From db6c87a86bab84ebbe7b3fdcef41a81f915d45c8 Mon Sep 17 00:00:00 2001
From: Yuki Kishimoto <yukikishimoto@protonmail.com>
Date: Mon, 29 Jan 2024 15:59:45 +0100
Subject: [PATCH] sdk: add `max_num_tags` limit

---
 crates/nostr-sdk/src/relay/limits.rs |  9 ++++++---
 crates/nostr-sdk/src/relay/mod.rs    | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/crates/nostr-sdk/src/relay/limits.rs b/crates/nostr-sdk/src/relay/limits.rs
index 13503010e..4a686e734 100644
--- a/crates/nostr-sdk/src/relay/limits.rs
+++ b/crates/nostr-sdk/src/relay/limits.rs
@@ -19,7 +19,10 @@ impl Default for Limits {
             messages: MessagesLimits {
                 max_size: 5_250_000,
             },
-            events: EventsLimits { max_size: 70_000 },
+            events: EventsLimits {
+                max_size: 70_000,
+                max_num_tags: 2_000,
+            },
         }
     }
 }
@@ -36,8 +39,8 @@ pub struct MessagesLimits {
 pub struct EventsLimits {
     /// Maximum size of normalised JSON, in bytes
     pub max_size: u32,
-    // /// Maximum number of tags allowed
-    // pub max_num_tags: u16,
+    /// Maximum number of tags allowed
+    pub max_num_tags: u16,
     // Maximum size for tag values, in bytes
     // pub max_tag_val_size: u16,
 }
diff --git a/crates/nostr-sdk/src/relay/mod.rs b/crates/nostr-sdk/src/relay/mod.rs
index b49c6dba6..4e947c4d8 100644
--- a/crates/nostr-sdk/src/relay/mod.rs
+++ b/crates/nostr-sdk/src/relay/mod.rs
@@ -144,6 +144,14 @@ pub enum Error {
         /// Max event size
         max_size: usize,
     },
+    /// Too many tags
+    #[error("Received event with too many tags: tags={size}, max_tags={max_size}")]
+    TooManyTags {
+        /// Tags num
+        size: usize,
+        /// Max tags num
+        max_size: usize,
+    },
 }
 
 /// Relay connection status
@@ -795,11 +803,27 @@ impl Relay {
                         tracing::trace!("Received message from {}: {:?}", relay.url, msg);
 
                         if let RawRelayMessage::Event { event, .. } = &msg {
+                            // Check event size
                             let size: usize = event.to_string().as_bytes().len();
                             let max_size: usize = relay.limits.events.max_size as usize;
                             if size > max_size {
                                 return Err(Error::EventTooLarge { size, max_size });
                             }
+
+                            // Check tags limit
+                            if let Some(tags) = event.get("tags") {
+                                if let Some(tags) = tags.as_array() {
+                                    let size: usize = tags.len();
+                                    let max_num_tags: usize =
+                                        relay.limits.events.max_num_tags as usize;
+                                    if size > max_num_tags {
+                                        return Err(Error::TooManyTags {
+                                            size,
+                                            max_size: max_num_tags,
+                                        });
+                                    }
+                                }
+                            }
                         }
 
                         if let Err(err) = relay