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[libvirt] Re: PATCH: Mark <seclabel> as dynamic generated, or statically pre-defined



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Daniel P. Berrange wrote:
> This patch implements the behaviour I was refering to earlier, whereby
> the domain XML explicitly says whether the security label is a statically
> pre-defined one, or dynamically generated on VM boot by libvirtd
> 
> So when creating a new guest, apps like virt-install have 2 options:
> 
>  - Leave out the <seclabel> tag completely
>     -> If no security driver is active, just works as normal unconfined VM
I want to make sure of terminology.  The VM will be confined, but will
not be separated.  IE the host machine will be protected from the VM,
while other VM's will not be.  svirt is concerned with protecting VM's
from each other.  Normal SELinux protects the Apache server from rogue
VMs.  If we want to have a truly unconfined vm, we need additional
policy.  I would suggest permissive mode or a permissive domain.

semanage permissive -a qemu_t

Would give you this.

>     -> If a security driver is active, a dynamic seclabel is generated
> 
>       <seclabel type='dynamic' model='selinux'>
>         <label>system_u:system_r:qemu_t:s0:c424,c719</label>
>         <imagelabel>system_u:object_r:virt_image_t:s0:c424,c719</imagelabel>
>       </seclabel>
> 
>  - Add an explicit <seclabel> tag with type='static' attribute
>     -> Security driver uses the defined label & imagelabel
> 
>       <seclabel type='static' model='selinux'>
>         <label>system_u:system_r:qemu_t:s0:c25,c100</label>
>         <imagelabel>system_u:system_r:virt_image_t:s0:c25,c100</imagelabel>
>       </seclabel>
> 
>
Not sure imagelabel is required in the second case since, libvirt will
not change the label.

This is the biggest difference between static and dynamic, static will
never run setfilecon, while dynamic runs it at startup and shutdown.

DYNAMIC:
	start
	setfilecon(image, imagelabel)
	setexeccon(label)
	exec()

	Finish
	ChildExit()
	setfilecon(image, DEFAULT_LABEL)
 	Exit()

STATIC:
	start
	setexecon(label)
	exec()

	Finish:
	ChildExit()
	Exit()

> A static seclabel is visible in the XML, at all times, whether the VM is
> active or inactive. 
> 
> A dynamic seclabel is only visible when the VM is running, since it is
> auto-generated at VM boot. If you migrate the VM, or save/restore it,
> the dynamic seclabel will change on each boot. The seclabel isn't visible
> when not running, or if asking for the inactive XML dump
> 
> This patch implements parsing of the 'type' attribute, and makes the
> seclabel generation key off this attribute.
> 
> It also adds the 'imagelabel' XML element, since that was being used
> internally, but was not including in the XML output, or parsing
> routines, making it impossible to specify a pre-defined image label
> or see the dyanmic one
> 
>  domain_conf.c      |   65 +++++++++++++++++++++++++++++++++++++++++++----------
>  domain_conf.h      |    9 +++++++
>  qemu_driver.c      |   13 ++++++++--
>  security_selinux.c |    1 
>  4 files changed, 73 insertions(+), 15 deletions(-)
> 
> 
> Daniel
> 
> Index: src/domain_conf.c
> ===================================================================
> RCS file: /data/cvs/libvirt/src/domain_conf.c,v
> retrieving revision 1.70
> diff -u -p -r1.70 domain_conf.c
> --- src/domain_conf.c	3 Mar 2009 09:44:42 -0000	1.70
> +++ src/domain_conf.c	3 Mar 2009 15:36:02 -0000
> @@ -168,6 +168,10 @@ VIR_ENUM_IMPL(virDomainState, VIR_DOMAIN
>                "shutoff",
>                "crashed")
>  
> +VIR_ENUM_IMPL(virDomainSeclabel, VIR_DOMAIN_SECLABEL_LAST,
> +              "dynamic",
> +              "static")
> +
>  #define virDomainReportError(conn, code, fmt...)                           \
>          virReportErrorHelper(conn, VIR_FROM_DOMAIN, code, __FILE__,        \
>                                 __FUNCTION__, __LINE__, fmt)
> @@ -1847,24 +1851,46 @@ static int virDomainLifecycleParseXML(vi
>  static int
>  virSecurityLabelDefParseXML(virConnectPtr conn,
>                              const virDomainDefPtr def,
> -                            xmlXPathContextPtr ctxt)
> +                            xmlXPathContextPtr ctxt,
> +                            int flags)
>  {
>      char *p;
>  
>      if (virXPathNode(conn, "./seclabel", ctxt) == NULL)
>          return 0;
>  
> -    p = virXPathStringLimit(conn, "string(./seclabel/label[1])",
> +    p = virXPathStringLimit(conn, "string(./seclabel/@type)",
>                              VIR_SECURITY_LABEL_BUFLEN-1, ctxt);
>      if (p == NULL)
>          goto error;
> -    def->seclabel.label = p;
> -
> -    p = virXPathStringLimit(conn, "string(./seclabel/@model)",
> -                            VIR_SECURITY_MODEL_BUFLEN-1, ctxt);
> -    if (p == NULL)
> +    if ((def->seclabel.type = virDomainSeclabelTypeFromString(p)) < 0)
>          goto error;
> -    def->seclabel.model = p;
> +    VIR_FREE(p);
> +
> +    /* Only parse details, if using static labels, or
> +     * if the 'live' VM XML is requested
> +     */
> +    if (def->seclabel.type == VIR_DOMAIN_SECLABEL_STATIC ||
> +        !(flags & VIR_DOMAIN_XML_INACTIVE)) {
> +        p = virXPathStringLimit(conn, "string(./seclabel/@model)",
> +                                VIR_SECURITY_MODEL_BUFLEN-1, ctxt);
> +        if (p == NULL)
> +            goto error;
> +        def->seclabel.model = p;
> +
> +        p = virXPathStringLimit(conn, "string(./seclabel/label[1])",
> +                                VIR_SECURITY_LABEL_BUFLEN-1, ctxt);
> +        if (p == NULL)
> +            goto error;
> +        def->seclabel.label = p;
> +
> +        p = virXPathStringLimit(conn, "string(./seclabel/imagelabel[1])",
> +                                VIR_SECURITY_LABEL_BUFLEN-1, ctxt);
> +        if (p == NULL)
> +            goto error;
> +        def->seclabel.imagelabel = p;
> +
> +    }
>  
>      return 0;
>  
> @@ -2458,7 +2484,7 @@ static virDomainDefPtr virDomainDefParse
>      VIR_FREE(nodes);
>  
>      /* analysis of security label */
> -    if (virSecurityLabelDefParseXML(conn, def, ctxt) == -1)
> +    if (virSecurityLabelDefParseXML(conn, def, ctxt, flags) == -1)
>          goto error;
>  
>      return def;
> @@ -3480,9 +3506,24 @@ char *virDomainDefFormat(virConnectPtr c
>      virBufferAddLit(&buf, "  </devices>\n");
>  
>      if (def->seclabel.model) {
> -        virBufferEscapeString(&buf, "  <seclabel model='%s'>\n", def->seclabel.model);
> -        virBufferEscapeString(&buf, "    <label>%s</label>\n", def->seclabel.label);
> -        virBufferAddLit(&buf, "  </seclabel>\n");
> +        const char *sectype = virDomainSeclabelTypeToString(def->seclabel.type);
> +        if (!sectype)
> +            goto cleanup;
> +        if (!def->seclabel.label ||
> +            (def->seclabel.type == VIR_DOMAIN_SECLABEL_DYNAMIC &&
> +             (flags & VIR_DOMAIN_XML_INACTIVE))) {
> +            virBufferVSprintf(&buf, "  <seclabel type='%s' model='%s'/>\n",
> +                              sectype, def->seclabel.model);
> +        } else {
> +            virBufferVSprintf(&buf, "  <seclabel type='%s' model='%s'>\n",
> +                                  sectype, def->seclabel.model);
> +            virBufferEscapeString(&buf, "    <label>%s</label>\n",
> +                                  def->seclabel.label);
> +            if (def->seclabel.imagelabel)
> +                virBufferEscapeString(&buf, "    <imagelabel>%s</imagelabel>\n",
> +                                      def->seclabel.imagelabel);
> +            virBufferAddLit(&buf, "  </seclabel>\n");
> +        }
>      }
>  
>      virBufferAddLit(&buf, "</domain>\n");
> Index: src/domain_conf.h
> ===================================================================
> RCS file: /data/cvs/libvirt/src/domain_conf.h,v
> retrieving revision 1.39
> diff -u -p -r1.39 domain_conf.h
> --- src/domain_conf.h	3 Mar 2009 09:44:42 -0000	1.39
> +++ src/domain_conf.h	3 Mar 2009 15:36:02 -0000
> @@ -410,6 +410,13 @@ struct _virDomainOSDef {
>      char *bootloaderArgs;
>  };
>  
> +enum virDomainSeclabelType {
> +    VIR_DOMAIN_SECLABEL_DYNAMIC,
> +    VIR_DOMAIN_SECLABEL_STATIC,
> +
> +    VIR_DOMAIN_SECLABEL_LAST,
> +};
> +
>  /* Security configuration for domain */
>  typedef struct _virSecurityLabelDef virSecurityLabelDef;
>  typedef virSecurityLabelDef *virSecurityLabelDefPtr;
> @@ -417,6 +424,7 @@ struct _virSecurityLabelDef {
>      char *model;        /* name of security model */
>      char *label;        /* security label string */
>      char *imagelabel;   /* security image label string */
> +    int type;
>  };
>  
>  #define VIR_DOMAIN_CPUMASK_LEN 1024
> @@ -650,5 +658,6 @@ VIR_ENUM_DECL(virDomainInputBus)
>  VIR_ENUM_DECL(virDomainGraphics)
>  /* from libvirt.h */
>  VIR_ENUM_DECL(virDomainState)
> +VIR_ENUM_DECL(virDomainSeclabel)
>  
>  #endif /* __DOMAIN_CONF_H */
> Index: src/qemu_driver.c
> ===================================================================
> RCS file: /data/cvs/libvirt/src/qemu_driver.c,v
> retrieving revision 1.213
> diff -u -p -r1.213 qemu_driver.c
> --- src/qemu_driver.c	3 Mar 2009 15:18:24 -0000	1.213
> +++ src/qemu_driver.c	3 Mar 2009 15:36:02 -0000
> @@ -1314,9 +1314,9 @@ static int qemudStartVMDaemon(virConnect
>      hookData.vm = vm;
>      hookData.driver = driver;
>  
> -   /* If you are using a SecurityDriver and there was no security label in
> -      database, then generate a security label for isolation */
> -    if (vm->def->seclabel.label == NULL &&
> +   /* If you are using a SecurityDriver with dynamic labelling, 
> +      then generate a security label for isolation */
> +    if (vm->def->seclabel.type == VIR_DOMAIN_SECLABEL_DYNAMIC &&
>          driver->securityDriver &&
>          driver->securityDriver->domainGenSecurityLabel &&
>          driver->securityDriver->domainGenSecurityLabel(conn, vm) < 0)
> @@ -1525,6 +1525,13 @@ static void qemudShutdownVMDaemon(virCon
>      if (driver->securityDriver)
>          driver->securityDriver->domainRestoreSecurityLabel(conn, vm);
>  
> +    /* Clear out dynamically assigned labels */
> +    if (vm->def->seclabel.type == VIR_DOMAIN_SECLABEL_DYNAMIC) {
> +        VIR_FREE(vm->def->seclabel.model);
> +        VIR_FREE(vm->def->seclabel.label);
> +        VIR_FREE(vm->def->seclabel.imagelabel);
> +    }
> +
>      if (qemudRemoveDomainStatus(conn, driver, vm) < 0) {
>          VIR_WARN(_("Failed to remove domain status for %s"),
>                   vm->def->name);
> Index: src/security_selinux.c
> ===================================================================
> RCS file: /data/cvs/libvirt/src/security_selinux.c,v
> retrieving revision 1.2
> diff -u -p -r1.2 security_selinux.c
> --- src/security_selinux.c	3 Mar 2009 15:18:24 -0000	1.2
> +++ src/security_selinux.c	3 Mar 2009 15:36:02 -0000
> @@ -161,6 +161,7 @@ SELinuxGenSecurityLabel(virConnectPtr co
>      char *scontext = NULL;
>      int c1 = 0;
>      int c2 = 0;
> +
>      if ( ( vm->def->seclabel.label ) ||
>           ( vm->def->seclabel.model ) ||
>           ( vm->def->seclabel.imagelabel )) {
> 
> 

Patch looks good.
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