Re: [libvirt] [PATCH 3/4] security: Introduce method for labeling file descriptors of created files
On 06/27/13 20:51, Daniel P. Berrange wrote:
On Wed, Jun 26, 2013 at 03:01:49PM +0200, Peter Krempa wrote:
> The method labels the file descriptor even if dynamic labeling/relabeling
> is turned off. This is needed for files created by libvirt and then
> passed along to qemu as a FD.
> ---
> src/libvirt_private.syms | 1 +
> src/security/security_dac.c | 9 +++++++++
> src/security/security_driver.h | 4 ++++
> src/security/security_manager.c | 16 ++++++++++++++++
> src/security/security_manager.h | 3 +++
> src/security/security_nop.c | 1 +
> src/security/security_selinux.c | 21 +++++++++++++++++++++
> src/security/security_stack.c | 19 +++++++++++++++++++
> 8 files changed, 74 insertions(+)
>
> diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c
> index 7802dda..5894259 100644
> --- a/src/security/security_selinux.c
> +++ b/src/security/security_selinux.c
> @@ -2446,6 +2446,26 @@
virSecuritySELinuxGetSecurityMountOptions(virSecurityManagerPtr mgr,
> return opts;
> }
>
> +static int
> +virSecuritySELinuxSetCreatedFDLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
> + virDomainDefPtr def,
> + int fd)
> +{
> + virSecurityLabelDefPtr secdef;
> +
> + if ((secdef = virDomainDefGetSecurityLabelDef(def, SECURITY_SELINUX_NAME))) {
> + if (!secdef->imagelabel)
> + secdef->imagelabel = virSecuritySELinuxGenImageLabel(mgr, def);
This is really dubious. None of the methods except for GenSecurityLabel
should be making changes to the secdef state.
There is already an exception: virSecuritySELinuxGetSecurityMountOptions().
> + } else {
> + return -1;
> + }
The style with nested if()s here is not following the pattern used in other
methods here either.
hmmmm ... ok
> +
> + if (secdef->imagelabel == NULL)
> + return 0;
> +
> + return virSecuritySELinuxFSetFilecon(fd, secdef->imagelabel);
> +}
In general I'm not really convinced we should be adding a new method
here, as opposed to making the existing SetImageFDLabel do the right
thing.
I was going to suggest expanding the function prototype with a bool that
would allow to choose whether to label the image always or only if
relabeling is enabled but looking through the code I noticed that
actually every caller would need to have this flag enabled.
There are currently 4 places this method is called:
qemuDumpToFd() - labels a FD of a freshly created file for the memory dump
qemuMigrationToFile() - again a new file FD is labeled, used for
(managed) save and dumping of memory
doTunnelMigrate() - the FD's of a pipe used for extracting data into the
stream are labeled, again this would probably fail with static labeling.
qemuProcessStart() - the migration FD is labelled on process start.
I think it's safe (and necessary) to relabel these even if relabeling is
disabled and thus we can change the function to always label FD's.
Do you agree?
Daniel
Peter