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Default umask (permissions) is not applied #352

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simonbuchan opened this Issue May 12, 2016 · 17 comments

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Reference: http://www.cyberciti.biz/tips/understanding-linux-unix-umask-value-usage.html

My current install has this in /etc/profile:

# The default umask is now handled by pam_umask.
# See pam_umask(8) and /etc/login.defs.

And, indeed /etc/profile has UMASK> > 022, but:

simon@QOF:~$ umask
0000

The effect of this is that new files are created with 666 and dirs with 777 permissions:

simon@QOF:~$ touch file
simon@QOF:~$ mkdir dir
simon@QOF:~$ ll -d file dir
drwxrwxrwx 2 simon simon 0 May 12 22:54 dir/
-rw-rw-rw- 1 simon simon 0 May 12 22:54 file

This mostly isn't a real problem since UoW doesn't have to care about multiple users, it largely shows up as ls showing dirs with an ugly green background, but it could freak out some tools, similar to ssh wanting 600 on your private keys.

Simplest fix would probably be to dump a umask 022 in /etc/profile, but it seems there's a bunch of stuff in that /etc/login.defs

Easy workaound is to add a umask to your ~/.bashrc

May be somewhat related to #167 , /etc/profile is supposed to be read if bash is a login shell - but even bash.exe --login doesn't seem to use pam_umask

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benhillis commented May 13, 2016

@simonbuchan Thanks for reporting this. I think there are a couple things going on here. I verified that when bash.exe --login is launched /bin/bash does read from /etc/profile. I dumped my default /etc/profile and noticed a comment that:

# The default umask is now handled by pam_umask.
# See pam_umask(8) and /etc/login.defs.

When you run "bash.exe --login" that translates into "/bin/bash --login". We don't run the /bin/login binary and I'm assuming that's what normally sets up pam_umask. Did you try adding a new umask to value to your /etc/profile? It should work (when using bash.exe --login).

Yep, umask in both /etc/profile and ~/.profile run with both bash.exe --login and bash -c "bash --login".
Interestingly, if I revert the umask command and do bash.exe -c "sudo login" then umask is 0002 - no idea where that is coming from!

0xMF commented May 26, 2016

Please ensure umask is never 0000 no matter how bash is started.

I understand users can set umask to saner defaults in their own bashrc files but it means whatever directories and files auto-installed by scripts after WSL setup and user first bash run till the bad umask was discovered now have to be changed to sane defaults. This is exacerbated in git-based repos because git will track the change of perms to saner defaults as a (needless) change thereby status of git repo becomes dirty which simply put is both: confusing and annoying.

@0xMF don't worry, git only tracks +x, and the .bashrc changes are mentioned as a workaround

neurogenesis commented Oct 16, 2016 edited

This also causes problems for zsh (compinit/compaudit). If you use a tool like antigen the directory permissions will throw shell errors when compinit/compaudit (command completion) is loaded.

Essentially any tool that performs basic checking for "other" write/read permissions will fail.

For anyone else trying to use dropbox, careful with symlinks to the windows /mnt/c/.... You'll likely run into a lot of problems. Unfortunately, dropbox for linux doesn't work yet either (because of the /proc/vmstat issue: #1071 ).

Hello, It's very strange. If I run ./configure, I found that the Makefile in the dir and sub dir only has permission rw no x. So some middle product didn't output, ./configure is right, but can't do make.

It's a big problem.

/usr/bin/m4: m4_esyscmd subprocess failed: Operation not permitted
/usr/bin/m4:configure.ac:489: cannot run command `./scripts/version.sh': Operation not permitted

lilred commented Dec 1, 2016

I have put this in my ~/.profile in the meantime:

# Note: Bash on Windows does not currently apply umask properly.
if [ "$(umask)" = "0000" ]; then
>   umask 022
fi

@benhillis: if you have time to entertain my curiosity - is there a particular reason you don't run /bin/login?

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benhillis commented Dec 1, 2016

@lilred - good question. Historically there have been a couple of reasons. When we first released /bin/bash worked but other shells (zsh for example) didn't work very well and we didn't want users to set their default shell to something that didn't work and get into a bad state. There's also potential strangeness around running bash.exe and zsh being launched.

That being said, running login would actually make a lot of things simpler for us.  Currently our init daemon has to do many of the things that /bin/login normally does. We're doing some design for the next release of Windows and I'll take a look at this and see if it would make sense to potentially switch things over now.

If you'd like to play around with using login there's a way you can use it now.

lxrun.exe /setdefaultuser root
bash.exe -c "/bin/login -f username"

lilred commented Dec 1, 2016

This is fantastic, thanks for the insight. I will change my Bash shortcut to this and report back if I hit any issues.

With /bin/login I do get umask returning 002, which is probably "good enough" to close this, but it's still not getting the "correct" default value 022 from /etc/login.defs line 151, which may be a thing.

Also it seems to start faster?!

One thing to be aware of is it doesn't extend PATH with the windows path.

@sunilmut sunilmut removed the network label Dec 4, 2016

@agross agross added a commit to agross/dotfiles that referenced this issue Feb 14, 2017

@agross agross Set umask for Bash on Windows, Microsoft/BashOnWindows#352 f92e4b6

@jackchammons Does closing this mean the default setup will now set a umask? /bin/login is not a default setup.

Member

jackchammons commented Feb 15, 2017

The current behavior is expected. We will be reevaluating where umask gets set in an future release.

hughbe commented Mar 23, 2017 edited

This is breaking unit tests for swift-llbuild, part of the Swift.org project:

$ umask 22
$ umask
0022
$ mkdir foo
$ ls -l
drwxrwxrwx 2 root root 0 Mar 23 16:47 foo

@harmishhk harmishhk added a commit to harmishhk/dotfiles that referenced this issue Mar 29, 2017

@harmishhk harmishhk set umask for WSL, Microsoft/BashOnWindows#352 7d7d84d

nesl247 commented Jun 7, 2017 edited

@jackchammons Why was this closed? Until the umask is working out of the box, this issue is still ongoing.

@sunilmut sunilmut reopened this Jun 12, 2017

@agross agross added a commit to agross/dotfiles that referenced this issue Jun 25, 2017

@agross agross Set umask for Bash on Windows, Microsoft/BashOnWindows#352 83b572f

@jameshclrk jameshclrk referenced this issue in zeit/hyper Jul 17, 2017

Open

Terminal colours not working correctly with bash on Windows #1706

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