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From 9c34fa05900b968d74f08ccf40917848a7be9441 Mon Sep 17 00:00:00 2001
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From: schneems <richard.schneeman+foo@gmail.com>
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Date: Tue, 24 Apr 2018 16:32:22 -0500
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Subject: [PATCH] Do not respond to http requests asking for a `file://`
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Based on CVE-2018-3760 when the Sprockets server is accidentally being used in production, an attacker can pass in a specifically crafted url that will allow them access to view every file on the system. If the file hit contains a compilable extension such as `.erb` then the code in that file will be executed.
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A Rails app will be using the Sprockets file server in production if they have accidentally configured their app to:
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```ruby
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config.assets.compile = true # Your app is vulnerable
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```
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It is highly recommended to not use the Sprockets server in production and to instead precompile assets to disk and serve them through a server such as Nginx or via the static file middleware that ships with rails `config.public_file_server.enabled = true`.
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This patch mitigates the issue, but explicitly disallowing any requests to any URI resources via the server.
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---
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test/test_server.rb | 7 +++++++
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1 files changed, 7 insertions(+), 0 deletions(-)
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diff --git a/test/test_server.rb b/test/test_server.rb
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index 66429533..19921e19 100644
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--- a/test/test_server.rb
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+++ b/test/test_server.rb
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@@ -331,6 +331,13 @@ def app
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assert_equal "", last_response.body
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end
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+ test "illegal access of a file asset" do
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+ absolute_path = fixture_path("server/app/javascripts")
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+
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+ get "assets/file:%2f%2f//#{absolute_path}/foo.js"
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+ assert_equal 403, last_response.status
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+ end
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+
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test "add new source to tree" do
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filename = fixture_path("server/app/javascripts/baz.js")
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