/* * 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 "qemu/osdep.h" #include <libssh2.h> #include <libssh2_sftp.h> #include "block/block_int.h" #include "block/qdict.h" #include "qapi/error.h" #include "qemu/error-report.h" #include "qemu/option.h" #include "qemu/cutils.h" #include "qemu/sockets.h" #include "qemu/uri.h" #include "qapi/qapi-visit-sockets.h" #include "qapi/qapi-visit-block-core.h" #include "qapi/qmp/qdict.h" #include "qapi/qmp/qstring.h" #include "qapi/qobject-input-visitor.h" #include "qapi/qobject-output-visitor.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; InetSocketAddress *inet; /* Used to warn if 'flush' is not supported. */ 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) { 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; char *port_str; int i; uri = uri_parse(filename); if (!uri) { return -EINVAL; } if (g_strcmp0(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_str(options, "user", uri->user); } qdict_put_str(options, "server.host", uri->server); port_str = g_strdup_printf("%d", uri->port ?: 22); qdict_put_str(options, "server.port", port_str); g_free(port_str); qdict_put_str(options, "path", 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_str(options, "host_key_check", qp->p[i].value); } } query_params_free(qp); uri_free(uri); return 0; err: if (uri) { uri_free(uri); } return -EINVAL; } static bool ssh_has_filename_options_conflict(QDict *options, Error **errp) { const QDictEntry *qe; for (qe = qdict_first(options); qe; qe = qdict_next(options, qe)) { if (!strcmp(qe->key, "host") || !strcmp(qe->key, "port") || !strcmp(qe->key, "path") || !strcmp(qe->key, "user") || !strcmp(qe->key, "host_key_check") || strstart(qe->key, "server.", NULL)) { error_setg(errp, "Option '%s' cannot be used with a file name", qe->key); return true; } } return false; } static void ssh_parse_filename(const char *filename, QDict *options, Error **errp) { if (ssh_has_filename_options_conflict(options, errp)) { 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, SshHostKeyCheck *hkc, Error **errp) { SshHostKeyCheckMode mode; if (hkc) { mode = hkc->mode; } else { mode = SSH_HOST_KEY_CHECK_MODE_KNOWN_HOSTS; } switch (mode) { case SSH_HOST_KEY_CHECK_MODE_NONE: return 0; case SSH_HOST_KEY_CHECK_MODE_HASH: if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_MD5) { return check_host_key_hash(s, hkc->u.hash.hash, LIBSSH2_HOSTKEY_HASH_MD5, 16, errp); } else if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_SHA1) { return check_host_key_hash(s, hkc->u.hash.hash, LIBSSH2_HOSTKEY_HASH_SHA1, 20, errp); } g_assert_not_reached(); break; case SSH_HOST_KEY_CHECK_MODE_KNOWN_HOSTS: return check_host_key_knownhosts(s, host, port, errp); default: g_assert_not_reached(); } 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 QemuOptsList ssh_runtime_opts = { .name = "ssh", .head = QTAILQ_HEAD_INITIALIZER(ssh_runtime_opts.head), .desc = { { .name = "host", .type = QEMU_OPT_STRING, .help = "Host to connect to", }, { .name = "port", .type = QEMU_OPT_NUMBER, .help = "Port to connect to", }, { .name = "host_key_check", .type = QEMU_OPT_STRING, .help = "Defines how and what to check the host key against", }, { /* end of list */ } }, }; static bool ssh_process_legacy_options(QDict *output_opts, QemuOpts *legacy_opts, Error **errp) { const char *host = qemu_opt_get(legacy_opts, "host"); const char *port = qemu_opt_get(legacy_opts, "port"); const char *host_key_check = qemu_opt_get(legacy_opts, "host_key_check"); if (!host && port) { error_setg(errp, "port may not be used without host"); return false; } if (host) { qdict_put_str(output_opts, "server.host", host); qdict_put_str(output_opts, "server.port", port ?: stringify(22)); } if (host_key_check) { if (strcmp(host_key_check, "no") == 0) { qdict_put_str(output_opts, "host-key-check.mode", "none"); } else if (strncmp(host_key_check, "md5:", 4) == 0) { qdict_put_str(output_opts, "host-key-check.mode", "hash"); qdict_put_str(output_opts, "host-key-check.type", "md5"); qdict_put_str(output_opts, "host-key-check.hash", &host_key_check[4]); } else if (strncmp(host_key_check, "sha1:", 5) == 0) { qdict_put_str(output_opts, "host-key-check.mode", "hash"); qdict_put_str(output_opts, "host-key-check.type", "sha1"); qdict_put_str(output_opts, "host-key-check.hash", &host_key_check[5]); } else if (strcmp(host_key_check, "yes") == 0) { qdict_put_str(output_opts, "host-key-check.mode", "known_hosts"); } else { error_setg(errp, "unknown host_key_check setting (%s)", host_key_check); return false; } } return true; } static BlockdevOptionsSsh *ssh_parse_options(QDict *options, Error **errp) { BlockdevOptionsSsh *result = NULL; QemuOpts *opts = NULL; Error *local_err = NULL; const QDictEntry *e; Visitor *v; /* Translate legacy options */ opts = qemu_opts_create(&ssh_runtime_opts, NULL, 0, &error_abort); qemu_opts_absorb_qdict(opts, options, &local_err); if (local_err) { error_propagate(errp, local_err); goto fail; } if (!ssh_process_legacy_options(options, opts, errp)) { goto fail; } /* Create the QAPI object */ v = qobject_input_visitor_new_flat_confused(options, errp); if (!v) { goto fail; } visit_type_BlockdevOptionsSsh(v, NULL, &result, &local_err); visit_free(v); if (local_err) { error_propagate(errp, local_err); goto fail; } /* Remove the processed options from the QDict (the visitor processes * _all_ options in the QDict) */ while ((e = qdict_first(options))) { qdict_del(options, e->key); } fail: qemu_opts_del(opts); return result; } static int connect_to_ssh(BDRVSSHState *s, BlockdevOptionsSsh *opts, int ssh_flags, int creat_mode, Error **errp) { int r, ret; const char *user; long port = 0; if (opts->has_user) { user = opts->user; } else { user = g_get_user_name(); if (!user) { error_setg_errno(errp, errno, "Can't get user name"); ret = -errno; goto err; } } /* Pop the config into our state object, Exit if invalid */ s->inet = opts->server; opts->server = NULL; if (qemu_strtol(s->inet->port, NULL, 10, &port) < 0) { error_setg(errp, "Use only numeric port value"); ret = -EINVAL; goto err; } /* Open the socket and connect. */ s->sock = inet_connect_saddr(s->inet, errp); if (s->sock < 0) { ret = -EIO; 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, s->inet->host, port, opts->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", opts->path, ssh_flags, creat_mode); s->sftp_handle = libssh2_sftp_open(s->sftp, opts->path, ssh_flags, creat_mode); if (!s->sftp_handle) { session_error_setg(errp, s, "failed to open remote file '%s'", opts->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; } 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; BlockdevOptionsSsh *opts; 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; } opts = ssh_parse_options(options, errp); if (opts == NULL) { return -EINVAL; } /* Start up SSH. */ ret = connect_to_ssh(s, opts, ssh_flags, 0, errp); if (ret < 0) { goto err; } /* Go non-blocking. */ libssh2_session_set_blocking(s->session, 0); qapi_free_BlockdevOptionsSsh(opts); return 0; err: if (s->sock >= 0) { close(s->sock); } s->sock = -1; qapi_free_BlockdevOptionsSsh(opts); return ret; } /* Note: This is a blocking operation */ static int ssh_grow_file(BDRVSSHState *s, int64_t offset, Error **errp) { ssize_t ret; char c[1] = { '\0' }; int was_blocking = libssh2_session_get_blocking(s->session); /* offset must be strictly greater than the current size so we do * not overwrite anything */ assert(offset > 0 && offset > s->attrs.filesize); libssh2_session_set_blocking(s->session, 1); libssh2_sftp_seek64(s->sftp_handle, offset - 1); ret = libssh2_sftp_write(s->sftp_handle, c, 1); libssh2_session_set_blocking(s->session, was_blocking); if (ret < 0) { sftp_error_setg(errp, s, "Failed to grow file"); return -EIO; } s->attrs.filesize = offset; return 0; } 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_co_create(BlockdevCreateOptions *options, Error **errp) { BlockdevCreateOptionsSsh *opts = &options->u.ssh; BDRVSSHState s; int ret; assert(options->driver == BLOCKDEV_DRIVER_SSH); ssh_state_init(&s); ret = connect_to_ssh(&s, opts->location, LIBSSH2_FXF_READ|LIBSSH2_FXF_WRITE| LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC, 0644, errp); if (ret < 0) { goto fail; } if (opts->size > 0) { ret = ssh_grow_file(&s, opts->size, errp); if (ret < 0) { goto fail; } } ret = 0; fail: ssh_state_free(&s); return ret; } static int coroutine_fn ssh_co_create_opts(const char *filename, QemuOpts *opts, Error **errp) { BlockdevCreateOptions *create_options; BlockdevCreateOptionsSsh *ssh_opts; int ret; QDict *uri_options = NULL; create_options = g_new0(BlockdevCreateOptions, 1); create_options->driver = BLOCKDEV_DRIVER_SSH; ssh_opts = &create_options->u.ssh; /* Get desired file size. */ ssh_opts->size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0), BDRV_SECTOR_SIZE); DPRINTF("total_size=%" PRIi64, ssh_opts->size); uri_options = qdict_new(); ret = parse_uri(filename, uri_options, errp); if (ret < 0) { goto out; } ssh_opts->location = ssh_parse_options(uri_options, errp); if (ssh_opts->location == NULL) { ret = -EINVAL; goto out; } ret = ssh_co_create(create_options, errp); out: qobject_unref(uri_options); qapi_free_BlockdevCreateOptions(create_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; } typedef struct BDRVSSHRestart { BlockDriverState *bs; Coroutine *co; } BDRVSSHRestart; static void restart_coroutine(void *opaque) { BDRVSSHRestart *restart = opaque; BlockDriverState *bs = restart->bs; BDRVSSHState *s = bs->opaque; AioContext *ctx = bdrv_get_aio_context(bs); DPRINTF("co=%p", restart->co); aio_set_fd_handler(ctx, s->sock, false, NULL, NULL, NULL, NULL); aio_co_wake(restart->co); } /* 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) { int r; IOHandler *rd_handler = NULL, *wr_handler = NULL; BDRVSSHRestart restart = { .bs = bs, .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, false, rd_handler, wr_handler, NULL, &restart); qemu_coroutine_yield(); DPRINTF("s->sock=%d - back", s->sock); } /* 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, int flags) { BDRVSSHState *s = bs->opaque; int ret; assert(!flags); 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) { warn_report("ssh server %s does not support fsync", s->inet->host); 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 int coroutine_fn ssh_co_truncate(BlockDriverState *bs, int64_t offset, PreallocMode prealloc, Error **errp) { BDRVSSHState *s = bs->opaque; if (prealloc != PREALLOC_MODE_OFF) { error_setg(errp, "Unsupported preallocation mode '%s'", PreallocMode_str(prealloc)); return -ENOTSUP; } if (offset < s->attrs.filesize) { error_setg(errp, "ssh driver does not support shrinking files"); return -ENOTSUP; } if (offset == s->attrs.filesize) { return 0; } return ssh_grow_file(s, offset, errp); } 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_co_create = ssh_co_create, .bdrv_co_create_opts = ssh_co_create_opts, .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_truncate = ssh_co_truncate, .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);