use containerd's epoch package for handling SOURCE_DATE_EPOCH

This allows us to validate the value before we're using it, and makes
sure we handle things in the same way.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

commands/bake.go

@@ -5,8 +5,10 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"strconv"
 
 	"github.com/containerd/console"
+	"github.com/containerd/containerd/pkg/epoch"
 	"github.com/containerd/containerd/platforms"
 	"github.com/docker/buildx/bake"
 	"github.com/docker/buildx/build"
@@ -162,16 +164,18 @@ func runBake(dockerCli command.Cli, targets []string, in bakeOptions, cFlags com
 		return err
 	}
 
-	if v := os.Getenv("SOURCE_DATE_EPOCH"); v != "" {
-		// TODO: extract env var parsing to a method easily usable by library consumers
+	if v, err := epoch.SourceDateEpoch(); err != nil {
+		return err
+	} else if v != nil {
+		esd := strconv.FormatInt(v.Unix(), 10)
 		for _, t := range tgts {
-			if _, ok := t.Args["SOURCE_DATE_EPOCH"]; ok {
+			if _, ok := t.Args[epoch.SourceDateEpochEnv]; ok {
 				continue
 			}
 			if t.Args == nil {
 				t.Args = map[string]*string{}
 			}
-			t.Args["SOURCE_DATE_EPOCH"] = &v
+			t.Args[epoch.SourceDateEpochEnv] = &esd
 		}
 	}
 

commands/build.go

@@ -15,6 +15,7 @@ import (
 	"strings"
 
 	"github.com/containerd/console"
+	"github.com/containerd/containerd/pkg/epoch"
 	"github.com/docker/buildx/build"
 	"github.com/docker/buildx/builder"
 	"github.com/docker/buildx/controller"
@@ -120,10 +121,13 @@ func (o *buildOptions) toControllerOptions() (*controllerapi.BuildOptions, error
 		ExportLoad:     o.exportLoad,
 	}
 
-	// TODO: extract env var parsing to a method easily usable by library consumers
-	if v := os.Getenv("SOURCE_DATE_EPOCH"); v != "" {
-		if _, ok := opts.BuildArgs["SOURCE_DATE_EPOCH"]; !ok {
-			opts.BuildArgs["SOURCE_DATE_EPOCH"] = v
+	if _, ok := opts.BuildArgs[epoch.SourceDateEpochEnv]; !ok {
+		v, err := epoch.SourceDateEpoch()
+		if err != nil {
+			return nil, err
+		}
+		if v != nil {
+			opts.BuildArgs[epoch.SourceDateEpochEnv] = strconv.FormatInt(v.Unix(), 10)
 		}
 	}
 

vendor/github.com/containerd/containerd/pkg/epoch/context.go

@@ -0,0 +1,41 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package epoch
+
+import (
+	"context"
+	"time"
+)
+
+type (
+	epochKey struct{}
+)
+
+// WithSourceDateEpoch associates the context with the epoch.
+func WithSourceDateEpoch(ctx context.Context, tm *time.Time) context.Context {
+	return context.WithValue(ctx, epochKey{}, tm)
+}
+
+// FromContext returns the epoch associated with the context.
+// FromContext does not fall back to read the SOURCE_DATE_EPOCH env var.
+func FromContext(ctx context.Context) *time.Time {
+	v := ctx.Value(epochKey{})
+	if v == nil {
+		return nil
+	}
+	return v.(*time.Time)
+}

vendor/github.com/containerd/containerd/pkg/epoch/epoch.go

@@ -0,0 +1,69 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+// Package epoch provides SOURCE_DATE_EPOCH utilities.
+package epoch
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+// SourceDateEpochEnv is the SOURCE_DATE_EPOCH env var.
+// See https://reproducible-builds.org/docs/source-date-epoch/
+const SourceDateEpochEnv = "SOURCE_DATE_EPOCH"
+
+// SourceDateEpoch returns the SOURCE_DATE_EPOCH env var as *time.Time.
+// If the env var is not set, SourceDateEpoch returns nil without an error.
+func SourceDateEpoch() (*time.Time, error) {
+	v, ok := os.LookupEnv(SourceDateEpochEnv)
+	if !ok || v == "" {
+		return nil, nil // not an error
+	}
+	i64, err := strconv.ParseInt(v, 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("invalid %s value %q: %w", SourceDateEpochEnv, v, err)
+	}
+	unix := time.Unix(i64, 0).UTC()
+	return &unix, nil
+}
+
+// SourceDateEpochOrNow returns the SOURCE_DATE_EPOCH time if available,
+// otherwise returns the current time.
+func SourceDateEpochOrNow() time.Time {
+	epoch, err := SourceDateEpoch()
+	if err != nil {
+		logrus.WithError(err).Warnf("Invalid %s", SourceDateEpochEnv)
+	}
+	if epoch != nil {
+		return *epoch
+	}
+	return time.Now().UTC()
+}
+
+// SetSourceDateEpoch sets the SOURCE_DATE_EPOCH env var.
+func SetSourceDateEpoch(tm time.Time) {
+	os.Setenv(SourceDateEpochEnv, fmt.Sprintf("%d", tm.Unix()))
+}
+
+// UnsetSourceDateEpoch unsets the SOURCE_DATE_EPOCH env var.
+func UnsetSourceDateEpoch() {
+	os.Unsetenv(SourceDateEpochEnv)
+}

vendor/modules.txt

@@ -165,6 +165,7 @@ github.com/containerd/containerd/leases
 github.com/containerd/containerd/log
 github.com/containerd/containerd/namespaces
 github.com/containerd/containerd/pkg/dialer
+github.com/containerd/containerd/pkg/epoch
 github.com/containerd/containerd/pkg/randutil
 github.com/containerd/containerd/pkg/seed
 github.com/containerd/containerd/pkg/userns