SegWit wallet support

This introduces two command line flags (-addresstype and -changetype) which control
the type of addresses/outputs created by the GUI and RPCs. Certain RPCs allow
overriding these (`getnewaddress` and `getrawchangeaddress`). Supported types
are "legacy" (P2PKH and P2SH-multisig), "p2sh-segwit" (P2SH-P2WPKH and P2SH-P2WSH-multisig),
and "bech32" (P2WPKH and P2WSH-multisig).

A few utility functions are added to the wallet to construct different address type
and to add the necessary entries to the wallet file to be compatible with earlier
versions (see `CWallet::LearnRelatedScripts`, `GetDestinationForKey`,
`GetAllDestinationsForKey`, `CWallet::AddAndGetDestinationForScript`).

3 files changed, 22 insertions, 21 deletions

diff --git a/src/qt/addresstablemodel.cpp b/src/qt/addresstablemodel.cpp
index 1d16940acb..f238c37f63 100644
--- a/src/qt/addresstablemodel.cpp
+++ b/src/qt/addresstablemodel.cpp
@@ -384,7 +384,8 @@ QString AddressTableModel::addRow(const QString &type, const QString &label, con
                 return QString();
             }
         }
-        strAddress = EncodeDestination(newKey.GetID());
+        wallet->LearnRelatedScripts(newKey, g_address_type);
+        strAddress = EncodeDestination(GetDestinationForKey(newKey, g_address_type));
     }
     else
     {
diff --git a/src/qt/paymentserver.cpp b/src/qt/paymentserver.cpp
index 510a3783ae..48462f9b5f 100644
--- a/src/qt/paymentserver.cpp
+++ b/src/qt/paymentserver.cpp
@@ -636,27 +636,24 @@ void PaymentServer::fetchPaymentACK(CWallet* wallet, const SendCoinsRecipient& r
     // Create a new refund address, or re-use:
     QString account = tr("Refund from %1").arg(recipient.authenticatedMerchant);
     std::string strAccount = account.toStdString();
-    std::set<CTxDestination> refundAddresses = wallet->GetAccountAddresses(strAccount);
-    if (!refundAddresses.empty()) {
-        CScript s = GetScriptForDestination(*refundAddresses.begin());
+    CPubKey newKey;
+    if (wallet->GetKeyFromPool(newKey)) {
+        // BIP70 requests encode the scriptPubKey directly, so we are not restricted to address
+        // types supported by the receiver. As a result, we choose the address format we also
+        // use for change. Despite an actual payment and not change, this is a close match:
+        // it's the output type we use subject to privacy issues, but not restricted by what
+        // other software supports.
+        wallet->LearnRelatedScripts(newKey, g_change_type);
+        CTxDestination dest = GetDestinationForKey(newKey, g_change_type);
+        wallet->SetAddressBook(dest, strAccount, "refund");
+
+        CScript s = GetScriptForDestination(dest);
         payments::Output* refund_to = payment.add_refund_to();
         refund_to->set_script(&s[0], s.size());
-    }
-    else {
-        CPubKey newKey;
-        if (wallet->GetKeyFromPool(newKey)) {
-            CKeyID keyID = newKey.GetID();
-            wallet->SetAddressBook(keyID, strAccount, "refund");
-
-            CScript s = GetScriptForDestination(keyID);
-            payments::Output* refund_to = payment.add_refund_to();
-            refund_to->set_script(&s[0], s.size());
-        }
-        else {
-            // This should never happen, because sending coins should have
-            // just unlocked the wallet and refilled the keypool.
-            qWarning() << "PaymentServer::fetchPaymentACK: Error getting refund key, refund_to not set";
-        }
+    } else {
+        // This should never happen, because sending coins should have
+        // just unlocked the wallet and refilled the keypool.
+        qWarning() << "PaymentServer::fetchPaymentACK: Error getting refund key, refund_to not set";
     }
 
     int length = payment.ByteSize();
diff --git a/src/qt/test/wallettests.cpp b/src/qt/test/wallettests.cpp
index 4b7c3bd726..a270e5de59 100644
--- a/src/qt/test/wallettests.cpp
+++ b/src/qt/test/wallettests.cpp
@@ -149,6 +149,9 @@ void BumpFee(TransactionView& view, const uint256& txid, bool expectDisabled, st
 //     src/qt/test/test_bitcoin-qt -platform cocoa    # macOS
 void TestGUI()
 {
+    g_address_type = OUTPUT_TYPE_P2SH_SEGWIT;
+    g_change_type = OUTPUT_TYPE_P2SH_SEGWIT;
+
     // Set up wallet and chain with 105 blocks (5 mature blocks for spending).
     TestChain100Setup test;
     for (int i = 0; i < 5; ++i) {
@@ -161,7 +164,7 @@ void TestGUI()
     wallet.LoadWallet(firstRun);
     {
         LOCK(wallet.cs_wallet);
-        wallet.SetAddressBook(test.coinbaseKey.GetPubKey().GetID(), "", "receive");
+        wallet.SetAddressBook(GetDestinationForKey(test.coinbaseKey.GetPubKey(), g_address_type), "", "receive");
         wallet.AddKeyPubKey(test.coinbaseKey, test.coinbaseKey.GetPubKey());
     }
     {