Escape untrusted text when logging

This fixes a shell escape issue

[CVE-2022-30123]

lib/rack/common_logger.rb

@@ -54,7 +54,10 @@ def log(env, status, header, began_at)
         length,
         now - began_at ]
 
+      msg.gsub!(/[^[:print:]\n]/) { |c| "\\x#{c.ord}" }
+
       logger = @logger || env[RACK_ERRORS]
+
       # Standard library logger doesn't support write but it supports << which actually
       # calls to write on the log device without formatting
       if logger.respond_to?(:write)

lib/rack/lint.rb

@@ -295,7 +295,7 @@ def check_env(env)
       check_hijack env
 
       ## * The <tt>REQUEST_METHOD</tt> must be a valid token.
-      assert("REQUEST_METHOD unknown: #{env[REQUEST_METHOD]}") {
+      assert("REQUEST_METHOD unknown: #{env[REQUEST_METHOD].dump}") {
         env[REQUEST_METHOD] =~ /\A[0-9A-Za-z!\#$%&'*+.^_`|~-]+\z/
       }
 

test/spec_common_logger.rb

@@ -21,6 +21,10 @@
     [200,
      {"Content-Type" => "text/html", "Content-Length" => "0"},
      []]}
+  app_without_lint = lambda { |env|
+    [200,
+     { "content-type" => "text/html", "content-length" => length.to_s },
+     [obj]]}
 
   it "log to rack.errors by default" do
     res = Rack::MockRequest.new(Rack::CommonLogger.new(app)).get("/")
@@ -85,6 +89,14 @@ def with_mock_time(t = 0)
     (0..1).must_include duration.to_f
   end
 
+  it "escapes non printable characters except newline" do
+    logdev = StringIO.new
+    log = Logger.new(logdev)
+    Rack::MockRequest.new(Rack::CommonLogger.new(app_without_lint, log)).request("GET\b", "/hello")
+
+    logdev.string.must_match(/GET\\x8 \/hello/)
+  end
+
   def length
     123
   end

test/spec_lint.rb

@@ -96,6 +96,11 @@ def env(*args)
     }.must_raise(Rack::Lint::LintError).
       message.must_match(/REQUEST_METHOD/)
 
+    lambda {
+      Rack::Lint.new(nil).call(env("REQUEST_METHOD" => "OOPS?\b!"))
+    }.must_raise(Rack::Lint::LintError).
+      message.must_match(/OOPS\?\\/)
+
     lambda {
       Rack::Lint.new(nil).call(env("SCRIPT_NAME" => "howdy"))
     }.must_raise(Rack::Lint::LintError).