Moved `obscuren` secp256k1-go

1 files changed, 304 insertions, 0 deletions

diff --git a/crypto/secp256k1/secp256.go b/crypto/secp256k1/secp256.go
new file mode 100644
index 000000000..53ad9b477
--- /dev/null
+++ b/crypto/secp256k1/secp256.go
@@ -0,0 +1,304 @@
+package secp256k1
+
+/*
+#cgo CFLAGS: -std=gnu99 -Wno-error
+#cgo darwin CFLAGS: -I/usr/local/include
+#cgo LDFLAGS: -lgmp
+#cgo darwin LDFLAGS: -L/usr/local/lib
+#define USE_FIELD_10X26
+#define USE_NUM_GMP
+#define USE_FIELD_INV_BUILTIN
+#include "./secp256k1/src/secp256k1.c"
+*/
+import "C"
+
+import (
+	"bytes"
+	"errors"
+	"unsafe"
+)
+
+//#define USE_FIELD_5X64
+
+/*
+   Todo:
+   > Centralize key management in module
+   > add pubkey/private key struct
+   > Dont let keys leave module; address keys as ints
+
+   > store private keys in buffer and shuffle (deters persistance on swap disc)
+   > Byte permutation (changing)
+   > xor with chaning random block (to deter scanning memory for 0x63) (stream cipher?)
+
+   On Disk
+   > Store keys in wallets
+   > use slow key derivation function for wallet encryption key (2 seconds)
+*/
+
+func init() {
+	C.secp256k1_start() //takes 10ms to 100ms
+}
+
+func Stop() {
+	C.secp256k1_stop()
+}
+
+/*
+int secp256k1_ecdsa_pubkey_create(
+    unsigned char *pubkey, int *pubkeylen,
+    const unsigned char *seckey, int compressed);
+*/
+
+/** Compute the public key for a secret key.
+ *  In:     compressed: whether the computed public key should be compressed
+ *          seckey:     pointer to a 32-byte private key.
+ *  Out:    pubkey:     pointer to a 33-byte (if compressed) or 65-byte (if uncompressed)
+ *                      area to store the public key.
+ *          pubkeylen:  pointer to int that will be updated to contains the pubkey's
+ *                      length.
+ *  Returns: 1: secret was valid, public key stores
+ *           0: secret was invalid, try again.
+ */
+
+//pubkey, seckey
+
+func GenerateKeyPair() ([]byte, []byte) {
+
+	pubkey_len := C.int(65)
+	const seckey_len = 32
+
+	var pubkey []byte = make([]byte, pubkey_len)
+	var seckey []byte = RandByte(seckey_len)
+
+	var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
+	var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
+
+	ret := C.secp256k1_ecdsa_pubkey_create(
+		pubkey_ptr, &pubkey_len,
+		seckey_ptr, 0)
+
+	if ret != C.int(1) {
+		return GenerateKeyPair() //invalid secret, try again
+	}
+	return pubkey, seckey
+}
+
+func GeneratePubKey(seckey []byte) ([]byte, error) {
+	pubkey_len := C.int(65)
+	const seckey_len = 32
+
+	var pubkey []byte = make([]byte, pubkey_len)
+
+	var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
+	var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
+
+	ret := C.secp256k1_ecdsa_pubkey_create(
+		pubkey_ptr, &pubkey_len,
+		seckey_ptr, 0)
+
+	if ret != C.int(1) {
+		return nil, errors.New("Unable to generate pubkey from seckey")
+	}
+
+	return pubkey, nil
+}
+
+/*
+*  Create a compact ECDSA signature (64 byte + recovery id).
+*  Returns: 1: signature created
+*           0: nonce invalid, try another one
+*  In:      msg:    the message being signed
+*           msglen: the length of the message being signed
+*           seckey: pointer to a 32-byte secret key (assumed to be valid)
+*           nonce:  pointer to a 32-byte nonce (generated with a cryptographic PRNG)
+*  Out:     sig:    pointer to a 64-byte array where the signature will be placed.
+*           recid:  pointer to an int, which will be updated to contain the recovery id.
+ */
+
+/*
+int secp256k1_ecdsa_sign_compact(const unsigned char *msg, int msglen,
+                                 unsigned char *sig64,
+                                 const unsigned char *seckey,
+                                 const unsigned char *nonce,
+                                 int *recid);
+*/
+
+func Sign(msg []byte, seckey []byte) ([]byte, error) {
+	//var nonce []byte = RandByte(32)
+	nonce := make([]byte, 32)
+	for i := range msg {
+		nonce[i] = msg[i] ^ seckey[i]
+	}
+
+	var sig []byte = make([]byte, 65)
+	var recid C.int
+
+	var msg_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&msg[0]))
+	var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
+	var nonce_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&nonce[0]))
+	var sig_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&sig[0]))
+
+	if C.secp256k1_ecdsa_seckey_verify(seckey_ptr) != C.int(1) {
+		return nil, errors.New("Invalid secret key")
+	}
+
+	ret := C.secp256k1_ecdsa_sign_compact(
+		msg_ptr, C.int(len(msg)),
+		sig_ptr,
+		seckey_ptr,
+		nonce_ptr,
+		&recid)
+
+	sig[64] = byte(int(recid))
+
+	if ret != C.int(1) {
+		// nonce invalid, retry
+		return Sign(msg, seckey)
+	}
+
+	return sig, nil
+
+}
+
+/*
+* Verify an ECDSA secret key.
+*  Returns: 1: secret key is valid
+*           0: secret key is invalid
+*  In:      seckey: pointer to a 32-byte secret key
+ */
+
+func VerifySeckeyValidity(seckey []byte) error {
+	if len(seckey) != 32 {
+		return errors.New("priv key is not 32 bytes")
+	}
+	var seckey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&seckey[0]))
+	ret := C.secp256k1_ecdsa_seckey_verify(seckey_ptr)
+	if int(ret) != 1 {
+		return errors.New("invalid seckey")
+	}
+	return nil
+}
+
+/*
+* Validate a public key.
+*  Returns: 1: valid public key
+*           0: invalid public key
+ */
+
+func VerifyPubkeyValidity(pubkey []byte) error {
+	if len(pubkey) != 65 {
+		return errors.New("pub key is not 65 bytes")
+	}
+	var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
+	ret := C.secp256k1_ecdsa_pubkey_verify(pubkey_ptr, 65)
+	if int(ret) != 1 {
+		return errors.New("invalid pubkey")
+	}
+
+	return nil
+}
+
+func VerifySignatureValidity(sig []byte) bool {
+	//64+1
+	if len(sig) != 65 {
+		return false
+	}
+	//malleability check, highest bit must be 1
+	if (sig[32] & 0x80) == 0x80 {
+		return false
+	}
+	//recovery id check
+	if sig[64] >= 4 {
+		return false
+	}
+
+	return true
+}
+
+//for compressed signatures, does not need pubkey
+func VerifySignature(msg []byte, sig []byte, pubkey1 []byte) error {
+	if msg == nil || sig == nil || pubkey1 == nil {
+		return errors.New("inputs must be non-nil")
+	}
+	if len(sig) != 65 {
+		return errors.New("invalid signature length")
+	}
+	if len(pubkey1) != 65 {
+		return errors.New("Invalid public key length")
+	}
+
+	//to enforce malleability, highest bit of S must be 0
+	//S starts at 32nd byte
+	if (sig[32] & 0x80) == 0x80 { //highest bit must be 1
+		return errors.New("Signature not malleable")
+	}
+
+	if sig[64] >= 4 {
+		return errors.New("Recover byte invalid")
+	}
+
+	// if pubkey recovered, signature valid
+	pubkey2, err := RecoverPubkey(msg, sig)
+	if err != nil {
+		return err
+	}
+	if len(pubkey2) != 65 {
+		return errors.New("Invalid recovered public key length")
+	}
+	if !bytes.Equal(pubkey1, pubkey2) {
+		return errors.New("Public key does not match recovered public key")
+	}
+
+	return nil
+}
+
+/*
+int secp256k1_ecdsa_recover_compact(const unsigned char *msg, int msglen,
+                                    const unsigned char *sig64,
+                                    unsigned char *pubkey, int *pubkeylen,
+                                    int compressed, int recid);
+*/
+
+/*
+ * Recover an ECDSA public key from a compact signature.
+ *  Returns: 1: public key succesfully recovered (which guarantees a correct signature).
+ *           0: otherwise.
+ *  In:      msg:        the message assumed to be signed
+ *           msglen:     the length of the message
+ *           compressed: whether to recover a compressed or uncompressed pubkey
+ *           recid:      the recovery id (as returned by ecdsa_sign_compact)
+ *  Out:     pubkey:     pointer to a 33 or 65 byte array to put the pubkey.
+ *           pubkeylen:  pointer to an int that will contain the pubkey length.
+ */
+
+//recovers the public key from the signature
+//recovery of pubkey means correct signature
+func RecoverPubkey(msg []byte, sig []byte) ([]byte, error) {
+	if len(sig) != 65 {
+		return nil, errors.New("Invalid signature length")
+	}
+
+	var pubkey []byte = make([]byte, 65)
+
+	var msg_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&msg[0]))
+	var sig_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&sig[0]))
+	var pubkey_ptr *C.uchar = (*C.uchar)(unsafe.Pointer(&pubkey[0]))
+
+	var pubkeylen C.int
+
+	ret := C.secp256k1_ecdsa_recover_compact(
+		msg_ptr, C.int(len(msg)),
+		sig_ptr,
+		pubkey_ptr, &pubkeylen,
+		C.int(0), C.int(sig[64]),
+	)
+
+	if ret == C.int(0) {
+		return nil, errors.New("Failed to recover public key")
+	} else if pubkeylen != C.int(65) {
+		return nil, errors.New("Impossible Error: Invalid recovered public key length")
+	} else {
+		return pubkey, nil
+	}
+	return nil, errors.New("Impossible Error: func RecoverPubkey has reached an unreachable state")
+}