more libcap2

Robert Connolly robert at linuxfromscratch.org
Thu Oct 2 21:39:01 PDT 2008


On Friday October 3 2008 12:12:15 am Robert Connolly wrote:
> Another suid-root dropped:
>
> chmod -s /bin/su
> setcap CAP_DAC_READ_SEARCH,CAP_SETUID,CAP_SETGID=ep /bin/su
>
> robert

/bin/su seems to want to reset the gid, and probably the uid, of /etc/shadow, 
according to Strace.

Regardless of the comments in /usr/include/linux/capability.h, it looks like 
CAP_DAC_READ_SEARCH allows writting to /etc/shadow.

If I remove CAP_DAC_READ_SEARCH, and make /etc/shadow group 
read/writable, /bin/su works. Each has pros and cons, and I don't know which 
is better.

This might be a bug in CAP_DAC_READ_SEARCH... somehow FOWNER was mixed in.

Opinions, debug help?

robert
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