Never hand out 0xffff as a mid

[Samba/gebeck_regimport.git] / source3 / libsmb / async_smb.c

/*
   Unix SMB/CIFS implementation.
   Infrastructure for async SMB client requests
   Copyright (C) Volker Lendecke 2008

   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"

/**
 * Fetch an error out of a NBT packet
 * @param[in] buf       The SMB packet
 * @retval              The error, converted to NTSTATUS
 */

NTSTATUS cli_pull_error(char *buf)
{
        uint32_t flags2 = SVAL(buf, smb_flg2);

        if (flags2 & FLAGS2_32_BIT_ERROR_CODES) {
                return NT_STATUS(IVAL(buf, smb_rcls));
        }

        /* if the client uses dos errors, but there is no error,
           we should return no error here, otherwise it looks
           like an unknown bad NT_STATUS. jmcd */
        if (CVAL(buf, smb_rcls) == 0)
                return NT_STATUS_OK;

        return NT_STATUS_DOS(CVAL(buf, smb_rcls), SVAL(buf,smb_err));
}

/**
 * Compatibility helper for the sync APIs: Fake NTSTATUS in cli->inbuf
 * @param[in] cli       The client connection that just received an error
 * @param[in] status    The error to set on "cli"
 */

void cli_set_error(struct cli_state *cli, NTSTATUS status)
{
        uint32_t flags2 = SVAL(cli->inbuf, smb_flg2);

        if (NT_STATUS_IS_DOS(status)) {
                SSVAL(cli->inbuf, smb_flg2,
                      flags2 & ~FLAGS2_32_BIT_ERROR_CODES);
                SCVAL(cli->inbuf, smb_rcls, NT_STATUS_DOS_CLASS(status));
                SSVAL(cli->inbuf, smb_err, NT_STATUS_DOS_CODE(status));
                return;
        }

        SSVAL(cli->inbuf, smb_flg2, flags2 | FLAGS2_32_BIT_ERROR_CODES);
        SIVAL(cli->inbuf, smb_rcls, NT_STATUS_V(status));
        return;
}

/**
 * @brief Find the smb_cmd offset of the last command pushed
 * @param[in] buf       The buffer we're building up
 * @retval              Where can we put our next andx cmd?
 *
 * While chaining requests, the "next" request we're looking at needs to put
 * its SMB_Command before the data the previous request already built up added
 * to the chain. Find the offset to the place where we have to put our cmd.
 */

static bool find_andx_cmd_ofs(uint8_t *buf, size_t *pofs)
{
        uint8_t cmd;
        size_t ofs;

        cmd = CVAL(buf, smb_com);

        SMB_ASSERT(is_andx_req(cmd));

        ofs = smb_vwv0;

        while (CVAL(buf, ofs) != 0xff) {

                if (!is_andx_req(CVAL(buf, ofs))) {
                        return false;
                }

                /*
                 * ofs is from start of smb header, so add the 4 length
                 * bytes. The next cmd is right after the wct field.
                 */
                ofs = SVAL(buf, ofs+2) + 4 + 1;

                SMB_ASSERT(ofs+4 < talloc_get_size(buf));
        }

        *pofs = ofs;
        return true;
}

/**
 * @brief Do the smb chaining at a buffer level
 * @param[in] poutbuf           Pointer to the talloc'ed buffer to be modified
 * @param[in] smb_command       The command that we want to issue
 * @param[in] wct               How many words?
 * @param[in] vwv               The words, already in network order
 * @param[in] bytes_alignment   How shall we align "bytes"?
 * @param[in] num_bytes         How many bytes?
 * @param[in] bytes             The data the request ships
 *
 * smb_splice_chain() adds the vwv and bytes to the request already present in
 * *poutbuf.
 */

bool smb_splice_chain(uint8_t **poutbuf, uint8_t smb_command,
                      uint8_t wct, const uint16_t *vwv,
                      size_t bytes_alignment,
                      uint32_t num_bytes, const uint8_t *bytes)
{
        uint8_t *outbuf;
        size_t old_size, new_size;
        size_t ofs;
        size_t chain_padding = 0;
        size_t bytes_padding = 0;
        bool first_request;

        old_size = talloc_get_size(*poutbuf);

        /*
         * old_size == smb_wct means we're pushing the first request in for
         * libsmb/
         */

        first_request = (old_size == smb_wct);

        if (!first_request && ((old_size % 4) != 0)) {
                /*
                 * Align the wct field of subsequent requests to a 4-byte
                 * boundary
                 */
                chain_padding = 4 - (old_size % 4);
        }

        /*
         * After the old request comes the new wct field (1 byte), the vwv's
         * and the num_bytes field. After at we might need to align the bytes
         * given to us to "bytes_alignment", increasing the num_bytes value.
         */

        new_size = old_size + chain_padding + 1 + wct * sizeof(uint16_t) + 2;

        if ((bytes_alignment != 0) && ((new_size % bytes_alignment) != 0)) {
                bytes_padding = bytes_alignment - (new_size % bytes_alignment);
        }

        new_size += bytes_padding + num_bytes;

        if ((smb_command != SMBwriteX) && (new_size > 0xffff)) {
                DEBUG(1, ("splice_chain: %u bytes won't fit\n",
                          (unsigned)new_size));
                return false;
        }

        outbuf = TALLOC_REALLOC_ARRAY(NULL, *poutbuf, uint8_t, new_size);
        if (outbuf == NULL) {
                DEBUG(0, ("talloc failed\n"));
                return false;
        }
        *poutbuf = outbuf;

        if (first_request) {
                SCVAL(outbuf, smb_com, smb_command);
        } else {
                size_t andx_cmd_ofs;

                if (!find_andx_cmd_ofs(outbuf, &andx_cmd_ofs)) {
                        DEBUG(1, ("invalid command chain\n"));
                        *poutbuf = TALLOC_REALLOC_ARRAY(
                                NULL, *poutbuf, uint8_t, old_size);
                        return false;
                }

                if (chain_padding != 0) {
                        memset(outbuf + old_size, 0, chain_padding);
                        old_size += chain_padding;
                }

                SCVAL(outbuf, andx_cmd_ofs, smb_command);
                SSVAL(outbuf, andx_cmd_ofs + 2, old_size - 4);
        }

        ofs = old_size;

        /*
         * Push the chained request:
         *
         * wct field
         */

        SCVAL(outbuf, ofs, wct);
        ofs += 1;

        /*
         * vwv array
         */

        memcpy(outbuf + ofs, vwv, sizeof(uint16_t) * wct);
        ofs += sizeof(uint16_t) * wct;

        /*
         * bcc (byte count)
         */

        SSVAL(outbuf, ofs, num_bytes + bytes_padding);
        ofs += sizeof(uint16_t);

        /*
         * padding
         */

        if (bytes_padding != 0) {
                memset(outbuf + ofs, 0, bytes_padding);
                ofs += bytes_padding;
        }

        /*
         * The bytes field
         */

        memcpy(outbuf + ofs, bytes, num_bytes);

        return true;
}

/**
 * Figure out if there is an andx command behind the current one
 * @param[in] buf       The smb buffer to look at
 * @param[in] ofs       The offset to the wct field that is followed by the cmd
 * @retval Is there a command following?
 */

static bool have_andx_command(const char *buf, uint16_t ofs)
{
        uint8_t wct;
        size_t buflen = talloc_get_size(buf);

        if ((ofs == buflen-1) || (ofs == buflen)) {
                return false;
        }

        wct = CVAL(buf, ofs);
        if (wct < 2) {
                /*
                 * Not enough space for the command and a following pointer
                 */
                return false;
        }
        return (CVAL(buf, ofs+1) != 0xff);
}

#define MAX_SMB_IOV 5

struct cli_smb_state {
        struct tevent_context *ev;
        struct cli_state *cli;
        uint8_t header[smb_wct+1]; /* Space for the header including the wct */

        /*
         * For normal requests, cli_smb_req_send chooses a mid. Secondary
         * trans requests need to use the mid of the primary request, so we
         * need a place to store it. Assume it's set if != 0.
         */
        uint16_t mid;

        uint16_t *vwv;
        uint8_t bytecount_buf[2];

        struct iovec iov[MAX_SMB_IOV+3];
        int iov_count;

        uint8_t *inbuf;
        uint32_t seqnum;
        int chain_num;
        struct tevent_req **chained_requests;
};

static uint16_t cli_alloc_mid(struct cli_state *cli)
{
        int num_pending = talloc_array_length(cli->pending);
        uint16_t result;

        while (true) {
                int i;

                result = cli->mid++;
                if ((result == 0) || (result == 0xffff)) {
                        continue;
                }

                for (i=0; i<num_pending; i++) {
                        if (result == cli_smb_req_mid(cli->pending[i])) {
                                break;
                        }
                }

                if (i == num_pending) {
                        return result;
                }
        }
}

void cli_smb_req_unset_pending(struct tevent_req *req)
{
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);
        struct cli_state *cli = state->cli;
        int num_pending = talloc_array_length(cli->pending);
        int i;

        if (num_pending == 1) {
                /*
                 * The pending read_smb tevent_req is a child of
                 * cli->pending. So if nothing is pending anymore, we need to
                 * delete the socket read fde.
                 */
                TALLOC_FREE(cli->pending);
                return;
        }

        for (i=0; i<num_pending; i++) {
                if (req == cli->pending[i]) {
                        break;
                }
        }
        if (i == num_pending) {
                /*
                 * Something's seriously broken. Just returning here is the
                 * right thing nevertheless, the point of this routine is to
                 * remove ourselves from cli->pending.
                 */
                return;
        }

        /*
         * Remove ourselves from the cli->pending array
         */
        if (num_pending > 1) {
                cli->pending[i] = cli->pending[num_pending-1];
        }

        /*
         * No NULL check here, we're shrinking by sizeof(void *), and
         * talloc_realloc just adjusts the size for this.
         */
        cli->pending = talloc_realloc(NULL, cli->pending, struct tevent_req *,
                                      num_pending - 1);
        return;
}

static int cli_smb_req_destructor(struct tevent_req *req)
{
        cli_smb_req_unset_pending(req);
        return 0;
}

static void cli_smb_received(struct tevent_req *subreq);

bool cli_smb_req_set_pending(struct tevent_req *req)
{
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);
        struct cli_state *cli;
        struct tevent_req **pending;
        int num_pending;
        struct tevent_req *subreq;

        cli = state->cli;
        num_pending = talloc_array_length(cli->pending);

        pending = talloc_realloc(cli, cli->pending, struct tevent_req *,
                                 num_pending+1);
        if (pending == NULL) {
                return false;
        }
        pending[num_pending] = req;
        cli->pending = pending;
        talloc_set_destructor(req, cli_smb_req_destructor);

        if (num_pending > 0) {
                return true;
        }

        /*
         * We're the first ones, add the read_smb request that waits for the
         * answer from the server
         */
        subreq = read_smb_send(cli->pending, state->ev, cli->fd);
        if (subreq == NULL) {
                cli_smb_req_unset_pending(req);
                return false;
        }
        tevent_req_set_callback(subreq, cli_smb_received, cli);
        return true;
}

/*
 * Fetch a smb request's mid. Only valid after the request has been sent by
 * cli_smb_req_send().
 */
uint16_t cli_smb_req_mid(struct tevent_req *req)
{
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);
        return SVAL(state->header, smb_mid);
}

void cli_smb_req_set_mid(struct tevent_req *req, uint16_t mid)
{
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);
        state->mid = mid;
}

static size_t iov_len(const struct iovec *iov, int count)
{
        size_t result = 0;
        int i;
        for (i=0; i<count; i++) {
                result += iov[i].iov_len;
        }
        return result;
}

static uint8_t *iov_concat(TALLOC_CTX *mem_ctx, const struct iovec *iov,
                           int count)
{
        size_t len = iov_len(iov, count);
        size_t copied;
        uint8_t *buf;
        int i;

        buf = talloc_array(mem_ctx, uint8_t, len);
        if (buf == NULL) {
                return NULL;
        }
        copied = 0;
        for (i=0; i<count; i++) {
                memcpy(buf+copied, iov[i].iov_base, iov[i].iov_len);
                copied += iov[i].iov_len;
        }
        return buf;
}

struct tevent_req *cli_smb_req_create(TALLOC_CTX *mem_ctx,
                                      struct event_context *ev,
                                      struct cli_state *cli,
                                      uint8_t smb_command,
                                      uint8_t additional_flags,
                                      uint8_t wct, uint16_t *vwv,
                                      int iov_count,
                                      struct iovec *bytes_iov)
{
        struct tevent_req *result;
        struct cli_smb_state *state;

        if (iov_count > MAX_SMB_IOV) {
                /*
                 * Should not happen :-)
                 */
                return NULL;
        }

        result = tevent_req_create(mem_ctx, &state, struct cli_smb_state);
        if (result == NULL) {
                return NULL;
        }
        state->ev = ev;
        state->cli = cli;
        state->mid = 0;         /* Set to auto-choose in cli_smb_req_send */
        state->chain_num = 0;
        state->chained_requests = NULL;

        cli_setup_packet_buf(cli, (char *)state->header);
        SCVAL(state->header, smb_com, smb_command);
        SSVAL(state->header, smb_tid, cli->cnum);
        SCVAL(state->header, smb_wct, wct);

        state->vwv = vwv;

        SSVAL(state->bytecount_buf, 0, iov_len(bytes_iov, iov_count));

        state->iov[0].iov_base = state->header;
        state->iov[0].iov_len  = sizeof(state->header);
        state->iov[1].iov_base = state->vwv;
        state->iov[1].iov_len  = wct * sizeof(uint16_t);
        state->iov[2].iov_base = state->bytecount_buf;
        state->iov[2].iov_len  = sizeof(uint16_t);

        if (iov_count != 0) {
                memcpy(&state->iov[3], bytes_iov,
                       iov_count * sizeof(*bytes_iov));
        }
        state->iov_count = iov_count + 3;

        return result;
}

static bool cli_signv(struct cli_state *cli, struct iovec *iov, int count,
                      uint32_t *seqnum)
{
        uint8_t *buf;

        /*
         * Obvious optimization: Make cli_calculate_sign_mac work with struct
         * iovec directly. MD5Update would do that just fine.
         */

        if ((count <= 0) || (iov[0].iov_len < smb_wct)) {
                return false;
        }

        buf = iov_concat(talloc_tos(), iov, count);
        if (buf == NULL) {
                return false;
        }

        cli_calculate_sign_mac(cli, (char *)buf, seqnum);
        memcpy(iov[0].iov_base, buf, iov[0].iov_len);

        TALLOC_FREE(buf);
        return true;
}

static void cli_smb_sent(struct tevent_req *subreq);

static bool cli_smb_req_iov_send(struct tevent_req *req,
                                 struct cli_smb_state *state,
                                 struct iovec *iov, int iov_count)
{
        struct tevent_req *subreq;

        if (iov[0].iov_len < smb_wct) {
                return false;
        }

        if (state->mid != 0) {
                SSVAL(iov[0].iov_base, smb_mid, state->mid);
        } else {
                SSVAL(iov[0].iov_base, smb_mid, cli_alloc_mid(state->cli));
        }

        smb_setlen((char *)iov[0].iov_base, iov_len(iov, iov_count) - 4);

        if (!cli_signv(state->cli, iov, iov_count, &state->seqnum)) {
                return false;
        }

        if (cli_encryption_on(state->cli)) {
                NTSTATUS status;
                char *buf, *enc_buf;

                buf = (char *)iov_concat(talloc_tos(), iov, iov_count);
                if (buf == NULL) {
                        return false;
                }
                status = cli_encrypt_message(state->cli, (char *)buf,
                                             &enc_buf);
                TALLOC_FREE(buf);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(0, ("Error in encrypting client message: %s\n",
                                  nt_errstr(status)));
                        return false;
                }
                buf = (char *)talloc_memdup(state, enc_buf,
                                            smb_len(enc_buf)+4);
                SAFE_FREE(enc_buf);
                if (buf == NULL) {
                        return false;
                }
                iov[0].iov_base = buf;
                iov[0].iov_len = talloc_get_size(buf);
                subreq = writev_send(state, state->ev, state->cli->outgoing,
                                     state->cli->fd, iov, 1);
        } else {
                subreq = writev_send(state, state->ev, state->cli->outgoing,
                                     state->cli->fd, iov, iov_count);
        }
        if (subreq == NULL) {
                return false;
        }
        tevent_req_set_callback(subreq, cli_smb_sent, req);
        return true;
}

bool cli_smb_req_send(struct tevent_req *req)
{
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);

        return cli_smb_req_iov_send(req, state, state->iov, state->iov_count);
}

struct tevent_req *cli_smb_send(TALLOC_CTX *mem_ctx,
                                struct event_context *ev,
                                struct cli_state *cli,
                                uint8_t smb_command,
                                uint8_t additional_flags,
                                uint8_t wct, uint16_t *vwv,
                                uint32_t num_bytes,
                                const uint8_t *bytes)
{
        struct tevent_req *req;
        struct iovec iov;

        iov.iov_base = CONST_DISCARD(char *, bytes);
        iov.iov_len = num_bytes;

        req = cli_smb_req_create(mem_ctx, ev, cli, smb_command,
                                 additional_flags, wct, vwv, 1, &iov);
        if (req == NULL) {
                return NULL;
        }
        if (!cli_smb_req_send(req)) {
                TALLOC_FREE(req);
        }
        return req;
}

static void cli_smb_sent(struct tevent_req *subreq)
{
        struct tevent_req *req = tevent_req_callback_data(
                subreq, struct tevent_req);
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);
        ssize_t nwritten;
        int err;

        nwritten = writev_recv(subreq, &err);
        TALLOC_FREE(subreq);
        if (nwritten == -1) {
                tevent_req_nterror(req, map_nt_error_from_unix(err));
                return;
        }

        switch (CVAL(state->header, smb_com)) {
        case SMBtranss:
        case SMBtranss2:
        case SMBnttranss:
        case SMBntcancel:
                state->inbuf = NULL;
                tevent_req_done(req);
                return;
        case SMBlockingX:
                if ((CVAL(state->header, smb_wct) == 8) &&
                    (CVAL(state->vwv+3, 0) == LOCKING_ANDX_OPLOCK_RELEASE)) {
                        state->inbuf = NULL;
                        tevent_req_done(req);
                        return;
                }
        }

        if (!cli_smb_req_set_pending(req)) {
                tevent_req_nterror(req, NT_STATUS_NO_MEMORY);
                return;
        }
}

static void cli_smb_received(struct tevent_req *subreq)
{
        struct cli_state *cli = tevent_req_callback_data(
                subreq, struct cli_state);
        struct tevent_req *req;
        struct cli_smb_state *state;
        struct tevent_context *ev;
        NTSTATUS status;
        uint8_t *inbuf;
        ssize_t received;
        int num_pending;
        int i, err;
        uint16_t mid;

        received = read_smb_recv(subreq, talloc_tos(), &inbuf, &err);
        TALLOC_FREE(subreq);
        if (received == -1) {
                status = map_nt_error_from_unix(err);
                goto fail;
        }

        if ((IVAL(inbuf, 4) != 0x424d53ff) /* 0xFF"SMB" */
            && (SVAL(inbuf, 4) != 0x45ff)) /* 0xFF"E" */ {
                DEBUG(10, ("Got non-SMB PDU\n"));
                status = NT_STATUS_INVALID_NETWORK_RESPONSE;
                goto fail;
        }

        if (cli_encryption_on(cli) && (CVAL(inbuf, 0) == 0)) {
                uint16_t enc_ctx_num;

                status = get_enc_ctx_num(inbuf, &enc_ctx_num);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(10, ("get_enc_ctx_num returned %s\n",
                                   nt_errstr(status)));
                        goto fail;
                }

                if (enc_ctx_num != cli->trans_enc_state->enc_ctx_num) {
                        DEBUG(10, ("wrong enc_ctx %d, expected %d\n",
                                   enc_ctx_num,
                                   cli->trans_enc_state->enc_ctx_num));
                        status = NT_STATUS_INVALID_HANDLE;
                        goto fail;
                }

                status = common_decrypt_buffer(cli->trans_enc_state,
                                               (char *)inbuf);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(10, ("common_decrypt_buffer returned %s\n",
                                   nt_errstr(status)));
                        goto fail;
                }
        }

        mid = SVAL(inbuf, smb_mid);
        num_pending = talloc_array_length(cli->pending);

        for (i=0; i<num_pending; i++) {
                if (mid == cli_smb_req_mid(cli->pending[i])) {
                        break;
                }
        }
        if (i == num_pending) {
                /* Dump unexpected reply */
                TALLOC_FREE(inbuf);
                goto done;
        }

        req = cli->pending[i];
        state = tevent_req_data(req, struct cli_smb_state);
        ev = state->ev;

        if (!cli_check_sign_mac(cli, (char *)inbuf, state->seqnum+1)) {
                DEBUG(10, ("cli_check_sign_mac failed\n"));
                TALLOC_FREE(inbuf);
                status = NT_STATUS_ACCESS_DENIED;
                goto fail;
        }

        if (state->chained_requests == NULL) {
                state->inbuf = talloc_move(state, &inbuf);
                talloc_set_destructor(req, NULL);
                cli_smb_req_destructor(req);
                tevent_req_done(req);
        } else {
                struct tevent_req **chain = talloc_move(
                        talloc_tos(), &state->chained_requests);
                int num_chained = talloc_array_length(chain);

                for (i=0; i<num_chained; i++) {
                        state = tevent_req_data(chain[i], struct
                                                cli_smb_state);
                        state->inbuf = inbuf;
                        state->chain_num = i;
                        tevent_req_done(chain[i]);
                }
                TALLOC_FREE(inbuf);
                TALLOC_FREE(chain);
        }
 done:
        if (talloc_array_length(cli->pending) > 0) {
                /*
                 * Set up another read request for the other pending cli_smb
                 * requests
                 */
                state = tevent_req_data(cli->pending[0], struct cli_smb_state);
                subreq = read_smb_send(cli->pending, state->ev, cli->fd);
                if (subreq == NULL) {
                        status = NT_STATUS_NO_MEMORY;
                        goto fail;
                }
                tevent_req_set_callback(subreq, cli_smb_received, cli);
        }
        return;
 fail:
        /*
         * Cancel all pending requests. We don't do a for-loop walking
         * cli->pending because that array changes in
         * cli_smb_req_destructor().
         */
        while (talloc_array_length(cli->pending) > 0) {
                req = cli->pending[0];
                talloc_set_destructor(req, NULL);
                cli_smb_req_destructor(req);
                tevent_req_nterror(req, status);
        }
}

NTSTATUS cli_smb_recv(struct tevent_req *req, uint8_t min_wct,
                      uint8_t *pwct, uint16_t **pvwv,
                      uint32_t *pnum_bytes, uint8_t **pbytes)
{
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);
        NTSTATUS status = NT_STATUS_OK;
        uint8_t cmd, wct;
        uint16_t num_bytes;
        size_t wct_ofs, bytes_offset;
        int i;

        if (tevent_req_is_nterror(req, &status)) {
                return status;
        }

        if (state->inbuf == NULL) {
                /* This was a request without a reply */
                return NT_STATUS_OK;
        }

        wct_ofs = smb_wct;
        cmd = CVAL(state->inbuf, smb_com);

        for (i=0; i<state->chain_num; i++) {
                if (i < state->chain_num-1) {
                        if (cmd == 0xff) {
                                return NT_STATUS_REQUEST_ABORTED;
                        }
                        if (!is_andx_req(cmd)) {
                                return NT_STATUS_INVALID_NETWORK_RESPONSE;
                        }
                }

                if (!have_andx_command((char *)state->inbuf, wct_ofs)) {
                        /*
                         * This request was not completed because a previous
                         * request in the chain had received an error.
                         */
                        return NT_STATUS_REQUEST_ABORTED;
                }

                wct_ofs = SVAL(state->inbuf, wct_ofs + 3);

                /*
                 * Skip the all-present length field. No overflow, we've just
                 * put a 16-bit value into a size_t.
                 */
                wct_ofs += 4;

                if (wct_ofs+2 > talloc_get_size(state->inbuf)) {
                        return NT_STATUS_INVALID_NETWORK_RESPONSE;
                }

                cmd = CVAL(state->inbuf, wct_ofs + 1);
        }

        status = cli_pull_error((char *)state->inbuf);

        if (!have_andx_command((char *)state->inbuf, wct_ofs)
            && NT_STATUS_IS_ERR(status)) {
                /*
                 * The last command takes the error code. All further commands
                 * down the requested chain will get a
                 * NT_STATUS_REQUEST_ABORTED.
                 */
                return status;
        }

        wct = CVAL(state->inbuf, wct_ofs);
        bytes_offset = wct_ofs + 1 + wct * sizeof(uint16_t);
        num_bytes = SVAL(state->inbuf, bytes_offset);

        if (wct < min_wct) {
                return NT_STATUS_INVALID_NETWORK_RESPONSE;
        }

        /*
         * wct_ofs is a 16-bit value plus 4, wct is a 8-bit value, num_bytes
         * is a 16-bit value. So bytes_offset being size_t should be far from
         * wrapping.
         */
        if ((bytes_offset + 2 > talloc_get_size(state->inbuf))
            || (bytes_offset > 0xffff)) {
                return NT_STATUS_INVALID_NETWORK_RESPONSE;
        }

        if (pwct != NULL) {
                *pwct = wct;
        }
        if (pvwv != NULL) {
                *pvwv = (uint16_t *)(state->inbuf + wct_ofs + 1);
        }
        if (pnum_bytes != NULL) {
                *pnum_bytes = num_bytes;
        }
        if (pbytes != NULL) {
                *pbytes = (uint8_t *)state->inbuf + bytes_offset + 2;
        }

        return NT_STATUS_OK;
}

size_t cli_smb_wct_ofs(struct tevent_req **reqs, int num_reqs)
{
        size_t wct_ofs;
        int i;

        wct_ofs = smb_wct - 4;

        for (i=0; i<num_reqs; i++) {
                struct cli_smb_state *state;
                state = tevent_req_data(reqs[i], struct cli_smb_state);
                wct_ofs += iov_len(state->iov+1, state->iov_count-1);
                wct_ofs = (wct_ofs + 3) & ~3;
        }
        return wct_ofs;
}

bool cli_smb_chain_send(struct tevent_req **reqs, int num_reqs)
{
        struct cli_smb_state *first_state = tevent_req_data(
                reqs[0], struct cli_smb_state);
        struct cli_smb_state *last_state = tevent_req_data(
                reqs[num_reqs-1], struct cli_smb_state);
        struct cli_smb_state *state;
        size_t wct_offset;
        size_t chain_padding = 0;
        int i, iovlen;
        struct iovec *iov = NULL;
        struct iovec *this_iov;

        iovlen = 0;
        for (i=0; i<num_reqs; i++) {
                state = tevent_req_data(reqs[i], struct cli_smb_state);
                iovlen += state->iov_count;
        }

        iov = talloc_array(last_state, struct iovec, iovlen);
        if (iov == NULL) {
                goto fail;
        }

        first_state->chained_requests = (struct tevent_req **)talloc_memdup(
                last_state, reqs, sizeof(*reqs) * num_reqs);
        if (first_state->chained_requests == NULL) {
                goto fail;
        }

        wct_offset = smb_wct - 4;
        this_iov = iov;

        for (i=0; i<num_reqs; i++) {
                size_t next_padding = 0;
                uint16_t *vwv;

                state = tevent_req_data(reqs[i], struct cli_smb_state);

                if (i < num_reqs-1) {
                        if (!is_andx_req(CVAL(state->header, smb_com))
                            || CVAL(state->header, smb_wct) < 2) {
                                goto fail;
                        }
                }

                wct_offset += iov_len(state->iov+1, state->iov_count-1) + 1;
                if ((wct_offset % 4) != 0) {
                        next_padding = 4 - (wct_offset % 4);
                }
                wct_offset += next_padding;
                vwv = state->vwv;

                if (i < num_reqs-1) {
                        struct cli_smb_state *next_state = tevent_req_data(
                                reqs[i+1], struct cli_smb_state);
                        SCVAL(vwv+0, 0, CVAL(next_state->header, smb_com));
                        SCVAL(vwv+0, 1, 0);
                        SSVAL(vwv+1, 0, wct_offset);
                } else if (is_andx_req(CVAL(state->header, smb_com))) {
                        /* properly end the chain */
                        SCVAL(vwv+0, 0, 0xff);
                        SCVAL(vwv+0, 1, 0xff);
                        SSVAL(vwv+1, 0, 0);
                }

                if (i == 0) {
                        this_iov[0] = state->iov[0];
                } else {
                        /*
                         * This one is a bit subtle. We have to add
                         * chain_padding bytes between the requests, and we
                         * have to also include the wct field of the
                         * subsequent requests. We use the subsequent header
                         * for the padding, it contains the wct field in its
                         * last byte.
                         */
                        this_iov[0].iov_len = chain_padding+1;
                        this_iov[0].iov_base = &state->header[
                                sizeof(state->header) - this_iov[0].iov_len];
                        memset(this_iov[0].iov_base, 0, this_iov[0].iov_len-1);
                }
                memcpy(this_iov+1, state->iov+1,
                       sizeof(struct iovec) * (state->iov_count-1));
                this_iov += state->iov_count;
                chain_padding = next_padding;
        }

        if (!cli_smb_req_iov_send(reqs[0], last_state, iov, iovlen)) {
                goto fail;
        }
        return true;
 fail:
        TALLOC_FREE(iov);
        return false;
}

uint8_t *cli_smb_inbuf(struct tevent_req *req)
{
        struct cli_smb_state *state = tevent_req_data(
                req, struct cli_smb_state);
        return state->inbuf;
}

bool cli_has_async_calls(struct cli_state *cli)
{
        return ((tevent_queue_length(cli->outgoing) != 0)
                || (talloc_array_length(cli->pending) != 0));
}