Securing COMSTAR and VMware iSCSI connections

Connecting VMware iSCSI sessions to COMSTAR or any iSCSI target provider securely is required to maintain a reliable system. Without some level of initiator to target connection gate keeping we will eventually encounter a security event. This can happen from a variety of sources, for example a non-cluster aware OS can connect to an unsecured VMware shared storage LUN and cause severe damage to it since the OS has no shared LUN access knowledge.  All to often we make assumptions that security is about confidentiality when it is actually more commonly about data availability and integrity which will both be compromised if an unintentional connection were to write on a shared LUN.

At the very minimum security level we should apply non-authenticated named initiator access grants to our targets. This low security method defines initiator to target connection states for lower security tolerant environments. This security method is applicable when confidentiality is not as important and security is maintained with the physical access control realm. As well it should also coincide with SAN fabric isolation and be strictly managed by the Virtual System or Storage Administrators. Additionally we can increase access security control by enabling CHAP authentication which is a serious improvement over named initiators. I will demonstrate both of these security methods using COMSTAR iSCSI Providers and VMware within this blog entry.

Before we dive into the configuration details lets examine how LU’s are exposed. COMSTAR controls iSCSI target access using several combined elements. One of these elements is within the COMSTAR STMF facility where we can assign membership of host and target groups. By default if we do not define a host or target group any created target will belong to an implied ALL group. This group as we would expect grants any connecting initiator membership to the ALL group assigned LUN’s. These assignments are called views in the STMF state machine and are a mapping function of the Storage Block Driver service (SBD) to the STMF IT_nexus state tables.

This means that if we were to create an initiator without assigning a host group or host/target group combination, an initiator would be allowed unrestricted connectivity to any ALL group LUN views and possibly without any authentication at all. Allowing this to occur would of course be very undesirable from a security perspective in almost all cases. Conversely if we use a target group definition then only the initiators that connect to the respective target will see the LUN views which are mapped on that target definition instance.

While target groups do not significantly improve access security it does provide a means controlling accessibility based on the definition of interface connectivity classes which in turn can be mapped out on respective VLAN priority groups, bandwidth availability and applicable path fault tolerance capabilities which are all important aspects of availability and unfortunately are seldom considered security concepts in many architectures.

Generally on most simple storage configurations the use of target groups is not a requirement. However they do provide a level of access control with LUN views. For example we can assign LUN views to a target group which in turn frees us from having to add the LUN view to each host group within shared LUN configurations like VMware stores. With combination’s of host and target groups we can create more flexible methods in respect to shared LUN visibility. With the addition of simple CHAP authentication we can more effectively insulate target groups. This is primarily due to the ability to assign separate CHAP user and password values for each target.

Lets look at this visual depiction to help see the effect of using target and host groups.

COMSTAR host and target view depiction

In this depiction any initiator that connects to the target group prod-tg1 will by default see the views that are mapped to that target groups interfaces. Additionally if the initiator is also a member of the host group prod-esx1 those view mapping will also be visible.

One major difference with target groups verses the all group is that you can define LU views on mass to an entire class of initiator connections e.g. a production class. This becomes an important control element in a unified media environment where the use of VLANs separates visibility. Virtual interfaces can be created at the storage server and attached to VLANs respectively. Target groups become a very desirable as a control within a unified computing context.

Named Initiator Access

Enabling named initiator to target using unauthenticated access with COMSTAR and VMware iSCSI services is a relatively simple operation. Let’s examine how this method controls initiator access.

We will define two host groups, one for production esx hosts and one for test esx hosts.

# stmfadm create-hg prod-esx1

# stmfadm create-hg test-esx1

With these host groups defined we individually assign LU’s views to the host groups and then we define any initiator to be a member of one of the host groups to which it would only see the views which belong to the host group and additionally any views assigned to the default all group.

To add a host initiator to a host group, we must first create it in the port provider of choice which in this case is the iSCSI port provider.

# itadm create-initiator

Once created the defined initiator can be added to a host group.

# stmfadm add-hg-member -g prod-esx1

An ESX host initiator with this iqn name can now attach to our COMSTAR targets and will see any LU views that are added to the prod-esx1 host group. But there are still some issues here, for example any ESX host with this initiator name will be able to connect to our targets and see the LUs. This is where CHAP can help to improve access control.

Adding CHAP Authentication on the iSCSI Target

Adding CHAP authentication is very easy to accomplish, we simply need to set a chap user name and secret on the respective iSCSI target. Here is an example of its application.

# itadm modify-target -s -u tcuid1

Enter CHAP secret:
Re-enter secret:

The CHAP secret must be between 12 and 255 characters long. The addition of CHAP allows us to further reduce any risks of a potential storage security event. We can define an additional target and they can have a different chap user names and or secrets.

CHAP is more secure when used in a mutual authentication back to the source initiator which is my preferred way to implement it on ESX 4 (ESX 3 does not support mutual chap). This mode does not stop a successful one-way authentication from an initiator to the target, it allows the initiator to request that the target host system iSCSI services must authenticate back to the initiator which provides validation that the target is indeed the correct one. Here is an example of the target side initiator definition that would provide this capability.

# itadm modify-initiator -s -u icuid1

Enter CHAP secret:
Re-enter secret:

Configuring the ESX 4 Software iSCSI Initiator

On the ESX 4 host side we need to enter our initiator side CHAP values.



Be careful here, there are three places we can configure CHAP elements. The general tab allows a global point of admin where any target will inherit those entered values by default where applicable e.g. target chap settings. The the dynamic tab can override the global settings and as well the static tab overrides the global and dynamic ones. In this example we are configuring a dynamically discovered target to use mutual (aka bidirectional) authentication.

In closing CHAP is a reasonable method to ensure that we correctly grant initiator to target connectivity assignments in an effort to promote better integrity and availability. It does not however provide much on the side of confidentially for that we need more complex solutions like IPSec.

Hope you found this blog interesting.




Site Contents: © 2009  Mike La Spina

Multi Protocol Storage Provisioning with COMSTAR

 COMSTAR is a new breed of open source storage product available to the world. What was traditionally a closed and proprietary storage capability is now available to our open source communities. With OpenSolaris and COMSTAR the ability to freely provision virtual storage services over very mature high end protocols on standard commodity server hardware is now a reality. High performance transports are integral within the feature sets of COMSTAR and Sun’s open source portfolio of projects. The COMSTAR product is revolutionary in its method of provisioning storage virtualization and transport services to storage resource consumers.
COMSTAR provisions virtualized SCSI block storage over multiple SCSI transport protocols. While this function class is not new to us the ease of implementation using COMSTAR certainly is. All the complexities of using a multi protocol target services platform are cleaned up. It is simple to use and facilitates advanced high performance storage provisioning at the block level.
The services within this product have multiple common storage provisioning applications. One very interesting application is a storage gateway server and this blog demonstrates howto build a Fiber Channel (FC) storage gateway using the COMSTAR service layers and as well provision some additional features using the target services.


 COMSTAR FC Gateway Architecture by Mike La Spina

In this example instance we are re-provisioning an existing storage system with an OpenSolaris COMSTAR configuration running on a commodity white box which functions as a storage server head that can compress, scrub, thin provision, replicate, snapshot and clone the existing block storage attachments. The example FC based storage could also be comprised of a JBOD FC array directly attached to the OpenSolaris storage head if we so desired or many other commonly available SCSI attachment methods. The objective here is to extend and enhance any block storage system with high performance transports and virtualization features. Of course we could also formalize the white box to an industrial strength host once we are satisfied that the proof of concept is mature and optimal.  

The reality is that many older existing FC storage systems are installed without these features primarily due to the excessive licensing costs of them. And even when these features are available, its use is probably restricted to like proprietary systems thus obsolescing the entire lot of any useful future functionality. But what if you could re-purpose an older storage system to act as a DR store or backup cache system or maybe a test and development environment. With today’s economy this is from a cost perspective, very attractive and can be accomplished with very little risk on the investment side.

One of the possible applications for this flexible storage service is the re-provisioning of existing LUN’s from an existing system to newer more flexible SCSI transport protocols. This is particularly useful when we need to re-target the existing storage system from FC to iSCSI or the likes of. We can begin by exploring this functionality and explain how COMSTAR can provide us with this service.

First we need to understand the high level functionality of the COMSTAR service layers. Virtual LUN’s on COMSTAR are provisioned with a service layer named the LU provider. This layer maps backing stores of various types to a storage GUID assignment and additionally defines other properties like the LUN ID and size dimensions. This layer allows us to carve out the available block storage devices that are accessible on our OpenSolaris storage host. For example if we attached an FC Initiator to an external storage system we can then map the accessible SCSI block devices to the LU provider layer and then present this virtualized LUN to the other COMSTAR service layers for further processing.

Once we have defined the LU’s we can present this storage resource to the SCSI Target Mode Framework Service (STMF) layer which acts as the storage gate keeper. At this layer we define which clients (initiators) can connect to the LU’s based on Membership of Target Groups and Host Groups that are assigned logical views of the LU(s). The STMF layer routes the defined LU(s) as SCSI targets over a multiprotocol interface connection pool to a Port Provider. Port Providers are the protocol connection service instances which can be the likes of FC, iSCSI, SAS, iSER, FCoE and so on. 

With these COMSTAR basics in mind let us begin by diving into some of the details of how this can be applied.  

Sun has detailed howto setup COMSTAR at so no need to re-invent the wheel here.

Just as a note SXCE snv_103 and up integrate the COMSTAR FC and iSCSI port provider code. With the COMSTAR software components and FC target setup we can demonstrate the re-provisioning of an existing FC based storage server. Since I don’t have the luxury of having a proprietary storage server at home I will emulate this storage using an additional COMSTAR white box to act as the FC storage target to be re-provisioned.

On the existing FC target system we need to create Raid0 arrays of three disks each which will total up to a set of six trios. We will use these six non-fault tolerant disk groups as vdevs for a ZFS raidz2 group. This will allow us to create fault tolerant arrays from the existing storage server. The reasons for sets of three Raid0 groupings are to reduce the possibility of reaching the LUN maximums of the proprietary storage system and also we do not want to erode the performance by layering Raid 5 groups. As well we can tolerate a disk failure in two of the trios since we have Raidz2 across the Raid0 trio groups. Additionally using these Raid0 disk groups actually lowers the array failure probability rate. For example if a second disk were to failure in a single Raid0 set there would be no additional impact to other trios, thus reducing the overall failure rate. 

To create the emulated FC storage system I have defined the following 16G ZFS sparse volumes respectively named trio1 through trio6 each as a representation of the 3 disk Raid0 spanned LUN on a source storage host named ss1. 

root@ss1:~# zfs create sp1/gw
root@ss1:~# zfs create -s -V 16G sp1/gw/trio1
root@ss1:~# zfs create -s -V 16G sp1/gw/trio2
root@ss1:~# zfs create -s -V 16G sp1/gw/trio3
root@ss1:~# zfs create -s -V 16G sp1/gw/trio4
root@ss1:~# zfs create -s -V 16G sp1/gw/trio5
root@ss1:~# zfs create -s -V 16G sp1/gw/trio6

Once these mockup volumes are created they are then defined as backing stores using the sbdadm utility as follows.

root@ss1:~# sbdadm create-lu /dev/zvol/rdsk/sp1/gw/trio1

Created the following LU:

              GUID                    DATA SIZE           SOURCE
——————————–  ——————-  —————-
600144f01eb3862c0000494b55cd0001      17179803648      /dev/zvol/rdsk/sp1/gw/trio1

All the backing stores were added to the LU provider service layer to which in turn were assigned to the STMF service layer. Here we can see the automatically generated GUID’s that are assigned to the ZFS backing stores.

root@ss1:~# sbdadm list-lu

Found 6 LU(s)

              GUID                    DATA SIZE           SOURCE
——————————–  ——————-  —————-
600144f01eb3862c0000494b56000006      17179803648      /dev/zvol/rdsk/sp1/gw/trio6
600144f01eb3862c0000494b55fd0005      17179803648      /dev/zvol/rdsk/sp1/gw/trio5
600144f01eb3862c0000494b55fa0004      17179803648      /dev/zvol/rdsk/sp1/gw/trio4
600144f01eb3862c0000494b55f80003      17179803648      /dev/zvol/rdsk/sp1/gw/trio3
600144f01eb3862c0000494b55f50002      17179803648      /dev/zvol/rdsk/sp1/gw/trio2
600144f01eb3862c0000494b55cd0001      17179803648      /dev/zvol/rdsk/sp1/gw/trio1

A host group was defined named GW1 and respectively these LU GUID’s were added to the GW1 host group as LU views assigning LUN 0 to 5.

Just as a note the group names are case sensitive. 
root@ss1:~#stmfadm create-hg GW1

Here we assigned the GUID’s a LUN value on the GW1 host group with the -n parm.   

root@ss1:~# stmfadm add-view -h GW1 -n 0 600144F01EB3862C0000494B55CD0001
root@ss1:~# stmfadm add-view -h GW1 -n 1 600144F01EB3862C0000494B55F50002
root@ss1:~# stmfadm add-view -h GW1 -n 2 600144F01EB3862C0000494B55F80003
root@ss1:~# stmfadm add-view -h GW1 -n 3 600144F01EB3862C0000494B55FA0004
root@ss1:~# stmfadm add-view -h GW1 -n 4 600144F01EB3862C0000494B55FD0005
root@ss1:~# stmfadm add-view -h GW1 -n 5 600144F01EB3862C0000494B56000006

With the LU’s now available in a host group view we can add the COMSTAR re-provisioning gateway server FC wwn’s to this host group and it will become available as a storage resource on the re-provisioning gateway server named ss2. We need to obtain the wwn from the gateway server using the fcinfo hba-port command.  
root@ss2:~# fcinfo hba-port
HBA Port WWN: 210000e08b100163
        Port Mode: Initiator
        Port ID: 10300
        OS Device Name: /dev/cfg/c8
        Manufacturer: QLogic Corp.
        Model: QLA2300
        Firmware Version: 03.03.27
        FCode/BIOS Version:  BIOS: 1.47;
        Serial Number: not available
        Driver Name: qlc
        Driver Version: 20080617-2.30
        Type: N-port
        State: online
        Supported Speeds: 1Gb 2Gb
        Current Speed: 2Gb
        Node WWN: 200000e08b100163
        NPIV Not Supported

Using the stmfadm utility we add the gateway server’s wwn address to the GW1 host group. 
root@ss1:~# stmfadm add-hg-member -g GW1 wwn.210000e08b100163

Once added to ss1 we can see that it is indeed available and online. 
root@ss1:~# stmfadm list-target -v

Target: wwn.2100001B320EFD58
    Operational Status: Online
    Provider Name     : qlt
    Alias             : qlt2,0
    Sessions          : 1
        Initiator: wwn.210000E08B100163
            Alias: :qlc1
            Logged in since: Fri Dec 19 01:47:07 2008

The cfgadm command will scan for the newly available LUN’s and now we can access the emulated (aka boat anchor) storage system using our gateway server ss2. Of course we could also set up more initiators and access it over a multipath connection.  

cfgadm -a

root@ss2:~# format
Searching for disks…done

       0. c0t600144F01EB3862C0000494B55CD0001d0 <DEFAULT cyl 2086 alt 2 hd 255 sec 63>

       1. c0t600144F01EB3862C0000494B55F50002d0 <DEFAULT cyl 2086 alt 2 hd 255 sec 63>

       2. c0t600144F01EB3862C0000494B55F80003d0 <DEFAULT cyl 2086 alt 2 hd 255 sec 63>

       3. c0t600144F01EB3862C0000494B55FA0004d0 <DEFAULT cyl 2086 alt 2 hd 255 sec 63>

       4. c0t600144F01EB3862C0000494B55FD0005d0 <DEFAULT cyl 2086 alt 2 hd 255 sec 63>

       5. c0t600144F01EB3862C0000494B56000006d0 <DEFAULT cyl 2086 alt 2 hd 255 sec 63>

Now that we some FC LUN connections configured from to the storage system to be re-provisioned we can create a ZFS based pool which grants us the ability to carve out the block storage in a virtual manner. As discussed previously we will use raid dp a.k.a. raidz2 to provide a higher level of availability with the zpool create raidz2 option command.

root@ss2:~# zpool create gwrp1 raidz2 c0t600144F01EB3862C0000494B55CD0001d0 c0t600144F01EB3862C0000494B55F50002d0 c0t600144F01EB3862C0000494B55F80003d0 c0t600144F01EB3862C0000494B55FA0004d0 c0t600144F01EB3862C0000494B55FD0005d0 c0t600144F01EB3862C0000494B56000006d0

A quick status check reveals all is well with the ZFS pool.

root@ss2:~# zpool status gwrp1
  pool: gwrp1
 state: ONLINE
 scrub: none requested

        NAME                                       STATE     READ WRITE CKSUM
        gwrp1                                      ONLINE       0     0     0
          raidz2                                   ONLINE       0     0     0
            c0t600144F01EB3862C0000494B55CD0001d0  ONLINE       0     0     0
            c0t600144F01EB3862C0000494B55F50002d0  ONLINE       0     0     0
            c0t600144F01EB3862C0000494B55F80003d0  ONLINE       0     0     0
            c0t600144F01EB3862C0000494B55FA0004d0  ONLINE       0     0     0
            c0t600144F01EB3862C0000494B55FD0005d0  ONLINE       0     0     0
            c0t600144F01EB3862C0000494B56000006d0  ONLINE       0     0     0

Let’s carve out some of this newly created pool as a 32GB sparse volume. The -p option creates the full path if it does not currently exist.

root@ss2:~# zfs create -p -s -V 32G gwrp1/stores/lun0

root@ss2:~# zfs list
NAME                         USED  AVAIL  REFER  MOUNTPOINT
gwrp1                        220K  62.6G  38.0K  /gwrp1
gwrp1/stores                67.9K  62.6G  36.0K  /gwrp1/stores
gwrp1/stores/lun0           32.0K  62.6G  32.0K  -

With a slice of the pool created we can now assign a GUID within the LU Provider layer using the sbdadm utility.

root@ss2:~# sbdadm create-lu /dev/zvol/rdsk/gwrp1/stores/lun0

Created the following LU:

              GUID                    DATA SIZE           SOURCE
——————————–  ——————-  —————-
600144f07ed404000000496813070001      34359672832      /dev/zvol/rdsk/gwrp1/stores/lun0

The LU Provider layer can also provision sparse based storage. However in this case the ZFS backing store is already thin provisioned. If this were a physical disk backing store it would be prudent to use the LU Provider’s sparse/thin provisioning feature. At this point we are ready to create the STMF Host Group and View that will be used to demonstrate a real world example of the multi protocol capability with the COMSTAR OpenStorage ss2 host. In this case I will use VMware ESX as a storage consumer. To reflect the host group type we will name it ESX1 and then we need to add a view for the LU GUID of the virtualized storage.

root@ss2:~# stmfadm create-hg ESX1

root@ss2:~# stmfadm add-view -h ESX1 -n 1 600144f07ed404000000496813070001

root@ss2:~# stmfadm list-view -l 600144F07ED404000000496813070001
View Entry: 0
    Host group   : ESX1
    Target group : All
    LUN          : 1

With a view defined for the VMware hosts let’s add an ESX host FC HBA wwn membership to the defined ESX1 host group. We need to retrieve the wwn from the VMware server using either the console or a Virtual Infrastructure Client GUI. Personally I like the console esxcfg-info tool, however if it’s an ESXi host then the GUI will serve the info just as well.

VMware Screen shot WWN by Mike La Spina

[root@vh1 root]# esxcfg-info -s | grep ‘Adapter WWN’
                     |—-Adapter WWNN…………………………20:00:00:e0:8b:01:f7:e2

root@ss2:~# stmfadm add-hg-member -g ESX1 wwn.210000e08b01f7e2

And the result of this change after we issue a rescan on vmhba1 and create a VMFS volume named ss2-cstar-zs0.0 with the re-provisioned storage is reflected here.

VMware Screen shot VMFS volume by Mike La Spina

This crafted storage is now a thinly provisioned VMFS store that can deliver replication, snapshots, cloning, advanced error detection and can also be re-platformed to a new storage system at a later date using ZFS’s hardware autonomy. The storage server is very attractive as it creates a level of future proofing and insulates the storage consumers from proprietary vendor lock in. But that’s not the best part of this example. Let’s say you wish provide different tiers of connectivity services for your storage consumers. For example we could attach a development or test environment using an iSCSI protocol and the more critical environments can use FC or FCoE based protocol.
So let’s look at how we can add a second SCSI transport protocol to this interesting configuration.
Just as a note the new iSCSI port provider is a kernel based implementation and has superior performance to its predecessor iscsitgt user land implementation.

To add the iSCSI protocol we need to enable the iscsi/target port provider service.





root@ss2:~# svcadm enable iscsi/target

Now we need to create an iSCSI target and iSCSI initiator definition so that we can add the iSCSI initiator to the ESX1 host group. As well we should define a target portal group so we can control what host IP(s) will service this target.

root@ss2:~# itadm create-tpg 2

root@ss2:~# itadm create-target

root@ss2:~# itadm create-target -n -t 2
Target successfully created

By default the iqn will be created as a member of the All targets group.

If we left out the parameters the itadm utility would create an iqn GUID and use the default target portal group of 1. And yes for those familiar with the predecessor iscsitadm utility we can now create a iqn name at the command line.

At this point we need to define the initiator iqn to the iSCSI port provider service and if required additionally secure it using CHAP. We need to retrieve the VMware initiator iqn name from either the Virtual Infrastructure Client GUI or console command line. Just as a note if we did not specify a host group when we defined our view the default would allow any initiator FC, iSCSI or otherwise to connect to the LU and this may have a purpose but generally it is a bad practice to allow in most configurations. Once created the initiator is added to the ESX1 host group thus enables our second access protocol to the same LU.

[root@vh1 root]# esxcfg-info -s | grep ‘iqn’
         |—-ISCSI Name……………………………………
         |—-ISCSI Alias……………………………………

root@ss2:~# itadm create-initiator

root@ss2:~# stmfadm add-hg-member -g ESX1

After adding the ss2 iSCSI interface IP to VMware’s Software iSCSI initiator we now have a multipath multiprotocol connection to our COMSTAR storage host.

 VMware iqn example By Mike La Spina

VMware mpath example by Mike La Spina 

This is simply the most functional and advanced Open Source storage product in the world today. Here we have commodity white boxes serving advanced storage protocols in my home lab, can you imagine what could be done with Data Center class server hardware and Fishworks. You can begin to see the advantages of this future proof platform. As protocols like FCoE, Infiniband and iSER (iSCSI without the TCP session overhead) already working in COMSTAR the Sun Software Engineers and OpenSolaris community are crafting outstanding storage products.

Hope you found this blog to be interesting.







Site Contents: © 2009  Mike La Spina