NSS: Fix use after free

It can happed if there are two domains and user is not found
in the first one.

==29279== Invalid read of size 1
==29279==    at 0x4C2CBA2: strlen (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==29279==    by 0x89A7AC4: talloc_strdup (in /usr/lib64/libtalloc.so.2.1.2)
==29279==    by 0x11668A: nss_cmd_initgroups_search (nsssrv_cmd.c:4191)
==29279==    by 0x118B27: nss_cmd_getby_dp_callback (nsssrv_cmd.c:1208)
==29279==    by 0x10F2B4: nsssrv_dp_send_acct_req_done (nsssrv_cmd.c:759)
==29279==    by 0x126AFB: sss_dp_internal_get_done (responder_dp.c:802)
==29279==    by 0x56EA861: ??? (in /usr/lib64/libdbus-1.so.3.7.4)
==29279==    by 0x56EDB50: dbus_connection_dispatch (in /usr/lib64/libdbus-1.so.3.7.4)
==29279==    by 0x50721E1: sbus_dispatch (sssd_dbus_connection.c:96)
==29279==    by 0x879B22E: tevent_common_loop_timer_delay (tevent_timed.c:341)
==29279==    by 0x879C239: epoll_event_loop_once (tevent_epoll.c:911)
==29279==    by 0x879A936: std_event_loop_once (tevent_standard.c:114)
==29279==  Address 0xbbad240 is 96 bytes inside a block of size 106 free'd
==29279==    at 0x4C2AD17: free (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==29279==    by 0x89A46E3: _talloc_free (in /usr/lib64/libtalloc.so.2.1.2)
==29279==    by 0x116679: nss_cmd_initgroups_search (nsssrv_cmd.c:4190)
==29279==    by 0x118B27: nss_cmd_getby_dp_callback (nsssrv_cmd.c:1208)
==29279==    by 0x10F2B4: nsssrv_dp_send_acct_req_done (nsssrv_cmd.c:759)
==29279==    by 0x126AFB: sss_dp_internal_get_done (responder_dp.c:802)
==29279==    by 0x56EA861: ??? (in /usr/lib64/libdbus-1.so.3.7.4)
==29279==    by 0x56EDB50: dbus_connection_dispatch (in /usr/lib64/libdbus-1.so.3.7.4)
==29279==    by 0x50721E1: sbus_dispatch (sssd_dbus_connection.c:96)
==29279==    by 0x879B22E: tevent_common_loop_timer_delay (tevent_timed.c:341)
==29279==    by 0x879C239: epoll_event_loop_once (tevent_epoll.c:911)
==29279==    by 0x879A936: std_event_loop_once (tevent_standard.c:114)

Resolves:
https://fedorahosted.org/sssd/ticket/2749

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

2 files changed, 4 insertions, 3 deletions

diff --git a/src/responder/nss/nsssrv_cmd.c b/src/responder/nss/nsssrv_cmd.c
index aa64432d5..459634b8d 100644
--- a/src/responder/nss/nsssrv_cmd.c
+++ b/src/responder/nss/nsssrv_cmd.c
@@ -4107,7 +4107,7 @@ static int nss_cmd_initgr_send_reply(struct nss_dom_ctx *dctx)
     }
 
     ret = fill_initgr(cctx->creq->out, dctx->domain, dctx->res, nctx,
-                      dctx->mc_name, cmdctx->name);
+                      dctx->mc_name, cmdctx->normalized_name);
     if (ret) {
         return ret;
     }
@@ -4151,14 +4151,14 @@ static int nss_cmd_initgroups_search(struct nss_dom_ctx *dctx)
         /* make sure to update the dctx if we changed domain */
         dctx->domain = dom;
 
-        talloc_free(name);
+        talloc_zfree(cmdctx->normalized_name);
         name = sss_get_cased_name(dctx, cmdctx->name, dom->case_sensitive);
         if (!name) return ENOMEM;
 
         name = sss_reverse_replace_space(cmdctx, name,
                                          nctx->rctx->override_space);
         /* save name so it can be used in initgr reply */
-        cmdctx->name = name;
+        cmdctx->normalized_name = name;
         if (name == NULL) {
             DEBUG(SSSDBG_CRIT_FAILURE,
                   "sss_reverse_replace_space failed\n");
diff --git a/src/responder/nss/nsssrv_private.h b/src/responder/nss/nsssrv_private.h
index e5a2486f1..72f7b7560 100644
--- a/src/responder/nss/nsssrv_private.h
+++ b/src/responder/nss/nsssrv_private.h
@@ -31,6 +31,7 @@ struct nss_cmd_ctx {
     struct cli_ctx *cctx;
     enum sss_cli_command cmd;
     char *name;
+    const char *normalized_name;
     bool name_is_upn;
     uint32_t id;
     char *secid;