core/tools: make keyctl remote signing more resilient

core/tools/headertool.py

@@ -64,14 +64,15 @@ def process_remote_signers(fw, addrs: List[str]) -> Tuple[int, List[bytes]]:
     digest = fw.digest()
     name = fw.NAME
 
+    def mkproxy(addr):
+        return Pyro4.Proxy(f"PYRO:keyctl@{addr}:{PORT}")
+
     sigmask = 0
-    proxies = []
     pks, Rs = [], []
     for addr in addrs:
         click.echo(f"Connecting to {addr}...")
-        proxy = Pyro4.Proxy(f"PYRO:keyctl@{addr}:{PORT}")
-        proxies.append((addr, proxy))
-        pk, R = proxy.get_commit(name, digest)
+        with mkproxy(addr) as proxy:
+            pk, R = proxy.get_commit(name, digest)
         if pk not in fw.public_keys:
             raise click.ClickException(
                 f"Signer at {addr} commits with unknown public key {pk.hex()}"
@@ -88,14 +89,16 @@ def process_remote_signers(fw, addrs: List[str]) -> Tuple[int, List[bytes]]:
 
     # collect signatures
     sigs = []
-    for addr, proxy in proxies:
+    for addr in addrs:
         click.echo(f"Waiting for {addr} to sign... ", nl=False)
-        sig = proxy.get_signature(name, digest, global_R, global_pk)
+        with mkproxy(addr) as proxy:
+            sig = proxy.get_signature(name, digest, global_R, global_pk)
         sigs.append(sig)
         click.echo("OK")
 
-    for _, proxy in proxies:
-        proxy.finish()
+    for addr in addrs:
+        with mkproxy(addr) as proxy:
+            proxy.finish()
 
     # compute global signature
     return sigmask, cosi.combine_sig(global_R, sigs)

core/tools/keyctl-proxy

@@ -75,6 +75,8 @@ class KeyctlProxy:
         self.address_n = parse_path(PATH.format(image_type.BIP32_INDEX))
         self.digest = digest
         self.commit = commit
+        self.signature = None
+        self.global_params = None
 
     def _check_name_digest(self, name, digest):
         if name != self.name or digest != self.digest:
@@ -87,21 +89,29 @@ class KeyctlProxy:
         click.echo("Sending commitment!")
         return self.commit
 
-    def get_signature(self, name, digest, global_R, global_pk):
-        self._check_name_digest(name, digest)
+    def _make_signature(self, global_R, global_pk):
         while True:
             try:
                 click.echo("\n\n\nSigning...")
                 signature = cosi.sign(
-                    TREZOR, self.address_n, digest, global_R, global_pk
+                    TREZOR, self.address_n, self.digest, global_R, global_pk
                 )
-                click.echo("Sending signature!")
                 return signature.signature
             except Exception as e:
                 click.echo(e)
                 traceback.print_exc()
                 click.echo("Trying again ...")
 
+
+    def get_signature(self, name, digest, global_R, global_pk):
+        self._check_name_digest(name, digest)
+        global_params = global_R, global_pk
+        if global_params != self.global_params:
+            self.signature = self._make_signature(global_R, global_pk)
+            self.global_params = global_params
+        click.echo("Sending signature!")
+        return self.signature
+
     @Pyro4.oneway
     def finish(self):
         click.echo("Done! \\(^o^)/")