Normalise license MD5 values

License files uploaded in the UI always have newlines as separators, with a
single trailing newline.

Licenses pasted in the text box will have newlines replaced by \r\n by the
browser, and may have zero trailing newlines, or many.

Normalising these to a canonical form lets us match against the license app more
efficiently.

app/models/license.rb

@@ -131,6 +131,12 @@ class License < ActiveRecord::Base
     self.data = file.read
   end
 
+  def md5
+    normalized_data = self.data.gsub("\r\n", "\n").gsub(/\n+$/, '') + "\n"
+
+    Digest::MD5.hexdigest(normalized_data)
+  end
+
   def license
     return nil unless self.data
 

lib/gitlab/usage_data.rb

@@ -82,7 +82,7 @@ module Gitlab
 
         if license
           usage_data[:edition] = license_edition(license.plan)
-          usage_data[:license_md5] = Digest::MD5.hexdigest(license.data)
+          usage_data[:license_md5] = license.md5
           usage_data[:historical_max_users] = ::HistoricalData.max_historical_user_count
           usage_data[:licensee] = license.licensee
           usage_data[:license_user_count] = license.restricted_user_count

spec/models/license_spec.rb

@@ -315,6 +315,26 @@ describe License do
     end
   end
 
+  describe "#md5" do
+    it "returns the same MD5 for licenses with carriage returns and those without" do
+      other_license = build(:license, data: license.data.gsub("\n", "\r\n"))
+
+      expect(other_license.md5).to eq(license.md5)
+    end
+
+    it "returns the same MD5 for licenses with trailing newlines and those without" do
+      other_license = build(:license, data: license.data.chomp)
+
+      expect(other_license.md5).to eq(license.md5)
+    end
+
+    it "returns the same MD5 for licenses with multiple trailing newlines and those with a single trailing newline" do
+      other_license = build(:license, data: "#{license.data}\n\n\n")
+
+      expect(other_license.md5).to eq(license.md5)
+    end
+  end
+
   describe "#license" do
     context "when no data is provided" do
       before do