From d06f61136d67aea758845db5585642852d91ebdb Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Wed, 29 May 2024 17:08:15 -0300
Subject: [PATCH] allow using libsecp256k1 for signature verification in
 subscriptions.

---
 libsecp256k1/README.md | 25 +++++++++++++++++++++-
 pool.go                | 11 +++++++++-
 relay.go               | 47 ++++++++++++++++++++++++++----------------
 3 files changed, 63 insertions(+), 20 deletions(-)

diff --git a/libsecp256k1/README.md b/libsecp256k1/README.md
index f404202..7ec5563 100644
--- a/libsecp256k1/README.md
+++ b/libsecp256k1/README.md
@@ -1,4 +1,8 @@
-This is faster than the pure Go version:
+This wraps [libsecp256k1](https://github.com/bitcoin-core/secp256k1) with `cgo`.
+
+It doesn't embed the library or anything smart like that because I don't know how to do it, so you must have it installed in your system.
+
+It is faster than the pure Go version:
 
 ```
 goos: linux
@@ -8,3 +12,22 @@ cpu: AMD Ryzen 3 3200G with Radeon Vega Graphics
 BenchmarkSignatureVerification/btcec-4         	     145	   7873130 ns/op	  127069 B/op	     579 allocs/op
 BenchmarkSignatureVerification/libsecp256k1-4  	     502	   2314573 ns/op	  112241 B/op	     392 allocs/op
 ```
+
+To use it manually, just import. To use it inside the automatic verification that happens for subscriptions, set it up with a `SimplePool`:
+
+```go
+pool := nostr.NewSimplePool()
+pool.SignatureChecker = func (evt nostr.Event) bool {
+	ok, _ := libsecp256k1.CheckSignature(evt)
+	return ok
+}
+```
+
+Or directly to the `Relay`:
+
+```go
+relay := nostr.RelayConnect(context.Background(), "wss://relay.nostr.com", nostr.WithSignatureChecker(func (evt nostr.Event) bool {
+	ok, _ := libsecp256k1.CheckSignature(evt)
+	return ok
+}))
+```
diff --git a/pool.go b/pool.go
index 75cc9ed..4abf935 100644
--- a/pool.go
+++ b/pool.go
@@ -22,6 +22,9 @@ type SimplePool struct {
 
 	authHandler func(*Event) error
 	cancel      context.CancelFunc
+
+	// custom things not often used
+	SignatureChecker func(Event) bool
 }
 
 type DirectedFilters struct {
@@ -85,7 +88,13 @@ func (pool *SimplePool) EnsureRelay(url string) (*Relay, error) {
 		// we use this ctx here so when the pool dies everything dies
 		ctx, cancel := context.WithTimeout(pool.Context, time.Second*15)
 		defer cancel()
-		if relay, err = RelayConnect(ctx, nm); err != nil {
+
+		opts := make([]RelayOption, 0, 1)
+		if pool.SignatureChecker != nil {
+			opts = append(opts, WithSignatureChecker(pool.SignatureChecker))
+		}
+
+		if relay, err = RelayConnect(ctx, nm, opts...); err != nil {
 			return nil, fmt.Errorf("failed to connect: %w", err)
 		}
 
diff --git a/relay.go b/relay.go
index 2d4fc40..0715417 100644
--- a/relay.go
+++ b/relay.go
@@ -38,6 +38,7 @@ type Relay struct {
 	okCallbacks                   *xsync.MapOf[string, func(bool, string)]
 	writeQueue                    chan writeRequest
 	subscriptionChannelCloseQueue chan *Subscription
+	signatureChecker              func(Event) bool
 
 	// custom things that aren't often used
 	//
@@ -60,18 +61,14 @@ func NewRelay(ctx context.Context, url string, opts ...RelayOption) *Relay {
 		okCallbacks:                   xsync.NewMapOf[string, func(bool, string)](),
 		writeQueue:                    make(chan writeRequest),
 		subscriptionChannelCloseQueue: make(chan *Subscription),
+		signatureChecker: func(e Event) bool {
+			ok, _ := e.CheckSignature()
+			return ok
+		},
 	}
 
 	for _, opt := range opts {
-		switch o := opt.(type) {
-		case WithNoticeHandler:
-			r.notices = make(chan string)
-			go func() {
-				for notice := range r.notices {
-					o(notice)
-				}
-			}()
-		}
+		opt.ApplyRelayOption(r)
 	}
 
 	return r
@@ -89,16 +86,34 @@ func RelayConnect(ctx context.Context, url string, opts ...RelayOption) (*Relay,
 // When instantiating relay connections, some options may be passed.
 // RelayOption is the type of the argument passed for that.
 type RelayOption interface {
-	IsRelayOption()
+	ApplyRelayOption(*Relay)
 }
 
+var (
+	_ RelayOption = (WithNoticeHandler)(nil)
+	_ RelayOption = (WithSignatureChecker)(nil)
+)
+
 // WithNoticeHandler just takes notices and is expected to do something with them.
 // when not given, defaults to logging the notices.
 type WithNoticeHandler func(notice string)
 
-func (_ WithNoticeHandler) IsRelayOption() {}
+func (nh WithNoticeHandler) ApplyRelayOption(r *Relay) {
+	r.notices = make(chan string)
+	go func() {
+		for notice := range r.notices {
+			nh(notice)
+		}
+	}()
+}
 
-var _ RelayOption = (WithNoticeHandler)(nil)
+// WithSignatureChecker must be a function that checks the signature of an
+// event and returns true or false.
+type WithSignatureChecker func(Event) bool
+
+func (sc WithSignatureChecker) ApplyRelayOption(r *Relay) {
+	r.signatureChecker = sc
+}
 
 // String just returns the relay URL.
 func (r *Relay) String() string {
@@ -237,12 +252,8 @@ func (r *Relay) ConnectWithTLS(ctx context.Context, tlsConfig *tls.Config) error
 
 					// check signature, ignore invalid, except from trusted (AssumeValid) relays
 					if !r.AssumeValid {
-						if ok, err := env.Event.CheckSignature(); !ok {
-							errmsg := ""
-							if err != nil {
-								errmsg = err.Error()
-							}
-							InfoLogger.Printf("{%s} bad signature on %s; %s\n", r.URL, env.Event.ID, errmsg)
+						if ok := r.signatureChecker(env.Event); !ok {
+							InfoLogger.Printf("{%s} bad signature on %s\n", r.URL, env.Event.ID)
 							continue
 						}
 					}