111 lines
2.7 KiB
C
111 lines
2.7 KiB
C
#include "signature.h"
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#include "shadouble.h"
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#include "bitcoin_tx.h"
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#include <openssl/bn.h>
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#include <openssl/obj_mac.h>
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#include <assert.h>
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#include <ccan/cast/cast.h>
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struct signature *sign_hash(const tal_t *ctx, EC_KEY *private_key,
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const struct sha256_double *h)
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{
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ECDSA_SIG *sig;
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int len;
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struct signature *s;
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sig = ECDSA_do_sign(h->sha.u.u8, sizeof(*h), private_key);
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if (!sig)
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return NULL;
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/* See https://github.com/sipa/bitcoin/commit/a81cd9680.
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* There can only be one signature with an even S, so make sure we
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* get that one. */
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if (BN_is_odd(sig->s)) {
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const EC_GROUP *group;
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BIGNUM order;
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BN_init(&order);
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group = EC_KEY_get0_group(private_key);
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EC_GROUP_get_order(group, &order, NULL);
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BN_sub(sig->s, &order, sig->s);
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BN_free(&order);
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assert(!BN_is_odd(sig->s));
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}
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s = talz(ctx, struct signature);
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/* Pack r and s into signature, 32 bytes each. */
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len = BN_num_bytes(sig->r);
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assert(len <= sizeof(s->r));
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BN_bn2bin(sig->r, s->r + sizeof(s->r) - len);
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len = BN_num_bytes(sig->s);
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assert(len <= sizeof(s->s));
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BN_bn2bin(sig->s, s->s + sizeof(s->s) - len);
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ECDSA_SIG_free(sig);
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return s;
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}
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struct signature *sign_tx_input(const tal_t *ctx, struct bitcoin_tx *tx,
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unsigned int in,
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const u8 *subscript, size_t subscript_len,
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EC_KEY *privkey)
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{
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struct sha256_double hash;
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struct sha256_ctx shactx;
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/* Transaction gets signed as if the output subscript is the
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* only input script. */
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tx->input[in].script_length = subscript_len;
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tx->input[in].script = cast_const(u8 *, subscript);
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sha256_init(&shactx);
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sha256_tx(&shactx, tx);
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sha256_le32(&shactx, SIGHASH_ALL);
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sha256_double_done(&shactx, &hash);
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/* Reset it for next time. */
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tx->input[in].script_length = 0;
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tx->input[in].script = NULL;
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return sign_hash(ctx, privkey, &hash);
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}
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Signature *signature_to_proto(const tal_t *ctx, const struct signature *sig)
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{
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Signature *pb = tal(ctx, Signature);
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signature__init(pb);
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assert((sig->s[31] & 1) == 0);
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/* Kill me now... */
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memcpy(&pb->r1, sig->r, 8);
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memcpy(&pb->r2, sig->r + 8, 8);
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memcpy(&pb->r3, sig->r + 16, 8);
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memcpy(&pb->r4, sig->r + 24, 8);
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memcpy(&pb->s1, sig->s, 8);
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memcpy(&pb->s2, sig->s + 8, 8);
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memcpy(&pb->s3, sig->s + 16, 8);
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memcpy(&pb->s4, sig->s + 24, 8);
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return pb;
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}
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bool proto_to_signature(const Signature *pb, struct signature *sig)
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{
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/* Kill me again. */
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memcpy(sig->r, &pb->r1, 8);
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memcpy(sig->r + 8, &pb->r2, 8);
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memcpy(sig->r + 16, &pb->r3, 8);
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memcpy(sig->r + 24, &pb->r4, 8);
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memcpy(sig->s, &pb->s1, 8);
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memcpy(sig->s + 8, &pb->s2, 8);
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memcpy(sig->s + 16, &pb->s3, 8);
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memcpy(sig->s + 24, &pb->s4, 8);
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/* S must be even */
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return (sig->s[31] & 1) == 0;
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}
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