Adding upstream version 2.4.57+dfsg.upstream/2.4.57+dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 810 insertions, 0 deletions

diff --git a/servers/slapd/back-relay/Makefile.in b/servers/slapd/back-relay/Makefile.in
new file mode 100644
index 0000000..15100af
--- /dev/null
+++ b/servers/slapd/back-relay/Makefile.in
@@ -0,0 +1,41 @@
+# Makefile.in for back-relay
+# $OpenLDAP$
+## This work is part of OpenLDAP Software <http://www.openldap.org/>.
+##
+## Copyright 1998-2021 The OpenLDAP Foundation.
+## All rights reserved.
+##
+## Redistribution and use in source and binary forms, with or without
+## modification, are permitted only as authorized by the OpenLDAP
+## Public License.
+##
+## A copy of this license is available in the file LICENSE in the
+## top-level directory of the distribution or, alternatively, at
+## <http://www.OpenLDAP.org/license.html>.
+
+SRCS	= init.c op.c
+OBJS	= init.lo op.lo
+
+LDAP_INCDIR= ../../../include       
+LDAP_LIBDIR= ../../../libraries
+
+BUILD_OPT = "--enable-relay"
+BUILD_MOD = @BUILD_RELAY@
+
+mod_DEFS = -DSLAPD_IMPORT
+MOD_DEFS = $(@BUILD_RELAY@_DEFS)
+
+shared_LDAP_LIBS = $(LDAP_LIBLDAP_R_LA) $(LDAP_LIBLBER_LA)
+NT_LINK_LIBS = -L.. -lslapd $(@BUILD_LIBS_DYNAMIC@_LDAP_LIBS) $(REWRITE)
+UNIX_LINK_LIBS = $(@BUILD_LIBS_DYNAMIC@_LDAP_LIBS) $(REWRITE)
+
+LIBBASE = back_relay
+
+XINCPATH = -I.. -I$(srcdir)/..
+XDEFS = $(MODULES_CPPFLAGS)
+
+all-local-lib:	../.backend
+
+../.backend: lib$(LIBBASE).a
+	@touch $@
+
diff --git a/servers/slapd/back-relay/README b/servers/slapd/back-relay/README
new file mode 100644
index 0000000..81f152c
--- /dev/null
+++ b/servers/slapd/back-relay/README
@@ -0,0 +1,83 @@
+Relay backend sets up a relay virtual database that allows
+to access other databases in the same instance of slapd
+through different naming contexts and remapping attribute 
+values.
+
+The DN rewrite, filter rewrite and attributeType/objectClass
+mapping is done by means of the rewrite-remap overlay.
+
+The database containing the real naming context can be
+explicitly selected by means of the "relay" directive,
+which must contain the naming context of the target 
+database.  This also causes the rewrite-remap overlay 
+to be automatically instantiated.  If the optional keyword 
+"massage" is present, the rewrite-remap overlay is 
+automatically configured to map the virtual to the real 
+naming context and vice-versa.
+
+Otherwise, the rewrite-remap overlay must be explicitly
+instantiated, by using the "overlay" directive, as 
+illustrated below.  This allows much more freedom in target 
+database selection and DN rewriting.
+
+If the "relay" directive is not present, the backend is
+not bound to a single target database; on the contrary,
+the target database is selected on a per-operation basis.
+
+This allows, for instance, to relay one database for 
+authentication and anotheir for search/modify, or allows
+to use one target for persons and another for groups
+and so on.
+
+To summarize: the "relay" directive:
+- explicitly bounds the database to a single database 
+  holding the real naming context;
+- automatically instantiates the rewrite-remap overlay;
+- automatically configures the naming context massaging
+  if the optional "massage" keyword is added
+
+If the "relay" directive is not used, the rewrite-remap
+overlay must be explicitly instantiated and the massaging
+must be configured, either by using the "suffixmassage"
+directive, or by issuing more sophisticate rewrite 
+instructions.
+
+AttributeType/objectClass mapping must be explicitly
+required.
+
+Note that the rewrite-remap overlay is not complete nor 
+production- ready yet.
+Examples are given of all the suggested usages. 
+
+# automatically massage from virtual to real naming context
+database	relay
+suffix		"dc=virtual,dc=naming,dc=context"
+relay		"dc=real,dc=naming,dc=context" massage
+
+# explicitly massage (same as above)
+database	relay
+suffix		"dc=virtual,dc=naming,dc=context"
+relay		"dc=real,dc=naming,dc=context"
+suffixmassage	"dc=virtual,dc=naming,dc=context" \
+			"dc=real,dc=naming,dc=context"
+
+# explicitly massage (same as above, but dynamic backend resolution)
+database	relay
+suffix		"dc=virtual,dc=naming,dc=context"
+overlay		rewrite-remap
+suffixmassage	"dc=virtual,dc=naming,dc=context" \
+			"dc=real,dc=naming,dc=context"
+
+# old fashioned suffixalias, applied also to DN-valued attributes
+# from virtual to real naming context, but not the reverse...
+database	relay
+suffix		"dc=virtual,dc=naming,dc=context"
+relay		"dc=real,dc=naming,dc=context"
+rewriteContext	default
+rewriteRule	"(.*)dc=virtual,dc=naming,dc=context$" \
+			"$1dc=real,dc=naming,dc=context"
+rewriteContext	searchFilter
+rewriteContext	searchResult
+rewriteContext	searchResultAttrDN
+rewriteContext	matchedDN
+
diff --git a/servers/slapd/back-relay/back-relay.h b/servers/slapd/back-relay/back-relay.h
new file mode 100644
index 0000000..0a0a9bc
--- /dev/null
+++ b/servers/slapd/back-relay/back-relay.h
@@ -0,0 +1,49 @@
+/* back-relay.h - relay backend header file */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2004-2021 The OpenLDAP Foundation.
+ * Portions Copyright 2004 Pierangelo Masarati.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/* ACKNOWLEDGEMENTS:
+ * This work was initially developed by Pierangelo Masarati for inclusion
+ * in OpenLDAP Software.
+ */
+
+#ifndef SLAPD_RELAY_H
+#define SLAPD_RELAY_H
+
+#include "proto-back-relay.h"
+
+LDAP_BEGIN_DECL
+
+typedef enum relay_operation_e {
+	relay_op_entry_get = op_last,
+	relay_op_entry_release,
+	relay_op_has_subordinates,
+	relay_op_last
+} relay_operation_t;
+
+typedef struct relay_back_info {
+	BackendDB	*ri_bd;
+	struct berval	ri_realsuffix;
+	int		ri_massage;
+} relay_back_info;
+
+/* Pad relay_back_info if needed to create valid OpExtra key addresses */
+#define	RELAY_INFO_SIZE \
+	(sizeof(relay_back_info) > (size_t) relay_op_last ? \
+	 sizeof(relay_back_info) : (size_t) relay_op_last   )
+
+LDAP_END_DECL
+
+#endif /* SLAPD_RELAY_H */
diff --git a/servers/slapd/back-relay/init.c b/servers/slapd/back-relay/init.c
new file mode 100644
index 0000000..4e18381
--- /dev/null
+++ b/servers/slapd/back-relay/init.c
@@ -0,0 +1,254 @@
+/* init.c - initialize relay backend */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2004-2021 The OpenLDAP Foundation.
+ * Portions Copyright 2004 Pierangelo Masarati.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/* ACKNOWLEDGEMENTS:
+ * This work was initially developed by Pierangelo Masarati for inclusion
+ * in OpenLDAP Software.
+ */
+
+#include "portable.h"
+
+#include <stdio.h>
+#include <ac/string.h>
+
+#include "slap.h"
+#include "config.h"
+#include "back-relay.h"
+
+static ConfigDriver relay_back_cf;
+
+static ConfigTable relaycfg[] = {
+	{ "relay", "relay", 2, 2, 0,
+		ARG_MAGIC|ARG_DN|ARG_QUOTE,
+		relay_back_cf, "( OLcfgDbAt:5.1 "
+			"NAME 'olcRelay' "
+			"DESC 'Relay DN' "
+			"SYNTAX OMsDN "
+			"SINGLE-VALUE )",
+		NULL, NULL },
+	{ NULL }
+};
+
+static ConfigOCs relayocs[] = {
+	{ "( OLcfgDbOc:5.1 "
+		"NAME 'olcRelayConfig' "
+		"DESC 'Relay backend configuration' "
+		"SUP olcDatabaseConfig "
+		"MAY ( olcRelay "
+		") )",
+		 	Cft_Database, relaycfg},
+	{ NULL, 0, NULL }
+};
+
+static int
+relay_back_cf( ConfigArgs *c )
+{
+	relay_back_info	*ri = ( relay_back_info * )c->be->be_private;
+	int		rc = 0;
+
+	if ( c->op == SLAP_CONFIG_EMIT ) {
+		if ( ri != NULL && !BER_BVISNULL( &ri->ri_realsuffix ) ) {
+			value_add_one( &c->rvalue_vals, &ri->ri_realsuffix );
+			return 0;
+		}
+		return 1;
+
+	} else if ( c->op == LDAP_MOD_DELETE ) {
+		if ( !BER_BVISNULL( &ri->ri_realsuffix ) ) {
+			ch_free( ri->ri_realsuffix.bv_val );
+			BER_BVZERO( &ri->ri_realsuffix );
+			ri->ri_bd = NULL;
+			return 0;
+		}
+		return 1;
+
+	} else {
+		BackendDB *bd;
+
+		assert( ri != NULL );
+		assert( BER_BVISNULL( &ri->ri_realsuffix ) );
+
+		if ( c->be->be_nsuffix == NULL ) {
+			snprintf( c->cr_msg, sizeof( c->cr_msg),
+				"\"relay\" directive "
+				"must appear after \"suffix\"" );
+			Log2( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+				"%s: %s.\n", c->log, c->cr_msg );
+			rc = 1;
+			goto relay_done;
+		}
+
+		if ( !BER_BVISNULL( &c->be->be_nsuffix[ 1 ] ) ) {
+			snprintf( c->cr_msg, sizeof( c->cr_msg),
+				"relaying of multiple suffix "
+				"database not supported" );
+			Log2( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+				"%s: %s.\n", c->log, c->cr_msg );
+			rc = 1;
+			goto relay_done;
+		}
+
+		bd = select_backend( &c->value_ndn, 1 );
+		if ( bd == NULL ) {
+			snprintf( c->cr_msg, sizeof( c->cr_msg),
+				"cannot find database "
+				"of relay dn \"%s\" "
+				"in \"olcRelay <dn>\"\n",
+				c->value_dn.bv_val );
+			Log2( LDAP_DEBUG_CONFIG, LDAP_LEVEL_ERR,
+				"%s: %s.\n", c->log, c->cr_msg );
+
+		} else if ( bd->be_private == c->be->be_private ) {
+			snprintf( c->cr_msg, sizeof( c->cr_msg),
+				"relay dn \"%s\" would call self "
+				"in \"relay <dn>\" line\n",
+				c->value_dn.bv_val );
+			Log2( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+				"%s: %s.\n", c->log, c->cr_msg );
+			rc = 1;
+			goto relay_done;
+		}
+
+		ri->ri_realsuffix = c->value_ndn;
+		BER_BVZERO( &c->value_ndn );
+
+relay_done:;
+		ch_free( c->value_dn.bv_val );
+		ch_free( c->value_ndn.bv_val );
+	}
+
+	return rc;
+}
+
+int
+relay_back_initialize( BackendInfo *bi )
+{
+	bi->bi_init = 0;
+	bi->bi_open = 0;
+	bi->bi_config = 0;
+	bi->bi_close = 0;
+	bi->bi_destroy = 0;
+
+	bi->bi_db_init = relay_back_db_init;
+	bi->bi_db_config = config_generic_wrapper;
+	bi->bi_db_open = relay_back_db_open;
+#if 0
+	bi->bi_db_close = relay_back_db_close;
+#endif
+	bi->bi_db_destroy = relay_back_db_destroy;
+
+	bi->bi_op_bind = relay_back_op_bind;
+	bi->bi_op_search = relay_back_op_search;
+	bi->bi_op_compare = relay_back_op_compare;
+	bi->bi_op_modify = relay_back_op_modify;
+	bi->bi_op_modrdn = relay_back_op_modrdn;
+	bi->bi_op_add = relay_back_op_add;
+	bi->bi_op_delete = relay_back_op_delete;
+	bi->bi_extended = relay_back_op_extended;
+	bi->bi_entry_release_rw = relay_back_entry_release_rw;
+	bi->bi_entry_get_rw = relay_back_entry_get_rw;
+	bi->bi_operational = relay_back_operational;
+	bi->bi_has_subordinates = relay_back_has_subordinates;
+
+	bi->bi_cf_ocs = relayocs;
+
+	return config_register_schema( relaycfg, relayocs );
+}
+
+int
+relay_back_db_init( Backend *be, ConfigReply *cr)
+{
+	relay_back_info		*ri;
+
+	be->be_private = NULL;
+
+	ri = (relay_back_info *) ch_calloc( 1, RELAY_INFO_SIZE );
+	if ( ri == NULL ) {
+ 		return -1;
+ 	}
+
+	ri->ri_bd = NULL;
+	BER_BVZERO( &ri->ri_realsuffix );
+	ri->ri_massage = 0;
+
+	be->be_cf_ocs = be->bd_info->bi_cf_ocs;
+
+	be->be_private = (void *)ri;
+
+	return 0;
+}
+
+int
+relay_back_db_open( Backend *be, ConfigReply *cr )
+{
+	relay_back_info		*ri = (relay_back_info *)be->be_private;
+
+	assert( ri != NULL );
+
+	if ( !BER_BVISNULL( &ri->ri_realsuffix ) ) {
+		ri->ri_bd = select_backend( &ri->ri_realsuffix, 1 );
+
+		/* must be there: it was during config! */
+		if ( ri->ri_bd == NULL ) {
+			snprintf( cr->msg, sizeof( cr->msg),
+				"cannot find database "
+				"of relay dn \"%s\" "
+				"in \"olcRelay <dn>\"\n",
+				ri->ri_realsuffix.bv_val );
+			Log1( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+				"relay_back_db_open: %s.\n", cr->msg );
+
+			return 1;
+		}
+
+		/* inherit controls */
+		AC_MEMCPY( be->bd_self->be_ctrls, ri->ri_bd->be_ctrls, sizeof( be->be_ctrls ) );
+
+	} else {
+		/* inherit all? */
+		AC_MEMCPY( be->bd_self->be_ctrls, frontendDB->be_ctrls, sizeof( be->be_ctrls ) );
+	}
+
+	return 0;
+}
+
+int
+relay_back_db_close( Backend *be, ConfigReply *cr )
+{
+	return 0;
+}
+
+int
+relay_back_db_destroy( Backend *be, ConfigReply *cr)
+{
+	relay_back_info		*ri = (relay_back_info *)be->be_private;
+
+	if ( ri ) {
+		if ( !BER_BVISNULL( &ri->ri_realsuffix ) ) {
+			ch_free( ri->ri_realsuffix.bv_val );
+		}
+		ch_free( ri );
+	}
+
+	return 0;
+}
+
+#if SLAPD_RELAY == SLAPD_MOD_DYNAMIC
+
+/* conditionally define the init_module() function */
+SLAP_BACKEND_INIT_MODULE( relay )
+
+#endif /* SLAPD_RELAY == SLAPD_MOD_DYNAMIC */
diff --git a/servers/slapd/back-relay/op.c b/servers/slapd/back-relay/op.c
new file mode 100644
index 0000000..37112ae
--- /dev/null
+++ b/servers/slapd/back-relay/op.c
@@ -0,0 +1,331 @@
+/* op.c - relay backend operations */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2004-2021 The OpenLDAP Foundation.
+ * Portions Copyright 2004 Pierangelo Masarati.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/* ACKNOWLEDGEMENTS:
+ * This work was initially developed by Pierangelo Masarati for inclusion
+ * in OpenLDAP Software.
+ */
+
+#include "portable.h"
+
+#include <stdio.h>
+
+#include "slap.h"
+#include "back-relay.h"
+
+/* Results when no real database (.rf_bd) or operation handler (.rf_op) */
+static const struct relay_fail_modes_s {
+	slap_mask_t	rf_bd, rf_op;
+#define RB_ERR_MASK	0x0000FFFFU /* bitmask for default return value */
+#define RB_BDERR	0x80000000U /* use .rf_bd's default return value */
+#define RB_OPERR	0x40000000U /* set rs->sr_err = .rf_op return value */
+#define RB_REF		0x20000000U /* use default_referral if available */
+#define RB_SEND		0x10000000U /* send result; RB_??ERR is also set */
+#define RB_SENDREF	0/*unused*/ /* like RB_SEND when referral found */
+#define RB_NO_BIND	(RB_OPERR | LDAP_INVALID_CREDENTIALS)
+#define RB_NOT_SUPP	(RB_OPERR | LDAP_UNWILLING_TO_PERFORM)
+#define RB_NO_OBJ	(RB_REF | LDAP_NO_SUCH_OBJECT)
+#define RB_CHK_REF	(RB_REF | RB_SENDREF | LDAP_SUCCESS)
+} relay_fail_modes[relay_op_last] = {
+	/* .rf_bd is unused when zero, otherwise both fields have RB_BDERR */
+#	define RB_OP(b, o)	{ (b) | RB_BD2ERR(b), (o) | RB_BD2ERR(b) }
+#	define RB_BD2ERR(b)	((b) ? RB_BDERR : 0)
+	/* indexed by slap_operation_t: */
+	RB_OP(RB_NO_BIND|RB_SEND, RB_NO_BIND  |RB_SEND), /* Bind           */
+	RB_OP(0,                  LDAP_SUCCESS),         /* Unbind: unused */
+	RB_OP(RB_NO_OBJ |RB_SEND, RB_NOT_SUPP |RB_SEND), /* Search         */
+	RB_OP(RB_NO_OBJ |RB_SEND, SLAP_CB_CONTINUE),     /* Compare        */
+	RB_OP(RB_NO_OBJ |RB_SEND, RB_NOT_SUPP |RB_SEND), /* Modify         */
+	RB_OP(RB_NO_OBJ |RB_SEND, RB_NOT_SUPP |RB_SEND), /* Modrdn         */
+	RB_OP(RB_NO_OBJ |RB_SEND, RB_NOT_SUPP |RB_SEND), /* Add            */
+	RB_OP(RB_NO_OBJ |RB_SEND, RB_NOT_SUPP |RB_SEND), /* Delete         */
+	RB_OP(0,                  LDAP_SUCCESS),         /* Abandon:unused */
+	RB_OP(RB_NO_OBJ,          RB_NOT_SUPP),          /* Extended       */
+	RB_OP(0,                  SLAP_CB_CONTINUE),     /* Cancel: unused */
+	RB_OP(0,                  LDAP_SUCCESS),    /* operational         */
+	RB_OP(RB_CHK_REF,         LDAP_SUCCESS),    /* chk_referrals:unused*/
+	RB_OP(0,                  SLAP_CB_CONTINUE),/* chk_controls:unused */
+	/* additional relay_operation_t indexes from back-relay.h: */
+	RB_OP(0,                  0/*unused*/),     /* entry_get = op_last */
+	RB_OP(0,                  0/*unused*/),     /* entry_release       */
+	RB_OP(0,                  0/*unused*/),     /* has_subordinates    */
+};
+
+/*
+ * Callbacks: Caller changed op->o_bd from Relay to underlying
+ * BackendDB.  sc_response sets it to Relay BackendDB, sc_cleanup puts
+ * back underlying BackendDB.  Caller will restore Relay BackendDB.
+ */
+
+typedef struct relay_callback {
+	slap_callback rcb_sc;
+	BackendDB *rcb_bd;
+} relay_callback;
+
+static int
+relay_back_cleanup_cb( Operation *op, SlapReply *rs )
+{
+	op->o_bd = ((relay_callback *) op->o_callback)->rcb_bd;
+	return SLAP_CB_CONTINUE;
+}
+
+static int
+relay_back_response_cb( Operation *op, SlapReply *rs )
+{
+	relay_callback	*rcb = (relay_callback *) op->o_callback;
+
+	rcb->rcb_sc.sc_cleanup = relay_back_cleanup_cb;
+	rcb->rcb_bd = op->o_bd;
+	op->o_bd = op->o_callback->sc_private;
+	return SLAP_CB_CONTINUE;
+}
+
+#define relay_back_add_cb( rcb, op ) {				\
+		(rcb)->rcb_sc.sc_next = (op)->o_callback;	\
+		(rcb)->rcb_sc.sc_response = relay_back_response_cb; \
+		(rcb)->rcb_sc.sc_cleanup = 0;			\
+		(rcb)->rcb_sc.sc_writewait = 0;			\
+		(rcb)->rcb_sc.sc_private = (op)->o_bd;		\
+		(op)->o_callback = (slap_callback *) (rcb);	\
+}
+
+#define relay_back_remove_cb( rcb, op ) {			\
+		slap_callback	**sc = &(op)->o_callback;	\
+		for ( ;; sc = &(*sc)->sc_next )			\
+			if ( *sc == (slap_callback *) (rcb) ) {	\
+				*sc = (*sc)->sc_next; break;	\
+			} else if ( *sc == NULL ) break;	\
+}
+
+/*
+ * Select the backend database with the operation's DN.  On failure,
+ * set/send results depending on operation type <which>'s fail_modes.
+ */
+static BackendDB *
+relay_back_select_backend( Operation *op, SlapReply *rs, int which )
+{
+	OpExtra		*oex;
+	char		*key = (char *) op->o_bd->be_private;
+	BackendDB	*bd  = ((relay_back_info *) key)->ri_bd;
+	slap_mask_t	fail_mode = relay_fail_modes[which].rf_bd;
+	int		useDN = 0, rc = ( fail_mode & RB_ERR_MASK );
+
+	if ( bd == NULL && !BER_BVISNULL( &op->o_req_ndn ) ) {
+		useDN = 1;
+		bd = select_backend( &op->o_req_ndn, 1 );
+	}
+
+	if ( bd != NULL ) {
+		key += which; /* <relay, op type> key from RELAY_WRAP_OP() */
+		LDAP_SLIST_FOREACH( oex, &op->o_extra, oe_next ) {
+			if ( oex->oe_key == key )
+				break;
+		}
+		if ( oex == NULL ) {
+			return bd;
+		}
+
+		Debug( LDAP_DEBUG_ANY,
+			"%s: back-relay for DN=\"%s\" would call self.\n",
+			op->o_log_prefix, op->o_req_dn.bv_val, 0 );
+
+	} else if ( useDN && ( fail_mode & RB_REF ) && default_referral ) {
+		rc = LDAP_REFERRAL;
+
+		/* if we set sr_err to LDAP_REFERRAL, we must provide one */
+		rs->sr_ref = referral_rewrite(
+			default_referral, NULL, &op->o_req_dn,
+			op->o_tag == LDAP_REQ_SEARCH ?
+			op->ors_scope : LDAP_SCOPE_DEFAULT );
+		if ( rs->sr_ref != NULL ) {
+			rs->sr_flags |= REP_REF_MUSTBEFREED;
+		} else {
+			rs->sr_ref = default_referral;
+		}
+
+		if ( fail_mode & RB_SENDREF )
+			fail_mode = (RB_BDERR | RB_SEND);
+	}
+
+	if ( fail_mode & RB_BDERR ) {
+		rs->sr_err = rc;
+		if ( fail_mode & RB_SEND ) {
+			send_ldap_result( op, rs );
+		}
+	}
+
+	return NULL;
+}
+
+/*
+ * Forward <act> on <op> to database <bd>, with <relay, op type>-specific
+ * key in op->o_extra so relay_back_select_backend() can catch recursion.
+ */
+#define RELAY_WRAP_OP( op, bd, which, act ) { \
+	OpExtraDB wrap_oex; \
+	BackendDB *const wrap_bd = (op)->o_bd; \
+	wrap_oex.oe_db = wrap_bd; \
+	wrap_oex.oe.oe_key = (char *) wrap_bd->be_private + (which); \
+	LDAP_SLIST_INSERT_HEAD( &(op)->o_extra, &wrap_oex.oe, oe_next ); \
+	(op)->o_bd = (bd); \
+	act; \
+	(op)->o_bd = wrap_bd; \
+	LDAP_SLIST_REMOVE( &(op)->o_extra, &wrap_oex.oe, OpExtra, oe_next ); \
+}
+
+/*
+ * Forward backend function #<which> on <op> to operation DN's database
+ * like RELAY_WRAP_OP, after setting up callbacks. If no database or no
+ * backend function, set/send results depending on <which>'s fail_modes.
+ */
+static int
+relay_back_op( Operation *op, SlapReply *rs, int which )
+{
+	BackendDB	*bd;
+	BI_op_bind	*func;
+	slap_mask_t	fail_mode = relay_fail_modes[which].rf_op;
+	int		rc = ( fail_mode & RB_ERR_MASK );
+
+	bd = relay_back_select_backend( op, rs, which );
+	if ( bd == NULL ) {
+		if ( fail_mode & RB_BDERR )
+			return rs->sr_err;	/* sr_err was set above */
+
+	} else if ( (func = (&bd->be_bind)[which]) != 0 ) {
+		relay_callback	rcb;
+
+		relay_back_add_cb( &rcb, op );
+		RELAY_WRAP_OP( op, bd, which, {
+			rc = func( op, rs );
+		});
+		relay_back_remove_cb( &rcb, op );
+
+	} else if ( fail_mode & RB_OPERR ) {
+		rs->sr_err = rc;
+		if ( rc == LDAP_UNWILLING_TO_PERFORM ) {
+			rs->sr_text = "operation not supported within naming context";
+		}
+
+		if ( fail_mode & RB_SEND ) {
+			send_ldap_result( op, rs );
+		}
+	}
+
+	return rc;
+}
+
+
+int
+relay_back_op_bind( Operation *op, SlapReply *rs )
+{
+	/* allow rootdn as a means to auth without the need to actually
+ 	 * contact the proxied DSA */
+	switch ( be_rootdn_bind( op, rs ) ) {
+	case SLAP_CB_CONTINUE:
+		break;
+
+	default:
+		return rs->sr_err;
+	}
+
+	return relay_back_op( op, rs, op_bind );
+}
+
+#define RELAY_DEFOP(func, which) \
+	int func( Operation *op, SlapReply *rs ) \
+	{ return relay_back_op( op, rs, which ); }
+
+RELAY_DEFOP( relay_back_op_search,		op_search )
+RELAY_DEFOP( relay_back_op_compare,		op_compare )
+RELAY_DEFOP( relay_back_op_modify,		op_modify )
+RELAY_DEFOP( relay_back_op_modrdn,		op_modrdn )
+RELAY_DEFOP( relay_back_op_add,			op_add )
+RELAY_DEFOP( relay_back_op_delete,		op_delete )
+RELAY_DEFOP( relay_back_op_extended,	op_extended )
+RELAY_DEFOP( relay_back_operational,	op_aux_operational )
+
+/* Abandon, Cancel, Unbind and some DN-less calls like be_connection_init
+ * need no extra handling:  slapd already calls them for all databases.
+ */
+
+
+int
+relay_back_entry_release_rw( Operation *op, Entry *e, int rw )
+{
+	BackendDB		*bd;
+	int			rc = LDAP_UNWILLING_TO_PERFORM;
+
+	bd = relay_back_select_backend( op, NULL, relay_op_entry_release );
+	if ( bd && bd->be_release ) {
+		RELAY_WRAP_OP( op, bd, relay_op_entry_release, {
+			rc = bd->be_release( op, e, rw );
+		});
+	} else if ( e->e_private == NULL ) {
+		entry_free( e );
+		rc = LDAP_SUCCESS;
+	}
+
+	return rc;
+}
+
+int
+relay_back_entry_get_rw( Operation *op, struct berval *ndn,
+	ObjectClass *oc, AttributeDescription *at, int rw, Entry **e )
+{
+	BackendDB		*bd;
+	int			rc = LDAP_NO_SUCH_OBJECT;
+
+	bd = relay_back_select_backend( op, NULL, relay_op_entry_get );
+	if ( bd && bd->be_fetch ) {
+		RELAY_WRAP_OP( op, bd, relay_op_entry_get, {
+			rc = bd->be_fetch( op, ndn, oc, at, rw, e );
+		});
+	}
+
+	return rc;
+}
+
+#if 0 /* Give the RB_SENDREF flag a nonzero value if implementing this */
+/*
+ * NOTE: even the existence of this function is questionable: we cannot
+ * pass the bi_chk_referrals() call thru the rwm overlay because there
+ * is no way to rewrite the req_dn back; but then relay_back_chk_referrals()
+ * is passing the target database a DN that likely does not belong to its
+ * naming context... mmmh.
+ */
+RELAY_DEFOP( relay_back_chk_referrals, op_aux_chk_referrals )
+#endif /*0*/
+
+int
+relay_back_has_subordinates( Operation *op, Entry *e, int *hasSubs )
+{
+	BackendDB		*bd;
+	int			rc = LDAP_OTHER;
+
+	bd = relay_back_select_backend( op, NULL, relay_op_has_subordinates );
+	if ( bd && bd->be_has_subordinates ) {
+		RELAY_WRAP_OP( op, bd, relay_op_has_subordinates, {
+			rc = bd->be_has_subordinates( op, e, hasSubs );
+		});
+	}
+
+	return rc;
+}
+
+
+/*
+ * FIXME: must implement tools as well
+ */
diff --git a/servers/slapd/back-relay/proto-back-relay.h b/servers/slapd/back-relay/proto-back-relay.h
new file mode 100644
index 0000000..5ed71aa
--- /dev/null
+++ b/servers/slapd/back-relay/proto-back-relay.h
@@ -0,0 +1,52 @@
+/* proto-back-relay.h - relay backend header file */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2004-2021 The OpenLDAP Foundation.
+ * Portions Copyright 2004 Pierangelo Masarati.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/* ACKNOWLEDGEMENTS:
+ * This work was initially developed by Pierangelo Masarati for inclusion
+ * in OpenLDAP Software.
+ */
+
+#ifndef PROTO_BACK_RELAY
+#define PROTO_BACK_RELAY
+
+#include <ldap_cdefs.h>
+
+LDAP_BEGIN_DECL
+
+extern BI_init			relay_back_initialize;
+
+extern BI_db_init		relay_back_db_init;
+extern BI_db_open		relay_back_db_open;
+extern BI_db_close		relay_back_db_close;
+extern BI_db_destroy		relay_back_db_destroy;
+
+extern BI_op_bind		relay_back_op_bind;
+extern BI_op_search		relay_back_op_search;
+extern BI_op_compare		relay_back_op_compare;
+extern BI_op_modify		relay_back_op_modify;
+extern BI_op_modrdn		relay_back_op_modrdn;
+extern BI_op_add		relay_back_op_add;
+extern BI_op_delete		relay_back_op_delete;
+extern BI_op_extended		relay_back_op_extended;
+extern BI_entry_release_rw	relay_back_entry_release_rw;
+extern BI_entry_get_rw		relay_back_entry_get_rw;
+extern BI_operational		relay_back_operational;
+extern BI_has_subordinates	relay_back_has_subordinates;
+
+LDAP_END_DECL
+
+#endif /* PROTO_BACK_RELAY */
+