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hw/9pfs: man page for proxy helper

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Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This commit is contained in:
M. Mohan Kumar 2011-12-14 13:58:47 +05:30 committed by Aneesh Kumar K.V
parent f67e3ffd34
commit a2d8f1beb1
2 changed files with 70 additions and 1 deletions
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12
Makefile
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@ -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
@ -289,7 +290,10 @@ 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"
@ -373,6 +377,12 @@ 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 && \

59
fsdev/virtfs-proxy-helper.texi Normal file
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@ -0,0 +1,59 @@
@example
@c man begin SYNOPSIS
usage: virtfs-proxy-helper options
@c man end
@end example
@c man begin DESCRIPTION
@table @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.
@end table
@c man end
@c man begin OPTIONS
The following options are supported:
@table @option
@item -h
@findex -h
Display help and exit
@item -p|--path path
Path to export for proxy filesystem driver
@item -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
@item -n|--nodaemon
Run as a normal program. By default program will run in daemon mode
@end table
@c man end
@setfilename virtfs-proxy-helper
@settitle QEMU 9p virtfs proxy filesystem helper
@c man begin AUTHOR
M. Mohan Kumar
@c man end