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