#include "postgres.h"
#include <unistd.h>
#include "libpq/auth.h"
#include "libpq/be-gssapi-common.h"
#include "libpq/libpq.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "port/pg_bswap.h"
#include "utils/injection_point.h"
#include "utils/memutils.h"

Include dependency graph for be-secure-gssapi.c:

Macros
#define	PQ_GSS_SEND_BUFFER_SIZE 16384

#define	PQ_GSS_RECV_BUFFER_SIZE 16384

Functions
ssize_t	be_gssapi_write (Port port, const void ptr, size_t len)

ssize_t	be_gssapi_read (Port port, void ptr, size_t len)

static ssize_t	read_or_wait (Port *port, ssize_t len)

ssize_t	secure_open_gssapi (Port *port)

bool	be_gssapi_get_auth (Port *port)

bool	be_gssapi_get_enc (Port *port)

const char *	be_gssapi_get_princ (Port *port)

bool	be_gssapi_get_delegation (Port *port)

Variables
static char *	PqGSSSendBuffer

static int	PqGSSSendLength

static int	PqGSSSendNext

static int	PqGSSSendConsumed

static char *	PqGSSRecvBuffer

static int	PqGSSRecvLength

static char *	PqGSSResultBuffer

static int	PqGSSResultLength

static int	PqGSSResultNext

static uint32	PqGSSMaxPktSize

Macro Definition Documentation

◆ PQ_GSS_RECV_BUFFER_SIZE

#define PQ_GSS_RECV_BUFFER_SIZE 16384

Definition at line 53 of file be-secure-gssapi.c.

◆ PQ_GSS_SEND_BUFFER_SIZE

#define PQ_GSS_SEND_BUFFER_SIZE 16384

Definition at line 52 of file be-secure-gssapi.c.

Function Documentation

◆ be_gssapi_get_auth()

bool be_gssapi_get_auth ( Port * port )

Definition at line 717 of file be-secure-gssapi.c.

{
    if (!port || !port->gss)
        return false;
 
    return port->gss->auth;
}

References port.

Referenced by PerformAuthentication(), and pgstat_bestart_security().

◆ be_gssapi_get_delegation()

bool be_gssapi_get_delegation ( Port * port )

Definition at line 755 of file be-secure-gssapi.c.

{
    if (!port || !port->gss)
        return false;
 
    return port->gss->delegated_creds;
}

References port.

Referenced by check_conn_params(), dblink_connstr_check(), dblink_security_check(), PerformAuthentication(), pgfdw_security_check(), and pgstat_bestart_security().

◆ be_gssapi_get_enc()

bool be_gssapi_get_enc ( Port * port )

Definition at line 729 of file be-secure-gssapi.c.

{
    if (!port || !port->gss)
        return false;
 
    return port->gss->enc;
}

References port.

Referenced by PerformAuthentication(), and pgstat_bestart_security().

◆ be_gssapi_get_princ()

const char * be_gssapi_get_princ ( Port * port )

Definition at line 742 of file be-secure-gssapi.c.

{
    if (!port || !port->gss)
        return NULL;
 
    return port->gss->princ;
}

References port.

Referenced by PerformAuthentication(), and pgstat_bestart_security().

◆ be_gssapi_read()

ssize_t be_gssapi_read	(	Port *	port,
		void *	ptr,
		size_t	len
	)

Definition at line 263 of file be-secure-gssapi.c.

{
    OM_uint32   major,
                minor;
    gss_buffer_desc input,
                output;
    ssize_t     ret;
    size_t      bytes_returned = 0;
    gss_ctx_id_t gctx = port->gss->ctx;
 
    /*
     * 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 = secure_raw_read(port, PqGSSRecvBuffer + PqGSSRecvLength,
                                  sizeof(uint32) - PqGSSRecvLength);
 
            /* If ret <= 0, secure_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))
        {
            ereport(COMMERROR,
                    (errmsg("oversize GSSAPI packet sent by the client (%zu > %zu)",
                            (size_t) input.length,
                            PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))));
            errno = ECONNRESET;
            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 = secure_raw_read(port, PqGSSRecvBuffer + PqGSSRecvLength,
                              input.length - (PqGSSRecvLength - sizeof(uint32)));
        /* If ret <= 0, secure_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.
         */
        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(_("GSSAPI unwrap error"), major, minor);
            errno = ECONNRESET;
            return -1;
        }
        if (conf_state == 0)
        {
            ereport(COMMERROR,
                    (errmsg("incoming GSSAPI message did not use confidentiality")));
            errno = ECONNRESET;
            return -1;
        }
 
        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);
    }
 
    return bytes_returned;
}

References _, Assert(), COMMERROR, ECONNRESET, ereport, errmsg(), EWOULDBLOCK, input, len, Min, output, pg_GSS_error(), pg_ntoh32, port, PQ_GSS_RECV_BUFFER_SIZE, PqGSSRecvBuffer, PqGSSRecvLength, PqGSSResultBuffer, PqGSSResultLength, PqGSSResultNext, and secure_raw_read().

Referenced by secure_read().

◆ be_gssapi_write()

ssize_t be_gssapi_write	(	Port *	port,
		const void *	ptr,
		size_t	len
	)

Definition at line 96 of file be-secure-gssapi.c.

{
    OM_uint32   major,
                minor;
    gss_buffer_desc input,
                output;
    size_t      bytes_to_encrypt;
    size_t      bytes_encrypted;
    gss_ctx_id_t gctx = port->gss->ctx;
 
    /*
     * 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)
    {
        elog(COMMERROR, "GSSAPI caller failed to retransmit all data needing to be retried");
        errno = ECONNRESET;
        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
     * secure_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     ret;
            ssize_t     amount = PqGSSSendLength - PqGSSSendNext;
 
            ret = secure_raw_write(port, PqGSSSendBuffer + PqGSSSendNext, amount);
            if (ret <= 0)
                return ret;
 
            /*
             * Check if this was a partial write, and if so, move forward that
             * far in our buffer and try again.
             */
            if (ret < amount)
            {
                PqGSSSendNext += ret;
                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(_("GSSAPI wrap error"), major, minor);
            errno = ECONNRESET;
            return -1;
        }
        if (conf_state == 0)
        {
            ereport(COMMERROR,
                    (errmsg("outgoing GSSAPI message would not use confidentiality")));
            errno = ECONNRESET;
            return -1;
        }
        if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
        {
            ereport(COMMERROR,
                    (errmsg("server tried to send oversize GSSAPI packet (%zu > %zu)",
                            (size_t) output.length,
                            PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))));
            errno = ECONNRESET;
            return -1;
        }
 
        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;
 
    return bytes_encrypted;
}

References _, Assert(), COMMERROR, ECONNRESET, elog, ereport, errmsg(), input, len, output, pg_GSS_error(), pg_hton32, port, PQ_GSS_SEND_BUFFER_SIZE, PqGSSMaxPktSize, PqGSSSendBuffer, PqGSSSendConsumed, PqGSSSendLength, PqGSSSendNext, and secure_raw_write().

Referenced by secure_write().

◆ read_or_wait()

static ssize_t read_or_wait	(	Port *	port,
		ssize_t	len
	)

static

Definition at line 424 of file be-secure-gssapi.c.

{
    ssize_t     ret;
 
    /*
     * Keep going until we either read in everything we were asked to, or we
     * error out.
     */
    while (PqGSSRecvLength < len)
    {
        ret = secure_raw_read(port, PqGSSRecvBuffer + PqGSSRecvLength, len - PqGSSRecvLength);
 
        /*
         * If we got back an error and it wasn't just
         * EWOULDBLOCK/EAGAIN/EINTR, then give up.
         */
        if (ret < 0 &&
            !(errno == EWOULDBLOCK || errno == EAGAIN || errno == EINTR))
            return -1;
 
        /*
         * Ok, we got back either a positive value, zero, or a negative result
         * indicating we should retry.
         *
         * If it was zero or negative, then we wait on the socket to be
         * readable again.
         */
        if (ret <= 0)
        {
            WaitLatchOrSocket(NULL,
                              WL_SOCKET_READABLE | WL_EXIT_ON_PM_DEATH,
                              port->sock, 0, WAIT_EVENT_GSS_OPEN_SERVER);
 
            /*
             * If we got back zero bytes, and then waited on the socket to be
             * readable and got back zero bytes on a second read, then this is
             * EOF and the client hung up on us.
             *
             * If we did get data here, then we can just fall through and
             * handle it just as if we got data the first time.
             *
             * Otherwise loop back to the top and try again.
             */
            if (ret == 0)
            {
                ret = secure_raw_read(port, PqGSSRecvBuffer + PqGSSRecvLength, len - PqGSSRecvLength);
                if (ret == 0)
                    return -1;
            }
            if (ret < 0)
                continue;
        }
 
        PqGSSRecvLength += ret;
    }
 
    return len;
}

References EAGAIN, EINTR, EWOULDBLOCK, len, port, PqGSSRecvBuffer, PqGSSRecvLength, secure_raw_read(), WaitLatchOrSocket(), WL_EXIT_ON_PM_DEATH, and WL_SOCKET_READABLE.

Referenced by secure_open_gssapi().

◆ secure_open_gssapi()

ssize_t secure_open_gssapi ( Port * port )

Definition at line 496 of file be-secure-gssapi.c.

{
    bool        complete_next = false;
    OM_uint32   major,
                minor;
    gss_cred_id_t delegated_creds;
 
    INJECTION_POINT("backend-gssapi-startup", NULL);
 
    /*
     * Allocate subsidiary Port data for GSSAPI operations.
     */
    port->gss = (pg_gssinfo *)
        MemoryContextAllocZero(TopMemoryContext, sizeof(pg_gssinfo));
 
    delegated_creds = GSS_C_NO_CREDENTIAL;
    port->gss->delegated_creds = false;
 
    /*
     * Allocate buffers and initialize state variables.  By malloc'ing the
     * buffers at this point, we avoid wasting static data space in processes
     * that will never use them, and we ensure that the buffers are
     * sufficiently aligned for the length-word accesses that we do in some
     * places in this file.
     */
    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)
        ereport(FATAL,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));
    PqGSSSendLength = PqGSSSendNext = PqGSSSendConsumed = 0;
    PqGSSRecvLength = PqGSSResultLength = PqGSSResultNext = 0;
 
    /*
     * Use the configured keytab, if there is one.  As we now require MIT
     * Kerberos, we might consider using the credential store extensions in
     * the future instead of the environment variable.
     */
    if (pg_krb_server_keyfile != NULL && pg_krb_server_keyfile[0] != '\0')
    {
        if (setenv("KRB5_KTNAME", pg_krb_server_keyfile, 1) != 0)
        {
            /* The only likely failure cause is OOM, so use that errcode */
            ereport(FATAL,
                    (errcode(ERRCODE_OUT_OF_MEMORY),
                     errmsg("could not set environment: %m")));
        }
    }
 
    while (true)
    {
        ssize_t     ret;
        gss_buffer_desc input,
                    output = GSS_C_EMPTY_BUFFER;
 
        /*
         * The client always sends first, so try to go ahead and read the
         * length and wait on the socket to be readable again if that fails.
         */
        ret = read_or_wait(port, sizeof(uint32));
        if (ret < 0)
            return ret;
 
        /*
         * Get the length for this packet from the length header.
         */
        input.length = pg_ntoh32(*(uint32 *) PqGSSRecvBuffer);
 
        /* Done with the length, reset our buffer */
        PqGSSRecvLength = 0;
 
        /*
         * During initialization, packets are always fully consumed and
         * shouldn't ever be over PQ_GSS_RECV_BUFFER_SIZE in length.
         *
         * Verify on our side that the client doesn't do something funny.
         */
        if (input.length > PQ_GSS_RECV_BUFFER_SIZE)
        {
            ereport(COMMERROR,
                    (errmsg("oversize GSSAPI packet sent by the client (%zu > %d)",
                            (size_t) input.length,
                            PQ_GSS_RECV_BUFFER_SIZE)));
            return -1;
        }
 
        /*
         * Get the rest of the packet so we can pass it to GSSAPI to accept
         * the context.
         */
        ret = read_or_wait(port, input.length);
        if (ret < 0)
            return ret;
 
        input.value = PqGSSRecvBuffer;
 
        /* Process incoming data.  (The client sends first.) */
        major = gss_accept_sec_context(&minor, &port->gss->ctx,
                                       GSS_C_NO_CREDENTIAL, &input,
                                       GSS_C_NO_CHANNEL_BINDINGS,
                                       &port->gss->name, NULL, &output, NULL,
                                       NULL, pg_gss_accept_delegation ? &delegated_creds : NULL);
 
        if (GSS_ERROR(major))
        {
            pg_GSS_error(_("could not accept GSSAPI security context"),
                         major, minor);
            gss_release_buffer(&minor, &output);
            return -1;
        }
        else if (!(major & GSS_S_CONTINUE_NEEDED))
        {
            /*
             * rfc2744 technically permits context negotiation to be complete
             * both with and without a packet to be sent.
             */
            complete_next = true;
        }
 
        if (delegated_creds != GSS_C_NO_CREDENTIAL)
        {
            pg_store_delegated_credential(delegated_creds);
            port->gss->delegated_creds = true;
        }
 
        /* Done handling the incoming packet, reset our buffer */
        PqGSSRecvLength = 0;
 
        /*
         * Check if we have data to send and, if we do, make sure to send it
         * all
         */
        if (output.length > 0)
        {
            uint32      netlen = pg_hton32(output.length);
 
            if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
            {
                ereport(COMMERROR,
                        (errmsg("server tried to send oversize GSSAPI packet (%zu > %zu)",
                                (size_t) output.length,
                                PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))));
                gss_release_buffer(&minor, &output);
                return -1;
            }
 
            memcpy(PqGSSSendBuffer, &netlen, sizeof(uint32));
            PqGSSSendLength += sizeof(uint32);
 
            memcpy(PqGSSSendBuffer + PqGSSSendLength, output.value, output.length);
            PqGSSSendLength += output.length;
 
            /* we don't bother with PqGSSSendConsumed here */
 
            while (PqGSSSendNext < PqGSSSendLength)
            {
                ret = secure_raw_write(port, PqGSSSendBuffer + PqGSSSendNext,
                                       PqGSSSendLength - PqGSSSendNext);
 
                /*
                 * If we got back an error and it wasn't just
                 * EWOULDBLOCK/EAGAIN/EINTR, then give up.
                 */
                if (ret < 0 &&
                    !(errno == EWOULDBLOCK || errno == EAGAIN || errno == EINTR))
                {
                    gss_release_buffer(&minor, &output);
                    return -1;
                }
 
                /* Wait and retry if we couldn't write yet */
                if (ret <= 0)
                {
                    WaitLatchOrSocket(NULL,
                                      WL_SOCKET_WRITEABLE | WL_EXIT_ON_PM_DEATH,
                                      port->sock, 0, WAIT_EVENT_GSS_OPEN_SERVER);
                    continue;
                }
 
                PqGSSSendNext += ret;
            }
 
            /* Done sending the packet, reset our buffer */
            PqGSSSendLength = PqGSSSendNext = 0;
 
            gss_release_buffer(&minor, &output);
        }
 
        /*
         * If we got back that the connection is finished being set up, now
         * that we've sent the last packet, exit our loop.
         */
        if (complete_next)
            break;
    }
 
    /*
     * Determine the max packet size which will fit in our buffer, after
     * accounting for the length.  be_gssapi_write will need this.
     */
    major = gss_wrap_size_limit(&minor, port->gss->ctx, 1, GSS_C_QOP_DEFAULT,
                                PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32),
                                &PqGSSMaxPktSize);
 
    if (GSS_ERROR(major))
    {
        pg_GSS_error(_("GSSAPI size check error"), major, minor);
        return -1;
    }
 
    port->gss->enc = true;
 
    return 0;
}