Fix transit import/export of hmac-only keys (hashicorp#20864)

* Fix export of HMAC typed keys When initially implemented, exporting HMAC keys resulted in returning the unused, internal HMACKey value rather than the main Key value that is used for HMAC operations. This is a breaking change. Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com> * Consistently handle HMAC keys in keysutil When generating HMAC-typed keys, set HMACKey = Key consistently, to allow users of HMAC-typed keys to use them backwards compatibly. Notably, this could discard the (unused) HMACKey field set today. Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com> * Add test proving export of HMAC keys work Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com> * Add changelog entry Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com> --------- Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>
fopina · May 31, 2023 · daf72aa · daf72aa
1 parent c02c1da
commit daf72aa
Show file tree

Hide file tree

Showing 6 changed files with 34 additions and 3 deletions.
diff --git a/builtin/logical/transit/path_backup_test.go b/builtin/logical/transit/path_backup_test.go
@@ -39,6 +39,7 @@ func TestTransit_BackupRestore(t *testing.T) {
 	testBackupRestore(t, "rsa-2048", "hmac-verify")
 	testBackupRestore(t, "rsa-3072", "hmac-verify")
 	testBackupRestore(t, "rsa-4096", "hmac-verify")
+	testBackupRestore(t, "hmac", "hmac-verify")
 }
 
 func testBackupRestore(t *testing.T, keyType, feature string) {
@@ -57,6 +58,9 @@ func testBackupRestore(t *testing.T, keyType, feature string) {
 			"exportable": true,
 		},
 	}
+    if keyType == "hmac" {
+        keyReq.Data["key_size"] = 32
+    }
 	resp, err = b.HandleRequest(context.Background(), keyReq)
 	if err != nil || (resp != nil && resp.IsError()) {
 		t.Fatalf("resp: %#v\nerr: %v", resp, err)

diff --git a/builtin/logical/transit/path_byok_test.go b/builtin/logical/transit/path_byok_test.go
@@ -28,7 +28,8 @@ func TestTransit_BYOKExportImport(t *testing.T) {
 	testBYOKExportImport(t, "rsa-3072", "sign-verify")
 	testBYOKExportImport(t, "rsa-4096", "sign-verify")
 
-	// Unlike backup, we don't support importing HMAC keys here.
+	// Test HMAC sign/verify after a restore for supported keys.
+	testBYOKExportImport(t, "hmac", "hmac-verify")
 }
 
 func testBYOKExportImport(t *testing.T, keyType, feature string) {
@@ -47,6 +48,9 @@ func testBYOKExportImport(t *testing.T, keyType, feature string) {
 			"exportable": true,
 		},
 	}
+	if keyType == "hmac" {
+		keyReq.Data["key_size"] = 32
+	}
 	resp, err = b.HandleRequest(context.Background(), keyReq)
 	if err != nil || (resp != nil && resp.IsError()) {
 		t.Fatalf("resp: %#v\nerr: %v", resp, err)

diff --git a/builtin/logical/transit/path_export.go b/builtin/logical/transit/path_export.go
@@ -162,7 +162,11 @@ func getExportKey(policy *keysutil.Policy, key *keysutil.KeyEntry, exportType st
 
 	switch exportType {
 	case exportTypeHMACKey:
-		return strings.TrimSpace(base64.StdEncoding.EncodeToString(key.HMACKey)), nil
+		src := key.HMACKey
+		if policy.Type == keysutil.KeyType_HMAC {
+			src = key.Key
+		}
+		return strings.TrimSpace(base64.StdEncoding.EncodeToString(src)), nil
 
 	case exportTypeEncryptionKey:
 		switch policy.Type {

diff --git a/builtin/logical/transit/path_export_test.go b/builtin/logical/transit/path_export_test.go
@@ -28,6 +28,7 @@ func TestTransit_Export_KeyVersion_ExportsCorrectVersion(t *testing.T) {
 	verifyExportsCorrectVersion(t, "hmac-key", "ecdsa-p384")
 	verifyExportsCorrectVersion(t, "hmac-key", "ecdsa-p521")
 	verifyExportsCorrectVersion(t, "hmac-key", "ed25519")
+	verifyExportsCorrectVersion(t, "hmac-key", "hmac")
 }
 
 func verifyExportsCorrectVersion(t *testing.T, exportType, keyType string) {
@@ -43,6 +44,9 @@ func verifyExportsCorrectVersion(t *testing.T, exportType, keyType string) {
 		"exportable": true,
 		"type":       keyType,
 	}
+	if keyType == "hmac" {
+		req.Data["key_size"] = 32
+	}
 	_, err := b.HandleRequest(context.Background(), req)
 	if err != nil {
 		t.Fatal(err)

diff --git a/changelog/20864.txt b/changelog/20864.txt
@@ -0,0 +1,5 @@
+```release-note:bug
+secrets/transit: Fix export of HMAC-only key, correctly exporting the key used for sign operations. For consumers of the previously incorrect key, use the plaintext export to retrieve these incorrect keys and import them as new versions.
+secrets/transit: Fix bug related to shorter dedicated HMAC key sizing.
+sdk/helper/keysutil: New HMAC type policies will have HMACKey equal to Key and be copied over on import.
+```
diff --git a/sdk/helper/keysutil/policy.go b/sdk/helper/keysutil/policy.go
@@ -767,6 +767,10 @@ func (p *Policy) Upgrade(ctx context.Context, storage logical.Storage, randReade
 		entry.HMACKey = hmacKey
 		p.Keys[strconv.Itoa(p.LatestVersion)] = entry
 		persistNeeded = true
+
+		if p.Type == KeyType_HMAC {
+			entry.HMACKey = entry.Key
+		}
 	}
 
 	if persistNeeded {
@@ -1497,6 +1501,7 @@ func (p *Policy) ImportPublicOrPrivate(ctx context.Context, storage logical.Stor
 		entry.Key = key
 		if p.Type == KeyType_HMAC {
 			p.KeySize = len(key)
+			entry.HMACKey = key
 		}
 	} else {
 		var parsedKey any
@@ -1613,7 +1618,7 @@ func (p *Policy) RotateInMemory(randReader io.Reader) (retErr error) {
 		if p.Type == KeyType_AES128_GCM96 {
 			numBytes = 16
 		} else if p.Type == KeyType_HMAC {
-			numBytes := p.KeySize
+			numBytes = p.KeySize
 			if numBytes < HmacMinKeySize || numBytes > HmacMaxKeySize {
 				return fmt.Errorf("invalid key size for HMAC key, must be between %d and %d bytes", HmacMinKeySize, HmacMaxKeySize)
 			}
@@ -1624,6 +1629,11 @@ func (p *Policy) RotateInMemory(randReader io.Reader) (retErr error) {
 		}
 		entry.Key = newKey
 
+		if p.Type == KeyType_HMAC {
+			// To avoid causing problems, ensure HMACKey = Key.
+			entry.HMACKey = newKey
+		}
+
 	case KeyType_ECDSA_P256, KeyType_ECDSA_P384, KeyType_ECDSA_P521:
 		var curve elliptic.Curve
 		switch p.Type {