add CKM_EXTRACT_KEY_FROM_KEY mechanism

PyKCS11/__init__.py

@@ -987,6 +987,26 @@ def __init__(self, data):
         super().__init__(data, CKM_XOR_BASE_AND_DATA)
 
 
+class EXTRACT_KEY_FROM_KEY_Mechanism():
+    """CKM_EXTRACT_KEY_FROM_KEY key derivation mechanism"""
+
+    def __init__(self, extractParams):
+        """
+        :param extractParams: the index of the first bit of the original key to be used in the newly-derived key. 
+                              For example if extractParams=5 then the 5 first bits are skipped and not used.
+        """
+        self._param = PyKCS11.LowLevel.CK_EXTRACT_PARAMS()
+        self._param.assign(extractParams)
+
+        self._mech = PyKCS11.LowLevel.CK_MECHANISM()
+        self._mech.mechanism = CKM_EXTRACT_KEY_FROM_KEY
+        self._mech.pParameter = self._param
+        self._mech.ulParameterLen = PyKCS11.LowLevel.CK_EXTRACT_PARAMS_LENGTH
+
+    def to_native(self):
+        return self._mech
+
+
 class DigestSession(object):
     def __init__(self, lib, session, mecha):
         self._lib = lib

src/opensc/pkcs11.h

@@ -774,6 +774,8 @@ struct ck_key_derivation_string_data {
   unsigned long ulLen;
 } ;
 
+typedef unsigned long ck_extract_params;
+
 #define CKF_HW			(1 << 0)
 #define CKF_ENCRYPT		(1 << 8)
 #define CKF_DECRYPT		(1 << 9)
@@ -1354,6 +1356,9 @@ typedef struct ck_ecdh1_derive_params *CK_ECDH1_DERIVE_PARAMS_PTR;
 typedef struct ck_key_derivation_string_data CK_KEY_DERIVATION_STRING_DATA;
 typedef struct ck_key_derivation_string_data *CK_KEY_DERIVATION_STRING_DATA_PTR;
 
+typedef ck_extract_params CK_EXTRACT_PARAMS;
+typedef ck_extract_params *CK_EXTRACT_PARAMS_PTR;
+
 typedef struct ck_function_list CK_FUNCTION_LIST;
 typedef struct ck_function_list *CK_FUNCTION_LIST_PTR;
 typedef struct ck_function_list **CK_FUNCTION_LIST_PTR_PTR;
@@ -1432,6 +1437,8 @@ typedef struct ck_c_initialize_args *CK_C_INITIALIZE_ARGS_PTR;
 
 #undef ck_rsa_pkcs_pss_params
 
+#undef ck_extract_params
+
 #undef ck_rv_t
 #undef ck_notify_t
 

src/pykcs11.i

@@ -272,6 +272,10 @@ typedef struct CK_DATE{
             if( SWIG_IsOK( res2 ) )
                 break;
 
+            res2 = SWIG_ConvertPtr($input, &arg2, $descriptor(CK_EXTRACT_PARAMS*), 0);
+            if( SWIG_IsOK( res2 ) )
+                break;
+
             res2 = SWIG_ConvertPtr($input, &arg2, $descriptor(CK_OBJECT_HANDLE*), 0);
             if( SWIG_IsOK( res2 ) )
                 break;
@@ -492,6 +496,10 @@ typedef struct CK_KEY_DERIVATION_STRING_DATA {
 
 %constant int CK_KEY_DERIVATION_STRING_DATA_LENGTH = sizeof(CK_KEY_DERIVATION_STRING_DATA);
 
+%pointer_class(unsigned long, CK_EXTRACT_PARAMS);
+
+%constant int CK_EXTRACT_PARAMS_LENGTH = sizeof(CK_EXTRACT_PARAMS);
+
 typedef struct CK_MECHANISM_INFO {
 %immutable;
     unsigned long    ulMinKeySize;

test/test_derive.py

@@ -304,3 +304,35 @@ def test_deriveKey_CKM_XOR_BASE_AND_DATA(self):
 
         # cleanup
         self.session.destroyObject(derivedKey)
+
+    def test_deriveKey_CKM_EXTRACT_KEY_FROM_KEY(self):
+        if self.manufacturer.startswith("SoftHSM"):
+            self.skipTest("SoftHSM does not support CKM_EXTRACT_KEY_FROM_KEY")
+
+        # sample from the PKCS#11 specification 3.0, section 2.43.7
+        # see https://docs.oasis-open.org/pkcs11/pkcs11-curr/v3.0/os/pkcs11-curr-v3.0-os.html#_Toc30061466
+        baseKeyTemplate = self.genericKeyTemplate + [
+            (PyKCS11.CKA_DERIVE, PyKCS11.CK_TRUE),
+            (PyKCS11.CKA_VALUE, [0x32, 0x9f, 0x84, 0xa9])]
+
+        # create a base key
+        baseKey = self.session.createObject(baseKeyTemplate)
+
+        expectedDerivedKeyValue = [0x95, 0x26]
+
+        derivedKeyTemplate = self.genericKeyTemplate + [(
+            PyKCS11.CKA_VALUE_LEN, len(expectedDerivedKeyValue))]
+
+        # extract bytes from the base key
+        mechanism = PyKCS11.EXTRACT_KEY_FROM_KEY_Mechanism(21)
+        derivedKey = self.session.deriveKey(
+            baseKey, derivedKeyTemplate, mechanism)
+        self.assertIsNotNone(derivedKey)
+
+        derivedKeyValue = self.getCkaValue(derivedKey)
+
+        # match: check derived key value
+        self.assertSequenceEqual(expectedDerivedKeyValue, derivedKeyValue)
+
+        self.session.destroyObject(baseKey)
+        self.session.destroyObject(derivedKey)