lmp-el2go-auto-register: fix PKCS#11 slot initialization

This patch fixes the potential issues when running the auto-registration
script on the device:

1. 1st slot gets overwritten
If the 1st slot is not labeled 'aktualizr' and lmp-el2go-auto-register
can't log into it with it's default PIN it would overwrite it. This
might mean data loss for some othe deamon which initialized the slot

2. Objects not stored in proper slots
When writing to pkcs#11 lmp-el2go-auto-register was not using the slot
label consistently. This means that some objects were written in proper
slot while some other not. This would only happen if the 1st slot (0x0)
was initialized with default PIN.

3. has_labels method doesn't use slot label
For this reason it would always try to access 1st slot (0x0) and ignore
the label. If slot with label 'aktualizr' was initialized in different
position this would mean the certificate/key objects would not be stored
properly.

Signed-off-by: Milosz Wasilewski <milosz.wasilewski@foundries.io>

meta-lmp-base/recipes-support/lmp-el2go-auto-register/lmp-el2go-auto-register/lmp-el2go-auto-register

@@ -4,6 +4,7 @@
 # Copyright (c) 2022, Foundries.io Ltd.
 
 from contextlib import contextmanager
+import re
 import os
 import logging
 import subprocess
@@ -18,6 +19,7 @@ PIN = os.environ.get("PKCS11_PIN", "87654321")
 SO_PIN = os.environ.get("PKCS11_SOPIN", "12345678")
 SOTA_DIR = os.environ.get("SOTA_DIR", "/var/sota")
 HANDLERS = os.environ.get("HANDLERS", "aws-iot,aktualizr-lite")
+TOKEN_LABEL = os.environ.get("TOKEN_LABEL", "aktualizr")
 
 REPO_ID = os.environ["REPOID"]
 
@@ -46,7 +48,7 @@ class Pkcs11:
             "--key-type=EC:prime256v1",
             f"--id={slot}",
             f"--label={label}",
-            "--token-label=aktualizr",
+            f"--token-label={TOKEN_LABEL}",
         ]
         run_quietly(args)
 
@@ -60,11 +62,12 @@ class Pkcs11:
             f"--type={type}",
             f"--id={slot}",
             f"--label={label}",
+            f"--token-label={TOKEN_LABEL}",
         ]
         run_quietly(args)
 
     def has_labels(self, labels: List[str]) -> bool:
-        args = ["pkcs11-tool", f"--module={self.LIB}", f"--pin={PIN}", "--list-objects"]
+        args = ["pkcs11-tool", f"--module={self.LIB}", f"--pin={PIN}", f"--token-label={TOKEN_LABEL}", "--list-objects"]
         out = subprocess.check_output(args)
         missing = {x: 1 for x in labels}
         for line in out.decode().splitlines():
@@ -76,20 +79,59 @@ class Pkcs11:
                         pass  # already removed
         return len(missing) == 0
 
+    @classmethod
+    def _init_slot_dictionary(cls, pkcs11_output: str) -> dict:
+        slot_dict = {}
+        slot_id = None
+        r = re.compile("\((?P<slot_id>[0-9x]{3})\)")
+
+        for line in pkcs11_output.splitlines():
+            if line.startswith("Slot"):
+                # decode slot ID
+                # assume output in format:
+                # Slot 0 (0x0): 710be08c-e795-597d-bf30-2a98bab41050
+                g = r.search(line)
+                slot_id = g.group("slot_id")
+                slot_dict.update({slot_id: {}})
+            if line.startswith(" "):
+                # decode slot dictionary
+                # assume output in format:
+                #   token label        : testtoken
+                parts = line.split(":", 1)
+                slot_dict[slot_id].update({parts[0].strip(): parts[1].strip()})
+        return slot_dict
+
     @classmethod
     def _is_initialized(cls) -> bool:
-        args = ["pkcs11-tool", f"--module={cls.LIB}", f"--pin={PIN}", "--list-objects"]
+        args = ["pkcs11-tool", f"--module={cls.LIB}", "--list-slots"]
         try:
-            subprocess.check_output(args, stderr=subprocess.STDOUT)
+            out = subprocess.check_output(args, stderr=subprocess.STDOUT)
+            slot_dict = cls._init_slot_dictionary(out.decode())
+            for slot_id, slot in slot_dict.items():
+                token_label = slot.get("token label")
+                if token_label == f"{TOKEN_LABEL}":
+                    return True
         except subprocess.CalledProcessError:
             return False
-        return True
+        return False
 
     @classmethod
     def _initialize(cls):
+        args = ["pkcs11-tool", f"--module={cls.LIB}", "--list-slots"]
+        out = subprocess.check_output(args, stderr=subprocess.STDOUT)
+        slot_dict = cls._init_slot_dictionary(out.decode())
+        empty_slot = None
+        for slot_id, slot in slot_dict.items():
+            token_state = slot.get("token state")
+            if token_state == "uninitialized":
+                empty_slot = slot_id
+                break
+        if empty_slot is None:
+            # raise exception as there are no more available slots
+            raise RuntimeError("No free PKCS11 slots")
         args = ["pkcs11-tool", f"--module={cls.LIB}", f"--so-pin={SO_PIN}"]
-        subprocess.check_call(args + ["--init-token", "--label", "aktualizr"])
-        subprocess.check_call(args + ["--init-pin", f"--pin={PIN}"])
+        subprocess.check_call(args + ["--init-token", "--label", f"{TOKEN_LABEL}", "--slot", f"{empty_slot}"])
+        subprocess.check_call(args + ["--init-pin", f"--pin={PIN}", "--slot", f"{empty_slot}"])
 
     @classmethod
     def get_initialized(cls) -> "Pkcs11":