qemu/block/ssh.c
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   1/*
   2 * Secure Shell (ssh) backend for QEMU.
   3 *
   4 * Copyright (C) 2013 Red Hat Inc., Richard W.M. Jones <rjones@redhat.com>
   5 *
   6 * Permission is hereby granted, free of charge, to any person obtaining a copy
   7 * of this software and associated documentation files (the "Software"), to deal
   8 * in the Software without restriction, including without limitation the rights
   9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10 * copies of the Software, and to permit persons to whom the Software is
  11 * furnished to do so, subject to the following conditions:
  12 *
  13 * The above copyright notice and this permission notice shall be included in
  14 * all copies or substantial portions of the Software.
  15 *
  16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22 * THE SOFTWARE.
  23 */
  24
  25#include "qemu/osdep.h"
  26
  27#include <libssh2.h>
  28#include <libssh2_sftp.h>
  29
  30#include "block/block_int.h"
  31#include "qapi/error.h"
  32#include "qemu/error-report.h"
  33#include "qemu/option.h"
  34#include "qemu/cutils.h"
  35#include "qemu/sockets.h"
  36#include "qemu/uri.h"
  37#include "qapi/qapi-visit-sockets.h"
  38#include "qapi/qapi-visit-block-core.h"
  39#include "qapi/qmp/qdict.h"
  40#include "qapi/qmp/qstring.h"
  41#include "qapi/qobject-input-visitor.h"
  42#include "qapi/qobject-output-visitor.h"
  43
  44/* DEBUG_SSH=1 enables the DPRINTF (debugging printf) statements in
  45 * this block driver code.
  46 *
  47 * TRACE_LIBSSH2=<bitmask> enables tracing in libssh2 itself.  Note
  48 * that this requires that libssh2 was specially compiled with the
  49 * `./configure --enable-debug' option, so most likely you will have
  50 * to compile it yourself.  The meaning of <bitmask> is described
  51 * here: http://www.libssh2.org/libssh2_trace.html
  52 */
  53#define DEBUG_SSH     0
  54#define TRACE_LIBSSH2 0 /* or try: LIBSSH2_TRACE_SFTP */
  55
  56#define DPRINTF(fmt, ...)                           \
  57    do {                                            \
  58        if (DEBUG_SSH) {                            \
  59            fprintf(stderr, "ssh: %-15s " fmt "\n", \
  60                    __func__, ##__VA_ARGS__);       \
  61        }                                           \
  62    } while (0)
  63
  64typedef struct BDRVSSHState {
  65    /* Coroutine. */
  66    CoMutex lock;
  67
  68    /* SSH connection. */
  69    int sock;                         /* socket */
  70    LIBSSH2_SESSION *session;         /* ssh session */
  71    LIBSSH2_SFTP *sftp;               /* sftp session */
  72    LIBSSH2_SFTP_HANDLE *sftp_handle; /* sftp remote file handle */
  73
  74    /* See ssh_seek() function below. */
  75    int64_t offset;
  76    bool offset_op_read;
  77
  78    /* File attributes at open.  We try to keep the .filesize field
  79     * updated if it changes (eg by writing at the end of the file).
  80     */
  81    LIBSSH2_SFTP_ATTRIBUTES attrs;
  82
  83    InetSocketAddress *inet;
  84
  85    /* Used to warn if 'flush' is not supported. */
  86    bool unsafe_flush_warning;
  87} BDRVSSHState;
  88
  89static void ssh_state_init(BDRVSSHState *s)
  90{
  91    memset(s, 0, sizeof *s);
  92    s->sock = -1;
  93    s->offset = -1;
  94    qemu_co_mutex_init(&s->lock);
  95}
  96
  97static void ssh_state_free(BDRVSSHState *s)
  98{
  99    if (s->sftp_handle) {
 100        libssh2_sftp_close(s->sftp_handle);
 101    }
 102    if (s->sftp) {
 103        libssh2_sftp_shutdown(s->sftp);
 104    }
 105    if (s->session) {
 106        libssh2_session_disconnect(s->session,
 107                                   "from qemu ssh client: "
 108                                   "user closed the connection");
 109        libssh2_session_free(s->session);
 110    }
 111    if (s->sock >= 0) {
 112        close(s->sock);
 113    }
 114}
 115
 116static void GCC_FMT_ATTR(3, 4)
 117session_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
 118{
 119    va_list args;
 120    char *msg;
 121
 122    va_start(args, fs);
 123    msg = g_strdup_vprintf(fs, args);
 124    va_end(args);
 125
 126    if (s->session) {
 127        char *ssh_err;
 128        int ssh_err_code;
 129
 130        /* This is not an errno.  See <libssh2.h>. */
 131        ssh_err_code = libssh2_session_last_error(s->session,
 132                                                  &ssh_err, NULL, 0);
 133        error_setg(errp, "%s: %s (libssh2 error code: %d)",
 134                   msg, ssh_err, ssh_err_code);
 135    } else {
 136        error_setg(errp, "%s", msg);
 137    }
 138    g_free(msg);
 139}
 140
 141static void GCC_FMT_ATTR(3, 4)
 142sftp_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
 143{
 144    va_list args;
 145    char *msg;
 146
 147    va_start(args, fs);
 148    msg = g_strdup_vprintf(fs, args);
 149    va_end(args);
 150
 151    if (s->sftp) {
 152        char *ssh_err;
 153        int ssh_err_code;
 154        unsigned long sftp_err_code;
 155
 156        /* This is not an errno.  See <libssh2.h>. */
 157        ssh_err_code = libssh2_session_last_error(s->session,
 158                                                  &ssh_err, NULL, 0);
 159        /* See <libssh2_sftp.h>. */
 160        sftp_err_code = libssh2_sftp_last_error((s)->sftp);
 161
 162        error_setg(errp,
 163                   "%s: %s (libssh2 error code: %d, sftp error code: %lu)",
 164                   msg, ssh_err, ssh_err_code, sftp_err_code);
 165    } else {
 166        error_setg(errp, "%s", msg);
 167    }
 168    g_free(msg);
 169}
 170
 171static void GCC_FMT_ATTR(2, 3)
 172sftp_error_report(BDRVSSHState *s, const char *fs, ...)
 173{
 174    va_list args;
 175
 176    va_start(args, fs);
 177    error_vprintf(fs, args);
 178
 179    if ((s)->sftp) {
 180        char *ssh_err;
 181        int ssh_err_code;
 182        unsigned long sftp_err_code;
 183
 184        /* This is not an errno.  See <libssh2.h>. */
 185        ssh_err_code = libssh2_session_last_error(s->session,
 186                                                  &ssh_err, NULL, 0);
 187        /* See <libssh2_sftp.h>. */
 188        sftp_err_code = libssh2_sftp_last_error((s)->sftp);
 189
 190        error_printf(": %s (libssh2 error code: %d, sftp error code: %lu)",
 191                     ssh_err, ssh_err_code, sftp_err_code);
 192    }
 193
 194    va_end(args);
 195    error_printf("\n");
 196}
 197
 198static int parse_uri(const char *filename, QDict *options, Error **errp)
 199{
 200    URI *uri = NULL;
 201    QueryParams *qp;
 202    char *port_str;
 203    int i;
 204
 205    uri = uri_parse(filename);
 206    if (!uri) {
 207        return -EINVAL;
 208    }
 209
 210    if (g_strcmp0(uri->scheme, "ssh") != 0) {
 211        error_setg(errp, "URI scheme must be 'ssh'");
 212        goto err;
 213    }
 214
 215    if (!uri->server || strcmp(uri->server, "") == 0) {
 216        error_setg(errp, "missing hostname in URI");
 217        goto err;
 218    }
 219
 220    if (!uri->path || strcmp(uri->path, "") == 0) {
 221        error_setg(errp, "missing remote path in URI");
 222        goto err;
 223    }
 224
 225    qp = query_params_parse(uri->query);
 226    if (!qp) {
 227        error_setg(errp, "could not parse query parameters");
 228        goto err;
 229    }
 230
 231    if(uri->user && strcmp(uri->user, "") != 0) {
 232        qdict_put_str(options, "user", uri->user);
 233    }
 234
 235    qdict_put_str(options, "server.host", uri->server);
 236
 237    port_str = g_strdup_printf("%d", uri->port ?: 22);
 238    qdict_put_str(options, "server.port", port_str);
 239    g_free(port_str);
 240
 241    qdict_put_str(options, "path", uri->path);
 242
 243    /* Pick out any query parameters that we understand, and ignore
 244     * the rest.
 245     */
 246    for (i = 0; i < qp->n; ++i) {
 247        if (strcmp(qp->p[i].name, "host_key_check") == 0) {
 248            qdict_put_str(options, "host_key_check", qp->p[i].value);
 249        }
 250    }
 251
 252    query_params_free(qp);
 253    uri_free(uri);
 254    return 0;
 255
 256 err:
 257    if (uri) {
 258      uri_free(uri);
 259    }
 260    return -EINVAL;
 261}
 262
 263static bool ssh_has_filename_options_conflict(QDict *options, Error **errp)
 264{
 265    const QDictEntry *qe;
 266
 267    for (qe = qdict_first(options); qe; qe = qdict_next(options, qe)) {
 268        if (!strcmp(qe->key, "host") ||
 269            !strcmp(qe->key, "port") ||
 270            !strcmp(qe->key, "path") ||
 271            !strcmp(qe->key, "user") ||
 272            !strcmp(qe->key, "host_key_check") ||
 273            strstart(qe->key, "server.", NULL))
 274        {
 275            error_setg(errp, "Option '%s' cannot be used with a file name",
 276                       qe->key);
 277            return true;
 278        }
 279    }
 280
 281    return false;
 282}
 283
 284static void ssh_parse_filename(const char *filename, QDict *options,
 285                               Error **errp)
 286{
 287    if (ssh_has_filename_options_conflict(options, errp)) {
 288        return;
 289    }
 290
 291    parse_uri(filename, options, errp);
 292}
 293
 294static int check_host_key_knownhosts(BDRVSSHState *s,
 295                                     const char *host, int port, Error **errp)
 296{
 297    const char *home;
 298    char *knh_file = NULL;
 299    LIBSSH2_KNOWNHOSTS *knh = NULL;
 300    struct libssh2_knownhost *found;
 301    int ret, r;
 302    const char *hostkey;
 303    size_t len;
 304    int type;
 305
 306    hostkey = libssh2_session_hostkey(s->session, &len, &type);
 307    if (!hostkey) {
 308        ret = -EINVAL;
 309        session_error_setg(errp, s, "failed to read remote host key");
 310        goto out;
 311    }
 312
 313    knh = libssh2_knownhost_init(s->session);
 314    if (!knh) {
 315        ret = -EINVAL;
 316        session_error_setg(errp, s,
 317                           "failed to initialize known hosts support");
 318        goto out;
 319    }
 320
 321    home = getenv("HOME");
 322    if (home) {
 323        knh_file = g_strdup_printf("%s/.ssh/known_hosts", home);
 324    } else {
 325        knh_file = g_strdup_printf("/root/.ssh/known_hosts");
 326    }
 327
 328    /* Read all known hosts from OpenSSH-style known_hosts file. */
 329    libssh2_knownhost_readfile(knh, knh_file, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
 330
 331    r = libssh2_knownhost_checkp(knh, host, port, hostkey, len,
 332                                 LIBSSH2_KNOWNHOST_TYPE_PLAIN|
 333                                 LIBSSH2_KNOWNHOST_KEYENC_RAW,
 334                                 &found);
 335    switch (r) {
 336    case LIBSSH2_KNOWNHOST_CHECK_MATCH:
 337        /* OK */
 338        DPRINTF("host key OK: %s", found->key);
 339        break;
 340    case LIBSSH2_KNOWNHOST_CHECK_MISMATCH:
 341        ret = -EINVAL;
 342        session_error_setg(errp, s,
 343                      "host key does not match the one in known_hosts"
 344                      " (found key %s)", found->key);
 345        goto out;
 346    case LIBSSH2_KNOWNHOST_CHECK_NOTFOUND:
 347        ret = -EINVAL;
 348        session_error_setg(errp, s, "no host key was found in known_hosts");
 349        goto out;
 350    case LIBSSH2_KNOWNHOST_CHECK_FAILURE:
 351        ret = -EINVAL;
 352        session_error_setg(errp, s,
 353                      "failure matching the host key with known_hosts");
 354        goto out;
 355    default:
 356        ret = -EINVAL;
 357        session_error_setg(errp, s, "unknown error matching the host key"
 358                      " with known_hosts (%d)", r);
 359        goto out;
 360    }
 361
 362    /* known_hosts checking successful. */
 363    ret = 0;
 364
 365 out:
 366    if (knh != NULL) {
 367        libssh2_knownhost_free(knh);
 368    }
 369    g_free(knh_file);
 370    return ret;
 371}
 372
 373static unsigned hex2decimal(char ch)
 374{
 375    if (ch >= '0' && ch <= '9') {
 376        return (ch - '0');
 377    } else if (ch >= 'a' && ch <= 'f') {
 378        return 10 + (ch - 'a');
 379    } else if (ch >= 'A' && ch <= 'F') {
 380        return 10 + (ch - 'A');
 381    }
 382
 383    return -1;
 384}
 385
 386/* Compare the binary fingerprint (hash of host key) with the
 387 * host_key_check parameter.
 388 */
 389static int compare_fingerprint(const unsigned char *fingerprint, size_t len,
 390                               const char *host_key_check)
 391{
 392    unsigned c;
 393
 394    while (len > 0) {
 395        while (*host_key_check == ':')
 396            host_key_check++;
 397        if (!qemu_isxdigit(host_key_check[0]) ||
 398            !qemu_isxdigit(host_key_check[1]))
 399            return 1;
 400        c = hex2decimal(host_key_check[0]) * 16 +
 401            hex2decimal(host_key_check[1]);
 402        if (c - *fingerprint != 0)
 403            return c - *fingerprint;
 404        fingerprint++;
 405        len--;
 406        host_key_check += 2;
 407    }
 408    return *host_key_check - '\0';
 409}
 410
 411static int
 412check_host_key_hash(BDRVSSHState *s, const char *hash,
 413                    int hash_type, size_t fingerprint_len, Error **errp)
 414{
 415    const char *fingerprint;
 416
 417    fingerprint = libssh2_hostkey_hash(s->session, hash_type);
 418    if (!fingerprint) {
 419        session_error_setg(errp, s, "failed to read remote host key");
 420        return -EINVAL;
 421    }
 422
 423    if(compare_fingerprint((unsigned char *) fingerprint, fingerprint_len,
 424                           hash) != 0) {
 425        error_setg(errp, "remote host key does not match host_key_check '%s'",
 426                   hash);
 427        return -EPERM;
 428    }
 429
 430    return 0;
 431}
 432
 433static int check_host_key(BDRVSSHState *s, const char *host, int port,
 434                          SshHostKeyCheck *hkc, Error **errp)
 435{
 436    SshHostKeyCheckMode mode;
 437
 438    if (hkc) {
 439        mode = hkc->mode;
 440    } else {
 441        mode = SSH_HOST_KEY_CHECK_MODE_KNOWN_HOSTS;
 442    }
 443
 444    switch (mode) {
 445    case SSH_HOST_KEY_CHECK_MODE_NONE:
 446        return 0;
 447    case SSH_HOST_KEY_CHECK_MODE_HASH:
 448        if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_MD5) {
 449            return check_host_key_hash(s, hkc->u.hash.hash,
 450                                       LIBSSH2_HOSTKEY_HASH_MD5, 16, errp);
 451        } else if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_SHA1) {
 452            return check_host_key_hash(s, hkc->u.hash.hash,
 453                                       LIBSSH2_HOSTKEY_HASH_SHA1, 20, errp);
 454        }
 455        g_assert_not_reached();
 456        break;
 457    case SSH_HOST_KEY_CHECK_MODE_KNOWN_HOSTS:
 458        return check_host_key_knownhosts(s, host, port, errp);
 459    default:
 460        g_assert_not_reached();
 461    }
 462
 463    return -EINVAL;
 464}
 465
 466static int authenticate(BDRVSSHState *s, const char *user, Error **errp)
 467{
 468    int r, ret;
 469    const char *userauthlist;
 470    LIBSSH2_AGENT *agent = NULL;
 471    struct libssh2_agent_publickey *identity;
 472    struct libssh2_agent_publickey *prev_identity = NULL;
 473
 474    userauthlist = libssh2_userauth_list(s->session, user, strlen(user));
 475    if (strstr(userauthlist, "publickey") == NULL) {
 476        ret = -EPERM;
 477        error_setg(errp,
 478                "remote server does not support \"publickey\" authentication");
 479        goto out;
 480    }
 481
 482    /* Connect to ssh-agent and try each identity in turn. */
 483    agent = libssh2_agent_init(s->session);
 484    if (!agent) {
 485        ret = -EINVAL;
 486        session_error_setg(errp, s, "failed to initialize ssh-agent support");
 487        goto out;
 488    }
 489    if (libssh2_agent_connect(agent)) {
 490        ret = -ECONNREFUSED;
 491        session_error_setg(errp, s, "failed to connect to ssh-agent");
 492        goto out;
 493    }
 494    if (libssh2_agent_list_identities(agent)) {
 495        ret = -EINVAL;
 496        session_error_setg(errp, s,
 497                           "failed requesting identities from ssh-agent");
 498        goto out;
 499    }
 500
 501    for(;;) {
 502        r = libssh2_agent_get_identity(agent, &identity, prev_identity);
 503        if (r == 1) {           /* end of list */
 504            break;
 505        }
 506        if (r < 0) {
 507            ret = -EINVAL;
 508            session_error_setg(errp, s,
 509                               "failed to obtain identity from ssh-agent");
 510            goto out;
 511        }
 512        r = libssh2_agent_userauth(agent, user, identity);
 513        if (r == 0) {
 514            /* Authenticated! */
 515            ret = 0;
 516            goto out;
 517        }
 518        /* Failed to authenticate with this identity, try the next one. */
 519        prev_identity = identity;
 520    }
 521
 522    ret = -EPERM;
 523    error_setg(errp, "failed to authenticate using publickey authentication "
 524               "and the identities held by your ssh-agent");
 525
 526 out:
 527    if (agent != NULL) {
 528        /* Note: libssh2 implementation implicitly calls
 529         * libssh2_agent_disconnect if necessary.
 530         */
 531        libssh2_agent_free(agent);
 532    }
 533
 534    return ret;
 535}
 536
 537static QemuOptsList ssh_runtime_opts = {
 538    .name = "ssh",
 539    .head = QTAILQ_HEAD_INITIALIZER(ssh_runtime_opts.head),
 540    .desc = {
 541        {
 542            .name = "host",
 543            .type = QEMU_OPT_STRING,
 544            .help = "Host to connect to",
 545        },
 546        {
 547            .name = "port",
 548            .type = QEMU_OPT_NUMBER,
 549            .help = "Port to connect to",
 550        },
 551        {
 552            .name = "host_key_check",
 553            .type = QEMU_OPT_STRING,
 554            .help = "Defines how and what to check the host key against",
 555        },
 556        { /* end of list */ }
 557    },
 558};
 559
 560static bool ssh_process_legacy_options(QDict *output_opts,
 561                                       QemuOpts *legacy_opts,
 562                                       Error **errp)
 563{
 564    const char *host = qemu_opt_get(legacy_opts, "host");
 565    const char *port = qemu_opt_get(legacy_opts, "port");
 566    const char *host_key_check = qemu_opt_get(legacy_opts, "host_key_check");
 567
 568    if (!host && port) {
 569        error_setg(errp, "port may not be used without host");
 570        return false;
 571    }
 572
 573    if (host) {
 574        qdict_put_str(output_opts, "server.host", host);
 575        qdict_put_str(output_opts, "server.port", port ?: stringify(22));
 576    }
 577
 578    if (host_key_check) {
 579        if (strcmp(host_key_check, "no") == 0) {
 580            qdict_put_str(output_opts, "host-key-check.mode", "none");
 581        } else if (strncmp(host_key_check, "md5:", 4) == 0) {
 582            qdict_put_str(output_opts, "host-key-check.mode", "hash");
 583            qdict_put_str(output_opts, "host-key-check.type", "md5");
 584            qdict_put_str(output_opts, "host-key-check.hash",
 585                          &host_key_check[4]);
 586        } else if (strncmp(host_key_check, "sha1:", 5) == 0) {
 587            qdict_put_str(output_opts, "host-key-check.mode", "hash");
 588            qdict_put_str(output_opts, "host-key-check.type", "sha1");
 589            qdict_put_str(output_opts, "host-key-check.hash",
 590                          &host_key_check[5]);
 591        } else if (strcmp(host_key_check, "yes") == 0) {
 592            qdict_put_str(output_opts, "host-key-check.mode", "known_hosts");
 593        } else {
 594            error_setg(errp, "unknown host_key_check setting (%s)",
 595                       host_key_check);
 596            return false;
 597        }
 598    }
 599
 600    return true;
 601}
 602
 603static BlockdevOptionsSsh *ssh_parse_options(QDict *options, Error **errp)
 604{
 605    BlockdevOptionsSsh *result = NULL;
 606    QemuOpts *opts = NULL;
 607    Error *local_err = NULL;
 608    QObject *crumpled;
 609    const QDictEntry *e;
 610    Visitor *v;
 611
 612    /* Translate legacy options */
 613    opts = qemu_opts_create(&ssh_runtime_opts, NULL, 0, &error_abort);
 614    qemu_opts_absorb_qdict(opts, options, &local_err);
 615    if (local_err) {
 616        error_propagate(errp, local_err);
 617        goto fail;
 618    }
 619
 620    if (!ssh_process_legacy_options(options, opts, errp)) {
 621        goto fail;
 622    }
 623
 624    /* Create the QAPI object */
 625    crumpled = qdict_crumple(options, errp);
 626    if (crumpled == NULL) {
 627        goto fail;
 628    }
 629
 630    /*
 631     * FIXME .numeric, .to, .ipv4 or .ipv6 don't work with -drive.
 632     * .to doesn't matter, it's ignored anyway.
 633     * That's because when @options come from -blockdev or
 634     * blockdev_add, members are typed according to the QAPI schema,
 635     * but when they come from -drive, they're all QString.  The
 636     * visitor expects the former.
 637     */
 638    v = qobject_input_visitor_new(crumpled);
 639    visit_type_BlockdevOptionsSsh(v, NULL, &result, &local_err);
 640    visit_free(v);
 641    qobject_decref(crumpled);
 642
 643    if (local_err) {
 644        error_propagate(errp, local_err);
 645        goto fail;
 646    }
 647
 648    /* Remove the processed options from the QDict (the visitor processes
 649     * _all_ options in the QDict) */
 650    while ((e = qdict_first(options))) {
 651        qdict_del(options, e->key);
 652    }
 653
 654fail:
 655    qemu_opts_del(opts);
 656    return result;
 657}
 658
 659static int connect_to_ssh(BDRVSSHState *s, BlockdevOptionsSsh *opts,
 660                          int ssh_flags, int creat_mode, Error **errp)
 661{
 662    int r, ret;
 663    const char *user;
 664    long port = 0;
 665
 666    if (opts->has_user) {
 667        user = opts->user;
 668    } else {
 669        user = g_get_user_name();
 670        if (!user) {
 671            error_setg_errno(errp, errno, "Can't get user name");
 672            ret = -errno;
 673            goto err;
 674        }
 675    }
 676
 677    /* Pop the config into our state object, Exit if invalid */
 678    s->inet = opts->server;
 679    opts->server = NULL;
 680
 681    if (qemu_strtol(s->inet->port, NULL, 10, &port) < 0) {
 682        error_setg(errp, "Use only numeric port value");
 683        ret = -EINVAL;
 684        goto err;
 685    }
 686
 687    /* Open the socket and connect. */
 688    s->sock = inet_connect_saddr(s->inet, errp);
 689    if (s->sock < 0) {
 690        ret = -EIO;
 691        goto err;
 692    }
 693
 694    /* Create SSH session. */
 695    s->session = libssh2_session_init();
 696    if (!s->session) {
 697        ret = -EINVAL;
 698        session_error_setg(errp, s, "failed to initialize libssh2 session");
 699        goto err;
 700    }
 701
 702#if TRACE_LIBSSH2 != 0
 703    libssh2_trace(s->session, TRACE_LIBSSH2);
 704#endif
 705
 706    r = libssh2_session_handshake(s->session, s->sock);
 707    if (r != 0) {
 708        ret = -EINVAL;
 709        session_error_setg(errp, s, "failed to establish SSH session");
 710        goto err;
 711    }
 712
 713    /* Check the remote host's key against known_hosts. */
 714    ret = check_host_key(s, s->inet->host, port, opts->host_key_check, errp);
 715    if (ret < 0) {
 716        goto err;
 717    }
 718
 719    /* Authenticate. */
 720    ret = authenticate(s, user, errp);
 721    if (ret < 0) {
 722        goto err;
 723    }
 724
 725    /* Start SFTP. */
 726    s->sftp = libssh2_sftp_init(s->session);
 727    if (!s->sftp) {
 728        session_error_setg(errp, s, "failed to initialize sftp handle");
 729        ret = -EINVAL;
 730        goto err;
 731    }
 732
 733    /* Open the remote file. */
 734    DPRINTF("opening file %s flags=0x%x creat_mode=0%o",
 735            opts->path, ssh_flags, creat_mode);
 736    s->sftp_handle = libssh2_sftp_open(s->sftp, opts->path, ssh_flags,
 737                                       creat_mode);
 738    if (!s->sftp_handle) {
 739        session_error_setg(errp, s, "failed to open remote file '%s'",
 740                           opts->path);
 741        ret = -EINVAL;
 742        goto err;
 743    }
 744
 745    r = libssh2_sftp_fstat(s->sftp_handle, &s->attrs);
 746    if (r < 0) {
 747        sftp_error_setg(errp, s, "failed to read file attributes");
 748        return -EINVAL;
 749    }
 750
 751    return 0;
 752
 753 err:
 754    if (s->sftp_handle) {
 755        libssh2_sftp_close(s->sftp_handle);
 756    }
 757    s->sftp_handle = NULL;
 758    if (s->sftp) {
 759        libssh2_sftp_shutdown(s->sftp);
 760    }
 761    s->sftp = NULL;
 762    if (s->session) {
 763        libssh2_session_disconnect(s->session,
 764                                   "from qemu ssh client: "
 765                                   "error opening connection");
 766        libssh2_session_free(s->session);
 767    }
 768    s->session = NULL;
 769
 770    return ret;
 771}
 772
 773static int ssh_file_open(BlockDriverState *bs, QDict *options, int bdrv_flags,
 774                         Error **errp)
 775{
 776    BDRVSSHState *s = bs->opaque;
 777    BlockdevOptionsSsh *opts;
 778    int ret;
 779    int ssh_flags;
 780
 781    ssh_state_init(s);
 782
 783    ssh_flags = LIBSSH2_FXF_READ;
 784    if (bdrv_flags & BDRV_O_RDWR) {
 785        ssh_flags |= LIBSSH2_FXF_WRITE;
 786    }
 787
 788    opts = ssh_parse_options(options, errp);
 789    if (opts == NULL) {
 790        return -EINVAL;
 791    }
 792
 793    /* Start up SSH. */
 794    ret = connect_to_ssh(s, opts, ssh_flags, 0, errp);
 795    if (ret < 0) {
 796        goto err;
 797    }
 798
 799    /* Go non-blocking. */
 800    libssh2_session_set_blocking(s->session, 0);
 801
 802    qapi_free_BlockdevOptionsSsh(opts);
 803
 804    return 0;
 805
 806 err:
 807    if (s->sock >= 0) {
 808        close(s->sock);
 809    }
 810    s->sock = -1;
 811
 812    qapi_free_BlockdevOptionsSsh(opts);
 813
 814    return ret;
 815}
 816
 817/* Note: This is a blocking operation */
 818static int ssh_grow_file(BDRVSSHState *s, int64_t offset, Error **errp)
 819{
 820    ssize_t ret;
 821    char c[1] = { '\0' };
 822    int was_blocking = libssh2_session_get_blocking(s->session);
 823
 824    /* offset must be strictly greater than the current size so we do
 825     * not overwrite anything */
 826    assert(offset > 0 && offset > s->attrs.filesize);
 827
 828    libssh2_session_set_blocking(s->session, 1);
 829
 830    libssh2_sftp_seek64(s->sftp_handle, offset - 1);
 831    ret = libssh2_sftp_write(s->sftp_handle, c, 1);
 832
 833    libssh2_session_set_blocking(s->session, was_blocking);
 834
 835    if (ret < 0) {
 836        sftp_error_setg(errp, s, "Failed to grow file");
 837        return -EIO;
 838    }
 839
 840    s->attrs.filesize = offset;
 841    return 0;
 842}
 843
 844static QemuOptsList ssh_create_opts = {
 845    .name = "ssh-create-opts",
 846    .head = QTAILQ_HEAD_INITIALIZER(ssh_create_opts.head),
 847    .desc = {
 848        {
 849            .name = BLOCK_OPT_SIZE,
 850            .type = QEMU_OPT_SIZE,
 851            .help = "Virtual disk size"
 852        },
 853        { /* end of list */ }
 854    }
 855};
 856
 857static int ssh_co_create(BlockdevCreateOptions *options, Error **errp)
 858{
 859    BlockdevCreateOptionsSsh *opts = &options->u.ssh;
 860    BDRVSSHState s;
 861    int ret;
 862
 863    assert(options->driver == BLOCKDEV_DRIVER_SSH);
 864
 865    ssh_state_init(&s);
 866
 867    ret = connect_to_ssh(&s, opts->location,
 868                         LIBSSH2_FXF_READ|LIBSSH2_FXF_WRITE|
 869                         LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC,
 870                         0644, errp);
 871    if (ret < 0) {
 872        goto fail;
 873    }
 874
 875    if (opts->size > 0) {
 876        ret = ssh_grow_file(&s, opts->size, errp);
 877        if (ret < 0) {
 878            goto fail;
 879        }
 880    }
 881
 882    ret = 0;
 883fail:
 884    ssh_state_free(&s);
 885    return ret;
 886}
 887
 888static int coroutine_fn ssh_co_create_opts(const char *filename, QemuOpts *opts,
 889                                           Error **errp)
 890{
 891    BlockdevCreateOptions *create_options;
 892    BlockdevCreateOptionsSsh *ssh_opts;
 893    int ret;
 894    QDict *uri_options = NULL;
 895
 896    create_options = g_new0(BlockdevCreateOptions, 1);
 897    create_options->driver = BLOCKDEV_DRIVER_SSH;
 898    ssh_opts = &create_options->u.ssh;
 899
 900    /* Get desired file size. */
 901    ssh_opts->size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
 902                              BDRV_SECTOR_SIZE);
 903    DPRINTF("total_size=%" PRIi64, ssh_opts->size);
 904
 905    uri_options = qdict_new();
 906    ret = parse_uri(filename, uri_options, errp);
 907    if (ret < 0) {
 908        goto out;
 909    }
 910
 911    ssh_opts->location = ssh_parse_options(uri_options, errp);
 912    if (ssh_opts->location == NULL) {
 913        ret = -EINVAL;
 914        goto out;
 915    }
 916
 917    ret = ssh_co_create(create_options, errp);
 918
 919 out:
 920    QDECREF(uri_options);
 921    qapi_free_BlockdevCreateOptions(create_options);
 922    return ret;
 923}
 924
 925static void ssh_close(BlockDriverState *bs)
 926{
 927    BDRVSSHState *s = bs->opaque;
 928
 929    ssh_state_free(s);
 930}
 931
 932static int ssh_has_zero_init(BlockDriverState *bs)
 933{
 934    BDRVSSHState *s = bs->opaque;
 935    /* Assume false, unless we can positively prove it's true. */
 936    int has_zero_init = 0;
 937
 938    if (s->attrs.flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
 939        if (s->attrs.permissions & LIBSSH2_SFTP_S_IFREG) {
 940            has_zero_init = 1;
 941        }
 942    }
 943
 944    return has_zero_init;
 945}
 946
 947typedef struct BDRVSSHRestart {
 948    BlockDriverState *bs;
 949    Coroutine *co;
 950} BDRVSSHRestart;
 951
 952static void restart_coroutine(void *opaque)
 953{
 954    BDRVSSHRestart *restart = opaque;
 955    BlockDriverState *bs = restart->bs;
 956    BDRVSSHState *s = bs->opaque;
 957    AioContext *ctx = bdrv_get_aio_context(bs);
 958
 959    DPRINTF("co=%p", restart->co);
 960    aio_set_fd_handler(ctx, s->sock, false, NULL, NULL, NULL, NULL);
 961
 962    aio_co_wake(restart->co);
 963}
 964
 965/* A non-blocking call returned EAGAIN, so yield, ensuring the
 966 * handlers are set up so that we'll be rescheduled when there is an
 967 * interesting event on the socket.
 968 */
 969static coroutine_fn void co_yield(BDRVSSHState *s, BlockDriverState *bs)
 970{
 971    int r;
 972    IOHandler *rd_handler = NULL, *wr_handler = NULL;
 973    BDRVSSHRestart restart = {
 974        .bs = bs,
 975        .co = qemu_coroutine_self()
 976    };
 977
 978    r = libssh2_session_block_directions(s->session);
 979
 980    if (r & LIBSSH2_SESSION_BLOCK_INBOUND) {
 981        rd_handler = restart_coroutine;
 982    }
 983    if (r & LIBSSH2_SESSION_BLOCK_OUTBOUND) {
 984        wr_handler = restart_coroutine;
 985    }
 986
 987    DPRINTF("s->sock=%d rd_handler=%p wr_handler=%p", s->sock,
 988            rd_handler, wr_handler);
 989
 990    aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock,
 991                       false, rd_handler, wr_handler, NULL, &restart);
 992    qemu_coroutine_yield();
 993    DPRINTF("s->sock=%d - back", s->sock);
 994}
 995
 996/* SFTP has a function `libssh2_sftp_seek64' which seeks to a position
 997 * in the remote file.  Notice that it just updates a field in the
 998 * sftp_handle structure, so there is no network traffic and it cannot
 999 * fail.
1000 *
1001 * However, `libssh2_sftp_seek64' does have a catastrophic effect on
1002 * performance since it causes the handle to throw away all in-flight
1003 * reads and buffered readahead data.  Therefore this function tries
1004 * to be intelligent about when to call the underlying libssh2 function.
1005 */
1006#define SSH_SEEK_WRITE 0
1007#define SSH_SEEK_READ  1
1008#define SSH_SEEK_FORCE 2
1009
1010static void ssh_seek(BDRVSSHState *s, int64_t offset, int flags)
1011{
1012    bool op_read = (flags & SSH_SEEK_READ) != 0;
1013    bool force = (flags & SSH_SEEK_FORCE) != 0;
1014
1015    if (force || op_read != s->offset_op_read || offset != s->offset) {
1016        DPRINTF("seeking to offset=%" PRIi64, offset);
1017        libssh2_sftp_seek64(s->sftp_handle, offset);
1018        s->offset = offset;
1019        s->offset_op_read = op_read;
1020    }
1021}
1022
1023static coroutine_fn int ssh_read(BDRVSSHState *s, BlockDriverState *bs,
1024                                 int64_t offset, size_t size,
1025                                 QEMUIOVector *qiov)
1026{
1027    ssize_t r;
1028    size_t got;
1029    char *buf, *end_of_vec;
1030    struct iovec *i;
1031
1032    DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
1033
1034    ssh_seek(s, offset, SSH_SEEK_READ);
1035
1036    /* This keeps track of the current iovec element ('i'), where we
1037     * will write to next ('buf'), and the end of the current iovec
1038     * ('end_of_vec').
1039     */
1040    i = &qiov->iov[0];
1041    buf = i->iov_base;
1042    end_of_vec = i->iov_base + i->iov_len;
1043
1044    /* libssh2 has a hard-coded limit of 2000 bytes per request,
1045     * although it will also do readahead behind our backs.  Therefore
1046     * we may have to do repeated reads here until we have read 'size'
1047     * bytes.
1048     */
1049    for (got = 0; got < size; ) {
1050    again:
1051        DPRINTF("sftp_read buf=%p size=%zu", buf, end_of_vec - buf);
1052        r = libssh2_sftp_read(s->sftp_handle, buf, end_of_vec - buf);
1053        DPRINTF("sftp_read returned %zd", r);
1054
1055        if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
1056            co_yield(s, bs);
1057            goto again;
1058        }
1059        if (r < 0) {
1060            sftp_error_report(s, "read failed");
1061            s->offset = -1;
1062            return -EIO;
1063        }
1064        if (r == 0) {
1065            /* EOF: Short read so pad the buffer with zeroes and return it. */
1066            qemu_iovec_memset(qiov, got, 0, size - got);
1067            return 0;
1068        }
1069
1070        got += r;
1071        buf += r;
1072        s->offset += r;
1073        if (buf >= end_of_vec && got < size) {
1074            i++;
1075            buf = i->iov_base;
1076            end_of_vec = i->iov_base + i->iov_len;
1077        }
1078    }
1079
1080    return 0;
1081}
1082
1083static coroutine_fn int ssh_co_readv(BlockDriverState *bs,
1084                                     int64_t sector_num,
1085                                     int nb_sectors, QEMUIOVector *qiov)
1086{
1087    BDRVSSHState *s = bs->opaque;
1088    int ret;
1089
1090    qemu_co_mutex_lock(&s->lock);
1091    ret = ssh_read(s, bs, sector_num * BDRV_SECTOR_SIZE,
1092                   nb_sectors * BDRV_SECTOR_SIZE, qiov);
1093    qemu_co_mutex_unlock(&s->lock);
1094
1095    return ret;
1096}
1097
1098static int ssh_write(BDRVSSHState *s, BlockDriverState *bs,
1099                     int64_t offset, size_t size,
1100                     QEMUIOVector *qiov)
1101{
1102    ssize_t r;
1103    size_t written;
1104    char *buf, *end_of_vec;
1105    struct iovec *i;
1106
1107    DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
1108
1109    ssh_seek(s, offset, SSH_SEEK_WRITE);
1110
1111    /* This keeps track of the current iovec element ('i'), where we
1112     * will read from next ('buf'), and the end of the current iovec
1113     * ('end_of_vec').
1114     */
1115    i = &qiov->iov[0];
1116    buf = i->iov_base;
1117    end_of_vec = i->iov_base + i->iov_len;
1118
1119    for (written = 0; written < size; ) {
1120    again:
1121        DPRINTF("sftp_write buf=%p size=%zu", buf, end_of_vec - buf);
1122        r = libssh2_sftp_write(s->sftp_handle, buf, end_of_vec - buf);
1123        DPRINTF("sftp_write returned %zd", r);
1124
1125        if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
1126            co_yield(s, bs);
1127            goto again;
1128        }
1129        if (r < 0) {
1130            sftp_error_report(s, "write failed");
1131            s->offset = -1;
1132            return -EIO;
1133        }
1134        /* The libssh2 API is very unclear about this.  A comment in
1135         * the code says "nothing was acked, and no EAGAIN was
1136         * received!" which apparently means that no data got sent
1137         * out, and the underlying channel didn't return any EAGAIN
1138         * indication.  I think this is a bug in either libssh2 or
1139         * OpenSSH (server-side).  In any case, forcing a seek (to
1140         * discard libssh2 internal buffers), and then trying again
1141         * works for me.
1142         */
1143        if (r == 0) {
1144            ssh_seek(s, offset + written, SSH_SEEK_WRITE|SSH_SEEK_FORCE);
1145            co_yield(s, bs);
1146            goto again;
1147        }
1148
1149        written += r;
1150        buf += r;
1151        s->offset += r;
1152        if (buf >= end_of_vec && written < size) {
1153            i++;
1154            buf = i->iov_base;
1155            end_of_vec = i->iov_base + i->iov_len;
1156        }
1157
1158        if (offset + written > s->attrs.filesize)
1159            s->attrs.filesize = offset + written;
1160    }
1161
1162    return 0;
1163}
1164
1165static coroutine_fn int ssh_co_writev(BlockDriverState *bs,
1166                                      int64_t sector_num,
1167                                      int nb_sectors, QEMUIOVector *qiov)
1168{
1169    BDRVSSHState *s = bs->opaque;
1170    int ret;
1171
1172    qemu_co_mutex_lock(&s->lock);
1173    ret = ssh_write(s, bs, sector_num * BDRV_SECTOR_SIZE,
1174                    nb_sectors * BDRV_SECTOR_SIZE, qiov);
1175    qemu_co_mutex_unlock(&s->lock);
1176
1177    return ret;
1178}
1179
1180static void unsafe_flush_warning(BDRVSSHState *s, const char *what)
1181{
1182    if (!s->unsafe_flush_warning) {
1183        warn_report("ssh server %s does not support fsync",
1184                    s->inet->host);
1185        if (what) {
1186            error_report("to support fsync, you need %s", what);
1187        }
1188        s->unsafe_flush_warning = true;
1189    }
1190}
1191
1192#ifdef HAS_LIBSSH2_SFTP_FSYNC
1193
1194static coroutine_fn int ssh_flush(BDRVSSHState *s, BlockDriverState *bs)
1195{
1196    int r;
1197
1198    DPRINTF("fsync");
1199 again:
1200    r = libssh2_sftp_fsync(s->sftp_handle);
1201    if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
1202        co_yield(s, bs);
1203        goto again;
1204    }
1205    if (r == LIBSSH2_ERROR_SFTP_PROTOCOL &&
1206        libssh2_sftp_last_error(s->sftp) == LIBSSH2_FX_OP_UNSUPPORTED) {
1207        unsafe_flush_warning(s, "OpenSSH >= 6.3");
1208        return 0;
1209    }
1210    if (r < 0) {
1211        sftp_error_report(s, "fsync failed");
1212        return -EIO;
1213    }
1214
1215    return 0;
1216}
1217
1218static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
1219{
1220    BDRVSSHState *s = bs->opaque;
1221    int ret;
1222
1223    qemu_co_mutex_lock(&s->lock);
1224    ret = ssh_flush(s, bs);
1225    qemu_co_mutex_unlock(&s->lock);
1226
1227    return ret;
1228}
1229
1230#else /* !HAS_LIBSSH2_SFTP_FSYNC */
1231
1232static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
1233{
1234    BDRVSSHState *s = bs->opaque;
1235
1236    unsafe_flush_warning(s, "libssh2 >= 1.4.4");
1237    return 0;
1238}
1239
1240#endif /* !HAS_LIBSSH2_SFTP_FSYNC */
1241
1242static int64_t ssh_getlength(BlockDriverState *bs)
1243{
1244    BDRVSSHState *s = bs->opaque;
1245    int64_t length;
1246
1247    /* Note we cannot make a libssh2 call here. */
1248    length = (int64_t) s->attrs.filesize;
1249    DPRINTF("length=%" PRIi64, length);
1250
1251    return length;
1252}
1253
1254static int ssh_truncate(BlockDriverState *bs, int64_t offset,
1255                        PreallocMode prealloc, Error **errp)
1256{
1257    BDRVSSHState *s = bs->opaque;
1258
1259    if (prealloc != PREALLOC_MODE_OFF) {
1260        error_setg(errp, "Unsupported preallocation mode '%s'",
1261                   PreallocMode_str(prealloc));
1262        return -ENOTSUP;
1263    }
1264
1265    if (offset < s->attrs.filesize) {
1266        error_setg(errp, "ssh driver does not support shrinking files");
1267        return -ENOTSUP;
1268    }
1269
1270    if (offset == s->attrs.filesize) {
1271        return 0;
1272    }
1273
1274    return ssh_grow_file(s, offset, errp);
1275}
1276
1277static BlockDriver bdrv_ssh = {
1278    .format_name                  = "ssh",
1279    .protocol_name                = "ssh",
1280    .instance_size                = sizeof(BDRVSSHState),
1281    .bdrv_parse_filename          = ssh_parse_filename,
1282    .bdrv_file_open               = ssh_file_open,
1283    .bdrv_co_create               = ssh_co_create,
1284    .bdrv_co_create_opts          = ssh_co_create_opts,
1285    .bdrv_close                   = ssh_close,
1286    .bdrv_has_zero_init           = ssh_has_zero_init,
1287    .bdrv_co_readv                = ssh_co_readv,
1288    .bdrv_co_writev               = ssh_co_writev,
1289    .bdrv_getlength               = ssh_getlength,
1290    .bdrv_truncate                = ssh_truncate,
1291    .bdrv_co_flush_to_disk        = ssh_co_flush,
1292    .create_opts                  = &ssh_create_opts,
1293};
1294
1295static void bdrv_ssh_init(void)
1296{
1297    int r;
1298
1299    r = libssh2_init(0);
1300    if (r != 0) {
1301        fprintf(stderr, "libssh2 initialization failed, %d\n", r);
1302        exit(EXIT_FAILURE);
1303    }
1304
1305    bdrv_register(&bdrv_ssh);
1306}
1307
1308block_init(bdrv_ssh_init);
1309