Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging
[qemu.git] / block / ssh.c
blobf466cbf396625e72ec33440ff92280d30145424a
1 /*
2 * Secure Shell (ssh) backend for QEMU.
4 * Copyright (C) 2013 Red Hat Inc., Richard W.M. Jones <rjones@redhat.com>
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:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
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.
25 #include <stdio.h>
26 #include <stdlib.h>
27 #include <stdarg.h>
29 #include <libssh2.h>
30 #include <libssh2_sftp.h>
32 #include "block/block_int.h"
33 #include "qemu/sockets.h"
34 #include "qemu/uri.h"
35 #include "qapi/qmp/qint.h"
37 /* DEBUG_SSH=1 enables the DPRINTF (debugging printf) statements in
38 * this block driver code.
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
46 #define DEBUG_SSH 0
47 #define TRACE_LIBSSH2 0 /* or try: LIBSSH2_TRACE_SFTP */
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)
57 typedef struct BDRVSSHState {
58 /* Coroutine. */
59 CoMutex lock;
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 */
67 /* See ssh_seek() function below. */
68 int64_t offset;
69 bool offset_op_read;
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).
74 LIBSSH2_SFTP_ATTRIBUTES attrs;
76 /* Used to warn if 'flush' is not supported. */
77 char *hostport;
78 bool unsafe_flush_warning;
79 } BDRVSSHState;
81 static void ssh_state_init(BDRVSSHState *s)
83 memset(s, 0, sizeof *s);
84 s->sock = -1;
85 s->offset = -1;
86 qemu_co_mutex_init(&s->lock);
89 static void ssh_state_free(BDRVSSHState *s)
91 g_free(s->hostport);
92 if (s->sftp_handle) {
93 libssh2_sftp_close(s->sftp_handle);
95 if (s->sftp) {
96 libssh2_sftp_shutdown(s->sftp);
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);
104 if (s->sock >= 0) {
105 close(s->sock);
109 static void GCC_FMT_ATTR(3, 4)
110 session_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
112 va_list args;
113 char *msg;
115 va_start(args, fs);
116 msg = g_strdup_vprintf(fs, args);
117 va_end(args);
119 if (s->session) {
120 char *ssh_err;
121 int ssh_err_code;
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);
131 g_free(msg);
134 static void GCC_FMT_ATTR(3, 4)
135 sftp_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
137 va_list args;
138 char *msg;
140 va_start(args, fs);
141 msg = g_strdup_vprintf(fs, args);
142 va_end(args);
144 if (s->sftp) {
145 char *ssh_err;
146 int ssh_err_code;
147 unsigned long sftp_err_code;
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);
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);
161 g_free(msg);
164 static void GCC_FMT_ATTR(2, 3)
165 sftp_error_report(BDRVSSHState *s, const char *fs, ...)
167 va_list args;
169 va_start(args, fs);
170 error_vprintf(fs, args);
172 if ((s)->sftp) {
173 char *ssh_err;
174 int ssh_err_code;
175 unsigned long sftp_err_code;
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);
183 error_printf(": %s (libssh2 error code: %d, sftp error code: %lu)",
184 ssh_err, ssh_err_code, sftp_err_code);
187 va_end(args);
188 error_printf("\n");
191 static int parse_uri(const char *filename, QDict *options, Error **errp)
193 URI *uri = NULL;
194 QueryParams *qp = NULL;
195 int i;
197 uri = uri_parse(filename);
198 if (!uri) {
199 return -EINVAL;
202 if (strcmp(uri->scheme, "ssh") != 0) {
203 error_setg(errp, "URI scheme must be 'ssh'");
204 goto err;
207 if (!uri->server || strcmp(uri->server, "") == 0) {
208 error_setg(errp, "missing hostname in URI");
209 goto err;
212 if (!uri->path || strcmp(uri->path, "") == 0) {
213 error_setg(errp, "missing remote path in URI");
214 goto err;
217 qp = query_params_parse(uri->query);
218 if (!qp) {
219 error_setg(errp, "could not parse query parameters");
220 goto err;
223 if(uri->user && strcmp(uri->user, "") != 0) {
224 qdict_put(options, "user", qstring_from_str(uri->user));
227 qdict_put(options, "host", qstring_from_str(uri->server));
229 if (uri->port) {
230 qdict_put(options, "port", qint_from_int(uri->port));
233 qdict_put(options, "path", qstring_from_str(uri->path));
235 /* Pick out any query parameters that we understand, and ignore
236 * the rest.
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));
245 query_params_free(qp);
246 uri_free(uri);
247 return 0;
249 err:
250 if (qp) {
251 query_params_free(qp);
253 if (uri) {
254 uri_free(uri);
256 return -EINVAL;
259 static void ssh_parse_filename(const char *filename, QDict *options,
260 Error **errp)
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;
271 parse_uri(filename, options, errp);
274 static int check_host_key_knownhosts(BDRVSSHState *s,
275 const char *host, int port, Error **errp)
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;
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;
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;
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");
308 /* Read all known hosts from OpenSSH-style known_hosts file. */
309 libssh2_knownhost_readfile(knh, knh_file, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
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;
342 /* known_hosts checking successful. */
343 ret = 0;
345 out:
346 if (knh != NULL) {
347 libssh2_knownhost_free(knh);
349 g_free(knh_file);
350 return ret;
353 static unsigned hex2decimal(char ch)
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');
363 return -1;
366 /* Compare the binary fingerprint (hash of host key) with the
367 * host_key_check parameter.
369 static int compare_fingerprint(const unsigned char *fingerprint, size_t len,
370 const char *host_key_check)
372 unsigned c;
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;
388 return *host_key_check - '\0';
391 static int
392 check_host_key_hash(BDRVSSHState *s, const char *hash,
393 int hash_type, size_t fingerprint_len, Error **errp)
395 const char *fingerprint;
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;
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;
410 return 0;
413 static int check_host_key(BDRVSSHState *s, const char *host, int port,
414 const char *host_key_check, Error **errp)
416 /* host_key_check=no */
417 if (strcmp(host_key_check, "no") == 0) {
418 return 0;
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);
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);
433 /* host_key_check=yes */
434 if (strcmp(host_key_check, "yes") == 0) {
435 return check_host_key_knownhosts(s, host, port, errp);
438 error_setg(errp, "unknown host_key_check setting (%s)", host_key_check);
439 return -EINVAL;
442 static int authenticate(BDRVSSHState *s, const char *user, Error **errp)
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;
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;
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;
465 if (libssh2_agent_connect(agent)) {
466 ret = -ECONNREFUSED;
467 session_error_setg(errp, s, "failed to connect to ssh-agent");
468 goto out;
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;
477 for(;;) {
478 r = libssh2_agent_get_identity(agent, &identity, prev_identity);
479 if (r == 1) { /* end of list */
480 break;
482 if (r < 0) {
483 ret = -EINVAL;
484 session_error_setg(errp, s,
485 "failed to obtain identity from ssh-agent");
486 goto out;
488 r = libssh2_agent_userauth(agent, user, identity);
489 if (r == 0) {
490 /* Authenticated! */
491 ret = 0;
492 goto out;
494 /* Failed to authenticate with this identity, try the next one. */
495 prev_identity = identity;
498 ret = -EPERM;
499 error_setg(errp, "failed to authenticate using publickey authentication "
500 "and the identities held by your ssh-agent");
502 out:
503 if (agent != NULL) {
504 /* Note: libssh2 implementation implicitly calls
505 * libssh2_agent_disconnect if necessary.
507 libssh2_agent_free(agent);
510 return ret;
513 static int connect_to_ssh(BDRVSSHState *s, QDict *options,
514 int ssh_flags, int creat_mode, Error **errp)
516 int r, ret;
517 const char *host, *user, *path, *host_key_check;
518 int port;
520 if (!qdict_haskey(options, "host")) {
521 ret = -EINVAL;
522 error_setg(errp, "No hostname was specified");
523 goto err;
525 host = qdict_get_str(options, "host");
527 if (qdict_haskey(options, "port")) {
528 port = qdict_get_int(options, "port");
529 } else {
530 port = 22;
533 if (!qdict_haskey(options, "path")) {
534 ret = -EINVAL;
535 error_setg(errp, "No path was specified");
536 goto err;
538 path = qdict_get_str(options, "path");
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;
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";
557 /* Construct the host:port name for inet_connect. */
558 g_free(s->hostport);
559 s->hostport = g_strdup_printf("%s:%d", host, port);
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;
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;
576 #if TRACE_LIBSSH2 != 0
577 libssh2_trace(s->session, TRACE_LIBSSH2);
578 #endif
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;
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;
593 /* Authenticate. */
594 ret = authenticate(s, user, errp);
595 if (ret < 0) {
596 goto err;
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;
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;
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;
623 /* Delete the options we've used; any not deleted will cause the
624 * block layer to give an error about unused options.
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");
632 return 0;
634 err:
635 if (s->sftp_handle) {
636 libssh2_sftp_close(s->sftp_handle);
638 s->sftp_handle = NULL;
639 if (s->sftp) {
640 libssh2_sftp_shutdown(s->sftp);
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);
649 s->session = NULL;
651 return ret;
654 static int ssh_file_open(BlockDriverState *bs, QDict *options, int bdrv_flags,
655 Error **errp)
657 BDRVSSHState *s = bs->opaque;
658 int ret;
659 int ssh_flags;
661 ssh_state_init(s);
663 ssh_flags = LIBSSH2_FXF_READ;
664 if (bdrv_flags & BDRV_O_RDWR) {
665 ssh_flags |= LIBSSH2_FXF_WRITE;
668 /* Start up SSH. */
669 ret = connect_to_ssh(s, options, ssh_flags, 0, errp);
670 if (ret < 0) {
671 goto err;
674 /* Go non-blocking. */
675 libssh2_session_set_blocking(s->session, 0);
677 return 0;
679 err:
680 if (s->sock >= 0) {
681 close(s->sock);
683 s->sock = -1;
685 return ret;
688 static QemuOptsList ssh_create_opts = {
689 .name = "ssh-create-opts",
690 .head = QTAILQ_HEAD_INITIALIZER(ssh_create_opts.head),
691 .desc = {
693 .name = BLOCK_OPT_SIZE,
694 .type = QEMU_OPT_SIZE,
695 .help = "Virtual disk size"
697 { /* end of list */ }
701 static int ssh_create(const char *filename, QemuOpts *opts, Error **errp)
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' };
710 ssh_state_init(&s);
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);
717 uri_options = qdict_new();
718 r = parse_uri(filename, uri_options, errp);
719 if (r < 0) {
720 ret = r;
721 goto out;
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;
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;
741 s.attrs.filesize = total_size;
744 ret = 0;
746 out:
747 ssh_state_free(&s);
748 if (uri_options != NULL) {
749 QDECREF(uri_options);
751 return ret;
754 static void ssh_close(BlockDriverState *bs)
756 BDRVSSHState *s = bs->opaque;
758 ssh_state_free(s);
761 static int ssh_has_zero_init(BlockDriverState *bs)
763 BDRVSSHState *s = bs->opaque;
764 /* Assume false, unless we can positively prove it's true. */
765 int has_zero_init = 0;
767 if (s->attrs.flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
768 if (s->attrs.permissions & LIBSSH2_SFTP_S_IFREG) {
769 has_zero_init = 1;
773 return has_zero_init;
776 static void restart_coroutine(void *opaque)
778 Coroutine *co = opaque;
780 DPRINTF("co=%p", co);
782 qemu_coroutine_enter(co, NULL);
785 static coroutine_fn void set_fd_handler(BDRVSSHState *s, BlockDriverState *bs)
787 int r;
788 IOHandler *rd_handler = NULL, *wr_handler = NULL;
789 Coroutine *co = qemu_coroutine_self();
791 r = libssh2_session_block_directions(s->session);
793 if (r & LIBSSH2_SESSION_BLOCK_INBOUND) {
794 rd_handler = restart_coroutine;
796 if (r & LIBSSH2_SESSION_BLOCK_OUTBOUND) {
797 wr_handler = restart_coroutine;
800 DPRINTF("s->sock=%d rd_handler=%p wr_handler=%p", s->sock,
801 rd_handler, wr_handler);
803 aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock,
804 rd_handler, wr_handler, co);
807 static coroutine_fn void clear_fd_handler(BDRVSSHState *s,
808 BlockDriverState *bs)
810 DPRINTF("s->sock=%d", s->sock);
811 aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock, NULL, NULL, NULL);
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.
818 static coroutine_fn void co_yield(BDRVSSHState *s, BlockDriverState *bs)
820 set_fd_handler(s, bs);
821 qemu_coroutine_yield();
822 clear_fd_handler(s, bs);
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.
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.
835 #define SSH_SEEK_WRITE 0
836 #define SSH_SEEK_READ 1
837 #define SSH_SEEK_FORCE 2
839 static void ssh_seek(BDRVSSHState *s, int64_t offset, int flags)
841 bool op_read = (flags & SSH_SEEK_READ) != 0;
842 bool force = (flags & SSH_SEEK_FORCE) != 0;
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;
852 static coroutine_fn int ssh_read(BDRVSSHState *s, BlockDriverState *bs,
853 int64_t offset, size_t size,
854 QEMUIOVector *qiov)
856 ssize_t r;
857 size_t got;
858 char *buf, *end_of_vec;
859 struct iovec *i;
861 DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
863 ssh_seek(s, offset, SSH_SEEK_READ);
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').
869 i = &qiov->iov[0];
870 buf = i->iov_base;
871 end_of_vec = i->iov_base + i->iov_len;
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.
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);
884 if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
885 co_yield(s, bs);
886 goto again;
888 if (r < 0) {
889 sftp_error_report(s, "read failed");
890 s->offset = -1;
891 return -EIO;
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;
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;
909 return 0;
912 static coroutine_fn int ssh_co_readv(BlockDriverState *bs,
913 int64_t sector_num,
914 int nb_sectors, QEMUIOVector *qiov)
916 BDRVSSHState *s = bs->opaque;
917 int ret;
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);
924 return ret;
927 static int ssh_write(BDRVSSHState *s, BlockDriverState *bs,
928 int64_t offset, size_t size,
929 QEMUIOVector *qiov)
931 ssize_t r;
932 size_t written;
933 char *buf, *end_of_vec;
934 struct iovec *i;
936 DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
938 ssh_seek(s, offset, SSH_SEEK_WRITE);
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').
944 i = &qiov->iov[0];
945 buf = i->iov_base;
946 end_of_vec = i->iov_base + i->iov_len;
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);
954 if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
955 co_yield(s, bs);
956 goto again;
958 if (r < 0) {
959 sftp_error_report(s, "write failed");
960 s->offset = -1;
961 return -EIO;
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.
972 if (r == 0) {
973 ssh_seek(s, offset + written, SSH_SEEK_WRITE|SSH_SEEK_FORCE);
974 co_yield(s, bs);
975 goto again;
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;
987 if (offset + written > s->attrs.filesize)
988 s->attrs.filesize = offset + written;
991 return 0;
994 static coroutine_fn int ssh_co_writev(BlockDriverState *bs,
995 int64_t sector_num,
996 int nb_sectors, QEMUIOVector *qiov)
998 BDRVSSHState *s = bs->opaque;
999 int ret;
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);
1006 return ret;
1009 static void unsafe_flush_warning(BDRVSSHState *s, const char *what)
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);
1017 s->unsafe_flush_warning = true;
1021 #ifdef HAS_LIBSSH2_SFTP_FSYNC
1023 static coroutine_fn int ssh_flush(BDRVSSHState *s, BlockDriverState *bs)
1025 int r;
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;
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;
1039 if (r < 0) {
1040 sftp_error_report(s, "fsync failed");
1041 return -EIO;
1044 return 0;
1047 static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
1049 BDRVSSHState *s = bs->opaque;
1050 int ret;
1052 qemu_co_mutex_lock(&s->lock);
1053 ret = ssh_flush(s, bs);
1054 qemu_co_mutex_unlock(&s->lock);
1056 return ret;
1059 #else /* !HAS_LIBSSH2_SFTP_FSYNC */
1061 static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
1063 BDRVSSHState *s = bs->opaque;
1065 unsafe_flush_warning(s, "libssh2 >= 1.4.4");
1066 return 0;
1069 #endif /* !HAS_LIBSSH2_SFTP_FSYNC */
1071 static int64_t ssh_getlength(BlockDriverState *bs)
1073 BDRVSSHState *s = bs->opaque;
1074 int64_t length;
1076 /* Note we cannot make a libssh2 call here. */
1077 length = (int64_t) s->attrs.filesize;
1078 DPRINTF("length=%" PRIi64, length);
1080 return length;
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,
1099 static void bdrv_ssh_init(void)
1101 int r;
1103 r = libssh2_init(0);
1104 if (r != 0) {
1105 fprintf(stderr, "libssh2 initialization failed, %d\n", r);
1106 exit(EXIT_FAILURE);
1109 bdrv_register(&bdrv_ssh);
1112 block_init(bdrv_ssh_init);