fix(provenance): accept signed SHA when archive name differs from Chart.yaml

helm package records Chart.yaml's name in the provenance Files map. helm
pull --verify looked that entry up from the repository path, so a chart
published under a different name failed with "provenance does not contain
a SHA for a file named ...". The signature already authenticates the
Files map; a matching hash is enough.

Fixes #32546

Signed-off-by: Md Tanvir Alam <tanviralamshuvo@gmail.com>

pkg/provenance/sign.go

@@ -238,6 +238,11 @@ func (s *Signatory) ClearSign(archiveData []byte, filename string, metadataBytes
 
 // Verify checks a signature and verifies that it is legit for package data.
 // This is the core verification method that works with data in memory.
+//
+// filename is the local archive name. If that name is not in the signed Files
+// map, a Files entry whose SHA matches the archive is accepted. helm package
+// records Chart.yaml's name, which can differ from the repository path helm
+// pull uses to name the downloaded file.
 func (s *Signatory) Verify(archiveData, provData []byte, filename string) (*Verification, error) {
 	ver := &Verification{}
 
@@ -264,19 +269,36 @@ func (s *Signatory) Verify(archiveData, provData []byte, filename string) (*Veri
 	}
 
 	sum = "sha256:" + sum
-	if sha, ok := sums.Files[filename]; !ok {
-		return ver, fmt.Errorf("provenance does not contain a SHA for a file named %q", filename)
-	} else if sha != sum {
-		return ver, fmt.Errorf("sha256 sum does not match for %s: %q != %q", filename, sha, sum)
+	signedName, err := matchSignedFile(sums.Files, filename, sum)
+	if err != nil {
+		return ver, err
 	}
 	ver.FileHash = sum
-	ver.FileName = filename
+	ver.FileName = signedName
 
 	// TODO: when image signing is added, verify that here.
 
 	return ver, nil
 }
 
+// matchSignedFile returns the Files key that covers archiveSum.
+// If filename is present it must match; otherwise any signed name with the
+// same hash is accepted (repository path vs Chart.yaml name).
+func matchSignedFile(files map[string]string, filename, archiveSum string) (string, error) {
+	if sha, ok := files[filename]; ok {
+		if sha != archiveSum {
+			return "", fmt.Errorf("sha256 sum does not match for %s: %q != %q", filename, sha, archiveSum)
+		}
+		return filename, nil
+	}
+	for signedName, sha := range files {
+		if sha == archiveSum {
+			return signedName, nil
+		}
+	}
+	return "", fmt.Errorf("provenance does not contain a SHA for a file named %q", filename)
+}
+
 // verifySignature verifies that the given block is validly signed, and returns the signer.
 func (s *Signatory) verifySignature(block *clearsign.Block) (*openpgp.Entity, error) {
 	return openpgp.CheckDetachedSignature(

pkg/provenance/sign_test.go

@@ -386,6 +386,32 @@ func TestVerify(t *testing.T) {
 	}
 }
 
+func TestVerifyFilenameDiffersFromProvenance(t *testing.T) {
+	signer, err := NewFromFiles(testKeyfile, testPubfile)
+	require.NoError(t, err)
+
+	archiveData, err := os.ReadFile(testChartfile)
+	require.NoError(t, err)
+
+	sigData, err := os.ReadFile(testSigBlock)
+	require.NoError(t, err)
+
+	// helm pull --verify names the archive from the repository path, which can
+	// differ from the Chart.yaml name recorded in the provenance Files map.
+	ver, err := signer.Verify(archiveData, sigData, "otherrepo-1.2.3.tgz")
+	require.NoError(t, err)
+	assert.Equal(t, "hashtest-1.2.3.tgz", ver.FileName)
+	assert.Equal(t, "sha256:c6841b3a895f1444a6738b5d04564a57e860ce42f8519c3be807fb6d9bee7888", ver.FileHash)
+
+	_, err = signer.Verify([]byte("not the signed archive"), sigData, "otherrepo-1.2.3.tgz")
+	require.Error(t, err)
+	assert.ErrorContains(t, err, `provenance does not contain a SHA for a file named "otherrepo-1.2.3.tgz"`)
+
+	_, err = signer.Verify([]byte("not the signed archive"), sigData, filepath.Base(testChartfile))
+	require.Error(t, err)
+	assert.ErrorContains(t, err, "sha256 sum does not match")
+}
+
 // TestVerifyKeyboxKeyring mirrors TestVerify with the keyring loaded from a
 // GnuPG keybox instead of the legacy binary format.
 func TestVerifyKeyboxKeyring(t *testing.T) {