Ruby: Could not find a temporary directory

Question

I am getting some 500 errors in my Passenger Rails app. When looking at the log it appears passenger cannot access the /tmp dir. I have validated that it is there and has RW access to root, and then tried www-data. What is going on here?

 2014-01-14 16:01:16.6573 20624/7fa7c8806700 Pool2/SmartSpawner.h:301 ]: Preloader for /var/www/socialrest_homepage started on PID 20686, listening on unix:/tmp/passenger.1.0.20618/generation-0/backends/preloader.20686
App 20704 stdout: 
[Tue Jan 14 16:01:17 2014] [error] [client 168.215.171.129] Premature end of script headers: 
App 20686 stderr: /usr/local/rvm/rubies/ruby-2.0.0-p353/lib/ruby/2.0.0/tmpdir.rb:34:in `tmpdir': could not find a temporary directory (ArgumentError)
App 20686 stderr:   from /usr/local/rvm/gems/ruby-2.0.0-p353/gems/passenger-4.0.33/lib/phusion_passenger/utils/tmpio.rb:17:in `new'
App 20686 stderr:   from /usr/local/rvm/gems/ruby-2.0.0-p353/gems/passenger-4.0.33/lib/phusion_passenger/utils/tee_input.rb:99:in `initialize'
App 20686 stderr:   from /usr/local/rvm/gems/ruby-2.0.0-p353/gems/passenger-4.0.33/lib/phusion_passenger/rack/thread_handler_extension.rb:55:in `new'
App 20686 stderr:   from /usr/local/rvm/gems/ruby-2.0.0-p353/gems/passenger-4.0.33/lib/phusion_passenger/rack/thread_handler_extension.rb:55:in `process_request'
App 20686 stderr:   from /usr/local/rvm/gems/ruby-2.0.0-p353/gems/passenger-4.0.33/lib/phusion_passenger/request_handler/thread_handler.rb:141:in `accept_and_process_next_request'
App 20686 stderr:   from /usr/local/rvm/gems/ruby-2.0.0-p353/gems/passenger-4.0.33/lib/phusion_passenger/request_handler/thread_handler.rb:109:in `main_loop'
App 20686 stderr:   from /usr/local/rvm/gems/ruby-2.0.0-p353/gems/passenger-4.0.33/lib/phusion_passenger/request_handler.rb:440:in `block (3 levels) in start_threads'
[ 2014-01-14 16:01:21.0163 20624/7fa7cb242700 Pool2/Pool.h:776 ]: Process (pid=20704, group=/var/www/socialrest_homepage#default) no longer exists! Detaching it from the pool.
App 20720 stdout:

Here are my current /tmp, and config/environment.rb ownerships:

drwxrwxrwx   5 root root 4.0K Jan 14 16:01 tmp

-rwxr-xr-x  1 root root  196 Jan 13 20:06 environment.rb

Mcadams

Answer 1

-- Updated -- Secure answer is to use chmod +t /tmp

-- Previous answer --

Not sure what happened here, but I believe it had something to do with the /tmp folder permissions. I thought my /tmp folder was corrupted so I looked around about deleteing that folder and restoring it (I wasn't sure if this folder was especially significant about the way it was created). I found this source that suggested you can simply make the /tmp folder, just as you would any other folder, and then do a chmod 1777 on the newly created folder.

So, instead of deleting my current /tmp, I ran this chmod command and everything appeared to work.

What is strange to me is that I had previously done a chmod 777 and that caused the folder to not work. Weird...

Mcadams

life saver. Hit this issue only for certain pages just before start of user testing. First result in bing and resolved it right away. Thanks for sharing – Guardado

chmod 777 /tmp removes the sticky bit from the directory. Without the sticky bit, anyone can remove, rename or replace a file from/in the directory at any time. That's a severe security issue. – Ileus

An explanation why chmod 777 /tmp is a bad idea: security.stackexchange.com/questions/9115/… – Ileus

Answer 2

The most significant part of the stack trace is the error message:

could not find a temporary directory (ArgumentError)

When you tell Ruby >= 2.0 to create a temporary file, it looks for a directory where it can create a file in a secure way. Creating temporary files in a directory where anybody can replace the file while you are working on it would be a big (and common) security hole!

You have two possibilities:

• Tell ruby where it can securely create temporary files by setting one of the environment variables TMPDIR or TMP or TEMP to a directory that is secure.

• Fix up the permissions on a directory that ruby tries to use. Directories that Ruby tries to use by default: systempdir ("/tmp") and the current directory

Ruby deems a directory secure if the directory is either not world writable or has the sticky bit set. (Do not confuse the sticky bit (t) with the seteuid/setgid bit (s)!)

So, instead of setting TMPDIR, you might either make your working directory not world writable or do:

chmod +t /tmp

The manual page of chmod explains the use of the sticky bit:

[It] prevents unprivileged users from removing or renaming a file in the directory unless they own the file or the directory; this is called the restricted deletion flag for the directory, and is commonly found on world-writable directories like /tmp.

Here is what can happen without the sticky bit: https://security.stackexchange.com/questions/9115/can-you-describe-a-real-life-scenario-of-exploiting-sticky-bits/108666#108666

See also: https://blog.diacode.com/fixing-temporary-dir-problems-with-ruby-2

Ileus

Yep, that's it. 777 doesn't work. If you do a 777 on your /tmp dir, you can fix this with the chmod +t /tmp @Ileus suggested. – Dimorphism

Answer 3

ls -l /

$drwxrwxrw   9 root     root      4096 Jun 26 11:34 tmp

If you don't see that t at the end of the permissions column '/tmp'

chmod o+t /tmp
chmod 1777 /tmp    
$ ls -l / 
drwxrwxrwt   9 root     root      4096 Jun 26 11:35 tmp

reason is Fixing temporary dir problems with Ruby 2

Rejoin