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bitcoin/script: support for creating p2sh-p2wpkh.

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We want this because P2SH is something we can tell bitcoind to pay to;
we can't (yet?) do that with "raw" P2WPKH.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2016-04-12 13:07:04 +09:30
parent f7d86da1b5
commit d9c4960f33
2 changed files with 74 additions and 7 deletions
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71
bitcoin/script.c
View file

@ -3,6 +3,7 @@
#include "pubkey.h"
#include "script.h"
#include "signature.h"
#include "tx.h"
#include <assert.h>
#include <ccan/crypto/ripemd160/ripemd160.h>
#include <ccan/crypto/sha256/sha256.h>
@ -47,6 +48,15 @@
#define OP_CHECKLOCKTIMEVERIFY 0x61
#endif
/* Bitcoin's OP_HASH160 is RIPEMD(SHA256()) */
static void hash160(struct ripemd160 *redeemhash, const void *mem, size_t len)
{
struct sha256 h;
sha256(&h, mem, len);
ripemd160(redeemhash, h.u.u8, sizeof(h));
}
static void add(u8 **scriptp, const void *mem, size_t len)
{
size_t oldlen = tal_count(*scriptp);
@ -105,17 +115,30 @@ static void add_push_key(u8 **scriptp, const struct pubkey *key)
add_push_bytes(scriptp, key->der, sizeof(key->der));
}
static void add_push_sig(u8 **scriptp, const struct bitcoin_signature *sig)
static u8 *stack_key(const tal_t *ctx, const struct pubkey *key)
{
return tal_dup_arr(ctx, u8, key->der, sizeof(key->der), 0);
}
/* Bitcoin wants DER encoding. */
static u8 *stack_sig(const tal_t *ctx, const struct bitcoin_signature *sig)
{
/* Bitcoin wants DER encoding. */
u8 der[73];
/* FIXME: Use global! */
secp256k1_context *secpctx = secp256k1_context_create(0);
size_t len = signature_to_der(secpctx, der, &sig->sig);
secp256k1_context_destroy(secpctx);
/* Append sighash type */
der[len++] = sig->stype;
add_push_bytes(scriptp, der, len);
secp256k1_context_destroy(secpctx);
return tal_dup_arr(ctx, u8, der, len, 0);
}
static void add_push_sig(u8 **scriptp, const struct bitcoin_signature *sig)
{
u8 *der = stack_sig(*scriptp, sig);
add_push_bytes(scriptp, der, tal_count(der));
tal_free(der);
}
/* FIXME: permute? */
@ -156,18 +179,52 @@ u8 *bitcoin_redeem_single(const tal_t *ctx, const struct pubkey *key)
/* Create p2sh for this redeem script. */
u8 *scriptpubkey_p2sh(const tal_t *ctx, const u8 *redeemscript)
{
struct sha256 h;
struct ripemd160 redeemhash;
u8 *script = tal_arr(ctx, u8, 0);
add_op(&script, OP_HASH160);
sha256(&h, redeemscript, tal_count(redeemscript));
ripemd160(&redeemhash, h.u.u8, sizeof(h));
hash160(&redeemhash, redeemscript, tal_count(redeemscript));
add_push_bytes(&script, redeemhash.u.u8, sizeof(redeemhash.u.u8));
add_op(&script, OP_EQUAL);
return script;
}
/* Create the redeemscript for a P2SH + P2WPKH (for signing tx) */
u8 *bitcoin_redeem_p2wpkh(const tal_t *ctx, const struct pubkey *key)
{
struct ripemd160 keyhash;
u8 *script = tal_arr(ctx, u8, 0);
/* BIP141: BIP16 redeemScript pushed in the scriptSig is exactly a
* push of a version byte plus a push of a witness program. */
add_number(&script, 0);
hash160(&keyhash, key->der, sizeof(key->der));
add_push_bytes(&script, &keyhash, sizeof(keyhash));
return script;
}
/* Create an input which spends the p2sh-p2wpkh. */
void bitcoin_witness_p2sh_p2wpkh(const tal_t *ctx,
struct bitcoin_tx_input *input,
const struct bitcoin_signature *sig,
const struct pubkey *key)
{
u8 *redeemscript = bitcoin_redeem_p2wpkh(ctx, key);
/* BIP141: The scriptSig must be exactly a push of the BIP16 redeemScript
* or validation fails. */
input->script = tal_arr(ctx, u8, 0);
add_push_bytes(&input->script, redeemscript, tal_count(redeemscript));
input->script_length = tal_count(input->script);
/* BIP141: The witness must consist of exactly 2 items (≤ 520
* bytes each). The first one a signature, and the second one
* a public key. */
input->witness = tal_arr(ctx, u8 *, 2);
input->witness[0] = stack_sig(input->witness, sig);
input->witness[1] = stack_key(input->witness, key);
}
/* Create a script for our HTLC output: sending. */
u8 *scriptpubkey_htlc_send(const tal_t *ctx,
const struct pubkey *ourkey,

10
bitcoin/script.h
View file

@ -6,6 +6,7 @@
#include <ccan/tal/tal.h>
struct bitcoin_address;
struct bitcoin_tx_input;
struct pubkey;
struct sha256;
struct rel_locktime;
@ -36,6 +37,15 @@ u8 *bitcoin_redeem_secret_or_delay(const tal_t *ctx,
/* Create an output script using p2sh for this redeem script. */
u8 *scriptpubkey_p2sh(const tal_t *ctx, const u8 *redeemscript);
/* Create the redeemscript for a P2SH + P2WPKH. */
u8 *bitcoin_redeem_p2wpkh(const tal_t *ctx, const struct pubkey *key);
/* Create a witness which spends the 2of2. */
void bitcoin_witness_p2sh_p2wpkh(const tal_t *ctx,
struct bitcoin_tx_input *input,
const struct bitcoin_signature *sig,
const struct pubkey *key);
/* Create an input script to accept pay to pubkey */
u8 *scriptsig_pay_to_pubkeyhash(const tal_t *ctx,
const struct pubkey *key,