Re: allow_domain_fd_use

[Daniel J Walsh]

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On 10/15/2013 03:48 AM, Tim.Einmahl(a)kba.de wrote:
>  Hi,
>  
>  I would like to know, how much risk is there setting allow_domain_fd_use to
>  1?
>  
>  I am not totally sure about the security impact. Would that allow a process
>  in one domain to read files and sockets that have been opened by a another
>  domain?
>  
>  
>  Usually, I disable it, but from time to time I get error messages like:
>  
>  - type=AVC msg=audit(1381801383.801:31585): avc:  denied  { use } for
>  pid=25761 comm="mail" path="/dev/null" dev=devtmpfs ino=3656
>  scontext=system_u:system_r:logrotate_mail_t:s0-s0:c0.c1023
>  tcontext=system_u:system_r:system_cronjob_t:s0-s0:c0.c1023 tclass=fd
>  
>  
>  type=AVC msg=audit(1381801383.801:31585): avc:  denied  { use } for
>  pid=25761 comm="mail" path="/dev/null" dev=devtmpfs ino=3656
>  scontext=system_u:system_r:logrotate_mail_t:s0-s0:c0.c1023
>  tcontext=system_u:system_r:system_cronjob_t:s0-s0:c0.c1023 tclass=fd
>  
>  
>  type=SYSCALL msg=audit(1381801383.801:31585): arch=x86_64 syscall=execve
>  success=yes exit=0 a0=229fcd0 a1=229fd50 a2=229df90 a3=7fffb994eef0 items=0
>  ppid=25741 pid=25761 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
>  fsgid=0 tty=(none) ses=1677 comm=mail exe=/bin/mailx
>  subj=system_u:system_r:logrotate_mail_t:s0-s0:c0.c1023 key=(null)
>  
>  
>  On a hypervisor, I have to allow it, otherwise I get millions of messages
>  like
>  
>  type=SYSCALL msg=audit(1381823069.947:3240474): arch=c000003e syscall=0
>  success=no exit=-13 a0=17 a1=7f9045c99ae4 a2=11000 a3=7fffa277af30 items=0
>  ppid=1 pid=9616 auid=4294967295 uid=107 gid=107 euid=107 suid=107 fsuid=107
>  egid=107 sgid=107 fsgid=107 tty=(none) ses=4294967295 comm="qemu-kvm"
>  exe=2F7573722F6C6962657865632F71656D752D6B766D202864656C6574656429
>  subj=system_u:system_r:svirt_t:s0:c559,c791 key=(null) type=AVC
>  msg=audit(1381823069.947:3240474): avc:  denied  { use } for  pid=9616
>  comm="qemu-kvm" path="/dev/net/tun" dev=devtmpfs ino=9274
>  scontext=system_u:system_r:svirt_t:s0:c559,c791
>  tcontext=system_u:system_r:virtd_t:s0-s0:c0.c1023 tclass=fd
>  
>  
>  Regards Tim
>  
>  -- selinux mailing list selinux(a)lists.fedoraproject.org 
>  https://admin.fedoraproject.org/mailman/listinfo/selinux
>  
>   
We usually have this on by default.  What OS/Policy version are you seeing
this with?

This basically means that one process can open a UID and pass it to another
process either through a fork/exec or my fd passing.


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