Output descriptors module

1 files changed, 101 insertions, 0 deletions

diff --git a/src/script/descriptor.h b/src/script/descriptor.h
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+// Copyright (c) 2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_SCRIPT_DESCRIPTOR_H
+#define BITCOIN_SCRIPT_DESCRIPTOR_H
+
+#include <script/script.h>
+#include <script/sign.h>
+
+#include <vector>
+
+// Descriptors are strings that describe a set of scriptPubKeys, together with
+// all information necessary to solve them. By combining all information into
+// one, they avoid the need to separately import keys and scripts.
+//
+// Descriptors may be ranged, which occurs when the public keys inside are
+// specified in the form of HD chains (xpubs).
+//
+// Descriptors always represent public information - public keys and scripts -
+// but in cases where private keys need to be conveyed along with a descriptor,
+// they can be included inside by changing public keys to private keys (WIF
+// format), and changing xpubs by xprvs.
+//
+// 1. Examples
+//
+// A P2PK descriptor with a fixed public key:
+// - pk(0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798)
+//
+// A P2SH-P2WSH-P2PKH descriptor with a fixed public key:
+// - sh(wsh(pkh(02e493dbf1c10d80f3581e4904930b1404cc6c13900ee0758474fa94abe8c4cd13)))
+//
+// A bare 1-of-2 multisig descriptor:
+// - multi(1,022f8bde4d1a07209355b4a7250a5c5128e88b84bddc619ab7cba8d569b240efe4,025cbdf0646e5db4eaa398f365f2ea7a0e3d419b7e0330e39ce92bddedcac4f9bc)
+//
+// A chain of P2PKH outputs (this needs the corresponding private key to derive):
+// - pkh(xpub68Gmy5EdvgibQVfPdqkBBCHxA5htiqg55crXYuXoQRKfDBFA1WEjWgP6LHhwBZeNK1VTsfTFUHCdrfp1bgwQ9xv5ski8PX9rL2dZXvgGDnw/1'/2/*)
+//
+// 2. Grammar description:
+//
+// X: xpub or xprv encoded extended key
+// I: decimal encoded integer
+// H: Hex encoded byte array
+// A: Address in P2PKH, P2SH, or Bech32 encoding
+//
+// S (Scripts):
+// * pk(P): Pay-to-pubkey (P2PK) output for public key P.
+// * pkh(P): Pay-to-pubkey-hash (P2PKH) output for public key P.
+// * wpkh(P): Pay-to-witness-pubkey-hash (P2WPKH) output for public key P.
+// * sh(S): Pay-to-script-hash (P2SH) output for script S
+// * wsh(S): Pay-to-witness-script-hash (P2WSH) output for script S
+// * combo(P): combination of P2PK, P2PKH, P2WPKH, and P2SH-P2WPKH for public key P.
+// * multi(I,L): k-of-n multisig for given public keys
+// * addr(A): Output to address
+// * raw(H): scriptPubKey with raw bytes
+//
+// P (Public keys):
+// * H: fixed public key (or WIF-encoded private key)
+// * E: extended public key
+// * E/*: (ranged) all unhardened direct children of an extended public key
+// * E/*': (ranged) all hardened direct children of an extended public key
+//
+// L (Comma-separated lists of public keys):
+// * P
+// * L,P
+//
+// E (Extended public keys):
+// * X
+// * E/I: unhardened child
+// * E/I': hardened child
+//
+// The top level is S.
+
+/** Interface for parsed descriptor objects. */
+struct Descriptor {
+    virtual ~Descriptor() = default;
+
+    /** Whether the expansion of this descriptor depends on the position. */
+    virtual bool IsRange() const = 0;
+
+    /** Convert the descriptor back to a string, undoing parsing. */
+    virtual std::string ToString() const = 0;
+
+    /** Convert the descriptor to a private string. This fails if the provided provider does not have the relevant private keys. */
+    virtual bool ToPrivateString(const SigningProvider& provider, std::string& out) const = 0;
+
+    /** Expand a descriptor at a specified position.
+     *
+     * pos: the position at which to expand the descriptor. If IsRange() is false, this is ignored.
+     * provider: the provider to query for private keys in case of hardened derivation.
+     * output_script: the expanded scriptPubKeys will be put here.
+     * out: scripts and public keys necessary for solving the expanded scriptPubKeys will be put here (may be equal to provider).
+     */
+    virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0;
+};
+
+/** Parse a descriptor string. Included private keys are put in out. Returns nullptr if parsing fails. */
+std::unique_ptr<Descriptor> Parse(const std::string& descriptor, FlatSigningProvider& out);
+
+#endif // BITCOIN_SCRIPT_DESCRIPTOR_H
+