto.io/predicate-type"], "https://slsa.dev/provenance/") {
+			return &ocispecs.Descriptor{
+				Digest:      a.Digest,
+				Size:        a.Size_,
+				MediaType:   a.MediaType,
+				Annotations: a.Annotations,
+			}
+		}
+	}
+	return nil
+}
+
+func encodeProvenance(dt []byte, mode confutil.MetadataProvenanceMode) (string, error) {
+	var prv provenancePredicate
+	if err := json.Unmarshal(dt, &prv); err != nil {
+		return "", errors.Wrapf(err, "failed to unmarshal provenance")
+	}
+	if prv.Builder != nil && prv.Builder.ID == "" {
+		// reset builder if id is empty
+		prv.Builder = nil
+	}
+	if mode == confutil.MetadataProvenanceModeMin {
+		// reset fields for minimal provenance
+		prv.BuildConfig = nil
+		prv.Metadata = nil
+	}
+	dtprv, err := json.Marshal(prv)
+	if err != nil {
+		return "", errors.Wrapf(err, "failed to marshal provenance")
+	}
+	return base64.StdEncoding.EncodeToString(dtprv), nil
+}