librpc/rpc/dcerpc_util.c

/*
   Unix SMB/CIFS implementation.

   dcerpc utility functions

   Copyright (C) Andrew Tridgell 2003
   Copyright (C) Jelmer Vernooij 2004
   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005
   Copyright (C) Rafal Szczesniak 2006

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "lib/events/events.h"
#include "libcli/composite/composite.h"
#include "librpc/gen_ndr/ndr_epmapper_c.h"
#include "librpc/gen_ndr/ndr_dcerpc.h"
#include "librpc/gen_ndr/ndr_misc.h"
#include "librpc/rpc/dcerpc_proto.h"
#include "auth/credentials/credentials.h"
#include "auth/gensec/gensec.h"
#include "param/param.h"
#include "librpc/rpc/rpc_common.h"

/*
  find a dcerpc call on an interface by name
*/
const struct ndr_interface_call *dcerpc_iface_find_call(const struct ndr_interface_table *iface,
							const char *name)
{
	int i;
	for (i=0;i<iface->num_calls;i++) {
		if (strcmp(iface->calls[i].name, name) == 0) {
			return &iface->calls[i];
		}
	}
	return NULL;
}

struct epm_map_binding_state {
	struct dcerpc_binding *binding;
	const struct ndr_interface_table *table;
	struct dcerpc_pipe *pipe;
	struct policy_handle handle;
	struct GUID object;
	struct epm_twr_t twr;
	struct epm_twr_t *twr_r;
	uint32_t num_towers;
	struct epm_Map r;
};


static void continue_epm_recv_binding(struct composite_context *ctx);
static void continue_epm_map(struct tevent_req *subreq);


/*
  Stage 2 of epm_map_binding: Receive connected rpc pipe and send endpoint
  mapping rpc request
*/
static void continue_epm_recv_binding(struct composite_context *ctx)
{
	struct composite_context *c = talloc_get_type(ctx->async.private_data,
						      struct composite_context);
	struct epm_map_binding_state *s = talloc_get_type(c->private_data,
							  struct epm_map_binding_state);
	struct tevent_req *subreq;

	/* receive result of rpc pipe connect request */
	c->status = dcerpc_pipe_connect_b_recv(ctx, c, &s->pipe);
	if (!composite_is_ok(c)) return;

	c->status = dcerpc_binding_build_tower(s->pipe, s->binding, &s->twr.tower);
	if (!composite_is_ok(c)) return;

	/* with some nice pretty paper around it of course */
	s->r.in.object        = &s->object;
	s->r.in.map_tower     = &s->twr;
	s->r.in.entry_handle  = &s->handle;
	s->r.in.max_towers    = 1;
	s->r.out.entry_handle = &s->handle;
	s->r.out.num_towers   = &s->num_towers;

	/* send request for an endpoint mapping - a rpc request on connected pipe */
	subreq = dcerpc_epm_Map_r_send(s, c->event_ctx,
				       s->pipe->binding_handle,
				       &s->r);
	if (composite_nomem(subreq, c)) return;

	tevent_req_set_callback(subreq, continue_epm_map, c);
}


/*
  Stage 3 of epm_map_binding: Receive endpoint mapping and provide binding details
*/
static void continue_epm_map(struct tevent_req *subreq)
{
	struct composite_context *c = tevent_req_callback_data(subreq,
				      struct composite_context);
	struct epm_map_binding_state *s = talloc_get_type(c->private_data,
							  struct epm_map_binding_state);
	const char *endpoint;

	/* receive result of a rpc request */
	c->status = dcerpc_epm_Map_r_recv(subreq, s);
	TALLOC_FREE(subreq);
	if (!composite_is_ok(c)) return;

	/* check the details */
	if (s->r.out.result != 0 || *s->r.out.num_towers != 1) {
		composite_error(c, NT_STATUS_PORT_UNREACHABLE);
		return;
	}

	s->twr_r = s->r.out.towers[0].twr;
	if (s->twr_r == NULL) {
		composite_error(c, NT_STATUS_PORT_UNREACHABLE);
		return;
	}

	if (s->twr_r->tower.num_floors != s->twr.tower.num_floors ||
	    s->twr_r->tower.floors[3].lhs.protocol != s->twr.tower.floors[3].lhs.protocol) {
		composite_error(c, NT_STATUS_PORT_UNREACHABLE);
		return;
	}

	/* get received endpoint */
	endpoint = dcerpc_floor_get_rhs_data(s, &s->twr_r->tower.floors[3]);
	if (composite_nomem(endpoint, c)) return;

	c->status = dcerpc_binding_set_string_option(s->binding,
						     "endpoint",
						     endpoint);
	if (!composite_is_ok(c)) {
		return;
	}

	composite_done(c);
}


/*
  Request for endpoint mapping of dcerpc binding - try to request for endpoint
  unless there is default one.
*/
struct composite_context *dcerpc_epm_map_binding_send(TALLOC_CTX *mem_ctx,
						      struct dcerpc_binding *binding,
						      const struct ndr_interface_table *table,
						      struct cli_credentials *creds,
						      struct tevent_context *ev,
						      struct loadparm_context *lp_ctx)
{
	struct composite_context *c;
	struct epm_map_binding_state *s;
	struct composite_context *pipe_connect_req;
	NTSTATUS status;
	struct dcerpc_binding *epmapper_binding;
	int i;

	if (ev == NULL) {
		return NULL;
	}

	/* composite context allocation and setup */
	c = composite_create(mem_ctx, ev);
	if (c == NULL) {
		return NULL;
	}

	s = talloc_zero(c, struct epm_map_binding_state);
	if (composite_nomem(s, c)) return c;
	c->private_data = s;

	s->binding = binding;
	s->object  = dcerpc_binding_get_object(binding);
	s->table   = table;

	c->status = dcerpc_binding_set_abstract_syntax(binding,
						       &table->syntax_id);
	if (!composite_is_ok(c)) {
		return c;
	}

	/*
	  First, check if there is a default endpoint specified in the IDL
	*/
	for (i = 0; i < table->endpoints->count; i++) {
		struct dcerpc_binding *default_binding;
		enum dcerpc_transport_t transport;
		enum dcerpc_transport_t dtransport;
		const char *dendpoint = NULL;

		status = dcerpc_parse_binding(s,
					      table->endpoints->names[i],
					      &default_binding);
		if (!NT_STATUS_IS_OK(status)) {
			continue;
		}

		transport = dcerpc_binding_get_transport(binding);
		dtransport = dcerpc_binding_get_transport(default_binding);
		if (transport == NCA_UNKNOWN) {
			c->status = dcerpc_binding_set_transport(binding,
								 dtransport);
			if (!composite_is_ok(c)) {
				return c;
			}
			transport = dtransport;
		}

		if (transport != dtransport) {
			TALLOC_FREE(default_binding);
			continue;
		}

		dendpoint = dcerpc_binding_get_string_option(default_binding,
							     "endpoint");
		if (dendpoint == NULL) {
			TALLOC_FREE(default_binding);
			continue;
		}

		c->status = dcerpc_binding_set_string_option(binding,
							     "endpoint",
							     dendpoint);
		if (!composite_is_ok(c)) {
			return c;
		}

		TALLOC_FREE(default_binding);
		composite_done(c);
		return c;
	}

	epmapper_binding = dcerpc_binding_dup(s, binding);
	if (composite_nomem(epmapper_binding, c)) return c;

	/* basic endpoint mapping data */
	c->status = dcerpc_binding_set_string_option(epmapper_binding,
						     "endpoint", NULL);
	if (!composite_is_ok(c)) {
		return c;
	}
	c->status = dcerpc_binding_set_flags(epmapper_binding, 0, UINT32_MAX);
	if (!composite_is_ok(c)) {
		return c;
	}
	c->status = dcerpc_binding_set_assoc_group_id(epmapper_binding, 0);
	if (!composite_is_ok(c)) {
		return c;
	}
	c->status = dcerpc_binding_set_object(epmapper_binding, GUID_zero());
	if (!composite_is_ok(c)) {
		return c;
	}

	/* initiate rpc pipe connection */
	pipe_connect_req = dcerpc_pipe_connect_b_send(s, epmapper_binding,
						      &ndr_table_epmapper,
						      creds, c->event_ctx,
						      lp_ctx);
	if (composite_nomem(pipe_connect_req, c)) return c;

	composite_continue(c, pipe_connect_req, continue_epm_recv_binding, c);
	return c;
}


/*
  Receive result of endpoint mapping request
 */
NTSTATUS dcerpc_epm_map_binding_recv(struct composite_context *c)
{
	NTSTATUS status = composite_wait(c);

	talloc_free(c);
	return status;
}


/*
  Get endpoint mapping for rpc connection
*/
_PUBLIC_ NTSTATUS dcerpc_epm_map_binding(TALLOC_CTX *mem_ctx, struct dcerpc_binding *binding,
				const struct ndr_interface_table *table, struct tevent_context *ev,
				struct loadparm_context *lp_ctx)
{
	struct composite_context *c;
	struct cli_credentials *epm_creds;

	epm_creds = cli_credentials_init_anon(mem_ctx);
	if (epm_creds == NULL) {
		return NT_STATUS_NO_MEMORY;
	}
	c = dcerpc_epm_map_binding_send(mem_ctx, binding, table, epm_creds, ev, lp_ctx);
	if (c == NULL) {
		talloc_free(epm_creds);
		return NT_STATUS_NO_MEMORY;
	}
	talloc_steal(c, epm_creds);
	return dcerpc_epm_map_binding_recv(c);
}


struct pipe_auth_state {
	struct dcerpc_pipe *pipe;
	const struct dcerpc_binding *binding;
	const struct ndr_interface_table *table;
	struct loadparm_context *lp_ctx;
	struct cli_credentials *credentials;
	unsigned int logon_retries;
};


static void continue_auth_schannel(struct composite_context *ctx);
static void continue_auth(struct composite_context *ctx);
static void continue_auth_none(struct composite_context *ctx);
static void continue_ntlmssp_connection(struct composite_context *ctx);
static void continue_spnego_after_wrong_pass(struct composite_context *ctx);


/*
  Stage 2 of pipe_auth: Receive result of schannel bind request
*/
static void continue_auth_schannel(struct composite_context *ctx)
{
	struct composite_context *c = talloc_get_type(ctx->async.private_data,
						      struct composite_context);

	c->status = dcerpc_bind_auth_schannel_recv(ctx);
	if (!composite_is_ok(c)) return;

	composite_done(c);
}


/*
  Stage 2 of pipe_auth: Receive result of authenticated bind request
*/
static void continue_auth(struct composite_context *ctx)
{
	struct composite_context *c = talloc_get_type(ctx->async.private_data,
						      struct composite_context);

	c->status = dcerpc_bind_auth_recv(ctx);
	if (!composite_is_ok(c)) return;

	composite_done(c);
}
/*
  Stage 2 of pipe_auth: Receive result of authenticated bind request, but handle fallbacks:
  SPNEGO -> NTLMSSP
*/
static void continue_auth_auto(struct composite_context *ctx)
{
	struct composite_context *c = talloc_get_type(ctx->async.private_data,
						      struct composite_context);
	struct pipe_auth_state *s = talloc_get_type(c->private_data, struct pipe_auth_state);
	struct composite_context *sec_conn_req;

	c->status = dcerpc_bind_auth_recv(ctx);
	if (NT_STATUS_EQUAL(c->status, NT_STATUS_INVALID_PARAMETER)) {
		/*
		 * Retry with NTLMSSP auth as fallback
		 * send a request for secondary rpc connection
		 */
		sec_conn_req = dcerpc_secondary_connection_send(s->pipe,
								s->binding);
		composite_continue(c, sec_conn_req, continue_ntlmssp_connection, c);
		return;
	} else if (NT_STATUS_EQUAL(c->status, NT_STATUS_LOGON_FAILURE) ||
		   NT_STATUS_EQUAL(c->status, NT_STATUS_UNSUCCESSFUL)) {
		/*
		  try a second time on any error. We don't just do it
		  on LOGON_FAILURE as some servers will give a
		  NT_STATUS_UNSUCCESSFUL on a authentication error on RPC
		 */
		const char *principal;
		const char *endpoint;

		principal = gensec_get_target_principal(s->pipe->conn->security_state.generic_state);
		if (principal == NULL) {
			const char *hostname = gensec_get_target_hostname(s->pipe->conn->security_state.generic_state);
			const char *service  = gensec_get_target_service(s->pipe->conn->security_state.generic_state);
			if (hostname != NULL && service != NULL) {
				principal = talloc_asprintf(c, "%s/%s", service, hostname);
			}
		}

		endpoint = dcerpc_binding_get_string_option(s->binding, "endpoint");

		if ((cli_credentials_failed_kerberos_login(s->credentials, principal, &s->logon_retries) ||
		     cli_credentials_wrong_password(s->credentials)) &&
		    endpoint != NULL) {
			/*
			 * Retry SPNEGO with a better password
			 * send a request for secondary rpc connection
			 */
			sec_conn_req = dcerpc_secondary_connection_send(s->pipe,
									s->binding);
			composite_continue(c, sec_conn_req, continue_spnego_after_wrong_pass, c);
			return;
		}
	}

	if (!composite_is_ok(c)) return;

	composite_done(c);
}

/*
  Stage 3 of pipe_auth (fallback to NTLMSSP case): Receive secondary
  rpc connection (the first one can't be used any more, due to the
  bind nak) and perform authenticated bind request
*/
static void continue_ntlmssp_connection(struct composite_context *ctx)
{
	struct composite_context *c;
	struct pipe_auth_state *s;
	struct composite_context *auth_req;
	struct dcerpc_pipe *p2;
	void *pp;

	c = talloc_get_type(ctx->async.private_data, struct composite_context);
	s = talloc_get_type(c->private_data, struct pipe_auth_state);

	/* receive secondary rpc connection */
	c->status = dcerpc_secondary_connection_recv(ctx, &p2);
	if (!composite_is_ok(c)) return;


	/* this is a rather strange situation. When
	   we come into the routine, s is a child of s->pipe, and
	   when we created p2 above, it also became a child of
	   s->pipe.

	   Now we want p2 to be a parent of s->pipe, and we want s to
	   be a parent of both of them! If we don't do this very
	   carefully we end up creating a talloc loop
	*/

	/* we need the new contexts to hang off the same context
	   that s->pipe is on, but the only way to get that is
	   via talloc_parent() */
	pp = talloc_parent(s->pipe);

	/* promote s to be at the top */
	talloc_steal(pp, s);

	/* and put p2 under s */
	talloc_steal(s, p2);

	/* now put s->pipe under p2 */
	talloc_steal(p2, s->pipe);

	s->pipe = p2;

	/* initiate a authenticated bind */
	auth_req = dcerpc_bind_auth_send(c, s->pipe, s->table,
					 s->credentials,
					 lpcfg_gensec_settings(c, s->lp_ctx),
					 DCERPC_AUTH_TYPE_NTLMSSP,
					 dcerpc_auth_level(s->pipe->conn),
					 s->table->authservices->names[0]);
	composite_continue(c, auth_req, continue_auth, c);
}

/*
  Stage 3 of pipe_auth (retry on wrong password): Receive secondary
  rpc connection (the first one can't be used any more, due to the
  bind nak) and perform authenticated bind request
*/
static void continue_spnego_after_wrong_pass(struct composite_context *ctx)
{
	struct composite_context *c;
	struct pipe_auth_state *s;
	struct composite_context *auth_req;
	struct dcerpc_pipe *p2;

	c = talloc_get_type(ctx->async.private_data, struct composite_context);
	s = talloc_get_type(c->private_data, struct pipe_auth_state);

	/* receive secondary rpc connection */
	c->status = dcerpc_secondary_connection_recv(ctx, &p2);
	if (!composite_is_ok(c)) return;

	talloc_steal(s, p2);
	talloc_steal(p2, s->pipe);
	s->pipe = p2;

	/* initiate a authenticated bind */
	auth_req = dcerpc_bind_auth_send(c, s->pipe, s->table,
					 s->credentials,
					 lpcfg_gensec_settings(c, s->lp_ctx),
					 DCERPC_AUTH_TYPE_SPNEGO,
					 dcerpc_auth_level(s->pipe->conn),
					 s->table->authservices->names[0]);
	composite_continue(c, auth_req, continue_auth, c);
}


/*
  Stage 2 of pipe_auth: Receive result of non-authenticated bind request
*/
static void continue_auth_none(struct composite_context *ctx)
{
	struct composite_context *c = talloc_get_type(ctx->async.private_data,
						      struct composite_context);

	c->status = dcerpc_bind_auth_none_recv(ctx);
	if (!composite_is_ok(c)) return;

	composite_done(c);
}


/*
  Request to perform an authenticated bind if required. Authentication
  is determined using credentials passed and binding flags.
*/
struct composite_context *dcerpc_pipe_auth_send(struct dcerpc_pipe *p,
						const struct dcerpc_binding *binding,
						const struct ndr_interface_table *table,
						struct cli_credentials *credentials,
						struct loadparm_context *lp_ctx)
{
	struct composite_context *c;
	struct pipe_auth_state *s;
	struct composite_context *auth_schannel_req;
	struct composite_context *auth_req;
	struct composite_context *auth_none_req;
	struct dcecli_connection *conn;
	uint8_t auth_type;

	/* composite context allocation and setup */
	c = composite_create(p, p->conn->event_ctx);
	if (c == NULL) return NULL;

	s = talloc_zero(c, struct pipe_auth_state);
	if (composite_nomem(s, c)) return c;
	c->private_data = s;

	/* store parameters in state structure */
	s->binding      = binding;
	s->table        = table;
	s->credentials  = credentials;
	s->pipe         = p;
	s->lp_ctx       = lp_ctx;

	conn = s->pipe->conn;
	conn->flags = dcerpc_binding_get_flags(binding);

	if (DEBUGLVL(100)) {
		conn->flags |= DCERPC_DEBUG_PRINT_BOTH;
	}

	if (conn->transport.transport == NCALRPC) {
		const char *v = dcerpc_binding_get_string_option(binding,
							"auth_type");

		if (v != NULL && strcmp(v, "ncalrpc_as_system") == 0) {
			auth_req = dcerpc_bind_auth_send(c, s->pipe, s->table,
						 s->credentials,
						 lpcfg_gensec_settings(c, s->lp_ctx),
						 DCERPC_AUTH_TYPE_NCALRPC_AS_SYSTEM,
						 DCERPC_AUTH_LEVEL_CONNECT,
						 s->table->authservices->names[0]);
			composite_continue(c, auth_req, continue_auth, c);
			return c;
		}
	}

	if (cli_credentials_is_anonymous(s->credentials)) {
		auth_none_req = dcerpc_bind_auth_none_send(c, s->pipe, s->table);
		composite_continue(c, auth_none_req, continue_auth_none, c);
		return c;
	}

	if ((conn->flags & DCERPC_SCHANNEL) &&
	    !cli_credentials_get_netlogon_creds(s->credentials)) {
		/* If we don't already have netlogon credentials for
		 * the schannel bind, then we have to get these
		 * first */
		auth_schannel_req = dcerpc_bind_auth_schannel_send(c, s->pipe, s->table,
								   s->credentials, s->lp_ctx,
								   dcerpc_auth_level(conn));
		composite_continue(c, auth_schannel_req, continue_auth_schannel, c);
		return c;
	}

	/*
	 * we rely on the already authenticated CIFS connection
	 * if not doing sign or seal
	 */
	if (conn->transport.transport == NCACN_NP &&
	    !(conn->flags & (DCERPC_PACKET|DCERPC_SIGN|DCERPC_SEAL))) {
		auth_none_req = dcerpc_bind_auth_none_send(c, s->pipe, s->table);
		composite_continue(c, auth_none_req, continue_auth_none, c);
		return c;
	}


	/* Perform an authenticated DCE-RPC bind
	 */
	if (!(conn->flags & (DCERPC_CONNECT|DCERPC_SEAL|DCERPC_PACKET))) {
		/*
		  we are doing an authenticated connection,
		  which needs to use [connect], [sign] or [seal].
		  If nothing is specified, we default to [sign] now.
		  This give roughly the same protection as
		  ncacn_np with smb signing.
		*/
		conn->flags |= DCERPC_SIGN;
	}

	if (conn->flags & DCERPC_AUTH_SPNEGO) {
		auth_type = DCERPC_AUTH_TYPE_SPNEGO;

	} else if (conn->flags & DCERPC_AUTH_KRB5) {
		auth_type = DCERPC_AUTH_TYPE_KRB5;

	} else if (conn->flags & DCERPC_SCHANNEL) {
		auth_type = DCERPC_AUTH_TYPE_SCHANNEL;

	} else if (conn->flags & DCERPC_AUTH_NTLM) {
		auth_type = DCERPC_AUTH_TYPE_NTLMSSP;

	} else {
		/* try SPNEGO with fallback to NTLMSSP */
		auth_req = dcerpc_bind_auth_send(c, s->pipe, s->table,
						 s->credentials,
						 lpcfg_gensec_settings(c, s->lp_ctx),
						 DCERPC_AUTH_TYPE_SPNEGO,
						 dcerpc_auth_level(conn),
						 s->table->authservices->names[0]);
		composite_continue(c, auth_req, continue_auth_auto, c);
		return c;
	}

	auth_req = dcerpc_bind_auth_send(c, s->pipe, s->table,
					 s->credentials,
					 lpcfg_gensec_settings(c, s->lp_ctx),
					 auth_type,
					 dcerpc_auth_level(conn),
					 s->table->authservices->names[0]);
	composite_continue(c, auth_req, continue_auth, c);
	return c;
}


/*
  Receive result of authenticated bind request on dcerpc pipe

  This returns *p, which may be different to the one originally
  supllied, as it rebinds to a new pipe due to authentication fallback

*/
NTSTATUS dcerpc_pipe_auth_recv(struct composite_context *c, TALLOC_CTX *mem_ctx,
			       struct dcerpc_pipe **p)
{
	NTSTATUS status;

	struct pipe_auth_state *s = talloc_get_type(c->private_data,
						    struct pipe_auth_state);
	status = composite_wait(c);
	if (!NT_STATUS_IS_OK(status)) {
		char *uuid_str = GUID_string(s->pipe, &s->table->syntax_id.uuid);
		DEBUG(0, ("Failed to bind to uuid %s for %s %s\n", uuid_str,
			  dcerpc_binding_string(uuid_str, s->binding), nt_errstr(status)));
		talloc_free(uuid_str);
	} else {
		talloc_steal(mem_ctx, s->pipe);
		*p = s->pipe;
	}

	talloc_free(c);
	return status;
}


/*
   Perform an authenticated bind if needed - sync version

   This may change *p, as it rebinds to a new pipe due to authentication fallback
*/
_PUBLIC_ NTSTATUS dcerpc_pipe_auth(TALLOC_CTX *mem_ctx,
			  struct dcerpc_pipe **p,
			  const struct dcerpc_binding *binding,
			  const struct ndr_interface_table *table,
			  struct cli_credentials *credentials,
			  struct loadparm_context *lp_ctx)
{
	struct composite_context *c;

	c = dcerpc_pipe_auth_send(*p, binding, table, credentials, lp_ctx);
	return dcerpc_pipe_auth_recv(c, mem_ctx, p);
}


NTSTATUS dcecli_generic_session_key(struct dcecli_connection *c,
				    DATA_BLOB *session_key)
{
	if (c != NULL) {
		if (c->transport.transport != NCALRPC &&
		    c->transport.transport != NCACN_UNIX_STREAM)
		{
			return NT_STATUS_LOCAL_USER_SESSION_KEY;
		}
	}

	return dcerpc_generic_session_key(session_key);
}

/*
  fetch the user session key - may be default (above) or the SMB session key

  The key is always truncated to 16 bytes
*/
_PUBLIC_ NTSTATUS dcerpc_fetch_session_key(struct dcerpc_pipe *p,
					   DATA_BLOB *session_key)
{
	NTSTATUS status;
	status = p->conn->security_state.session_key(p->conn, session_key);
	if (!NT_STATUS_IS_OK(status)) {
		return status;
	}

	session_key->length = MIN(session_key->length, 16);

	return NT_STATUS_OK;
}

/*
  create a secondary context from a primary connection

  this uses dcerpc_alter_context() to create a new dcerpc context_id
*/
_PUBLIC_ NTSTATUS dcerpc_secondary_context(struct dcerpc_pipe *p,
				  struct dcerpc_pipe **pp2,
				  const struct ndr_interface_table *table)
{
	NTSTATUS status;
	struct dcerpc_pipe *p2;
	struct GUID *object = NULL;

	p2 = talloc_zero(p, struct dcerpc_pipe);
	if (p2 == NULL) {
		return NT_STATUS_NO_MEMORY;
	}
	p2->conn = talloc_reference(p2, p->conn);
	p2->request_timeout = p->request_timeout;

	p2->context_id = ++p->conn->next_context_id;

	p2->syntax = table->syntax_id;

	p2->transfer_syntax = p->transfer_syntax;

	p2->binding = dcerpc_binding_dup(p2, p->binding);
	if (p2->binding == NULL) {
		talloc_free(p2);
		return NT_STATUS_NO_MEMORY;
	}

	p2->object = dcerpc_binding_get_object(p2->binding);
	if (!GUID_all_zero(&p2->object)) {
		object = &p2->object;
	}

	p2->binding_handle = dcerpc_pipe_binding_handle(p2, object, table);
	if (p2->binding_handle == NULL) {
		talloc_free(p2);
		return NT_STATUS_NO_MEMORY;
	}

	status = dcerpc_alter_context(p2, p2, &p2->syntax, &p2->transfer_syntax);
	if (!NT_STATUS_IS_OK(status)) {
		talloc_free(p2);
		return status;
	}

	*pp2 = p2;

	return NT_STATUS_OK;
}