[PATCH] IPA: Use function sysdb_attrs_get_el in safe way

[Lukas Slebodnik]

ehlo,

Intention of ticket @2284 was to refactor function sysdb_attrs_get_el
This would be a big change and it would not ne easy to backport patch
to the branch sssd-1-11. The attached patch fixes prolem in simple way
and patch can be easily applied on top of branch sssd-1-11

Function sysdb_attrs_get_el can enlarge array of ldb_message_element in "struct
sysdb_attrs" if attribute is not among available attributes. Array will be
enlarged with function talloc_realloc but realloc can move array to another
place in memory therefore ldb_message_element should not be used after next
call of function sysdb_attrs_get_el

    sysdb_attrs_get_el(netgroup, SYSDB_ORIG_MEMBER_USER, &user_found);
    sysdb_attrs_get_el(netgroup, SYSDB_ORIG_MEMBER_HOST, &host_found);
With netgroups, it is common to omit user or host from netgroup triple.
There is very high probability that realloc will be called. it is possible
pointer user_found can refer to the old area after the second call of function
sysdb_attrs_get_el.

Resolves:
https://fedorahosted.org/sssd/ticket/2284

How to test?
sh-4.2$ getent netgroup netgroup_user1
netgroup_user2        (-,usersssd01,example.com)

and run backend with valgrind

Result:
    --without patch: there are errors like in description of ticket
                        https://fedorahosted.org/sssd/ticket/2284
    --with patch: errors are gone

LS

[Sumit Bose]

On Wed, Mar 26, 2014 at 12:37:01PM +0100, Lukas Slebodnik wrote:
>  ehlo,
>  
>  Intention of ticket @2284 was to refactor function sysdb_attrs_get_el
>  This would be a big change and it would not ne easy to backport patch
>  to the branch sssd-1-11. The attached patch fixes prolem in simple way
>  and patch can be easily applied on top of branch sssd-1-11
>  
>  Function sysdb_attrs_get_el can enlarge array of ldb_message_element in "struct
>  sysdb_attrs" if attribute is not among available attributes. Array will be
>  enlarged with function talloc_realloc but realloc can move array to another
>  place in memory therefore ldb_message_element should not be used after next
>  call of function sysdb_attrs_get_el
>  
>      sysdb_attrs_get_el(netgroup, SYSDB_ORIG_MEMBER_USER, &user_found);
>      sysdb_attrs_get_el(netgroup, SYSDB_ORIG_MEMBER_HOST, &host_found);
>  With netgroups, it is common to omit user or host from netgroup triple.
>  There is very high probability that realloc will be called. it is possible
>  pointer user_found can refer to the old area after the second call of function
>  sysdb_attrs_get_el.
>  
>  Resolves:
>  https://fedorahosted.org/sssd/ticket/2284
>  
>  How to test?
>  sh-4.2$ getent netgroup netgroup_user1
>  netgroup_user2        (-,usersssd01,example.com)
>  
>  and run backend with valgrind
>  
>  Result:
>      --without patch: there are errors like in description of ticket
>                          https://fedorahosted.org/sssd/ticket/2284
>      --with patch: errors are gone
>  
>  LS 
Patch looks good and passes my tests, ACK. Pavel gave his ACK on irc as
well.

bye,
Sumit

[Jakub Hrozek]

On Wed, Mar 26, 2014 at 02:43:14PM +0100, Sumit Bose wrote:
>  On Wed, Mar 26, 2014 at 12:37:01PM +0100, Lukas Slebodnik wrote:
>  > ehlo,
>  > 
>  > Intention of ticket @2284 was to refactor function sysdb_attrs_get_el
>  > This would be a big change and it would not ne easy to backport patch
>  > to the branch sssd-1-11. The attached patch fixes prolem in simple way
>  > and patch can be easily applied on top of branch sssd-1-11
>  > 
>  > Function sysdb_attrs_get_el can enlarge array of ldb_message_element in
> "struct
>  > sysdb_attrs" if attribute is not among available attributes. Array will be
>  > enlarged with function talloc_realloc but realloc can move array to another
>  > place in memory therefore ldb_message_element should not be used after next
>  > call of function sysdb_attrs_get_el
>  > 
>  >     sysdb_attrs_get_el(netgroup, SYSDB_ORIG_MEMBER_USER, &user_found);
>  >     sysdb_attrs_get_el(netgroup, SYSDB_ORIG_MEMBER_HOST, &host_found);
>  > With netgroups, it is common to omit user or host from netgroup triple.
>  > There is very high probability that realloc will be called. it is possible
>  > pointer user_found can refer to the old area after the second call of function
>  > sysdb_attrs_get_el.
>  > 
>  > Resolves:
>  > https://fedorahosted.org/sssd/ticket/2284
>  > 
>  > How to test?
>  > sh-4.2$ getent netgroup netgroup_user1
>  > netgroup_user2        (-,usersssd01,example.com)
>  > 
>  > and run backend with valgrind
>  > 
>  > Result:
>  >     --without patch: there are errors like in description of ticket
>  >                         https://fedorahosted.org/sssd/ticket/2284
>  >     --with patch: errors are gone
>  > 
>  > LS
>  
>  Patch looks good and passes my tests, ACK. Pavel gave his ACK on irc as
>  well.
>  
>  bye,
>  Sumit 
Pushed to master and sssd-1-11