block/ssh.c

   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 <stdio.h>
  26 #include <stdlib.h>
  27 #include <stdarg.h>
  28
  29 #include <libssh2.h>
  30 #include <libssh2_sftp.h>
  31
  32 #include "block/block_int.h"
  33 #include "qemu/sockets.h"
  34 #include "qemu/uri.h"
  35 #include "qapi/qmp/qint.h"
  36
  37 /* DEBUG_SSH=1 enables the DPRINTF (debugging printf) statements in
  38  * this block driver code.
  39  *
  40  * TRACE_LIBSSH2=<bitmask> enables tracing in libssh2 itself.  Note
  41  * that this requires that libssh2 was specially compiled with the
  42  * `./configure --enable-debug' option, so most likely you will have
  43  * to compile it yourself.  The meaning of <bitmask> is described
  44  * here: http://www.libssh2.org/libssh2_trace.html
  45  */
  46 #define DEBUG_SSH     0
  47 #define TRACE_LIBSSH2 0 /* or try: LIBSSH2_TRACE_SFTP */
  48
  49 #define DPRINTF(fmt, ...)                           \
  50     do {                                            \
  51         if (DEBUG_SSH) {                            \
  52             fprintf(stderr, "ssh: %-15s " fmt "\n", \
  53                     __func__, ##__VA_ARGS__);       \
  54         }                                           \
  55     } while (0)
  56
  57 typedef struct BDRVSSHState {
  58     /* Coroutine. */
  59     CoMutex lock;
  60
  61     /* SSH connection. */
  62     int sock;                         /* socket */
  63     LIBSSH2_SESSION *session;         /* ssh session */
  64     LIBSSH2_SFTP *sftp;               /* sftp session */
  65     LIBSSH2_SFTP_HANDLE *sftp_handle; /* sftp remote file handle */
  66
  67     /* See ssh_seek() function below. */
  68     int64_t offset;
  69     bool offset_op_read;
  70
  71     /* File attributes at open.  We try to keep the .filesize field
  72      * updated if it changes (eg by writing at the end of the file).
  73      */
  74     LIBSSH2_SFTP_ATTRIBUTES attrs;
  75
  76     /* Used to warn if 'flush' is not supported. */
  77     char *hostport;
  78     bool unsafe_flush_warning;
  79 } BDRVSSHState;
  80
  81 static void ssh_state_init(BDRVSSHState *s)
  82 {
  83     memset(s, 0, sizeof *s);
  84     s->sock = -1;
  85     s->offset = -1;
  86     qemu_co_mutex_init(&s->lock);
  87 }
  88
  89 static void ssh_state_free(BDRVSSHState *s)
  90 {
  91     g_free(s->hostport);
  92     if (s->sftp_handle) {
  93         libssh2_sftp_close(s->sftp_handle);
  94     }
  95     if (s->sftp) {
  96         libssh2_sftp_shutdown(s->sftp);
  97     }
  98     if (s->session) {
  99         libssh2_session_disconnect(s->session,
 100                                    "from qemu ssh client: "
 101                                    "user closed the connection");
 102         libssh2_session_free(s->session);
 103     }
 104     if (s->sock >= 0) {
 105         close(s->sock);
 106     }
 107 }
 108
 109 static void GCC_FMT_ATTR(3, 4)
 110 session_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
 111 {
 112     va_list args;
 113     char *msg;
 114
 115     va_start(args, fs);
 116     msg = g_strdup_vprintf(fs, args);
 117     va_end(args);
 118
 119     if (s->session) {
 120         char *ssh_err;
 121         int ssh_err_code;
 122
 123         /* This is not an errno.  See <libssh2.h>. */
 124         ssh_err_code = libssh2_session_last_error(s->session,
 125                                                   &ssh_err, NULL, 0);
 126         error_setg(errp, "%s: %s (libssh2 error code: %d)",
 127                    msg, ssh_err, ssh_err_code);
 128     } else {
 129         error_setg(errp, "%s", msg);
 130     }
 131     g_free(msg);
 132 }
 133
 134 static void GCC_FMT_ATTR(3, 4)
 135 sftp_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
 136 {
 137     va_list args;
 138     char *msg;
 139
 140     va_start(args, fs);
 141     msg = g_strdup_vprintf(fs, args);
 142     va_end(args);
 143
 144     if (s->sftp) {
 145         char *ssh_err;
 146         int ssh_err_code;
 147         unsigned long sftp_err_code;
 148
 149         /* This is not an errno.  See <libssh2.h>. */
 150         ssh_err_code = libssh2_session_last_error(s->session,
 151                                                   &ssh_err, NULL, 0);
 152         /* See <libssh2_sftp.h>. */
 153         sftp_err_code = libssh2_sftp_last_error((s)->sftp);
 154
 155         error_setg(errp,
 156                    "%s: %s (libssh2 error code: %d, sftp error code: %lu)",
 157                    msg, ssh_err, ssh_err_code, sftp_err_code);
 158     } else {
 159         error_setg(errp, "%s", msg);
 160     }
 161     g_free(msg);
 162 }
 163
 164 static void GCC_FMT_ATTR(2, 3)
 165 sftp_error_report(BDRVSSHState *s, const char *fs, ...)
 166 {
 167     va_list args;
 168
 169     va_start(args, fs);
 170     error_vprintf(fs, args);
 171
 172     if ((s)->sftp) {
 173         char *ssh_err;
 174         int ssh_err_code;
 175         unsigned long sftp_err_code;
 176
 177         /* This is not an errno.  See <libssh2.h>. */
 178         ssh_err_code = libssh2_session_last_error(s->session,
 179                                                   &ssh_err, NULL, 0);
 180         /* See <libssh2_sftp.h>. */
 181         sftp_err_code = libssh2_sftp_last_error((s)->sftp);
 182
 183         error_printf(": %s (libssh2 error code: %d, sftp error code: %lu)",
 184                      ssh_err, ssh_err_code, sftp_err_code);
 185     }
 186
 187     va_end(args);
 188     error_printf("\n");
 189 }
 190
 191 static int parse_uri(const char *filename, QDict *options, Error **errp)
 192 {
 193     URI *uri = NULL;
 194     QueryParams *qp = NULL;
 195     int i;
 196
 197     uri = uri_parse(filename);
 198     if (!uri) {
 199         return -EINVAL;
 200     }
 201
 202     if (strcmp(uri->scheme, "ssh") != 0) {
 203         error_setg(errp, "URI scheme must be 'ssh'");
 204         goto err;
 205     }
 206
 207     if (!uri->server || strcmp(uri->server, "") == 0) {
 208         error_setg(errp, "missing hostname in URI");
 209         goto err;
 210     }
 211
 212     if (!uri->path || strcmp(uri->path, "") == 0) {
 213         error_setg(errp, "missing remote path in URI");
 214         goto err;
 215     }
 216
 217     qp = query_params_parse(uri->query);
 218     if (!qp) {
 219         error_setg(errp, "could not parse query parameters");
 220         goto err;
 221     }
 222
 223     if(uri->user && strcmp(uri->user, "") != 0) {
 224         qdict_put(options, "user", qstring_from_str(uri->user));
 225     }
 226
 227     qdict_put(options, "host", qstring_from_str(uri->server));
 228
 229     if (uri->port) {
 230         qdict_put(options, "port", qint_from_int(uri->port));
 231     }
 232
 233     qdict_put(options, "path", qstring_from_str(uri->path));
 234
 235     /* Pick out any query parameters that we understand, and ignore
 236      * the rest.
 237      */
 238     for (i = 0; i < qp->n; ++i) {
 239         if (strcmp(qp->p[i].name, "host_key_check") == 0) {
 240             qdict_put(options, "host_key_check",
 241                       qstring_from_str(qp->p[i].value));
 242         }
 243     }
 244
 245     query_params_free(qp);
 246     uri_free(uri);
 247     return 0;
 248
 249  err:
 250     if (qp) {
 251       query_params_free(qp);
 252     }
 253     if (uri) {
 254       uri_free(uri);
 255     }
 256     return -EINVAL;
 257 }
 258
 259 static void ssh_parse_filename(const char *filename, QDict *options,
 260                                Error **errp)
 261 {
 262     if (qdict_haskey(options, "user") ||
 263         qdict_haskey(options, "host") ||
 264         qdict_haskey(options, "port") ||
 265         qdict_haskey(options, "path") ||
 266         qdict_haskey(options, "host_key_check")) {
 267         error_setg(errp, "user, host, port, path, host_key_check cannot be used at the same time as a file option");
 268         return;
 269     }
 270
 271     parse_uri(filename, options, errp);
 272 }
 273
 274 static int check_host_key_knownhosts(BDRVSSHState *s,
 275                                      const char *host, int port, Error **errp)
 276 {
 277     const char *home;
 278     char *knh_file = NULL;
 279     LIBSSH2_KNOWNHOSTS *knh = NULL;
 280     struct libssh2_knownhost *found;
 281     int ret, r;
 282     const char *hostkey;
 283     size_t len;
 284     int type;
 285
 286     hostkey = libssh2_session_hostkey(s->session, &len, &type);
 287     if (!hostkey) {
 288         ret = -EINVAL;
 289         session_error_setg(errp, s, "failed to read remote host key");
 290         goto out;
 291     }
 292
 293     knh = libssh2_knownhost_init(s->session);
 294     if (!knh) {
 295         ret = -EINVAL;
 296         session_error_setg(errp, s,
 297                            "failed to initialize known hosts support");
 298         goto out;
 299     }
 300
 301     home = getenv("HOME");
 302     if (home) {
 303         knh_file = g_strdup_printf("%s/.ssh/known_hosts", home);
 304     } else {
 305         knh_file = g_strdup_printf("/root/.ssh/known_hosts");
 306     }
 307
 308     /* Read all known hosts from OpenSSH-style known_hosts file. */
 309     libssh2_knownhost_readfile(knh, knh_file, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
 310
 311     r = libssh2_knownhost_checkp(knh, host, port, hostkey, len,
 312                                  LIBSSH2_KNOWNHOST_TYPE_PLAIN|
 313                                  LIBSSH2_KNOWNHOST_KEYENC_RAW,
 314                                  &found);
 315     switch (r) {
 316     case LIBSSH2_KNOWNHOST_CHECK_MATCH:
 317         /* OK */
 318         DPRINTF("host key OK: %s", found->key);
 319         break;
 320     case LIBSSH2_KNOWNHOST_CHECK_MISMATCH:
 321         ret = -EINVAL;
 322         session_error_setg(errp, s,
 323                       "host key does not match the one in known_hosts"
 324                       " (found key %s)", found->key);
 325         goto out;
 326     case LIBSSH2_KNOWNHOST_CHECK_NOTFOUND:
 327         ret = -EINVAL;
 328         session_error_setg(errp, s, "no host key was found in known_hosts");
 329         goto out;
 330     case LIBSSH2_KNOWNHOST_CHECK_FAILURE:
 331         ret = -EINVAL;
 332         session_error_setg(errp, s,
 333                       "failure matching the host key with known_hosts");
 334         goto out;
 335     default:
 336         ret = -EINVAL;
 337         session_error_setg(errp, s, "unknown error matching the host key"
 338                       " with known_hosts (%d)", r);
 339         goto out;
 340     }
 341
 342     /* known_hosts checking successful. */
 343     ret = 0;
 344
 345  out:
 346     if (knh != NULL) {
 347         libssh2_knownhost_free(knh);
 348     }
 349     g_free(knh_file);
 350     return ret;
 351 }
 352
 353 static unsigned hex2decimal(char ch)
 354 {
 355     if (ch >= '0' && ch <= '9') {
 356         return (ch - '0');
 357     } else if (ch >= 'a' && ch <= 'f') {
 358         return 10 + (ch - 'a');
 359     } else if (ch >= 'A' && ch <= 'F') {
 360         return 10 + (ch - 'A');
 361     }
 362
 363     return -1;
 364 }
 365
 366 /* Compare the binary fingerprint (hash of host key) with the
 367  * host_key_check parameter.
 368  */
 369 static int compare_fingerprint(const unsigned char *fingerprint, size_t len,
 370                                const char *host_key_check)
 371 {
 372     unsigned c;
 373
 374     while (len > 0) {
 375         while (*host_key_check == ':')
 376             host_key_check++;
 377         if (!qemu_isxdigit(host_key_check[0]) ||
 378             !qemu_isxdigit(host_key_check[1]))
 379             return 1;
 380         c = hex2decimal(host_key_check[0]) * 16 +
 381             hex2decimal(host_key_check[1]);
 382         if (c - *fingerprint != 0)
 383             return c - *fingerprint;
 384         fingerprint++;
 385         len--;
 386         host_key_check += 2;
 387     }
 388     return *host_key_check - '\0';
 389 }
 390
 391 static int
 392 check_host_key_hash(BDRVSSHState *s, const char *hash,
 393                     int hash_type, size_t fingerprint_len, Error **errp)
 394 {
 395     const char *fingerprint;
 396
 397     fingerprint = libssh2_hostkey_hash(s->session, hash_type);
 398     if (!fingerprint) {
 399         session_error_setg(errp, s, "failed to read remote host key");
 400         return -EINVAL;
 401     }
 402
 403     if(compare_fingerprint((unsigned char *) fingerprint, fingerprint_len,
 404                            hash) != 0) {
 405         error_setg(errp, "remote host key does not match host_key_check '%s'",
 406                    hash);
 407         return -EPERM;
 408     }
 409
 410     return 0;
 411 }
 412
 413 static int check_host_key(BDRVSSHState *s, const char *host, int port,
 414                           const char *host_key_check, Error **errp)
 415 {
 416     /* host_key_check=no */
 417     if (strcmp(host_key_check, "no") == 0) {
 418         return 0;
 419     }
 420
 421     /* host_key_check=md5:xx:yy:zz:... */
 422     if (strncmp(host_key_check, "md5:", 4) == 0) {
 423         return check_host_key_hash(s, &host_key_check[4],
 424                                    LIBSSH2_HOSTKEY_HASH_MD5, 16, errp);
 425     }
 426
 427     /* host_key_check=sha1:xx:yy:zz:... */
 428     if (strncmp(host_key_check, "sha1:", 5) == 0) {
 429         return check_host_key_hash(s, &host_key_check[5],
 430                                    LIBSSH2_HOSTKEY_HASH_SHA1, 20, errp);
 431     }
 432
 433     /* host_key_check=yes */
 434     if (strcmp(host_key_check, "yes") == 0) {
 435         return check_host_key_knownhosts(s, host, port, errp);
 436     }
 437
 438     error_setg(errp, "unknown host_key_check setting (%s)", host_key_check);
 439     return -EINVAL;
 440 }
 441
 442 static int authenticate(BDRVSSHState *s, const char *user, Error **errp)
 443 {
 444     int r, ret;
 445     const char *userauthlist;
 446     LIBSSH2_AGENT *agent = NULL;
 447     struct libssh2_agent_publickey *identity;
 448     struct libssh2_agent_publickey *prev_identity = NULL;
 449
 450     userauthlist = libssh2_userauth_list(s->session, user, strlen(user));
 451     if (strstr(userauthlist, "publickey") == NULL) {
 452         ret = -EPERM;
 453         error_setg(errp,
 454                 "remote server does not support \"publickey\" authentication");
 455         goto out;
 456     }
 457
 458     /* Connect to ssh-agent and try each identity in turn. */
 459     agent = libssh2_agent_init(s->session);
 460     if (!agent) {
 461         ret = -EINVAL;
 462         session_error_setg(errp, s, "failed to initialize ssh-agent support");
 463         goto out;
 464     }
 465     if (libssh2_agent_connect(agent)) {
 466         ret = -ECONNREFUSED;
 467         session_error_setg(errp, s, "failed to connect to ssh-agent");
 468         goto out;
 469     }
 470     if (libssh2_agent_list_identities(agent)) {
 471         ret = -EINVAL;
 472         session_error_setg(errp, s,
 473                            "failed requesting identities from ssh-agent");
 474         goto out;
 475     }
 476
 477     for(;;) {
 478         r = libssh2_agent_get_identity(agent, &identity, prev_identity);
 479         if (r == 1) {           /* end of list */
 480             break;
 481         }
 482         if (r < 0) {
 483             ret = -EINVAL;
 484             session_error_setg(errp, s,
 485                                "failed to obtain identity from ssh-agent");
 486             goto out;
 487         }
 488         r = libssh2_agent_userauth(agent, user, identity);
 489         if (r == 0) {
 490             /* Authenticated! */
 491             ret = 0;
 492             goto out;
 493         }
 494         /* Failed to authenticate with this identity, try the next one. */
 495         prev_identity = identity;
 496     }
 497
 498     ret = -EPERM;
 499     error_setg(errp, "failed to authenticate using publickey authentication "
 500                "and the identities held by your ssh-agent");
 501
 502  out:
 503     if (agent != NULL) {
 504         /* Note: libssh2 implementation implicitly calls
 505          * libssh2_agent_disconnect if necessary.
 506          */
 507         libssh2_agent_free(agent);
 508     }
 509
 510     return ret;
 511 }
 512
 513 static int connect_to_ssh(BDRVSSHState *s, QDict *options,
 514                           int ssh_flags, int creat_mode, Error **errp)
 515 {
 516     int r, ret;
 517     const char *host, *user, *path, *host_key_check;
 518     int port;
 519
 520     if (!qdict_haskey(options, "host")) {
 521         ret = -EINVAL;
 522         error_setg(errp, "No hostname was specified");
 523         goto err;
 524     }
 525     host = qdict_get_str(options, "host");
 526
 527     if (qdict_haskey(options, "port")) {
 528         port = qdict_get_int(options, "port");
 529     } else {
 530         port = 22;
 531     }
 532
 533     if (!qdict_haskey(options, "path")) {
 534         ret = -EINVAL;
 535         error_setg(errp, "No path was specified");
 536         goto err;
 537     }
 538     path = qdict_get_str(options, "path");
 539
 540     if (qdict_haskey(options, "user")) {
 541         user = qdict_get_str(options, "user");
 542     } else {
 543         user = g_get_user_name();
 544         if (!user) {
 545             error_setg_errno(errp, errno, "Can't get user name");
 546             ret = -errno;
 547             goto err;
 548         }
 549     }
 550
 551     if (qdict_haskey(options, "host_key_check")) {
 552         host_key_check = qdict_get_str(options, "host_key_check");
 553     } else {
 554         host_key_check = "yes";
 555     }
 556
 557     /* Construct the host:port name for inet_connect. */
 558     g_free(s->hostport);
 559     s->hostport = g_strdup_printf("%s:%d", host, port);
 560
 561     /* Open the socket and connect. */
 562     s->sock = inet_connect(s->hostport, errp);
 563     if (s->sock < 0) {
 564         ret = -errno;
 565         goto err;
 566     }
 567
 568     /* Create SSH session. */
 569     s->session = libssh2_session_init();
 570     if (!s->session) {
 571         ret = -EINVAL;
 572         session_error_setg(errp, s, "failed to initialize libssh2 session");
 573         goto err;
 574     }
 575
 576 #if TRACE_LIBSSH2 != 0
 577     libssh2_trace(s->session, TRACE_LIBSSH2);
 578 #endif
 579
 580     r = libssh2_session_handshake(s->session, s->sock);
 581     if (r != 0) {
 582         ret = -EINVAL;
 583         session_error_setg(errp, s, "failed to establish SSH session");
 584         goto err;
 585     }
 586
 587     /* Check the remote host's key against known_hosts. */
 588     ret = check_host_key(s, host, port, host_key_check, errp);
 589     if (ret < 0) {
 590         goto err;
 591     }
 592
 593     /* Authenticate. */
 594     ret = authenticate(s, user, errp);
 595     if (ret < 0) {
 596         goto err;
 597     }
 598
 599     /* Start SFTP. */
 600     s->sftp = libssh2_sftp_init(s->session);
 601     if (!s->sftp) {
 602         session_error_setg(errp, s, "failed to initialize sftp handle");
 603         ret = -EINVAL;
 604         goto err;
 605     }
 606
 607     /* Open the remote file. */
 608     DPRINTF("opening file %s flags=0x%x creat_mode=0%o",
 609             path, ssh_flags, creat_mode);
 610     s->sftp_handle = libssh2_sftp_open(s->sftp, path, ssh_flags, creat_mode);
 611     if (!s->sftp_handle) {
 612         session_error_setg(errp, s, "failed to open remote file '%s'", path);
 613         ret = -EINVAL;
 614         goto err;
 615     }
 616
 617     r = libssh2_sftp_fstat(s->sftp_handle, &s->attrs);
 618     if (r < 0) {
 619         sftp_error_setg(errp, s, "failed to read file attributes");
 620         return -EINVAL;
 621     }
 622
 623     /* Delete the options we've used; any not deleted will cause the
 624      * block layer to give an error about unused options.
 625      */
 626     qdict_del(options, "host");
 627     qdict_del(options, "port");
 628     qdict_del(options, "user");
 629     qdict_del(options, "path");
 630     qdict_del(options, "host_key_check");
 631
 632     return 0;
 633
 634  err:
 635     if (s->sftp_handle) {
 636         libssh2_sftp_close(s->sftp_handle);
 637     }
 638     s->sftp_handle = NULL;
 639     if (s->sftp) {
 640         libssh2_sftp_shutdown(s->sftp);
 641     }
 642     s->sftp = NULL;
 643     if (s->session) {
 644         libssh2_session_disconnect(s->session,
 645                                    "from qemu ssh client: "
 646                                    "error opening connection");
 647         libssh2_session_free(s->session);
 648     }
 649     s->session = NULL;
 650
 651     return ret;
 652 }
 653
 654 static int ssh_file_open(BlockDriverState *bs, QDict *options, int bdrv_flags,
 655                          Error **errp)
 656 {
 657     BDRVSSHState *s = bs->opaque;
 658     int ret;
 659     int ssh_flags;
 660
 661     ssh_state_init(s);
 662
 663     ssh_flags = LIBSSH2_FXF_READ;
 664     if (bdrv_flags & BDRV_O_RDWR) {
 665         ssh_flags |= LIBSSH2_FXF_WRITE;
 666     }
 667
 668     /* Start up SSH. */
 669     ret = connect_to_ssh(s, options, ssh_flags, 0, errp);
 670     if (ret < 0) {
 671         goto err;
 672     }
 673
 674     /* Go non-blocking. */
 675     libssh2_session_set_blocking(s->session, 0);
 676
 677     return 0;
 678
 679  err:
 680     if (s->sock >= 0) {
 681         close(s->sock);
 682     }
 683     s->sock = -1;
 684
 685     return ret;
 686 }
 687
 688 static QemuOptsList ssh_create_opts = {
 689     .name = "ssh-create-opts",
 690     .head = QTAILQ_HEAD_INITIALIZER(ssh_create_opts.head),
 691     .desc = {
 692         {
 693             .name = BLOCK_OPT_SIZE,
 694             .type = QEMU_OPT_SIZE,
 695             .help = "Virtual disk size"
 696         },
 697         { /* end of list */ }
 698     }
 699 };
 700
 701 static int ssh_create(const char *filename, QemuOpts *opts, Error **errp)
 702 {
 703     int r, ret;
 704     int64_t total_size = 0;
 705     QDict *uri_options = NULL;
 706     BDRVSSHState s;
 707     ssize_t r2;
 708     char c[1] = { '\0' };
 709
 710     ssh_state_init(&s);
 711
 712     /* Get desired file size. */
 713     total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
 714                           BDRV_SECTOR_SIZE);
 715     DPRINTF("total_size=%" PRIi64, total_size);
 716
 717     uri_options = qdict_new();
 718     r = parse_uri(filename, uri_options, errp);
 719     if (r < 0) {
 720         ret = r;
 721         goto out;
 722     }
 723
 724     r = connect_to_ssh(&s, uri_options,
 725                        LIBSSH2_FXF_READ|LIBSSH2_FXF_WRITE|
 726                        LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC,
 727                        0644, errp);
 728     if (r < 0) {
 729         ret = r;
 730         goto out;
 731     }
 732
 733     if (total_size > 0) {
 734         libssh2_sftp_seek64(s.sftp_handle, total_size-1);
 735         r2 = libssh2_sftp_write(s.sftp_handle, c, 1);
 736         if (r2 < 0) {
 737             sftp_error_setg(errp, &s, "truncate failed");
 738             ret = -EINVAL;
 739             goto out;
 740         }
 741         s.attrs.filesize = total_size;
 742     }
 743
 744     ret = 0;
 745
 746  out:
 747     ssh_state_free(&s);
 748     if (uri_options != NULL) {
 749         QDECREF(uri_options);
 750     }
 751     return ret;
 752 }
 753
 754 static void ssh_close(BlockDriverState *bs)
 755 {
 756     BDRVSSHState *s = bs->opaque;
 757
 758     ssh_state_free(s);
 759 }
 760
 761 static int ssh_has_zero_init(BlockDriverState *bs)
 762 {
 763     BDRVSSHState *s = bs->opaque;
 764     /* Assume false, unless we can positively prove it's true. */
 765     int has_zero_init = 0;
 766
 767     if (s->attrs.flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
 768         if (s->attrs.permissions & LIBSSH2_SFTP_S_IFREG) {
 769             has_zero_init = 1;
 770         }
 771     }
 772
 773     return has_zero_init;
 774 }
 775
 776 static void restart_coroutine(void *opaque)
 777 {
 778     Coroutine *co = opaque;
 779
 780     DPRINTF("co=%p", co);
 781
 782     qemu_coroutine_enter(co, NULL);
 783 }
 784
 785 static coroutine_fn void set_fd_handler(BDRVSSHState *s, BlockDriverState *bs)
 786 {
 787     int r;
 788     IOHandler *rd_handler = NULL, *wr_handler = NULL;
 789     Coroutine *co = qemu_coroutine_self();
 790
 791     r = libssh2_session_block_directions(s->session);
 792
 793     if (r & LIBSSH2_SESSION_BLOCK_INBOUND) {
 794         rd_handler = restart_coroutine;
 795     }
 796     if (r & LIBSSH2_SESSION_BLOCK_OUTBOUND) {
 797         wr_handler = restart_coroutine;
 798     }
 799
 800     DPRINTF("s->sock=%d rd_handler=%p wr_handler=%p", s->sock,
 801             rd_handler, wr_handler);
 802
 803     aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock,
 804                        rd_handler, wr_handler, co);
 805 }
 806
 807 static coroutine_fn void clear_fd_handler(BDRVSSHState *s,
 808                                           BlockDriverState *bs)
 809 {
 810     DPRINTF("s->sock=%d", s->sock);
 811     aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock, NULL, NULL, NULL);
 812 }
 813
 814 /* A non-blocking call returned EAGAIN, so yield, ensuring the
 815  * handlers are set up so that we'll be rescheduled when there is an
 816  * interesting event on the socket.
 817  */
 818 static coroutine_fn void co_yield(BDRVSSHState *s, BlockDriverState *bs)
 819 {
 820     set_fd_handler(s, bs);
 821     qemu_coroutine_yield();
 822     clear_fd_handler(s, bs);
 823 }
 824
 825 /* SFTP has a function `libssh2_sftp_seek64' which seeks to a position
 826  * in the remote file.  Notice that it just updates a field in the
 827  * sftp_handle structure, so there is no network traffic and it cannot
 828  * fail.
 829  *
 830  * However, `libssh2_sftp_seek64' does have a catastrophic effect on
 831  * performance since it causes the handle to throw away all in-flight
 832  * reads and buffered readahead data.  Therefore this function tries
 833  * to be intelligent about when to call the underlying libssh2 function.
 834  */
 835 #define SSH_SEEK_WRITE 0
 836 #define SSH_SEEK_READ  1
 837 #define SSH_SEEK_FORCE 2
 838
 839 static void ssh_seek(BDRVSSHState *s, int64_t offset, int flags)
 840 {
 841     bool op_read = (flags & SSH_SEEK_READ) != 0;
 842     bool force = (flags & SSH_SEEK_FORCE) != 0;
 843
 844     if (force || op_read != s->offset_op_read || offset != s->offset) {
 845         DPRINTF("seeking to offset=%" PRIi64, offset);
 846         libssh2_sftp_seek64(s->sftp_handle, offset);
 847         s->offset = offset;
 848         s->offset_op_read = op_read;
 849     }
 850 }
 851
 852 static coroutine_fn int ssh_read(BDRVSSHState *s, BlockDriverState *bs,
 853                                  int64_t offset, size_t size,
 854                                  QEMUIOVector *qiov)
 855 {
 856     ssize_t r;
 857     size_t got;
 858     char *buf, *end_of_vec;
 859     struct iovec *i;
 860
 861     DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
 862
 863     ssh_seek(s, offset, SSH_SEEK_READ);
 864
 865     /* This keeps track of the current iovec element ('i'), where we
 866      * will write to next ('buf'), and the end of the current iovec
 867      * ('end_of_vec').
 868      */
 869     i = &qiov->iov[0];
 870     buf = i->iov_base;
 871     end_of_vec = i->iov_base + i->iov_len;
 872
 873     /* libssh2 has a hard-coded limit of 2000 bytes per request,
 874      * although it will also do readahead behind our backs.  Therefore
 875      * we may have to do repeated reads here until we have read 'size'
 876      * bytes.
 877      */
 878     for (got = 0; got < size; ) {
 879     again:
 880         DPRINTF("sftp_read buf=%p size=%zu", buf, end_of_vec - buf);
 881         r = libssh2_sftp_read(s->sftp_handle, buf, end_of_vec - buf);
 882         DPRINTF("sftp_read returned %zd", r);
 883
 884         if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
 885             co_yield(s, bs);
 886             goto again;
 887         }
 888         if (r < 0) {
 889             sftp_error_report(s, "read failed");
 890             s->offset = -1;
 891             return -EIO;
 892         }
 893         if (r == 0) {
 894             /* EOF: Short read so pad the buffer with zeroes and return it. */
 895             qemu_iovec_memset(qiov, got, 0, size - got);
 896             return 0;
 897         }
 898
 899         got += r;
 900         buf += r;
 901         s->offset += r;
 902         if (buf >= end_of_vec && got < size) {
 903             i++;
 904             buf = i->iov_base;
 905             end_of_vec = i->iov_base + i->iov_len;
 906         }
 907     }
 908
 909     return 0;
 910 }
 911
 912 static coroutine_fn int ssh_co_readv(BlockDriverState *bs,
 913                                      int64_t sector_num,
 914                                      int nb_sectors, QEMUIOVector *qiov)
 915 {
 916     BDRVSSHState *s = bs->opaque;
 917     int ret;
 918
 919     qemu_co_mutex_lock(&s->lock);
 920     ret = ssh_read(s, bs, sector_num * BDRV_SECTOR_SIZE,
 921                    nb_sectors * BDRV_SECTOR_SIZE, qiov);
 922     qemu_co_mutex_unlock(&s->lock);
 923
 924     return ret;
 925 }
 926
 927 static int ssh_write(BDRVSSHState *s, BlockDriverState *bs,
 928                      int64_t offset, size_t size,
 929                      QEMUIOVector *qiov)
 930 {
 931     ssize_t r;
 932     size_t written;
 933     char *buf, *end_of_vec;
 934     struct iovec *i;
 935
 936     DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
 937
 938     ssh_seek(s, offset, SSH_SEEK_WRITE);
 939
 940     /* This keeps track of the current iovec element ('i'), where we
 941      * will read from next ('buf'), and the end of the current iovec
 942      * ('end_of_vec').
 943      */
 944     i = &qiov->iov[0];
 945     buf = i->iov_base;
 946     end_of_vec = i->iov_base + i->iov_len;
 947
 948     for (written = 0; written < size; ) {
 949     again:
 950         DPRINTF("sftp_write buf=%p size=%zu", buf, end_of_vec - buf);
 951         r = libssh2_sftp_write(s->sftp_handle, buf, end_of_vec - buf);
 952         DPRINTF("sftp_write returned %zd", r);
 953
 954         if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
 955             co_yield(s, bs);
 956             goto again;
 957         }
 958         if (r < 0) {
 959             sftp_error_report(s, "write failed");
 960             s->offset = -1;
 961             return -EIO;
 962         }
 963         /* The libssh2 API is very unclear about this.  A comment in
 964          * the code says "nothing was acked, and no EAGAIN was
 965          * received!" which apparently means that no data got sent
 966          * out, and the underlying channel didn't return any EAGAIN
 967          * indication.  I think this is a bug in either libssh2 or
 968          * OpenSSH (server-side).  In any case, forcing a seek (to
 969          * discard libssh2 internal buffers), and then trying again
 970          * works for me.
 971          */
 972         if (r == 0) {
 973             ssh_seek(s, offset + written, SSH_SEEK_WRITE|SSH_SEEK_FORCE);
 974             co_yield(s, bs);
 975             goto again;
 976         }
 977
 978         written += r;
 979         buf += r;
 980         s->offset += r;
 981         if (buf >= end_of_vec && written < size) {
 982             i++;
 983             buf = i->iov_base;
 984             end_of_vec = i->iov_base + i->iov_len;
 985         }
 986
 987         if (offset + written > s->attrs.filesize)
 988             s->attrs.filesize = offset + written;
 989     }
 990
 991     return 0;
 992 }
 993
 994 static coroutine_fn int ssh_co_writev(BlockDriverState *bs,
 995                                       int64_t sector_num,
 996                                       int nb_sectors, QEMUIOVector *qiov)
 997 {
 998     BDRVSSHState *s = bs->opaque;
 999     int ret;
1000
1001     qemu_co_mutex_lock(&s->lock);
1002     ret = ssh_write(s, bs, sector_num * BDRV_SECTOR_SIZE,
1003                     nb_sectors * BDRV_SECTOR_SIZE, qiov);
1004     qemu_co_mutex_unlock(&s->lock);
1005
1006     return ret;
1007 }
1008
1009 static void unsafe_flush_warning(BDRVSSHState *s, const char *what)
1010 {
1011     if (!s->unsafe_flush_warning) {
1012         error_report("warning: ssh server %s does not support fsync",
1013                      s->hostport);
1014         if (what) {
1015             error_report("to support fsync, you need %s", what);
1016         }
1017         s->unsafe_flush_warning = true;
1018     }
1019 }
1020
1021 #ifdef HAS_LIBSSH2_SFTP_FSYNC
1022
1023 static coroutine_fn int ssh_flush(BDRVSSHState *s, BlockDriverState *bs)
1024 {
1025     int r;
1026
1027     DPRINTF("fsync");
1028  again:
1029     r = libssh2_sftp_fsync(s->sftp_handle);
1030     if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
1031         co_yield(s, bs);
1032         goto again;
1033     }
1034     if (r == LIBSSH2_ERROR_SFTP_PROTOCOL &&
1035         libssh2_sftp_last_error(s->sftp) == LIBSSH2_FX_OP_UNSUPPORTED) {
1036         unsafe_flush_warning(s, "OpenSSH >= 6.3");
1037         return 0;
1038     }
1039     if (r < 0) {
1040         sftp_error_report(s, "fsync failed");
1041         return -EIO;
1042     }
1043
1044     return 0;
1045 }
1046
1047 static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
1048 {
1049     BDRVSSHState *s = bs->opaque;
1050     int ret;
1051
1052     qemu_co_mutex_lock(&s->lock);
1053     ret = ssh_flush(s, bs);
1054     qemu_co_mutex_unlock(&s->lock);
1055
1056     return ret;
1057 }
1058
1059 #else /* !HAS_LIBSSH2_SFTP_FSYNC */
1060
1061 static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
1062 {
1063     BDRVSSHState *s = bs->opaque;
1064
1065     unsafe_flush_warning(s, "libssh2 >= 1.4.4");
1066     return 0;
1067 }
1068
1069 #endif /* !HAS_LIBSSH2_SFTP_FSYNC */
1070
1071 static int64_t ssh_getlength(BlockDriverState *bs)
1072 {
1073     BDRVSSHState *s = bs->opaque;
1074     int64_t length;
1075
1076     /* Note we cannot make a libssh2 call here. */
1077     length = (int64_t) s->attrs.filesize;
1078     DPRINTF("length=%" PRIi64, length);
1079
1080     return length;
1081 }
1082
1083 static BlockDriver bdrv_ssh = {
1084     .format_name                  = "ssh",
1085     .protocol_name                = "ssh",
1086     .instance_size                = sizeof(BDRVSSHState),
1087     .bdrv_parse_filename          = ssh_parse_filename,
1088     .bdrv_file_open               = ssh_file_open,
1089     .bdrv_create                  = ssh_create,
1090     .bdrv_close                   = ssh_close,
1091     .bdrv_has_zero_init           = ssh_has_zero_init,
1092     .bdrv_co_readv                = ssh_co_readv,
1093     .bdrv_co_writev               = ssh_co_writev,
1094     .bdrv_getlength               = ssh_getlength,
1095     .bdrv_co_flush_to_disk        = ssh_co_flush,
1096     .create_opts                  = &ssh_create_opts,
1097 };
1098
1099 static void bdrv_ssh_init(void)
1100 {
1101     int r;
1102
1103     r = libssh2_init(0);
1104     if (r != 0) {
1105         fprintf(stderr, "libssh2 initialization failed, %d\n", r);
1106         exit(EXIT_FAILURE);
1107     }
1108
1109     bdrv_register(&bdrv_ssh);
1110 }
1111
1112 block_init(bdrv_ssh_init);