From 9775016bf19c871d515bec293c163f9f27adef77 Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Sun, 15 Jan 2023 22:00:38 -0300
Subject: [PATCH] implement nip-42 AUTH event validation.

---
 nip42/nip42.go | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 nip42/nip42.go

diff --git a/nip42/nip42.go b/nip42/nip42.go
new file mode 100644
index 0000000..a161e30
--- /dev/null
+++ b/nip42/nip42.go
@@ -0,0 +1,40 @@
+package nip42
+
+import (
+	"net/url"
+	"time"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+func ValidateAuthEvent(event *nostr.Event, challenge string, relayURL string) (pubkey string, ok bool) {
+	if ok, _ := event.CheckSignature(); ok == false {
+		return "", false
+	}
+	if event.Kind != 22242 {
+		return "", false
+	}
+
+	now := time.Now()
+	if event.CreatedAt.After(now.Add(10*time.Minute)) || event.CreatedAt.Before(now.Add(-10*time.Minute)) {
+		return "", false
+	}
+
+	if event.Tags.GetFirst([]string{"challenge", challenge}) == nil {
+		return "", false
+	}
+
+	expected, err1 := url.Parse(relayURL)
+	found, err2 := url.Parse(event.Tags.GetFirst([]string{"relay", ""}).Value())
+	if err1 != nil || err2 != nil {
+		return "", false
+	} else {
+		if expected.Scheme != found.Scheme ||
+			expected.Host != found.Host ||
+			expected.Path != found.Path {
+			return "", false
+		}
+	}
+
+	return event.PubKey, true
+}