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Re: bug in [ -f file ] test


From: Reuti
Subject: Re: bug in [ -f file ] test
Date: Wed, 27 Jul 2016 17:55:53 +0200

> Am 27.07.2016 um 17:36 schrieb László Házy <address@hidden>:
> 
> Yes, user2 has rx access to /home/user1. This is done by the first command in 
> the list of commands, namely: "[user1]$ chmod g+rx /home/user1". The two 
> users are part of the same group.
> 
> An even more troublesome variation, involving root, is the following:
> 
> [user1]$ touch file; ls -l file
> -rw-r--r--. 1 user1 users    0 Jul 26 15:24 file

The dot at the end means SELinux ACL IIRC - are you running SELinux?

-- Reuti


> [user1]$ ln -s /home/user1/file /var/tmp/link
> [user1]$ ls -l /var/tmp/link
> lrwxrwxrwx. 1 user1 users 17 Jul 26 15:26 /var/tmp/link -> /home/user1/file
> 
> [user1]$ [[ -f /var/tmp/link ]]; echo $?
> 0
> 
> [user1]$ su 
> [root]$ [[ -f /var/tmp/link ]]; echo $?
> 1
> 
> 
> On Tue, 2016-07-26 at 23:26 +0200, Reuti wrote:
>> Am 26.07.2016 um 23:07 schrieb László Házy:
>> 
>> 
>>> 
>>> Hmm, interesting. I can reproduce your results. Thanks.
>>> However, note the following:
>>> 
>>> [user1]$ chmod g+rx /home/user1
>>> [user1]$ touch file; ls -l file
>>> -rw-r--r--. 1 user1 users    0 Jul 26 15:24 file
>>> 
>>> [user1]$ su user2 -c "ln -s /home/user1/file /var/tmp/link"
>>> [user1]$ ls -l /var/tmp/link
>>> lrwxrwxrwx. 1 user2 users 17 Jul 26 15:26 /var/tmp/link -> /home/user1/file
>>> 
>>> [user1]$ [[ -f /var/tmp/link ]]; echo $?
>>> 1
>>> 
>>> [user1]$ su user2
>>> [user2]$ [[ -f /var/tmp/link ]]; echo $?
>>> 0
>>> 
>>> Something does not add up.
>>> 
>> 
>> 
>> Does user2 have rx access to /home/user1?
>> 
>> -- Reuti
>> 
>> 
>> 
>>> 
>>> From experimenting, it appears that only the user who created the symlink 
>>> will get true for the file test.
>>> 
>>> Thank you.
>>> 
>>> 
>>> 
>>> 
>>> On Tue, 2016-07-26 at 15:06 -0400, Grisha Levit wrote:
>>> 
>>>> 
>>>> Are you sure "file" is a link to an actual file, not, say, a directory?
>>>> 
>>>> $ rpm -q bash; echo $BASH_VERSION; cat /etc/redhat-release
>>>> bash-4.3.42-3.fc23.x86_64
>>>> 4.3.42(1)-release
>>>> Fedora release 23 (Twenty Three)
>>>> 
>>>> $ touch file; ln -s file link; [[ -f link ]]; echo $?
>>>> 0
>>>> 
>>>> On Tue, Jul 26, 2016 at 12:58 PM, László Házy <
>>>> address@hidden
>>>> > wrote:
>>>> 
>>>>> 
>>>>> I am running bash 4.3.42-3 on Fedore Core 23.
>>>>> 
>>>>> I noticed that the [ -f file ] test returns false if "file" is a symlink. 
>>>>> Given the intended behavior (from a long time ago), this is wrong as the 
>>>>> symlinks are supposed to be followed. It certainly brakes functionality 
>>>>> in certain existing software.
>>>>> 
>>>>> Has the default behavior been changed somewhere along the time line and I 
>>>>> am not aware of it?
>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> 
>>>> 
>>> 
>> 
>> 
>> 




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