wip; removing direct use of ecdsa

circuitmatter/__init__.py

@@ -7,7 +7,7 @@
 import binascii
 import hashlib
 import json
-import pathlib
+import os
 import time
 
 from . import case, interaction_model, nonvolatile, session
@@ -48,8 +48,9 @@ def __init__(
             random_source = random
         self.random = random_source
 
-        state_file = pathlib.Path(state_filename)
-        if not state_file.exists():
+        try:
+            os.stat(state_filename)
+        except OSError:
             from circuitmatter import certificates
 
             initial_state = certificates.generate_initial_state(

circuitmatter/certificates.py

@@ -11,7 +11,7 @@
 from ecdsa import der
 from ecdsa.curves import NIST256p
 
-from . import pase, tlv
+from . import crypto, pase, tlv
 from .data_model import Enum8
 
 PAI_KEY_DER = b"\x30\x77\x02\x01\x01\x04\x20\xbb\x76\xa5\x80\x5f\x97\x26\x49\xaf\x1e\x8a\x87\xdc\x45\x57\xe6\x2c\x09\x00\xe5\x07\x09\xe8\x5c\x79\xc6\x44\xdf\x78\x90\xe5\x96\xa0\x0a\x06\x08\x2a\x86\x48\xce\x3d\x03\x01\x07\xa1\x44\x03\x42\x00\x04\x37\x5d\x2b\xc8\xc6\x15\x27\x5b\xfd\x84\x8b\x52\xfe\x21\x96\xe2\xa1\x4e\xf3\xcc\x91\xae\xf0\x5d\xff\x85\x1c\xbc\x19\xb1\xa9\x35\x45\x8c\xfe\x04\xaa\x42\x4e\x01\x6d\xe3\xd6\x74\xdc\x5b\x73\x29\xbd\x77\x57\xfd\xdb\x32\x38\xd6\x26\x73\x62\x9b\x3c\x79\x08\x45"  # noqa: E501 Line too long
@@ -87,11 +87,7 @@ def generate_certificates(vendor_id=0xFFF1, product_id=0x8000, device_type=22, p
     subject_key_identifier = (
         b"\x62\xfa\x82\x33\x59\xac\xfa\xa9\x96\x3e\x1c\xfa\x14\x0a\xdd\xf5\x04\xf3\x71\x60"
     )
-    signature = private_key.sign_deterministic(
-        declaration,
-        hashfunc=hashlib.sha256,
-        sigencode=ecdsa.util.sigencode_der_canonize,
-    )
+    signature = crypto.Sign_as_der(private_key, declaration)
 
     certification_declaration = []
     # version
@@ -133,9 +129,7 @@ def generate_certificates(vendor_id=0xFFF1, product_id=0x8000, device_type=22, p
 
 
 def generate_dac(vendor_id, product_id, product_name, random_source) -> tuple[bytes, bytes]:  # noqa: PLR0914 Too many locals
-    dac_key = ecdsa.keys.SigningKey.generate(
-        curve=ecdsa.NIST256p, hashfunc=hashlib.sha256, entropy=random_source.urandom
-    )
+    dac_key = crypto.GenerateKeyPair(random_source.urandom)
 
     version = der.encode_constructed(0, der.encode_integer(2))
     serial_number = der.encode_integer(1)
@@ -194,11 +188,7 @@ def generate_dac(vendor_id, product_id, product_name, random_source) -> tuple[by
     )
 
     pai_key = ecdsa.keys.SigningKey.from_der(PAI_KEY_DER, hashfunc=hashlib.sha256)
-    signature = pai_key.sign_deterministic(
-        certificate,
-        hashfunc=hashlib.sha256,
-        sigencode=ecdsa.util.sigencode_der_canonize,
-    )
+    signature = crypto.Sign_as_der(pai_key, certificate)
 
     dac_cert = der.encode_sequence(
         certificate, signature_algorithm, der.encode_bitstring(signature, unused=0)

circuitmatter/clusters/measurement/temperature_measurement.py

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: Copyright (c) 2024 Ludovic BOUÉ
+#
+# SPDX-License-Identifier: MIT
+
 from circuitmatter import data_model
 
 

circuitmatter/crypto.py

@@ -2,7 +2,15 @@
 #
 # SPDX-License-Identifier: MIT
 
-import enum
+try:
+    import enum
+except ImportError:
+
+    class Enum:
+        class IntEnum:
+            pass
+
+
 import hashlib
 import hmac
 import struct
@@ -122,6 +130,25 @@ class MatterCertificate(tlv.Structure):
     signature = tlv.OctetStringMember(11, GROUP_SIZE_BYTES * 2)
 
 
+def DRBG_seed(seed):
+    random.seed(seed)
+
+
+def DRBG_bytes(byte_len: int) -> bytes:
+    """Matter spec DRBG() specifies length in bits."""
+    return random.randbytes(n)
+
+
+def DRBG_32() -> int:
+    """Return a 32-bit random unsigned int."""
+    return random.randrange(0, 0xFFFFFFFF)
+
+
+def TRNG_bytes(byte_len: int) -> bytes:
+    """Matter spec TRNG() specifies length in bits."""
+    return os.urandom(byte_len)
+
+
 def Hash(*message) -> bytes:
     h = hashlib.sha256()
     for m in message:
@@ -135,6 +162,24 @@ def HMAC(key, message) -> bytes:
     return m.digest()
 
 
+def GenerateKeyPair(random_source):
+    return ecdsa.keys.SigningKey.generate(
+        curve=ecdsa.NIST256p, hashfunc=hashlib.sha256, entropy=random_source
+    )
+
+
+def Sign_as_der(private_key, message):
+    return private_key.sign_deterministic(
+        message, hashfunc=hashlib.sha256, sigencode=ecdsa.util.sigencode_der_canonize
+    )
+
+
+def Sign_as_string(private_key, message):
+    return private_key.sign_deterministic(
+        message, hashfunc=hashlib.sha256, sigencode=ecdsa.util.sigencode_string
+    )
+
+
 def HKDF_Extract(salt, input_key) -> bytes:
     return HMAC(salt, input_key)
 

circuitmatter/device_types/sensor/temperature_sensor.py

@@ -1,10 +1,15 @@
+# SPDX-FileCopyrightText: Copyright (c) 2024 Ludovic BOUÉ
+#
+# SPDX-License-Identifier: MIT
+
+import random
+
 from circuitmatter.clusters.general.identify import Identify
 from circuitmatter.clusters.measurement.temperature_measurement import (
     TemperatureMeasurement,
 )
-from .. import simple_device
 
-import random
+from .. import simple_device
 
 
 class TemperatureSensor(simple_device.SimpleDevice):
@@ -20,6 +25,4 @@ def __init__(self, name):
         self._temp = TemperatureMeasurement()
         self.servers.append(self._temp)
 
-        self._temp.MeasuredValue = random.randint(
-            1500, 2500
-        )  # Random temp between 15°C and 25°C
+        self._temp.MeasuredValue = random.randint(1500, 2500)  # Random temp between 15°C and 25°C

circuitmatter/session.py

@@ -608,9 +608,7 @@ def reply_to_sigma1(self, exchange, sigma1):  # noqa: PLR0915, PLR0914 Too many
             session_context.session_active_threshold = (
                 sigma1.initiatorSessionParams.session_active_threshold / 1000
             )
-        ephemeral_key_pair = ecdsa.keys.SigningKey.generate(
-            curve=ecdsa.NIST256p, hashfunc=hashlib.sha256, entropy=self.random.urandom
-        )
+        ephemeral_key_pair = crypto.GenerateKeyPair(self.random.urandom)
 
         ephemeral_public_key = ephemeral_key_pair.verifying_key.to_string(encoding="uncompressed")
 
@@ -632,10 +630,8 @@ def reply_to_sigma1(self, exchange, sigma1):  # noqa: PLR0915, PLR0914 Too many
 
         tbsdata = tbsdata.encode()
 
-        tbedata.signature = self.node_credentials.noc_keys[matching_noc].sign_deterministic(
-            tbsdata,
-            hashfunc=hashlib.sha256,
-            sigencode=ecdsa.util.sigencode_string,
+        tbedata.signature = crypto.Sign_as_string(
+            self.node_credentials.noc_keys[matching_noc], tbsdata
         )
         tbedata.resumptionID = session_context.resumption_id