145 lines
4.4 KiB
Go
145 lines
4.4 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 wraps the bitcoin secp256k1 C library.
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package secp256k1
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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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#define USE_NUM_NONE
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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 "ext.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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)
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var context *C.secp256k1_context
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func init() {
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// around 20 ms on a modern CPU.
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context = C.secp256k1_context_create_sign_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, need 32 bytes")
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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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ErrInvalidKey = errors.New("invalid private key")
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ErrSignFailed = errors.New("signing failed")
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ErrRecoverFailed = errors.New("recovery failed")
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)
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// Sign creates a recoverable ECDSA signature.
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// The produced signature is in the 65-byte [R || S || V] format where V is 0 or 1.
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//
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// The caller is responsible for ensuring that msg cannot be chosen
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// directly by an attacker. It is usually preferable to use a cryptographic
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// hash function on any input before handing it to this function.
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func Sign(msg []byte, seckey []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 len(seckey) != 32 {
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return nil, ErrInvalidKey
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}
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seckeydata := (*C.uchar)(unsafe.Pointer(&seckey[0]))
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if C.secp256k1_ec_seckey_verify(context, seckeydata) != 1 {
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return nil, ErrInvalidKey
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}
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var (
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msgdata = (*C.uchar)(unsafe.Pointer(&msg[0]))
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noncefunc = C.secp256k1_nonce_function_rfc6979
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sigstruct C.secp256k1_ecdsa_recoverable_signature
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)
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if C.secp256k1_ecdsa_sign_recoverable(context, &sigstruct, msgdata, seckeydata, noncefunc, nil) == 0 {
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return nil, ErrSignFailed
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}
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var (
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sig = make([]byte, 65)
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sigdata = (*C.uchar)(unsafe.Pointer(&sig[0]))
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recid C.int
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)
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C.secp256k1_ecdsa_recoverable_signature_serialize_compact(context, sigdata, &recid, &sigstruct)
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sig[64] = byte(recid) // add back recid to get 65 bytes sig
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return sig, 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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var (
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pubkey = make([]byte, 65)
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sigdata = (*C.uchar)(unsafe.Pointer(&sig[0]))
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msgdata = (*C.uchar)(unsafe.Pointer(&msg[0]))
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)
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if C.secp256k1_ecdsa_recover_pubkey(context, (*C.uchar)(unsafe.Pointer(&pubkey[0])), sigdata, msgdata) == 0 {
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return nil, ErrRecoverFailed
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}
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return pubkey, 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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