Added stderr > stdout redirection to sandbox options.

lib/exec_sandbox.rb

@@ -6,6 +6,7 @@
 require 'etc'
 require 'fcntl'
 require 'fileutils'
+require 'set'
 require 'tempfile'
 require 'tmpdir'
 

lib/exec_sandbox/sandbox.rb

@@ -92,8 +92,11 @@ def pull(from, to)
   # @option options [String] :out path to a file that is set as the child's
   #     stdout; if not set, the child will receive the write end of a pipe whose
   #     contents is returned in :out_data
+  # @option options [Symbol] :err :none closes the child's stderr, :out
+  #     redirects the child's stderr to stdout; by default, the child's stderr
+  #     is the same as the parent's
   # @return [Hash] the result of {Wait4#wait4}, plus an :out_data key if no :out
-  #                option is given
+  #                option is given  
   def run(command, options = {})
     limits = options[:limits] || {}
 
@@ -113,7 +116,14 @@ def run(command, options = {})
       out_rd, out_wr = IO.pipe
       io[:out] = out_wr
     end
-    io[:err] = STDERR unless options[:no_stderr]
+    case options[:err]
+    when :out
+      io[:err] = STDOUT
+    when :none
+      # Don't set io[:err], so the child's stderr will be closed.
+    else
+      io[:err] = STDERR
+    end
 
     pid = ExecSandbox::Spawn.spawn command, io, @principal, limits
     # Close the pipe ends that are meant to be used in the child.

lib/exec_sandbox/spawn.rb

@@ -28,32 +28,44 @@ def self.spawn(command, io = {}, principal = {}, resources = {})
   # @param [Hash] io associates file descriptors with IO objects or file paths;
   #                  all file descriptors not covered by io will be closed
   def self.limit_io(io)
+    # Sort the list of redirections by file descriptor number.
+    redirects = []
     [:in, :out, :err].each_with_index do |sym, fd_num|
-      if target = io.delete(sym)
-        io[fd_num] = target
+      if target = io[sym]
+        redirects << [fd_num, redirects.length, target]
       end
     end
     io.each do |k, v|
-      if v.respond_to?(:fileno)
-        if v.fileno != k
-          LibC.close k
-          LibC.dup2 v.fileno, k
+      if k.kind_of? Integer
+        redirects << [k, redirects.length, v]
+      end
+    end
+
+    # Perform the redirections.
+    redirects.sort!
+    redirects.each do |fd_num, _, target|    
+      if target.respond_to?(:fileno)
+        # IO stream.
+        if target.fileno != fd_num
+          LibC.close fd_num
+          LibC.dup2 target.fileno, fd_num
         end
       else
-        LibC.close k
-        open_fd = IO.sysopen(v, 'r+')
-        if open_fd != k
-          LibC.dup2 open_fd, k
+        # Filename string.
+        LibC.close fd_num
+        open_fd = IO.sysopen(target, 'r+')
+        if open_fd != fd_num
+          LibC.dup2 open_fd, fd_num
           LibC.close open_fd
         end
       end
     end
 
-    # Close all file descriptors.
+    # Close all file descriptors not in the redirection table.
+    redirected_fds = Set.new redirects.map(&:first)
     max_fd = LibC.getdtablesize
     0.upto(max_fd) do |fd|
-      next if io[fd]
-      LibC.close fd
+      LibC.close fd unless redirected_fds.include?(fd)
     end
   end
 

spec/exec_sandbox/sandbox_spec.rb

@@ -8,23 +8,44 @@
       @temp_in.close
       @temp_out = Tempfile.new 'exec_sandbox_rspec'
       @temp_out.close
-
-      ExecSandbox.use do |s|
-        @result = s.run bin_fixture(:duplicate), :in => @temp_in.path,
-                                                 :out => @temp_out.path
-      end
     end
     after do
       @temp_in.unlink
       @temp_out.unlink
     end
 
-    it 'should not crash' do
-      @result[:exit_code].should == 0
+    describe 'duplicate.rb' do
+      before do
+        ExecSandbox.use do |s|
+          @result = s.run bin_fixture(:duplicate), :in => @temp_in.path,
+                                                   :out => @temp_out.path
+        end
+      end
+
+      it 'should not crash' do
+        @result[:exit_code].should == 0
+      end
+
+      it 'should produce the correct result' do
+        File.read(@temp_out.path).should == "I/O test\nI/O test\n" 
+      end
     end
-
-    it 'should produce the correct result' do
-      File.read(@temp_out.path).should == "I/O test\nI/O test\n" 
+
+    describe 'count.rb' do
+      before do
+        ExecSandbox.use do |s|
+          @result = s.run [bin_fixture(:count), '9'], :in => @temp_in.path,
+              :out => @temp_out.path, :err => :out
+        end
+      end
+
+      it 'should not crash' do
+        @result[:exit_code].should == 0
+      end
+
+      it 'should produce the correct result' do
+        File.read(@temp_out.path).should == (1..9).map { |i| "#{i}\n" }.join('')
+      end
     end
   end
 
@@ -61,6 +82,22 @@
         @result[:out_data].should == "S" * buffer_size
       end
     end
+
+    describe 'count.rb' do
+      before do
+        ExecSandbox.use do |s|
+          @result = s.run [bin_fixture(:count), '9'], :err => :out
+        end
+      end
+
+      it 'should not crash' do
+        @result[:exit_code].should == 0
+      end
+
+      it 'should produce the correct result' do
+        @result[:out_data].should == (1..9).map { |i| "#{i}\n" }.join('')
+      end
+    end
   end
 
 

spec/exec_sandbox/spawn_spec.rb

@@ -69,6 +69,35 @@
         @status[:exit_code].should_not == 0
       end
     end
+
+    shared_examples_for 'count.rb' do
+      it 'should not crash' do
+        @status[:exit_code].should == 0
+      end
+
+      it 'should write successfully' do
+        @temp_out.open
+        begin
+          @temp_out.read.should == (1..9).map { |i| "#{i}\n" }.join('')
+        ensure
+          @temp_out.close
+        end
+      end
+    end
+
+    describe 'with file descriptor and stderr redirected to stdout' do
+      before do
+        File.open(@temp_in.path, 'r') do |in_io|
+          File.open(@temp_out.path, 'w') do |out_io|
+            pid = ExecSandbox::Spawn.spawn [bin_fixture(:count), '9'],
+                {:in => in_io, :out => out_io, :err => STDOUT}
+            @status = ExecSandbox::Wait4.wait4 pid
+          end
+        end
+      end
+
+      it_behaves_like 'count.rb'
+    end
   end
 
   describe '#spawn principal' do

spec/fixtures/count.rb

@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+
+# Counts from 1 to the first argument, and writes each number on a separate
+# line. Odd numbers go to STDOUT, even numbers go to STDERR. 
+# on both STDOUT and STDERR.
+
+limit = ARGV[0].to_i
+1.upto(limit) do |i|
+  file = (i % 2 == 0) ? STDERR : STDOUT
+  file.write "#{i}\n"
+  file.flush
+end