[Rcpp-devel] How to elevate privilege from within Rcpp?

| I need to call a 3rd party library function with root privileges.
| I'm not sure how to accomplish this from within Rcpp.

I dont think you can ...
 
| If I was writing an executable, I could call seteuid to elevate privileges
| before calling the external function, and set the suid bit on the executable.
| But given that this needs to be done from within a Rcpp Library, I'm not sure
| how to do this. The last thing I want to do is run R as root or set suid on the
| R binary.

... unless you run R with suid bits, which you shouldn't as you rightly point out.

Rcpp is standard C/C++ code. So the wisdom of 'man seteuid' still applies:

   seteuid() sets the effective user ID of the calling process.  Unprivileged
   user processes may only set the effective user ID to the real user ID, the
   effective user ID or the saved set-user-ID.
 
| Any help / pointers would be greatly appreciated.

You may have to call a small self-contained executable which may then have a
suid bit set.

Dirk

http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

Thanks Dirk,
I was afraid of that, but glad that you confirmed it. In the mean time I've
figured out a way that may not require root :)

thanks again
Bhaskar

On 15 March 2015 at 15:48, Bhaskar V. Karambelkar wrote:
| I need to call a 3rd party library function with root privileges.
| I'm not sure how to accomplish this from within Rcpp.

I dont think you can ...

| If I was writing an executable, I could call seteuid to elevate
privileges
| before calling the external function, and set the suid bit on the
executable.
| But given that this needs to be done from within a Rcpp Library, I'm not
sure
| how to do this. The last thing I want to do is run R as root or set suid
on the
| R binary.

... unless you run R with suid bits, which you shouldn't as you rightly
point out.

Rcpp is standard C/C++ code. So the wisdom of 'man seteuid' still applies:

   seteuid() sets the effective user ID of the calling process.
Unprivileged
   user processes may only set the effective user ID to the real user ID,
the
   effective user ID or the saved set-user-ID.

| Any help / pointers would be greatly appreciated.

You may have to call a small self-contained executable which may then have
a
suid bit set.

Dirk

--
http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

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| I was afraid of that, but glad that you confirmed it. In the mean time I've
| figured out a way that may not require root :)

Hah!  If there is a generalizable trick worth sharing then please don't hold
back and tell us.

Dirk

http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

Nope I'm afraid no generalization trick. Basically I needed to open a RAW
socket which requires root access, but reading up on socket man page, I see
that now I can open a ICMP socket which is a new addition, and doesn't
require root and yet do what I want to do.

So just something that works for my particular case.

thanks
Bhaskar

On 15 March 2015 at 16:26, Bhaskar V. Karambelkar wrote:
| I was afraid of that, but glad that you confirmed it. In the mean time
I've
| figured out a way that may not require root :)

Hah!  If there is a generalizable trick worth sharing then please don't
hold
back and tell us.

Dirk

--
http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org

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