rpc: use HexToPubKey helper for all legacy pubkey-parsing RPCs

This deduplicates code and leads to more consistent and detailed error
messages. Affected are legacy import RPCs (`importpubkey`,
`importmulti`) and other ones where solving data can be provided
(`fundrawtransaction`, `walletcreatefundedpsbt`, `send`, `sendall`).

Author: theStack

src/wallet/rpc/backup.cpp

@@ -460,12 +460,7 @@ RPCHelpMan importpubkey()
         throw JSONRPCError(RPC_WALLET_ERROR, "Wallet is currently rescanning. Abort existing rescan or wait.");
     }
 
-    if (!IsHex(request.params[0].get_str()))
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey must be a hex string");
-    std::vector<unsigned char> data(ParseHex(request.params[0].get_str()));
-    CPubKey pubKey(data);
-    if (!pubKey.IsFullyValid())
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey is not a valid public key");
+    CPubKey pubKey = HexToPubKey(request.params[0].get_str());
 
     {
         LOCK(pwallet->cs_wallet);
@@ -986,15 +981,7 @@ static UniValue ProcessImportLegacy(ImportData& import_data, std::map<CKeyID, CP
         import_data.witnessscript = std::make_unique<CScript>(parsed_witnessscript.begin(), parsed_witnessscript.end());
     }
     for (size_t i = 0; i < pubKeys.size(); ++i) {
-        const auto& str = pubKeys[i].get_str();
-        if (!IsHex(str)) {
-            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey \"" + str + "\" must be a hex string");
-        }
-        auto parsed_pubkey = ParseHex(str);
-        CPubKey pubkey(parsed_pubkey);
-        if (!pubkey.IsFullyValid()) {
-            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey \"" + str + "\" is not a valid public key");
-        }
+        CPubKey pubkey = HexToPubKey(pubKeys[i].get_str());
         pubkey_map.emplace(pubkey.GetID(), pubkey);
         ordered_pubkeys.push_back(pubkey.GetID());
     }

src/wallet/rpc/spend.cpp

@@ -627,15 +627,7 @@ CreatedTransactionResult FundTransaction(CWallet& wallet, const CMutableTransact
         const UniValue solving_data = options["solving_data"].get_obj();
         if (solving_data.exists("pubkeys")) {
             for (const UniValue& pk_univ : solving_data["pubkeys"].get_array().getValues()) {
-                const std::string& pk_str = pk_univ.get_str();
-                if (!IsHex(pk_str)) {
-                    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("'%s' is not hex", pk_str));
-                }
-                const std::vector<unsigned char> data(ParseHex(pk_str));
-                const CPubKey pubkey(data.begin(), data.end());
-                if (!pubkey.IsFullyValid()) {
-                    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("'%s' is not a valid public key", pk_str));
-                }
+                const CPubKey pubkey = HexToPubKey(pk_univ.get_str());
                 coinControl.m_external_provider.pubkeys.emplace(pubkey.GetID(), pubkey);
                 // Add witness script for pubkeys
                 const CScript wit_script = GetScriptForDestination(WitnessV0KeyHash(pubkey));

test/functional/wallet_basic.py

@@ -459,10 +459,11 @@ def run_test(self):
             assert_raises_rpc_error(-5, "Invalid Bitcoin address or script", self.nodes[0].importaddress, "invalid")
 
             # This will raise an exception for attempting to import a pubkey that isn't in hex
-            assert_raises_rpc_error(-5, "Pubkey must be a hex string", self.nodes[0].importpubkey, "not hex")
+            assert_raises_rpc_error(-5, 'Pubkey "not hex" must be a hex string', self.nodes[0].importpubkey, "not hex")
 
-            # This will raise an exception for importing an invalid pubkey
-            assert_raises_rpc_error(-5, "Pubkey is not a valid public key", self.nodes[0].importpubkey, "5361746f736869204e616b616d6f746f")
+            # This will raise an exception for importing a pubkey with invalid length
+            too_short_pubkey = "5361746f736869204e616b616d6f746f"
+            assert_raises_rpc_error(-5, f'Pubkey "{too_short_pubkey}" must have a length of either 33 or 65 bytes', self.nodes[0].importpubkey, too_short_pubkey)
 
             # Bech32m addresses cannot be imported into a legacy wallet
             assert_raises_rpc_error(-5, "Bech32m addresses cannot be imported into legacy wallets", self.nodes[0].importaddress, "bcrt1p0xlxvlhemja6c4dqv22uapctqupfhlxm9h8z3k2e72q4k9hcz7vqc8gma6")

test/functional/wallet_fundrawtransaction.py

@@ -1055,8 +1055,8 @@ def test_external_inputs(self):
         assert_raises_rpc_error(-4, "Not solvable pre-selected input COutPoint(%s, %s)" % (ext_utxo["txid"][0:10], ext_utxo["vout"]), wallet.fundrawtransaction, raw_tx)
 
         # Error conditions
-        assert_raises_rpc_error(-5, "'not a pubkey' is not hex", wallet.fundrawtransaction, raw_tx, solving_data={"pubkeys":["not a pubkey"]})
-        assert_raises_rpc_error(-5, "'01234567890a0b0c0d0e0f' is not a valid public key", wallet.fundrawtransaction, raw_tx, solving_data={"pubkeys":["01234567890a0b0c0d0e0f"]})
+        assert_raises_rpc_error(-5, 'Pubkey "not a pubkey" must be a hex string', wallet.fundrawtransaction, raw_tx, solving_data={"pubkeys":["not a pubkey"]})
+        assert_raises_rpc_error(-5, 'Pubkey "01234567890a0b0c0d0e0f" must have a length of either 33 or 65 bytes', wallet.fundrawtransaction, raw_tx, solving_data={"pubkeys":["01234567890a0b0c0d0e0f"]})
         assert_raises_rpc_error(-5, "'not a script' is not hex", wallet.fundrawtransaction, raw_tx, solving_data={"scripts":["not a script"]})
         assert_raises_rpc_error(-8, "Unable to parse descriptor 'not a descriptor'", wallet.fundrawtransaction, raw_tx, solving_data={"descriptors":["not a descriptor"]})
         assert_raises_rpc_error(-8, "Invalid parameter, missing vout key", wallet.fundrawtransaction, raw_tx, input_weights=[{"txid": ext_utxo["txid"]}])