fix: translate unicode domain names to Punycode for compatibility with DNS (#2823)

Gemfile

@@ -5,6 +5,7 @@ gem "authie"
 gem "autoprefixer-rails"
 gem "bcrypt"
 gem "chronic"
+gem "domain_name"
 gem "dotenv"
 gem "dynamic_form"
 gem "encrypto_signo"

Gemfile.lock

@@ -101,6 +101,7 @@ GEM
     date (3.3.4)
     deep_merge (1.2.2)
     diff-lcs (1.5.0)
+    domain_name (0.6.20240107)
     dotenv (3.0.2)
     dynamic_form (1.3.1)
       actionview (> 5.2.0)
@@ -334,6 +335,7 @@ DEPENDENCIES
   chronic
   coffee-rails (~> 5.0)
   database_cleaner
+  domain_name
   dotenv
   dynamic_form
   encrypto_signo

app/lib/dns_resolver.rb

@@ -17,10 +17,8 @@ class DNSResolver
   # @param [String] name
   # @return [Array<String>]
   def a(name)
-    dns do |dns|
+    get_resources(name, Resolv::DNS::Resource::IN::A).map do |s|
-      dns.getresources(name, Resolv::DNS::Resource::IN::A).map do |s|
+      s.address.to_s
-        s.address.to_s
-      end
     end
   end
 
@@ -29,10 +27,8 @@ class DNSResolver
   # @param [String] name
   # @return [Array<String>]
   def aaaa(name)
-    dns do |dns|
+    get_resources(name, Resolv::DNS::Resource::IN::AAAA).map do |s|
-      dns.getresources(name, Resolv::DNS::Resource::IN::AAAA).map do |s|
+      s.address.to_s
-        s.address.to_s
-      end
     end
   end
 
@@ -41,10 +37,8 @@ class DNSResolver
   # @param [String] name
   # @return [Array<String>]
   def txt(name)
-    dns do |dns|
+    get_resources(name, Resolv::DNS::Resource::IN::TXT).map do |s|
-      dns.getresources(name, Resolv::DNS::Resource::IN::TXT).map do |s|
+      s.data.to_s.strip
-        s.data.to_s.strip
-      end
     end
   end
 
@@ -53,10 +47,8 @@ class DNSResolver
   # @param [String] name
   # @return [Array<String>]
   def cname(name)
-    dns do |dns|
+    get_resources(name, Resolv::DNS::Resource::IN::CNAME).map do |s|
-      dns.getresources(name, Resolv::DNS::Resource::IN::CNAME).map do |s|
+      s.name.to_s.downcase
-        s.name.to_s.downcase
-      end
     end
   end
 
@@ -65,16 +57,14 @@ class DNSResolver
   # @param [String] name
   # @return [Array<Array<Integer, String>>]
   def mx(name)
-    dns do |dns|
+    records = get_resources(name, Resolv::DNS::Resource::IN::MX).map do |m|
-      records = dns.getresources(name, Resolv::DNS::Resource::IN::MX).map do |m|
+      [m.preference.to_i, m.exchange.to_s]
-        [m.preference.to_i, m.exchange.to_s]
+    end
-      end
+    records.sort do |a, b|
-      records.sort do |a, b|
+      if a[0] == b[0]
-        if a[0] == b[0]
+        [-1, 1].sample
-          [-1, 1].sample
+      else
-        else
+        a[0] <=> b[0]
-          a[0] <=> b[0]
-        end
       end
     end
   end
@@ -90,7 +80,7 @@ class DNSResolver
       (parts.size - 1).times do |n|
         d = parts[n, parts.size - n + 1].join(".")
 
-        records = dns.getresources(d, Resolv::DNS::Resource::IN::NS).map do |s|
+        records = get_resources(d, Resolv::DNS::Resource::IN::NS).map do |s|
           s.name.to_s
         end
 
@@ -124,6 +114,13 @@ class DNSResolver
     end
   end
 
+  def get_resources(name, type)
+    encoded_name = DomainName::Punycode.encode_hostname(name)
+    dns do |dns|
+      dns.getresources(encoded_name, type)
+    end
+  end
+
   class << self
 
     # Return a resolver which will use the nameservers for the given domain

spec/lib/dns_resolver_spec.rb

@@ -14,6 +14,9 @@ RSpec.describe DNSResolver do
     it "returns a list of IP addresses" do
       expect(resolver.a("www.test.postalserver.io").sort).to eq ["1.2.3.4", "2.3.4.5"]
     end
+    it "resolves a domain name containing an emoji" do
+      expect(resolver.a("☺.test.postalserver.io").sort).to eq ["3.4.5.6"]
+    end
   end
 
   describe "#aaaa" do