Transaction validation

abc/txvalidation.nim

@@ -0,0 +1,32 @@
+import ./txstore
+
+func checkValue(store: TxStore, transaction: Transaction): bool =
+  var valueIn, valueOut = 0.u256
+
+  for (hash, owner) in transaction.inputs:
+    for output in store[hash].outputs:
+      if output.owner == owner:
+        valueIn += output.amount
+
+  for (_, amount) in transaction.outputs:
+    valueOut += amount
+
+  valueIn == valueOut
+
+func hasValidTx*(store: TxStore, hash: TxHash): bool =
+  if hash == store.genesis:
+    return true
+
+  if not store.hasTx(hash):
+    return false
+
+  let transaction = store[hash]
+
+  if not transaction.hasValidSignature:
+    return false
+
+  for (hash, _) in transaction.inputs:
+    if not store.hasValidTx(hash):
+      return false
+
+  store.checkValue(transaction)

tests/testTxValidation.nim

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+import abc/txstore
+import abc/txvalidation
+import ./basics
+import ./alicebob
+
+suite "Transaction validation":
+
+  let alice = PublicKey.alice
+  let bob = PublicKey.bob
+  let genesis = Transaction.genesis
+  var tx1, tx2: Transaction
+
+  setup:
+    tx1 = !Transaction.init({genesis.hash: alice}, {bob: 100.u256})
+    tx2 = !Transaction.init({tx1.hash: bob}, {alice: 100.u256})
+    PrivateKey.alice.sign(tx1)
+    PrivateKey.bob.sign(tx2)
+
+  test "checks validity of transactions":
+    var store = TxStore.init(genesis)
+    store.add(tx1, tx2)
+    check store.hasValidTx(genesis.hash)
+    check store.hasValidTx(tx1.hash)
+    check store.hasValidTx(tx2.hash)
+
+  test "checks that no input is missing":
+    var store = TxStore.init(genesis)
+    store.add(tx2) # tx2 depends on tx1, which is missing
+    check not store.hasValidTx(tx2.hash)
+
+  test "checks that inputs and outputs match":
+    var store = TxStore.init(genesis)
+    var invalid1 = !Transaction.init({genesis.hash: alice}, {bob: 999.u256})
+    var invalid2 = !Transaction.init({invalid1.hash: bob}, {alice: 999.u256})
+    PrivateKey.alice.sign(invalid1)
+    PrivateKey.bob.sign(invalid2)
+    store.add(invalid1, invalid2)
+    check not store.hasValidTx(invalid1.hash)
+    check not store.hasValidTx(invalid2.hash)
+
+  test "checks that signatures match":
+    var store = TxStore.init(genesis)
+    var invalid1 = !Transaction.init({genesis.hash: alice}, {bob: 100.u256})
+    var invalid2 = !Transaction.init({invalid1.hash: bob}, {alice: 100.u256})
+    PrivateKey.bob.sign(invalid1) # invalid signature, should be signed by alice
+    PrivateKey.bob.sign(invalid2)
+    store.add(invalid1, invalid2)
+    check not store.hasValidTx(invalid1.hash)
+    check not store.hasValidTx(invalid2.hash)