275 lines
7.5 KiB
Go
275 lines
7.5 KiB
Go
// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package secp256k1
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// TODO: set USE_SCALAR_4X64 depending on platform?
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/*
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#cgo CFLAGS: -I./libsecp256k1
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#cgo CFLAGS: -I./libsecp256k1/src/
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#cgo darwin CFLAGS: -I/usr/local/include
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#cgo freebsd CFLAGS: -I/usr/local/include
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#cgo linux,arm CFLAGS: -I/usr/local/arm/include
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#cgo LDFLAGS: -lgmp
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#cgo darwin LDFLAGS: -L/usr/local/lib
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#cgo freebsd LDFLAGS: -L/usr/local/lib
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#cgo linux,arm LDFLAGS: -L/usr/local/arm/lib
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#define USE_NUM_GMP
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#define USE_FIELD_10X26
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#define USE_FIELD_INV_BUILTIN
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#define USE_SCALAR_8X32
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#define USE_SCALAR_INV_BUILTIN
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#define NDEBUG
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#include "./libsecp256k1/src/secp256k1.c"
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#include "./libsecp256k1/src/modules/recovery/main_impl.h"
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#include "pubkey_scalar_mul.h"
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typedef void (*callbackFunc) (const char* msg, void* data);
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extern void secp256k1GoPanicIllegal(const char* msg, void* data);
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extern void secp256k1GoPanicError(const char* msg, void* data);
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*/
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import "C"
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import (
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"errors"
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"math/big"
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"unsafe"
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"github.com/ethereum/go-ethereum/crypto/randentropy"
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)
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//#define USE_FIELD_5X64
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/*
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TODO:
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> store private keys in buffer and shuffle (deters persistance on swap disc)
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> byte permutation (changing)
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> xor with chaning random block (to deter scanning memory for 0x63) (stream cipher?)
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*/
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// holds ptr to secp256k1_context_struct (see secp256k1/include/secp256k1.h)
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var (
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context *C.secp256k1_context
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N *big.Int
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)
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func init() {
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N, _ = new(big.Int).SetString("fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141", 16)
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// around 20 ms on a modern CPU.
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context = C.secp256k1_context_create(3) // SECP256K1_START_SIGN | SECP256K1_START_VERIFY
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C.secp256k1_context_set_illegal_callback(context, C.callbackFunc(C.secp256k1GoPanicIllegal), nil)
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C.secp256k1_context_set_error_callback(context, C.callbackFunc(C.secp256k1GoPanicError), nil)
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}
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var (
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ErrInvalidMsgLen = errors.New("invalid message length for signature recovery")
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ErrInvalidSignatureLen = errors.New("invalid signature length")
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ErrInvalidRecoveryID = errors.New("invalid signature recovery id")
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)
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func GenerateKeyPair() ([]byte, []byte) {
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var seckey []byte = randentropy.GetEntropyCSPRNG(32)
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var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
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var pubkey64 []byte = make([]byte, 64) // secp256k1_pubkey
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var pubkey65 []byte = make([]byte, 65) // 65 byte uncompressed pubkey
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pubkey64_ptr := (*C.secp256k1_pubkey)(unsafe.Pointer(&pubkey64[0]))
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pubkey65_ptr := (*C.uchar)(unsafe.Pointer(&pubkey65[0]))
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ret := C.secp256k1_ec_pubkey_create(
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context,
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pubkey64_ptr,
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seckey_ptr,
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)
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if ret != C.int(1) {
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return GenerateKeyPair() // invalid secret, try again
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}
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var output_len C.size_t
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C.secp256k1_ec_pubkey_serialize( // always returns 1
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context,
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pubkey65_ptr,
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&output_len,
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pubkey64_ptr,
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0, // SECP256K1_EC_COMPRESSED
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)
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return pubkey65, seckey
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}
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func GeneratePubKey(seckey []byte) ([]byte, error) {
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if err := VerifySeckeyValidity(seckey); err != nil {
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return nil, err
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}
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var pubkey []byte = make([]byte, 64)
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var pubkey_ptr *C.secp256k1_pubkey = (*C.secp256k1_pubkey)(unsafe.Pointer(&pubkey[0]))
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var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
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ret := C.secp256k1_ec_pubkey_create(
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context,
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pubkey_ptr,
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seckey_ptr,
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)
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if ret != C.int(1) {
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return nil, errors.New("Unable to generate pubkey from seckey")
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}
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return pubkey, nil
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}
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func Sign(msg []byte, seckey []byte) ([]byte, error) {
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msg_ptr := (*C.uchar)(unsafe.Pointer(&msg[0]))
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seckey_ptr := (*C.uchar)(unsafe.Pointer(&seckey[0]))
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sig := make([]byte, 65)
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sig_ptr := (*C.secp256k1_ecdsa_recoverable_signature)(unsafe.Pointer(&sig[0]))
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nonce := randentropy.GetEntropyCSPRNG(32)
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ndata_ptr := unsafe.Pointer(&nonce[0])
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noncefp_ptr := &(*C.secp256k1_nonce_function_default)
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if C.secp256k1_ec_seckey_verify(context, seckey_ptr) != C.int(1) {
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return nil, errors.New("Invalid secret key")
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}
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ret := C.secp256k1_ecdsa_sign_recoverable(
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context,
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sig_ptr,
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msg_ptr,
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seckey_ptr,
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noncefp_ptr,
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ndata_ptr,
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)
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if ret == C.int(0) {
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return Sign(msg, seckey) //invalid secret, try again
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}
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sig_serialized := make([]byte, 65)
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sig_serialized_ptr := (*C.uchar)(unsafe.Pointer(&sig_serialized[0]))
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var recid C.int
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C.secp256k1_ecdsa_recoverable_signature_serialize_compact(
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context,
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sig_serialized_ptr, // 64 byte compact signature
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&recid,
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sig_ptr, // 65 byte "recoverable" signature
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)
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sig_serialized[64] = byte(int(recid)) // add back recid to get 65 bytes sig
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return sig_serialized, nil
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}
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func VerifySeckeyValidity(seckey []byte) error {
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if len(seckey) != 32 {
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return errors.New("priv key is not 32 bytes")
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}
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var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
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ret := C.secp256k1_ec_seckey_verify(context, seckey_ptr)
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if int(ret) != 1 {
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return errors.New("invalid seckey")
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}
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return nil
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}
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// RecoverPubkey returns the the public key of the signer.
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// msg must be the 32-byte hash of the message to be signed.
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// sig must be a 65-byte compact ECDSA signature containing the
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// recovery id as the last element.
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func RecoverPubkey(msg []byte, sig []byte) ([]byte, error) {
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if len(msg) != 32 {
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return nil, ErrInvalidMsgLen
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}
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if err := checkSignature(sig); err != nil {
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return nil, err
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}
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msg_ptr := (*C.uchar)(unsafe.Pointer(&msg[0]))
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sig_ptr := (*C.uchar)(unsafe.Pointer(&sig[0]))
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pubkey := make([]byte, 64)
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/*
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this slice is used for both the recoverable signature and the
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resulting serialized pubkey (both types in libsecp256k1 are 65
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bytes). this saves one allocation of 65 bytes, which is nice as
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pubkey recovery is one bottleneck during load in Ethereum
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*/
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bytes65 := make([]byte, 65)
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pubkey_ptr := (*C.secp256k1_pubkey)(unsafe.Pointer(&pubkey[0]))
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recoverable_sig_ptr := (*C.secp256k1_ecdsa_recoverable_signature)(unsafe.Pointer(&bytes65[0]))
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recid := C.int(sig[64])
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ret := C.secp256k1_ecdsa_recoverable_signature_parse_compact(
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context,
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recoverable_sig_ptr,
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sig_ptr,
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recid)
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if ret == C.int(0) {
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return nil, errors.New("Failed to parse signature")
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}
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ret = C.secp256k1_ecdsa_recover(
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context,
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pubkey_ptr,
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recoverable_sig_ptr,
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msg_ptr,
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)
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if ret == C.int(0) {
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return nil, errors.New("Failed to recover public key")
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}
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serialized_pubkey_ptr := (*C.uchar)(unsafe.Pointer(&bytes65[0]))
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var output_len C.size_t
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C.secp256k1_ec_pubkey_serialize( // always returns 1
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context,
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serialized_pubkey_ptr,
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&output_len,
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pubkey_ptr,
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0, // SECP256K1_EC_COMPRESSED
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)
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return bytes65, nil
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}
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func checkSignature(sig []byte) error {
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if len(sig) != 65 {
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return ErrInvalidSignatureLen
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}
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if sig[64] >= 4 {
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return ErrInvalidRecoveryID
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}
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return nil
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}
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// reads num into buf as big-endian bytes.
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func readBits(buf []byte, num *big.Int) {
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const wordLen = int(unsafe.Sizeof(big.Word(0)))
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i := len(buf)
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for _, d := range num.Bits() {
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for j := 0; j < wordLen && i > 0; j++ {
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i--
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buf[i] = byte(d)
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d >>= 8
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}
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}
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}
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