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api: require write permission for guest agent interaction

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I noticed that we allow virDomainGetVcpusFlags even for read-only
connections, but that with a flag, it can require guest agent
interaction.  It is feasible that a malicious guest could
intentionally abuse the replies it sends over the guest agent
connection to possibly trigger a bug in libvirt's JSON parser,
or withhold an answer so as to prevent the use of the agent
in a later command such as a shutdown request.  Although we
don't know of any such exploits now (and therefore don't mind
posting this patch publicly without trying to get a CVE assigned),
it is better to err on the side of caution and explicitly require
full access to any domain where the API requires guest interaction
to operate correctly.

I audited all commands that are marked as conditionally using a
guest agent.  Note that at least virDomainFSTrim is documented
as needing a guest agent, but that such use is unconditional
depending on the hypervisor (so the existing domain:fs_trim ACL
should be sufficient there, rather than also requirng domain:write).
But when designing future APIs, such as the plans for obtaining
a domain's IP addresses, we should copy the approach of this patch
in making interaction with the guest be specified via a flag, and
use that flag to also require stricter access checks.

* src/libvirt.c (virDomainGetVcpusFlags): Forbid guest interaction
on read-only connection.
(virDomainShutdownFlags, virDomainReboot): Improve docs on agent
interaction.
* src/remote/remote_protocol.x
(REMOTE_PROC_DOMAIN_SNAPSHOT_CREATE_XML)
(REMOTE_PROC_DOMAIN_SET_VCPUS_FLAGS)
(REMOTE_PROC_DOMAIN_GET_VCPUS_FLAGS, REMOTE_PROC_DOMAIN_REBOOT)
(REMOTE_PROC_DOMAIN_SHUTDOWN_FLAGS): Require domain:write for any
conditional use of a guest agent.
* src/xen/xen_driver.c: Fix clients.
* src/libxl/libxl_driver.c: Likewise.
* src/uml/uml_driver.c: Likewise.
* src/qemu/qemu_driver.c: Likewise.
* src/lxc/lxc_driver.c: Likewise.

Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eric Blake 2014-01-21 10:37:29 -07:00
parent bb85da2cb1
commit 7f2d27d1e3
7 changed files with 27 additions and 16 deletions
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12
src/libvirt.c
View File

@ -3134,6 +3134,9 @@ error:
* in which the hypervisor tries each shutdown method is undefined,
* and a hypervisor is not required to support all methods.
*
* To use guest agent (VIR_DOMAIN_SHUTDOWN_GUEST_AGENT) the domain XML
* must have <channel> configured.
*
* Returns 0 in case of success and -1 in case of failure.
*/
int
@ -3180,7 +3183,7 @@ error:
*
* If @flags is set to zero, then the hypervisor will choose the
* method of shutdown it considers best. To have greater control
* pass one or more of the virDomainShutdownFlagValues. The order
* pass one or more of the virDomainRebootFlagValues. The order
* in which the hypervisor tries each shutdown method is undefined,
* and a hypervisor is not required to support all methods.
*
@ -9347,7 +9350,7 @@ error:
* current virtual CPU count.
*
* If @flags includes VIR_DOMAIN_VCPU_GUEST, then the state of the processors
* is modified in the guest instead of the hypervisor. This flag is only usable
* is queried in the guest instead of the hypervisor. This flag is only usable
* on live domains. Guest agent may be needed for this flag to be available.
*
* Returns the number of vCPUs in case of success, -1 in case of failure.
@ -9362,6 +9365,10 @@ virDomainGetVcpusFlags(virDomainPtr domain, unsigned int flags)
virResetLastError();
virCheckDomainReturn(domain, -1);
conn = domain->conn;
if (flags & VIR_DOMAIN_VCPU_GUEST)
virCheckReadOnlyGoto(conn->flags, error);
/* At most one of these two flags should be set. */
if ((flags & VIR_DOMAIN_AFFECT_LIVE) &&
@ -9372,7 +9379,6 @@ virDomainGetVcpusFlags(virDomainPtr domain, unsigned int flags)
__FUNCTION__);
goto error;
}
conn = domain->conn;
if (conn->driver->domainGetVcpusFlags) {
int ret;

6
src/libxl/libxl_driver.c
View File

@ -1409,7 +1409,7 @@ libxlDomainShutdownFlags(virDomainPtr dom, unsigned int flags)
if (!(vm = libxlDomObjFromDomain(dom)))
goto cleanup;
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def) < 0)
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
if (!virDomainObjIsActive(vm)) {
@ -1456,7 +1456,7 @@ libxlDomainReboot(virDomainPtr dom, unsigned int flags)
if (!(vm = libxlDomObjFromDomain(dom)))
goto cleanup;
if (virDomainRebootEnsureACL(dom->conn, vm->def) < 0)
if (virDomainRebootEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
if (!virDomainObjIsActive(vm)) {
@ -2316,7 +2316,7 @@ libxlDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
if (!(vm = libxlDomObjFromDomain(dom)))
goto cleanup;
if (virDomainGetVcpusFlagsEnsureACL(dom->conn, vm->def) < 0)
if (virDomainGetVcpusFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
active = virDomainObjIsActive(vm);

4
src/lxc/lxc_driver.c
View File

@ -3335,7 +3335,7 @@ lxcDomainShutdownFlags(virDomainPtr dom,
priv = vm->privateData;
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def) < 0)
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
if (!virDomainObjIsActive(vm)) {
@ -3415,7 +3415,7 @@ lxcDomainReboot(virDomainPtr dom,
priv = vm->privateData;
if (virDomainRebootEnsureACL(dom->conn, vm->def) < 0)
if (virDomainRebootEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
if (!virDomainObjIsActive(vm)) {

8
src/qemu/qemu_driver.c
View File

@ -1835,7 +1835,7 @@ static int qemuDomainShutdownFlags(virDomainPtr dom, unsigned int flags) {
if (agentRequested || (!flags && priv->agent))
useAgent = true;
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def) < 0)
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
if (priv->agentError) {
@ -1936,7 +1936,7 @@ qemuDomainReboot(virDomainPtr dom, unsigned int flags)
priv = vm->privateData;
if (virDomainRebootEnsureACL(dom->conn, vm->def) < 0)
if (virDomainRebootEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
if ((flags & VIR_DOMAIN_REBOOT_GUEST_AGENT) ||
@ -4898,7 +4898,7 @@ qemuDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
priv = vm->privateData;
if (virDomainGetVcpusFlagsEnsureACL(dom->conn, vm->def) < 0)
if (virDomainGetVcpusFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
if (!(caps = virQEMUDriverGetCapabilities(driver, false)))
@ -13090,7 +13090,7 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
cfg = virQEMUDriverGetConfig(driver);
if (virDomainSnapshotCreateXMLEnsureACL(domain->conn, vm->def) < 0)
if (virDomainSnapshotCreateXMLEnsureACL(domain->conn, vm->def, flags) < 0)
goto cleanup;
if (!(caps = virQEMUDriverGetCapabilities(driver, false)))

5
src/remote/remote_protocol.x
View File

@ -3105,6 +3105,7 @@ enum remote_procedure {
/**
* @generate: both
* @acl: domain:init_control
* @acl: domain:write:VIR_DOMAIN_REBOOT_GUEST_AGENT
*/
REMOTE_PROC_DOMAIN_REBOOT = 27,
@ -4198,6 +4199,7 @@ enum remote_procedure {
/**
* @generate: both
* @acl: domain:snapshot
* @acl: domain:write:VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE
*/
REMOTE_PROC_DOMAIN_SNAPSHOT_CREATE_XML = 185,
@ -4290,12 +4292,14 @@ enum remote_procedure {
* @acl: domain:write
* @acl: domain:save:!VIR_DOMAIN_AFFECT_CONFIG|VIR_DOMAIN_AFFECT_LIVE
* @acl: domain:save:VIR_DOMAIN_AFFECT_CONFIG
* @acl: domain:write:VIR_DOMAIN_VCPU_GUEST
*/
REMOTE_PROC_DOMAIN_SET_VCPUS_FLAGS = 199,
/**
* @generate: both
* @acl: domain:read
* @acl: domain:write:VIR_DOMAIN_VCPU_GUEST
*/
REMOTE_PROC_DOMAIN_GET_VCPUS_FLAGS = 200,
@ -4682,6 +4686,7 @@ enum remote_procedure {
/**
* @generate: both
* @acl: domain:init_control
* @acl: domain:write:VIR_DOMAIN_SHUTDOWN_GUEST_AGENT
*/
REMOTE_PROC_DOMAIN_SHUTDOWN_FLAGS = 258,

2
src/uml/uml_driver.c
View File

@ -1635,7 +1635,7 @@ static int umlDomainShutdownFlags(virDomainPtr dom,
goto cleanup;
}
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def) < 0)
if (virDomainShutdownFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
goto cleanup;
#if 0

6
src/xen/xen_driver.c
View File

@ -952,7 +952,7 @@ xenUnifiedDomainShutdownFlags(virDomainPtr dom,
if (!(def = xenGetDomainDefForDom(dom)))
goto cleanup;
if (virDomainShutdownFlagsEnsureACL(dom->conn, def) < 0)
if (virDomainShutdownFlagsEnsureACL(dom->conn, def, flags) < 0)
goto cleanup;
ret = xenDaemonDomainShutdown(dom->conn, def);
@ -979,7 +979,7 @@ xenUnifiedDomainReboot(virDomainPtr dom, unsigned int flags)
if (!(def = xenGetDomainDefForDom(dom)))
goto cleanup;
if (virDomainRebootEnsureACL(dom->conn, def) < 0)
if (virDomainRebootEnsureACL(dom->conn, def, flags) < 0)
goto cleanup;
ret = xenDaemonDomainReboot(dom->conn, def);
@ -1526,7 +1526,7 @@ xenUnifiedDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
if (!(def = xenGetDomainDefForDom(dom)))
goto cleanup;
if (virDomainGetVcpusFlagsEnsureACL(dom->conn, def) < 0)
if (virDomainGetVcpusFlagsEnsureACL(dom->conn, def, flags) < 0)
goto cleanup;
ret = xenUnifiedDomainGetVcpusFlagsInternal(dom, def, flags);