Extract melange sign to a library

pkg/cli/sign.go

@@ -22,14 +22,12 @@ import (
 	"io"
 	"os"
 
+	pkgsign "chainguard.dev/melange/pkg/sign"
 	"github.com/chainguard-dev/clog"
-	"github.com/chainguard-dev/go-apk/pkg/expandapk"
 	sign "github.com/chainguard-dev/go-apk/pkg/signature"
 	"github.com/klauspost/compress/gzip"
 	"github.com/spf13/cobra"
 	"golang.org/x/sync/errgroup"
-
-	"chainguard.dev/melange/pkg/build"
 )
 
 type signIndexOpts struct {
@@ -193,70 +191,5 @@ func (o signOpts) RunAllE(ctx context.Context, pkgs ...string) error {
 
 func (o signOpts) run(ctx context.Context, pkg string) error {
 	clog.FromContext(ctx).Infof("Processing apk %s", pkg)
-
-	apkr, err := os.Open(pkg)
-	if err != nil {
-		return err
-	}
-
-	eapk, err := expandapk.ExpandApk(ctx, apkr, "")
-	if err != nil {
-		return fmt.Errorf("expanding apk: %w", err)
-	}
-	defer eapk.Close()
-
-	if err := apkr.Close(); err != nil {
-		return err
-	}
-
-	// Split the streams and then rebuild
-	cf, err := os.Open(eapk.ControlFile)
-	if err != nil {
-		return err
-	}
-	defer cf.Close()
-
-	// Use the control sections ModTime (set to SDE) for the signature
-	cfinfo, err := os.Stat(eapk.ControlFile)
-	if err != nil {
-		return err
-	}
-
-	pc := &build.PackageBuild{
-		Build: &build.Build{
-			SigningKey:        o.Key,
-			SigningPassphrase: "",
-		},
-	}
-
-	cdata, err := os.ReadFile(eapk.ControlFile)
-	if err != nil {
-		return err
-	}
-
-	sigData, err := build.EmitSignature(ctx, pc.Signer(), cdata, cfinfo.ModTime())
-	if err != nil {
-		return err
-	}
-
-	df, err := os.Open(eapk.PackageFile)
-	if err != nil {
-		return err
-	}
-	defer df.Close()
-
-	// Replace the package file with the new one
-	f, err := os.Create(pkg)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
-	for _, fp := range []io.Reader{bytes.NewBuffer(sigData), cf, df} {
-		if _, err := io.Copy(f, fp); err != nil {
-			return err
-		}
-	}
-
-	return nil
+	return pkgsign.APK(ctx, pkg, o.Key)
 }

pkg/sign/apk.go

@@ -0,0 +1,95 @@
+// Copyright 2024 Chainguard, Inc.
+//
+// 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 sign
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"os"
+
+	"chainguard.dev/melange/pkg/build"
+	"github.com/chainguard-dev/go-apk/pkg/expandapk"
+)
+
+// APK() signs an APK file with the provided key. The existing APK file is
+// replaced with the signed APK file.
+func APK(ctx context.Context, apkPath string, keyPath string) error {
+	apkr, err := os.Open(apkPath)
+	if err != nil {
+		return err
+	}
+
+	eapk, err := expandapk.ExpandApk(ctx, apkr, "")
+	if err != nil {
+		return fmt.Errorf("expanding apk: %w", err)
+	}
+	defer eapk.Close()
+
+	if err := apkr.Close(); err != nil {
+		return err
+	}
+
+	// Split the streams and then rebuild
+	cf, err := os.Open(eapk.ControlFile)
+	if err != nil {
+		return err
+	}
+	defer cf.Close()
+
+	// Use the control sections ModTime (set to SDE) for the signature
+	cfinfo, err := os.Stat(eapk.ControlFile)
+	if err != nil {
+		return err
+	}
+
+	pc := &build.PackageBuild{
+		Build: &build.Build{
+			SigningKey:        keyPath,
+			SigningPassphrase: "",
+		},
+	}
+
+	cdata, err := os.ReadFile(eapk.ControlFile)
+	if err != nil {
+		return err
+	}
+
+	sigData, err := build.EmitSignature(ctx, pc.Signer(), cdata, cfinfo.ModTime())
+	if err != nil {
+		return err
+	}
+
+	df, err := os.Open(eapk.PackageFile)
+	if err != nil {
+		return err
+	}
+	defer df.Close()
+
+	// Replace the package file with the new one
+	f, err := os.Create(apkPath)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	for _, fp := range []io.Reader{bytes.NewBuffer(sigData), cf, df} {
+		if _, err := io.Copy(f, fp); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

pkg/sign/apk_test.go

@@ -0,0 +1,120 @@
+// Copyright 2024 Chainguard, Inc.
+//
+// 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 sign
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"context"
+	"crypto/sha1"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/chainguard-dev/go-apk/pkg/expandapk"
+	"github.com/chainguard-dev/go-apk/pkg/signature"
+)
+
+const (
+	testAPK     = "testdata/test.apk"
+	testPubkey  = "test.pem.pub"
+	testPrivKey = "test.pem"
+)
+
+func TestAPK(t *testing.T) {
+	tmpDir := t.TempDir()
+	ctx := context.Background()
+	apkPath := tmpDir + "/out.apk"
+
+	// copy testdata/test.apk to tmpDir
+	if err := CopyFile(testAPK, apkPath); err != nil {
+		t.Fatal(err)
+	}
+	// sign the apk
+	if err := APK(ctx, apkPath, "testdata/"+testPrivKey); err != nil {
+		t.Fatal(err)
+	}
+	// verify the signature
+	controlData, sigName, sig, err := parseAPK(ctx, apkPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if sigName != ".SIGN.RSA."+testPubkey {
+		t.Fatalf("unexpected signature name %s", sigName)
+	}
+	//nolint:gosec we do have to use SHA1 here
+	digest := computeSHA1Digest(controlData)
+	pubKey, err := os.ReadFile("testdata/" + testPubkey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := signature.RSAVerifySHA1Digest(digest, sig, pubKey); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func computeSHA1Digest(data []byte) []byte {
+	digest := sha1.New()
+	_, _ = digest.Write(data)
+	return digest.Sum(nil)
+}
+
+func parseAPK(ctx context.Context, apkPath string) (control []byte, sigName string, sig []byte, err error) {
+	apkr, err := os.Open(apkPath)
+	if err != nil {
+		return nil, "", nil, err
+	}
+	eapk, err := expandapk.ExpandApk(context.TODO(), apkr, "")
+	if err != nil {
+		return nil, "", nil, err
+	}
+	defer eapk.Close()
+	gzSig, err := os.ReadFile(eapk.SignatureFile)
+	if err != nil {
+		return nil, "", nil, err
+	}
+	zr, err := gzip.NewReader(bytes.NewReader(gzSig))
+	if err != nil {
+		return nil, "", nil, err
+	}
+	tr := tar.NewReader(zr)
+	hdr, err := tr.Next()
+	if err != nil {
+		return nil, "", nil, err
+	}
+	if !strings.HasPrefix(hdr.Name, ".SIGN.") {
+		return nil, "", nil, fmt.Errorf("unexpected header name %s", hdr.Name)
+	}
+	sig, err = io.ReadAll(tr)
+	control, err = os.ReadFile(eapk.ControlFile)
+	if err != nil {
+		return nil, "", nil, err
+	}
+	return control, hdr.Name, sig, err
+}
+
+func CopyFile(src, dest string) error {
+	b, err := os.ReadFile(src)
+	if err != nil {
+		return err
+	}
+	if err := os.WriteFile(dest, b, 0644); err != nil {
+		return err
+	}
+	return nil
+}

pkg/sign/testdata/test.pem

@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----

pkg/sign/testdata/test.pem.pub

@@ -0,0 +1,9 @@
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAm+LrkhrpjcH7xBTm2HvR
+kEQBOn/VLbCqNmG7+7/WKWaim1bmAcj/o/grb7NUXUH529aIa+Ue4q8b4g8J8I6r
+BWZ32f8mQ/iMereQYe0uoyhjb3pxHZZDdj7q0nq5WyYTGl0nCs/0YHed0F442vCq
+QEBEvOeI4fXx1VWlmc9zX5px6/sFPQbrS3jAD5AjGgbB5JlW3c3cqWqvQu1/P1t+
+euOnhLCaCKQXehezwOajlj36qfbREyH2SmEk5x2OIo4r5MD9kozBeLJnqaU1svUe
+3EF7wK/qiLtUYi7V2NkAL2sR0goOxavovHQZpJFfKw72gXE+I3omHSb/VSPEQuCj
+wQIDAQAB
+-----END PUBLIC KEY-----