Add message size limit of 64 keys.

README.md

@@ -55,7 +55,7 @@ Eg: `pigeon identity show` becomes `./pigeon-cli show`.
  - [X] Run Flog / Flay and friends to find duplications. Will aid in port to other languages.
  - [X] Make all methods private except those required for the CLI.
  - [X] Add Lipmaa links like the Bamboo folks do.
- - [ ] Set a max message size.
+ - [X] Set a max message size.
  - [ ] Make the switch to LevelDB, RocksDB, [UNQLite](https://unqlite.org/features.html) or similar (currently using Ruby PStore).
  - [ ] Make CLI names consistent with API names. Eg: find vs. read.
  - [ ] Create regexes in ::Lexer using strings and Regexp.new() for cleaner regexes.

dist/pigeon/message.rb

@@ -5,9 +5,10 @@ module Pigeon
     attr_reader :author, :kind, :body, :signature, :depth, :lipmaa, :prev
 
     class VerificationError < StandardError; end
+    class MessageSizeError < StandardError; end
 
     VERFIY_ERROR = "Expected field `%s` to equal %s, got: %s"
-
+    MSG_SIZE_ERROR = "Messages cannot have more than 64 keys. Got %s."
     # Store a message that someone (not the LocalIdentity)
     # has authored.
     def self.ingest(author:, body:, depth:, kind:, lipmaa:, prev:, signature:)
@@ -54,6 +55,11 @@ module Pigeon
     end
 
     def verify_counted_fields
+      key_count = body.count
+      if key_count > 64
+        msg = MSG_SIZE_ERROR % key_count
+        raise MessageSizeError, msg
+      end
       count = store.get_message_count_for(author.multihash)
       expected_prev = store.get_message_by_depth(author.multihash, count - 1) || Pigeon::NOTHING
       assert("depth", count, depth)

spec/pigeon/message_spec.rb

@@ -94,6 +94,18 @@ RSpec.describe Pigeon::Message do
   end
 
   it "verifies accuracy of Lipmaa links"
+
+  it "does not allow message with more than 64 keys" do
+    error = "Messages cannot have more than 64 keys. Got 65."
+    body = {}
+    65.times do
+      body[SecureRandom.hex(6)] = SecureRandom.hex(6)
+    end
+    expect do
+      create_message(body)
+    end.to raise_error(Pigeon::Message::MessageSizeError, error)
+  end
+
   it "verifies accuracy of signatures" do
     # === Initial setup
     Pigeon::LocalIdentity.current