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Re: [libvirt] [PATCH] Added new attribute accessmode to filesystem element



On 10/14/2010 04:38 PM, Daniel P. Berrange wrote:
On Thu, Oct 14, 2010 at 04:24:45PM +0530, Harsh Prateek Bora wrote:
This patch introduces new attribute to filesystem element
to support customizable access mode for mount type.
Valid accessmode are: passthrough, mapped and squash.

Usage:
	<filesystem type='mount' accessmode='passthrough'>
	<source dir='/export/to/guest'/>
	<target dir='mount_tag'/>
	</filesystem>

Here is the detailed explanation on these access modes:

Access mode: mapped
--------------------

Fileserver intercepts and maps all the file object create requests.
Files on the fileserver will be created with Fileserver's user credentials
and the
client-user's credentials are stored in extended attributes.
During getattr() server extracts the client-user's credentials from extended
attributes and sends to the client.

This adds a great deal of security in the cloud environments where the
guest's(client) user space is kept completely isolated from host's user
space.


Access mode : passthrough
--------------------------

In this security model, Fileserver passes down all requests to the
underlying filesystem. File system objects on the fileserver will be created
with client-user's credentials. This is done by setting setuid()/setgid()
during creation or chmod/chown after file creation. At the end of create
protocol
request, files on the fileserver will be owned by cleint-user's uid/gid.
This model mimic's current NFSv3 level of security.

Access mode: squash
--------------------

In 'squash' mode, the (filesystem) server attempts to preserve user/group
ownership from guest, however:
- If the server is running as root this mode is equivalent to passthrough.
- If the server is running as non-root, all files just have uid/gid matching
   the server process.


Note: This patch is based on Daniel's patch to support 9pfs.
It shall be applied after applying Daniel's patch to support 9pfs.

Signed-off-by: Harsh Prateek Bora<harsh linux vnet ibm com>
---
  docs/schemas/domain.rng |    7 +++++++
  src/conf/domain_conf.c  |   30 ++++++++++++++++++++++++++++--
  src/conf/domain_conf.h  |   11 +++++++++++
  src/qemu/qemu_conf.c    |   10 ++++++++--
  4 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/docs/schemas/domain.rng b/docs/schemas/domain.rng
index ccb8cf3..c0e5149 100644
--- a/docs/schemas/domain.rng
+++ b/docs/schemas/domain.rng
@@ -761,6 +761,13 @@
        </choice>
        <optional>
          <ref name="address"/>
+<attribute name="accessmode">
+<choice>
+<value>passthrough</value>
+<value>mapped</value>
+<value>squash</value>
+</choice>
+</attribute>
        </optional>
      </element>
    </define>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index e05d5d7..68c8441 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -161,6 +161,12 @@ VIR_ENUM_IMPL(virDomainFS, VIR_DOMAIN_FS_TYPE_LAST,
                "file",
                "template")

+VIR_ENUM_IMPL(virDomainFSAccessMode, VIR_DOMAIN_FS_SECURITY_LAST,
+              "passthrough",
+              "mapped",
+              "squash")
+
+
  VIR_ENUM_IMPL(virDomainNet, VIR_DOMAIN_NET_TYPE_LAST,
                "user",
                "ethernet",
@@ -1847,6 +1853,7 @@ virDomainFSDefParseXML(xmlNodePtr node,
      char *type = NULL;
      char *source = NULL;
      char *target = NULL;
+    char *accessmode = NULL;

      if (VIR_ALLOC(def)<  0) {
          virReportOOMError();
@@ -1864,6 +1871,17 @@ virDomainFSDefParseXML(xmlNodePtr node,
          def->type = VIR_DOMAIN_FS_TYPE_MOUNT;
      }

+    accessmode = virXMLPropString(node, "accessmode");
+    if (accessmode) {
+        if ((def->accessmode = virDomainFSAccessModeTypeFromString(accessmode))<  0) {
+            virDomainReportError(VIR_ERR_INTERNAL_ERROR,
+                                 _("unknown accessmode '%s'"), accessmode);
+            goto error;
+        }
+    } else {
+        def->accessmode = VIR_DOMAIN_FS_ACCESSMODE_PASSTHROUGH;
+    }
+
      cur = node->children;
      while (cur != NULL) {
          if (cur->type == XML_ELEMENT_NODE) {
@@ -5602,6 +5620,7 @@ virDomainFSDefFormat(virBufferPtr buf,
                       int flags)
  {
      const char *type = virDomainFSTypeToString(def->type);
+    const char *accessmode = virDomainFSAccessModeTypeToString(def->accessmode);

      if (!type) {
          virDomainReportError(VIR_ERR_INTERNAL_ERROR,
@@ -5609,9 +5628,16 @@ virDomainFSDefFormat(virBufferPtr buf,
          return -1;
      }

+   if (!accessmode) {
+        virDomainReportError(VIR_ERR_INTERNAL_ERROR,
+                             _("unexpected accessmode %d"), def->accessmode);
+        return -1;
+    }
+
+
      virBufferVSprintf(buf,
-                      "<filesystem type='%s'>\n",
-                      type);
+                      "<filesystem type='%s' accessmode='%s'>\n",
+                      type, accessmode);

      if (def->src) {
          switch (def->type) {
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 7195c04..0668ce5 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -236,10 +236,20 @@ enum virDomainFSType {
      VIR_DOMAIN_FS_TYPE_LAST
  };

+/* Filesystem mount access mode  */
+enum virDomainFSAccessMode {
+    VIR_DOMAIN_FS_ACCESSMODE_PASSTHROUGH,
+    VIR_DOMAIN_FS_ACCESSMODE_MAPPED,
+    VIR_DOMAIN_FS_ACCESSMODE_SQUASH,
+
+    VIR_DOMAIN_FS_ACCESSMODE_LAST
+};
+
  typedef struct _virDomainFSDef virDomainFSDef;
  typedef virDomainFSDef *virDomainFSDefPtr;
  struct _virDomainFSDef {
      int type;
+    int accessmode;
      char *src;
      char *dst;
      unsigned int readonly : 1;
@@ -1167,6 +1177,7 @@ VIR_ENUM_DECL(virDomainDiskErrorPolicy)
  VIR_ENUM_DECL(virDomainController)
  VIR_ENUM_DECL(virDomainControllerModel)
  VIR_ENUM_DECL(virDomainFS)
+VIR_ENUM_DECL(virDomainFSAccessMode)
  VIR_ENUM_DECL(virDomainNet)
  VIR_ENUM_DECL(virDomainChrDevice)
  VIR_ENUM_DECL(virDomainChrChannelTarget)
diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index 18a302a..0961d8a 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -2783,11 +2783,17 @@ char *qemuBuildFSStr(virDomainFSDefPtr fs,

      if (fs->type != VIR_DOMAIN_FS_TYPE_MOUNT) {
          qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                        _("can only passthrough directories"));
+                        _("only supports mount filesystem type"));
          goto error;
      }

-    virBufferAddLit(&opt, "local,security_model=passthrough");
+    virBufferAddLit(&opt, "local");
+    if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_SQUASH) {
+        virBufferAddLit(&opt, ",security_model=none");
+    } else {
+        virBufferAddLit(&opt, ",security_model=%s",
+                        virDomainFSAccessModeTypeToString(fs->accessmode));
+    }
      virBufferVSprintf(&opt, ",id=%s%s", QEMU_FSDEV_HOST_PREFIX, fs->info.alias);
      virBufferVSprintf(&opt, ",path=%s", fs->src);


ACK, this gets my vote now.

Thanks Daniel, but extremely sorry that v1 has few errors which i missed in hurry, just sent v2 (tested).

Regards,
Harsh
Daniel


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