multi: verifySeed RPC (#1037)

fixup:

update

update

internal/rpchelp/helpdescs_en_US.go

@@ -541,14 +541,23 @@ var helpDescsEnUS = map[string]string{
 	"verifymessage-message":   "The message to verify",
 	"verifymessage--result0":  "Whether the message was signed with the private key of 'address'",
 
+	// VerifySeedCmd help.
+	"verifyseed--synopsis": "Verifes if the inputted seed derived account key is associated with the running wallet account key",
+	"verifyseed-seed":      "Seed to be checked against the running wallets",
+	"verifyseed-account":   "Used to check if a watching only wallets public key is the same as the running wallets",
+
+	// VerifySeedResult help.
+	"verifyseedresult-keyresult": "The result of comparing an inputted seed with the running wallets.  Useful to check if a watching only wallet's public key is the same as the running wallet",
+	"verifyseedresult-cointype":  "Outputs the current cointype of the running wallet",
+
 	// Version help
 	"version--synopsis":       "Returns application and API versions (semver) keyed by their names",
 	"version--result0--desc":  "Version objects keyed by the program or API name",
 	"version--result0--key":   "Program or API name",
 	"version--result0--value": "Object containing the semantic version",
 
 	// WalletLockCmd help.
-	"walletlock--synopsis": "Lock the wallet.",
+	"walletlock--synopsis": "Lock the wallet",
 
 	// WalletPassphraseCmd help.
 	"walletpassphrase--synopsis":  "Unlock the wallet.",

internal/rpchelp/methods.go

@@ -76,6 +76,7 @@ var Methods = []struct {
 	{"sweepaccount", []interface{}{(*dcrjson.SweepAccountResult)(nil)}},
 	{"validateaddress", []interface{}{(*dcrjson.ValidateAddressWalletResult)(nil)}},
 	{"verifymessage", returnsBool},
+	{"verifyseed", []interface{}{(*dcrjson.VerifySeedResult)(nil)}},
 	{"version", []interface{}{(*map[string]dcrjson.VersionResult)(nil)}},
 	{"walletlock", nil},
 	{"walletpassphrase", nil},

rpc/legacyrpc/methods.go

@@ -36,6 +36,7 @@ import (
 	"github.com/decred/dcrwallet/wallet"
 	"github.com/decred/dcrwallet/wallet/txrules"
 	"github.com/decred/dcrwallet/wallet/udb"
+	"github.com/decred/dcrwallet/walletseed"
 )
 
 // API version constants
@@ -123,6 +124,7 @@ var handlers = map[string]handler{
 	"ticketsforaddress":       {fn: ticketsForAddress},
 	"validateaddress":         {fn: validateAddress},
 	"verifymessage":           {fn: verifyMessage},
+	"verifyseed":              {fn: verifySeed},
 	"version":                 {fn: version},
 	"walletinfo":              {fn: walletInfo},
 	"walletlock":              {fn: walletLock},
@@ -3423,6 +3425,95 @@ WrongAddrKind:
 	return nil, rpcErrorf(dcrjson.ErrRPCInvalidParameter, "address must be secp256k1 P2PK or P2PKH")
 }
 
+func deriveCoinTypeKey(seed []byte, coinType uint32, params *chaincfg.Params) (*hdkeychain.ExtendedKey, error) {
+	// Create new root from the inputted seed and the current net
+	root, err := hdkeychain.NewMaster(seed[:], params)
+	if err != nil {
+		return nil, err
+	}
+
+	// BIP0032 hierarchy: m/<purpose>'/
+	// Where purpose = 44 and the ' indicates hardening with the HardenedKeyStart 0x80000000
+	purpose, err := root.Child(44 + hdkeychain.HardenedKeyStart)
+	if err != nil {
+		return nil, err
+	}
+	defer purpose.Zero()
+
+	// BIP0044 hierarchy: m/<purpose>'/<coin type>'
+	// Where coin type is either the legacy coin type, 20, or the coin type described in SLIP0044, 44. Note these parameters
+	// are only appropraite for main net.
+	coinTypePrivKey, err := purpose.Child(coinType + hdkeychain.HardenedKeyStart)
+	if err != nil {
+		return nil, err
+	}
+
+	return coinTypePrivKey, nil
+}
+
+// verifySeed checks if a user inputted seed is equivelent to the running wallets.
+// Returns a a JSON object, with the dscribed bool and coin type.
+func verifySeed(s *Server, icmd interface{}) (interface{}, error) {
+	cmd := icmd.(*dcrjson.VerifySeedCmd)
+	w, ok := s.walletLoader.LoadedWallet()
+	if !ok {
+		return nil, errUnloadedWallet
+	}
+
+	// obtain the wallet public key to check agaisnt the wallet derived seed
+	var account uint32 = 0
+	if cmd.Account != nil {
+		account = uint32(cmd.Account)
+	}
+
+	// do whats necessary to derive the key from the seed
+	c := make(chan *hdkeychain.ExtendedKey)
+	go func(seed string) {
+		coinType, err := w.CoinType()
+		if err != nil {
+			return nil, err
+		}
+
+		decodedSeed, err := walletseed.DecodeUserInput(cmd.Seed)
+		if err != nil {
+			return nil, err
+		}
+
+		coinTypePrivKey, err := deriveCoinTypeKey(decodedSeed, coinType, w.ChainParams())
+		if err != nil {
+			return nil, err
+		}
+		defer coinTypePrivKey.Zero()
+
+		// Both derivedAccountKey and walletDerivedAccountKey use the BIP044 hierachy: m/44'/<coin type>'/<account>'
+		accountKey, err := coinTypePrivKey.Child(account + hdkeychain.HardenedKeyStart)
+		if err != nil {
+			return nil, err
+		}
+		defer accountKey.Zero()
+
+		// To be matched with walletxPubKey.
+		seedxPubKey, err := accountKey.Neuter()
+		if err != nil {
+			return nil, err
+		}
+
+		c <- seedxPubKey
+	}(cmd.Seed)
+
+	walletxPubKey := w.MasterPubKey(account)
+	if err != nil {
+		return nil, err
+	}
+
+	seedxPubKey := <-c
+
+	return &dcrjson.VerifySeedResult{
+		Result:   walletxPubKey.String() == seedxPubKey.String(),
+		CoinType: coinType,
+	}, nil
+}
+
 // version handles the version command by returning the RPC API versions of the
 // wallet and, optionally, the consensus RPC server as well if it is associated
 // with the server.  The chainClient is optional, and this is simply a helper