Play with a running ruby process safely

reval

#!/usr/bin/env bash
#
# ./reval "pid" "ruby code"

rm /tmp/ruby.out 2> /dev/null
expr=$(echo $2 | base64)
(
  echo "set breakpoint pending on";
  echo "tb rb_funcallv"
  echo "commands"
  echo "call (void*)rb_eval_string_protect(\"require'base64';a=eval(Base64.decode64('$expr'));File.write('/tmp/ruby.out',a.to_s)\", (void*)0)"
  echo "d"
  echo "end"
  echo "c"
) | gdb -p $1 &> /dev/null
if [ -f /tmp/ruby.out ]; then
  cat /tmp/ruby.out
else
  echo "Execution failed"
fi
root@staging-01:/tmp/test# vi reval
root@staging-01:/tmp/test# ./reval 349 "Octopus::Proxy.nil?"
false
root@staging-01:/tmp/test# cat reval
#!/usr/bin/env bash
#
# ./reval "pid" "ruby code"
rm /tmp/ruby.out 2> /dev/null
expr=$(echo $2 | base64)
(
  echo "set breakpoint pending on";
  echo "tb rb_funcallv"
  echo "commands"
  echo "call (void*)rb_eval_string_protect(\"require'base64';a=eval(Base64.decode64('$expr'));File.write('/tmp/ruby.out',a.to_s)\", (void*)0)"
  echo "d"
  echo "end"
  echo "c"
) | gdb -p $1 &> /dev/null
if [ -f /tmp/ruby.out ]; then
  cat /tmp/ruby.out
  echo ""
else
  echo "Execution failed"
fi