fix(cardano): add input validation

common/tests/fixtures/cardano/sign_tx.failed.json

@@ -4,6 +4,39 @@
     "passphrase": ""
   },
   "tests": [
+    {
+      "description": "Input prev hash has incorrect length",
+      "parameters": {
+        "protocol_magic": 764824073,
+        "network_id": 1,
+        "fee": 42,
+        "ttl": 10,
+        "certificates": [],
+        "withdrawals": [],
+        "auxiliary_data": null,
+        "inputs": [
+          {
+            "path": "m/1852'/1815'/0'/0/0",
+            "prev_hash": "3b40265111d8bb3c3c608d95b3a0bf83461ace32d79336579a1939b3",
+            "prev_index": 0
+          }
+        ],
+        "outputs": [
+          {
+            "address": "Ae2tdPwUPEZCanmBz5g2GEwFqKTKpNJcGYPKfDxoNeKZ8bRHr8366kseiK2",
+            "amount": "3003112"
+          }
+        ],
+        "mint": [],
+        "script_data_hash": null,
+        "signing_mode": "ORDINARY_TRANSACTION",
+        "additional_witness_requests": [],
+        "include_network_id": false
+      },
+      "result": {
+        "error_message": "Invalid input"
+      }
+    },
     {
       "description": "Output address is a valid CBOR but invalid Cardano address",
       "parameters": {

core/src/apps/cardano/helpers/__init__.py

@@ -4,6 +4,7 @@ INVALID_ADDRESS = wire.ProcessError("Invalid address")
 INVALID_ADDRESS_PARAMETERS = wire.ProcessError("Invalid address parameters")
 NETWORK_MISMATCH = wire.ProcessError("Output address network mismatch")
 INVALID_TX_SIGNING_REQUEST = wire.ProcessError("Invalid tx signing request")
+INVALID_INPUT = wire.ProcessError("Invalid input")
 INVALID_OUTPUT = wire.ProcessError("Invalid output")
 INVALID_CERTIFICATE = wire.ProcessError("Invalid certificate")
 INVALID_WITHDRAWAL = wire.ProcessError("Invalid withdrawal")
@@ -22,6 +23,7 @@ INVALID_OUTPUT_DATUM_HASH = wire.ProcessError("Invalid output datum hash")
 INVALID_SCRIPT_DATA_HASH = wire.ProcessError("Invalid script data hash")
 
 LOVELACE_MAX_SUPPLY = 45_000_000_000 * 1_000_000
+INPUT_PREV_HASH_SIZE = 32
 ADDRESS_KEY_HASH_SIZE = 28
 SCRIPT_HASH_SIZE = 28
 OUTPUT_DATUM_HASH_SIZE = 32

core/src/apps/cardano/sign_tx.py

@@ -60,6 +60,8 @@ from .certificates import (
     validate_pool_relay,
 )
 from .helpers import (
+    INPUT_PREV_HASH_SIZE,
+    INVALID_INPUT,
     INVALID_OUTPUT,
     INVALID_OUTPUT_DATUM_HASH,
     INVALID_SCRIPT_DATA_HASH,
@@ -341,6 +343,7 @@ async def _process_inputs(
     """Read, validate and serialize the inputs."""
     for _ in range(inputs_count):
         input: CardanoTxInput = await ctx.call(CardanoTxItemAck(), CardanoTxInput)
+        _validate_input(input)
         inputs_list.append((input.prev_hash, input.prev_index))
 
 
@@ -778,6 +781,11 @@ def _validate_stake_pool_registration_tx_structure(msg: CardanoSignTxInit) -> No
         raise INVALID_STAKE_POOL_REGISTRATION_TX_STRUCTURE
 
 
+def _validate_input(input: CardanoTxInput) -> None:
+    if len(input.prev_hash) != INPUT_PREV_HASH_SIZE:
+        raise INVALID_INPUT
+
+
 def _validate_output(
     output: CardanoTxOutput,
     signing_mode: CardanoTxSigningMode,