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File /etc/shadow belongs to root, and access permission is set to 400 or "-r--------" (unless chmod).
So it can't be modified by even root.
But when I login as a normal user (UID 500 up) and I change password with the command /usr/bin/passwd, file /etc/shadow is consequently changed.
I think such binary can gain privilege over even root.
I question how to make such bin with gcc/g++?
Waaaaaaaait a second... there is no restriction to what root can do!
I just tried chmod'ing a file to 400... root could still edit it fine.
Sounds like there's another issue with your system, but I'm far from a linux expert.
/etc/shadow is supposed to be accessed by privilaged users only. You should grant access to it lightly.
>>I don't know why that file is only readable by root
Because it is supposed to hold the users passwords (encrypted), its "safer" than storing them in /etc/passwd which must be globally accessable. shadow
>>Yeah, I know what Shadow passwords are,
I thought you would ;) I was just picking up on:
>I don't know why that file is only readable by root
and
>Debian machine and it's rw root, r other
>>but why should the file not be writeable by root
Don't know, that's a strange one. Maybe it's one extra level of "security" to frighten a newbie haxor... yes it's lame (and pointless), but it's all I can think of!
Makes sense now :)
Quote:
http://www.debian.org/doc/manuals/se...to/ch3.en.html
/etc/shadow
Only the root user and the group shadow have read access to this file,
I did not change access permission, -r-------- is default one.
Anyway thank for all hints.
But I still w:onder when I login as a normal user, I can use /usr/bin/passwd to change /etc/shadow, which is not writeable for normal users.
Look at the permissions on /usr/bin/passwd. What are they set to?Quote:
Originally posted by Jaguar
But I still w:onder when I login as a normal user, I can use /usr/bin/passwd to change /etc/shadow, which is not writeable for normal users.
I could be wrong, but I do not belive suid allows a program to 'set' it's UID to 0, it's rather given the UID of 0. A program does not have to be aware if it is suid or not, you can suid any program and it will be given super users priveleges.
On a side note, besides the given suid apps (passwd being one of them), sudo is a great tool to give specific users the ability to run suid apps.
(Just thought I'd add my 2 cents)
I run a few linux boxes some redhat etc. And all of them
have
-r-------- root root ***** /etc/shadow
note: no matter what, root can change anything ANYTHING. Like it was the kernel or in control of the kernel. If it can't change something then it's not Unix.
Do you really think they're still looking nearly 3 months later...?