s3: smbd: Ensure we always go via getgroups_unix_user() when creating an NT token.

This has to be done in every code path that creates
an NT token, as remote users may have been added to
the local /etc/group database. Tokens created merely
from the info3 structs (via the DC or via the krb5 PAC)
won't have these local groups.

This code needs to special-case the guest user, as
this token can have the token_sid[0] set to the Guest
SID, not the mapping of UNIX uid -> SID.

Other users that may have a well-known SID
set in token_sid[0] (like SYSTEM) are usually
not mappable to UNIX users and can be ignored
when adding local groups from /etc/group.

Combined back-port of fixes
6034ab521c47fc5f4732398652c9c6847ff92035 and
a9fa09723bee3588db2168ac13f7ad0334452c11 from
master.

https://bugzilla.samba.org/show_bug.cgi?id=10508

Signed-off-by: Jeremy Allison <jra@samba.org>

diff --git a/source3/auth/token_util.c b/source3/auth/token_util.c
index d86d589cc3d6ff14d6c6491fb33d79fa63bca84c..be44ce949d9f6f4c6dd116795d1bcc768cf00db6 100644 (file)
--- a/source3/auth/token_util.c
+++ b/source3/auth/token_util.c
@@ -389,6 +389,100 @@ struct security_token *create_local_nt_token(TALLOC_CTX *mem_ctx,
        return result;
 }
 
+/***************************************************
+ Merge in any groups from /etc/group.
+***************************************************/
+
+static NTSTATUS add_local_groups(struct security_token *result,
+                                bool is_guest)
+{
+       gid_t *gids = NULL;
+       uint32_t getgroups_num_group_sids = 0;
+       struct passwd *pass = NULL;
+       TALLOC_CTX *tmp_ctx = talloc_stackframe();
+       int i;
+
+       if (is_guest) {
+               /*
+                * Guest is a special case. It's always
+                * a user that can be looked up, but
+                * result->sids[0] is set to DOMAIN\Guest.
+                * Lookup by account name instead.
+                */
+               pass = Get_Pwnam_alloc(tmp_ctx, lp_guestaccount());
+       } else {
+               uid_t uid;
+
+               /* For non-guest result->sids[0] is always the user sid. */
+               if (!sid_to_uid(&result->sids[0], &uid)) {
+                       /*
+                        * Non-mappable SID like SYSTEM.
+                        * Can't be in any /etc/group groups.
+                        */
+                       TALLOC_FREE(tmp_ctx);
+                       return NT_STATUS_OK;
+               }
+
+               pass = getpwuid_alloc(tmp_ctx, uid);
+               if (pass == NULL) {
+                       DEBUG(1, ("SID %s -> getpwuid(%u) failed\n",
+                               sid_string_dbg(&result->sids[0]),
+                               (unsigned int)uid));
+               }
+       }
+
+       if (!pass) {
+               TALLOC_FREE(tmp_ctx);
+               return NT_STATUS_UNSUCCESSFUL;
+       }
+
+       /*
+        * Now we must get any groups this user has been
+        * added to in /etc/group and merge them in.
+        * This has to be done in every code path
+        * that creates an NT token, as remote users
+        * may have been added to the local /etc/group
+        * database. Tokens created merely from the
+        * info3 structs (via the DC or via the krb5 PAC)
+        * won't have these local groups. Note the
+        * groups added here will only be UNIX groups
+        * (S-1-22-2-XXXX groups) as getgroups_unix_user()
+        * turns off winbindd before calling getgroups().
+        *
+        * NB. This is duplicating work already
+        * done in the 'unix_user:' case of
+        * create_token_from_sid() but won't
+        * do anything other than be inefficient
+        * in that case.
+        */
+
+       if (!getgroups_unix_user(tmp_ctx, pass->pw_name, pass->pw_gid,
+                       &gids, &getgroups_num_group_sids)) {
+               DEBUG(1, ("getgroups_unix_user for user %s failed\n",
+                       pass->pw_name));
+               TALLOC_FREE(tmp_ctx);
+               return NT_STATUS_UNSUCCESSFUL;
+       }
+
+       for (i=0; i<getgroups_num_group_sids; i++) {
+               NTSTATUS status;
+               struct dom_sid grp_sid;
+               gid_to_sid(&grp_sid, gids[i]);
+
+               status = add_sid_to_array_unique(result,
+                                        &grp_sid,
+                                        &result->sids,
+                                        &result->num_sids);
+               if (!NT_STATUS_IS_OK(status)) {
+                       DEBUG(3, ("Failed to add UNIX SID to nt token\n"));
+                       TALLOC_FREE(tmp_ctx);
+                       return status;
+               }
+       }
+       TALLOC_FREE(tmp_ctx);
+       return NT_STATUS_OK;
+}
+
 static NTSTATUS finalize_local_nt_token(struct security_token *result,
                                        bool is_guest)
 {
@@ -396,6 +490,13 @@ static NTSTATUS finalize_local_nt_token(struct security_token *result,
        gid_t gid;
        NTSTATUS status;
 
+       /* Add any local groups. */
+
+       status = add_local_groups(result, is_guest);
+       if (!NT_STATUS_IS_OK(status)) {
+               return status;
+       }
+
        /* Add in BUILTIN sids */
 
        status = add_sid_to_array(result, &global_sid_World,