Increase maximum depth of the supported taptrees on non-NanoS devices…

…; generalize corresponding test so that it adapts to the different limits

src/common/wallet.h

@@ -73,7 +73,12 @@
  MAX(MAX_WALLET_POLICY_SERIALIZED_LENGTH_V1, MAX_WALLET_POLICY_SERIALIZED_LENGTH_V2)
 
 // maximum depth of a taproot tree that we support
-#define MAX_TAPTREE_POLICY_DEPTH 4
+// (here depth 1 means only the root of the taptree)
+#ifdef TARGET_NANOS
+#define MAX_TAPTREE_POLICY_DEPTH 5
+#else
+#define MAX_TAPTREE_POLICY_DEPTH 9
+#endif
 
 typedef struct {
  uint32_t master_key_derivation[MAX_BIP32_PATH_STEPS];

src/handler/lib/check_merkle_tree_sorted.h

@@ -2,11 +2,12 @@
 
 #include "../../boilerplate/dispatcher.h"
 #include "../../common/merkle.h"
+#include "../../common/wallet.h"
 
 // this flow aborts if any element is larger than this size
-// This is enough for a PSBT with the control block of a taptree of depth 5 tapbranches
 // TODO: we might remove this limitation altogether with a more careful implementation.
-#define MAX_CHECK_MERKLE_TREE_SORTED_PREIMAGE_SIZE 162
+// Here we make sure that we have enough space for control block of a taptree of the maximum supported depth
+#define MAX_CHECK_MERKLE_TREE_SORTED_PREIMAGE_SIZE (34 + 32*(MAX_TAPTREE_POLICY_DEPTH - 1))
 
 typedef void (*merkle_tree_elements_callback_t)(struct dispatcher_context_s *,
  void *,

tests/test_e2e_tapscripts.py

@@ -236,21 +236,28 @@ def test_e2e_tapscript_multi_a_2of2(rpc, rpc_test_wallet, client: Client, specul
  rpc, rpc_test_wallet, client, speculos_globals, comm)
 
 
-def test_e2e_tapscript_depth4(rpc, rpc_test_wallet, client: Client, speculos_globals: SpeculosGlobals, comm: Union[TransportClient, SpeculosClient]):
+def test_e2e_tapscript_maxdepth(rpc, rpc_test_wallet, client: Client, speculos_globals: SpeculosGlobals, comm: Union[TransportClient, SpeculosClient], model: str):
  # A taproot tree with maximum supported depth, where the internal key is in the deepest script
 
+ MAX_TAPTREE_POLICY_DEPTH = 4 if model == "nanos" else 9
+
+ # Make the most unbalanced tree where each script is a simple pk()
+ parts = [f"pk(@{i}/**)" for i in range(1, MAX_TAPTREE_POLICY_DEPTH)]
+ descriptor_template = "tr(@0/**,{" + ',{'.join(parts) + f",pk(@{MAX_TAPTREE_POLICY_DEPTH}/**)" + "}" * (MAX_TAPTREE_POLICY_DEPTH - 1) + ")"
+
  keys_info = []
- for _ in range(4):
+ for _ in range(MAX_TAPTREE_POLICY_DEPTH):
  _, core_xpub_orig = create_new_wallet()
  keys_info.append(core_xpub_orig)
 
+ # the last (deepest) script is the only one we sign with the ledger key
  path = "499'/1'/0'"
  internal_xpub = get_internal_xpub(speculos_globals.seed, path)
  keys_info.append(f"[{speculos_globals.master_key_fingerprint.hex()}/{path}]{internal_xpub}")
 
  wallet_policy = WalletPolicy(
  name="Tapscriptception",
- descriptor_template="tr(@0/**,{pk(@1/**),{pk(@2/**),{pk(@3/**),pk(@4/**)}}})",
+ descriptor_template=descriptor_template,
  keys_info=keys_info)
 
  run_test_e2e(wallet_policy, [], rpc, rpc_test_wallet, client, speculos_globals, comm)