Fix for bug #5551, smbd recursing back into winbindd from a winbindd call.

Jeremy.
(cherry picked from commit 132a5f4a5740f8a4e3bd634af654c9761c11aa1a)

1 files changed, 66 insertions, 13 deletions

diff --git a/source/auth/auth_util.c b/source/auth/auth_util.c
index 7013285809c..115a6e9ad20 100644
--- a/source/auth/auth_util.c
+++ b/source/auth/auth_util.c
@@ -486,26 +486,50 @@ static auth_serversupplied_info *make_server_info(TALLOC_CTX *mem_ctx)
 }
 
 /***************************************************************************
+ Is the incoming username our own machine account ?
+ If so, the connection is almost certainly from winbindd.
+***************************************************************************/
+
+static bool is_our_machine_account(const char *username)
+{
+	bool ret;
+	char *truncname = NULL;
+	size_t ulen = strlen(username);
+
+	if (ulen == 0 || username[ulen-1] != '$') {
+		return false;
+	}
+	truncname = SMB_STRDUP(username);
+	if (!truncname) {
+		return false;
+	}
+	truncname[ulen-1] = '\0';
+	ret = strequal(truncname, global_myname());
+	SAFE_FREE(truncname);
+	return ret;
+}
+
+/***************************************************************************
  Make (and fill) a user_info struct from a struct samu
 ***************************************************************************/
 
-NTSTATUS make_server_info_sam(auth_serversupplied_info **server_info, 
+NTSTATUS make_server_info_sam(auth_serversupplied_info **server_info,
 			      struct samu *sampass)
 {
-	NTSTATUS status;
 	struct passwd *pwd;
 	gid_t *gids;
 	auth_serversupplied_info *result;
 	int i;
 	size_t num_gids;
 	DOM_SID unix_group_sid;
-	
+	const char *username = pdb_get_username(sampass);
+	NTSTATUS status;
 
 	if ( !(result = make_server_info(NULL)) ) {
 		return NT_STATUS_NO_MEMORY;
 	}
 
-	if ( !(pwd = getpwnam_alloc(result, pdb_get_username(sampass))) ) {
+	if ( !(pwd = getpwnam_alloc(result, username)) ) {
 		DEBUG(1, ("User %s in passdb, but getpwnam() fails!\n",
 			  pdb_get_username(sampass)));
 		TALLOC_FREE(result);
@@ -520,21 +544,50 @@ NTSTATUS make_server_info_sam(auth_serversupplied_info **server_info,
 	talloc_steal(result, pwd->pw_name);
 	result->gid = pwd->pw_gid;
 	result->uid = pwd->pw_uid;
-	
+
 	TALLOC_FREE(pwd);
 
-	status = pdb_enum_group_memberships(result, sampass,
+	if (IS_DC && is_our_machine_account(username)) {
+		/*
+		 * Ensure for a connection from our own
+		 * machine account (from winbindd on a DC)
+		 * there are no supplementary groups.
+		 * Prevents loops in calling gid_to_sid().
+		 */
+		result->sids = NULL;
+		gids = NULL;
+		result->num_sids = 0;
+
+		/*
+		 * This is a hack of monstrous proportions.
+		 * If we know it's winbindd talking to us,
+		 * we know we must never recurse into it,
+		 * so turn off contacting winbindd for this
+		 * entire process. This will get fixed when
+		 * winbindd doesn't need to talk to smbd on
+		 * a PDC. JRA.
+		 */
+
+		winbind_off();
+
+		DEBUG(10, ("make_server_info_sam: our machine account %s "
+			"setting supplementary group list empty and "
+			"turning off winbindd requests.\n",
+			username));
+	} else {
+		status = pdb_enum_group_memberships(result, sampass,
 					    &result->sids, &gids,
 					    &result->num_sids);
 
-	if (!NT_STATUS_IS_OK(status)) {
-		DEBUG(10, ("pdb_enum_group_memberships failed: %s\n",
-			   nt_errstr(status)));
-		result->sam_account = NULL; /* Don't free on error exit. */
-		TALLOC_FREE(result);
-		return status;
+		if (!NT_STATUS_IS_OK(status)) {
+			DEBUG(10, ("pdb_enum_group_memberships failed: %s\n",
+				   nt_errstr(status)));
+			result->sam_account = NULL; /* Don't free on error exit. */
+			TALLOC_FREE(result);
+			return status;
+		}
 	}
-	
+
 	/* Add the "Unix Group" SID for each gid to catch mapped groups
 	   and their Unix equivalent.  This is to solve the backwards 
 	   compatibility problem of 'valid users = +ntadmin' where