From: "Richard W.M. Jones" <rjo...@redhat.com>
qemu-system-x86_64 -drive file=ssh://hostname/some/image
QEMU will ssh into 'hostname' and open '/some/image' which is made
available as a standard block device.
You can specify a username (ssh://user@host/...) and/or a port number
(ssh://host:port/...).
Current limitations:
- Authentication must be done without passwords or passphrases, using
ssh-agent. Other authentication methods are not supported. (*)
- Does not check host key. (*)
- New remote files cannot be created. (*)
- Uses coroutine read/write, instead of true AIO. (libssh2 supports
non-blocking access, so this could be fixed with some effort).
- Blocks during connection and authentication.
(*) = potentially easy fix
This is implemented using libssh2 on the client side. The server just
requires a regular ssh daemon with sftp-server support. Most ssh
daemons on Unix/Linux systems will work out of the box.
---
block/Makefile.objs | 1 +
block/ssh.c | 514 ++++++++++++++++++++++++++++++++++++++++++++++++++++
configure | 47 +++++
qemu-doc.texi | 28 +++
4 files changed, 590 insertions(+)
create mode 100644 block/ssh.c
diff --git a/block/Makefile.objs b/block/Makefile.objs
index c067f38..6c4b5bc 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -13,6 +13,7 @@ block-obj-$(CONFIG_LIBISCSI) += iscsi.o
block-obj-$(CONFIG_CURL) += curl.o
block-obj-$(CONFIG_RBD) += rbd.o
block-obj-$(CONFIG_GLUSTERFS) += gluster.o
+block-obj-$(CONFIG_LIBSSH2) += ssh.o
endif
common-obj-y += stream.o
diff --git a/block/ssh.c b/block/ssh.c
new file mode 100644
index 0000000..7071cfd
--- /dev/null
+++ b/block/ssh.c
@@ -0,0 +1,514 @@
+/*
+ * Secure Shell (ssh) backend for QEMU.
+ *
+ * Copyright (C) 2013 Red Hat Inc., Richard W.M. Jones <rjo...@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+
+#ifndef _WIN32
+#include <pwd.h>
+#endif
+
+#include <libssh2.h>
+#include <libssh2_sftp.h>
+
+#include "block/block_int.h"
+#include "qemu/sockets.h"
+#include "qemu/uri.h"
+
+#define SECTOR_SIZE 512
+
+static void __attribute__((constructor)) ssh_init(void)
+{
+ int r;
+
+ r = libssh2_init(0);
+ if (r != 0) {
+ fprintf(stderr, "libssh2 initialization failed, %d\n", r);
+ exit(EXIT_FAILURE);
+ }
+}
+
+typedef struct BDRVSSHState {
+ CoMutex lock; /* coroutine lock */
+
+ /* configuration */
+ char *user; /* remote username */
+ char *host; /* hostname and port */
+ char *path; /* path to remote disk image */
+
+ /* ssh connection */
+ int sock; /* socket */
+ LIBSSH2_SESSION *session; /* ssh session */
+ LIBSSH2_SFTP *sftp; /* sftp session */
+ LIBSSH2_SFTP_HANDLE *sftp_handle; /* sftp remote file handle */
+
+ /* file attributes (at open) */
+ LIBSSH2_SFTP_ATTRIBUTES attrs;
+} BDRVSSHState;
+
+/* Wrappers around error_report which make sure to dump as much
+ * information from libssh2 as possible.
+ */
+static void
+session_error_report(BDRVSSHState *s, const char *fs, ...)
+{
+ va_list args;
+
+ va_start(args, fs);
+
+ if ((s)->session) {
+ char *ssh_err;
+ int ssh_err_len = sizeof ssh_err;
+ int ssh_err_code;
+
+ libssh2_session_last_error((s)->session,
+ &ssh_err, &ssh_err_len, 0);
+ /* This is not an errno. See <libssh2.h>. */
+ ssh_err_code = libssh2_session_last_errno((s)->session);
+
+ error_vprintf(fs, args);
+ error_printf(": %s (libssh2 error code: %d)", ssh_err, ssh_err_code);
+ }
+ else {
+ error_vprintf(fs, args);
+ }
+
+ va_end(args);
+ error_printf("\n");
+}
+
+static void
+sftp_error_report(BDRVSSHState *s, const char *fs, ...)
+{
+ va_list args;
+
+ va_start(args, fs);
+
+ if ((s)->sftp) {
+ char *ssh_err;
+ int ssh_err_len = sizeof ssh_err;
+ int ssh_err_code;
+ unsigned long sftp_err_code;
+
+ libssh2_session_last_error((s)->session,
+ &ssh_err, &ssh_err_len, 0);
+ /* This is not an errno. See <libssh2.h>. */
+ ssh_err_code = libssh2_session_last_errno((s)->session);
+ /* See <libssh2_sftp.h>. */
+ sftp_err_code = libssh2_sftp_last_error((s)->sftp);
+
+ error_vprintf(fs, args);
+ error_printf(": %s (libssh2 error code: %d, sftp error code: %lu)",
+ ssh_err, ssh_err_code, sftp_err_code);
+ }
+ else {
+ error_vprintf(fs, args);
+ }
+
+ va_end(args);
+ error_printf("\n");
+}
+
+#ifndef _WIN32
+static char *get_username(void)
+{
+ struct passwd *pwd;
+
+ pwd = getpwuid(geteuid ());
+ if (!pwd) {
+ error_report("failed to get current user name");
+ return NULL;
+ }
+ return g_strdup(pwd->pw_name);
+}
+#else
+static char *get_username(void)
+{
+ error_report("on Windows, specify a remote user name in the URI");
+ return NULL;
+}
+#endif
+
+static int parse_uri(BDRVSSHState *s, const char *filename)
+{
+ URI *uri;
+
+ uri = uri_parse(filename);
+ if (!uri)
+ return -EINVAL;
+
+ if (strcmp(uri->scheme, "ssh") != 0) {
+ error_report("URI scheme must be 'ssh'");
+ goto err;
+ }
+
+ if (!uri->server || strcmp(uri->server, "") == 0) {
+ error_report("missing hostname in URI");
+ goto err;
+ }
+
+ if (!uri->path || strcmp(uri->path, "") == 0) {
+ error_report("missing remote path in URI");
+ goto err;
+ }
+
+ /* If user is defined in the URI, use it. Else use local username. */
+ if(uri->user && strcmp(uri->user, "") != 0)
+ s->user = g_strdup(uri->user);
+ else {
+ s->user = get_username();
+ if (!s->user)
+ goto err;
+ }
+
+ /* Construct the hostname:port string for inet_connect. */
+ if(uri->port == 0)
+ uri->port = 22;
+ s->host = g_strdup_printf("%s:%d", uri->server, uri->port);
+
+ s->path = g_strdup(uri->path);
+
+ return 0;
+
+ err:
+ uri_free(uri);
+ return -EINVAL;
+}
+
+static int connect_to_ssh(BDRVSSHState *s)
+{
+ int r, ret;
+ const char *userauthlist;
+ LIBSSH2_AGENT *agent = NULL;
+ struct libssh2_agent_publickey *identity;
+ struct libssh2_agent_publickey *prev_identity = NULL;
+
+ s->session = libssh2_session_init();
+ if (!s->session) {
+ ret = -EINVAL;
+ session_error_report(s, "failed to initialize libssh2 session");
+ goto err;
+ }
+
+ r = libssh2_session_handshake(s->session, s->sock);
+ if (r != 0) {
+ ret = -EINVAL;
+ session_error_report(s, "failed to establish SSH session");
+ goto err;
+ }
+
+#if 0
+ /* Check the remote host's key against known_hosts. */
+ ret = check_host_key (s);
+ if (ret < 0)
+ goto err;
+#endif
+
+ /* Authenticate. */
+ userauthlist = libssh2_userauth_list(s->session, s->user, strlen(s->user));
+ if (strstr(userauthlist, "publickey") == NULL) {
+ ret = -EPERM;
+ error_report("remote server does not support \"publickey\"
authentication");
+ goto err;
+ }
+
+ /* Connect to ssh-agent and try each identity in turn. */
+ agent = libssh2_agent_init(s->session);
+ if (!agent) {
+ ret = -EINVAL;
+ session_error_report(s, "failed to initialize ssh-agent support");
+ goto err;
+ }
+ if (libssh2_agent_connect(agent)) {
+ ret = -ECONNREFUSED;
+ session_error_report(s, "failed to connect to ssh-agent");
+ goto err;
+ }
+ if (libssh2_agent_list_identities(agent)) {
+ ret = -EINVAL;
+ session_error_report(s, "failed requesting identities from ssh-agent");
+ goto err;
+ }
+
+ for(;;) {
+ r = libssh2_agent_get_identity(agent, &identity, prev_identity);
+ if (r == 1) /* end of list */
+ break;
+ if (r < 0) {
+ ret = -EINVAL;
+ session_error_report(s, "failed to obtain identity from
ssh-agent");
+ goto err;
+ }
+ r = libssh2_agent_userauth(agent, s->user, identity);
+ if (r == 0)
+ goto authenticated;
+ /* Failed to authenticate with this identity, try the next one. */
+ prev_identity = identity;
+ }
+
+ ret = -EPERM;
+ error_report("failed to authenticate using publickey authentication "
+ "and the identities held by your ssh-agent");
+ goto err;
+
+ authenticated:
+ libssh2_agent_disconnect(agent);
+ libssh2_agent_free(agent);
+ agent = NULL;
+
+ /* Start SFTP. */
+ s->sftp = libssh2_sftp_init(s->session);
+ if (!s->sftp) {
+ session_error_report(s, "failed to initialize sftp handle");
+ ret = -EINVAL;
+ goto err;
+ }
+
+ s->sftp_handle = libssh2_sftp_open(s->sftp, s->path,
+ LIBSSH2_FXF_READ|LIBSSH2_FXF_WRITE,
+ 0);
+ if (!s->sftp_handle) {
+ session_error_report(s, "failed to open remote file '%s'", s->path);
+ ret = -EINVAL;
+ goto err;
+ }
+
+ r = libssh2_sftp_fstat(s->sftp_handle, &s->attrs);
+ if (r < 0) {
+ sftp_error_report(s, "failed to read file attributes of '%s'",
+ s->path);
+ ret = -EINVAL;
+ goto err;
+ }
+
+ 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;
+
+ if (agent) {
+ libssh2_agent_disconnect(agent);
+ libssh2_agent_free(agent);
+ }
+
+ return ret;
+}
+
+static int ssh_file_open(BlockDriverState *bs, const char *filename,
+ int bdrv_flags)
+{
+ BDRVSSHState *s = bs->opaque;
+ int ret;
+ Error *err = NULL;
+
+ s->sock = -1;
+
+ ret = parse_uri(s, filename);
+ if (ret < 0)
+ goto err;
+
+ /* Open the socket and connect. */
+ s->sock = inet_connect(s->host, &err);
+ if (err != NULL) {
+ ret = -errno;
+ qerror_report_err(err);
+ error_free(err);
+ goto err;
+ }
+
+ /* Start up SSH. */
+ ret = connect_to_ssh(s);
+ if (ret < 0)
+ goto err;
+
+#if 0 /* Enable this when AIO callbacks are implemented. */
+ /* Go non-blocking. */
+ libssh2_session_set_blocking(s->session, 0);
+#endif
+
+ qemu_co_mutex_init(&s->lock);
+
+ return 0;
+
+ err:
+ if (s->sock >= 0)
+ close(s->sock);
+ s->sock = -1;
+
+ g_free(s->path);
+ s->path = NULL;
+ g_free(s->host);
+ s->host = NULL;
+ g_free(s->user);
+ s->user = NULL;
+
+ return ret;
+}
+
+static void ssh_close(BlockDriverState *bs)
+{
+ BDRVSSHState *s = bs->opaque;
+
+ 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);
+
+ g_free(s->path);
+ g_free(s->host);
+ g_free(s->user);
+}
+
+static coroutine_fn int ssh_read(BDRVSSHState *s,
+ int64_t offset, char *buf, size_t size)
+{
+ ssize_t r;
+ size_t got;
+
+ /* According to the docs, this just updates a field in the
+ * sftp_handle structure, so there is no network traffic and it
+ * cannot fail.
+ */
+ libssh2_sftp_seek64(s->sftp_handle, offset);
+
+ /* 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:
+ r = libssh2_sftp_read(s->sftp_handle, buf + got, size - got);
+
+ if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT)
+ goto again;
+ if (r < 0) {
+ sftp_error_report(s, "%s: read failed", s->path);
+ return -EIO;
+ }
+ if (r == 0) {
+ error_report("%s: read failed (EOF)", s->path);
+ return -EIO;
+ }
+
+ got += r;
+ }
+
+ return 0;
+}
+
+static coroutine_fn int ssh_co_read(BlockDriverState *bs,
+ int64_t sector_num,
+ uint8_t *buf, int nb_sectors)
+{
+ BDRVSSHState *s = bs->opaque;
+ int ret;
+
+ qemu_co_mutex_lock(&s->lock);
+ ret = ssh_read(s, sector_num * SECTOR_SIZE, (char *) buf,
+ nb_sectors * SECTOR_SIZE);
+ qemu_co_mutex_unlock(&s->lock);
+
+ return ret;
+}
+
+static int ssh_write(BDRVSSHState *s,
+ int64_t offset, const char *buf, size_t size)
+{
+ ssize_t r;
+ size_t written;
+
+ /* According to the docs, this just updates a field in the
+ * sftp_handle structure, so there is no network traffic and it
+ * cannot fail.
+ */
+ libssh2_sftp_seek64(s->sftp_handle, offset);
+
+ for (written = 0; written < size; ) {
+ again:
+ r = libssh2_sftp_write(s->sftp_handle, buf + written, size - written);
+
+ if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT)
+ goto again;
+ if (r < 0) {
+ sftp_error_report(s, "%s: write failed", s->path);
+ return -EIO;
+ }
+
+ written += r;
+ }
+
+ return 0;
+}
+
+static coroutine_fn int ssh_co_write(BlockDriverState *bs,
+ int64_t sector_num,
+ const uint8_t *buf, int nb_sectors)
+{
+ BDRVSSHState *s = bs->opaque;
+ int ret;
+
+ qemu_co_mutex_lock(&s->lock);
+ ret = ssh_write(s, sector_num * SECTOR_SIZE, (const char *)buf,
+ nb_sectors * SECTOR_SIZE);
+
+ qemu_co_mutex_unlock(&s->lock);
+
+ return ret;
+}
+
+static int64_t ssh_getlength(BlockDriverState *bs)
+{
+ BDRVSSHState *s = bs->opaque;
+ return (int64_t) s->attrs.filesize;
+}
+
+static BlockDriver bdrv_ssh = {
+ .format_name = "ssh",
+ .protocol_name = "ssh",
+ .instance_size = sizeof(BDRVSSHState),
+ .bdrv_file_open = ssh_file_open,
+ .bdrv_close = ssh_close,
+ .bdrv_read = ssh_co_read,
+ .bdrv_write = ssh_co_write,
+ .bdrv_getlength = ssh_getlength,
+#if 0
+ .bdrv_aio_readv = ssh_aio_readv,
+ .bdrv_aio_writev = ssh_aio_writev,
+ .bdrv_aio_flush = ssh_aio_flush,
+#endif
+};
+
+static void bdrv_ssh_init(void)
+{
+ bdrv_register(&bdrv_ssh);
+}
+
+block_init(bdrv_ssh_init);
diff --git a/configure b/configure
index 46a7594..4ea1b39 100755
--- a/configure
+++ b/configure
@@ -229,6 +229,7 @@ virtio_blk_data_plane=""
gtk=""
gtkabi="2.0"
tpm="no"
+libssh2=""
# parse CC options first
for opt do
@@ -908,6 +909,10 @@ for opt do
;;
--enable-tpm) tpm="yes"
;;
+ --disable-libssh2) libssh2="no"
+ ;;
+ --enable-libssh2) libssh2="yes"
+ ;;
*) echo "ERROR: unknown option $opt"; show_help="yes"
;;
esac
@@ -1164,6 +1169,7 @@ echo " --disable-glusterfs disable GlusterFS
backend"
echo " --enable-gcov enable test coverage analysis with gcov"
echo " --gcov=GCOV use specified gcov [$gcov_tool]"
echo " --enable-tpm enable TPM support"
+echo " --enable-libssh2 enable ssh block device support"
echo ""
echo "NOTE: The object files are built at the place where configure is
launched"
exit 1
@@ -2328,6 +2334,42 @@ EOF
fi
##########################################
+# libssh2 probe
+if test "$libssh2" != "no" ; then
+ cat > $TMPC <<EOF
+#include <stdio.h>
+#include <libssh2.h>
+#include <libssh2_sftp.h>
+int main(void) {
+ LIBSSH2_SESSION *session;
+ session = libssh2_session_init ();
+ (void) libssh2_sftp_init (session);
+ return 0;
+}
+EOF
+
+ if $pkg_config libssh2 --modversion >/dev/null 2>&1; then
+ libssh2_cflags=`$pkg_config libssh2 --cflags`
+ libssh2_libs=`$pkg_config libssh2 --libs`
+ else
+ libssh2_cflags=
+ libssh2_libs="-lssh2"
+ fi
+
+ if compile_prog "$libssh2_cflags" "$libssh2_libs" ; then
+ libssh2=yes
+ libs_tools="$libssh2_libs $libs_tools"
+ libs_softmmu="$libssh2_libs $libs_softmmu"
+ QEMU_CFLAGS="$QEMU_CFLAGS $libssh2_cflags"
+ else
+ if test "$libssh2" = "yes" ; then
+ feature_not_found "libssh2"
+ fi
+ libssh2=no
+ fi
+fi
+
+##########################################
# linux-aio probe
if test "$linux_aio" != "no" ; then
@@ -3439,6 +3481,7 @@ echo "virtio-blk-data-plane $virtio_blk_data_plane"
echo "gcov $gcov_tool"
echo "gcov enabled $gcov"
echo "TPM support $tpm"
+echo "libssh2 support $libssh2"
if test "$sdl_too_old" = "yes"; then
echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -3804,6 +3847,10 @@ if test "$glusterfs" = "yes" ; then
echo "CONFIG_GLUSTERFS=y" >> $config_host_mak
fi
+if test "$libssh2" = "yes" ; then
+ echo "CONFIG_LIBSSH2=y" >> $config_host_mak
+fi
+
if test "$virtio_blk_data_plane" = "yes" ; then
echo "CONFIG_VIRTIO_BLK_DATA_PLANE=y" >> $config_host_mak
fi
diff --git a/qemu-doc.texi b/qemu-doc.texi
index af84bef..004b2ff 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -423,6 +423,7 @@ snapshots.
* disk_images_sheepdog:: Sheepdog disk images
* disk_images_iscsi:: iSCSI LUNs
* disk_images_gluster:: GlusterFS disk images
+* disk_images_ssh:: Secure Shell (ssh) disk images
@end menu
@node disk_images_quickstart
@@ -1038,6 +1039,33 @@ qemu-system-x86_64 -drive
file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glu
qemu-system-x86_64 -drive file=gluster+rdma://1.2.3.4:24007/testvol/a.img
@end example
+@node disk_images_ssh
+@subsection Secure Shell (ssh) disk images
+
+You can access disk images located on a remote ssh server
+by using the ssh protocol:
+@example
+qemu-system-x86_64 -drive
file=ssh://[@var{user}@@]@var{server}[:@var{port}]/@var{path}
+@end example
+
+@var{ssh} is the protocol.
+
+@var{user} is the remote user. If not specified, then the local
+username is tried.
+
+@var{server} specifies the remote ssh server. Any ssh server can be
+used, but it must implement the sftp-server protocol. Most Unix/Linux
+systems should work without requiring any extra configuration.
+
+@var{port} is the port number on which sshd is listening. By default
+the standard ssh port (22) is used.
+
+@var{path} is the path to the disk image.
+
+Authentication must currently be done without requiring a password or
+passphrase. Set up ssh-agent with authorized keys, or Kerberos or
+similar.
+
@node pcsys_network
@section Network emulation
--
1.8.1.4
