Merge #8035: [Wallet] Add simplest BIP32/deterministic key generation implementation

afcd77e Detect -usehd mismatches when wallet.dat already exists (Jonas Schnelli)
17c0131 [Docs] Add release notes and bip update for Bip32/HD wallets (Jonas Schnelli)
c022e5b [Wallet] use constant for bip32 hardened key limit (Jonas Schnelli)
f190251 [Wallet] Add simplest BIP32/deterministic key generation implementation (Jonas Schnelli)

1 files changed, 93 insertions, 4 deletions

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 9faf21591f..723b2eceff 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -42,6 +42,7 @@ bool bSpendZeroConfChange = DEFAULT_SPEND_ZEROCONF_CHANGE;
 bool fSendFreeTransactions = DEFAULT_SEND_FREE_TRANSACTIONS;
 
 const char * DEFAULT_WALLET_DAT = "wallet.dat";
+const uint32_t BIP32_HARDENED_KEY_LIMIT = 0x80000000;
 
 /**
  * Fees smaller than this (in satoshi) are considered zero fee (for transaction creation)
@@ -91,7 +92,51 @@ CPubKey CWallet::GenerateNewKey()
     bool fCompressed = CanSupportFeature(FEATURE_COMPRPUBKEY); // default to compressed public keys if we want 0.6.0 wallets
 
     CKey secret;
-    secret.MakeNewKey(fCompressed);
+
+    // Create new metadata
+    int64_t nCreationTime = GetTime();
+    CKeyMetadata metadata(nCreationTime);
+
+    // use HD key derivation if HD was enabled during wallet creation
+    if (!hdChain.masterKeyID.IsNull()) {
+        // for now we use a fixed keypath scheme of m/0'/0'/k
+        CKey key;                      //master key seed (256bit)
+        CExtKey masterKey;             //hd master key
+        CExtKey accountKey;            //key at m/0'
+        CExtKey externalChainChildKey; //key at m/0'/0'
+        CExtKey childKey;              //key at m/0'/0'/<n>'
+
+        // try to get the master key
+        if (!GetKey(hdChain.masterKeyID, key))
+            throw std::runtime_error("CWallet::GenerateNewKey(): Master key not found");
+
+        masterKey.SetMaster(key.begin(), key.size());
+
+        // derive m/0'
+        // use hardened derivation (child keys >= 0x80000000 are hardened after bip32)
+        masterKey.Derive(accountKey, BIP32_HARDENED_KEY_LIMIT);
+
+        // derive m/0'/0'
+        accountKey.Derive(externalChainChildKey, BIP32_HARDENED_KEY_LIMIT);
+
+        // derive child key at next index, skip keys already known to the wallet
+        do
+        {
+            // always derive hardened keys
+            // childIndex | BIP32_HARDENED_KEY_LIMIT = derive childIndex in hardened child-index-range
+            // example: 1 | BIP32_HARDENED_KEY_LIMIT == 0x80000001 == 2147483649
+            externalChainChildKey.Derive(childKey, hdChain.nExternalChainCounter | BIP32_HARDENED_KEY_LIMIT);
+            // increment childkey index
+            hdChain.nExternalChainCounter++;
+        } while(HaveKey(childKey.key.GetPubKey().GetID()));
+        secret = childKey.key;
+
+        // update the chain model in the database
+        if (!CWalletDB(strWalletFile).WriteHDChain(hdChain))
+            throw std::runtime_error("CWallet::GenerateNewKey(): Writing HD chain model failed");
+    } else {
+        secret.MakeNewKey(fCompressed);
+    }
 
     // Compressed public keys were introduced in version 0.6.0
     if (fCompressed)
@@ -100,9 +145,7 @@ CPubKey CWallet::GenerateNewKey()
     CPubKey pubkey = secret.GetPubKey();
     assert(secret.VerifyPubKey(pubkey));
 
-    // Create new metadata
-    int64_t nCreationTime = GetTime();
-    mapKeyMetadata[pubkey.GetID()] = CKeyMetadata(nCreationTime);
+    mapKeyMetadata[pubkey.GetID()] = metadata;
     if (!nTimeFirstKey || nCreationTime < nTimeFirstKey)
         nTimeFirstKey = nCreationTime;
 
@@ -1121,6 +1164,37 @@ CAmount CWallet::GetChange(const CTransaction& tx) const
     return nChange;
 }
 
+bool CWallet::SetHDMasterKey(const CKey& key)
+{
+    LOCK(cs_wallet);
+
+    // store the key as normal "key"/"ckey" object
+    // in the database
+    // key metadata is not required
+    CPubKey pubkey = key.GetPubKey();
+    if (!AddKeyPubKey(key, pubkey))
+        throw std::runtime_error("CWallet::GenerateNewKey(): AddKey failed");
+
+    // store the keyid (hash160) together with
+    // the child index counter in the database
+    // as a hdchain object
+    CHDChain newHdChain;
+    newHdChain.masterKeyID = pubkey.GetID();
+    SetHDChain(newHdChain, false);
+
+    return true;
+}
+
+bool CWallet::SetHDChain(const CHDChain& chain, bool memonly)
+{
+    LOCK(cs_wallet);
+    if (!memonly && !CWalletDB(strWalletFile).WriteHDChain(chain))
+        throw runtime_error("AddHDChain(): writing chain failed");
+
+    hdChain = chain;
+    return true;
+}
+
 int64_t CWalletTx::GetTxTime() const
 {
     int64_t n = nTimeSmart;
@@ -3135,6 +3209,7 @@ std::string CWallet::GetWalletHelpString(bool showDebug)
         strUsage += HelpMessageOpt("-sendfreetransactions", strprintf(_("Send transactions as zero-fee transactions if possible (default: %u)"), DEFAULT_SEND_FREE_TRANSACTIONS));
     strUsage += HelpMessageOpt("-spendzeroconfchange", strprintf(_("Spend unconfirmed change when sending transactions (default: %u)"), DEFAULT_SPEND_ZEROCONF_CHANGE));
     strUsage += HelpMessageOpt("-txconfirmtarget=<n>", strprintf(_("If paytxfee is not set, include enough fee so transactions begin confirmation on average within n blocks (default: %u)"), DEFAULT_TX_CONFIRM_TARGET));
+    strUsage += HelpMessageOpt("-usehd", _("Use hierarchical deterministic key generation (HD) after bip32. Only has effect during wallet creation/first start") + " " + strprintf(_("(default: %u)"), DEFAULT_USE_HD_WALLET));
     strUsage += HelpMessageOpt("-upgradewallet", _("Upgrade wallet to latest format on startup"));
     strUsage += HelpMessageOpt("-wallet=<file>", _("Specify wallet file (within data directory)") + " " + strprintf(_("(default: %s)"), DEFAULT_WALLET_DAT));
     strUsage += HelpMessageOpt("-walletbroadcast", _("Make the wallet broadcast transactions") + " " + strprintf(_("(default: %u)"), DEFAULT_WALLETBROADCAST));
@@ -3222,6 +3297,13 @@ bool CWallet::InitLoadWallet()
     if (fFirstRun)
     {
         // Create new keyUser and set as default key
+        if (GetBoolArg("-usehd", DEFAULT_USE_HD_WALLET)) {
+            // generate a new master key
+            CKey key;
+            key.MakeNewKey(true);
+            if (!walletInstance->SetHDMasterKey(key))
+                throw std::runtime_error("CWallet::GenerateNewKey(): Storing master key failed");
+        }
         CPubKey newDefaultKey;
         if (walletInstance->GetKeyFromPool(newDefaultKey)) {
             walletInstance->SetDefaultKey(newDefaultKey);
@@ -3231,6 +3313,13 @@ bool CWallet::InitLoadWallet()
 
         walletInstance->SetBestChain(chainActive.GetLocator());
     }
+    else if (mapArgs.count("-usehd")) {
+        bool useHD = GetBoolArg("-usehd", DEFAULT_USE_HD_WALLET);
+        if (!walletInstance->hdChain.masterKeyID.IsNull() && !useHD)
+            return InitError(strprintf(_("Error loading %s: You can't disable HD on a already existing HD wallet"), walletFile));
+        if (walletInstance->hdChain.masterKeyID.IsNull() && useHD)
+            return InitError(strprintf(_("Error loading %s: You can't enable HD on a already existing non-HD wallet"), walletFile));
+    }
 
     LogPrintf(" wallet      %15dms\n", GetTimeMillis() - nStart);