lightningnetwork / lnd / 13236757158

package keychain

import (

        "fmt"

        "github.com/btcsuite/btcd/btcec/v2"

        "github.com/btcsuite/btcd/btcec/v2/ecdsa"

        "github.com/btcsuite/btcd/btcec/v2/schnorr"

)

const (

        // KeyDerivationVersionLegacy is the previous version of the key

        // derivation schema defined below. We use a version as this means that

        // we'll be able to accept new seed in the future and be able to discern

        // if the software is compatible with the version of the seed.

        KeyDerivationVersionLegacy = 0

        // KeyDerivationVersionTaproot is the most recent version of the key

        // derivation scheme that marks the introduction of the Taproot

        // derivation with BIP0086 support.

        KeyDerivationVersionTaproot = 1

        // CurrentKeyDerivationVersion is the current default key derivation

        // version that is used for new seeds.

        CurrentKeyDerivationVersion = KeyDerivationVersionTaproot

        // BIP0043Purpose is the "purpose" value that we'll use for the first

        // version or our key derivation scheme. All keys are expected to be

        // derived from this purpose, then the particular coin type of the

        // chain where the keys are to be used.  Slightly adhering to BIP0043

        // allows us to not deviate too far from a widely used standard, and

        // also fits into existing implementations of the BIP's template.

        //

        // NOTE: BRICK SQUUUUUAD.

        BIP0043Purpose = 1017

)

// IsKnownVersion returns true if the given version is one of the known

// derivation scheme versions as defined by this package.

var (

        // MaxKeyRangeScan is the maximum number of keys that we'll attempt to

        // scan with if a caller knows the public key, but not the KeyLocator

        // and wishes to derive a private key.

        MaxKeyRangeScan = 100000

        // ErrCannotDerivePrivKey is returned when DerivePrivKey is unable to

        // derive a private key given only the public key and target key

        // family.

        ErrCannotDerivePrivKey = fmt.Errorf("unable to derive private key")

)

// KeyFamily represents a "family" of keys that will be used within various

// contracts created by lnd. These families are meant to be distinct branches

// within the HD key chain of the backing wallet. Usage of key families within

// the interface below are strict in order to promote integrability and the

// ability to restore all keys given a user master seed backup.

//

// The key derivation in this file follows the following hierarchy based on

// BIP43:

//

//   - m/1017'/coinType'/keyFamily'/0/index

type KeyFamily uint32

const (

        // KeyFamilyMultiSig are keys to be used within multi-sig scripts.

        KeyFamilyMultiSig KeyFamily = 0

        // KeyFamilyRevocationBase are keys that are used within channels to

        // create revocation basepoints that the remote party will use to

        // create revocation keys for us.

        KeyFamilyRevocationBase KeyFamily = 1

        // KeyFamilyHtlcBase are keys used within channels that will be

        // combined with per-state randomness to produce public keys that will

        // be used in HTLC scripts.

        KeyFamilyHtlcBase KeyFamily = 2

        // KeyFamilyPaymentBase are keys used within channels that will be

        // combined with per-state randomness to produce public keys that will

        // be used in scripts that pay directly to us without any delay.

        KeyFamilyPaymentBase KeyFamily = 3

        // KeyFamilyDelayBase are keys used within channels that will be

        // combined with per-state randomness to produce public keys that will

        // be used in scripts that pay to us, but require a CSV delay before we

        // can sweep the funds.

        KeyFamilyDelayBase KeyFamily = 4

        // KeyFamilyRevocationRoot is a family of keys which will be used to

        // derive the root of a revocation tree for a particular channel.

        KeyFamilyRevocationRoot KeyFamily = 5

        // KeyFamilyNodeKey is a family of keys that will be used to derive

        // keys that will be advertised on the network to represent our current

        // "identity" within the network. Peers will need our latest node key

        // in order to establish a transport session with us on the Lightning

        // p2p level (BOLT-0008).

        KeyFamilyNodeKey KeyFamily = 6

        // KeyFamilyBaseEncryption is the family of keys that will be used to

        // derive keys that we use to encrypt and decrypt any general blob data

        // like static channel backups and the TLS private key. Often used when

        // encrypting files on disk.

        KeyFamilyBaseEncryption KeyFamily = 7

        // KeyFamilyTowerSession is the family of keys that will be used to

        // derive session keys when negotiating sessions with watchtowers. The

        // session keys are limited to the lifetime of the session and are used

        // to increase privacy in the watchtower protocol.

        KeyFamilyTowerSession KeyFamily = 8

        // KeyFamilyTowerID is the family of keys used to derive the public key

        // of a watchtower. This made distinct from the node key to offer a form

        // of rudimentary whitelisting, i.e. via knowledge of the pubkey,

        // preventing others from having full access to the tower just as a

        // result of knowing the node key.

        KeyFamilyTowerID KeyFamily = 9

)

// VersionZeroKeyFamilies is a slice of all the known key families for first

// version of the key derivation schema defined in this package.

var VersionZeroKeyFamilies = []KeyFamily{

        KeyFamilyMultiSig,

        KeyFamilyRevocationBase,

        KeyFamilyHtlcBase,

        KeyFamilyPaymentBase,

        KeyFamilyDelayBase,

        KeyFamilyRevocationRoot,

        KeyFamilyNodeKey,

        KeyFamilyBaseEncryption,

        KeyFamilyTowerSession,

        KeyFamilyTowerID,

}

// KeyLocator is a two-tuple that can be used to derive *any* key that has ever

// been used under the key derivation mechanisms described in this file.

// Version 0 of our key derivation schema uses the following BIP43-like

// derivation:

//

//   - m/1017'/coinType'/keyFamily'/0/index

//

// Our purpose is 1017 (chosen arbitrary for now), and the coin type will vary

// based on which coin/chain the channels are being created on. The key family

// are actually just individual "accounts" in the nomenclature of BIP43. By

// default we assume a branch of 0 (external). Finally, the key index (which

// will vary per channel and use case) is the final element which allows us to

// deterministically derive keys.

type KeyLocator struct {

        // TODO(roasbeef): add the key scope as well??

        // Family is the family of key being identified.

        Family KeyFamily

        // Index is the precise index of the key being identified.

        Index uint32

}

// IsEmpty returns true if a KeyLocator is "empty". This may be the case where

// we learn of a key from a remote party for a contract, but don't know the

// precise details of its derivation (as we don't know the private key!).

// KeyDescriptor wraps a KeyLocator and also optionally includes a public key.

// Either the KeyLocator must be non-empty, or the public key pointer be

// non-nil. This will be used by the KeyRing interface to lookup arbitrary

// private keys, and also within the SignDescriptor struct to locate precisely

// which keys should be used for signing.

type KeyDescriptor struct {

        // KeyLocator is the internal KeyLocator of the descriptor.

        KeyLocator

        // PubKey is an optional public key that fully describes a target key.

        // If this is nil, the KeyLocator MUST NOT be empty.

        PubKey *btcec.PublicKey

}

// KeyRing is the primary interface that will be used to perform public

// derivation of various keys used within the peer-to-peer network, and also

// within any created contracts. All derivation required by the KeyRing is

// based off of public derivation, so a system with only an extended public key

// (for the particular purpose+family) can derive this set of keys.

type KeyRing interface {

        // DeriveNextKey attempts to derive the *next* key within the key

        // family (account in BIP43) specified. This method should return the

        // next external child within this branch.

        DeriveNextKey(keyFam KeyFamily) (KeyDescriptor, error)

        // DeriveKey attempts to derive an arbitrary key specified by the

        // passed KeyLocator. This may be used in several recovery scenarios,

        // or when manually rotating something like our current default node

        // key.

        DeriveKey(keyLoc KeyLocator) (KeyDescriptor, error)

}

// SecretKeyRing is a ring similar to the regular KeyRing interface, but it is

// also able to derive *private keys*. As this is a super-set of the regular

// KeyRing, we also expect the SecretKeyRing to implement the fully KeyRing

// interface. The methods in this struct may be used to extract the node key in

// order to accept inbound network connections, or to do manual signing for

// recovery purposes.

type SecretKeyRing interface {

        KeyRing

        ECDHRing

        MessageSignerRing

        // DerivePrivKey attempts to derive the private key that corresponds to

        // the passed key descriptor.  If the public key is set, then this

        // method will perform an in-order scan over the key set, with a max of

        // MaxKeyRangeScan keys. In order for this to work, the caller MUST set

        // the KeyFamily within the partially populated KeyLocator.

        DerivePrivKey(keyDesc KeyDescriptor) (*btcec.PrivateKey, error)

}

// MessageSignerRing is an interface that abstracts away basic low-level ECDSA

// signing on keys within a key ring.

type MessageSignerRing interface {

        // SignMessage signs the given message, single or double SHA256 hashing

        // it first, with the private key described in the key locator.

        SignMessage(keyLoc KeyLocator, msg []byte,

                doubleHash bool) (*ecdsa.Signature, error)

        // SignMessageCompact signs the given message, single or double SHA256

        // hashing it first, with the private key described in the key locator

        // and returns the signature in the compact, public key recoverable

        // format.

        SignMessageCompact(keyLoc KeyLocator, msg []byte,

                doubleHash bool) ([]byte, error)

        // SignMessageSchnorr signs the given message, single or double SHA256

        // hashing it first, with the private key described in the key locator

        // and the optional Taproot tweak applied to the private key.

        SignMessageSchnorr(keyLoc KeyLocator, msg []byte,

                doubleHash bool, taprootTweak []byte,

                tag []byte) (*schnorr.Signature, error)

}

// SingleKeyMessageSigner is an abstraction interface that hides the

// implementation of the low-level ECDSA signing operations by wrapping a

// single, specific private key.

type SingleKeyMessageSigner interface {

        // PubKey returns the public key of the wrapped private key.

        PubKey() *btcec.PublicKey

        // KeyLocator returns the locator that describes the wrapped private

        // key.

        KeyLocator() KeyLocator

        // SignMessage signs the given message, single or double SHA256 hashing

        // it first, with the wrapped private key.

        SignMessage(message []byte, doubleHash bool) (*ecdsa.Signature, error)

        // SignMessageCompact signs the given message, single or double SHA256

        // hashing it first, with the wrapped private key and returns the

        // signature in the compact, public key recoverable format.

        SignMessageCompact(message []byte, doubleHash bool) ([]byte, error)

}

// ECDHRing is an interface that abstracts away basic low-level ECDH shared key

// generation on keys within a key ring.

type ECDHRing interface {

        // ECDH performs a scalar multiplication (ECDH-like operation) between

        // the target key descriptor and remote public key. The output

        // returned will be the sha256 of the resulting shared point serialized

        // in compressed format. If k is our private key, and P is the public

        // key, we perform the following operation:

        //

        //  sx := k*P

        //  s := sha256(sx.SerializeCompressed())

        ECDH(keyDesc KeyDescriptor, pubKey *btcec.PublicKey) ([32]byte, error)

}

// SingleKeyECDH is an abstraction interface that hides the implementation of an

// ECDH operation by wrapping a single, specific private key.

type SingleKeyECDH interface {

        // PubKey returns the public key of the wrapped private key.

        PubKey() *btcec.PublicKey

        // ECDH performs a scalar multiplication (ECDH-like operation) between

        // the wrapped private key and remote public key. The output returned

        // will be the sha256 of the resulting shared point serialized in

        // compressed format.

        ECDH(pubKey *btcec.PublicKey) ([32]byte, error)

}

// TODO(roasbeef): extend to actually support scalar mult of key?

//  * would allow to push in initial handshake auth into interface as well