Signature NOT fix, bad attempt

protocol_prototype/IcingProtocol.drawio

@@ -1,4 +1,4 @@
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+<mxfile host="app.diagrams.net" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36" version="26.1.3" pages="2">
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       <root>
@@ -260,7 +260,7 @@
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   </diagram>
   <diagram id="4Sb7mgJDpsadGym-U4wz" name="Echanges">
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+    <mxGraphModel dx="1434" dy="793" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="850" pageHeight="1100" math="0" shadow="0">
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@@ -414,7 +414,7 @@
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+        <mxCell id="pP7SjZfcCiBg3d1TCkzP-63" value="= 295&lt;span style=&quot;background-color: transparent; color: light-dark(rgb(0, 0, 0), rgb(255, 255, 255));&quot;&gt;b (+1)&lt;/span&gt;" style="text;html=1;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" parent="1" vertex="1">
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protocol_prototype/crypto_utils.py

@@ -1,11 +1,8 @@
 import os
-from cryptography.hazmat.primitives import hashes
-from cryptography.hazmat.primitives.asymmetric import ec
-from cryptography.hazmat.primitives.asymmetric.ec import ECDH
-from cryptography.hazmat.primitives import serialization
-from cryptography.hazmat.primitives.asymmetric import utils
 from cryptography.exceptions import InvalidSignature
-
+from cryptography.hazmat.primitives import hashes, serialization
+from cryptography.hazmat.primitives.asymmetric import ec, utils
+from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature, encode_dss_signature
 
 def generate_identity_keys():
     """
@@ -79,3 +76,26 @@ def compute_ecdh_shared_key(private_key, peer_pubkey_bytes: bytes) -> bytes:
     peer_public_key = peer_public_numbers.public_key()
     shared_key = private_key.exchange(ec.ECDH(), peer_public_key)
     return shared_key
+
+
+def der_to_raw(der_sig: bytes) -> bytes:
+    """
+    Convert a DER-encoded ECDSA signature to a raw 64-byte signature (r||s),
+    where each component is padded to 32 bytes.
+    """
+    r, s = decode_dss_signature(der_sig)
+    r_bytes = r.to_bytes(32, byteorder='big')
+    s_bytes = s.to_bytes(32, byteorder='big')
+    return r_bytes + s_bytes
+
+
+def raw_signature_to_der(raw_sig: bytes) -> bytes:
+    """
+    Convert a raw signature (64 bytes, concatenated r||s) to DER-encoded signature.
+    """
+    if len(raw_sig) != 64:
+        raise ValueError("Raw signature must be 64 bytes (r||s).")
+    from cryptography.hazmat.primitives.asymmetric.utils import encode_dss_signature
+    r = int.from_bytes(raw_sig[:32], 'big')
+    s = int.from_bytes(raw_sig[32:], 'big')
+    return encode_dss_signature(r, s)

protocol_prototype/protocol.py

@@ -2,6 +2,7 @@ import random
 import time
 import threading
 from typing import List, Dict, Any
+from crypto_utils import raw_signature_to_der
 
 from crypto_utils import (
     generate_identity_keys,
@@ -306,9 +307,8 @@ class IcingProtocol:
 
     def generate_ecdhe(self, index: int):
         """
-        Formerly 'respond_to_handshake' - this verifies the inbound ephemeral signature
+        Formerly 'respond_to_handshake'. Verifies ephemeral signature, computes ECDH,
-        and computes the ECDH shared secret, storing it in self.shared_secret.
+        updates pfs_history, and stores shared_secret. Does NOT send a handshake back.
-        It does NOT send a handshake back.
         """
         if index < 0 or index >= len(self.inbound_messages):
             print(f"{RED}[ERROR]{RESET} Invalid index {index}.")
@@ -318,26 +318,36 @@ class IcingProtocol:
             print(f"{RED}[ERROR]{RESET} inbound_messages[{index}] is not a HANDSHAKE.")
             return
 
-        ephemeral_pub = msg["parsed"]["ephemeral_pub"]
+        # Parse fields
-        ephemeral_sig = msg["parsed"]["ephemeral_sig"]
+        # (timestamp, ephemeral_pub, ephemeral_sig, pfs_hash) = ...
+        (ts32, ephemeral_pub, ephemeral_sig, pfs_val) = msg["parsed"]
 
-        # Verify ephemeral signature
+        # 1) Verify ephemeral signature
         if not self.peer_identity_pubkey_obj:
-            print(f"{RED}[ERROR]{RESET} Peer identity not set, cannot verify ephemeral signature.")
+            print(f"{RED}[ERROR]{RESET} Peer identity not set.")
             return
-        ok = verify_signature(self.peer_identity_pubkey_obj, ephemeral_sig, ephemeral_pub)
+        # ephemeral_sig is raw r||s
+        sig_der = raw_signature_to_der(ephemeral_sig)
+        ok = verify_signature(self.peer_identity_pubkey_obj, sig_der, ephemeral_pub)
         if not ok:
-            print(f"{RED}[ERROR]{RESET} Ephemeral signature is invalid.")
+            print(f"{RED}[ERROR]{RESET} Ephemeral signature invalid.")
             return
-        print(f"{GREEN}[OK]{RESET} Ephemeral signature verified successfully.")
+        print(f"{GREEN}[OK]{RESET} Ephemeral signature verified.")
 
-        # If we have ephemeral_privkey, compute ECDH shared key
+        # 2) ECDH
-        if self.ephemeral_privkey:
+        if not self.ephemeral_privkey:
-            shared = compute_ecdh_shared_key(self.ephemeral_privkey, ephemeral_pub)
+            print(f"{YELLOW}[WARN]{RESET} No ephemeral_privkey. Cannot compute shared secret.")
-            self.shared_secret = shared.hex()
+            return
-            print(f"{GREEN}[OK]{RESET} Derived ECDH shared key = {self.shared_secret}")
+        shared = compute_ecdh_shared_key(self.ephemeral_privkey, ephemeral_pub)
-        else:
+        self.shared_secret = shared.hex()
-            print(f"{YELLOW}[WARN]{RESET} No ephemeral_privkey available, cannot compute ECDH shared key.")
+        print(f"{GREEN}[OK]{RESET} Computed ECDH shared key = {self.shared_secret}")
+
+        # 3) Update pfs_history
+        # If we have an entry, increment session_number, store new secret
+        # If none, create session_number=1, store new secret
+        old_session, _ = self.pfs_history.get(self.peer_identity_pubkey_bytes, (-1, ""))
+        new_session = 1 if old_session < 0 else old_session + 1
+        self.pfs_history[self.peer_identity_pubkey_bytes] = (new_session, self.shared_secret)
 
     # -------------------------------------------------------------------------
     # Utility