| Message ID | 20220803151741.7826-1-dpsmith@apertussolutions.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v11] xsm: refactor flask sid alloc and domain check | expand |
On 03.08.2022 17:17, Daniel P. Smith wrote: > Changes in v11: > - put back dom0_created variable in flask_domain_create() to ensure the > enforcement that dom0_t is a singleton label Stale patch or bad rev log? > @@ -548,22 +556,19 @@ static int cf_check flask_domain_create(struct domain *d, uint32_t ssidref) > { > int rc; > struct domain_security_struct *dsec = d->ssid; > - static int dom0_created = 0; The variable is going away here, and it is not re-appearing elsewhere. Jan > - if ( is_idle_domain(current->domain) && !dom0_created ) > - { > - dsec->sid = SECINITSID_DOM0; > - dom0_created = 1; > - } > - else > - { > - rc = avc_current_has_perm(ssidref, SECCLASS_DOMAIN, > - DOMAIN__CREATE, NULL); > - if ( rc ) > - return rc; > + /* > + * If the null label is passed, then use the label from security context > + * allocation. > + */ > + if ( ssidref == 0 ) > + ssidref = dsec->sid; > > - dsec->sid = ssidref; > - } > + rc = avc_current_has_perm(ssidref, SECCLASS_DOMAIN, DOMAIN__CREATE, NULL); > + if ( rc ) > + return rc; > + > + dsec->sid = ssidref; > dsec->self_sid = dsec->sid; > > rc = security_transition_sid(dsec->sid, dsec->sid, SECCLASS_DOMAIN,
On 8/3/22 11:26, Jan Beulich wrote: > On 03.08.2022 17:17, Daniel P. Smith wrote: >> Changes in v11: >> - put back dom0_created variable in flask_domain_create() to ensure the >> enforcement that dom0_t is a singleton label > > Stale patch or bad rev log? Nope, having a bad day. Staged the change but didn't amend commit it before my usual sequence of test and cut patch. My apologies. >> @@ -548,22 +556,19 @@ static int cf_check flask_domain_create(struct domain *d, uint32_t ssidref) >> { >> int rc; >> struct domain_security_struct *dsec = d->ssid; >> - static int dom0_created = 0; > > The variable is going away here, and it is not re-appearing elsewhere. > > Jan > >> - if ( is_idle_domain(current->domain) && !dom0_created ) >> - { >> - dsec->sid = SECINITSID_DOM0; >> - dom0_created = 1; >> - } >> - else >> - { >> - rc = avc_current_has_perm(ssidref, SECCLASS_DOMAIN, >> - DOMAIN__CREATE, NULL); >> - if ( rc ) >> - return rc; >> + /* >> + * If the null label is passed, then use the label from security context >> + * allocation. >> + */ >> + if ( ssidref == 0 ) >> + ssidref = dsec->sid; >> >> - dsec->sid = ssidref; >> - } >> + rc = avc_current_has_perm(ssidref, SECCLASS_DOMAIN, DOMAIN__CREATE, NULL); >> + if ( rc ) >> + return rc; >> + >> + dsec->sid = ssidref; >> dsec->self_sid = dsec->sid; >> >> rc = security_transition_sid(dsec->sid, dsec->sid, SECCLASS_DOMAIN, >
diff --git a/tools/flask/policy/modules/dom0.te b/tools/flask/policy/modules/dom0.te index 0a63ce15b6..f710ff9941 100644 --- a/tools/flask/policy/modules/dom0.te +++ b/tools/flask/policy/modules/dom0.te @@ -75,3 +75,6 @@ admin_device(dom0_t, ioport_t) admin_device(dom0_t, iomem_t) domain_comms(dom0_t, dom0_t) + +# Allow the hypervisor to build domains of type dom0_t +xen_build_domain(dom0_t) diff --git a/tools/flask/policy/modules/domU.te b/tools/flask/policy/modules/domU.te index b77df29d56..3f269018f9 100644 --- a/tools/flask/policy/modules/domU.te +++ b/tools/flask/policy/modules/domU.te @@ -13,6 +13,9 @@ domain_comms(domU_t, domU_t) migrate_domain_out(dom0_t, domU_t) domain_self_comms(domU_t) +# Allow the hypervisor to build domains of type domU_t +xen_build_domain(domU_t) + # Device model for domU_t. You can define distinct types for device models for # domains of other types, or add more make_device_model lines for this type. declare_domain(dm_dom_t) diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c index 8c9cd0f297..cb81e62c52 100644 --- a/xen/xsm/flask/hooks.c +++ b/xen/xsm/flask/hooks.c @@ -182,7 +182,15 @@ static int cf_check flask_domain_alloc_security(struct domain *d) dsec->sid = SECINITSID_DOMIO; break; default: - dsec->sid = SECINITSID_UNLABELED; + if ( domain_sid(current->domain) == SECINITSID_XENBOOT ) + { + if ( d->is_privileged ) + dsec->sid = SECINITSID_DOM0; + else + dsec->sid = SECINITSID_DOMU; + } + else + dsec->sid = SECINITSID_UNLABELED; } dsec->self_sid = dsec->sid; @@ -548,22 +556,19 @@ static int cf_check flask_domain_create(struct domain *d, uint32_t ssidref) { int rc; struct domain_security_struct *dsec = d->ssid; - static int dom0_created = 0; - if ( is_idle_domain(current->domain) && !dom0_created ) - { - dsec->sid = SECINITSID_DOM0; - dom0_created = 1; - } - else - { - rc = avc_current_has_perm(ssidref, SECCLASS_DOMAIN, - DOMAIN__CREATE, NULL); - if ( rc ) - return rc; + /* + * If the null label is passed, then use the label from security context + * allocation. + */ + if ( ssidref == 0 ) + ssidref = dsec->sid; - dsec->sid = ssidref; - } + rc = avc_current_has_perm(ssidref, SECCLASS_DOMAIN, DOMAIN__CREATE, NULL); + if ( rc ) + return rc; + + dsec->sid = ssidref; dsec->self_sid = dsec->sid; rc = security_transition_sid(dsec->sid, dsec->sid, SECCLASS_DOMAIN,
The function flask_domain_alloc_security() allocates the security context and assigns an initial SID for the domain under construction. When it came to SID assignment of the initial domain, flask_domain_alloc_security() would assign unlabeled_t. Then in flask_domain_create() it would be switched to dom0_t. This logic worked under the assumption that the first domain constructed would be the hypervisor constructing dom0 and all other domains would be constructed by a toolstack, which would provide a SID. The introduction of dom0less and subsequently hyperlaunch violates this assumption, as non-privileged domain may be constructed before the initial domain or no initial domain may be constructed at all. It is not possible currently for dom0less to express domain labels in the domain configuration, as such the FLASK policy must employ a sensible initial SID assignment that can differentiate between hypervisor and toolstack domain construction. With the introduction of xenboot_t it is now possible to distinguish when the hypervisor is in the boot state, and thus any domain construction happening at this time is being initiated by the hypervisor. This commit addresses the above situation by using a check to confirm if the hypervisor is under the xenboot_t context in flask_domain_alloc_security(). When that is the case, it will inspect the domain's is_privileged field to determine whether an initial label of dom0_t or domU_t should be set for the domain. The logic for flask_domain_create() was changed to allow the incoming SID to override the initial label. The base policy was adjusted to allow the idle domain under the xenboot_t context the ability to construct domains of both types, dom0_t and domu_t. Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com> --- Split out from series "Adds starting the idle domain privileged", earlier patches from series have been committed. Changes in v11: - put back dom0_created variable in flask_domain_create() to ensure the enforcement that dom0_t is a singleton label Changes in v10: - rewrote commit message - fixed typos - reworked logic in flask_domain_create() to be simpler and not result in changing the domain security struct before the access check fails tools/flask/policy/modules/dom0.te | 3 +++ tools/flask/policy/modules/domU.te | 3 +++ xen/xsm/flask/hooks.c | 35 +++++++++++++++++------------- 3 files changed, 26 insertions(+), 15 deletions(-)