source: branches/samba-3.5.x/source4/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 "param/param.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;
}

/* 
   push a ncacn_packet into a blob, potentially with auth info
*/
NTSTATUS ncacn_push_auth(DATA_BLOB *blob, TALLOC_CTX *mem_ctx, 
                         struct smb_iconv_convenience *iconv_convenience,
                          struct ncacn_packet *pkt,
                          struct dcerpc_auth *auth_info)
{
        struct ndr_push *ndr;
        enum ndr_err_code ndr_err;

        ndr = ndr_push_init_ctx(mem_ctx, iconv_convenience);
        if (!ndr) {
                return NT_STATUS_NO_MEMORY;
        }

        if (!(pkt->drep[0] & DCERPC_DREP_LE)) {
                ndr->flags |= LIBNDR_FLAG_BIGENDIAN;
        }

        if (pkt->pfc_flags & DCERPC_PFC_FLAG_OBJECT_UUID) {
                ndr->flags |= LIBNDR_FLAG_OBJECT_PRESENT;
        }

        if (auth_info) {
                pkt->auth_length = auth_info->credentials.length;
        } else {
                pkt->auth_length = 0;
        }

        ndr_err = ndr_push_ncacn_packet(ndr, NDR_SCALARS|NDR_BUFFERS, pkt);
        if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                return ndr_map_error2ntstatus(ndr_err);
        }

        if (auth_info) {
                ndr_err = ndr_push_dcerpc_auth(ndr, NDR_SCALARS|NDR_BUFFERS, auth_info);
                if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                        return ndr_map_error2ntstatus(ndr_err);
                }
        }

        *blob = ndr_push_blob(ndr);

        /* fill in the frag length */
        dcerpc_set_frag_length(blob, blob->length);

        return NT_STATUS_OK;
}


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 guid;
        struct epm_twr_t twr;
        struct epm_twr_t *twr_r;
        struct epm_Map r;
};


static void continue_epm_recv_binding(struct composite_context *ctx);
static void continue_epm_map(struct rpc_request *req);


/*
  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 rpc_request *map_req;

        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);

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

        s->pipe->conn->flags |= DCERPC_NDR_REF_ALLOC;

        /* prepare requested binding parameters */
        s->binding->object         = s->table->syntax_id;

        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->guid;
        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;

        /* send request for an endpoint mapping - a rpc request on connected pipe */
        map_req = dcerpc_epm_Map_send(s->pipe, c, &s->r);
        if (composite_nomem(map_req, c)) return;
        
        composite_continue_rpc(c, map_req, continue_epm_map, c);
}


/*
  Stage 3 of epm_map_binding: Receive endpoint mapping and provide binding details
*/
static void continue_epm_map(struct rpc_request *req)
{
        struct composite_context *c = talloc_get_type(req->async.private_data,
                                                      struct composite_context);
        struct epm_map_binding_state *s = talloc_get_type(c->private_data,
                                                          struct epm_map_binding_state);

        /* receive result of a rpc request */
        c->status = dcerpc_ndr_request_recv(req);
        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 */
        s->binding->endpoint = talloc_reference(s->binding,
                                                dcerpc_floor_get_rhs_data(c, &s->twr_r->tower.floors[3]));
        if (composite_nomem(s->binding->endpoint, 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 tevent_context *ev,
                                                      struct loadparm_context *lp_ctx)
{
        struct composite_context *c;
        struct epm_map_binding_state *s;
        struct composite_context *pipe_connect_req;
        struct cli_credentials *anon_creds;

        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->table   = table;

        /* anonymous credentials for rpc connection used to get endpoint mapping */
        anon_creds = cli_credentials_init(mem_ctx);
        cli_credentials_set_anonymous(anon_creds);

        /*
          First, check if there is a default endpoint specified in the IDL
        */
        if (table != NULL) {
                struct dcerpc_binding *default_binding;

                /* Find one of the default pipes for this interface */
                for (i = 0; i < table->endpoints->count; i++) {
                        status = dcerpc_parse_binding(mem_ctx, table->endpoints->names[i], &default_binding);

                        if (NT_STATUS_IS_OK(status)) {
                                if (binding->transport == NCA_UNKNOWN) 
                                        binding->transport = default_binding->transport;
                                if (default_binding->transport == binding->transport && 
                                        default_binding->endpoint) {
                                        binding->endpoint = talloc_reference(binding, default_binding->endpoint);
                                        talloc_free(default_binding);

                                        composite_done(c);
                                        return c;

                                } else {
                                        talloc_free(default_binding);
                                }
                        }
                }
        }

        epmapper_binding = talloc_zero(c, struct dcerpc_binding);
        if (composite_nomem(epmapper_binding, c)) return c;

        /* basic endpoint mapping data */
        epmapper_binding->transport             = binding->transport;
        epmapper_binding->host                  = talloc_reference(epmapper_binding, binding->host);
        epmapper_binding->target_hostname       = epmapper_binding->host;
        epmapper_binding->options               = NULL;
        epmapper_binding->flags                 = 0;
        epmapper_binding->assoc_group_id        = 0;
        epmapper_binding->endpoint              = NULL;

        /* initiate rpc pipe connection */
        pipe_connect_req = dcerpc_pipe_connect_b_send(c, epmapper_binding, 
                                                      &ndr_table_epmapper,
                                                      anon_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;

        c = dcerpc_epm_map_binding_send(mem_ctx, binding, table, ev, lp_ctx);
        return dcerpc_epm_map_binding_recv(c);
}


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


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)) {
                if (cli_credentials_wrong_password(s->credentials)) {
                        /*
                         * 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;

        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, 
                                         lp_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, 
                                         lp_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, 
                                                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 dcerpc_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 = binding->flags;

        if (DEBUGLVL(100)) {
                conn->flags |= DCERPC_DEBUG_PRINT_BOTH;
        }
        
        /* remember the binding string for possible secondary connections */
        conn->binding_string = dcerpc_binding_string(p, binding);

        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 ((binding->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 &&
            !(s->binding->flags & (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_SIGN|DCERPC_SEAL))) {
                /*
                  we are doing an authenticated connection,
                  but not using sign or seal. We must force
                  the CONNECT dcerpc auth type as a NONE auth
                  type doesn't allow authentication
                  information to be passed.
                */
                conn->flags |= DCERPC_CONNECT;
        }

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

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

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

        } else if (s->binding->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, 
                                                 lp_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, 
                                         lp_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 - %s\n", uuid_str, 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, 
                          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 dcerpc_generic_session_key(struct dcerpc_connection *c,
                                    DATA_BLOB *session_key)
{
        /* this took quite a few CPU cycles to find ... */
        session_key->data = discard_const_p(unsigned char, "SystemLibraryDTC");
        session_key->length = 16;
        return NT_STATUS_OK;
}

/*
  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;
}


/*
  log a rpc packet in a format suitable for ndrdump. This is especially useful
  for sealed packets, where ethereal cannot easily see the contents

  this triggers on a debug level of >= 10
*/
_PUBLIC_ void dcerpc_log_packet(const char *lockdir,
                                                                const struct ndr_interface_table *ndr,
                       uint32_t opnum, uint32_t flags, 
                       DATA_BLOB *pkt)
{
        const int num_examples = 20;
        int i;

        if (lockdir == NULL) return;

        for (i=0;i<num_examples;i++) {
                char *name=NULL;
                asprintf(&name, "%s/rpclog/%s-%u.%d.%s", 
                         lockdir, ndr->name, opnum, i,
                         (flags&NDR_IN)?"in":"out");
                if (name == NULL) {
                        return;
                }
                if (!file_exist(name)) {
                        if (file_save(name, pkt->data, pkt->length)) {
                                DEBUG(10,("Logged rpc packet to %s\n", name));
                        }
                        free(name);
                        break;
                }
                free(name);
        }
}



/*
  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;
        
        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 = talloc_reference(p2, p->binding);

        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;
}