diff options
Diffstat (limited to 'multisite-identity-service-management.rst')
| -rw-r--r-- | multisite-identity-service-management.rst | 376 |
1 files changed, 376 insertions, 0 deletions
diff --git a/multisite-identity-service-management.rst b/multisite-identity-service-management.rst new file mode 100644 index 0000000..f46c4b4 --- /dev/null +++ b/multisite-identity-service-management.rst @@ -0,0 +1,376 @@ +This work is licensed under a Creative Commons Attribution 3.0 Unported +License. +http://creativecommons.org/licenses/by/3.0/legalcode + + +======================================= + Multisite identity service management +======================================= + +Glossary +======== + +There are 3 types of token supported by OpenStack KeyStone + **UUID** + + **PKI/PKIZ** + + **FERNET** + +Please refer to reference section for these token formats, benchmark and +comparation. + + +Problem description +=================== + +Abstract +------------ + +a user should, using a single authentication point be able to manage virtual +resources spread over multiple OpenStack regions. + +Description +------------ + +- User/Group Management: e.g. use of LDAP, should OPNFV be agnostic to this? + Reusing the LDAP infrastructure that is mature and has features lacking in +Keystone (e.g.password aging and policies). KeyStone can use external system to +do the user authentication, and user/group management could be the job of +external system, so that KeyStone can reuse/co-work with enterprise identity +management. KeyStone's main role in OpenStack is to provide +service(Nova,Cinder...) aware token, and do the authorization. You can refer to +this post https://blog-nkinder.rhcloud.com/?p=130.Therefore, LDAP itself should +be a topic out of our scope. + +- Role assignment: In case of federation(and perhaps other solutions) it is not + feasible/scalable to do role assignment to users. Role assignment to groups +is better. Role assignment will be done usually based on group. KeyStone +supports this. + +- Amount of inter region traffic: should be kept as little as possible, + consider CERNs Ceilometer issue as described in +http://openstack-in-production.blogspot.se/2014/03/cern-cloud-architecture-update-for.html + +Requirement analysis +=========================== + +- A user is provided with a single authentication URL to the Identity + (Keystone) service. Using that URL, the user authenticates with Keystone by +requesting a token typically using username/password credentials. The keystone +server validates the credentials, possibly with an external LDAP/AD server and +returns a token to the user. With token type UUID/Fernet, the user request the +service catalog. With PKI tokens the service catalog is included in the token. +The user sends a request to a service in a selected region including the token. +Now the service in the region, say Nova needs to validate the token. Nova uses +its configured keystone endpoint and service credentials to request token +validation from Keystone. The Keystone token validation should preferably be +done in the same region as Nova itself. Now Keystone has to validate the token +that also (always?) includes a project ID in order to make sure the user is +authorized to use Nova. The project ID is stored in the assignment backend - +tables in the Keystone SQL database. For this project ID validation the +assignment backend database needs to have the same content as the keystone who +issued the token. + +- So either 1) services in all regions are configured with a central keystone + endpoint through which all token validations will happen. or 2) the Keystone +assignment backend database is replicated and thus available to Keystone +instances locally in each region. + + Alt 2) is obviously the only scalable solution that produce no inter region +traffic for normal service usage. Only when data in the assignment backend is +changed, replication traffic will be sent between regions. Assignment data +includes domains, projects, roles and role assignments. + +Keystone deployment: + + - Centralized: a single Keystone service installed in some location, either + in a "master" region or totally external as a service to OpenStack + regions. + - Distributed: a Keystone service is deployed in each region + +Token types: + + - UUID: tokens are persistently stored and creates a lot of database + traffic, the persistence of token is for the revoke purpose. UUID tokens +are online validated by Keystone, each API calling to service will ask token +validation from KeyStone. Keystone can become a bottleneck in a large system +due to this. UUID token type is not suitable for use in multi region clouds at +all, no matter the solution used for the Keystone database replication (or +not). UUID tokens have a fixed size. + + - PKI: tokens are non persistent cryptographic based tokens and offline + validated (not by the Keystone service) by Keystone middleware +which is part of other services such as Nova. Since PKI tokens include endpoint +for all services in all regions, the token size can become big.There are +several ways to reduce the token size, no catalog policy, endpoint filter to +make a project binding with limited endpoints, and compressed PKI token - PKIZ, +but the size of token is still predictable, make it difficult to manage. If no +catalog applied, that means the user can access all regions, in some scenario, +it's not allowed to do like this. + + - Fernet: tokens are non persistent cryptographic based tokens and online + validated by the Keystone service. Fernet tokens are more lightweigth +then PKI tokens and have a fixed size. + + PKI (offline validated) are needed with a centralized Keystone to avoid +inter region traffic. PKI tokens do produce Keystone traffic for revocation +lists. + + Fernet tokens requires Keystone deployed in a distributed manner, again to +avoid inter region traffic. + + Cryptographic tokens brings new (compared to UUID tokens) issues/use-cases +like key rotation, certificate revocation. Key management is out of scope of +this use case. + +Database deployment: + + Database replication: + -Master/slave asynchronous: supported by the database server itself +(mysql/mariadb etc), works over WAN, it's more scalable + -Multi master synchronous: Galera(others like percona), not so scalable, +for multi-master writing, and need more parameter tunning for WAN latency. + -Symmetrical/asymmetrical: data replicated to all regions or a subset, +in the latter case it means some regions needs to access Keystone in another +region. + + Database server sharing: + In an OpenStack controller normally many databases from different +services are provided from the same database server instance. For HA reasons, +the database server is usually synchronously replicated to a few other nodes +(controllers) to form a cluster. Note that _all_ database are replicated in +this case, for example when Galera sync repl is used. + + Only the Keystone database can be replicated to other sites. Replicating +databases for other services will cause those services to get of out sync and +malfunction. + + Since only the Keystone database is to be sync replicated to another +region/site, it's better to deploy Keystone database into its own +database server with extra networking requirement, cluster or replication +configuration. How to support this by installer is out of scope. + + The database server can be shared when async master/slave repl is used, if +global transaction identifiers GTID is enabled. + + +Candidate solution analysis +------------------------------------ + +- KeyStone service (Distributed) with Fernet token + + Fernet token is a very new format, and just introduced recently,the biggest +gain for this token format is :1) lightweight, size is small to be carried in +the API request, not like PKI token( as the sites increased, the endpoint-list +will grows and the token size is too long to carry in the API request) 2) no +token persistence, this also make the DB not changed too much and with light +weight data size (just project. User, domain, endpoint etc). The drawback for +the Fernet token is that token has to be validated by KeyStone for each API +request. + + This makes that the DB of KeyStone can work as a cluster in multisite (for +example, using MySQL galera cluster). That means install KeyStone API server in +each site, but share the same the backend DB cluster.Because the DB cluster +will synchronize data in real time to multisite, all KeyStone server can see +the same data. + + Because each site with KeyStone installed, and all data kept same, +therefore all token validation could be done locally in the same site. + + The challenge for this solution is how many sites the DB cluster can +support. Question is aksed to MySQL galera developers, their answer is that no +number/distance/network latency limitation in the code. But in the practice, +they have seen a case to use MySQL cluster in 5 data centers, each data centers +with 3 nodes. + + This solution will be very good for limited sites which the DB cluster can +cover very well. + +- KeyStone service(Distributed) with Fernet token + Async replication ( + multi-cluster mode). + + We may have several KeyStone cluster with Fernet token, for example, +cluster1 ( site1, site2, … site 10 ), cluster 2 ( site11, site 12,..,site 20). +Then do the DB async replication among different cluster asynchronously. + + A prototype of this has been down on this. In some blogs they call it +"hybridreplication". Architecturally you have a master region where you do +keystone writes. The other regions is read-only. +http://severalnines.com/blog/deploy-asynchronous-slave-galera-mysql-easy-way +http://severalnines.com/blog/replicate-mysql-server-galera-cluster + + Only one DB cluster (the master DB cluster) is allowed to write(but still +multisite, not all sites), other clusters waiting for replication. Inside the +master cluster, "write" is allowed in multiple region for the distributed lock +in the DB. But please notice the challenge of key distribution and rotation for +Fernet token, you can refer to these two blogs: http://lbragstad.com/?p=133, +http://lbragstad.com/?p=156 + +- KeyStone service(Distributed) with Fernet token + Async replication ( + star-mode). + + one master KeyStone cluster with Fernet token in two sites (for site level +high availability purpose), other sites will be installed with at least 2 slave +nodes where the node is configured with DB async replication from the master +cluster members, and one slave’s mater node in site1, another slave’s master +node in site 2. + + Only the master cluster nodes are allowed to write, other slave nodes +waiting for replication from the master cluster ( very little delay) member. +But the chanllenge of key distribution and rotation for Fernet token should be +settled, you can refer to these two blogs: http://lbragstad.com/?p=133, +http://lbragstad.com/?p=156 + + Pros. + Why cluster in the master sites? There are lots of master nodes in the +cluster, in order to provide more slaves could be done with async. replication +in parallel. Why two sites for the master cluster? to provide higher +reliability (site level) for writing request. + Why using multi-slaves in other sites. Slave has no knowledge of other +slaves, so easy to manage multi-slaves in one site than a cluster, and +multi-slaves work independently but provide multi-instance redundancy(like a +cluster, but independent). + + Cons. The distribution/rotation of key management. + +- KeyStone service(Distributed) with PKI token + + The PKI token has one great advantage is that the token validation can be +done locally, without sending token validation request toKeyStone server. The +drawback of PKI token is 1) the endpoint list size in the token. If a project +will be only spread in very limited site number(region number), then we can use +the endpoint filter to reduce the token size, make it workable even a lot of +sites in the cloud. 2) KeyStone middleware(the old KeyStone client, which +co-locate in Nova/xxx-API) will have to send the request to the KeyStone server +frequently for the revoke-list, in order to reject some malicious API request, +for example, a user has be deactivated, but use an old token to access +OpenStack service. + + For this solution, except above issues, we need also to provide KeyStone +Active-Active mode across site to reduce the impact of site failure. And the +revoke-list request is very frequently asked, so the performance of the +KeyStone server needs also to be taken care. + + Site level keystone load balance is required to provide site level +redundancy. Otherwise the KeyStone middleware will not switch request to the +health KeyStone server in time. + + This solution can be used for some scenario, especially a project only +spread in limited sites ( regions ). + + And also the cert distribution/revoke to each site / API server for token +validation is required. + +- KeyStone service(Distributed) with UUID token + + Because each token validation will be sent to KeyStone server,and the token +persistence also makes the DB size larger than Fernet token, not so good as the +fernet token to provide a distributed KeyStone service. UUID is a solution +better for small scale and inside one site. + + Cons: UUID tokens are persistently stored so will cause a lot of inter +region replication traffic, tokens will be persisted for authorization and +revoke purpose, the frequent changed database leads to a lot of inter region +replication traffic. + +- KeyStone service(Distributed) with Fernet token + KeyStone federation You + have to accept the drawback of KeyStone federation if you have a lot of +sites/regions. Please refer to KeyStone federation section + +- KeyStone federation + In this solution, we can install KeyStone service in each site and with +its own database. Because we have to make the KeyStone IdP and SP know each +other, therefore the configuration needs to be done accordingly, and setup the +role/domain/group mapping, create regarding region in the pair.As sites +increase, if each user is able to access all sites, then full-meshed +mapping/configuration has to be done. Whenever you add one more site, you have +to do n*(n-1) sites configuration/mapping. The complexity will be great enough +as the sites number increase. + + KeyStone Federation is mainly for different cloud admin to borrow/rent +resources, for example, A company and B company, A private cloud and B public +cloud, and both of them using OpenStack based cloud. Therefore a lot of mapping +and configuration has to be done to make it work. + +- KeyStone service (Centralized)with Fernet token + + cons: inter region traffic for token validation, token validation requests +from all other sites has to be sent to the centralized site. Too frequent inter +region traffic. + +- KeyStone service(Centralized) with PKI token + + cons: inter region traffic for tokenrevocation list management, the token +revocation list request from all other sites has to be sent to the centralized +site. Too frequent inter region traffic. + +- KeyStone service(Centralized) with UUID token + + cons: inter region traffic for token validation, the token validation +request from all other sites has to be sent to the centralized site. Too +frequent inter region traffic. + +Prototype +----------- + A prototype of the candidate solution "KeyStone service(Distributed) with +Fernet token + Async replication ( multi-cluster mode)" has been executed Hans +Feldt and Chaoyi Huang, please refer to https://github.com/hafe/dockers/ . And +one issue was found "Can't specify identity endpoint for token validation among +several keystone servers in keystonemiddleware", please refer to the Gaps +section. + +Gaps +==== + Can't specify identity endpoint for token validation among several keystone +servers in keystonemiddleware. + + +**NAME-THE-MODULE issues:** + +* keystonemiddleware + + * Can't specify identity endpoint for token validation among several keystone + * servers in keystonemiddleware: + * https://bugs.launchpad.net/keystone/+bug/1488347 + +Affected By +----------- + OPNFV multisite cloud. + +Conclusion +----------- + + As the prototype demonstrate the cluster level aysn. replication capability +and fernet token validation in local site is feasible. And the candidate +solution "KeyStone service(Distributed) with Fernet token + Async replication ( +star-mode)" is simplified solution of the prototyped one, it's much more easier +in deployment and maintenance, with better scalability. + + Therefore the candidate solution "KeyStone service(Distributed) with Fernet +token + Async replication ( star-mode)" for multsite OPNFV cloud is +recommended. + +References +========== + + There are 3 format token (UUID, PKI/PKIZ, Fernet) provided byKeyStone, this +blog give a very good description, benchmark and comparation: + http://dolphm.com/the-anatomy-of-openstack-keystone-token-formats/ + http://dolphm.com/benchmarking-openstack-keystone-token-formats/ + + To understand the benefit and shortage of PKI/PKIZ token, pleaserefer to : + https://www.mirantis.com/blog/understanding-openstack-authentication-keystone-pk + + To understand KeyStone federation and how to use it: + http://blog.rodrigods.com/playing-with-keystone-to-keystone-federation/ + + To integrate KeyStone with external enterprise ready authentication system + https://blog-nkinder.rhcloud.com/?p=130. + + Key repliocation used in KeyStone Fernet token + http://lbragstad.com/?p=133, + http://lbragstad.com/?p=156 + + KeyStone revoke + http://specs.openstack.org/openstack/keystone-specs/api/v3/identity-api-v3-os-revoke-ext.html |