Cached Filename of Constant Length

nebhale · nebhale · commit b264792494ce · 2017-08-21T08:54:40.000-07:00
Previously, the name of a cached file was a sanitized version of the URI. Recently, a user starting caching a file that had a URI that was longer than 255 characters, causing issues with writing a filename of that length to the filesystem. The solution to this was to hash the URI (SHA256 in this case) in order to get a shorter and constant-length filename. [resolves cloudfoundry#484]
diff --git a/lib/java_buildpack/util/cache/cached_file.rb b/lib/java_buildpack/util/cache/cached_file.rb
@@ -13,8 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+require 'digest'
 require 'fileutils'
 require 'java_buildpack/util/cache'
+require 'java_buildpack/util/sanitizer'
 
 module JavaBuildpack
   module Util
@@ -24,6 +26,7 @@ module Cache
       #
       # Note: this class is thread-safe, however access to the cached files is not
       class CachedFile
+        include JavaBuildpack::Util
 
         # Creates an instance of the cached file.  Files created and expected by this class will all be rooted at
         # +cache_root+.
@@ -32,7 +35,7 @@ class CachedFile
         # @param [String] uri a uri which uniquely identifies the file in the cache
         # @param [Boolean] mutable whether the cached file should be mutable
         def initialize(cache_root, uri, mutable)
-          key            = URI.escape(uri.sanitize_uri, ':/&')
+          key            = Digest::SHA256.hexdigest uri.sanitize_uri
           @cached        = cache_root + "#{key}.cached"
           @etag          = cache_root + "#{key}.etag"
           @last_modified = cache_root + "#{key}.last_modified"
diff --git a/spec/java_buildpack/util/cache/cached_file_spec.rb b/spec/java_buildpack/util/cache/cached_file_spec.rb
@@ -15,6 +15,7 @@
 
 require 'spec_helper'
 require 'application_helper'
+require 'digest'
 require 'fileutils'
 require 'java_buildpack/util/cache/cached_file'
 
@@ -104,7 +105,7 @@
   end
 
   def cache_file(extension)
-    app_dir + "http%3A%2F%2Ffoo-uri%2F.#{extension}"
+    app_dir + "#{Digest::SHA256.hexdigest('http://foo-uri/')}.#{extension}"
   end
 
   def touch(extension, content = '')
diff --git a/spec/java_buildpack/util/cache/download_cache_spec.rb b/spec/java_buildpack/util/cache/download_cache_spec.rb
@@ -17,6 +17,7 @@
 require 'application_helper'
 require 'internet_availability_helper'
 require 'logging_helper'
+require 'digest'
 require 'fileutils'
 require 'java_buildpack/util/cache/download_cache'
 require 'net/http'
@@ -337,7 +338,7 @@
   end
 
   def cache_file(root, extension)
-    root + "http%3A%2F%2Ffoo-uri%2F.#{extension}"
+    root + "#{Digest::SHA256.hexdigest('http://foo-uri/')}.#{extension}"
   end
 
   def expect_complete_cache(root)
