sandbox postinstall

Closes Homebrew/homebrew#38479.

Signed-off-by: Xu Cheng <xucheng@me.com>

Library/Homebrew/cmd/postinstall.rb

@@ -1,5 +1,34 @@
+require "sandbox"
+
 module Homebrew
   def postinstall
-    ARGV.formulae.each { |f| f.run_post_install }
+    ARGV.formulae.each { |f| run_post_install(f) }
+  end
+
+  def run_post_install(formula)
+    args = %W[
+      nice #{RUBY_PATH}
+      -W0
+      -I #{HOMEBREW_LIBRARY_PATH}
+      --
+      #{HOMEBREW_LIBRARY_PATH}/postinstall.rb
+      #{formula.path}
+    ].concat(ARGV.options_only)
+
+    Utils.safe_fork do
+      if Sandbox.available? && ARGV.sandbox?
+        sandbox = Sandbox.new
+        sandbox.allow_write_temp_and_cache
+        sandbox.allow_write_log(formula)
+        sandbox.allow_write_cellar(formula)
+        sandbox.allow_write_path HOMEBREW_PREFIX
+        sandbox.deny_write_path HOMEBREW_LIBRARY
+        sandbox.deny_write_path HOMEBREW_REPOSITORY/".git"
+        sandbox.deny_write HOMEBREW_BREW_FILE
+        sandbox.exec(*args)
+      else
+        exec(*args)
+      end
+    end
   end
 end

Library/Homebrew/formula_installer.rb

@@ -9,6 +9,7 @@ require 'cleaner'
 require 'formula_cellar_checks'
 require 'install_renamed'
 require 'cmd/tap'
+require 'cmd/postinstall'
 require 'hooks/bottles'
 require 'debrew'
 require 'sandbox'
@@ -586,7 +587,7 @@ class FormulaInstaller
   end
 
   def post_install
-    formula.run_post_install
+    Homebrew.run_post_install(formula)
   rescue Exception => e
     opoo "The post-install step did not complete successfully"
     puts "You can try again using `brew postinstall #{formula.name}`"

Library/Homebrew/postinstall.rb

@@ -0,0 +1,21 @@
+old_trap = trap("INT") { exit! 130 }
+
+require "global"
+require "debrew"
+require "fcntl"
+require "socket"
+
+begin
+  error_pipe = UNIXSocket.open(ENV["HOMEBREW_ERROR_PIPE"], &:recv_io)
+  error_pipe.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)
+
+  trap("INT", old_trap)
+
+  formula = ARGV.formulae.first
+  formula.extend(Debrew::Formula) if ARGV.debug?
+  formula.run_post_install
+rescue Exception => e
+  Marshal.dump(e, error_pipe)
+  error_pipe.close
+  exit! 1
+end