[Qemu-devel] [PATCH V4 12/13] hw/9pfs: man page for proxy helper

[M. Mohan Kumar]

From: "M. Mohan Kumar" <address@hidden>

Signed-off-by: M. Mohan Kumar <address@hidden>
---
 Makefile                       |   12 +++++++-
 fsdev/virtfs-proxy-helper.texi |   59 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 1 deletions(-)
 create mode 100644 fsdev/virtfs-proxy-helper.texi

diff --git a/Makefile b/Makefile
index 0acad52..f5b3524 100644
--- a/Makefile
+++ b/Makefile
@@ -38,6 +38,7 @@ LIBS+=-lz $(LIBS_TOOLS)
 
 ifdef BUILD_DOCS
 DOCS=qemu-doc.html qemu-tech.html qemu.1 qemu-img.1 qemu-nbd.8 
QMP/qmp-commands.txt
+DOCS+=fsdev/virtfs-proxy-helper.1
 else
 DOCS=
 endif
@@ -283,7 +284,10 @@ ifdef CONFIG_POSIX
        $(INSTALL_DIR) "$(DESTDIR)$(mandir)/man8"
        $(INSTALL_DATA) qemu-nbd.8 "$(DESTDIR)$(mandir)/man8"
 endif
-
+ifdef CONFIG_VIRTFS
+       $(INSTALL_DIR) "$(DESTDIR)$(mandir)/man1"
+       $(INSTALL_DATA) fsdev/virtfs-proxy-helper.1 "$(DESTDIR)$(mandir)/man1"
+endif
 install-sysconfig:
        $(INSTALL_DIR) "$(DESTDIR)$(sysconfdir)/qemu"
        $(INSTALL_DATA) $(SRC_PATH)/sysconfigs/target/target-x86_64.conf 
"$(DESTDIR)$(sysconfdir)/qemu"
@@ -367,6 +371,12 @@ qemu-img.1: qemu-img.texi qemu-img-cmds.texi
          pod2man --section=1 --center=" " --release=" " qemu-img.pod > $@, \
          "  GEN   $@")
 
+fsdev/virtfs-proxy-helper.1: fsdev/virtfs-proxy-helper.texi
+       $(call quiet-command, \
+         perl -Ww -- $(SRC_PATH)/scripts/texi2pod.pl $< 
fsdev/virtfs-proxy-helper.pod && \
+         pod2man --section=1 --center=" " --release=" " 
fsdev/virtfs-proxy-helper.pod > $@, \
+         "  GEN   $@")
+
 qemu-nbd.8: qemu-nbd.texi
        $(call quiet-command, \
          perl -Ww -- $(SRC_PATH)/scripts/texi2pod.pl $< qemu-nbd.pod && \
diff --git a/fsdev/virtfs-proxy-helper.texi b/fsdev/virtfs-proxy-helper.texi
new file mode 100644
index 0000000..3816382
--- /dev/null
+++ b/fsdev/virtfs-proxy-helper.texi
@@ -0,0 +1,59 @@
address@hidden
address@hidden man begin SYNOPSIS
+usage: virtfs-proxy-helper options
address@hidden man end
address@hidden example
+
address@hidden man begin DESCRIPTION
address@hidden @description
+Pass-through security model in QEMU 9p server needs root privilege to do
+few file operations (like chown, chmod to any mode/uid:gid).  There are two
+issues in pass-through security model
+
+1) TOCTTOU vulnerability: Following symbolic links in the server could
+provide access to files beyond 9p export path.
+
+2) Running QEMU with root privilege could be a security issue.
+
+To overcome above issues, following approach is used: A new filesytem
+type 'proxy' is introduced. Proxy FS uses chroot + socket combination
+for securing the vulnerability known with following symbolic links.
+Intention of adding a new filesystem type is to allow qemu to run
+in non-root mode, but doing privileged operations using socket IO.
+
+Proxy helper(a stand alone binary part of qemu) is invoked with
+root privileges. Proxy helper chroots into 9p export path and creates
+a socket pair or a named socket based on the command line parameter.
+Qemu and proxy helper communicate using this socket. QEMU proxy fs
+driver sends filesystem request to proxy helper and receives the
+response from it.
+
+Proxy helper is designed so that it can drop the root privilege with
+retaining capbilities needed for doing filesystem operations only.
+
address@hidden table
address@hidden man end
+
address@hidden man begin OPTIONS
+The following options are supported:
address@hidden @option
address@hidden -h
address@hidden -h
+Display help and exit
address@hidden -p|--path path
+Path to export for proxy filesystem driver
address@hidden -f|--fd socket-id
+Use given file descriptor as socket descriptor for communicating with
+qemu proxy fs drier. Usually a helper like libvirt will create
+socketpair and pass one of the fds as parameter to -f|--fd
address@hidden -n|--nodaemon
+Run as a normal program. By default program will run in daemon mode
address@hidden table
address@hidden man end
+
address@hidden virtfs-proxy-helper
address@hidden QEMU 9p virtfs proxy filesystem helper
+
address@hidden man begin AUTHOR
+M. Mohan Kumar
address@hidden man end
-- 
1.7.6