source: branches/samba-3.5.x/source4/librpc/rpc/dcerpc_connect.c

/* 
   Unix SMB/CIFS implementation.

   dcerpc connect functions

   Copyright (C) Andrew Tridgell 2003
   Copyright (C) Jelmer Vernooij 2004
   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005-2007
   Copyright (C) Rafal Szczesniak  2005
   
   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 "libcli/composite/composite.h"
#include "libcli/smb_composite/smb_composite.h"
#include "lib/events/events.h"
#include "libcli/smb2/smb2.h"
#include "libcli/smb2/smb2_calls.h"
#include "librpc/rpc/dcerpc.h"
#include "librpc/rpc/dcerpc_proto.h"
#include "auth/credentials/credentials.h"
#include "param/param.h"
#include "libcli/resolve/resolve.h"


struct pipe_np_smb_state {
        struct smb_composite_connect conn;
        struct smbcli_tree *tree;
        struct dcerpc_pipe_connect io;
};


/*
  Stage 3 of ncacn_np_smb: Named pipe opened (or not)
*/
static void continue_pipe_open_smb(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);

        /* receive result of named pipe open request on smb */
        c->status = dcerpc_pipe_open_smb_recv(ctx);
        if (!composite_is_ok(c)) return;

        composite_done(c);
}


/*
  Stage 2 of ncacn_np_smb: Open a named pipe after successful smb connection
*/
static void continue_smb_connect(struct composite_context *ctx)
{
        struct composite_context *open_ctx;
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_np_smb_state *s = talloc_get_type(c->private_data,
                                                      struct pipe_np_smb_state);
        
        /* receive result of smb connect request */
        c->status = smb_composite_connect_recv(ctx, c);
        if (!composite_is_ok(c)) return;

        /* prepare named pipe open parameters */
        s->tree         = s->conn.out.tree;
        s->io.pipe_name = s->io.binding->endpoint;

        /* send named pipe open request */
        open_ctx = dcerpc_pipe_open_smb_send(s->io.pipe, s->tree, s->io.pipe_name);
        if (composite_nomem(open_ctx, c)) return;

        composite_continue(c, open_ctx, continue_pipe_open_smb, c);
}


/*
  Initiate async open of a rpc connection to a rpc pipe on SMB using
  the binding structure to determine the endpoint and options
*/
static struct composite_context *dcerpc_pipe_connect_ncacn_np_smb_send(TALLOC_CTX *mem_ctx, struct dcerpc_pipe_connect *io, struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        struct pipe_np_smb_state *s;
        struct composite_context *conn_req;
        struct smb_composite_connect *conn;

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

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

        s->io  = *io;
        conn   = &s->conn;

        /* prepare smb connection parameters: we're connecting to IPC$ share on
           remote rpc server */
        conn->in.dest_host              = s->io.binding->host;
        conn->in.dest_ports                  = lp_smb_ports(lp_ctx);
        if (s->io.binding->target_hostname == NULL)
                conn->in.called_name = "*SMBSERVER"; /* FIXME: This is invalid */
        else
                conn->in.called_name            = s->io.binding->target_hostname;
        conn->in.socket_options         = lp_socket_options(lp_ctx);
        conn->in.service                = "IPC$";
        conn->in.service_type           = NULL;
        conn->in.workgroup              = lp_workgroup(lp_ctx);
        conn->in.gensec_settings = lp_gensec_settings(conn, lp_ctx);
        conn->in.iconv_convenience = lp_iconv_convenience(lp_ctx);

        lp_smbcli_options(lp_ctx, &conn->in.options);
        lp_smbcli_session_options(lp_ctx, &conn->in.session_options);

        /*
         * provide proper credentials - user supplied, but allow a
         * fallback to anonymous if this is an schannel connection
         * (might be NT4 not allowing machine logins at session
         * setup) or if asked to do so by the caller (perhaps a SAMR password change?)
         */
        s->conn.in.credentials = s->io.creds;
        if (s->io.binding->flags & (DCERPC_SCHANNEL|DCERPC_ANON_FALLBACK)) {
                conn->in.fallback_to_anonymous  = true;
        } else {
                conn->in.fallback_to_anonymous  = false;
        }

        /* send smb connect request */
        conn_req = smb_composite_connect_send(conn, s->io.pipe->conn, 
                                              s->io.resolve_ctx,
                                              s->io.pipe->conn->event_ctx);
        if (composite_nomem(conn_req, c)) return c;

        composite_continue(c, conn_req, continue_smb_connect, c);
        return c;
}


/*
  Receive result of a rpc connection to a rpc pipe on SMB
*/
static NTSTATUS dcerpc_pipe_connect_ncacn_np_smb_recv(struct composite_context *c)
{
        NTSTATUS status = composite_wait(c);

        talloc_free(c);
        return status;
}


struct pipe_np_smb2_state {
        struct smb2_tree *tree;
        struct dcerpc_pipe_connect io;
};


/*
  Stage 3 of ncacn_np_smb: Named pipe opened (or not)
*/
static void continue_pipe_open_smb2(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);

        /* receive result of named pipe open request on smb2 */
        c->status = dcerpc_pipe_open_smb2_recv(ctx);
        if (!composite_is_ok(c)) return;

        composite_done(c);
}


/*
  Stage 2 of ncacn_np_smb2: Open a named pipe after successful smb2 connection
*/
static void continue_smb2_connect(struct composite_context *ctx)
{
        struct composite_context *open_req;
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_np_smb2_state *s = talloc_get_type(c->private_data,
                                                       struct pipe_np_smb2_state);

        /* receive result of smb2 connect request */
        c->status = smb2_connect_recv(ctx, c, &s->tree);
        if (!composite_is_ok(c)) return;

        /* prepare named pipe open parameters */
        s->io.pipe_name = s->io.binding->endpoint;

        /* send named pipe open request */
        open_req = dcerpc_pipe_open_smb2_send(s->io.pipe, s->tree, s->io.pipe_name);
        if (composite_nomem(open_req, c)) return;

        composite_continue(c, open_req, continue_pipe_open_smb2, c);
}


/* 
   Initiate async open of a rpc connection request on SMB2 using
   the binding structure to determine the endpoint and options
*/
static struct composite_context *dcerpc_pipe_connect_ncacn_np_smb2_send(
                                        TALLOC_CTX *mem_ctx,
                                        struct dcerpc_pipe_connect *io,
                                        struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        struct pipe_np_smb2_state *s;
        struct composite_context *conn_req;
        struct smbcli_options options;

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

        s = talloc_zero(c, struct pipe_np_smb2_state);
        if (composite_nomem(s, c)) return c;
        c->private_data = s;

        s->io = *io;

        /*
         * provide proper credentials - user supplied or anonymous in case this is
         * schannel connection
         */
        if (s->io.binding->flags & DCERPC_SCHANNEL) {
                s->io.creds = cli_credentials_init(mem_ctx);
                if (composite_nomem(s->io.creds, c)) return c;

                cli_credentials_guess(s->io.creds, lp_ctx);
        }

        lp_smbcli_options(lp_ctx, &options);

        /* send smb2 connect request */
        conn_req = smb2_connect_send(mem_ctx, s->io.binding->host, 
                        lp_parm_string_list(mem_ctx, lp_ctx, NULL, "smb2", "ports", NULL),
                                        "IPC$", 
                                     s->io.resolve_ctx,
                                     s->io.creds,
                                     c->event_ctx,
                                     &options,
                                         lp_socket_options(lp_ctx),
                                         lp_gensec_settings(mem_ctx, lp_ctx)
                                         );
        composite_continue(c, conn_req, continue_smb2_connect, c);
        return c;
}


/*
  Receive result of a rpc connection to a rpc pipe on SMB2
*/
static NTSTATUS dcerpc_pipe_connect_ncacn_np_smb2_recv(struct composite_context *c)
{
        NTSTATUS status = composite_wait(c);
        
        talloc_free(c);
        return status;
}


struct pipe_ip_tcp_state {
        struct dcerpc_pipe_connect io;
        const char *host;
        const char *target_hostname;
        uint32_t port;
};


/*
  Stage 2 of ncacn_ip_tcp: rpc pipe opened (or not)
*/
static void continue_pipe_open_ncacn_ip_tcp(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);

        /* receive result of named pipe open request on tcp/ip */
        c->status = dcerpc_pipe_open_tcp_recv(ctx);
        if (!composite_is_ok(c)) return;

        composite_done(c);
}


/*
  Initiate async open of a rpc connection to a rpc pipe on TCP/IP using
  the binding structure to determine the endpoint and options
*/
static struct composite_context* dcerpc_pipe_connect_ncacn_ip_tcp_send(TALLOC_CTX *mem_ctx,
                                                                       struct dcerpc_pipe_connect *io)
{
        struct composite_context *c;
        struct pipe_ip_tcp_state *s;
        struct composite_context *pipe_req;

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

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

        /* store input parameters in state structure */
        s->io               = *io;
        s->host             = talloc_reference(c, io->binding->host);
        s->target_hostname  = talloc_reference(c, io->binding->target_hostname);
                             /* port number is a binding endpoint here */
        s->port             = atoi(io->binding->endpoint);   

        /* send pipe open request on tcp/ip */
        pipe_req = dcerpc_pipe_open_tcp_send(s->io.pipe->conn, s->host, s->target_hostname, 
                                             s->port, io->resolve_ctx);
        composite_continue(c, pipe_req, continue_pipe_open_ncacn_ip_tcp, c);
        return c;
}


/*
  Receive result of a rpc connection to a rpc pipe on TCP/IP
*/
static NTSTATUS dcerpc_pipe_connect_ncacn_ip_tcp_recv(struct composite_context *c)
{
        NTSTATUS status = composite_wait(c);
        
        talloc_free(c);
        return status;
}


struct pipe_unix_state {
        struct dcerpc_pipe_connect io;
        const char *path;
};


/*
  Stage 2 of ncacn_unix: rpc pipe opened (or not)
*/
static void continue_pipe_open_ncacn_unix_stream(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);

        /* receive result of pipe open request on unix socket */
        c->status = dcerpc_pipe_open_unix_stream_recv(ctx);
        if (!composite_is_ok(c)) return;

        composite_done(c);
}


/*
  Initiate async open of a rpc connection to a rpc pipe on unix socket using
  the binding structure to determine the endpoint and options
*/
static struct composite_context* dcerpc_pipe_connect_ncacn_unix_stream_send(TALLOC_CTX *mem_ctx,
                                                                            struct dcerpc_pipe_connect *io)
{
        struct composite_context *c;
        struct pipe_unix_state *s;
        struct composite_context *pipe_req;

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

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

        /* prepare pipe open parameters and store them in state structure
           also, verify whether biding endpoint is not null */
        s->io = *io;
        
        if (!io->binding->endpoint) {
                DEBUG(0, ("Path to unix socket not specified\n"));
                composite_error(c, NT_STATUS_INVALID_PARAMETER);
                return c;
        }

        s->path  = talloc_strdup(c, io->binding->endpoint);  /* path is a binding endpoint here */
        if (composite_nomem(s->path, c)) return c;

        /* send pipe open request on unix socket */
        pipe_req = dcerpc_pipe_open_unix_stream_send(s->io.pipe->conn, s->path);
        composite_continue(c, pipe_req, continue_pipe_open_ncacn_unix_stream, c);
        return c;
}


/*
  Receive result of a rpc connection to a pipe on unix socket
*/
static NTSTATUS dcerpc_pipe_connect_ncacn_unix_stream_recv(struct composite_context *c)
{
        NTSTATUS status = composite_wait(c);

        talloc_free(c);
        return status;
}


struct pipe_ncalrpc_state {
        struct dcerpc_pipe_connect io;
};

static NTSTATUS dcerpc_pipe_connect_ncalrpc_recv(struct composite_context *c);

/*
  Stage 2 of ncalrpc: rpc pipe opened (or not)
*/
static void continue_pipe_open_ncalrpc(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);

        /* receive result of pipe open request on ncalrpc */
        c->status = dcerpc_pipe_connect_ncalrpc_recv(ctx);
        if (!composite_is_ok(c)) return;

        composite_done(c);
}


/* 
   Initiate async open of a rpc connection request on NCALRPC using
   the binding structure to determine the endpoint and options
*/
static struct composite_context* dcerpc_pipe_connect_ncalrpc_send(TALLOC_CTX *mem_ctx,
                                                                  struct dcerpc_pipe_connect *io, struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        struct pipe_ncalrpc_state *s;
        struct composite_context *pipe_req;

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

        s = talloc_zero(c, struct pipe_ncalrpc_state);
        if (composite_nomem(s, c)) return c;
        c->private_data = s;
        
        /* store input parameters in state structure */
        s->io  = *io;

        /* send pipe open request */
        pipe_req = dcerpc_pipe_open_pipe_send(s->io.pipe->conn, lp_ncalrpc_dir(lp_ctx), 
                                              s->io.binding->endpoint);
        composite_continue(c, pipe_req, continue_pipe_open_ncalrpc, c);
        return c;
}


/*
  Receive result of a rpc connection to a rpc pipe on NCALRPC
*/
static NTSTATUS dcerpc_pipe_connect_ncalrpc_recv(struct composite_context *c)
{
        NTSTATUS status = composite_wait(c);
        
        talloc_free(c);
        return status;
}


struct pipe_connect_state {
        struct dcerpc_pipe *pipe;
        struct dcerpc_binding *binding;
        const struct ndr_interface_table *table;
        struct cli_credentials *credentials;
        struct loadparm_context *lp_ctx;
};


static void continue_map_binding(struct composite_context *ctx);
static void continue_connect(struct composite_context *c, struct pipe_connect_state *s);
static void continue_pipe_connect_ncacn_np_smb2(struct composite_context *ctx);
static void continue_pipe_connect_ncacn_np_smb(struct composite_context *ctx);
static void continue_pipe_connect_ncacn_ip_tcp(struct composite_context *ctx);
static void continue_pipe_connect_ncacn_unix(struct composite_context *ctx);
static void continue_pipe_connect_ncalrpc(struct composite_context *ctx);
static void continue_pipe_connect(struct composite_context *c, struct pipe_connect_state *s);
static void continue_pipe_auth(struct composite_context *ctx);


/*
  Stage 2 of pipe_connect_b: Receive result of endpoint mapping
*/
static void continue_map_binding(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_connect_state *s = talloc_get_type(c->private_data,
                                                       struct pipe_connect_state);
        
        c->status = dcerpc_epm_map_binding_recv(ctx);
        if (!composite_is_ok(c)) return;

        DEBUG(2,("Mapped to DCERPC endpoint %s\n", s->binding->endpoint));
        
        continue_connect(c, s);
}


/*
  Stage 2 of pipe_connect_b: Continue connection after endpoint is known
*/
static void continue_connect(struct composite_context *c, struct pipe_connect_state *s)
{
        struct dcerpc_pipe_connect pc;

        /* potential exits to another stage by sending an async request */
        struct composite_context *ncacn_np_smb2_req;
        struct composite_context *ncacn_np_smb_req;
        struct composite_context *ncacn_ip_tcp_req;
        struct composite_context *ncacn_unix_req;
        struct composite_context *ncalrpc_req;

        /* dcerpc pipe connect input parameters */
        pc.pipe         = s->pipe;
        pc.binding      = s->binding;
        pc.interface    = s->table;
        pc.creds        = s->credentials;
        pc.resolve_ctx  = lp_resolve_context(s->lp_ctx);

        /* connect dcerpc pipe depending on required transport */
        switch (s->binding->transport) {
        case NCACN_NP:
                if (pc.binding->flags & DCERPC_SMB2) {
                        /* new varient of SMB a.k.a. SMB2 */
                        ncacn_np_smb2_req = dcerpc_pipe_connect_ncacn_np_smb2_send(c, &pc, s->lp_ctx);
                        composite_continue(c, ncacn_np_smb2_req, continue_pipe_connect_ncacn_np_smb2, c);
                        return;

                } else {
                        /* good old ordinary SMB */
                        ncacn_np_smb_req = dcerpc_pipe_connect_ncacn_np_smb_send(c, &pc, s->lp_ctx);
                        composite_continue(c, ncacn_np_smb_req, continue_pipe_connect_ncacn_np_smb, c);
                        return;
                }
                break;

        case NCACN_IP_TCP:
                ncacn_ip_tcp_req = dcerpc_pipe_connect_ncacn_ip_tcp_send(c, &pc);
                composite_continue(c, ncacn_ip_tcp_req, continue_pipe_connect_ncacn_ip_tcp, c);
                return;

        case NCACN_UNIX_STREAM:
                ncacn_unix_req = dcerpc_pipe_connect_ncacn_unix_stream_send(c, &pc);
                composite_continue(c, ncacn_unix_req, continue_pipe_connect_ncacn_unix, c);
                return;

        case NCALRPC:
                ncalrpc_req = dcerpc_pipe_connect_ncalrpc_send(c, &pc, s->lp_ctx);
                composite_continue(c, ncalrpc_req, continue_pipe_connect_ncalrpc, c);
                return;

        default:
                /* looks like a transport we don't support now */
                composite_error(c, NT_STATUS_NOT_SUPPORTED);
        }
}


/*
  Stage 3 of pipe_connect_b: Receive result of pipe connect request on
  named pipe on smb2
*/
static void continue_pipe_connect_ncacn_np_smb2(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_connect_state *s = talloc_get_type(c->private_data,
                                                       struct pipe_connect_state);

        c->status = dcerpc_pipe_connect_ncacn_np_smb2_recv(ctx);
        if (!composite_is_ok(c)) return;

        continue_pipe_connect(c, s);
}


/*
  Stage 3 of pipe_connect_b: Receive result of pipe connect request on
  named pipe on smb
*/
static void continue_pipe_connect_ncacn_np_smb(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_connect_state *s = talloc_get_type(c->private_data,
                                                       struct pipe_connect_state);

        c->status = dcerpc_pipe_connect_ncacn_np_smb_recv(ctx);
        if (!composite_is_ok(c)) return;
        
        continue_pipe_connect(c, s);
}


/*
  Stage 3 of pipe_connect_b: Receive result of pipe connect request on tcp/ip
*/
static void continue_pipe_connect_ncacn_ip_tcp(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_connect_state *s = talloc_get_type(c->private_data,
                                                       struct pipe_connect_state);

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

        continue_pipe_connect(c, s);
}


/*
  Stage 3 of pipe_connect_b: Receive result of pipe connect request on unix socket
*/
static void continue_pipe_connect_ncacn_unix(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_connect_state *s = talloc_get_type(c->private_data,
                                                       struct pipe_connect_state);
        
        c->status = dcerpc_pipe_connect_ncacn_unix_stream_recv(ctx);
        if (!composite_is_ok(c)) return;
        
        continue_pipe_connect(c, s);
}


/*
  Stage 3 of pipe_connect_b: Receive result of pipe connect request on local rpc
*/
static void continue_pipe_connect_ncalrpc(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_connect_state *s = talloc_get_type(c->private_data,
                                                       struct pipe_connect_state);
        
        c->status = dcerpc_pipe_connect_ncalrpc_recv(ctx);
        if (!composite_is_ok(c)) return;

        continue_pipe_connect(c, s);
}


/*
  Stage 4 of pipe_connect_b: Start an authentication on connected dcerpc pipe
  depending on credentials and binding flags passed.
*/
static void continue_pipe_connect(struct composite_context *c, struct pipe_connect_state *s)
{
        struct composite_context *auth_bind_req;

        s->pipe->binding = s->binding;
        if (!talloc_reference(s->pipe, s->binding)) {
                composite_error(c, NT_STATUS_NO_MEMORY);
                return;
        }

        auth_bind_req = dcerpc_pipe_auth_send(s->pipe, s->binding, s->table,
                                              s->credentials, s->lp_ctx);
        composite_continue(c, auth_bind_req, continue_pipe_auth, c);
}


/*
  Stage 5 of pipe_connect_b: Receive result of pipe authentication request
  and say if all went ok
*/
static void continue_pipe_auth(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_connect_state *s = talloc_get_type(c->private_data, struct pipe_connect_state);

        c->status = dcerpc_pipe_auth_recv(ctx, s, &s->pipe);
        if (!composite_is_ok(c)) return;

        composite_done(c);
}


/*
  handle timeouts of a dcerpc connect
*/
static void dcerpc_connect_timeout_handler(struct tevent_context *ev, struct tevent_timer *te, 
                                           struct timeval t, void *private_data)
{
        struct composite_context *c = talloc_get_type(private_data, struct composite_context);
        composite_error(c, NT_STATUS_IO_TIMEOUT);
}

/*
  start a request to open a rpc connection to a rpc pipe, using
  specified binding structure to determine the endpoint and options
*/
_PUBLIC_ struct composite_context* dcerpc_pipe_connect_b_send(TALLOC_CTX *parent_ctx,
                                                     struct dcerpc_binding *binding,
                                                     const struct ndr_interface_table *table,
                                                     struct cli_credentials *credentials,
                                                     struct tevent_context *ev,
                                                     struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        struct pipe_connect_state *s;
        struct tevent_context *new_ev = NULL;

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

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

        /* initialise dcerpc pipe structure */
        s->pipe = dcerpc_pipe_init(c, ev, lp_iconv_convenience(lp_ctx));
        if (composite_nomem(s->pipe, c)) return c;

        if (DEBUGLEVEL >= 10)
                s->pipe->conn->packet_log_dir = lp_lockdir(lp_ctx);

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

        event_add_timed(c->event_ctx, c,
                        timeval_current_ofs(DCERPC_REQUEST_TIMEOUT, 0),
                        dcerpc_connect_timeout_handler, c);
        
        switch (s->binding->transport) {
        case NCA_UNKNOWN: {
                struct composite_context *binding_req;
                binding_req = dcerpc_epm_map_binding_send(c, s->binding, s->table,
                                                          s->pipe->conn->event_ctx,
                                                          s->lp_ctx);
                composite_continue(c, binding_req, continue_map_binding, c);
                return c;
                }

        case NCACN_NP:
        case NCACN_IP_TCP:
        case NCALRPC:
                if (!s->binding->endpoint) {
                        struct composite_context *binding_req;
                        binding_req = dcerpc_epm_map_binding_send(c, s->binding, s->table,
                                                                  s->pipe->conn->event_ctx,
                                                                  s->lp_ctx);
                        composite_continue(c, binding_req, continue_map_binding, c);
                        return c;
                }

        default:
                break;
        }

        continue_connect(c, s);
        return c;
}


/*
  receive result of a request to open a rpc connection to a rpc pipe
*/
_PUBLIC_ NTSTATUS dcerpc_pipe_connect_b_recv(struct composite_context *c, TALLOC_CTX *mem_ctx,
                                    struct dcerpc_pipe **p)
{
        NTSTATUS status;
        struct pipe_connect_state *s;
        
        status = composite_wait(c);
        
        if (NT_STATUS_IS_OK(status)) {
                s = talloc_get_type(c->private_data, struct pipe_connect_state);
                talloc_steal(mem_ctx, s->pipe);
                *p = s->pipe;
        }
        talloc_free(c);
        return status;
}


/*
  open a rpc connection to a rpc pipe, using the specified 
  binding structure to determine the endpoint and options - sync version
*/
_PUBLIC_ NTSTATUS dcerpc_pipe_connect_b(TALLOC_CTX *parent_ctx,
                               struct dcerpc_pipe **pp,
                               struct dcerpc_binding *binding,
                               const struct ndr_interface_table *table,
                               struct cli_credentials *credentials,
                               struct tevent_context *ev,
                               struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        
        c = dcerpc_pipe_connect_b_send(parent_ctx, binding, table,
                                       credentials, ev, lp_ctx);
        return dcerpc_pipe_connect_b_recv(c, parent_ctx, pp);
}


struct pipe_conn_state {
        struct dcerpc_pipe *pipe;
};


static void continue_pipe_connect_b(struct composite_context *ctx);


/*
  Initiate rpc connection to a rpc pipe, using the specified string
  binding to determine the endpoint and options.
  The string is to be parsed to a binding structure first.
*/
_PUBLIC_ struct composite_context* dcerpc_pipe_connect_send(TALLOC_CTX *parent_ctx,
                                                   const char *binding,
                                                   const struct ndr_interface_table *table,
                                                   struct cli_credentials *credentials,
                                                   struct tevent_context *ev, struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        struct pipe_conn_state *s;
        struct dcerpc_binding *b;
        struct composite_context *pipe_conn_req;

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

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

        /* parse binding string to the structure */
        c->status = dcerpc_parse_binding(c, binding, &b);
        if (!NT_STATUS_IS_OK(c->status)) {
                DEBUG(0, ("Failed to parse dcerpc binding '%s'\n", binding));
                composite_error(c, c->status);
                return c;
        }

        DEBUG(3, ("Using binding %s\n", dcerpc_binding_string(c, b)));

        /* 
           start connecting to a rpc pipe after binding structure
           is established
         */
        pipe_conn_req = dcerpc_pipe_connect_b_send(c, b, table,
                                                   credentials, ev, lp_ctx);
        composite_continue(c, pipe_conn_req, continue_pipe_connect_b, c);
        return c;
}


/*
  Stage 2 of pipe_connect: Receive result of actual pipe connect request
  and say if we're done ok
*/
static void continue_pipe_connect_b(struct composite_context *ctx)
{
        struct composite_context *c = talloc_get_type(ctx->async.private_data,
                                                      struct composite_context);
        struct pipe_conn_state *s = talloc_get_type(c->private_data,
                                                    struct pipe_conn_state);

        c->status = dcerpc_pipe_connect_b_recv(ctx, c, &s->pipe);
        talloc_steal(s, s->pipe);
        if (!composite_is_ok(c)) return;

        composite_done(c);
}


/*
  Receive result of pipe connect (using binding string) request
  and return connected pipe structure.
*/
NTSTATUS dcerpc_pipe_connect_recv(struct composite_context *c,
                                  TALLOC_CTX *mem_ctx,
                                  struct dcerpc_pipe **pp)
{
        NTSTATUS status;
        struct pipe_conn_state *s;

        status = composite_wait(c);
        if (NT_STATUS_IS_OK(status)) {
                s = talloc_get_type(c->private_data, struct pipe_conn_state);
                *pp = talloc_steal(mem_ctx, s->pipe);
        }
        talloc_free(c);
        return status;
}


/*
  Open a rpc connection to a rpc pipe, using the specified string
  binding to determine the endpoint and options - sync version
*/
_PUBLIC_ NTSTATUS dcerpc_pipe_connect(TALLOC_CTX *parent_ctx, 
                             struct dcerpc_pipe **pp, 
                             const char *binding,
                             const struct ndr_interface_table *table,
                             struct cli_credentials *credentials,
                             struct tevent_context *ev,
                             struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        c = dcerpc_pipe_connect_send(parent_ctx, binding, 
                                     table, credentials, ev, lp_ctx);
        return dcerpc_pipe_connect_recv(c, parent_ctx, pp);
}