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[Samba.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"

static void cli_state_handler(struct event_context *event_ctx,
                              struct fd_event *event, uint16 flags, void *p);

/*
 * Read an smb packet asynchronously, discard keepalives
 */

struct read_smb_state {
        struct tevent_context *ev;
        int fd;
        uint8_t *buf;
};

static ssize_t read_smb_more(uint8_t *buf, size_t buflen, void *private_data);
static void read_smb_done(struct tevent_req *subreq);

static struct tevent_req *read_smb_send(TALLOC_CTX *mem_ctx,
                                        struct tevent_context *ev,
                                        int fd)
{
        struct tevent_req *result, *subreq;
        struct read_smb_state *state;

        result = tevent_req_create(mem_ctx, &state, struct read_smb_state);
        if (result == NULL) {
                return NULL;
        }
        state->ev = ev;
        state->fd = fd;

        subreq = read_packet_send(state, ev, fd, 4, read_smb_more, NULL);
        if (subreq == NULL) {
                goto fail;
        }
        tevent_req_set_callback(subreq, read_smb_done, result);
        return result;
 fail:
        TALLOC_FREE(result);
        return NULL;
}

static ssize_t read_smb_more(uint8_t *buf, size_t buflen, void *private_data)
{
        if (buflen > 4) {
                return 0;       /* We've been here, we're done */
        }
        return smb_len_large(buf);
}

static void read_smb_done(struct tevent_req *subreq)
{
        struct tevent_req *req = tevent_req_callback_data(
                subreq, struct tevent_req);
        struct read_smb_state *state = tevent_req_data(
                req, struct read_smb_state);
        ssize_t len;
        int err;

        len = read_packet_recv(subreq, state, &state->buf, &err);
        TALLOC_FREE(subreq);
        if (len == -1) {
                tevent_req_error(req, err);
                return;
        }

        if (CVAL(state->buf, 0) == SMBkeepalive) {
                subreq = read_packet_send(state, state->ev, state->fd, 4,
                                          read_smb_more, NULL);
                if (tevent_req_nomem(subreq, req)) {
                        return;
                }
                tevent_req_set_callback(subreq, read_smb_done, req);
                return;
        }
        tevent_req_done(req);
}

static ssize_t read_smb_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
                             uint8_t **pbuf, int *perrno)
{
        struct read_smb_state *state = tevent_req_data(
                req, struct read_smb_state);

        if (tevent_req_is_unix_error(req, perrno)) {
                return -1;
        }
        *pbuf = talloc_move(mem_ctx, &state->buf);
        return talloc_get_size(*pbuf);
}

/**
 * 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;
}

/**
 * Allocate a new mid
 * @param[in] cli       The client connection
 * @retval              The new, unused mid
 */

static uint16_t cli_new_mid(struct cli_state *cli)
{
        uint16_t result;
        struct cli_request *req;

        while (true) {
                result = cli->mid++;
                if (result == 0) {
                        continue;
                }

                for (req = cli->outstanding_requests; req; req = req->next) {
                        if (result == req->mid) {
                                break;
                        }
                }

                if (req == NULL) {
                        return result;
                }
        }
}

/**
 * Print an async req that happens to be a cli_request
 * @param[in] mem_ctx   The TALLOC_CTX to put the result on
 * @param[in] req       The request to print
 * @retval              The string representation of "req"
 */

static char *cli_request_print(TALLOC_CTX *mem_ctx, struct async_req *req)
{
        char *result = async_req_print(mem_ctx, req);
        struct cli_request *cli_req = talloc_get_type_abort(
                req->private_data, struct cli_request);

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

        return talloc_asprintf_append_buffer(
                result, "mid=%d\n", cli_req->mid);
}

/**
 * Destroy a cli_request
 * @param[in] req       The cli_request to kill
 * @retval Can't fail
 */

static int cli_request_destructor(struct cli_request *req)
{
        if (req->enc_state != NULL) {
                common_free_enc_buffer(req->enc_state, (char *)req->outbuf);
        }
        DLIST_REMOVE(req->cli->outstanding_requests, req);
        if (req->cli->outstanding_requests == NULL) {
                TALLOC_FREE(req->cli->fd_event);
        }
        return 0;
}

/**
 * Are there already requests waiting in the chain_accumulator?
 * @param[in] cli       The cli_state we want to check
 * @retval reply :-)
 */

bool cli_in_chain(struct cli_state *cli)
{
        if (cli->chain_accumulator == NULL) {
                return false;
        }

        return (cli->chain_accumulator->num_async != 0);
}

/**
 * @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;
}

/**
 * @brief Destroy an async_req that is the visible part of a cli_request
 * @param[in] req       The request to kill
 * @retval Return 0 to make talloc happy
 *
 * This destructor is a bit tricky: Because a cli_request can host more than
 * one async_req for chained requests, we need to make sure that the
 * "cli_request" that we were part of is correctly destroyed at the right
 * time. This is done by NULLing out ourself from the "async" member of our
 * "cli_request". If there is none left, then also TALLOC_FREE() the
 * cli_request, which was a talloc child of the client connection cli_state.
 */

static int cli_async_req_destructor(struct async_req *req)
{
        struct cli_request *cli_req = talloc_get_type_abort(
                req->private_data, struct cli_request);
        int i, pending;
        bool found = false;

        pending = 0;

        for (i=0; i<cli_req->num_async; i++) {
                if (cli_req->async[i] == req) {
                        cli_req->async[i] = NULL;
                        found = true;
                }
                if (cli_req->async[i] != NULL) {
                        pending += 1;
                }
        }

        SMB_ASSERT(found);

        if (pending == 0) {
                TALLOC_FREE(cli_req);
        }

        return 0;
}

/**
 * @brief Chain up a request
 * @param[in] mem_ctx           The TALLOC_CTX for the result
 * @param[in] ev                The event context that will call us back
 * @param[in] cli               The cli_state we queue the request up for
 * @param[in] smb_command       The command that we want to issue
 * @param[in] additional_flags  open_and_x wants to add oplock header flags
 * @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
 *
 * cli_request_chain() is the core of the SMB request marshalling routine. It
 * will create a new async_req structure in the cli->chain_accumulator->async
 * array and marshall the smb_cmd, the vwv array and the bytes into
 * cli->chain_accumulator->outbuf.
 */

static struct async_req *cli_request_chain(TALLOC_CTX *mem_ctx,
                                           struct event_context *ev,
                                           struct cli_state *cli,
                                           uint8_t smb_command,
                                           uint8_t additional_flags,
                                           uint8_t wct, const uint16_t *vwv,
                                           size_t bytes_alignment,
                                           uint32_t num_bytes,
                                           const uint8_t *bytes)
{
        struct async_req **tmp_reqs;
        struct cli_request *req;

        req = cli->chain_accumulator;

        tmp_reqs = TALLOC_REALLOC_ARRAY(req, req->async, struct async_req *,
                                        req->num_async + 1);
        if (tmp_reqs == NULL) {
                DEBUG(0, ("talloc failed\n"));
                return NULL;
        }
        req->async = tmp_reqs;
        req->num_async += 1;

        req->async[req->num_async-1] = async_req_new(mem_ctx);
        if (req->async[req->num_async-1] == NULL) {
                DEBUG(0, ("async_req_new failed\n"));
                req->num_async -= 1;
                return NULL;
        }
        req->async[req->num_async-1]->private_data = req;
        req->async[req->num_async-1]->print = cli_request_print;
        talloc_set_destructor(req->async[req->num_async-1],
                              cli_async_req_destructor);

        if (!smb_splice_chain(&req->outbuf, smb_command, wct, vwv,
                              bytes_alignment, num_bytes, bytes)) {
                goto fail;
        }

        return req->async[req->num_async-1];

 fail:
        TALLOC_FREE(req->async[req->num_async-1]);
        req->num_async -= 1;
        return NULL;
}

/**
 * @brief prepare a cli_state to accept a chain of requests
 * @param[in] cli       The cli_state we want to queue up in
 * @param[in] ev        The event_context that will call us back for the socket
 * @param[in] size_hint How many bytes are expected, just an optimization
 * @retval Did we have enough memory?
 *
 * cli_chain_cork() sets up a new cli_request in cli->chain_accumulator. If
 * cli is used in an async fashion, i.e. if we have outstanding requests, then
 * we do not have to create a fd event. If cli is used only with the sync
 * helpers, we need to create the fd_event here.
 *
 * If you want to issue a chained request to the server, do a
 * cli_chain_cork(), then do you cli_open_send(), cli_read_and_x_send(),
 * cli_close_send() and so on. The async requests that come out of
 * cli_xxx_send() are normal async requests with the difference that they
 * won't be shipped individually. But the event_context will still trigger the
 * req->async.fn to be called on every single request.
 *
 * You have to take care yourself that you only issue chainable requests in
 * the middle of the chain.
 */

bool cli_chain_cork(struct cli_state *cli, struct event_context *ev,
                    size_t size_hint)
{
        struct cli_request *req = NULL;

        SMB_ASSERT(cli->chain_accumulator == NULL);

        if (cli->fd == -1) {
                DEBUG(10, ("cli->fd closed\n"));
                return false;
        }

        if (cli->fd_event == NULL) {
                SMB_ASSERT(cli->outstanding_requests == NULL);
                cli->fd_event = event_add_fd(ev, cli, cli->fd,
                                             EVENT_FD_READ,
                                             cli_state_handler, cli);
                if (cli->fd_event == NULL) {
                        return false;
                }
        }

        req = talloc(cli, struct cli_request);
        if (req == NULL) {
                goto fail;
        }
        req->cli = cli;

        if (size_hint == 0) {
                size_hint = 100;
        }
        req->outbuf = talloc_array(req, uint8_t, smb_wct + size_hint);
        if (req->outbuf == NULL) {
                goto fail;
        }
        req->outbuf = TALLOC_REALLOC_ARRAY(NULL, req->outbuf, uint8_t,
                                           smb_wct);

        req->num_async = 0;
        req->async = NULL;

        req->enc_state = NULL;
        req->recv_helper.fn = NULL;

        SSVAL(req->outbuf, smb_tid, cli->cnum);
        cli_setup_packet_buf(cli, (char *)req->outbuf);

        req->mid = cli_new_mid(cli);

        cli->chain_accumulator = req;

        DEBUG(10, ("cli_chain_cork: mid=%d\n", req->mid));

        return true;
 fail:
        TALLOC_FREE(req);
        if (cli->outstanding_requests == NULL) {
                TALLOC_FREE(cli->fd_event);
        }
        return false;
}

/**
 * Ship a request queued up via cli_request_chain()
 * @param[in] cl        The connection
 */

void cli_chain_uncork(struct cli_state *cli)
{
        struct cli_request *req = cli->chain_accumulator;
        size_t smblen;

        SMB_ASSERT(req != NULL);

        DLIST_ADD_END(cli->outstanding_requests, req, struct cli_request *);
        talloc_set_destructor(req, cli_request_destructor);

        cli->chain_accumulator = NULL;

        SSVAL(req->outbuf, smb_mid, req->mid);

        smblen = talloc_get_size(req->outbuf) - 4;

        smb_setlen((char *)req->outbuf, smblen);

        if (smblen > 0x1ffff) {
                /*
                 * This is a POSIX 14 word large write. Overwrite just the
                 * size field, the '0xFFSMB' has been set by smb_setlen which
                 * _smb_setlen_large does not do.
                 */
                _smb_setlen_large(((char *)req->outbuf), smblen);
        }

        cli_calculate_sign_mac(cli, (char *)req->outbuf);

        if (cli_encryption_on(cli)) {
                NTSTATUS status;
                char *enc_buf;

                status = cli_encrypt_message(cli, (char *)req->outbuf,
                                             &enc_buf);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(0, ("Error in encrypting client message. "
                                  "Error %s\n", nt_errstr(status)));
                        TALLOC_FREE(req);
                        return;
                }
                req->outbuf = (uint8_t *)enc_buf;
                req->enc_state = cli->trans_enc_state;
        }

        req->sent = 0;

        event_fd_set_writeable(cli->fd_event);
}

/**
 * @brief Send a request to the server
 * @param[in] mem_ctx           The TALLOC_CTX for the result
 * @param[in] ev                The event context that will call us back
 * @param[in] cli               The cli_state we queue the request up for
 * @param[in] smb_command       The command that we want to issue
 * @param[in] additional_flags  open_and_x wants to add oplock header flags
 * @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
 *
 * This is the generic routine to be used by the cli_xxx_send routines.
 */

struct async_req *cli_request_send(TALLOC_CTX *mem_ctx,
                                   struct event_context *ev,
                                   struct cli_state *cli,
                                   uint8_t smb_command,
                                   uint8_t additional_flags,
                                   uint8_t wct, const uint16_t *vwv,
                                   size_t bytes_alignment,
                                   uint32_t num_bytes, const uint8_t *bytes)
{
        struct async_req *result;
        bool uncork = false;

        if (cli->chain_accumulator == NULL) {
                if (!cli_chain_cork(cli, ev,
                                    wct * sizeof(uint16_t) + num_bytes + 3)) {
                        DEBUG(1, ("cli_chain_cork failed\n"));
                        return NULL;
                }
                uncork = true;
        }

        result = cli_request_chain(mem_ctx, ev, cli, smb_command,
                                   additional_flags, wct, vwv, bytes_alignment,
                                   num_bytes, bytes);

        if (result == NULL) {
                DEBUG(1, ("cli_request_chain failed\n"));
        }

        if (uncork) {
                cli_chain_uncork(cli);
        }

        return result;
}

/**
 * Calculate the current ofs to wct for requests like write&x
 * @param[in] req       The smb request we're currently building
 * @retval how many bytes offset have we accumulated?
 */

uint16_t cli_wct_ofs(const struct cli_state *cli)
{
        size_t buf_size;

        if (cli->chain_accumulator == NULL) {
                return smb_wct - 4;
        }

        buf_size = talloc_get_size(cli->chain_accumulator->outbuf);

        if (buf_size == smb_wct) {
                return smb_wct - 4;
        }

        /*
         * Add alignment for subsequent requests
         */

        if ((buf_size % 4) != 0) {
                buf_size += (4 - (buf_size % 4));
        }

        return buf_size - 4;
}

/**
 * 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);
}

/**
 * @brief Pull reply data out of a request
 * @param[in] req               The request that we just received a reply for
 * @param[out] pwct             How many words did the server send?
 * @param[out] pvwv             The words themselves
 * @param[out] pnum_bytes       How many bytes did the server send?
 * @param[out] pbytes           The bytes themselves
 * @retval Was the reply formally correct?
 */

NTSTATUS cli_pull_reply(struct async_req *req,
                        uint8_t *pwct, uint16_t **pvwv,
                        uint16_t *pnum_bytes, uint8_t **pbytes)
{
        struct cli_request *cli_req = talloc_get_type_abort(
                req->private_data, struct cli_request);
        uint8_t wct, cmd;
        uint16_t num_bytes;
        size_t wct_ofs, bytes_offset;
        int i, j;
        NTSTATUS status;

        for (i = 0; i < cli_req->num_async; i++) {
                if (req == cli_req->async[i]) {
                        break;
                }
        }

        if (i == cli_req->num_async) {
                cli_set_error(cli_req->cli, NT_STATUS_INVALID_PARAMETER);
                return NT_STATUS_INVALID_PARAMETER;
        }

        /**
         * The status we pull here is only relevant for the last reply in the
         * chain.
         */

        status = cli_pull_error(cli_req->inbuf);

        if (i == 0) {
                if (NT_STATUS_IS_ERR(status)
                    && !have_andx_command(cli_req->inbuf, smb_wct)) {
                        cli_set_error(cli_req->cli, status);
                        return status;
                }
                wct_ofs = smb_wct;
                goto done;
        }

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

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

                if (!have_andx_command(cli_req->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(cli_req->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(cli_req->inbuf)) {
                        return NT_STATUS_INVALID_NETWORK_RESPONSE;
                }

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

        if (!have_andx_command(cli_req->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;
        }

 done:
        wct = CVAL(cli_req->inbuf, wct_ofs);

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

        /*
         * 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(cli_req->inbuf))
            || (bytes_offset > 0xffff)) {
                return NT_STATUS_INVALID_NETWORK_RESPONSE;
        }

        *pwct = wct;
        *pvwv = (uint16_t *)(cli_req->inbuf + wct_ofs + 1);
        *pnum_bytes = num_bytes;
        *pbytes = (uint8_t *)cli_req->inbuf + bytes_offset + 2;

        return NT_STATUS_OK;
}

/**
 * Decrypt a PDU, check the signature
 * @param[in] cli       The cli_state that received something
 * @param[in] pdu       The incoming bytes
 * @retval error code
 */


static NTSTATUS validate_smb_crypto(struct cli_state *cli, char *pdu)
{
        NTSTATUS status;

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

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

                status = get_enc_ctx_num((uint8_t *)pdu, &enc_ctx_num);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(10, ("get_enc_ctx_num returned %s\n",
                                   nt_errstr(status)));
                        return status;
                }

                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));
                        return NT_STATUS_INVALID_HANDLE;
                }

                status = common_decrypt_buffer(cli->trans_enc_state, pdu);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(10, ("common_decrypt_buffer returned %s\n",
                                   nt_errstr(status)));
                        return status;
                }
        }

        if (!cli_check_sign_mac(cli, pdu)) {
                DEBUG(10, ("cli_check_sign_mac failed\n"));
                close(cli->fd);
                cli->fd = -1;
                return NT_STATUS_ACCESS_DENIED;
        }

        return NT_STATUS_OK;
}

/**
 * A PDU has arrived on cli->evt_inbuf
 * @param[in] cli       The cli_state that received something
 */

static void handle_incoming_pdu(struct cli_state *cli)
{
        struct cli_request *req, *next;
        uint16_t mid;
        size_t raw_pdu_len, buf_len, pdu_len, rest_len;
        char *pdu;
        int i;
        NTSTATUS status;

        int num_async;

        /*
         * The encrypted PDU len might differ from the unencrypted one
         */
        raw_pdu_len = smb_len(cli->evt_inbuf) + 4;
        buf_len = talloc_get_size(cli->evt_inbuf);
        rest_len = buf_len - raw_pdu_len;

        if (buf_len == raw_pdu_len) {
                /*
                 * Optimal case: Exactly one PDU was in the socket buffer
                 */
                pdu = cli->evt_inbuf;
                cli->evt_inbuf = NULL;
        }
        else {
                DEBUG(11, ("buf_len = %d, raw_pdu_len = %d, splitting "
                           "buffer\n", (int)buf_len, (int)raw_pdu_len));

                if (raw_pdu_len < rest_len) {
                        /*
                         * The PDU is shorter, talloc_memdup that one.
                         */
                        pdu = (char *)talloc_memdup(
                                cli, cli->evt_inbuf, raw_pdu_len);

                        memmove(cli->evt_inbuf, cli->evt_inbuf + raw_pdu_len,
                                buf_len - raw_pdu_len);

                        cli->evt_inbuf = TALLOC_REALLOC_ARRAY(
                                NULL, cli->evt_inbuf, char, rest_len);

                        if (pdu == NULL) {
                                status = NT_STATUS_NO_MEMORY;
                                goto invalidate_requests;
                        }
                }
                else {
                        /*
                         * The PDU is larger than the rest, talloc_memdup the
                         * rest
                         */
                        pdu = cli->evt_inbuf;

                        cli->evt_inbuf = (char *)talloc_memdup(
                                cli, pdu + raw_pdu_len, rest_len);

                        if (cli->evt_inbuf == NULL) {
                                status = NT_STATUS_NO_MEMORY;
                                goto invalidate_requests;
                        }
                }
        }

        if ((raw_pdu_len == 4) && (CVAL(pdu, 0) == SMBkeepalive)) {
                DEBUG(10, ("Got keepalive\n"));
                TALLOC_FREE(pdu);
                return;
        }

        status = validate_smb_crypto(cli, pdu);
        if (!NT_STATUS_IS_OK(status)) {
                goto invalidate_requests;
        }

        mid = SVAL(pdu, smb_mid);

        DEBUG(10, ("handle_incoming_pdu: got mid %d\n", mid));

        for (req = cli->outstanding_requests; req; req = req->next) {
                if (req->mid == mid) {
                        break;
                }
        }

        pdu_len = smb_len(pdu) + 4;

        if (req == NULL) {
                DEBUG(3, ("Request for mid %d not found, dumping PDU\n", mid));

                TALLOC_FREE(pdu);
                return;
        }

        req->inbuf = talloc_move(req, &pdu);

        /*
         * Freeing the last async_req will free the req (see
         * cli_async_req_destructor). So make a copy of req->num_async, we
         * can't reference it in the last round.
         */

        num_async = req->num_async;

        for (i=0; i<num_async; i++) {
                /**
                 * A request might have been talloc_free()'ed before we arrive
                 * here. It will have removed itself from req->async via its
                 * destructor cli_async_req_destructor().
                 */
                if (req->async[i] != NULL) {
                        if (req->recv_helper.fn != NULL) {
                                req->recv_helper.fn(req->async[i]);
                        } else {
                                async_req_done(req->async[i]);
                        }
                }
        }
        return;

 invalidate_requests:

        DEBUG(10, ("handle_incoming_pdu: Aborting with %s\n",
                   nt_errstr(status)));

        for (req = cli->outstanding_requests; req; req = next) {
                next = req->next;
                if (req->num_async) {
                        async_req_nterror(req->async[0], status);
                }
        }
        return;
}

/**
 * fd event callback. This is the basic connection to the socket
 * @param[in] event_ctx The event context that called us
 * @param[in] event     The event that fired
 * @param[in] flags     EVENT_FD_READ | EVENT_FD_WRITE
 * @param[in] p         private_data, in this case the cli_state
 */

static void cli_state_handler(struct event_context *event_ctx,
                              struct fd_event *event, uint16 flags, void *p)
{
        struct cli_state *cli = (struct cli_state *)p;
        struct cli_request *req, *next;
        NTSTATUS status;

        DEBUG(11, ("cli_state_handler called with flags %d\n", flags));

        if (cli->fd == -1) {
                status = NT_STATUS_CONNECTION_INVALID;
                goto sock_error;
        }

        if (flags & EVENT_FD_WRITE) {
                size_t to_send;
                ssize_t sent;

                for (req = cli->outstanding_requests; req; req = req->next) {
                        to_send = smb_len(req->outbuf)+4;
                        if (to_send > req->sent) {
                                break;
                        }
                }

                if (req == NULL) {
                        if (cli->fd_event != NULL) {
                                event_fd_set_not_writeable(cli->fd_event);
                        }
                        return;
                }

                sent = sys_send(cli->fd, req->outbuf + req->sent,
                            to_send - req->sent, 0);

                if (sent < 0) {
                        status = map_nt_error_from_unix(errno);
                        goto sock_error;
                }

                req->sent += sent;

                if (req->sent == to_send) {
                        return;
                }
        }

        if (flags & EVENT_FD_READ) {
                int res, available;
                size_t old_size, new_size;
                char *tmp;

                res = ioctl(cli->fd, FIONREAD, &available);
                if (res == -1) {
                        DEBUG(10, ("ioctl(FIONREAD) failed: %s\n",
                                   strerror(errno)));
                        status = map_nt_error_from_unix(errno);
                        goto sock_error;
                }

                if (available == 0) {
                        /* EOF */
                        status = NT_STATUS_END_OF_FILE;
                        goto sock_error;
                }

                old_size = talloc_get_size(cli->evt_inbuf);
                new_size = old_size + available;

                if (new_size < old_size) {
                        /* wrap */
                        status = NT_STATUS_UNEXPECTED_IO_ERROR;
                        goto sock_error;
                }

                tmp = TALLOC_REALLOC_ARRAY(cli, cli->evt_inbuf, char,
                                           new_size);
                if (tmp == NULL) {
                        /* nomem */
                        status = NT_STATUS_NO_MEMORY;
                        goto sock_error;
                }
                cli->evt_inbuf = tmp;

                res = sys_recv(cli->fd, cli->evt_inbuf + old_size, available, 0);
                if (res == -1) {
                        DEBUG(10, ("recv failed: %s\n", strerror(errno)));
                        status = map_nt_error_from_unix(errno);
                        goto sock_error;
                }

                DEBUG(11, ("cli_state_handler: received %d bytes, "
                           "smb_len(evt_inbuf) = %d\n", (int)res,
                           smb_len(cli->evt_inbuf)));

                /* recv *might* have returned less than announced */
                new_size = old_size + res;

                /* shrink, so I don't expect errors here */
                cli->evt_inbuf = TALLOC_REALLOC_ARRAY(cli, cli->evt_inbuf,
                                                      char, new_size);

                while ((cli->evt_inbuf != NULL)
                       && ((smb_len(cli->evt_inbuf) + 4) <= new_size)) {
                        /*
                         * we've got a complete NBT level PDU in evt_inbuf
                         */
                        handle_incoming_pdu(cli);
                        new_size = talloc_get_size(cli->evt_inbuf);
                }
        }

        return;

 sock_error:

        for (req = cli->outstanding_requests; req; req = next) {
                int i, num_async;

                next = req->next;
                num_async = req->num_async;

                for (i=0; i<num_async; i++) {
                        async_req_nterror(req->async[i], status);
                }
        }
        TALLOC_FREE(cli->fd_event);
        if (cli->fd != -1) {
                close(cli->fd);
                cli->fd = -1;
        }
}


struct cli_session_request_state {
        struct tevent_context *ev;
        int sock;
        uint32 len_hdr;
        struct iovec iov[3];
        uint8_t nb_session_response;
};

static void cli_session_request_sent(struct tevent_req *subreq);
static void cli_session_request_recvd(struct tevent_req *subreq);

struct tevent_req *cli_session_request_send(TALLOC_CTX *mem_ctx,
                                            struct tevent_context *ev,
                                            int sock,
                                            const struct nmb_name *called,
                                            const struct nmb_name *calling)
{
        struct tevent_req *req, *subreq;
        struct cli_session_request_state *state;

        req = tevent_req_create(mem_ctx, &state,
                                struct cli_session_request_state);
        if (req == NULL) {
                return NULL;
        }
        state->ev = ev;
        state->sock = sock;

        state->iov[1].iov_base = name_mangle(
                state, called->name, called->name_type);
        if (tevent_req_nomem(state->iov[1].iov_base, req)) {
                return tevent_req_post(req, ev);
        }
        state->iov[1].iov_len = name_len(
                (char *)state->iov[1].iov_base);

        state->iov[2].iov_base = name_mangle(
                state, calling->name, calling->name_type);
        if (tevent_req_nomem(state->iov[2].iov_base, req)) {
                return tevent_req_post(req, ev);
        }
        state->iov[2].iov_len = name_len(
                (char *)state->iov[2].iov_base);

        _smb_setlen(((char *)&state->len_hdr),
                    state->iov[1].iov_len + state->iov[2].iov_len);
        SCVAL((char *)&state->len_hdr, 0, 0x81);

        state->iov[0].iov_base = &state->len_hdr;
        state->iov[0].iov_len = sizeof(state->len_hdr);

        subreq = writev_send(state, ev, NULL, sock, state->iov, 3);
        if (tevent_req_nomem(subreq, req)) {
                return tevent_req_post(req, ev);
        }
        tevent_req_set_callback(subreq, cli_session_request_sent, req);
        return req;
}

static void cli_session_request_sent(struct tevent_req *subreq)
{
        struct tevent_req *req = tevent_req_callback_data(
                subreq, struct tevent_req);
        struct cli_session_request_state *state = tevent_req_data(
                req, struct cli_session_request_state);
        ssize_t ret;
        int err;

        ret = writev_recv(subreq, &err);
        TALLOC_FREE(subreq);
        if (ret == -1) {
                tevent_req_error(req, err);
                return;
        }
        subreq = read_smb_send(state, state->ev, state->sock);
        if (tevent_req_nomem(subreq, req)) {
                return;
        }
        tevent_req_set_callback(subreq, cli_session_request_recvd, req);
}

static void cli_session_request_recvd(struct tevent_req *subreq)
{
        struct tevent_req *req = tevent_req_callback_data(
                subreq, struct tevent_req);
        struct cli_session_request_state *state = tevent_req_data(
                req, struct cli_session_request_state);
        uint8_t *buf;
        ssize_t ret;
        int err;

        ret = read_smb_recv(subreq, talloc_tos(), &buf, &err);
        TALLOC_FREE(subreq);

        if (ret < 4) {
                ret = -1;
                err = EIO;
        }
        if (ret == -1) {
                tevent_req_error(req, err);
                return;
        }
        /*
         * In case of an error there is more information in the data
         * portion according to RFC1002. We're not subtle enough to
         * respond to the different error conditions, so drop the
         * error info here.
         */
        state->nb_session_response = CVAL(buf, 0);
        tevent_req_done(req);
}

bool cli_session_request_recv(struct tevent_req *req, int *err, uint8_t *resp)
{
        struct cli_session_request_state *state = tevent_req_data(
                req, struct cli_session_request_state);

        if (tevent_req_is_unix_error(req, err)) {
                return false;
        }
        *resp = state->nb_session_response;
        return true;
}