Re: getaddrinfo(3) chroot(2) with root

[Remco]

Denis Fondras wrote:

 Hello all,
 
 I am burning my last neurons with a behavior I can't explain. I wonder
 why getaddrinfo() fails when called after chroot() with root user.
 
 
 I have this piece of code :
 
...
 error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);
...

Apart from the other suggestions you got, I'm wandering why don't you try to 
get more information about the error using the gai_strerror(3) function ?
(like in the example of getaddrinfo(3))

Re: getaddrinfo(3) chroot(2) with root

[Otto Moerbeek]

On Wed, May 14, 2014 at 07:41:47PM +0200, Denis Fondras wrote:

  After chroot, /etc/resolv.conf is no longer available.
  
 
 Thank you very much Ted  Vadim.
 
  Other daemons like ntpd have a helper process that runs outside chroot
  and does all of the DNS resolution for them.
  
 
 Ok, I'll look on this side.
 
 Thank you,
 Denis

A quick way to solve this (but an administrative headache) is to
create etc/resolv.conf in your chroot.

-Otto

getaddrinfo(3) chroot(2) with root

[Denis Fondras]

Hello all,

I am burning my last neurons with a behavior I can't explain. I wonder
why getaddrinfo() fails when called after chroot() with root user.


I have this piece of code :

/*--- test.c ---*/
#include sys/types.h
#include stdio.h
#include sys/socket.h
#include netdb.h
#include pwd.h

int main(int argc, char *argv[])
{
struct addrinfo *ai_out;
struct passwd   *pw;
int error;

pw = getpwnam(_bgpd);

error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
if (error)
printf(getaddrinfo() failed\n);
else printf(getaddrinfo() succeed\n);

chroot(pw-pw_dir);
chdir(/);

error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
if (error)
printf(getaddrinfo() failed\n);
else printf(getaddrinfo() succeed\n);

return 0;
}
/*--- test.c ---*/

$ ./a.out
getaddrinfo() succeed
getaddrinfo() succeed

# ./a.out
getaddrinfo() succeed
getaddrinfo() succeed




Everything is good. Now if I compile :

/*--- test.c ---*/
#include sys/types.h
#include stdio.h
#include sys/socket.h
#include netdb.h
#include pwd.h

int main(int argc, char *argv[])
{
struct addrinfo *ai_out;
struct passwd   *pw;
int error;

pw = getpwnam(_bgpd);

error = 0
if (error)
printf(getaddrinfo() failed\n);
else printf(getaddrinfo() succeed\n);

chroot(pw-pw_dir);

error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
if (error)
printf(getaddrinfo() failed\n);
else printf(getaddrinfo() succeed\n);

return 0;
}
/*--- test.c ---*/

$ ./a.out
getaddrinfo() succeed
getaddrinfo() succeed

# ./a.out
getaddrinfo() succeed
getaddrinfo() failed



If this an expected behavior, what would be the preferred way to resolve
a name from a chrooted process ? I am extending OpenBGPd and I need to
resolve domain names and connect to a service (no BGP protocol). I am
currently using the session process to handle the connection part but
I am stuck on name resolution for now.

Thank you in advance,
Denis

Re: getaddrinfo(3) chroot(2) with root

[Peter J. Philipp]

On 05/14/14 18:57, Denis Fondras wrote:
 Hello all,
 
 I am burning my last neurons with a behavior I can't explain. I wonder
 why getaddrinfo() fails when called after chroot() with root user.
 
 
 I have this piece of code :
 
 /*--- test.c ---*/
 #include sys/types.h
 #include stdio.h
 #include sys/socket.h
 #include netdb.h
 #include pwd.h
 
 int main(int argc, char *argv[])
 {
 struct addrinfo *ai_out;
 struct passwd   *pw;
 int error;
 
 pw = getpwnam(_bgpd);
 
 error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);
 
 chroot(pw-pw_dir);
 chdir(/);
 
 error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);
 
 return 0;
 }
 /*--- test.c ---*/
 
 $ ./a.out
 getaddrinfo() succeed
 getaddrinfo() succeed
 
 # ./a.out
 getaddrinfo() succeed
 getaddrinfo() succeed
 
 
 
 
 Everything is good. Now if I compile :
 
 /*--- test.c ---*/
 #include sys/types.h
 #include stdio.h
 #include sys/socket.h
 #include netdb.h
 #include pwd.h
 
 int main(int argc, char *argv[])
 {
 struct addrinfo *ai_out;
 struct passwd   *pw;
 int error;
 
 pw = getpwnam(_bgpd);
 
 error = 0
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);
 
 chroot(pw-pw_dir);
 
 error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);
 
 return 0;
 }
 /*--- test.c ---*/
 
 $ ./a.out
 getaddrinfo() succeed
 getaddrinfo() succeed
 
 # ./a.out
 getaddrinfo() succeed
 getaddrinfo() failed
 
 
 
 If this an expected behavior, what would be the preferred way to resolve
 a name from a chrooted process ? I am extending OpenBGPd and I need to
 resolve domain names and connect to a service (no BGP protocol). I am
 currently using the session process to handle the connection part but
 I am stuck on name resolution for now.
 
 Thank you in advance,
 Denis
 

I wonder if you're using the wrong function.  There is gethostbyname for
forward lookups?

Regards,

-peter

Re: getaddrinfo(3) chroot(2) with root

[Ted Unangst]

On Wed, May 14, 2014 at 18:57, Denis Fondras wrote:
 Hello all,
 
 I am burning my last neurons with a behavior I can't explain. I wonder
 why getaddrinfo() fails when called after chroot() with root user.

After chroot, /etc/resolv.conf is no longer available.

 If this an expected behavior, what would be the preferred way to resolve
 a name from a chrooted process ? I am extending OpenBGPd and I need to
 resolve domain names and connect to a service (no BGP protocol). I am
 currently using the session process to handle the connection part but
 I am stuck on name resolution for now.

Other daemons like ntpd have a helper process that runs outside chroot
and does all of the DNS resolution for them.

Re: getaddrinfo(3) chroot(2) with root

[Denis Fondras]

Le 14/05/2014 19:14, Peter J. Philipp a écrit :
 
 I wonder if you're using the wrong function.  There is gethostbyname for
 forward lookups?
 

I read it was deprecated.

Denis

Re: getaddrinfo(3) chroot(2) with root

[Vadim Zhukov]

2014-05-14 20:57 GMT+04:00 Denis Fondras open...@ledeuns.net:
 Hello all,

 I am burning my last neurons with a behavior I can't explain. I wonder
 why getaddrinfo() fails when called after chroot() with root user.


 I have this piece of code :

 /*--- test.c ---*/
 #include sys/types.h
 #include stdio.h
 #include sys/socket.h
 #include netdb.h
 #include pwd.h

 int main(int argc, char *argv[])
 {
 struct addrinfo *ai_out;
 struct passwd   *pw;
 int error;

 pw = getpwnam(_bgpd);

 error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);

 chroot(pw-pw_dir);
 chdir(/);

 error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);

 return 0;
 }
 /*--- test.c ---*/

 $ ./a.out
 getaddrinfo() succeed
 getaddrinfo() succeed

 # ./a.out
 getaddrinfo() succeed
 getaddrinfo() succeed




 Everything is good. Now if I compile :

 /*--- test.c ---*/
 #include sys/types.h
 #include stdio.h
 #include sys/socket.h
 #include netdb.h
 #include pwd.h

 int main(int argc, char *argv[])
 {
 struct addrinfo *ai_out;
 struct passwd   *pw;
 int error;

 pw = getpwnam(_bgpd);

 error = 0
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);

 chroot(pw-pw_dir);

 error = getaddrinfo(rpki.liopen.eu, NULL, NULL, ai_out);
 if (error)
 printf(getaddrinfo() failed\n);
 else printf(getaddrinfo() succeed\n);

 return 0;
 }
 /*--- test.c ---*/

 $ ./a.out
 getaddrinfo() succeed
 getaddrinfo() succeed

 # ./a.out
 getaddrinfo() succeed
 getaddrinfo() failed



 If this an expected behavior, what would be the preferred way to resolve
 a name from a chrooted process ? I am extending OpenBGPd and I need to
 resolve domain names and connect to a service (no BGP protocol). I am
 currently using the session process to handle the connection part but
 I am stuck on name resolution for now.

/etc/resolv.conf is read on the first attempt to resolve something,
no? And, of course, you have no /your/chroot/path/etc/resolv.conf.

--
  WBR,
  Vadim Zhukov

Re: getaddrinfo(3) chroot(2) with root

[Denis Fondras]

 After chroot, /etc/resolv.conf is no longer available.
 

Thank you very much Ted  Vadim.

 Other daemons like ntpd have a helper process that runs outside chroot
 and does all of the DNS resolution for them.
 

Ok, I'll look on this side.

Thank you,
Denis