96 lines
2.7 KiB
Go
96 lines
2.7 KiB
Go
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//go:build libsecp256k1
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package nostr
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/*
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#cgo LDFLAGS: -lsecp256k1
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#include <secp256k1.h>
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#include <secp256k1_schnorrsig.h>
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#include <secp256k1_extrakeys.h>
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*/
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import "C"
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import (
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"crypto/rand"
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"crypto/sha256"
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"encoding/hex"
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"errors"
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"fmt"
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"unsafe"
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"github.com/btcsuite/btcd/btcec/v2/schnorr"
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)
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// CheckSignature checks if the signature is valid for the id
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// (which is a hash of the serialized event content).
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// returns an error if the signature itself is invalid.
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func (evt Event) CheckSignature() (bool, error) {
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var pk [32]byte
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_, err := hex.Decode(pk[:], []byte(evt.PubKey))
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if err != nil {
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return false, fmt.Errorf("event pubkey '%s' is invalid hex: %w", evt.PubKey, err)
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}
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var sig [64]byte
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_, err = hex.Decode(sig[:], []byte(evt.Sig))
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if err != nil {
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return false, fmt.Errorf("event signature '%s' is invalid hex: %w", evt.Sig, err)
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}
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msg := sha256.Sum256(evt.Serialize())
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var xonly C.secp256k1_xonly_pubkey
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if C.secp256k1_xonly_pubkey_parse(globalSecp256k1Context, &xonly, (*C.uchar)(unsafe.Pointer(&pk[0]))) != 1 {
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return false, fmt.Errorf("failed to parse xonly pubkey")
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}
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res := C.secp256k1_schnorrsig_verify(globalSecp256k1Context, (*C.uchar)(unsafe.Pointer(&sig[0])), (*C.uchar)(unsafe.Pointer(&msg[0])), 32, &xonly)
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return res == 1, nil
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}
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// Sign signs an event with a given privateKey.
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func (evt *Event) Sign(secretKey string, signOpts ...schnorr.SignOption) error {
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sk, err := hex.DecodeString(secretKey)
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if err != nil {
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return fmt.Errorf("Sign called with invalid secret key '%s': %w", secretKey, err)
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}
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if evt.Tags == nil {
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evt.Tags = make(Tags, 0)
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}
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var keypair C.secp256k1_keypair
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if C.secp256k1_keypair_create(globalSecp256k1Context, &keypair, (*C.uchar)(unsafe.Pointer(&sk[0]))) != 1 {
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return errors.New("failed to parse private key")
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}
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var xonly C.secp256k1_xonly_pubkey
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var pk [32]byte
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C.secp256k1_keypair_xonly_pub(globalSecp256k1Context, &xonly, nil, &keypair)
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C.secp256k1_xonly_pubkey_serialize(globalSecp256k1Context, (*C.uchar)(unsafe.Pointer(&pk[0])), &xonly)
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evt.PubKey = hex.EncodeToString(pk[:])
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h := sha256.Sum256(evt.Serialize())
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var sig [64]byte
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var random [32]byte
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rand.Read(random[:])
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if C.secp256k1_schnorrsig_sign32(globalSecp256k1Context, (*C.uchar)(unsafe.Pointer(&sig[0])), (*C.uchar)(unsafe.Pointer(&h[0])), &keypair, (*C.uchar)(unsafe.Pointer(&random[0]))) != 1 {
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return errors.New("failed to sign message")
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}
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evt.ID = hex.EncodeToString(h[:])
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evt.Sig = hex.EncodeToString(sig[:])
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return nil
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}
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var globalSecp256k1Context *C.secp256k1_context
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func init() {
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globalSecp256k1Context = C.secp256k1_context_create(C.SECP256K1_CONTEXT_SIGN | C.SECP256K1_CONTEXT_VERIFY)
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if globalSecp256k1Context == nil {
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panic("failed to create secp256k1 context")
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}
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}
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