Fixes finterprint filter handling of timestamp field

Fixes #1572

lib/logstash/filters/fingerprint.rb

@@ -90,15 +90,15 @@ class LogStash::Filters::Fingerprint < LogStash::Filters::Base
   def anonymize_openssl(data)
     digest = encryption_algorithm()
     # in JRuby 1.7.11 outputs as ASCII-8BIT
-    OpenSSL::HMAC.hexdigest(digest, @key, data).force_encoding(Encoding::UTF_8)
+    OpenSSL::HMAC.hexdigest(digest, @key, data.to_s).force_encoding(Encoding::UTF_8)
   end
 
   def anonymize_murmur3(value)
     case value
       when Fixnum
         MurmurHash3::V32.int_hash(value)
-      when String
+      else
-        MurmurHash3::V32.str_hash(value)
+        MurmurHash3::V32.str_hash(value.to_s)
     end
   end
 

spec/filters/fingerprint.rb

@@ -164,4 +164,39 @@ describe LogStash::Filters::Fingerprint do
     end
   end
 
+  context 'Timestamps' do
+    epoch_time = Time.at(0).gmtime
+
+    describe 'OpenSSL Fingerprinting' do
+      config <<-CONFIG
+        filter {
+          fingerprint {
+            source => ['@timestamp']
+            key    => '0123'
+            method => 'SHA1'
+          }
+        }
+      CONFIG
+
+      sample("@timestamp" => epoch_time) do
+        insist { subject["fingerprint"] } == '1d5379ec92d86a67cfc642d55aa050ca312d3b9a'
+      end
+    end
+
+    describe 'MURMUR3 Fingerprinting' do
+      config <<-CONFIG
+        filter {
+          fingerprint {
+            source => ['@timestamp']
+            method => 'MURMUR3'
+          }
+        }
+      CONFIG
+
+      sample("@timestamp" => epoch_time) do
+        insist { subject["fingerprint"] } == 743372282
+      end
+    end
+  end
+
 end