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#include "privkey.h"
#include "pubkey.h"
#include "script.h"
#include "shadouble.h"
#include "signature.h"
#include "tx.h"
#include <assert.h>
#include <bitcoin/psbt.h>
#include <ccan/cast/cast.h>
#include <ccan/mem/mem.h>
#include <common/type_to_string.h>
#include <common/utils.h>
#include <wire/wire.h>
#undef DEBUG
#ifdef DEBUG
# include <ccan/err/err.h>
# include <stdio.h>
#define SHA_FMT \
"%02x%02x%02x%02x%02x%02x%02x%02x" \
"%02x%02x%02x%02x%02x%02x%02x%02x" \
"%02x%02x%02x%02x%02x%02x%02x%02x" \
"%02x%02x%02x%02x%02x%02x%02x%02x"
#define SHA_VALS(e) \
e[0], e[1], e[2], e[3], e[4], e[5], e[6], e[7], \
e[8], e[9], e[10], e[11], e[12], e[13], e[14], e[15], \
e[16], e[17], e[18], e[19], e[20], e[21], e[22], e[23], \
e[24], e[25], e[25], e[26], e[28], e[29], e[30], e[31]
static void dump_tx(const char *msg,
const struct bitcoin_tx *tx, size_t inputnum,
const u8 *script,
const struct pubkey *key,
const struct sha256_double *h)
{
size_t i, j;
warnx("%s tx version %u locktime %#x:",
msg, tx->wtx->version, tx->wtx->locktime);
for (i = 0; i < tx->wtx->num_inputs; i++) {
warnx("input[%zu].txid = "SHA_FMT, i,
SHA_VALS(tx->wtx->inputs[i].txhash));
warnx("input[%zu].index = %u", i, tx->wtx->inputs[i].index);
}
for (i = 0; i < tx->wtx->num_outputs; i++) {
warnx("output[%zu].amount = %llu",
i, (long long)tx->wtx->outputs[i].satoshi);
warnx("output[%zu].script = %zu",
i, tx->wtx->outputs[i].script_len);
for (j = 0; j < tx->wtx->outputs[i].script_len; j++)
fprintf(stderr, "%02x", tx->wtx->outputs[i].script[j]);
fprintf(stderr, "\n");
}
warnx("input[%zu].script = %zu", inputnum, tal_count(script));
for (i = 0; i < tal_count(script); i++)
fprintf(stderr, "%02x", script[i]);
if (key) {
fprintf(stderr, "\nPubkey: ");
for (i = 0; i < sizeof(key->pubkey); i++)
fprintf(stderr, "%02x", ((u8 *)&key->pubkey)[i]);
fprintf(stderr, "\n");
}
if (h) {
fprintf(stderr, "\nHash: ");
for (i = 0; i < sizeof(h->sha.u.u8); i++)
fprintf(stderr, "%02x", h->sha.u.u8[i]);
fprintf(stderr, "\n");
}
}
#else
static void dump_tx(const char *msg UNUSED,
const struct bitcoin_tx *tx UNUSED, size_t inputnum UNUSED,
const u8 *script UNUSED,
const struct pubkey *key UNUSED,
const struct sha256_double *h UNUSED)
{
}
#endif
/* Taken from https://github.com/bitcoin/bitcoin/blob/master/src/key.cpp */
/* Check that the sig has a low R value and will be less than 71 bytes */
static bool sig_has_low_r(const secp256k1_ecdsa_signature* sig)
{
unsigned char compact_sig[64];
secp256k1_ecdsa_signature_serialize_compact(secp256k1_ctx, compact_sig, sig);
/* In DER serialization, all values are interpreted as big-endian, signed
* integers. The highest bit in the integer indicates its signed-ness; 0 is
* positive, 1 is negative. When the value is interpreted as a negative
* integer, it must be converted to a positive value by prepending a 0x00
* byte so that the highest bit is 0. We can avoid this prepending by
* ensuring that our highest bit is always 0, and thus we must check that
* the first byte is less than 0x80. */
return compact_sig[0] < 0x80;
}
void sign_hash(const struct privkey *privkey,
const struct sha256_double *h,
secp256k1_ecdsa_signature *s)
{
bool ok;
unsigned char extra_entropy[32] = {0};
/* Grind for low R */
do {
ok = secp256k1_ecdsa_sign(secp256k1_ctx,
s,
h->sha.u.u8,
privkey->secret.data, NULL, extra_entropy);
((u32 *)extra_entropy)[0]++;
} while (!sig_has_low_r(s));
assert(ok);
}
void bitcoin_tx_hash_for_sig(const struct bitcoin_tx *tx, unsigned int in,
const u8 *script,
enum sighash_type sighash_type,
struct sha256_double *dest)
{
int ret;
u8 value[9];
u64 input_val_sats;
struct amount_sat input_amt;
int flags = WALLY_TX_FLAG_USE_WITNESS;
input_amt = psbt_input_get_amount(tx->psbt, in);
input_val_sats = input_amt.satoshis; /* Raw: type conversion */
/* Wally can allocate here, iff tx doesn't fit on stack */
tal_wally_start();
if (is_elements(chainparams)) {
ret = wally_tx_confidential_value_from_satoshi(input_val_sats, value, sizeof(value));
assert(ret == WALLY_OK);
ret = wally_tx_get_elements_signature_hash(
tx->wtx, in, script, tal_bytelen(script), value,
sizeof(value), sighash_type, flags, dest->sha.u.u8,
sizeof(*dest));
assert(ret == WALLY_OK);
} else {
ret = wally_tx_get_btc_signature_hash(
tx->wtx, in, script, tal_bytelen(script), input_val_sats,
sighash_type, flags, dest->sha.u.u8, sizeof(*dest));
assert(ret == WALLY_OK);
}
tal_wally_end(tx->wtx);
}
void sign_tx_input(const struct bitcoin_tx *tx,
unsigned int in,
const u8 *subscript,
const u8 *witness_script,
const struct privkey *privkey, const struct pubkey *key,
enum sighash_type sighash_type,
struct bitcoin_signature *sig)
{
struct sha256_double hash;
bool use_segwit = witness_script != NULL;
const u8 *script = use_segwit ? witness_script : subscript;
assert(sighash_type_valid(sighash_type));
sig->sighash_type = sighash_type;
bitcoin_tx_hash_for_sig(tx, in, script, sighash_type, &hash);
dump_tx("Signing", tx, in, subscript, key, &hash);
sign_hash(privkey, &hash, &sig->s);
}
bool check_signed_hash(const struct sha256_double *hash,
const secp256k1_ecdsa_signature *signature,
const struct pubkey *key)
{
int ret;
ret = secp256k1_ecdsa_verify(secp256k1_ctx,
signature,
hash->sha.u.u8, &key->pubkey);
return ret == 1;
}
bool check_tx_sig(const struct bitcoin_tx *tx, size_t input_num,
const u8 *redeemscript,
const u8 *witness_script,
const struct pubkey *key,
const struct bitcoin_signature *sig)
{
struct sha256_double hash;
bool use_segwit = witness_script != NULL;
const u8 *script = use_segwit ? witness_script : redeemscript;
bool ret;
/* We only support a limited subset of sighash types. */
if (sig->sighash_type != SIGHASH_ALL) {
if (!witness_script)
return false;
if (sig->sighash_type != (SIGHASH_SINGLE|SIGHASH_ANYONECANPAY))
return false;
}
assert(input_num < tx->wtx->num_inputs);
dump_tx("check_tx_sig", tx, input_num, script, key, &hash);
bitcoin_tx_hash_for_sig(tx, input_num, script, sig->sighash_type, &hash);
ret = check_signed_hash(&hash, &sig->s, key);
if (!ret)
dump_tx("Sig failed", tx, input_num, redeemscript, key, &hash);
return ret;
}
/* Stolen direct from bitcoin/src/script/sign.cpp:
// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2014 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
*/
static bool IsValidSignatureEncoding(const unsigned char sig[], size_t len)
{
// Format: 0x30 [total-length] 0x02 [R-length] [R] 0x02 [S-length] [S] [sighash]
// * total-length: 1-byte length descriptor of everything that follows,
// excluding the sighash byte.
// * R-length: 1-byte length descriptor of the R value that follows.
// * R: arbitrary-length big-endian encoded R value. It must use the shortest
// possible encoding for a positive integers (which means no null bytes at
// the start, except a single one when the next byte has its highest bit set).
// * S-length: 1-byte length descriptor of the S value that follows.
// * S: arbitrary-length big-endian encoded S value. The same rules apply.
// * sighash: 1-byte value indicating what data is hashed (not part of the DER
// signature)
// Minimum and maximum size constraints.
if (len < 9) return false;
if (len > 73) return false;
// A signature is of type 0x30 (compound).
if (sig[0] != 0x30) return false;
// Make sure the length covers the entire signature.
if (sig[1] != len - 3) return false;
// Extract the length of the R element.
unsigned int lenR = sig[3];
// Make sure the length of the S element is still inside the signature.
if (5 + lenR >= len) return false;
// Extract the length of the S element.
unsigned int lenS = sig[5 + lenR];
// Verify that the length of the signature matches the sum of the length
// of the elements.
if ((size_t)lenR + (size_t)lenS + 7 != len) return false;
// Check whether the R element is an integer.
if (sig[2] != 0x02) return false;
// Zero-length integers are not allowed for R.
if (lenR == 0) return false;
// Negative numbers are not allowed for R.
if (sig[4] & 0x80) return false;
// Null bytes at the start of R are not allowed, unless R would
// otherwise be interpreted as a negative number.
if (lenR > 1 && (sig[4] == 0x00) && !(sig[5] & 0x80)) return false;
// Check whether the S element is an integer.
if (sig[lenR + 4] != 0x02) return false;
// Zero-length integers are not allowed for S.
if (lenS == 0) return false;
// Negative numbers are not allowed for S.
if (sig[lenR + 6] & 0x80) return false;
// Null bytes at the start of S are not allowed, unless S would otherwise be
// interpreted as a negative number.
if (lenS > 1 && (sig[lenR + 6] == 0x00) && !(sig[lenR + 7] & 0x80)) return false;
return true;
}
size_t signature_to_der(u8 der[73], const struct bitcoin_signature *sig)
{
size_t len = 72;
secp256k1_ecdsa_signature_serialize_der(secp256k1_ctx,
der, &len, &sig->s);
/* Append sighash type */
der[len++] = sig->sighash_type;
/* IsValidSignatureEncoding() expect extra byte for sighash */
assert(IsValidSignatureEncoding(memcheck(der, len), len));
return len;
}
bool signature_from_der(const u8 *der, size_t len, struct bitcoin_signature *sig)
{
if (len < 1)
return false;
if (!secp256k1_ecdsa_signature_parse_der(secp256k1_ctx,
&sig->s, der, len-1))
return false;
sig->sighash_type = der[len-1];
if (!sighash_type_valid(sig->sighash_type))
return false;
return true;
}
char *fmt_signature(const tal_t *ctx, const secp256k1_ecdsa_signature *sig)
{
u8 der[72];
size_t len = 72;
secp256k1_ecdsa_signature_serialize_der(secp256k1_ctx,
der, &len, sig);
return tal_hexstr(ctx, der, len);
}
REGISTER_TYPE_TO_STRING(secp256k1_ecdsa_signature, fmt_signature);
static char *bitcoin_signature_to_hexstr(const tal_t *ctx,
const struct bitcoin_signature *sig)
{
u8 der[73];
size_t len = signature_to_der(der, sig);
return tal_hexstr(ctx, der, len);
}
REGISTER_TYPE_TO_STRING(bitcoin_signature, bitcoin_signature_to_hexstr);
void fromwire_bitcoin_signature(const u8 **cursor, size_t *max,
struct bitcoin_signature *sig)
{
fromwire_secp256k1_ecdsa_signature(cursor, max, &sig->s);
sig->sighash_type = fromwire_u8(cursor, max);
if (!sighash_type_valid(sig->sighash_type))
fromwire_fail(cursor, max);
}
void towire_bitcoin_signature(u8 **pptr, const struct bitcoin_signature *sig)
{
assert(sighash_type_valid(sig->sighash_type));
towire_secp256k1_ecdsa_signature(pptr, &sig->s);
towire_u8(pptr, sig->sighash_type);
}
void towire_bip340sig(u8 **pptr, const struct bip340sig *bip340sig)
{
towire_u8_array(pptr, bip340sig->u8, sizeof(bip340sig->u8));
}
void fromwire_bip340sig(const u8 **cursor, size_t *max,
struct bip340sig *bip340sig)
{
fromwire_u8_array(cursor, max, bip340sig->u8, sizeof(bip340sig->u8));
}
char *fmt_bip340sig(const tal_t *ctx, const struct bip340sig *bip340sig)
{
return tal_hexstr(ctx, bip340sig->u8, sizeof(bip340sig->u8));
}
REGISTER_TYPE_TO_HEXSTR(bip340sig);
/* BIP-340:
*
* This proposal suggests to include the tag by prefixing the hashed
* data with ''SHA256(tag) || SHA256(tag)''. Because this is a 64-byte
* long context-specific constant and the ''SHA256'' block size is
* also 64 bytes, optimized implementations are possible (identical to
* SHA256 itself, but with a modified initial state). Using SHA256 of
* the tag name itself is reasonably simple and efficient for
* implementations that don't choose to use the optimization.
*/
/* For caller convenience, we hand in tag in parts (any can be "") */
void bip340_sighash_init(struct sha256_ctx *sctx,
const char *tag1,
const char *tag2,
const char *tag3)
{
struct sha256 taghash;
sha256_init(sctx);
sha256_update(sctx, memcheck(tag1, strlen(tag1)), strlen(tag1));
sha256_update(sctx, memcheck(tag2, strlen(tag2)), strlen(tag2));
sha256_update(sctx, memcheck(tag3, strlen(tag3)), strlen(tag3));
sha256_done(sctx, &taghash);
sha256_init(sctx);
sha256_update(sctx, &taghash, sizeof(taghash));
sha256_update(sctx, &taghash, sizeof(taghash));
}