Add RPC methods for exporting/importing viewing keys

contrib/zcash-cli.bash-completion

@@ -82,10 +82,14 @@ _zcash_cli() {
                 COMPREPLY=( $( compgen -W "add remove" -- "$cur" ) )
                 return 0
                 ;;
-            fundrawtransaction|getblock|getblockheader|getmempoolancestors|getmempooldescendants|getrawtransaction|gettransaction|listaccounts|listreceivedbyaccount|listreceivedbyaddress|sendrawtransaction|z_importkey)
+            fundrawtransaction|getblock|getblockheader|getmempoolancestors|getmempooldescendants|getrawtransaction|gettransaction|listaccounts|listreceivedbyaccount|listreceivedbyaddress|sendrawtransaction)
                 COMPREPLY=( $( compgen -W "true false" -- "$cur" ) )
                 return 0
                 ;;
+            z_importkey|z_importviewingkey)
+                COMPREPLY=( $( compgen -W "yes no whenkeyisnew" -- "$cur" ) )
+                return 0
+                ;;
             move|setaccount)
                 _zcash_accounts
                 return 0

src/rpcclient.cpp

@@ -114,6 +114,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "z_getoperationstatus", 0},
     { "z_getoperationresult", 0},
     { "z_importkey", 2 },
+    { "z_importviewingkey", 2 },
     { "z_getpaymentdisclosure", 1},
     { "z_getpaymentdisclosure", 2}
 };

src/rpcserver.cpp

@@ -395,6 +395,8 @@ static const CRPCCommand vRPCCommands[] =
     { "wallet",             "z_listaddresses",        &z_listaddresses,        true  },
     { "wallet",             "z_exportkey",            &z_exportkey,            true  },
     { "wallet",             "z_importkey",            &z_importkey,            true  },
+    { "wallet",             "z_exportviewingkey",     &z_exportviewingkey,     true  },
+    { "wallet",             "z_importviewingkey",     &z_importviewingkey,     true  },
     { "wallet",             "z_exportwallet",         &z_exportwallet,         true  },
     { "wallet",             "z_importwallet",         &z_importwallet,         true  },
 

src/rpcserver.h

@@ -279,6 +279,8 @@ extern UniValue getblocksubsidy(const UniValue& params, bool fHelp);
 
 extern UniValue z_exportkey(const UniValue& params, bool fHelp); // in rpcdump.cpp
 extern UniValue z_importkey(const UniValue& params, bool fHelp); // in rpcdump.cpp
+extern UniValue z_exportviewingkey(const UniValue& params, bool fHelp); // in rpcdump.cpp
+extern UniValue z_importviewingkey(const UniValue& params, bool fHelp); // in rpcdump.cpp
 extern UniValue z_getnewaddress(const UniValue& params, bool fHelp); // in rpcwallet.cpp
 extern UniValue z_listaddresses(const UniValue& params, bool fHelp); // in rpcwallet.cpp
 extern UniValue z_exportwallet(const UniValue& params, bool fHelp); // in rpcdump.cpp

src/wallet/rpcdump.cpp

@@ -644,6 +644,91 @@ UniValue z_importkey(const UniValue& params, bool fHelp)
     return NullUniValue;
 }
 
+UniValue z_importviewingkey(const UniValue& params, bool fHelp)
+{
+    if (!EnsureWalletIsAvailable(fHelp))
+        return NullUniValue;
+
+    if (fHelp || params.size() < 1 || params.size() > 2)
+        throw runtime_error(
+            "z_importviewingkey \"vkey\" ( rescan startHeight )\n"
+            "\nAdds a viewing key (as returned by z_exportviewingkey) to your wallet.\n"
+            "\nArguments:\n"
+            "1. \"vkey\"             (string, required) The viewing key (see z_exportviewingkey)\n"
+            "2. rescan             (string, optional, default=\"whenkeyisnew\") Rescan the wallet for transactions - can be \"yes\", \"no\" or \"whenkeyisnew\"\n"
+            "3. startHeight        (numeric, optional, default=0) Block height to start rescan from\n"
+            "\nNote: This call can take minutes to complete if rescan is true.\n"
+            "\nExamples:\n"
+            "\nImport a viewing key\n"
+            + HelpExampleCli("z_importviewingkey", "\"vkey\"") +
+            "\nImport the viewing key without rescan\n"
+            + HelpExampleCli("z_importviewingkey", "\"vkey\", no") +
+            "\nImport the viewing key with partial rescan\n"
+            + HelpExampleCli("z_importviewingkey", "\"vkey\" whenkeyisnew 30000") +
+            "\nRe-import the viewing key with longer partial rescan\n"
+            + HelpExampleCli("z_importviewingkey", "\"vkey\" yes 20000") +
+            "\nAs a JSON-RPC call\n"
+            + HelpExampleRpc("z_importviewingkey", "\"vkey\", \"no\"")
+        );
+
+    LOCK2(cs_main, pwalletMain->cs_wallet);
+
+    EnsureWalletIsUnlocked();
+
+    // Whether to perform rescan after import
+    bool fRescan = true;
+    bool fIgnoreExistingKey = true;
+    if (params.size() > 1) {
+        auto rescan = params[1].get_str();
+        if (rescan.compare("whenkeyisnew") != 0) {
+            fIgnoreExistingKey = false;
+            if (rescan.compare("no") == 0) {
+                fRescan = false;
+            } else if (rescan.compare("yes") != 0) {
+                throw JSONRPCError(
+                    RPC_INVALID_PARAMETER,
+                    "rescan must be \"yes\", \"no\" or \"whenkeyisnew\"");
+            }
+        }
+    }
+
+    // Height to rescan from
+    int nRescanHeight = 0;
+    if (params.size() > 2)
+        nRescanHeight = params[2].get_int();
+    if (nRescanHeight < 0 || nRescanHeight > chainActive.Height()) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "Block height out of range");
+    }
+
+    string strVKey = params[0].get_str();
+    CZCViewingKey viewingkey(strVKey);
+    auto vkey = viewingkey.Get();
+    auto addr = vkey.address();
+
+    {
+        if (pwalletMain->HaveSpendingKey(addr))
+            throw JSONRPCError(RPC_WALLET_ERROR, "The wallet already contains the private key for this viewing key");
+
+        // Don't throw error in case a viewing key is already there
+        if (pwalletMain->HaveViewingKey(addr)) {
+            if (fIgnoreExistingKey) {
+                return NullUniValue;
+            }
+        } else {
+            pwalletMain->MarkDirty();
+
+            if (!pwalletMain->AddViewingKey(vkey))
+                throw JSONRPCError(RPC_WALLET_ERROR, "Error adding viewing key to wallet");
+        }
+
+        // We want to scan for transactions and notes
+        if (fRescan) {
+            pwalletMain->ScanForWalletTransactions(chainActive[nRescanHeight], true);
+        }
+    }
+
+    return NullUniValue;
+}
 
 UniValue z_exportkey(const UniValue& params, bool fHelp)
 {
@@ -682,3 +767,43 @@ UniValue z_exportkey(const UniValue& params, bool fHelp)
     return spendingkey.ToString();
 }
 
+UniValue z_exportviewingkey(const UniValue& params, bool fHelp)
+{
+    if (!EnsureWalletIsAvailable(fHelp))
+        return NullUniValue;
+
+    if (fHelp || params.size() != 1)
+        throw runtime_error(
+            "z_exportviewingkey \"zaddr\"\n"
+            "\nReveals the viewing key corresponding to 'zaddr'.\n"
+            "Then the z_importviewingkey can be used with this output\n"
+            "\nArguments:\n"
+            "1. \"zaddr\"   (string, required) The zaddr for the viewing key\n"
+            "\nResult:\n"
+            "\"vkey\"                  (string) The viewing key\n"
+            "\nExamples:\n"
+            + HelpExampleCli("z_exportviewingkey", "\"myaddress\"")
+            + HelpExampleRpc("z_exportviewingkey", "\"myaddress\"")
+        );
+
+    LOCK2(cs_main, pwalletMain->cs_wallet);
+
+    EnsureWalletIsUnlocked();
+
+    string strAddress = params[0].get_str();
+
+    CZCPaymentAddress address(strAddress);
+    auto addr = address.Get();
+
+    libzcash::ViewingKey vk;
+    if (!pwalletMain->GetViewingKey(addr, vk)) {
+        libzcash::SpendingKey k;
+        if (!pwalletMain->GetSpendingKey(addr, k)) {
+            throw JSONRPCError(RPC_WALLET_ERROR, "Wallet does not hold private key or viewing key for this zaddr");
+        }
+        vk = k.viewing_key();
+    }
+
+    CZCViewingKey viewingkey(vk);
+    return viewingkey.ToString();
+}