Move routines to manipulate WAL into PostgreSQL::Test::Cluster

[pgsql.git] / src / interfaces / libpq / fe-secure-gssapi.c

/*-------------------------------------------------------------------------
 *
 * fe-secure-gssapi.c
 *   The front-end (client) encryption support for GSSAPI
 *
 * Portions Copyright (c) 2016-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *  src/interfaces/libpq/fe-secure-gssapi.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres_fe.h"

#include "fe-gssapi-common.h"
#include "libpq-fe.h"
#include "libpq-int.h"
#include "port/pg_bswap.h"


/*
 * Require encryption support, as well as mutual authentication and
 * tamperproofing measures.
 */
#define GSS_REQUIRED_FLAGS GSS_C_MUTUAL_FLAG | GSS_C_REPLAY_FLAG | \
        GSS_C_SEQUENCE_FLAG | GSS_C_CONF_FLAG | GSS_C_INTEG_FLAG

/*
 * Handle the encryption/decryption of data using GSSAPI.
 *
 * In the encrypted data stream on the wire, we break up the data
 * into packets where each packet starts with a uint32-size length
 * word (in network byte order), then encrypted data of that length
 * immediately following.  Decryption yields the same data stream
 * that would appear when not using encryption.
 *
 * Encrypted data typically ends up being larger than the same data
 * unencrypted, so we use fixed-size buffers for handling the
 * encryption/decryption which are larger than PQComm's buffer will
 * typically be to minimize the times where we have to make multiple
 * packets (and therefore multiple recv/send calls for a single
 * read/write call to us).
 *
 * NOTE: The client and server have to agree on the max packet size,
 * because we have to pass an entire packet to GSSAPI at a time and we
 * don't want the other side to send arbitrarily huge packets as we
 * would have to allocate memory for them to then pass them to GSSAPI.
 *
 * Therefore, these two #define's are effectively part of the protocol
 * spec and can't ever be changed.
 */
#define PQ_GSS_SEND_BUFFER_SIZE 16384
#define PQ_GSS_RECV_BUFFER_SIZE 16384

/*
 * We need these state variables per-connection.  To allow the functions
 * in this file to look mostly like those in be-secure-gssapi.c, set up
 * these macros.
 */
#define PqGSSSendBuffer (conn->gss_SendBuffer)
#define PqGSSSendLength (conn->gss_SendLength)
#define PqGSSSendNext (conn->gss_SendNext)
#define PqGSSSendConsumed (conn->gss_SendConsumed)
#define PqGSSRecvBuffer (conn->gss_RecvBuffer)
#define PqGSSRecvLength (conn->gss_RecvLength)
#define PqGSSResultBuffer (conn->gss_ResultBuffer)
#define PqGSSResultLength (conn->gss_ResultLength)
#define PqGSSResultNext (conn->gss_ResultNext)
#define PqGSSMaxPktSize (conn->gss_MaxPktSize)


/*
 * Attempt to write len bytes of data from ptr to a GSSAPI-encrypted connection.
 *
 * The connection must be already set up for GSSAPI encryption (i.e., GSSAPI
 * transport negotiation is complete).
 *
 * On success, returns the number of data bytes consumed (possibly less than
 * len).  On failure, returns -1 with errno set appropriately.  If the errno
 * indicates a non-retryable error, a message is added to conn->errorMessage.
 * For retryable errors, caller should call again (passing the same or more
 * data) once the socket is ready.
 */
ssize_t
pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
{
        OM_uint32       major,
                                minor;
        gss_buffer_desc input,
                                output = GSS_C_EMPTY_BUFFER;
        ssize_t         ret = -1;
        size_t          bytes_to_encrypt;
        size_t          bytes_encrypted;
        gss_ctx_id_t gctx = conn->gctx;

        /*
         * When we get a retryable failure, we must not tell the caller we have
         * successfully transmitted everything, else it won't retry.  For
         * simplicity, we claim we haven't transmitted anything until we have
         * successfully transmitted all "len" bytes.  Between calls, the amount of
         * the current input data that's already been encrypted and placed into
         * PqGSSSendBuffer (and perhaps transmitted) is remembered in
         * PqGSSSendConsumed.  On a retry, the caller *must* be sending that data
         * again, so if it offers a len less than that, something is wrong.
         *
         * Note: it may seem attractive to report partial write completion once
         * we've successfully sent any encrypted packets.  However, that can cause
         * problems for callers; notably, pqPutMsgEnd's heuristic to send only
         * full 8K blocks interacts badly with such a hack.  We won't save much,
         * typically, by letting callers discard data early, so don't risk it.
         */
        if (len < PqGSSSendConsumed)
        {
                appendPQExpBufferStr(&conn->errorMessage,
                                                         "GSSAPI caller failed to retransmit all data needing to be retried\n");
                errno = EINVAL;
                return -1;
        }

        /* Discount whatever source data we already encrypted. */
        bytes_to_encrypt = len - PqGSSSendConsumed;
        bytes_encrypted = PqGSSSendConsumed;

        /*
         * Loop through encrypting data and sending it out until it's all done or
         * pqsecure_raw_write() complains (which would likely mean that the socket
         * is non-blocking and the requested send() would block, or there was some
         * kind of actual error).
         */
        while (bytes_to_encrypt || PqGSSSendLength)
        {
                int                     conf_state = 0;
                uint32          netlen;

                /*
                 * Check if we have data in the encrypted output buffer that needs to
                 * be sent (possibly left over from a previous call), and if so, try
                 * to send it.  If we aren't able to, return that fact back up to the
                 * caller.
                 */
                if (PqGSSSendLength)
                {
                        ssize_t         retval;
                        ssize_t         amount = PqGSSSendLength - PqGSSSendNext;

                        retval = pqsecure_raw_write(conn, PqGSSSendBuffer + PqGSSSendNext, amount);
                        if (retval <= 0)
                                return retval;

                        /*
                         * Check if this was a partial write, and if so, move forward that
                         * far in our buffer and try again.
                         */
                        if (retval < amount)
                        {
                                PqGSSSendNext += retval;
                                continue;
                        }

                        /* We've successfully sent whatever data was in the buffer. */
                        PqGSSSendLength = PqGSSSendNext = 0;
                }

                /*
                 * Check if there are any bytes left to encrypt.  If not, we're done.
                 */
                if (!bytes_to_encrypt)
                        break;

                /*
                 * Check how much we are being asked to send, if it's too much, then
                 * we will have to loop and possibly be called multiple times to get
                 * through all the data.
                 */
                if (bytes_to_encrypt > PqGSSMaxPktSize)
                        input.length = PqGSSMaxPktSize;
                else
                        input.length = bytes_to_encrypt;

                input.value = (char *) ptr + bytes_encrypted;

                output.value = NULL;
                output.length = 0;

                /*
                 * Create the next encrypted packet.  Any failure here is considered a
                 * hard failure, so we return -1 even if some data has been sent.
                 */
                major = gss_wrap(&minor, gctx, 1, GSS_C_QOP_DEFAULT,
                                                 &input, &conf_state, &output);
                if (major != GSS_S_COMPLETE)
                {
                        pg_GSS_error(libpq_gettext("GSSAPI wrap error"), conn, major, minor);
                        errno = EIO;            /* for lack of a better idea */
                        goto cleanup;
                }

                if (conf_state == 0)
                {
                        libpq_append_conn_error(conn, "outgoing GSSAPI message would not use confidentiality");
                        errno = EIO;            /* for lack of a better idea */
                        goto cleanup;
                }

                if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
                {
                        libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
                                                                        (size_t) output.length,
                                                                        PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
                        errno = EIO;            /* for lack of a better idea */
                        goto cleanup;
                }

                bytes_encrypted += input.length;
                bytes_to_encrypt -= input.length;
                PqGSSSendConsumed += input.length;

                /* 4 network-order bytes of length, then payload */
                netlen = pg_hton32(output.length);
                memcpy(PqGSSSendBuffer + PqGSSSendLength, &netlen, sizeof(uint32));
                PqGSSSendLength += sizeof(uint32);

                memcpy(PqGSSSendBuffer + PqGSSSendLength, output.value, output.length);
                PqGSSSendLength += output.length;

                /* Release buffer storage allocated by GSSAPI */
                gss_release_buffer(&minor, &output);
        }

        /* If we get here, our counters should all match up. */
        Assert(len == PqGSSSendConsumed);
        Assert(len == bytes_encrypted);

        /* We're reporting all the data as sent, so reset PqGSSSendConsumed. */
        PqGSSSendConsumed = 0;

        ret = bytes_encrypted;

cleanup:
        /* Release GSSAPI buffer storage, if we didn't already */
        if (output.value != NULL)
                gss_release_buffer(&minor, &output);
        return ret;
}

/*
 * Read up to len bytes of data into ptr from a GSSAPI-encrypted connection.
 *
 * The connection must be already set up for GSSAPI encryption (i.e., GSSAPI
 * transport negotiation is complete).
 *
 * Returns the number of data bytes read, or on failure, returns -1
 * with errno set appropriately.  If the errno indicates a non-retryable
 * error, a message is added to conn->errorMessage.  For retryable errors,
 * caller should call again once the socket is ready.
 */
ssize_t
pg_GSS_read(PGconn *conn, void *ptr, size_t len)
{
        OM_uint32       major,
                                minor;
        gss_buffer_desc input = GSS_C_EMPTY_BUFFER,
                                output = GSS_C_EMPTY_BUFFER;
        ssize_t         ret;
        size_t          bytes_returned = 0;
        gss_ctx_id_t gctx = conn->gctx;

        /*
         * The plan here is to read one incoming encrypted packet into
         * PqGSSRecvBuffer, decrypt it into PqGSSResultBuffer, and then dole out
         * data from there to the caller.  When we exhaust the current input
         * packet, read another.
         */
        while (bytes_returned < len)
        {
                int                     conf_state = 0;

                /* Check if we have data in our buffer that we can return immediately */
                if (PqGSSResultNext < PqGSSResultLength)
                {
                        size_t          bytes_in_buffer = PqGSSResultLength - PqGSSResultNext;
                        size_t          bytes_to_copy = Min(bytes_in_buffer, len - bytes_returned);

                        /*
                         * Copy the data from our result buffer into the caller's buffer,
                         * at the point where we last left off filling their buffer.
                         */
                        memcpy((char *) ptr + bytes_returned, PqGSSResultBuffer + PqGSSResultNext, bytes_to_copy);
                        PqGSSResultNext += bytes_to_copy;
                        bytes_returned += bytes_to_copy;

                        /*
                         * At this point, we've either filled the caller's buffer or
                         * emptied our result buffer.  Either way, return to caller.  In
                         * the second case, we could try to read another encrypted packet,
                         * but the odds are good that there isn't one available.  (If this
                         * isn't true, we chose too small a max packet size.)  In any
                         * case, there's no harm letting the caller process the data we've
                         * already returned.
                         */
                        break;
                }

                /* Result buffer is empty, so reset buffer pointers */
                PqGSSResultLength = PqGSSResultNext = 0;

                /*
                 * Because we chose above to return immediately as soon as we emit
                 * some data, bytes_returned must be zero at this point.  Therefore
                 * the failure exits below can just return -1 without worrying about
                 * whether we already emitted some data.
                 */
                Assert(bytes_returned == 0);

                /*
                 * At this point, our result buffer is empty with more bytes being
                 * requested to be read.  We are now ready to load the next packet and
                 * decrypt it (entirely) into our result buffer.
                 */

                /* Collect the length if we haven't already */
                if (PqGSSRecvLength < sizeof(uint32))
                {
                        ret = pqsecure_raw_read(conn, PqGSSRecvBuffer + PqGSSRecvLength,
                                                                        sizeof(uint32) - PqGSSRecvLength);

                        /* If ret <= 0, pqsecure_raw_read already set the correct errno */
                        if (ret <= 0)
                                return ret;

                        PqGSSRecvLength += ret;

                        /* If we still haven't got the length, return to the caller */
                        if (PqGSSRecvLength < sizeof(uint32))
                        {
                                errno = EWOULDBLOCK;
                                return -1;
                        }
                }

                /* Decode the packet length and check for overlength packet */
                input.length = pg_ntoh32(*(uint32 *) PqGSSRecvBuffer);

                if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
                {
                        libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
                                                                        (size_t) input.length,
                                                                        PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
                        errno = EIO;            /* for lack of a better idea */
                        return -1;
                }

                /*
                 * Read as much of the packet as we are able to on this call into
                 * wherever we left off from the last time we were called.
                 */
                ret = pqsecure_raw_read(conn, PqGSSRecvBuffer + PqGSSRecvLength,
                                                                input.length - (PqGSSRecvLength - sizeof(uint32)));
                /* If ret <= 0, pqsecure_raw_read already set the correct errno */
                if (ret <= 0)
                        return ret;

                PqGSSRecvLength += ret;

                /* If we don't yet have the whole packet, return to the caller */
                if (PqGSSRecvLength - sizeof(uint32) < input.length)
                {
                        errno = EWOULDBLOCK;
                        return -1;
                }

                /*
                 * We now have the full packet and we can perform the decryption and
                 * refill our result buffer, then loop back up to pass data back to
                 * the caller.  Note that error exits below here must take care of
                 * releasing the gss output buffer.
                 */
                output.value = NULL;
                output.length = 0;
                input.value = PqGSSRecvBuffer + sizeof(uint32);

                major = gss_unwrap(&minor, gctx, &input, &output, &conf_state, NULL);
                if (major != GSS_S_COMPLETE)
                {
                        pg_GSS_error(libpq_gettext("GSSAPI unwrap error"), conn,
                                                 major, minor);
                        ret = -1;
                        errno = EIO;            /* for lack of a better idea */
                        goto cleanup;
                }

                if (conf_state == 0)
                {
                        libpq_append_conn_error(conn, "incoming GSSAPI message did not use confidentiality");
                        ret = -1;
                        errno = EIO;            /* for lack of a better idea */
                        goto cleanup;
                }

                memcpy(PqGSSResultBuffer, output.value, output.length);
                PqGSSResultLength = output.length;

                /* Our receive buffer is now empty, reset it */
                PqGSSRecvLength = 0;

                /* Release buffer storage allocated by GSSAPI */
                gss_release_buffer(&minor, &output);
        }

        ret = bytes_returned;

cleanup:
        /* Release GSSAPI buffer storage, if we didn't already */
        if (output.value != NULL)
                gss_release_buffer(&minor, &output);
        return ret;
}

/*
 * Simple wrapper for reading from pqsecure_raw_read.
 *
 * This takes the same arguments as pqsecure_raw_read, plus an output parameter
 * to return the number of bytes read.  This handles if blocking would occur and
 * if we detect EOF on the connection.
 */
static PostgresPollingStatusType
gss_read(PGconn *conn, void *recv_buffer, size_t length, ssize_t *ret)
{
        *ret = pqsecure_raw_read(conn, recv_buffer, length);
        if (*ret < 0)
        {
                if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)
                        return PGRES_POLLING_READING;
                else
                        return PGRES_POLLING_FAILED;
        }

        /* Check for EOF */
        if (*ret == 0)
        {
                int                     result = pqReadReady(conn);

                if (result < 0)
                        return PGRES_POLLING_FAILED;

                if (!result)
                        return PGRES_POLLING_READING;

                *ret = pqsecure_raw_read(conn, recv_buffer, length);
                if (*ret < 0)
                {
                        if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)
                                return PGRES_POLLING_READING;
                        else
                                return PGRES_POLLING_FAILED;
                }
                if (*ret == 0)
                        return PGRES_POLLING_FAILED;
        }

        return PGRES_POLLING_OK;
}

/*
 * Negotiate GSSAPI transport for a connection.  When complete, returns
 * PGRES_POLLING_OK.  Will return PGRES_POLLING_READING or
 * PGRES_POLLING_WRITING as appropriate whenever it would block, and
 * PGRES_POLLING_FAILED if transport could not be negotiated.
 */
PostgresPollingStatusType
pqsecure_open_gss(PGconn *conn)
{
        ssize_t         ret;
        OM_uint32       major,
                                minor,
                                gss_flags = GSS_REQUIRED_FLAGS;
        uint32          netlen;
        PostgresPollingStatusType result;
        gss_buffer_desc input = GSS_C_EMPTY_BUFFER,
                                output = GSS_C_EMPTY_BUFFER;

        /*
         * If first time through for this connection, allocate buffers and
         * initialize state variables.  By malloc'ing the buffers separately, we
         * ensure that they are sufficiently aligned for the length-word accesses
         * that we do in some places in this file.
         */
        if (PqGSSSendBuffer == NULL)
        {
                PqGSSSendBuffer = malloc(PQ_GSS_SEND_BUFFER_SIZE);
                PqGSSRecvBuffer = malloc(PQ_GSS_RECV_BUFFER_SIZE);
                PqGSSResultBuffer = malloc(PQ_GSS_RECV_BUFFER_SIZE);
                if (!PqGSSSendBuffer || !PqGSSRecvBuffer || !PqGSSResultBuffer)
                {
                        libpq_append_conn_error(conn, "out of memory");
                        return PGRES_POLLING_FAILED;
                }
                PqGSSSendLength = PqGSSSendNext = PqGSSSendConsumed = 0;
                PqGSSRecvLength = PqGSSResultLength = PqGSSResultNext = 0;
        }

        /*
         * Check if we have anything to send from a prior call and if so, send it.
         */
        if (PqGSSSendLength)
        {
                ssize_t         amount = PqGSSSendLength - PqGSSSendNext;

                ret = pqsecure_raw_write(conn, PqGSSSendBuffer + PqGSSSendNext, amount);
                if (ret < 0)
                {
                        if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)
                                return PGRES_POLLING_WRITING;
                        else
                                return PGRES_POLLING_FAILED;
                }

                if (ret < amount)
                {
                        PqGSSSendNext += ret;
                        return PGRES_POLLING_WRITING;
                }

                PqGSSSendLength = PqGSSSendNext = 0;
        }

        /*
         * Client sends first, and sending creates a context, therefore this will
         * be false the first time through, and then when we get called again we
         * will check for incoming data.
         */
        if (conn->gctx)
        {
                /* Process any incoming data we might have */

                /* See if we are still trying to get the length */
                if (PqGSSRecvLength < sizeof(uint32))
                {
                        /* Attempt to get the length first */
                        result = gss_read(conn, PqGSSRecvBuffer + PqGSSRecvLength, sizeof(uint32) - PqGSSRecvLength, &ret);
                        if (result != PGRES_POLLING_OK)
                                return result;

                        PqGSSRecvLength += ret;

                        if (PqGSSRecvLength < sizeof(uint32))
                                return PGRES_POLLING_READING;
                }

                /*
                 * Check if we got an error packet
                 *
                 * This is safe to do because we shouldn't ever get a packet over 8192
                 * and therefore the actual length bytes, being that they are in
                 * network byte order, for any real packet will start with two zero
                 * bytes.
                 */
                if (PqGSSRecvBuffer[0] == 'E')
                {
                        /*
                         * For an error packet during startup, we don't get a length, so
                         * simply read as much as we can fit into our buffer (as a string,
                         * so leave a spot at the end for a NULL byte too) and report that
                         * back to the caller.
                         */
                        result = gss_read(conn, PqGSSRecvBuffer + PqGSSRecvLength, PQ_GSS_RECV_BUFFER_SIZE - PqGSSRecvLength - 1, &ret);
                        if (result != PGRES_POLLING_OK)
                                return result;

                        PqGSSRecvLength += ret;

                        Assert(PqGSSRecvLength < PQ_GSS_RECV_BUFFER_SIZE);
                        PqGSSRecvBuffer[PqGSSRecvLength] = '\0';
                        appendPQExpBuffer(&conn->errorMessage, "%s\n", PqGSSRecvBuffer + 1);

                        return PGRES_POLLING_FAILED;
                }

                /*
                 * We should have the whole length at this point, so pull it out and
                 * then read whatever we have left of the packet
                 */

                /* Get the length and check for over-length packet */
                input.length = pg_ntoh32(*(uint32 *) PqGSSRecvBuffer);
                if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
                {
                        libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
                                                                        (size_t) input.length,
                                                                        PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
                        return PGRES_POLLING_FAILED;
                }

                /*
                 * Read as much of the packet as we are able to on this call into
                 * wherever we left off from the last time we were called.
                 */
                result = gss_read(conn, PqGSSRecvBuffer + PqGSSRecvLength,
                                                  input.length - (PqGSSRecvLength - sizeof(uint32)), &ret);
                if (result != PGRES_POLLING_OK)
                        return result;

                PqGSSRecvLength += ret;

                /*
                 * If we got less than the rest of the packet then we need to return
                 * and be called again.
                 */
                if (PqGSSRecvLength - sizeof(uint32) < input.length)
                        return PGRES_POLLING_READING;

                input.value = PqGSSRecvBuffer + sizeof(uint32);
        }

        /* Load the service name (no-op if already done */
        ret = pg_GSS_load_servicename(conn);
        if (ret != STATUS_OK)
                return PGRES_POLLING_FAILED;

        if (conn->gssdelegation && conn->gssdelegation[0] == '1')
        {
                /* Acquire credentials if possible */
                if (conn->gcred == GSS_C_NO_CREDENTIAL)
                        (void) pg_GSS_have_cred_cache(&conn->gcred);

                /*
                 * We have credentials and gssdelegation is enabled, so request
                 * credential delegation.  This may or may not actually result in
                 * credentials being delegated- it depends on if the forwardable flag
                 * has been set in the credential and if the server is configured to
                 * accept delegated credentials.
                 */
                if (conn->gcred != GSS_C_NO_CREDENTIAL)
                        gss_flags |= GSS_C_DELEG_FLAG;
        }

        /*
         * Call GSS init context, either with an empty input, or with a complete
         * packet from the server.
         */
        major = gss_init_sec_context(&minor, conn->gcred, &conn->gctx,
                                                                 conn->gtarg_nam, GSS_C_NO_OID,
                                                                 gss_flags, 0, 0, &input, NULL,
                                                                 &output, NULL, NULL);

        /* GSS Init Sec Context uses the whole packet, so clear it */
        PqGSSRecvLength = 0;

        if (GSS_ERROR(major))
        {
                pg_GSS_error(libpq_gettext("could not initiate GSSAPI security context"),
                                         conn, major, minor);
                return PGRES_POLLING_FAILED;
        }

        if (output.length == 0)
        {
                /*
                 * We're done - hooray!  Set flag to tell the low-level I/O routines
                 * to do GSS wrapping/unwrapping.
                 */
                conn->gssenc = true;
                conn->gssapi_used = true;

                /* Clean up */
                gss_release_cred(&minor, &conn->gcred);
                conn->gcred = GSS_C_NO_CREDENTIAL;
                gss_release_buffer(&minor, &output);

                /*
                 * Determine the max packet size which will fit in our buffer, after
                 * accounting for the length.  pg_GSS_write will need this.
                 */
                major = gss_wrap_size_limit(&minor, conn->gctx, 1, GSS_C_QOP_DEFAULT,
                                                                        PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32),
                                                                        &PqGSSMaxPktSize);

                if (GSS_ERROR(major))
                {
                        pg_GSS_error(libpq_gettext("GSSAPI size check error"), conn,
                                                 major, minor);
                        return PGRES_POLLING_FAILED;
                }

                return PGRES_POLLING_OK;
        }

        /* Must have output.length > 0 */
        if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
        {
                pg_GSS_error(libpq_gettext("GSSAPI context establishment error"),
                                         conn, major, minor);
                gss_release_buffer(&minor, &output);
                return PGRES_POLLING_FAILED;
        }

        /* Queue the token for writing */
        netlen = pg_hton32(output.length);

        memcpy(PqGSSSendBuffer, (char *) &netlen, sizeof(uint32));
        PqGSSSendLength += sizeof(uint32);

        memcpy(PqGSSSendBuffer + PqGSSSendLength, output.value, output.length);
        PqGSSSendLength += output.length;

        /* We don't bother with PqGSSSendConsumed here */

        /* Release buffer storage allocated by GSSAPI */
        gss_release_buffer(&minor, &output);

        /* Ask to be called again to write data */
        return PGRES_POLLING_WRITING;
}

/*
 * GSSAPI Information functions.
 */

/*
 * Return the GSSAPI Context itself.
 */
void *
PQgetgssctx(PGconn *conn)
{
        if (!conn)
                return NULL;

        return conn->gctx;
}

/*
 * Return true if GSSAPI encryption is in use.
 */
int
PQgssEncInUse(PGconn *conn)
{
        if (!conn || !conn->gctx)
                return 0;

        return conn->gssenc;
}