From c6069a627c42c21fc02d0770d39db9a9be45b180 Mon Sep 17 00:00:00 2001 From: Felix Lange Date: Fri, 15 Dec 2017 10:40:09 +0100 Subject: [PATCH] crypto, crypto/secp256k1: add CompressPubkey (#15626) This adds the inverse to DecompressPubkey and improves a few minor details in crypto/secp256k1. --- crypto/secp256k1/curve.go | 46 +++++++++++++++---------------------- crypto/secp256k1/ext.h | 40 ++++++++++++++++++-------------- crypto/secp256k1/secp256.go | 36 ++++++++++++++++++++++------- crypto/signature_cgo.go | 5 ++++ crypto/signature_nocgo.go | 5 ++++ crypto/signature_test.go | 38 ++++++++++++++++++++++++++++++ 6 files changed, 118 insertions(+), 52 deletions(-) diff --git a/crypto/secp256k1/curve.go b/crypto/secp256k1/curve.go index ec6d266cec..df80481857 100644 --- a/crypto/secp256k1/curve.go +++ b/crypto/secp256k1/curve.go @@ -34,7 +34,6 @@ package secp256k1 import ( "crypto/elliptic" "math/big" - "sync" "unsafe" "github.com/ethereum/go-ethereum/common/math" @@ -42,7 +41,7 @@ import ( /* #include "libsecp256k1/include/secp256k1.h" -extern int secp256k1_pubkey_scalar_mul(const secp256k1_context* ctx, const unsigned char *point, const unsigned char *scalar); +extern int secp256k1_ext_scalar_mul(const secp256k1_context* ctx, const unsigned char *point, const unsigned char *scalar); */ import "C" @@ -236,7 +235,7 @@ func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int, math.ReadBits(By, point[32:]) pointPtr := (*C.uchar)(unsafe.Pointer(&point[0])) scalarPtr := (*C.uchar)(unsafe.Pointer(&scalar[0])) - res := C.secp256k1_pubkey_scalar_mul(context, pointPtr, scalarPtr) + res := C.secp256k1_ext_scalar_mul(context, pointPtr, scalarPtr) // Unpack the result and clear temporaries. x := new(big.Int).SetBytes(point[:32]) @@ -263,14 +262,10 @@ func (BitCurve *BitCurve) ScalarBaseMult(k []byte) (*big.Int, *big.Int) { // X9.62. func (BitCurve *BitCurve) Marshal(x, y *big.Int) []byte { byteLen := (BitCurve.BitSize + 7) >> 3 - ret := make([]byte, 1+2*byteLen) - ret[0] = 4 // uncompressed point - - xBytes := x.Bytes() - copy(ret[1+byteLen-len(xBytes):], xBytes) - yBytes := y.Bytes() - copy(ret[1+2*byteLen-len(yBytes):], yBytes) + ret[0] = 4 // uncompressed point flag + math.ReadBits(x, ret[1:1+byteLen]) + math.ReadBits(y, ret[1+byteLen:]) return ret } @@ -289,24 +284,21 @@ func (BitCurve *BitCurve) Unmarshal(data []byte) (x, y *big.Int) { return } -var ( - initonce sync.Once - theCurve *BitCurve -) +var theCurve = new(BitCurve) + +func init() { + // See SEC 2 section 2.7.1 + // curve parameters taken from: + // http://www.secg.org/collateral/sec2_final.pdf + theCurve.P, _ = new(big.Int).SetString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F", 16) + theCurve.N, _ = new(big.Int).SetString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141", 16) + theCurve.B, _ = new(big.Int).SetString("0000000000000000000000000000000000000000000000000000000000000007", 16) + theCurve.Gx, _ = new(big.Int).SetString("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798", 16) + theCurve.Gy, _ = new(big.Int).SetString("483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8", 16) + theCurve.BitSize = 256 +} -// S256 returns a BitCurve which implements secp256k1 (see SEC 2 section 2.7.1) +// S256 returns a BitCurve which implements secp256k1. func S256() *BitCurve { - initonce.Do(func() { - // See SEC 2 section 2.7.1 - // curve parameters taken from: - // http://www.secg.org/collateral/sec2_final.pdf - theCurve = new(BitCurve) - theCurve.P, _ = new(big.Int).SetString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F", 16) - theCurve.N, _ = new(big.Int).SetString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141", 16) - theCurve.B, _ = new(big.Int).SetString("0000000000000000000000000000000000000000000000000000000000000007", 16) - theCurve.Gx, _ = new(big.Int).SetString("79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798", 16) - theCurve.Gy, _ = new(big.Int).SetString("483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8", 16) - theCurve.BitSize = 256 - }) return theCurve } diff --git a/crypto/secp256k1/ext.h b/crypto/secp256k1/ext.h index b0f30b73c6..9b043c724e 100644 --- a/crypto/secp256k1/ext.h +++ b/crypto/secp256k1/ext.h @@ -19,7 +19,7 @@ static secp256k1_context* secp256k1_context_create_sign_verify() { return secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY); } -// secp256k1_ecdsa_recover_pubkey recovers the public key of an encoded compact signature. +// secp256k1_ext_ecdsa_recover recovers the public key of an encoded compact signature. // // Returns: 1: recovery was successful // 0: recovery was not successful @@ -27,7 +27,7 @@ static secp256k1_context* secp256k1_context_create_sign_verify() { // Out: pubkey_out: the serialized 65-byte public key of the signer (cannot be NULL) // In: sigdata: pointer to a 65-byte signature with the recovery id at the end (cannot be NULL) // msgdata: pointer to a 32-byte message (cannot be NULL) -static int secp256k1_ecdsa_recover_pubkey( +static int secp256k1_ext_ecdsa_recover( const secp256k1_context* ctx, unsigned char *pubkey_out, const unsigned char *sigdata, @@ -46,7 +46,7 @@ static int secp256k1_ecdsa_recover_pubkey( return secp256k1_ec_pubkey_serialize(ctx, pubkey_out, &outputlen, &pubkey, SECP256K1_EC_UNCOMPRESSED); } -// secp256k1_ecdsa_verify_enc verifies an encoded compact signature. +// secp256k1_ext_ecdsa_verify verifies an encoded compact signature. // // Returns: 1: signature is valid // 0: signature is invalid @@ -55,7 +55,7 @@ static int secp256k1_ecdsa_recover_pubkey( // msgdata: pointer to a 32-byte message (cannot be NULL) // pubkeydata: pointer to public key data (cannot be NULL) // pubkeylen: length of pubkeydata -static int secp256k1_ecdsa_verify_enc( +static int secp256k1_ext_ecdsa_verify( const secp256k1_context* ctx, const unsigned char *sigdata, const unsigned char *msgdata, @@ -74,28 +74,34 @@ static int secp256k1_ecdsa_verify_enc( return secp256k1_ecdsa_verify(ctx, &sig, msgdata, &pubkey); } -// secp256k1_decompress_pubkey decompresses a public key. +// secp256k1_ext_reencode_pubkey decodes then encodes a public key. It can be used to +// convert between public key formats. The input/output formats are chosen depending on the +// length of the input/output buffers. // -// Returns: 1: public key is valid -// 0: public key is invalid +// Returns: 1: conversion successful +// 0: conversion unsuccessful // Args: ctx: pointer to a context object (cannot be NULL) -// Out: pubkey_out: the serialized 65-byte public key (cannot be NULL) -// In: pubkeydata: pointer to 33 bytes of compressed public key data (cannot be NULL) -static int secp256k1_decompress_pubkey( +// Out: out: output buffer that will contain the reencoded key (cannot be NULL) +// In: outlen: length of out (33 for compressed keys, 65 for uncompressed keys) +// pubkeydata: the input public key (cannot be NULL) +// pubkeylen: length of pubkeydata +static int secp256k1_ext_reencode_pubkey( const secp256k1_context* ctx, - unsigned char *pubkey_out, - const unsigned char *pubkeydata + unsigned char *out, + size_t outlen, + const unsigned char *pubkeydata, + size_t pubkeylen ) { secp256k1_pubkey pubkey; - if (!secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeydata, 33)) { + if (!secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeydata, pubkeylen)) { return 0; } - size_t outputlen = 65; - return secp256k1_ec_pubkey_serialize(ctx, pubkey_out, &outputlen, &pubkey, SECP256K1_EC_UNCOMPRESSED); + unsigned int flag = (outlen == 33) ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED; + return secp256k1_ec_pubkey_serialize(ctx, out, &outlen, &pubkey, flag); } -// secp256k1_pubkey_scalar_mul multiplies a point by a scalar in constant time. +// secp256k1_ext_scalar_mul multiplies a point by a scalar in constant time. // // Returns: 1: multiplication was successful // 0: scalar was invalid (zero or overflow) @@ -104,7 +110,7 @@ static int secp256k1_decompress_pubkey( // In: point: pointer to a 64-byte public point, // encoded as two 256bit big-endian numbers. // scalar: a 32-byte scalar with which to multiply the point -int secp256k1_pubkey_scalar_mul(const secp256k1_context* ctx, unsigned char *point, const unsigned char *scalar) { +int secp256k1_ext_scalar_mul(const secp256k1_context* ctx, unsigned char *point, const unsigned char *scalar) { int ret = 0; int overflow = 0; secp256k1_fe feX, feY; diff --git a/crypto/secp256k1/secp256.go b/crypto/secp256k1/secp256.go index 00a1f8aaa4..eefbb99ee4 100644 --- a/crypto/secp256k1/secp256.go +++ b/crypto/secp256k1/secp256.go @@ -115,7 +115,7 @@ func RecoverPubkey(msg []byte, sig []byte) ([]byte, error) { sigdata = (*C.uchar)(unsafe.Pointer(&sig[0])) msgdata = (*C.uchar)(unsafe.Pointer(&msg[0])) ) - if C.secp256k1_ecdsa_recover_pubkey(context, (*C.uchar)(unsafe.Pointer(&pubkey[0])), sigdata, msgdata) == 0 { + if C.secp256k1_ext_ecdsa_recover(context, (*C.uchar)(unsafe.Pointer(&pubkey[0])), sigdata, msgdata) == 0 { return nil, ErrRecoverFailed } return pubkey, nil @@ -130,22 +130,42 @@ func VerifySignature(pubkey, msg, signature []byte) bool { sigdata := (*C.uchar)(unsafe.Pointer(&signature[0])) msgdata := (*C.uchar)(unsafe.Pointer(&msg[0])) keydata := (*C.uchar)(unsafe.Pointer(&pubkey[0])) - return C.secp256k1_ecdsa_verify_enc(context, sigdata, msgdata, keydata, C.size_t(len(pubkey))) != 0 + return C.secp256k1_ext_ecdsa_verify(context, sigdata, msgdata, keydata, C.size_t(len(pubkey))) != 0 } // DecompressPubkey parses a public key in the 33-byte compressed format. // It returns non-nil coordinates if the public key is valid. -func DecompressPubkey(pubkey []byte) (X, Y *big.Int) { +func DecompressPubkey(pubkey []byte) (x, y *big.Int) { if len(pubkey) != 33 { return nil, nil } - buf := make([]byte, 65) - bufdata := (*C.uchar)(unsafe.Pointer(&buf[0])) - pubkeydata := (*C.uchar)(unsafe.Pointer(&pubkey[0])) - if C.secp256k1_decompress_pubkey(context, bufdata, pubkeydata) == 0 { + var ( + pubkeydata = (*C.uchar)(unsafe.Pointer(&pubkey[0])) + pubkeylen = C.size_t(len(pubkey)) + out = make([]byte, 65) + outdata = (*C.uchar)(unsafe.Pointer(&out[0])) + outlen = C.size_t(len(out)) + ) + if C.secp256k1_ext_reencode_pubkey(context, outdata, outlen, pubkeydata, pubkeylen) == 0 { return nil, nil } - return new(big.Int).SetBytes(buf[1:33]), new(big.Int).SetBytes(buf[33:]) + return new(big.Int).SetBytes(out[1:33]), new(big.Int).SetBytes(out[33:]) +} + +// CompressPubkey encodes a public key to 33-byte compressed format. +func CompressPubkey(x, y *big.Int) []byte { + var ( + pubkey = S256().Marshal(x, y) + pubkeydata = (*C.uchar)(unsafe.Pointer(&pubkey[0])) + pubkeylen = C.size_t(len(pubkey)) + out = make([]byte, 33) + outdata = (*C.uchar)(unsafe.Pointer(&out[0])) + outlen = C.size_t(len(out)) + ) + if C.secp256k1_ext_reencode_pubkey(context, outdata, outlen, pubkeydata, pubkeylen) == 0 { + panic("libsecp256k1 error") + } + return out } func checkSignature(sig []byte) error { diff --git a/crypto/signature_cgo.go b/crypto/signature_cgo.go index 381d8a1bbc..340bfc221e 100644 --- a/crypto/signature_cgo.go +++ b/crypto/signature_cgo.go @@ -76,6 +76,11 @@ func DecompressPubkey(pubkey []byte) (*ecdsa.PublicKey, error) { return &ecdsa.PublicKey{X: x, Y: y, Curve: S256()}, nil } +// CompressPubkey encodes a public key to the 33-byte compressed format. +func CompressPubkey(pubkey *ecdsa.PublicKey) []byte { + return secp256k1.CompressPubkey(pubkey.X, pubkey.Y) +} + // S256 returns an instance of the secp256k1 curve. func S256() elliptic.Curve { return secp256k1.S256() diff --git a/crypto/signature_nocgo.go b/crypto/signature_nocgo.go index 17fd613b21..78b99c02b0 100644 --- a/crypto/signature_nocgo.go +++ b/crypto/signature_nocgo.go @@ -102,6 +102,11 @@ func DecompressPubkey(pubkey []byte) (*ecdsa.PublicKey, error) { return key.ToECDSA(), nil } +// CompressPubkey encodes a public key to the 33-byte compressed format. +func CompressPubkey(pubkey *ecdsa.PublicKey) []byte { + return (*btcec.PublicKey)(pubkey).SerializeCompressed() +} + // S256 returns an instance of the secp256k1 curve. func S256() elliptic.Curve { return btcec.S256() diff --git a/crypto/signature_test.go b/crypto/signature_test.go index abcab425b5..5e2efc7e05 100644 --- a/crypto/signature_test.go +++ b/crypto/signature_test.go @@ -18,10 +18,13 @@ package crypto import ( "bytes" + "crypto/ecdsa" + "reflect" "testing" "github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/common/hexutil" + "github.com/ethereum/go-ethereum/common/math" ) var ( @@ -65,6 +68,11 @@ func TestVerifySignature(t *testing.T) { if VerifySignature(testpubkey, testmsg, sig[:len(sig)-2]) { t.Errorf("signature valid even though it's incomplete") } + wrongkey := common.CopyBytes(testpubkey) + wrongkey[10]++ + if VerifySignature(wrongkey, testmsg, sig) { + t.Errorf("signature valid with with wrong public key") + } } func TestDecompressPubkey(t *testing.T) { @@ -86,6 +94,36 @@ func TestDecompressPubkey(t *testing.T) { } } +func TestCompressPubkey(t *testing.T) { + key := &ecdsa.PublicKey{ + Curve: S256(), + X: math.MustParseBig256("0xe32df42865e97135acfb65f3bae71bdc86f4d49150ad6a440b6f15878109880a"), + Y: math.MustParseBig256("0x0a2b2667f7e725ceea70c673093bf67663e0312623c8e091b13cf2c0f11ef652"), + } + compressed := CompressPubkey(key) + if !bytes.Equal(compressed, testpubkeyc) { + t.Errorf("wrong public key result: got %x, want %x", compressed, testpubkeyc) + } +} + +func TestPubkeyRandom(t *testing.T) { + const runs = 200 + + for i := 0; i < runs; i++ { + key, err := GenerateKey() + if err != nil { + t.Fatalf("iteration %d: %v", i, err) + } + pubkey2, err := DecompressPubkey(CompressPubkey(&key.PublicKey)) + if err != nil { + t.Fatalf("iteration %d: %v", i, err) + } + if !reflect.DeepEqual(key.PublicKey, *pubkey2) { + t.Fatalf("iteration %d: keys not equal", i) + } + } +} + func BenchmarkEcrecoverSignature(b *testing.B) { for i := 0; i < b.N; i++ { if _, err := Ecrecover(testmsg, testsig); err != nil {