remove libsecp256k1 build tag (#7823)

We no longer use cgo for anything in this package.
Consolidate the non-cgo code with the rest of the library.

crypto/secp256k1/secp256k1.go

@@ -179,3 +179,67 @@ func (pubKey PubKey) Equals(other crypto.PubKey) bool {
 func (pubKey PubKey) Type() string {
 	return KeyType
 }
+
+// used to reject malleable signatures
+// see:
+//  - https://github.com/ethereum/go-ethereum/blob/f9401ae011ddf7f8d2d95020b7446c17f8d98dc1/crypto/signature_nocgo.go#L90-L93
+//  - https://github.com/ethereum/go-ethereum/blob/f9401ae011ddf7f8d2d95020b7446c17f8d98dc1/crypto/crypto.go#L39
+var secp256k1halfN = new(big.Int).Rsh(secp256k1.S256().N, 1)
+
+// Sign creates an ECDSA signature on curve Secp256k1, using SHA256 on the msg.
+// The returned signature will be of the form R || S (in lower-S form).
+func (privKey PrivKey) Sign(msg []byte) ([]byte, error) {
+	priv, _ := secp256k1.PrivKeyFromBytes(secp256k1.S256(), privKey)
+
+	sig, err := priv.Sign(crypto.Sha256(msg))
+	if err != nil {
+		return nil, err
+	}
+
+	sigBytes := serializeSig(sig)
+	return sigBytes, nil
+}
+
+// VerifySignature verifies a signature of the form R || S.
+// It rejects signatures which are not in lower-S form.
+func (pubKey PubKey) VerifySignature(msg []byte, sigStr []byte) bool {
+	if len(sigStr) != 64 {
+		return false
+	}
+
+	pub, err := secp256k1.ParsePubKey(pubKey, secp256k1.S256())
+	if err != nil {
+		return false
+	}
+
+	// parse the signature:
+	signature := signatureFromBytes(sigStr)
+	// Reject malleable signatures. libsecp256k1 does this check but btcec doesn't.
+	// see: https://github.com/ethereum/go-ethereum/blob/f9401ae011ddf7f8d2d95020b7446c17f8d98dc1/crypto/signature_nocgo.go#L90-L93
+	if signature.S.Cmp(secp256k1halfN) > 0 {
+		return false
+	}
+
+	return signature.Verify(crypto.Sha256(msg), pub)
+}
+
+// Read Signature struct from R || S. Caller needs to ensure
+// that len(sigStr) == 64.
+func signatureFromBytes(sigStr []byte) *secp256k1.Signature {
+	return &secp256k1.Signature{
+		R: new(big.Int).SetBytes(sigStr[:32]),
+		S: new(big.Int).SetBytes(sigStr[32:64]),
+	}
+}
+
+// Serialize signature to R || S.
+// R, S are padded to 32 bytes respectively.
+func serializeSig(sig *secp256k1.Signature) []byte {
+	rBytes := sig.R.Bytes()
+	sBytes := sig.S.Bytes()
+	sigBytes := make([]byte, 64)
+	// 0 pad the byte arrays from the left if they aren't big enough.
+	copy(sigBytes[32-len(rBytes):32], rBytes)
+	copy(sigBytes[64-len(sBytes):64], sBytes)
+	return sigBytes
+}

crypto/secp256k1/secp256k1_nocgo.go

@@ -1,76 +0,0 @@
-//go:build !libsecp256k1
-// +build !libsecp256k1
-
-package secp256k1
-
-import (
-	"math/big"
-
-	secp256k1 "github.com/btcsuite/btcd/btcec"
-
-	"github.com/tendermint/tendermint/crypto"
-)
-
-// used to reject malleable signatures
-// see:
-//  - https://github.com/ethereum/go-ethereum/blob/f9401ae011ddf7f8d2d95020b7446c17f8d98dc1/crypto/signature_nocgo.go#L90-L93
-//  - https://github.com/ethereum/go-ethereum/blob/f9401ae011ddf7f8d2d95020b7446c17f8d98dc1/crypto/crypto.go#L39
-var secp256k1halfN = new(big.Int).Rsh(secp256k1.S256().N, 1)
-
-// Sign creates an ECDSA signature on curve Secp256k1, using SHA256 on the msg.
-// The returned signature will be of the form R || S (in lower-S form).
-func (privKey PrivKey) Sign(msg []byte) ([]byte, error) {
-	priv, _ := secp256k1.PrivKeyFromBytes(secp256k1.S256(), privKey)
-
-	sig, err := priv.Sign(crypto.Sha256(msg))
-	if err != nil {
-		return nil, err
-	}
-
-	sigBytes := serializeSig(sig)
-	return sigBytes, nil
-}
-
-// VerifySignature verifies a signature of the form R || S.
-// It rejects signatures which are not in lower-S form.
-func (pubKey PubKey) VerifySignature(msg []byte, sigStr []byte) bool {
-	if len(sigStr) != 64 {
-		return false
-	}
-
-	pub, err := secp256k1.ParsePubKey(pubKey, secp256k1.S256())
-	if err != nil {
-		return false
-	}
-
-	// parse the signature:
-	signature := signatureFromBytes(sigStr)
-	// Reject malleable signatures. libsecp256k1 does this check but btcec doesn't.
-	// see: https://github.com/ethereum/go-ethereum/blob/f9401ae011ddf7f8d2d95020b7446c17f8d98dc1/crypto/signature_nocgo.go#L90-L93
-	if signature.S.Cmp(secp256k1halfN) > 0 {
-		return false
-	}
-
-	return signature.Verify(crypto.Sha256(msg), pub)
-}
-
-// Read Signature struct from R || S. Caller needs to ensure
-// that len(sigStr) == 64.
-func signatureFromBytes(sigStr []byte) *secp256k1.Signature {
-	return &secp256k1.Signature{
-		R: new(big.Int).SetBytes(sigStr[:32]),
-		S: new(big.Int).SetBytes(sigStr[32:64]),
-	}
-}
-
-// Serialize signature to R || S.
-// R, S are padded to 32 bytes respectively.
-func serializeSig(sig *secp256k1.Signature) []byte {
-	rBytes := sig.R.Bytes()
-	sBytes := sig.S.Bytes()
-	sigBytes := make([]byte, 64)
-	// 0 pad the byte arrays from the left if they aren't big enough.
-	copy(sigBytes[32-len(rBytes):32], rBytes)
-	copy(sigBytes[64-len(sBytes):64], sBytes)
-	return sigBytes
-}