From b7da1f771c746658530fdb2f29543338bb10752d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexander=20Gr=C3=A4b?= <alexander.graeb@secustack.com>
Date: Fri, 8 Feb 2019 11:13:11 +0100
Subject: [PATCH] Made HMAC Key Wrap mechanism configurable

Introduced the parameter 'hmac_keywrap_mechanism' in group
'[p11_crypto_plugin]' in Barbican config. The default value, which were
hard coded before, is 'CKM_SHA256_HMAC'. This defines the machanism used
to compute the HMAC from an wrapped PKEK. However with Utimaco HSMs this
leads to an CKR_MECHANISM_INVALID error. Therefore for Utimaco HSMs
'hmac_keywrap_mechanism' has to be changed to 'CKM_AES_MAC'.

Change-Id: I53537a96bc4b2acb30be5fa85e10bac89917851f
Story: 2004833
Task: 29027
---
 barbican/cmd/barbican_manage.py               | 37 ++++++++++++++-----
 barbican/plugin/crypto/p11_crypto.py          |  4 ++
 barbican/plugin/crypto/pkcs11.py              | 18 +++++++--
 .../tests/plugin/crypto/test_p11_crypto.py    |  2 +
 barbican/tests/plugin/crypto/test_pkcs11.py   |  4 +-
 .../fix-story-2004833-2b420688a82c3328.yaml   |  9 +++++
 6 files changed, 61 insertions(+), 13 deletions(-)
 create mode 100644 releasenotes/notes/fix-story-2004833-2b420688a82c3328.yaml

diff --git a/barbican/cmd/barbican_manage.py b/barbican/cmd/barbican_manage.py
index d1572c997..6ccfdf1cd 100644
--- a/barbican/cmd/barbican_manage.py
+++ b/barbican/cmd/barbican_manage.py
@@ -184,9 +184,14 @@ class HSMCommands(object):
           help='Password to login to PKCS11 session')
     @args('--label', '-L', metavar='<label>', default='primarymkek',
           help='The label of the Master Key Encrypt Key')
-    def check_mkek(self, passphrase, libpath=None, slotid=None, label=None):
+    @args('--hmac-wrap-mechanism', metavar='<hmac key wrap mechanism>',
+          dest='hmacwrap', default='CKM_SHA256_HMAC',
+          help='HMAC Key wrap mechanism, default is CKM_SHA256_HMAC')
+    def check_mkek(self, passphrase, libpath=None, slotid=None, label=None,
+                   hmacwrap=None):
         CKK_AES = 'CKK_AES'
-        self._create_pkcs11_session(str(passphrase), str(libpath), int(slotid))
+        self._create_pkcs11_session(str(passphrase), str(libpath),
+                                    int(slotid), str(hmacwrap))
         handle = self.pkcs11.get_key_handle(CKK_AES, str(label), self.session)
         self.pkcs11.return_session(self.session)
         if not handle:
@@ -208,11 +213,15 @@ class HSMCommands(object):
     @args('--length', '-l', metavar='<length>', default=32,
           help='The length in bytes of the Master Key Encryption Key'
                ' (default is 32)')
+    @args('--hmac-wrap-mechanism', metavar='<hmac key wrap mechanism>',
+          dest='hmacwrap', default='CKM_SHA256_HMAC',
+          help='HMAC Key wrap mechanism, default is CKM_SHA256_HMAC')
     def gen_mkek(self, passphrase, libpath=None, slotid=None, label=None,
-                 length=None):
+                 length=None, hmacwrap=None):
         CKK_AES = 'CKK_AES'
         CKM_AES_KEY_GEN = 'CKM_AES_KEY_GEN'
-        self._create_pkcs11_session(str(passphrase), str(libpath), int(slotid))
+        self._create_pkcs11_session(str(passphrase), str(libpath),
+                                    int(slotid), str(hmacwrap))
         self._verify_label_does_not_exist(CKK_AES, str(label), self.session)
         self.pkcs11.generate_key(CKK_AES, int(length), CKM_AES_KEY_GEN,
                                  self.session, str(label),
@@ -234,9 +243,13 @@ class HSMCommands(object):
           help='The label of the Master HMAC key')
     @args('--key-type', '-t', metavar='<key type>', dest='keytype',
           default='CKK_AES', help='The HMAC Key Type (e.g. CKK_AES)')
+    @args('--hmac-wrap-mechanism', metavar='<hmac key wrap mechanism>',
+          dest='hmacwrap', default='CKM_SHA256_HMAC',
+          help='HMAC Key wrap mechanism, default is CKM_SHA256_HMAC')
     def check_hmac(self, passphrase, libpath=None, slotid=None, label=None,
-                   keytype=None):
-        self._create_pkcs11_session(str(passphrase), str(libpath), int(slotid))
+                   keytype=None, hmacwrap=None):
+        self._create_pkcs11_session(str(passphrase), str(libpath),
+                                    int(slotid), str(hmacwrap))
         handle = self.pkcs11.get_key_handle(str(keytype), str(label),
                                             self.session)
         self.pkcs11.return_session(self.session)
@@ -262,9 +275,13 @@ class HSMCommands(object):
           help='The length in bytes of the Master HMAC Key (default is 32)')
     @args('--mechanism', '-m', metavar='<mechanism>',
           default='CKM_AES_KEY_GEN', help='The HMAC Key Generation mechanism')
+    @args('--hmac-wrap-mechanism', metavar='<hmac key wrap mechanism>',
+          dest='hmacwrap', default='CKM_SHA256_HMAC',
+          help='HMAC Key wrap mechanism, default is CKM_SHA256_HMAC')
     def gen_hmac(self, passphrase, libpath=None, slotid=None, label=None,
-                 keytype=None, mechanism=None, length=None):
-        self._create_pkcs11_session(str(passphrase), str(libpath), int(slotid))
+                 keytype=None, mechanism=None, length=None, hmacwrap=None):
+        self._create_pkcs11_session(str(passphrase), str(libpath), int(slotid),
+                                    str(hmacwrap))
         self._verify_label_does_not_exist(str(keytype), str(label),
                                           self.session)
         self.pkcs11.generate_key(str(keytype), int(length), str(mechanism),
@@ -282,11 +299,13 @@ class HSMCommands(object):
         rewrapper.execute(dryrun)
         rewrapper.pkcs11.return_session(rewrapper.hsm_session)
 
-    def _create_pkcs11_session(self, passphrase, libpath, slotid):
+    def _create_pkcs11_session(self, passphrase, libpath, slotid,
+                               hmacwrap):
         self.pkcs11 = pkcs11.PKCS11(
             library_path=libpath, login_passphrase=passphrase,
             rw_session=True, slot_id=slotid,
             encryption_mechanism='CKM_AES_CBC',
+            hmac_keywrap_mechanism=hmacwrap
         )
         self.session = self.pkcs11.get_session()
 
diff --git a/barbican/plugin/crypto/p11_crypto.py b/barbican/plugin/crypto/p11_crypto.py
index 56b3fb71a..8aea72dfa 100644
--- a/barbican/plugin/crypto/p11_crypto.py
+++ b/barbican/plugin/crypto/p11_crypto.py
@@ -69,6 +69,9 @@ p11_crypto_plugin_opts = [
     cfg.StrOpt('hmac_keygen_mechanism',
                help=u._('HMAC Key Generation Algorithm'),
                default='CKM_AES_KEY_GEN'),
+    cfg.StrOpt('hmac_keywrap_mechanism',
+               help=u._('HMAC key wrap mechanism'),
+               default='CKM_SHA256_HMAC'),
     cfg.StrOpt('seed_file',
                help=u._('File to pull entropy for seeding RNG'),
                default=''),
@@ -307,6 +310,7 @@ class P11CryptoPlugin(plugin.CryptoPluginBase):
             seed_random_buffer=seed_random_buffer,
             generate_iv=plugin_conf.aes_gcm_generate_iv,
             always_set_cka_sensitive=plugin_conf.always_set_cka_sensitive,
+            hmac_keywrap_mechanism=plugin_conf.hmac_keywrap_mechanism
         )
 
     def _reinitialize_pkcs11(self):
diff --git a/barbican/plugin/crypto/pkcs11.py b/barbican/plugin/crypto/pkcs11.py
index 737d5a9b6..c394a16b5 100644
--- a/barbican/plugin/crypto/pkcs11.py
+++ b/barbican/plugin/crypto/pkcs11.py
@@ -134,6 +134,7 @@ CKA_SUPPORTED_CMS_ATTRIBUTES = 0x503
 CKM_SHA256_HMAC = 0x251
 CKM_AES_KEY_GEN = 0x1080
 CKM_AES_CBC = 0x1082
+CKM_AES_MAC = 0x1083
 CKM_AES_CBC_PAD = 0x1085
 CKM_AES_GCM = 0x1087
 CKM_AES_KEY_WRAP = 0x1090
@@ -158,9 +159,15 @@ _KEY_GEN_MECHANISMS = {
     'CKM_GENERIC_SECRET_KEY_GEN': CKM_GENERIC_SECRET_KEY_GEN,
 }
 
+_KEY_WRAP_MECHANISMS = {
+    'CKM_SHA256_HMAC': CKM_SHA256_HMAC,
+    'CKM_AES_MAC': CKM_AES_MAC
+}
+
 CKM_NAMES = dict()
 CKM_NAMES.update(_ENCRYPTION_MECHANISMS)
 CKM_NAMES.update(_KEY_GEN_MECHANISMS)
+CKM_NAMES.update(_KEY_WRAP_MECHANISMS)
 
 ERROR_CODES = {
     1: 'CKR_CANCEL',
@@ -356,7 +363,8 @@ class PKCS11(object):
                  encryption_mechanism=None,
                  ffi=None, algorithm=None,
                  seed_random_buffer=None,
-                 generate_iv=None, always_set_cka_sensitive=None):
+                 generate_iv=None, always_set_cka_sensitive=None,
+                 hmac_keywrap_mechanism='CKM_SHA256_HMAC'):
         if algorithm:
             LOG.warning("WARNING: Using deprecated 'algorithm' argument.")
             encryption_mechanism = encryption_mechanism or algorithm
@@ -369,6 +377,9 @@ class PKCS11(object):
             '_{}_encrypt'.format(encryption_mechanism)
         )
 
+        if hmac_keywrap_mechanism not in _KEY_WRAP_MECHANISMS:
+            raise ValueError("Invalid HMAC keywrap mechanism")
+
         self.ffi = ffi or build_ffi()
         self.lib = self.ffi.dlopen(library_path)
         rv = self.lib.C_Initialize(self.ffi.NULL)
@@ -386,6 +397,7 @@ class PKCS11(object):
         self.gcmtagsize = 16
         self.generate_iv = generate_iv
         self.always_set_cka_sensitive = always_set_cka_sensitive
+        self.hmac_keywrap_mechanism = CKM_NAMES[hmac_keywrap_mechanism]
 
         # Validate configuration and RNG
         session = self.get_session()
@@ -674,7 +686,7 @@ class PKCS11(object):
 
     def compute_hmac(self, hmac_key, data, session):
         mech = self.ffi.new("CK_MECHANISM *")
-        mech.mechanism = CKM_SHA256_HMAC
+        mech.mechanism = self.hmac_keywrap_mechanism
         rv = self.lib.C_SignInit(session, mech, hmac_key)
         self._check_error(rv)
 
@@ -687,7 +699,7 @@ class PKCS11(object):
 
     def verify_hmac(self, hmac_key, sig, data, session):
         mech = self.ffi.new("CK_MECHANISM *")
-        mech.mechanism = CKM_SHA256_HMAC
+        mech.mechanism = self.hmac_keywrap_mechanism
 
         rv = self.lib.C_VerifyInit(session, mech, hmac_key)
         self._check_error(rv)
diff --git a/barbican/tests/plugin/crypto/test_p11_crypto.py b/barbican/tests/plugin/crypto/test_p11_crypto.py
index c919ba946..a7d05a285 100644
--- a/barbican/tests/plugin/crypto/test_p11_crypto.py
+++ b/barbican/tests/plugin/crypto/test_p11_crypto.py
@@ -63,6 +63,8 @@ class WhenTestingP11CryptoPlugin(utils.BaseTestCase):
         self.cfg_mock.p11_crypto_plugin.encryption_mechanism = 'CKM_AES_CBC'
         self.cfg_mock.p11_crypto_plugin.seed_file = ''
         self.cfg_mock.p11_crypto_plugin.seed_length = 32
+        self.cfg_mock.p11_crypto_plugin.hmac_keywrap_mechanism = \
+            'CKM_SHA256_HMAC'
 
         self.plugin_name = 'Test PKCS11 plugin'
         self.cfg_mock.p11_crypto_plugin.plugin_name = self.plugin_name
diff --git a/barbican/tests/plugin/crypto/test_pkcs11.py b/barbican/tests/plugin/crypto/test_pkcs11.py
index 938f1264b..afb9ffca5 100644
--- a/barbican/tests/plugin/crypto/test_pkcs11.py
+++ b/barbican/tests/plugin/crypto/test_pkcs11.py
@@ -60,12 +60,14 @@ class WhenTestingPKCS11(utils.BaseTestCase):
         self.cfg_mock.rw_session = False
         self.cfg_mock.slot_id = 1
         self.cfg_mock.encryption_mechanism = 'CKM_AES_CBC'
+        self.cfg_mock.hmac_keywrap_mechanism = 'CKM_SHA256_HMAC'
 
         self.pkcs11 = pkcs11.PKCS11(
             self.cfg_mock.library_path, self.cfg_mock.login_passphrase,
             self.cfg_mock.rw_session, self.cfg_mock.slot_id,
             self.cfg_mock.encryption_mechanism,
-            ffi=self.ffi
+            ffi=self.ffi,
+            hmac_keywrap_mechanism=self.cfg_mock.hmac_keywrap_mechanism
         )
 
     def _generate_random(self, session, buf, length):
diff --git a/releasenotes/notes/fix-story-2004833-2b420688a82c3328.yaml b/releasenotes/notes/fix-story-2004833-2b420688a82c3328.yaml
new file mode 100644
index 000000000..a73b966b8
--- /dev/null
+++ b/releasenotes/notes/fix-story-2004833-2b420688a82c3328.yaml
@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixed Story #2004734: Added a new option 'hmac_keywrap_mechanism' to make
+    the mechanism used to calculate a HMAC from an wrapped PKEK configurable.
+    This was introduced because of an problem with Utimaco HSMs which throw an
+    'CKR_MECHANISM_INVALID' error, e.g. when a new PKEK is generated. For
+    Utimaco HSMs, 'hmac_keywrap_mechanism' should be set to 'CKM_AES_MAC' in
+    barbican.conf.