File: red-stream.c

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/* -*- Mode: C; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
   Copyright (C) 2009, 2013 Red Hat, Inc.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   This library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>

#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#ifndef _WIN32
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/tcp.h>
#else
#include <ws2tcpip.h>
#endif

#include <glib.h>

#include <openssl/err.h>

#include <common/log.h>

#include "main-dispatcher.h"
#include "net-utils.h"
#include "red-common.h"
#include "red-stream.h"
#include "reds.h"
#include "websocket.h"

// compatibility for *BSD systems
#if !defined(TCP_CORK) && !defined(_WIN32)
#define TCP_CORK TCP_NOPUSH
#endif

struct AsyncRead {
    void *opaque;
    uint8_t *now;
    uint8_t *end;
    AsyncReadDone done;
    AsyncReadError error;
};
typedef struct AsyncRead AsyncRead;

#if HAVE_SASL
#include <sasl/sasl.h>

typedef struct RedSASL {
    sasl_conn_t *conn;

    /* If we want to negotiate an SSF layer with client */
    int wantSSF :1;
    /* If we are now running the SSF layer */
    int runSSF :1;

    /*
     * Buffering encoded data to allow more clear data
     * to be stuffed onto the output buffer
     */
    const uint8_t *encoded;
    unsigned int encodedLength;
    unsigned int encodedOffset;

    SpiceBuffer inbuffer;
} RedSASL;
#endif

struct RedStreamPrivate {
    SSL *ssl;

#if HAVE_SASL
    RedSASL sasl;
#endif

    AsyncRead async_read;

    RedsWebSocket *ws;

    /* life time of info:
     * allocated when creating RedStream.
     * deallocated when main_dispatcher handles the SPICE_CHANNEL_EVENT_DISCONNECTED
     * event, either from same thread or by call back from main thread. */
    SpiceChannelEventInfo* info;
    bool use_cork;
    bool corked;

    ssize_t (*read)(RedStream *s, void *buf, size_t nbyte);
    ssize_t (*write)(RedStream *s, const void *buf, size_t nbyte);
    ssize_t (*writev)(RedStream *s, const struct iovec *iov, int iovcnt);

    RedsState *reds;
    SpiceCoreInterfaceInternal *core;
};

#ifndef _WIN32
/**
 * Set TCP_CORK on socket
 */
/* NOTE: enabled must be int */
static int socket_set_cork(int socket, int enabled)
{
    SPICE_VERIFY(sizeof(enabled) == sizeof(int));
    return setsockopt(socket, IPPROTO_TCP, TCP_CORK, &enabled, sizeof(enabled));
}
#else
static inline int socket_set_cork(int socket, int enabled)
{
    return -1;
}
#endif

static ssize_t stream_write_cb(RedStream *s, const void *buf, size_t size)
{
    return socket_write(s->socket, buf, size);
}

static ssize_t stream_writev_cb(RedStream *s, const struct iovec *iov, int iovcnt)
{
    ssize_t ret = 0;
    do {
        int tosend;
        ssize_t n, expected = 0;
        int i;
#ifdef IOV_MAX
        tosend = MIN(iovcnt, IOV_MAX);
#else
        tosend = iovcnt;
#endif
        for (i = 0; i < tosend; i++) {
            expected += iov[i].iov_len;
        }
        n = socket_writev(s->socket, iov, tosend);
        if (n <= expected) {
            if (n > 0)
                ret += n;
            return ret == 0 ? n : ret;
        }
        ret += n;
        iov += tosend;
        iovcnt -= tosend;
    } while(iovcnt > 0);

    return ret;
}

static ssize_t stream_read_cb(RedStream *s, void *buf, size_t size)
{
    return socket_read(s->socket, buf, size);
}

static ssize_t stream_ssl_error(RedStream *s, int return_code)
{
    SPICE_GNUC_UNUSED int ssl_error;

    ssl_error = SSL_get_error(s->priv->ssl, return_code);

    // OpenSSL can to return SSL_ERROR_WANT_READ if we attempt to read
    // data and the socket did not receive all SSL packet.
    // Under Windows errno is not set so potentially caller can detect
    // the wrong error so we need to set errno.
#ifdef _WIN32
    if (ssl_error == SSL_ERROR_WANT_READ || ssl_error == SSL_ERROR_WANT_WRITE) {
        errno = EAGAIN;
    } else {
        errno = EPIPE;
    }
#endif

    // red_peer_receive is expected to receive -1 on errors while
    // OpenSSL documentation just state a <0 value
    return -1;
}

static ssize_t stream_ssl_write_cb(RedStream *s, const void *buf, size_t size)
{
    int return_code;

    return_code = SSL_write(s->priv->ssl, buf, size);

    if (return_code < 0) {
        return stream_ssl_error(s, return_code);
    }

    return return_code;
}

static ssize_t stream_ssl_read_cb(RedStream *s, void *buf, size_t size)
{
    int return_code;

    return_code = SSL_read(s->priv->ssl, buf, size);

    if (return_code < 0) {
        return stream_ssl_error(s, return_code);
    }

    return return_code;
}

void red_stream_remove_watch(RedStream* s)
{
    red_watch_remove(s->watch);
    s->watch = NULL;
}

#if HAVE_SASL
static ssize_t red_stream_sasl_read(RedStream *s, uint8_t *buf, size_t nbyte);
#endif

ssize_t red_stream_read(RedStream *s, void *buf, size_t nbyte)
{
    ssize_t ret;

#if HAVE_SASL
    if (s->priv->sasl.conn && s->priv->sasl.runSSF) {
        ret = red_stream_sasl_read(s, buf, nbyte);
    } else
#endif
        ret = s->priv->read(s, buf, nbyte);

    return ret;
}

bool red_stream_write_all(RedStream *stream, const void *in_buf, size_t n)
{
    const uint8_t *buf = (uint8_t *)in_buf;

    while (n) {
        int now = red_stream_write(stream, buf, n);
        if (now <= 0) {
            if (now == -1 && (errno == EINTR || errno == EAGAIN)) {
                continue;
            }
            return false;
        }
        n -= now;
        buf += now;
    }
    return true;
}

bool red_stream_set_auto_flush(RedStream *s, bool auto_flush)
{
    if (s->priv->use_cork == !auto_flush) {
        return true;
    }

    s->priv->use_cork = !auto_flush;
    if (s->priv->use_cork) {
        if (socket_set_cork(s->socket, 1)) {
            s->priv->use_cork = false;
            return false;
        } else {
            s->priv->corked = true;
        }
    } else if (s->priv->corked) {
        socket_set_cork(s->socket, 0);
        s->priv->corked = false;
    }
    return true;
}

void red_stream_flush(RedStream *s)
{
    if (s->priv->corked) {
        socket_set_cork(s->socket, 0);
        socket_set_cork(s->socket, 1);
    }
}

#if HAVE_SASL
static ssize_t red_stream_sasl_write(RedStream *s, const void *buf, size_t nbyte);
#endif

ssize_t red_stream_write(RedStream *s, const void *buf, size_t nbyte)
{
    ssize_t ret;

#if HAVE_SASL
    if (s->priv->sasl.conn && s->priv->sasl.runSSF) {
        ret = red_stream_sasl_write(s, buf, nbyte);
    } else
#endif
        ret = s->priv->write(s, buf, nbyte);

    return ret;
}

int red_stream_get_family(const RedStream *s)
{
    spice_return_val_if_fail(s != NULL, -1);

    if (s->socket == -1)
        return -1;

    return s->priv->info->laddr_ext.ss_family;
}

bool red_stream_is_plain_unix(const RedStream *s)
{
    spice_return_val_if_fail(s != NULL, false);

    if (red_stream_get_family(s) != AF_UNIX) {
        return false;
    }

#if HAVE_SASL
    if (s->priv->sasl.conn) {
        return false;
    }
#endif
    if (s->priv->ssl) {
        return false;
    }

    return true;

}

/**
 * red_stream_set_no_delay:
 * @stream: a #RedStream
 * @no_delay: whether to enable TCP_NODELAY on @@stream
 *
 * Returns: #true if the operation succeeded, #false otherwise.
 */
bool red_stream_set_no_delay(RedStream *stream, bool no_delay)
{
    return red_socket_set_no_delay(stream->socket, no_delay);
}

int red_stream_get_no_delay(RedStream *stream)
{
    return red_socket_get_no_delay(stream->socket);
}

#ifndef _WIN32
int red_stream_send_msgfd(RedStream *stream, int fd)
{
    struct msghdr msgh = { 0, };
    struct iovec iov;
    int r;

    const size_t fd_size = 1 * sizeof(int);
    struct cmsghdr *cmsg;
    union {
        struct cmsghdr hdr;
        char data[CMSG_SPACE(fd_size)];
    } control;

    spice_return_val_if_fail(red_stream_is_plain_unix(stream), -1);

    /* set the payload */
    iov.iov_base = (char*)"@";
    iov.iov_len = 1;
    msgh.msg_iovlen = 1;
    msgh.msg_iov = &iov;

    if (fd != -1) {
        msgh.msg_control = control.data;
        msgh.msg_controllen = sizeof(control.data);
        /* CMSG_SPACE() might be larger than CMSG_LEN() as it can include some
         * padding. We set the whole control data to 0 to avoid valgrind warnings
         */
        memset(control.data, 0, sizeof(control.data));

        cmsg = CMSG_FIRSTHDR(&msgh);
        cmsg->cmsg_len = CMSG_LEN(fd_size);
        cmsg->cmsg_level = SOL_SOCKET;
        cmsg->cmsg_type = SCM_RIGHTS;
        memcpy(CMSG_DATA(cmsg), &fd, fd_size);
    }

    do {
        r = sendmsg(stream->socket, &msgh, MSG_NOSIGNAL);
    } while (r < 0 && (errno == EINTR || errno == EAGAIN));

    return r;
}
#endif

ssize_t red_stream_writev(RedStream *s, const struct iovec *iov, int iovcnt)
{
    int i;
    int n;
    ssize_t ret = 0;

    if (s->priv->writev != NULL && iovcnt > 1) {
        return s->priv->writev(s, iov, iovcnt);
    }

    for (i = 0; i < iovcnt; ++i) {
        n = red_stream_write(s, iov[i].iov_base, iov[i].iov_len);
        if (n <= 0)
            return ret == 0 ? n : ret;
        ret += n;
    }

    return ret;
}

void red_stream_free(RedStream *s)
{
    if (!s) {
        return;
    }

    red_stream_push_channel_event(s, SPICE_CHANNEL_EVENT_DISCONNECTED);

#if HAVE_SASL
    if (s->priv->sasl.conn) {
        s->priv->sasl.runSSF = s->priv->sasl.wantSSF = 0;
        s->priv->sasl.encodedLength = s->priv->sasl.encodedOffset = 0;
        s->priv->sasl.encoded = NULL;
        sasl_dispose(&s->priv->sasl.conn);
        s->priv->sasl.conn = NULL;
    }
#endif

    if (s->priv->ssl) {
        SSL_free(s->priv->ssl);
    }

    websocket_free(s->priv->ws);

    red_stream_remove_watch(s);
    socket_close(s->socket);

    g_free(s);
}

void red_stream_push_channel_event(RedStream *s, int event)
{
    RedsState *reds = s->priv->reds;
    MainDispatcher *md = reds_get_main_dispatcher(reds);
    main_dispatcher_channel_event(md, event, s->priv->info);
}

static void red_stream_set_socket(RedStream *stream, int socket)
{
    stream->socket = socket;
    /* deprecated fields. Filling them for backward compatibility */
    stream->priv->info->llen = sizeof(stream->priv->info->laddr);
    stream->priv->info->plen = sizeof(stream->priv->info->paddr);
    getsockname(stream->socket, (struct sockaddr*)(&stream->priv->info->laddr), &stream->priv->info->llen);
    getpeername(stream->socket, (struct sockaddr*)(&stream->priv->info->paddr), &stream->priv->info->plen);

    stream->priv->info->flags |= SPICE_CHANNEL_EVENT_FLAG_ADDR_EXT;
    stream->priv->info->llen_ext = sizeof(stream->priv->info->laddr_ext);
    stream->priv->info->plen_ext = sizeof(stream->priv->info->paddr_ext);
    getsockname(stream->socket, (struct sockaddr*)(&stream->priv->info->laddr_ext),
                &stream->priv->info->llen_ext);
    getpeername(stream->socket, (struct sockaddr*)(&stream->priv->info->paddr_ext),
                &stream->priv->info->plen_ext);
}


void red_stream_set_channel(RedStream *stream, int connection_id,
                            int channel_type, int channel_id)
{
    stream->priv->info->connection_id = connection_id;
    stream->priv->info->type = channel_type;
    stream->priv->info->id   = channel_id;
    if (red_stream_is_ssl(stream)) {
        stream->priv->info->flags |= SPICE_CHANNEL_EVENT_FLAG_TLS;
    }
}

RedStream *red_stream_new(RedsState *reds, int socket)
{
    RedStream *stream;

    stream = g_malloc0(sizeof(RedStream) + sizeof(RedStreamPrivate));
    stream->priv = (RedStreamPrivate *)(stream+1);
    stream->priv->info = g_new0(SpiceChannelEventInfo, 1);
    stream->priv->reds = reds;
    stream->priv->core = reds_get_core_interface(reds);
    red_stream_set_socket(stream, socket);

    stream->priv->read = stream_read_cb;
    stream->priv->write = stream_write_cb;
    stream->priv->writev = stream_writev_cb;

    return stream;
}

void red_stream_set_core_interface(RedStream *stream, SpiceCoreInterfaceInternal *core)
{
    red_stream_remove_watch(stream);
    stream->priv->core = core;
}

bool red_stream_is_ssl(RedStream *stream)
{
    return (stream->priv->ssl != NULL);
}

static void red_stream_disable_writev(RedStream *stream)
{
    stream->priv->writev = NULL;
}

RedStreamSslStatus red_stream_ssl_accept(RedStream *stream)
{
    int ssl_error;
    int return_code;

    return_code = SSL_accept(stream->priv->ssl);
    if (return_code == 1) {
        return RED_STREAM_SSL_STATUS_OK;
    }

#ifndef SSL_OP_NO_RENEGOTIATION
    // With OpenSSL 1.0.2 and earlier: disable client-side renogotiation
    stream->priv->ssl->s3->flags |= SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS;
#endif

    ssl_error = SSL_get_error(stream->priv->ssl, return_code);
    if (return_code == -1 && (ssl_error == SSL_ERROR_WANT_READ ||
                              ssl_error == SSL_ERROR_WANT_WRITE)) {
        if (ssl_error == SSL_ERROR_WANT_READ) {
            return RED_STREAM_SSL_STATUS_WAIT_FOR_READ;
        } else {
            return RED_STREAM_SSL_STATUS_WAIT_FOR_WRITE;
        }
    }

    red_dump_openssl_errors();
    spice_warning("SSL_accept failed, error=%d", ssl_error);
    SSL_free(stream->priv->ssl);
    stream->priv->ssl = NULL;

    return RED_STREAM_SSL_STATUS_ERROR;
}

RedStreamSslStatus red_stream_enable_ssl(RedStream *stream, SSL_CTX *ctx)
{
    BIO *sbio;

    // Handle SSL handshaking
    if (!(sbio = BIO_new_socket(stream->socket, BIO_NOCLOSE))) {
        spice_warning("could not allocate ssl bio socket");
        return RED_STREAM_SSL_STATUS_ERROR;
    }

    stream->priv->ssl = SSL_new(ctx);
    if (!stream->priv->ssl) {
        spice_warning("could not allocate ssl context");
        BIO_free(sbio);
        return RED_STREAM_SSL_STATUS_ERROR;
    }

    SSL_set_bio(stream->priv->ssl, sbio, sbio);

    stream->priv->write = stream_ssl_write_cb;
    stream->priv->read = stream_ssl_read_cb;
    red_stream_disable_writev(stream);

    return red_stream_ssl_accept(stream);
}

void red_stream_set_async_error_handler(RedStream *stream,
                                        AsyncReadError error_handler)
{
    stream->priv->async_read.error = error_handler;
}

static inline void async_read_clear_handlers(RedStream *stream)
{
    AsyncRead *async = &stream->priv->async_read;
    red_stream_remove_watch(stream);
    async->now = NULL;
    async->end = NULL;
}

static void async_read_handler(G_GNUC_UNUSED int fd,
                               G_GNUC_UNUSED int event,
                               void *data)
{
    RedStream *stream = data;
    AsyncRead *async = &stream->priv->async_read;
    SpiceCoreInterfaceInternal *core = stream->priv->core;

    for (;;) {
        int n = async->end - async->now;

        spice_assert(n > 0);
        n = red_stream_read(stream, async->now, n);
        if (n <= 0) {
            int err = n < 0 ? errno: 0;
            switch (err) {
            case EAGAIN:
                if (!stream->watch) {
                    stream->watch = core->watch_add(core, stream->socket,
                                                    SPICE_WATCH_EVENT_READ,
                                                    async_read_handler, stream);
                }
                return;
            case EINTR:
                break;
            default:
                async_read_clear_handlers(stream);
                if (async->error) {
                    async->error(async->opaque, err);
                }
                return;
            }
        } else {
            async->now += n;
            if (async->now == async->end) {
                async_read_clear_handlers(stream);
                async->done(async->opaque);
                return;
            }
        }
    }
}

void red_stream_async_read(RedStream *stream,
                           uint8_t *data, size_t size,
                           AsyncReadDone read_done_cb,
                           void *opaque)
{
    AsyncRead *async = &stream->priv->async_read;

    g_return_if_fail(async->now == NULL && async->end == NULL);
    if (size == 0) {
        read_done_cb(opaque);
        return;
    }
    async->now = data;
    async->end = async->now + size;
    async->done = read_done_cb;
    async->opaque = opaque;
    async_read_handler(0, 0, stream);

}

#if HAVE_SASL
static bool red_stream_write_u8(RedStream *s, uint8_t n)
{
    return red_stream_write_all(s, &n, sizeof(uint8_t));
}

static bool red_stream_write_u32_le(RedStream *s, uint32_t n)
{
    n = GUINT32_TO_LE(n);
    return red_stream_write_all(s, &n, sizeof(uint32_t));
}

static ssize_t red_stream_sasl_write(RedStream *s, const void *buf, size_t nbyte)
{
    ssize_t ret;

    if (!s->priv->sasl.encoded) {
        int err;
        err = sasl_encode(s->priv->sasl.conn, (char *)buf, nbyte,
                          (const char **)&s->priv->sasl.encoded,
                          &s->priv->sasl.encodedLength);
        if (err != SASL_OK) {
            spice_warning("sasl_encode error: %d", err);
            errno = EIO;
            return -1;
        }

        if (s->priv->sasl.encodedLength == 0) {
            return 0;
        }

        if (!s->priv->sasl.encoded) {
            spice_warning("sasl_encode didn't return a buffer!");
            return 0;
        }

        s->priv->sasl.encodedOffset = 0;
    }

    ret = s->priv->write(s, s->priv->sasl.encoded + s->priv->sasl.encodedOffset,
                         s->priv->sasl.encodedLength - s->priv->sasl.encodedOffset);

    if (ret <= 0) {
        return ret;
    }

    s->priv->sasl.encodedOffset += ret;
    if (s->priv->sasl.encodedOffset == s->priv->sasl.encodedLength) {
        s->priv->sasl.encoded = NULL;
        s->priv->sasl.encodedOffset = s->priv->sasl.encodedLength = 0;
        return nbyte;
    }

    /* we didn't flush the encoded buffer */
    errno = EAGAIN;
    return -1;
}

static ssize_t red_stream_sasl_read(RedStream *s, uint8_t *buf, size_t nbyte)
{
    uint8_t encoded[4096];
    const char *decoded;
    unsigned int decodedlen;
    int err;
    int n;

    n = spice_buffer_copy(&s->priv->sasl.inbuffer, buf, nbyte);
    if (n > 0) {
        spice_buffer_remove(&s->priv->sasl.inbuffer, n);
        if (n == nbyte)
            return n;
        nbyte -= n;
        buf += n;
    }

    n = s->priv->read(s, encoded, sizeof(encoded));
    if (n <= 0) {
        return n;
    }

    err = sasl_decode(s->priv->sasl.conn,
                      (char *)encoded, n,
                      &decoded, &decodedlen);
    if (err != SASL_OK) {
        spice_warning("sasl_decode error: %d", err);
        errno = EIO;
        return -1;
    }

    if (decodedlen == 0) {
        errno = EAGAIN;
        return -1;
    }

    n = MIN(nbyte, decodedlen);
    memcpy(buf, decoded, n);
    spice_buffer_append(&s->priv->sasl.inbuffer, decoded + n, decodedlen - n);
    return n;
}

static char *addr_to_string(const char *format,
                            struct sockaddr_storage *sa,
                            socklen_t salen)
{
    char host[NI_MAXHOST];
    char serv[NI_MAXSERV];
    int err;

    if ((err = getnameinfo((struct sockaddr *)sa, salen,
                           host, sizeof(host),
                           serv, sizeof(serv),
                           NI_NUMERICHOST | NI_NUMERICSERV)) != 0) {
        spice_warning("Cannot resolve address %d: %s",
                      err, gai_strerror(err));
        return NULL;
    }

    return g_strdup_printf(format, host, serv);
}

static char *red_stream_get_local_address(RedStream *stream)
{
    return addr_to_string("%s;%s", &stream->priv->info->laddr_ext,
                          stream->priv->info->llen_ext);
}

static char *red_stream_get_remote_address(RedStream *stream)
{
    return addr_to_string("%s;%s", &stream->priv->info->paddr_ext,
                          stream->priv->info->plen_ext);
}

static int auth_sasl_check_ssf(RedSASL *sasl, int *runSSF)
{
    const void *val;
    int err, ssf;

    *runSSF = 0;
    if (!sasl->wantSSF) {
        return 1;
    }

    err = sasl_getprop(sasl->conn, SASL_SSF, &val);
    if (err != SASL_OK) {
        return 0;
    }

    ssf = *(const int *)val;
    spice_debug("negotiated an SSF of %d", ssf);
    if (ssf < 56) {
        return 0; /* 56 is good for Kerberos */
    }

    *runSSF = 1;

    /* We have a SSF that's good enough */
    return 1;
}

typedef struct RedSASLAuth {
    RedStream *stream;
    // list of mechanisms allowed, allocated and freed by SASL
    char *mechlist;
    // mech received
    char *mechname;
    uint32_t len;
    char *data;
    // callback to call if success
    RedSaslResult result_cb;
    void *result_opaque;
    // saved Async callback, we need to call if failed as
    // we need to chain it in order to use a different opaque data
    AsyncReadError saved_error_cb;
} RedSASLAuth;

static void red_sasl_auth_free(RedSASLAuth *auth)
{
    g_free(auth->data);
    g_free(auth->mechname);
    g_free(auth->mechlist);
    g_free(auth);
}

// handle SASL termination, either success or error
// NOTE: After this function is called usually there should be a
// return or the function should exit
static void red_sasl_async_result(RedSASLAuth *auth, RedSaslError err)
{
    red_stream_set_async_error_handler(auth->stream, auth->saved_error_cb);
    auth->result_cb(auth->result_opaque, err);
    red_sasl_auth_free(auth);
}

static void red_sasl_error(void *opaque, int err)
{
    RedSASLAuth *auth = opaque;
    red_stream_set_async_error_handler(auth->stream, auth->saved_error_cb);
    if (auth->saved_error_cb) {
        auth->saved_error_cb(auth->result_opaque, err);
    }
    red_sasl_auth_free(auth);
}

/*
 * Step Msg
 *
 * Input from client:
 *
 * u32 clientin-length
 * u8-array clientin-string
 *
 * Output to client:
 *
 * u32 serverout-length
 * u8-array serverout-strin
 * u8 continue
 */
#define SASL_MAX_MECHNAME_LEN 100
#define SASL_DATA_MAX_LEN (1024 * 1024)

static void red_sasl_handle_auth_steplen(void *opaque);

/*
 * Start Msg
 *
 * Input from client:
 *
 * u32 clientin-length
 * u8-array clientin-string
 *
 * Output to client:
 *
 * u32 serverout-length
 * u8-array serverout-strin
 * u8 continue
 */

static void red_sasl_handle_auth_step(void *opaque)
{
    RedSASLAuth *auth = opaque;
    RedStream *stream = auth->stream;
    const char *serverout;
    unsigned int serveroutlen;
    int err;
    char *clientdata = NULL;
    RedSASL *sasl = &stream->priv->sasl;
    uint32_t datalen = auth->len;

    /* NB, distinction of NULL vs "" is *critical* in SASL */
    if (datalen) {
        clientdata = auth->data;
        clientdata[datalen - 1] = '\0'; /* Wire includes '\0', but make sure */
        datalen--; /* Don't count NULL byte when passing to _start() */
    }

    if (auth->mechname != NULL) {
        spice_debug("Start SASL auth with mechanism %s. Data %p (%d bytes)",
                    auth->mechname, clientdata, datalen);
        err = sasl_server_start(sasl->conn,
                                auth->mechname,
                                clientdata,
                                datalen,
                                &serverout,
                                &serveroutlen);
        g_free(auth->mechname);
        auth->mechname = NULL;
    } else {
        spice_debug("Step using SASL Data %p (%d bytes)", clientdata, datalen);
        err = sasl_server_step(sasl->conn,
                               clientdata,
                               datalen,
                               &serverout,
                               &serveroutlen);
    }
    if (err != SASL_OK &&
        err != SASL_CONTINUE) {
        spice_warning("sasl step failed %d (%s)",
                    err, sasl_errdetail(sasl->conn));
        return red_sasl_async_result(auth, RED_SASL_ERROR_GENERIC);
    }

    if (serveroutlen > SASL_DATA_MAX_LEN) {
        spice_warning("sasl step reply data too long %d",
                      serveroutlen);
        return red_sasl_async_result(auth, RED_SASL_ERROR_GENERIC);
    }

    spice_debug("SASL return data %d bytes, %p", serveroutlen, serverout);

    if (serveroutlen) {
        serveroutlen += 1;
        red_stream_write_u32_le(stream, serveroutlen);
        red_stream_write_all(stream, serverout, serveroutlen);
    } else {
        red_stream_write_u32_le(stream, 0);
    }

    /* Whether auth is complete */
    red_stream_write_u8(stream, err == SASL_CONTINUE ? 0 : 1);

    if (err == SASL_CONTINUE) {
        spice_debug("%s", "Authentication must continue");
        /* Wait for step length */
        red_stream_async_read(stream, (uint8_t *)&auth->len, sizeof(uint32_t),
                              red_sasl_handle_auth_steplen, auth);
        return;
    } else {
        int ssf;

        if (auth_sasl_check_ssf(sasl, &ssf) == 0) {
            spice_warning("Authentication rejected for weak SSF");
            goto authreject;
        }

        spice_debug("Authentication successful");
        red_stream_write_u32_le(stream, SPICE_LINK_ERR_OK); /* Accept auth */

        /*
         * Delay writing in SSF encoded until now
         */
        sasl->runSSF = ssf;
        red_stream_disable_writev(stream); /* make sure writev isn't called directly anymore */

        return red_sasl_async_result(auth, RED_SASL_ERROR_OK);
    }

authreject:
    red_stream_write_u32_le(stream, 1); /* Reject auth */
    red_stream_write_u32_le(stream, sizeof("Authentication failed"));
    red_stream_write_all(stream, "Authentication failed", sizeof("Authentication failed"));

    red_sasl_async_result(auth, RED_SASL_ERROR_AUTH_FAILED);
}

static void red_sasl_handle_auth_steplen(void *opaque)
{
    RedSASLAuth *auth = opaque;

    auth->len = GUINT32_FROM_LE(auth->len);
    uint32_t len = auth->len;
    spice_debug("Got steplen %d", len);
    if (len > SASL_DATA_MAX_LEN) {
        spice_warning("Too much SASL data %d", len);
        return red_sasl_async_result(opaque, auth->mechname ? RED_SASL_ERROR_INVALID_DATA : RED_SASL_ERROR_GENERIC);
    }

    auth->data = g_realloc(auth->data, len);
    red_stream_async_read(auth->stream, (uint8_t *)auth->data, len,
                          red_sasl_handle_auth_step, auth);
}



static void red_sasl_handle_auth_mechname(void *opaque)
{
    RedSASLAuth *auth = opaque;

    auth->mechname[auth->len] = '\0';
    spice_debug("Got client mechname '%s' check against '%s'",
                auth->mechname, auth->mechlist);

    char quoted_mechname[SASL_MAX_MECHNAME_LEN + 4];
    sprintf(quoted_mechname, ",%s,", auth->mechname);

    if (strchr(auth->mechname, ',') || strstr(auth->mechlist, quoted_mechname) == NULL) {
        return red_sasl_async_result(auth, RED_SASL_ERROR_INVALID_DATA);
    }

    spice_debug("Validated mechname '%s'", auth->mechname);

    red_stream_async_read(auth->stream, (uint8_t *)&auth->len, sizeof(uint32_t),
                          red_sasl_handle_auth_steplen, auth);
}

static void red_sasl_handle_auth_mechlen(void *opaque)
{
    RedSASLAuth *auth = opaque;

    auth->len = GUINT32_FROM_LE(auth->len);
    uint32_t len = auth->len;
    if (len < 1 || len > SASL_MAX_MECHNAME_LEN) {
        spice_warning("Got bad client mechname len %d", len);
        return red_sasl_async_result(auth, RED_SASL_ERROR_GENERIC);
    }

    auth->mechname = g_malloc(len + 1);

    spice_debug("Wait for client mechname");
    red_stream_async_read(auth->stream, (uint8_t *)auth->mechname, len,
                          red_sasl_handle_auth_mechname, auth);
}

bool red_sasl_start_auth(RedStream *stream, RedSaslResult result_cb, void *result_opaque)
{
    const char *mechlist = NULL;
    sasl_security_properties_t secprops;
    int err;
    char *localAddr, *remoteAddr;
    int mechlistlen;
    RedSASL *sasl = &stream->priv->sasl;
    RedSASLAuth *auth;

    if (!(localAddr = red_stream_get_local_address(stream))) {
        goto error;
    }

    if (!(remoteAddr = red_stream_get_remote_address(stream))) {
        g_free(localAddr);
        goto error;
    }

    err = sasl_server_new("spice",
                          NULL, /* FQDN - just delegates to gethostname */
                          NULL, /* User realm */
                          localAddr,
                          remoteAddr,
                          NULL, /* Callbacks, not needed */
                          SASL_SUCCESS_DATA,
                          &sasl->conn);
    g_free(localAddr);
    g_free(remoteAddr);
    localAddr = remoteAddr = NULL;

    if (err != SASL_OK) {
        spice_warning("sasl context setup failed %d (%s)",
                    err, sasl_errstring(err, NULL, NULL));
        sasl->conn = NULL;
        goto error;
    }

    /* Inform SASL that we've got an external SSF layer from TLS */
    if (stream->priv->ssl) {
        sasl_ssf_t ssf;

        ssf = SSL_get_cipher_bits(stream->priv->ssl, NULL);
        err = sasl_setprop(sasl->conn, SASL_SSF_EXTERNAL, &ssf);
        if (err != SASL_OK) {
            spice_warning("cannot set SASL external SSF %d (%s)",
                        err, sasl_errstring(err, NULL, NULL));
            goto error_dispose;
        }
    } else {
        sasl->wantSSF = 1;
    }

    memset(&secprops, 0, sizeof secprops);
    /* Inform SASL that we've got an external SSF layer from TLS */
    if (stream->priv->ssl) {
        /* If we've got TLS (or UNIX domain sock), we don't care about SSF */
        secprops.min_ssf = 0;
        secprops.max_ssf = 0;
        secprops.maxbufsize = 8192;
        secprops.security_flags = 0;
    } else {
        /* Plain TCP, better get an SSF layer */
        secprops.min_ssf = 56; /* Good enough to require kerberos */
        secprops.max_ssf = 100000; /* Arbitrary big number */
        secprops.maxbufsize = 8192;
        /* Forbid any anonymous or trivially crackable auth */
        secprops.security_flags =
            SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
    }

    err = sasl_setprop(sasl->conn, SASL_SEC_PROPS, &secprops);
    if (err != SASL_OK) {
        spice_warning("cannot set SASL security props %d (%s)",
                      err, sasl_errstring(err, NULL, NULL));
        goto error_dispose;
    }

    err = sasl_listmech(sasl->conn,
                        NULL, /* Don't need to set user */
                        ",", /* Prefix */
                        ",", /* Separator */
                        ",", /* Suffix */
                        &mechlist,
                        NULL,
                        NULL);
    if (err != SASL_OK || mechlist == NULL) {
        spice_warning("cannot list SASL mechanisms %d (%s)",
                      err, sasl_errdetail(sasl->conn));
        goto error_dispose;
    }

    spice_debug("Available mechanisms for client: '%s'", mechlist);

    mechlistlen = strlen(mechlist);
    if (!red_stream_write_u32_le(stream, mechlistlen)
        || !red_stream_write_all(stream, mechlist, mechlistlen)) {
        spice_warning("SASL mechanisms write error");
        goto error;
    }

    auth = g_new0(RedSASLAuth, 1);
    auth->stream = stream;
    auth->result_cb = result_cb;
    auth->result_opaque = result_opaque;
    auth->saved_error_cb = stream->priv->async_read.error;
    auth->mechlist = g_strdup(mechlist);

    spice_debug("Wait for client mechname length");
    red_stream_set_async_error_handler(stream, red_sasl_error);
    red_stream_async_read(stream, (uint8_t *)&auth->len, sizeof(uint32_t),
                          red_sasl_handle_auth_mechlen, auth);

    return true;

error_dispose:
    sasl_dispose(&sasl->conn);
    sasl->conn = NULL;
error:
    return false;
}
#endif

static ssize_t stream_websocket_read(RedStream *s, void *buf, size_t size)
{
    unsigned flags;
    int len;

    do {
        len = websocket_read(s->priv->ws, buf, size, &flags);
    } while (len == 0 && flags != 0);
    return len;
}

static ssize_t stream_websocket_write(RedStream *s, const void *buf, size_t size)
{
    return websocket_write(s->priv->ws, buf, size, WEBSOCKET_BINARY_FINAL);
}

static ssize_t stream_websocket_writev(RedStream *s, const struct iovec *iov, int iovcnt)
{
    return websocket_writev(s->priv->ws, (struct iovec *) iov, iovcnt, WEBSOCKET_BINARY_FINAL);
}

/*
    If we detect that a newly opened stream appears to be using
    the WebSocket protocol, we will put in place cover functions
    that will speak WebSocket to the client, but allow the server
    to continue to use normal stream read/write/writev semantics.
*/
bool red_stream_is_websocket(RedStream *stream, const void *buf, size_t len)
{
    if (stream->priv->ws) {
        return false;
    }

    stream->priv->ws = websocket_new(buf, len, stream,
                                     (websocket_read_cb_t) stream->priv->read,
                                     (websocket_write_cb_t) stream->priv->write,
                                     (websocket_writev_cb_t) stream->priv->writev);
    if (stream->priv->ws) {
        stream->priv->read = stream_websocket_read;
        stream->priv->write = stream_websocket_write;

        if (stream->priv->writev) {
            stream->priv->writev = stream_websocket_writev;
        }

        return true;
    }

    return false;
}