rpc: Add getxpub command

achow101 · achow101 · commit c9af030cd60f · 2022-10-17T10:58:12.000-04:00
diff --git a/src/wallet/keyman.cpp b/src/wallet/keyman.cpp
@@ -76,6 +76,14 @@ std::optional<CExtKey> KeyManager::GetActiveHDKey() const
     return master_key;
 }
 
+std::optional<CExtPubKey> KeyManager::GetActiveHDPubKey() const
+{
+    if (!m_active_xpub.pubkey.IsValid()) {
+        return std::nullopt;
+    }
+    return m_active_xpub;
+}
+
 bool KeyManager::AddKeyInner(WalletBatch& batch, const CKey& key, const CPubKey& pubkey)
 {
     AssertLockHeld(cs_keyman);
diff --git a/src/wallet/keyman.h b/src/wallet/keyman.h
@@ -50,6 +50,7 @@ class KeyManager
     bool AddHDKey(WalletBatch& batch, const CExtKey& extkey, const CExtPubKey& extpub);
 
     std::optional<CExtKey> GetActiveHDKey() const EXCLUSIVE_LOCKS_REQUIRED(cs_keyman);
+    std::optional<CExtPubKey> GetActiveHDPubKey() const EXCLUSIVE_LOCKS_REQUIRED(cs_keyman);
     std::map<CKeyID, CKey> GetKeys() const EXCLUSIVE_LOCKS_REQUIRED(cs_keyman);
     std::optional<std::pair<CPubKey, std::vector<unsigned char>>> GetCryptedKey(const CKeyID& id) const EXCLUSIVE_LOCKS_REQUIRED(cs_keyman);
 
diff --git a/src/wallet/rpc/addresses.cpp b/src/wallet/rpc/addresses.cpp
@@ -786,4 +786,48 @@ RPCHelpMan walletdisplayaddress()
     };
 }
 #endif // ENABLE_EXTERNAL_SIGNER
+
+RPCHelpMan getxpub()
+{
+    return RPCHelpMan{"getxpub",
+                "Returns the xpub most recently used to generate descriptors for this descriptor wallet. "
+                "Not entirely useful right now as it returns the xpub of the root, and there are "
+                "hardened derivation steps involved in normal key derivation.\n",
+                {},
+                RPCResult{
+                    RPCResult::Type::OBJ, "", "",
+                    {
+                        {
+                        {RPCResult::Type::STR, "xpub", "The xpub"},
+                    }},
+                },
+                RPCExamples{
+                    HelpExampleCli("getxpub", "")
+            + HelpExampleRpc("getxpub", "")
+                },
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
+{
+    const std::shared_ptr<CWallet> pwallet = GetWalletForJSONRPCRequest(request);
+    if (!pwallet) return NullUniValue;
+
+    if (!pwallet->IsWalletFlagSet(WALLET_FLAG_DESCRIPTORS)) {
+        throw JSONRPCError(RPC_WALLET_ERROR, "getxpub is not available for non-descriptor wallets");
+    }
+
+    const KeyManager& keyman = pwallet->GetKeyManager();
+    LOCK2(pwallet->cs_wallet, keyman.cs_keyman);
+
+    std::optional<CExtPubKey> extpub = keyman.GetActiveHDPubKey();
+    if (extpub == std::nullopt) {
+        throw JSONRPCError(RPC_WALLET_ERROR, "This wallet does not have an active xpub");
+    }
+    std::string xpub = EncodeExtPubKey(*extpub);
+
+    UniValue obj(UniValue::VOBJ);
+    obj.pushKV("xpub", xpub);
+
+    return obj;
+},
+    };
+}
 } // namespace wallet
diff --git a/src/wallet/rpc/wallet.cpp b/src/wallet/rpc/wallet.cpp
@@ -768,6 +768,7 @@ RPCHelpMan listlabels();
 #ifdef ENABLE_EXTERNAL_SIGNER
 RPCHelpMan walletdisplayaddress();
 #endif // ENABLE_EXTERNAL_SIGNER
+RPCHelpMan getxpub();
 
 // backup
 RPCHelpMan dumpprivkey();
@@ -852,6 +853,7 @@ Span<const CRPCCommand> GetWalletRPCCommands()
         {"wallet", &getunconfirmedbalance},
         {"wallet", &getbalances},
         {"wallet", &getwalletinfo},
+        {"wallet", &getxpub},
         {"wallet", &importaddress},
         {"wallet", &importdescriptors},
         {"wallet", &importmulti},

Original file line number	Diff line number	Diff line change
`@@ -76,6 +76,14 @@ std::optional<CExtKey> KeyManager::GetActiveHDKey() const`
`76`	`76`	`return master_key;`
`77`	`77`	`}`
`78`	`78`
	`79`	`+std::optional<CExtPubKey> KeyManager::GetActiveHDPubKey() const`
	`80`	`+{`
	`81`	`+ if (!m_active_xpub.pubkey.IsValid()) {`
	`82`	`+ return std::nullopt;`
	`83`	`+ }`
	`84`	`+ return m_active_xpub;`
	`85`	`+}`
	`86`	`+`
`79`	`87`	`bool KeyManager::AddKeyInner(WalletBatch& batch, const CKey& key, const CPubKey& pubkey)`
`80`	`88`	`{`
`81`	`89`	`AssertLockHeld(cs_keyman);`