Fix PKCS11 helper

Slots in HSM are not assigned statically, we have to chose proper
slot from token label.

Softhsm i2.2.0 changed this behavior and now slots can change over
time (it is allowed by pkcs11 standard).

Changelog:
* created method get_slot() that returns slot number from
  used label
* replaces usage of slot in __init__ method of P11_Helper
  with label
* slot is dynamically detected from token label before
  session is opened
* pkcs11-util --init-token now uses '--free' instead '--slot'
  which uses first free slot (we don't care about slot numbers
  anymore)

https://pagure.io/freeipa/issue/6692

Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>

ipaserver/p11helper.py

@@ -30,6 +30,7 @@ struct _CK_VERSION
 };
 
 typedef unsigned long CK_SLOT_ID;
+typedef CK_SLOT_ID *CK_SLOT_ID_PTR;
 
 typedef unsigned long CK_SESSION_HANDLE;
 
@@ -43,6 +44,13 @@ typedef unsigned long CK_KEY_TYPE;
 
 typedef unsigned long CK_ATTRIBUTE_TYPE;
 
+typedef unsigned long ck_flags_t;
+
+typedef unsigned char CK_BBOOL;
+
+typedef unsigned long int CK_ULONG;
+typedef CK_ULONG *CK_ULONG_PTR;
+
 struct _CK_ATTRIBUTE
 {
   CK_ATTRIBUTE_TYPE type;
@@ -59,6 +67,31 @@ struct _CK_MECHANISM
   unsigned long ulParameterLen;
 };
 
+struct _CK_TOKEN_INFO
+{
+  unsigned char label[32];
+  unsigned char manufacturer_id[32];
+  unsigned char model[16];
+  unsigned char serial_number[16];
+  ck_flags_t flags;
+  unsigned long max_session_count;
+  unsigned long session_count;
+  unsigned long max_rw_session_count;
+  unsigned long rw_session_count;
+  unsigned long max_pin_len;
+  unsigned long min_pin_len;
+  unsigned long total_public_memory;
+  unsigned long free_public_memory;
+  unsigned long total_private_memory;
+  unsigned long free_private_memory;
+  struct _CK_VERSION hardware_version;
+  struct _CK_VERSION firmware_version;
+  unsigned char utc_time[16];
+};
+
+typedef struct _CK_TOKEN_INFO CK_TOKEN_INFO;
+typedef CK_TOKEN_INFO *CK_TOKEN_INFO_PTR;
+
 typedef unsigned long CK_RV;
 
 typedef ... *CK_NOTIFY;
@@ -70,9 +103,12 @@ typedef CK_RV (*CK_C_Finalize) (void *pReserved);
 typedef ... *CK_C_GetInfo;
 typedef ... *CK_C_GetFunctionList;
 CK_RV C_GetFunctionList (struct _CK_FUNCTION_LIST **function_list);
-typedef ... *CK_C_GetSlotList;
+typedef CK_RV (*CK_C_GetSlotList) (CK_BBOOL tokenPresent,
+                                   CK_SLOT_ID_PTR pSlotList,
+                                   CK_ULONG_PTR pulCount);
 typedef ... *CK_C_GetSlotInfo;
-typedef ... *CK_C_GetTokenInfo;
+typedef CK_RV (*CK_C_GetTokenInfo) (CK_SLOT_ID slotID,
+                                    CK_TOKEN_INFO_PTR pInfo);
 typedef ... *CK_C_WaitForSlotEvent;
 typedef ... *CK_C_GetMechanismList;
 typedef ... *CK_C_GetMechanismInfo;
@@ -255,10 +291,7 @@ struct _CK_FUNCTION_LIST
 
 typedef unsigned char CK_BYTE;
 typedef unsigned char CK_UTF8CHAR;
-typedef unsigned char CK_BBOOL;
-typedef unsigned long int CK_ULONG;
 typedef CK_BYTE *CK_BYTE_PTR;
-typedef CK_ULONG *CK_ULONG_PTR;
 
 typedef CK_OBJECT_HANDLE *CK_OBJECT_HANDLE_PTR;
 
@@ -387,6 +420,7 @@ CKM_AES_KEY_GEN = 0x1080
 CKR_OK = 0
 CKR_ATTRIBUTE_TYPE_INVALID = 0x12
 CKR_USER_NOT_LOGGED_IN = 0x101
+CKR_BUFFER_TOO_SMALL = 0x150
 
 CK_BYTE = _ffi.typeof('CK_BYTE')
 CK_BBOOL = _ffi.typeof('CK_BBOOL')
@@ -403,6 +437,10 @@ CK_MECHANISM = _ffi.typeof('CK_MECHANISM')
 
 CK_FUNCTION_LIST_PTR = _ffi.typeof('CK_FUNCTION_LIST_PTR')
 
+CK_SLOT_ID = _ffi.typeof('CK_SLOT_ID')
+
+CK_TOKEN_INFO = _ffi.typeof('CK_TOKEN_INFO')
+
 NULL_PTR = NULL
 
 
@@ -796,11 +834,10 @@ class P11_Helper(object):
         # Object not found
         return False
 
-    def __init__(self, slot, user_pin, library_path):
+    def __init__(self, token_label, user_pin, library_path):
         self.p11_ptr = new_ptr(CK_FUNCTION_LIST_PTR)
         self.session_ptr = new_ptr(CK_SESSION_HANDLE)
 
-        self.slot = 0
         self.session_ptr[0] = 0
         self.p11_ptr[0] = NULL
         self.module_handle = None
@@ -808,7 +845,7 @@ class P11_Helper(object):
         # Parse method args
         if isinstance(user_pin, unicode):
             user_pin = user_pin.encode()
-        self.slot = slot
+        self.token_label = token_label
 
         try:
             pGetFunctionList, module_handle = loadLibrary(library_path)
@@ -828,10 +865,17 @@ class P11_Helper(object):
         rv = self.p11.C_Initialize(NULL)
         check_return_value(rv, "initialize")
 
+        #
+        # Get Slot
+        #
+        slot = self.get_slot()
+        if slot is None:
+            raise Error("No slot for label {} found".format(self.token_label))
+
         #
         # Start session
         #
-        rv = self.p11.C_OpenSession(self.slot,
+        rv = self.p11.C_OpenSession(slot,
                                     CKF_SERIAL_SESSION | CKF_RW_SESSION, NULL,
                                     NULL, self.session_ptr)
         check_return_value(rv, "open session")
@@ -842,6 +886,49 @@ class P11_Helper(object):
         rv = self.p11.C_Login(self.session, CKU_USER, user_pin, len(user_pin))
         check_return_value(rv, "log in")
 
+    def get_slot(self):
+        """Get slot where then token is located
+        :return: slot number or None when slot not found
+        """
+        object_count_ptr = new_ptr(CK_ULONG)
+
+        # get slots ID
+        slots = None
+        for _i in range(0, 10):
+            # try max N times, then die to avoid infinite iteration
+            rv = self.p11.C_GetSlotList(CK_TRUE, NULL, object_count_ptr)
+            check_return_value(rv, "get slots IDs - prepare")
+
+            result_ids_ptr = new_array(CK_SLOT_ID, object_count_ptr[0])
+
+            rv = self.p11.C_GetSlotList(
+                CK_TRUE, result_ids_ptr, object_count_ptr)
+            if rv == CKR_BUFFER_TOO_SMALL:
+                continue
+            check_return_value(rv, "get slots IDs")
+            slots = result_ids_ptr
+            break  # we have slots !!!
+
+        if slots is None:
+            raise Error("Failed to get slots")
+
+        for slot in slots:
+            token_info_ptr = new_ptr(CK_TOKEN_INFO)
+            rv = self.p11.C_GetTokenInfo(slot, token_info_ptr)
+            check_return_value(rv, 'get token info')
+
+            # softhsm always returns label 32 bytes long with padding made of
+            # white spaces (#32), so we have to rstrip() padding and compare
+            # Label was created by softhsm-util so it is not our fault that
+            # there are #32 as padding (cffi initializes structures with
+            # zeroes)
+            # In case that this is not valid anymore, keep in mind backward
+            # compatibility
+
+            if self.token_label == char_array_to_unicode(
+                    token_info_ptr[0].label, 32).rstrip():
+                return slot
+
     def finalize(self):
         """
         Finalize operations with pkcs11 library
@@ -868,7 +955,6 @@ class P11_Helper(object):
 
         self.p11_ptr[0] = NULL
         self.session_ptr[0] = 0
-        self.slot = 0
         self.module_handle = None
 
     #################################################################