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xemu/block/ssh.c
Markus Armbruster 129c7d1c53 block: Document -drive problematic code and bugs 
-blockdev and blockdev_add convert their arguments via QObject to
BlockdevOptions for qmp_blockdev_add(), which converts them back to
QObject, then to a flattened QDict.  The QDict's members are typed
according to the QAPI schema.

-drive converts its argument via QemuOpts to a (flat) QDict.  This
QDict's members are all QString.

Thus, the QType of a flat QDict member depends on whether it comes
from -drive or -blockdev/blockdev_add, except when the QAPI type maps
to QString, which is the case for 'str' and enumeration types.

The block layer core extracts generic configuration from the flat
QDict, and the block driver extracts driver-specific configuration.

Both commonly do so by converting (parts of) the flat QDict to
QemuOpts, which turns all values into strings.  Not exactly elegant,
but correct.

However, A few places access the flat QDict directly:

* Most of them access members that are always QString.  Correct.

* bdrv_open_inherit() accesses a boolean, carefully.  Correct.

* nfs_config() uses a QObject input visitor.  Correct only because the
  visited type contains nothing but QStrings.

* nbd_config() and ssh_config() use a QObject input visitor, and the
  visited types contain non-QStrings: InetSocketAddress members
  @numeric, @to, @ipv4, @ipv6.  -drive works as long as you don't try
  to use them (they're all optional).  @to is ignored anyway.

  Reproducer:
  -drive driver=ssh,server.host=h,server.port=22,server.ipv4,path=p
  -drive driver=nbd,server.type=inet,server.data.host=h,server.data.port=22,server.data.ipv4
  both fail with "Invalid parameter type for 'data.ipv4', expected: boolean"

Add suitable comments to all these places.  Mark the buggy ones FIXME.

"Fortunately", -drive's driver-specific options are entirely
undocumented.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1490895797-29094-5-git-send-email-armbru@redhat.com
[mreitz: Fixed two typos]
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-04-03 17:11:39 +02:00

1221 lines
34 KiB
C
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/*
* 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 "qapi/error.h"
#include "qemu/error-report.h"
#include "qemu/cutils.h"
#include "qemu/sockets.h"
#include "qemu/uri.h"
#include "qapi-visit.h"
#include "qapi/qmp/qint.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 (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, "server.host", qstring_from_str(uri->server));
port_str = g_strdup_printf("%d", uri->port ?: 22);
qdict_put(options, "server.port", qstring_from_str(port_str));
g_free(port_str);
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 (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,
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 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 = "path",
.type = QEMU_OPT_STRING,
.help = "Path of the image on the host",
},
{
.name = "user",
.type = QEMU_OPT_STRING,
.help = "User as which to connect",
},
{
.name = "host_key_check",
.type = QEMU_OPT_STRING,
.help = "Defines how and what to check the host key against",
},
},
};
static bool ssh_process_legacy_socket_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");
if (!host && port) {
error_setg(errp, "port may not be used without host");
return false;
}
if (host) {
qdict_put(output_opts, "server.host", qstring_from_str(host));
qdict_put(output_opts, "server.port",
qstring_from_str(port ?: stringify(22)));
}
return true;
}
static InetSocketAddress *ssh_config(QDict *options, Error **errp)
{
InetSocketAddress *inet = NULL;
QDict *addr = NULL;
QObject *crumpled_addr = NULL;
Visitor *iv = NULL;
Error *local_error = NULL;
qdict_extract_subqdict(options, &addr, "server.");
if (!qdict_size(addr)) {
error_setg(errp, "SSH server address missing");
goto out;
}
crumpled_addr = qdict_crumple(addr, errp);
if (!crumpled_addr) {
goto out;
}
/*
* FIXME .numeric, .to, .ipv4 or .ipv6 don't work with -drive.
* .to doesn't matter, it's ignored anyway.
* That's because when @options come from -blockdev or
* blockdev_add, members are typed according to the QAPI schema,
* but when they come from -drive, they're all QString. The
* visitor expects the former.
*/
iv = qobject_input_visitor_new(crumpled_addr);
visit_type_InetSocketAddress(iv, NULL, &inet, &local_error);
if (local_error) {
error_propagate(errp, local_error);
goto out;
}
out:
QDECREF(addr);
qobject_decref(crumpled_addr);
visit_free(iv);
return inet;
}
static int connect_to_ssh(BDRVSSHState *s, QDict *options,
int ssh_flags, int creat_mode, Error **errp)
{
int r, ret;
QemuOpts *opts = NULL;
Error *local_err = NULL;
const char *user, *path, *host_key_check;
long port = 0;
opts = qemu_opts_create(&ssh_runtime_opts, NULL, 0, &error_abort);
qemu_opts_absorb_qdict(opts, options, &local_err);
if (local_err) {
ret = -EINVAL;
error_propagate(errp, local_err);
goto err;
}
if (!ssh_process_legacy_socket_options(options, opts, errp)) {
ret = -EINVAL;
goto err;
}
path = qemu_opt_get(opts, "path");
if (!path) {
ret = -EINVAL;
error_setg(errp, "No path was specified");
goto err;
}
user = qemu_opt_get(opts, "user");
if (!user) {
user = g_get_user_name();
if (!user) {
error_setg_errno(errp, errno, "Can't get user name");
ret = -errno;
goto err;
}
}
host_key_check = qemu_opt_get(opts, "host_key_check");
if (!host_key_check) {
host_key_check = "yes";
}
/* Pop the config into our state object, Exit if invalid */
s->inet = ssh_config(options, errp);
if (!s->inet) {
ret = -EINVAL;
goto err;
}
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, NULL, NULL);
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, 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;
}
qemu_opts_del(opts);
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;
qemu_opts_del(opts);
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);
aio_co_wake(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;
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,
false, rd_handler, wr_handler, NULL, co);
qemu_coroutine_yield();
DPRINTF("s->sock=%d - back", s->sock);
aio_set_fd_handler(bdrv_get_aio_context(bs), s->sock, false,
NULL, NULL, NULL, NULL);
}
/* 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->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 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);
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