summaryrefslogtreecommitdiffstats
path: root/block/ssh.c
blob: cf43bc0f8946c0b7f9deb89228e26741e09eb377 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
/*
 * Secure Shell (ssh) backend for QEMU.
 *
 * Copyright (C) 2013 Red Hat Inc., Richard W.M. Jones <rjones@redhat.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

#include <libssh2.h>
#include <libssh2_sftp.h>

#include "block/block_int.h"
#include "qemu/sockets.h"
#include "qemu/uri.h"
#include "qapi/qmp/qint.h"

/* DEBUG_SSH=1 enables the DPRINTF (debugging printf) statements in
 * this block driver code.
 *
 * TRACE_LIBSSH2=<bitmask> enables tracing in libssh2 itself.  Note
 * that this requires that libssh2 was specially compiled with the
 * `./configure --enable-debug' option, so most likely you will have
 * to compile it yourself.  The meaning of <bitmask> is described
 * here: http://www.libssh2.org/libssh2_trace.html
 */
#define DEBUG_SSH     0
#define TRACE_LIBSSH2 0 /* or try: LIBSSH2_TRACE_SFTP */

#define DPRINTF(fmt, ...)                           \
    do {                                            \
        if (DEBUG_SSH) {                            \
            fprintf(stderr, "ssh: %-15s " fmt "\n", \
                    __func__, ##__VA_ARGS__);       \
        }                                           \
    } while (0)

typedef struct BDRVSSHState {
    /* Coroutine. */
    CoMutex lock;

    /* SSH connection. */
    int sock;                         /* socket */
    LIBSSH2_SESSION *session;         /* ssh session */
    LIBSSH2_SFTP *sftp;               /* sftp session */
    LIBSSH2_SFTP_HANDLE *sftp_handle; /* sftp remote file handle */

    /* See ssh_seek() function below. */
    int64_t offset;
    bool offset_op_read;

    /* File attributes at open.  We try to keep the .filesize field
     * updated if it changes (eg by writing at the end of the file).
     */
    LIBSSH2_SFTP_ATTRIBUTES attrs;

    /* Used to warn if 'flush' is not supported. */
    char *hostport;
    bool unsafe_flush_warning;
} BDRVSSHState;

static void ssh_state_init(BDRVSSHState *s)
{
    memset(s, 0, sizeof *s);
    s->sock = -1;
    s->offset = -1;
    qemu_co_mutex_init(&s->lock);
}

static void ssh_state_free(BDRVSSHState *s)
{
    g_free(s->hostport);
    if (s->sftp_handle) {
        libssh2_sftp_close(s->sftp_handle);
    }
    if (s->sftp) {
        libssh2_sftp_shutdown(s->sftp);
    }
    if (s->session) {
        libssh2_session_disconnect(s->session,
                                   "from qemu ssh client: "
                                   "user closed the connection");
        libssh2_session_free(s->session);
    }
    if (s->sock >= 0) {
        close(s->sock);
    }
}

static void GCC_FMT_ATTR(3, 4)
session_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
{
    va_list args;
    char *msg;

    va_start(args, fs);
    msg = g_strdup_vprintf(fs, args);
    va_end(args);

    if (s->session) {
        char *ssh_err;
        int ssh_err_code;

        /* This is not an errno.  See <libssh2.h>. */
        ssh_err_code = libssh2_session_last_error(s->session,
                                                  &ssh_err, NULL, 0);
        error_setg(errp, "%s: %s (libssh2 error code: %d)",
                   msg, ssh_err, ssh_err_code);
    } else {
        error_setg(errp, "%s", msg);
    }
    g_free(msg);
}

static void GCC_FMT_ATTR(3, 4)
sftp_error_setg(Error **errp, BDRVSSHState *s, const char *fs, ...)
{
    va_list args;
    char *msg;

    va_start(args, fs);
    msg = g_strdup_vprintf(fs, args);
    va_end(args);

    if (s->sftp) {
        char *ssh_err;
        int ssh_err_code;
        unsigned long sftp_err_code;

        /* This is not an errno.  See <libssh2.h>. */
        ssh_err_code = libssh2_session_last_error(s->session,
                                                  &ssh_err, NULL, 0);
        /* See <libssh2_sftp.h>. */
        sftp_err_code = libssh2_sftp_last_error((s)->sftp);

        error_setg(errp,
                   "%s: %s (libssh2 error code: %d, sftp error code: %lu)",
                   msg, ssh_err, ssh_err_code, sftp_err_code);
    } else {
        error_setg(errp, "%s", msg);
    }
    g_free(msg);
}

static void GCC_FMT_ATTR(2, 3)
sftp_error_report(BDRVSSHState *s, const char *fs, ...)
{
    va_list args;

    va_start(args, fs);
    error_vprintf(fs, args);

    if ((s)->sftp) {
        char *ssh_err;
        int ssh_err_code;
        unsigned long sftp_err_code;

        /* This is not an errno.  See <libssh2.h>. */
        ssh_err_code = libssh2_session_last_error(s->session,
                                                  &ssh_err, NULL, 0);
        /* See <libssh2_sftp.h>. */
        sftp_err_code = libssh2_sftp_last_error((s)->sftp);

        error_printf(": %s (libssh2 error code: %d, sftp error code: %lu)",
                     ssh_err, ssh_err_code, sftp_err_code);
    }

    va_end(args);
    error_printf("\n");
}

static int parse_uri(const char *filename, QDict *options, Error **errp)
{
    URI *uri = NULL;
    QueryParams *qp = NULL;
    int i;

    uri = uri_parse(filename);
    if (!uri) {
        return -EINVAL;
    }

    if (strcmp(uri->scheme, "ssh") != 0) {
        error_setg(errp, "URI scheme must be 'ssh'");
        goto err;
    }

    if (!uri->server || strcmp(uri->server, "") == 0) {
        error_setg(errp, "missing hostname in URI");
        goto err;
    }

    if (!uri->path || strcmp(uri->path, "") == 0) {
        error_setg(errp, "missing remote path in URI");
        goto err;
    }

    qp = query_params_parse(uri->query);
    if (!qp) {
        error_setg(errp, "could not parse query parameters");
        goto err;
    }

    if(uri->user && strcmp(uri->user, "") != 0) {
        qdict_put(options, "user", qstring_from_str(uri->user));
    }

    qdict_put(options, "host", qstring_from_str(uri->server));

    if (uri->port) {
        qdict_put(options, "port", qint_from_int(uri->port));
    }

    qdict_put(options, "path", qstring_from_str(uri->path));

    /* Pick out any query parameters that we understand, and ignore
     * the rest.
     */
    for (i = 0; i < qp->n; ++i) {
        if (strcmp(qp->p[i].name, "host_key_check") == 0) {
            qdict_put(options, "host_key_check",
                      qstring_from_str(qp->p[i].value));
        }
    }

    query_params_free(qp);
    uri_free(uri);
    return 0;

 err:
    if (qp) {
      query_params_free(qp);
    }
    if (uri) {
      uri_free(uri);
    }
    return -EINVAL;
}

static void ssh_parse_filename(const char *filename, QDict *options,
                               Error **errp)
{
    if (qdict_haskey(options, "user") ||
        qdict_haskey(options, "host") ||
        qdict_haskey(options, "port") ||
        qdict_haskey(options, "path") ||
        qdict_haskey(options, "host_key_check")) {
        error_setg(errp, "user, host, port, path, host_key_check cannot be used at the same time as a file option");
        return;
    }

    parse_uri(filename, options, errp);
}

static int check_host_key_knownhosts(BDRVSSHState *s,
                                     const char *host, int port, Error **errp)
{
    const char *home;
    char *knh_file = NULL;
    LIBSSH2_KNOWNHOSTS *knh = NULL;
    struct libssh2_knownhost *found;
    int ret, r;
    const char *hostkey;
    size_t len;
    int type;

    hostkey = libssh2_session_hostkey(s->session, &len, &type);
    if (!hostkey) {
        ret = -EINVAL;
        session_error_setg(errp, s, "failed to read remote host key");
        goto out;
    }

    knh = libssh2_knownhost_init(s->session);
    if (!knh) {
        ret = -EINVAL;
        session_error_setg(errp, s,
                           "failed to initialize known hosts support");
        goto out;
    }

    home = getenv("HOME");
    if (home) {
        knh_file = g_strdup_printf("%s/.ssh/known_hosts", home);
    } else {
        knh_file = g_strdup_printf("/root/.ssh/known_hosts");
    }

    /* Read all known hosts from OpenSSH-style known_hosts file. */
    libssh2_knownhost_readfile(knh, knh_file, LIBSSH2_KNOWNHOST_FILE_OPENSSH);

    r = libssh2_knownhost_checkp(knh, host, port, hostkey, len,
                                 LIBSSH2_KNOWNHOST_TYPE_PLAIN|
                                 LIBSSH2_KNOWNHOST_KEYENC_RAW,
                                 &found);
    switch (r) {
    case LIBSSH2_KNOWNHOST_CHECK_MATCH:
        /* OK */
        DPRINTF("host key OK: %s", found->key);
        break;
    case LIBSSH2_KNOWNHOST_CHECK_MISMATCH:
        ret = -EINVAL;
        session_error_setg(errp, s,
                      "host key does not match the one in known_hosts"
                      " (found key %s)", found->key);
        goto out;
    case LIBSSH2_KNOWNHOST_CHECK_NOTFOUND:
        ret = -EINVAL;
        session_error_setg(errp, s, "no host key was found in known_hosts");
        goto out;
    case LIBSSH2_KNOWNHOST_CHECK_FAILURE:
        ret = -EINVAL;
        session_error_setg(errp, s,
                      "failure matching the host key with known_hosts");
        goto out;
    default:
        ret = -EINVAL;
        session_error_setg(errp, s, "unknown error matching the host key"
                      " with known_hosts (%d)", r);
        goto out;
    }

    /* known_hosts checking successful. */
    ret = 0;

 out:
    if (knh != NULL) {
        libssh2_knownhost_free(knh);
    }
    g_free(knh_file);
    return ret;
}

static unsigned hex2decimal(char ch)
{
    if (ch >= '0' && ch <= '9') {
        return (ch - '0');
    } else if (ch >= 'a' && ch <= 'f') {
        return 10 + (ch - 'a');
    } else if (ch >= 'A' && ch <= 'F') {
        return 10 + (ch - 'A');
    }

    return -1;
}

/* Compare the binary fingerprint (hash of host key) with the
 * host_key_check parameter.
 */
static int compare_fingerprint(const unsigned char *fingerprint, size_t len,
                               const char *host_key_check)
{
    unsigned c;

    while (len > 0) {
        while (*host_key_check == ':')
            host_key_check++;
        if (!qemu_isxdigit(host_key_check[0]) ||
            !qemu_isxdigit(host_key_check[1]))
            return 1;
        c = hex2decimal(host_key_check[0]) * 16 +
            hex2decimal(host_key_check[1]);
        if (c - *fingerprint != 0)
            return c - *fingerprint;
        fingerprint++;
        len--;
        host_key_check += 2;
    }
    return *host_key_check - '\0';
}

static int
check_host_key_hash(BDRVSSHState *s, const char *hash,
                    int hash_type, size_t fingerprint_len, Error **errp)
{
    const char *fingerprint;

    fingerprint = libssh2_hostkey_hash(s->session, hash_type);
    if (!fingerprint) {
        session_error_setg(errp, s, "failed to read remote host key");
        return -EINVAL;
    }

    if(compare_fingerprint((unsigned char *) fingerprint, fingerprint_len,
                           hash) != 0) {
        error_setg(errp, "remote host key does not match host_key_check '%s'",
                   hash);
        return -EPERM;
    }

    return 0;
}

static int check_host_key(BDRVSSHState *s, const char *host, int port,
                          const char *host_key_check, Error **errp)
{
    /* host_key_check=no */
    if (strcmp(host_key_check, "no") == 0) {
        return 0;
    }

    /* host_key_check=md5:xx:yy:zz:... */
    if (strncmp(host_key_check, "md5:", 4) == 0) {
        return check_host_key_hash(s, &host_key_check[4],
                                   LIBSSH2_HOSTKEY_HASH_MD5, 16, errp);
    }

    /* host_key_check=sha1:xx:yy:zz:... */
    if (strncmp(host_key_check, "sha1:", 5) == 0) {
        return check_host_key_hash(s, &host_key_check[5],
                                   LIBSSH2_HOSTKEY_HASH_SHA1, 20, errp);
    }

    /* host_key_check=yes */
    if (strcmp(host_key_check, "yes") == 0) {
        return check_host_key_knownhosts(s, host, port, errp);
    }

    error_setg(errp, "unknown host_key_check setting (%s)", host_key_check);
    return -EINVAL;
}

static int authenticate(BDRVSSHState *s, const char *user, Error **errp)
{
    int r, ret;
    const char *userauthlist;
    LIBSSH2_AGENT *agent = NULL;
    struct libssh2_agent_publickey *identity;
    struct libssh2_agent_publickey *prev_identity = NULL;

    userauthlist = libssh2_userauth_list(s->session, user, strlen(user));
    if (strstr(userauthlist, "publickey") == NULL) {
        ret = -EPERM;
        error_setg(errp,
                "remote server does not support \"publickey\" authentication");
        goto out;
    }

    /* Connect to ssh-agent and try each identity in turn. */
    agent = libssh2_agent_init(s->session);
    if (!agent) {
        ret = -EINVAL;
        session_error_setg(errp, s, "failed to initialize ssh-agent support");
        goto out;
    }
    if (libssh2_agent_connect(agent)) {
        ret = -ECONNREFUSED;
        session_error_setg(errp, s, "failed to connect to ssh-agent");
        goto out;
    }
    if (libssh2_agent_list_identities(agent)) {
        ret = -EINVAL;
        session_error_setg(errp, s,
                           "failed requesting identities from ssh-agent");
        goto out;
    }

    for(;;) {
        r = libssh2_agent_get_identity(agent, &identity, prev_identity);
        if (r == 1) {           /* end of list */
            break;
        }
        if (r < 0) {
            ret = -EINVAL;
            session_error_setg(errp, s,
                               "failed to obtain identity from ssh-agent");
            goto out;
        }
        r = libssh2_agent_userauth(agent, user, identity);
        if (r == 0) {
            /* Authenticated! */
            ret = 0;
            goto out;
        }
        /* Failed to authenticate with this identity, try the next one. */
        prev_identity = identity;
    }

    ret = -EPERM;
    error_setg(errp, "failed to authenticate using publickey authentication "
               "and the identities held by your ssh-agent");

 out:
    if (agent != NULL) {
        /* Note: libssh2 implementation implicitly calls
         * libssh2_agent_disconnect if necessary.
         */
        libssh2_agent_free(agent);
    }

    return ret;
}

static int connect_to_ssh(BDRVSSHState *s, QDict *options,
                          int ssh_flags, int creat_mode, Error **errp)
{
    int r, ret;
    const char *host, *user, *path, *host_key_check;
    int port;

    host = qdict_get_str(options, "host");

    if (qdict_haskey(options, "port")) {
        port = qdict_get_int(options, "port");
    } else {
        port = 22;
    }

    path = qdict_get_str(options, "path");

    if (qdict_haskey(options, "user")) {
        user = qdict_get_str(options, "user");
    } else {
        user = g_get_user_name();
        if (!user) {
            error_setg_errno(errp, errno, "Can't get user name");
            ret = -errno;
            goto err;
        }
    }

    if (qdict_haskey(options, "host_key_check")) {
        host_key_check = qdict_get_str(options, "host_key_check");
    } else {
        host_key_check = "yes";
    }

    /* Construct the host:port name for inet_connect. */
    g_free(s->hostport);
    s->hostport = g_strdup_printf("%s:%d", host, port);

    /* Open the socket and connect. */
    s->sock = inet_connect(s->hostport, errp);
    if (s->sock < 0) {
        ret = -errno;
        goto err;
    }

    /* Create SSH session. */
    s->session = libssh2_session_init();
    if (!s->session) {
        ret = -EINVAL;
        session_error_setg(errp, s, "failed to initialize libssh2 session");
        goto err;
    }

#if TRACE_LIBSSH2 != 0
    libssh2_trace(s->session, TRACE_LIBSSH2);
#endif

    r = libssh2_session_handshake(s->session, s->sock);
    if (r != 0) {
        ret = -EINVAL;
        session_error_setg(errp, s, "failed to establish SSH session");
        goto err;
    }

    /* Check the remote host's key against known_hosts. */
    ret = check_host_key(s, host, port, host_key_check, errp);
    if (ret < 0) {
        goto err;
    }

    /* Authenticate. */
    ret = authenticate(s, user, errp);
    if (ret < 0) {
        goto err;
    }

    /* Start SFTP. */
    s->sftp = libssh2_sftp_init(s->session);
    if (!s->sftp) {
        session_error_setg(errp, s, "failed to initialize sftp handle");
        ret = -EINVAL;
        goto err;
    }

    /* Open the remote file. */
    DPRINTF("opening file %s flags=0x%x creat_mode=0%o",
            path, ssh_flags, creat_mode);
    s->sftp_handle = libssh2_sftp_open(s->sftp, path, ssh_flags, creat_mode);
    if (!s->sftp_handle) {
        session_error_setg(errp, s, "failed to open remote file '%s'", path);
        ret = -EINVAL;
        goto err;
    }

    r = libssh2_sftp_fstat(s->sftp_handle, &s->attrs);
    if (r < 0) {
        sftp_error_setg(errp, s, "failed to read file attributes");
        return -EINVAL;
    }

    /* Delete the options we've used; any not deleted will cause the
     * block layer to give an error about unused options.
     */
    qdict_del(options, "host");
    qdict_del(options, "port");
    qdict_del(options, "user");
    qdict_del(options, "path");
    qdict_del(options, "host_key_check");

    return 0;

 err:
    if (s->sftp_handle) {
        libssh2_sftp_close(s->sftp_handle);
    }
    s->sftp_handle = NULL;
    if (s->sftp) {
        libssh2_sftp_shutdown(s->sftp);
    }
    s->sftp = NULL;
    if (s->session) {
        libssh2_session_disconnect(s->session,
                                   "from qemu ssh client: "
                                   "error opening connection");
        libssh2_session_free(s->session);
    }
    s->session = NULL;

    return ret;
}

static int ssh_file_open(BlockDriverState *bs, QDict *options, int bdrv_flags,
                         Error **errp)
{
    BDRVSSHState *s = bs->opaque;
    int ret;
    int ssh_flags;

    ssh_state_init(s);

    ssh_flags = LIBSSH2_FXF_READ;
    if (bdrv_flags & BDRV_O_RDWR) {
        ssh_flags |= LIBSSH2_FXF_WRITE;
    }

    /* Start up SSH. */
    ret = connect_to_ssh(s, options, ssh_flags, 0, errp);
    if (ret < 0) {
        goto err;
    }

    /* Go non-blocking. */
    libssh2_session_set_blocking(s->session, 0);

    return 0;

 err:
    if (s->sock >= 0) {
        close(s->sock);
    }
    s->sock = -1;

    return ret;
}

static QemuOptsList ssh_create_opts = {
    .name = "ssh-create-opts",
    .head = QTAILQ_HEAD_INITIALIZER(ssh_create_opts.head),
    .desc = {
        {
            .name = BLOCK_OPT_SIZE,
            .type = QEMU_OPT_SIZE,
            .help = "Virtual disk size"
        },
        { /* end of list */ }
    }
};

static int ssh_create(const char *filename, QemuOpts *opts, Error **errp)
{
    int r, ret;
    int64_t total_size = 0;
    QDict *uri_options = NULL;
    BDRVSSHState s;
    ssize_t r2;
    char c[1] = { '\0' };

    ssh_state_init(&s);

    /* Get desired file size. */
    total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
                          BDRV_SECTOR_SIZE);
    DPRINTF("total_size=%" PRIi64, total_size);

    uri_options = qdict_new();
    r = parse_uri(filename, uri_options, errp);
    if (r < 0) {
        ret = r;
        goto out;
    }

    r = connect_to_ssh(&s, uri_options,
                       LIBSSH2_FXF_READ|LIBSSH2_FXF_WRITE|
                       LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC,
                       0644, errp);
    if (r < 0) {
        ret = r;
        goto out;
    }

    if (total_size > 0) {
        libssh2_sftp_seek64(s.sftp_handle, total_size-1);
        r2 = libssh2_sftp_write(s.sftp_handle, c, 1);
        if (r2 < 0) {
            sftp_error_setg(errp, &s, "truncate failed");
            ret = -EINVAL;
            goto out;
        }
        s.attrs.filesize = total_size;
    }

    ret = 0;

 out:
    ssh_state_free(&s);
    if (uri_options != NULL) {
        QDECREF(uri_options);
    }
    return ret;
}

static void ssh_close(BlockDriverState *bs)
{
    BDRVSSHState *s = bs->opaque;

    ssh_state_free(s);
}

static int ssh_has_zero_init(BlockDriverState *bs)
{
    BDRVSSHState *s = bs->opaque;
    /* Assume false, unless we can positively prove it's true. */
    int has_zero_init = 0;

    if (s->attrs.flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
        if (s->attrs.permissions & LIBSSH2_SFTP_S_IFREG) {
            has_zero_init = 1;
        }
    }

    return has_zero_init;
}

static void restart_coroutine(void *opaque)
{
    Coroutine *co = opaque;

    DPRINTF("co=%p", co);

    qemu_coroutine_enter(co, NULL);
}

static coroutine_fn void set_fd_handler(BDRVSSHState *s, BlockDriverState *bs)
{
    int r;
    IOHandler *rd_handler = NULL, *wr_handler = NULL;
    Coroutine *co = qemu_coroutine_self();

    r = libssh2_session_block_directions(s->session);

    if (r & LIBSSH2_SESSION_BLOCK_INBOUND) {
        rd_handler = restart_coroutine;
    }
    if (r & LIBSSH2_SESSION_BLOCK_OUTBOUND) {
        wr_handler = restart_coroutine;
    }

    DPRINTF("s->sock=%d rd_handler=%p wr_handler=%p", s->sock,
            rd_handler, wr_handler);

    aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock,
                       rd_handler, wr_handler, co);
}

static coroutine_fn void clear_fd_handler(BDRVSSHState *s,
                                          BlockDriverState *bs)
{
    DPRINTF("s->sock=%d", s->sock);
    aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock, NULL, NULL, NULL);
}

/* A non-blocking call returned EAGAIN, so yield, ensuring the
 * handlers are set up so that we'll be rescheduled when there is an
 * interesting event on the socket.
 */
static coroutine_fn void co_yield(BDRVSSHState *s, BlockDriverState *bs)
{
    set_fd_handler(s, bs);
    qemu_coroutine_yield();
    clear_fd_handler(s, bs);
}

/* SFTP has a function `libssh2_sftp_seek64' which seeks to a position
 * in the remote file.  Notice that it just updates a field in the
 * sftp_handle structure, so there is no network traffic and it cannot
 * fail.
 *
 * However, `libssh2_sftp_seek64' does have a catastrophic effect on
 * performance since it causes the handle to throw away all in-flight
 * reads and buffered readahead data.  Therefore this function tries
 * to be intelligent about when to call the underlying libssh2 function.
 */
#define SSH_SEEK_WRITE 0
#define SSH_SEEK_READ  1
#define SSH_SEEK_FORCE 2

static void ssh_seek(BDRVSSHState *s, int64_t offset, int flags)
{
    bool op_read = (flags & SSH_SEEK_READ) != 0;
    bool force = (flags & SSH_SEEK_FORCE) != 0;

    if (force || op_read != s->offset_op_read || offset != s->offset) {
        DPRINTF("seeking to offset=%" PRIi64, offset);
        libssh2_sftp_seek64(s->sftp_handle, offset);
        s->offset = offset;
        s->offset_op_read = op_read;
    }
}

static coroutine_fn int ssh_read(BDRVSSHState *s, BlockDriverState *bs,
                                 int64_t offset, size_t size,
                                 QEMUIOVector *qiov)
{
    ssize_t r;
    size_t got;
    char *buf, *end_of_vec;
    struct iovec *i;

    DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);

    ssh_seek(s, offset, SSH_SEEK_READ);

    /* This keeps track of the current iovec element ('i'), where we
     * will write to next ('buf'), and the end of the current iovec
     * ('end_of_vec').
     */
    i = &qiov->iov[0];
    buf = i->iov_base;
    end_of_vec = i->iov_base + i->iov_len;

    /* libssh2 has a hard-coded limit of 2000 bytes per request,
     * although it will also do readahead behind our backs.  Therefore
     * we may have to do repeated reads here until we have read 'size'
     * bytes.
     */
    for (got = 0; got < size; ) {
    again:
        DPRINTF("sftp_read buf=%p size=%zu", buf, end_of_vec - buf);
        r = libssh2_sftp_read(s->sftp_handle, buf, end_of_vec - buf);
        DPRINTF("sftp_read returned %zd", r);

        if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
            co_yield(s, bs);
            goto again;
        }
        if (r < 0) {
            sftp_error_report(s, "read failed");
            s->offset = -1;
            return -EIO;
        }
        if (r == 0) {
            /* EOF: Short read so pad the buffer with zeroes and return it. */
            qemu_iovec_memset(qiov, got, 0, size - got);
            return 0;
        }

        got += r;
        buf += r;
        s->offset += r;
        if (buf >= end_of_vec && got < size) {
            i++;
            buf = i->iov_base;
            end_of_vec = i->iov_base + i->iov_len;
        }
    }

    return 0;
}

static coroutine_fn int ssh_co_readv(BlockDriverState *bs,
                                     int64_t sector_num,
                                     int nb_sectors, QEMUIOVector *qiov)
{
    BDRVSSHState *s = bs->opaque;
    int ret;

    qemu_co_mutex_lock(&s->lock);
    ret = ssh_read(s, bs, sector_num * BDRV_SECTOR_SIZE,
                   nb_sectors * BDRV_SECTOR_SIZE, qiov);
    qemu_co_mutex_unlock(&s->lock);

    return ret;
}

static int ssh_write(BDRVSSHState *s, BlockDriverState *bs,
                     int64_t offset, size_t size,
                     QEMUIOVector *qiov)
{
    ssize_t r;
    size_t written;
    char *buf, *end_of_vec;
    struct iovec *i;

    DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);

    ssh_seek(s, offset, SSH_SEEK_WRITE);

    /* This keeps track of the current iovec element ('i'), where we
     * will read from next ('buf'), and the end of the current iovec
     * ('end_of_vec').
     */
    i = &qiov->iov[0];
    buf = i->iov_base;
    end_of_vec = i->iov_base + i->iov_len;

    for (written = 0; written < size; ) {
    again:
        DPRINTF("sftp_write buf=%p size=%zu", buf, end_of_vec - buf);
        r = libssh2_sftp_write(s->sftp_handle, buf, end_of_vec - buf);
        DPRINTF("sftp_write returned %zd", r);

        if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
            co_yield(s, bs);
            goto again;
        }
        if (r < 0) {
            sftp_error_report(s, "write failed");
            s->offset = -1;
            return -EIO;
        }
        /* The libssh2 API is very unclear about this.  A comment in
         * the code says "nothing was acked, and no EAGAIN was
         * received!" which apparently means that no data got sent
         * out, and the underlying channel didn't return any EAGAIN
         * indication.  I think this is a bug in either libssh2 or
         * OpenSSH (server-side).  In any case, forcing a seek (to
         * discard libssh2 internal buffers), and then trying again
         * works for me.
         */
        if (r == 0) {
            ssh_seek(s, offset + written, SSH_SEEK_WRITE|SSH_SEEK_FORCE);
            co_yield(s, bs);
            goto again;
        }

        written += r;
        buf += r;
        s->offset += r;
        if (buf >= end_of_vec && written < size) {
            i++;
            buf = i->iov_base;
            end_of_vec = i->iov_base + i->iov_len;
        }

        if (offset + written > s->attrs.filesize)
            s->attrs.filesize = offset + written;
    }

    return 0;
}

static coroutine_fn int ssh_co_writev(BlockDriverState *bs,
                                      int64_t sector_num,
                                      int nb_sectors, QEMUIOVector *qiov)
{
    BDRVSSHState *s = bs->opaque;
    int ret;

    qemu_co_mutex_lock(&s->lock);
    ret = ssh_write(s, bs, sector_num * BDRV_SECTOR_SIZE,
                    nb_sectors * BDRV_SECTOR_SIZE, qiov);
    qemu_co_mutex_unlock(&s->lock);

    return ret;
}

static void unsafe_flush_warning(BDRVSSHState *s, const char *what)
{
    if (!s->unsafe_flush_warning) {
        error_report("warning: ssh server %s does not support fsync",
                     s->hostport);
        if (what) {
            error_report("to support fsync, you need %s", what);
        }
        s->unsafe_flush_warning = true;
    }
}

#ifdef HAS_LIBSSH2_SFTP_FSYNC

static coroutine_fn int ssh_flush(BDRVSSHState *s, BlockDriverState *bs)
{
    int r;

    DPRINTF("fsync");
 again:
    r = libssh2_sftp_fsync(s->sftp_handle);
    if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
        co_yield(s, bs);
        goto again;
    }
    if (r == LIBSSH2_ERROR_SFTP_PROTOCOL &&
        libssh2_sftp_last_error(s->sftp) == LIBSSH2_FX_OP_UNSUPPORTED) {
        unsafe_flush_warning(s, "OpenSSH >= 6.3");
        return 0;
    }
    if (r < 0) {
        sftp_error_report(s, "fsync failed");
        return -EIO;
    }

    return 0;
}

static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
{
    BDRVSSHState *s = bs->opaque;
    int ret;

    qemu_co_mutex_lock(&s->lock);
    ret = ssh_flush(s, bs);
    qemu_co_mutex_unlock(&s->lock);

    return ret;
}

#else /* !HAS_LIBSSH2_SFTP_FSYNC */

static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
{
    BDRVSSHState *s = bs->opaque;

    unsafe_flush_warning(s, "libssh2 >= 1.4.4");
    return 0;
}

#endif /* !HAS_LIBSSH2_SFTP_FSYNC */

static int64_t ssh_getlength(BlockDriverState *bs)
{
    BDRVSSHState *s = bs->opaque;
    int64_t length;

    /* Note we cannot make a libssh2 call here. */
    length = (int64_t) s->attrs.filesize;
    DPRINTF("length=%" PRIi64, length);

    return length;
}

static BlockDriver bdrv_ssh = {
    .format_name                  = "ssh",
    .protocol_name                = "ssh",
    .instance_size                = sizeof(BDRVSSHState),
    .bdrv_parse_filename          = ssh_parse_filename,
    .bdrv_file_open               = ssh_file_open,
    .bdrv_create                  = ssh_create,
    .bdrv_close                   = ssh_close,
    .bdrv_has_zero_init           = ssh_has_zero_init,
    .bdrv_co_readv                = ssh_co_readv,
    .bdrv_co_writev               = ssh_co_writev,
    .bdrv_getlength               = ssh_getlength,
    .bdrv_co_flush_to_disk        = ssh_co_flush,
    .create_opts                  = &ssh_create_opts,
};

static void bdrv_ssh_init(void)
{
    int r;

    r = libssh2_init(0);
    if (r != 0) {
        fprintf(stderr, "libssh2 initialization failed, %d\n", r);
        exit(EXIT_FAILURE);
    }

    bdrv_register(&bdrv_ssh);
}

block_init(bdrv_ssh_init);
OpenPOWER on IntegriCloud