EDIT

# Cdm authorisation and access control

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*Another page on this topic is found in the BDI wiki: http://wiki.bgbm.org/bdinotes/index.php/EDIT_Security*

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It is evident that the cdm library needs authorisation and access control. There are library methods which need to protected from unauthorised execution and there is also the data which is exposed by the library. Not all data should be visible to every user so a [[HibernateSpringAndRowlevelSecurity|row level access control]] is needed.

## Questions

1. Do we need a access control in the web service (cdmlib-remote) or is it sufficient to protect the service layer. As long web service controllers are not using DAO (cdmlib-persistence) methods directly it should not be necessary.

## Use cases

 A. a specific **classification sub tree** is **publicly visible** that is it is _published_

 B. a specific **classification sub tree** must not be **publicly visible** in the data portal and thus must be also hidden in the web service responses

 C. a specific **classification sub tree** is only visible for users which have a specific **role** but the user is not granted to **edit** anything in/below it

 D. A user is only granted to **edit Descriptions** 

 E. A user is only granted to **edit DescriptionElements** of a specific _Feature_ 

 F. A user is only granted to **edit structured Descriptions** 

 G. Combinations of B, C and D, E must be possible

 H. Only users with the **roles** *Admin* or **Usermanager** or the user in question it self (if currently authenticated) are allowed to execute **change password** 

 I. Only users with the **roles** *Admin* or **Usermanager** are allowed to create or **edit** new users

~~~

<code class="rst">

Tabular summary of above use cases translated into roles:

===========  =========================  ======================================  ===============  =============================

\                                                                               what to protect

-----------  -------------------------  --------------------------------------  ----------------------------------------------

Usecase      Role                       authority string                        Entity            ServiceMethod

===========  =========================  ======================================  ===============  =============================

A.           Anonymous                  TaxonNode.[READ]{uuid}                     ...

B.           TaxGroupX_User             TaxonNode.[READ]{uuid}                     ...

C.           TaxGroupX_Editor           TaxonNode.[UPDATE]{uuid}                   ...

D.           DescriptionEditor		Description.[UPDATE]			 ...					

E.           DescriptionEditor		DescriptioElement(Ecology).[UPDATE]        ...					

H.           Admin, Usermanager                                                                  UserService.changePassword()

===========  =========================  ======================================  ===============  =============================

*Anonymous* means not authenticated  

~~~

 **Special cases:** 

* **@TaxonNames@** can potentially be shared between different taxa, thus a situation may occur where a user has grants to edit taxon A but not for taxon B, but both taxa are sharing the same name. How will we handle this situation, should the name be cloned when the user starts editing taxon A, so that taxon A has another name entity than taxon B after the user saved the latest changes?

* The same problem as described above for TaxonNames also accounts for *@References@*, but in this case the problem is more severe since references are very often part of multiple taxon names. 

## Implementation details

_only a brief note for now, compiled by a lot of copy paste from the java doc:_

### Roles and CdmAuthorities

#### Roles

only one hard coded role: `ROLE_ADMIN` 

#### CdmAuthority

A `CdmAuthority` consists basically of two parts which are separated by a dot character '.'.

* permissionClass: an `CdmPermissionClass` instance with represents a cdm type or a part of the cdm type hierarchy. The className is always represented as an upper case string.

* property: The `CdmAuthority` only applies to instances which satisfy the specified property. Interpretation is up to type specific voters.

* operation: a string which specifies a `Operation` on that set of cdm types

* targetUuid: The operation may be restricted to a specific cdm entity by adding the entity uuid to the operation. The uuid string is enclosed in curly brackets '{' , '}' and appended to the end of the operation.

Examples for permissionStrings:

~~~

 TAXONBASE.[CREATE]

 TAXONBASE.[READ]

 TAXONBASE.[UPDATE]

 TAXONBASE.[DELETE]

 TAXONBASE.[DELETE,CREATE,UPDATE,READ]

 DESCRIPTIONBASE.UPDATE]

 DESCRIPTIONELEMENTBASE(Ecology).UPDATE]

 TAXONNODE.UPDATE{20c8f083-5870-4cbd-bf56-c5b2b98ab6a7}

~~~

in contrast to CdmAuthorities there are more general role like the following listed below, all these roles are having the  role prefix `'ROLE_'` which is defined in the String Security RoleVoter class:

~~~

 ROLE_ADMIN

 ROLE_USER_MANAGER

~~~

### Permission Groups

Permission groups can usually created as needed. The group name should reflect semantics the nature of the permission group.

The cdm provides default permission groups which are created by the `FirstDataInserter` in case they do not yet exist. See #4082 (implement default permission groups) for implementation details. Currently the following default permission groups exist: 

1. *Editor*: Contains all Authorities which are required to be granted for general editing, except the Authority for a specific taxonomical group. In order to actually enable an Editor to edit something it must be associated with a TAXONNODE Authority, e.g: @TAXONNODE.[CREATE,UPDATE,DELETE,READ]{...@}. Users which belong to this permission group are prohibited from toggling the publish-flag and from changing or deleting references and authors, but are able to create new ones. Once a 'Editor' has created a new Reference or Author the new entity is considered being still in the process of being created for some time even if the entity has already been saved to the database. See #4305 (newly created entities must stay editable even if a user only has the permission to create them) for implementation details on this feature.

~~~

REFERENCE.[CREATE,READ]

TAXONNAMEBASE.[CREATE,READ,UPDATE]

TEAMORPERSONBASE.[CREATE,READ]

TAXONBASE.[CREATE,UPDATE,DELETE,READ]

DESCRIPTIONBASE.[CREATE,UPDATE,DELETE,READ]

DESCRIPTIONELEMENTBASE.[CREATE,UPDATE,DELETE,READ]

~~~

1. *ProjectManager*: A permission group which enables a User to edit and delete entities which are of central importance for a whole project. Users which belong to this permission group are granted to edit and delete taxa, names, references, authors, terms and can toggle the publish-flag on taxa, speciemens and occurrences.

~~~

REFERENCE.[UPDATE,DELETE]

TAXONNAMEBASE.[DELETE]

TEAMORPERSONBASE.[UPDATE,DELETE]

ROLE_PROJECT_MANAGER

~~~

### Authorisation control

Different approaches of authorisation control need to be used in order to implement all kinds of CRUD permissions:

* service layer: method `@PreAuthorize` annotations with Spring EL, e.g. UserService:

~~~

@PreAuthorize("#username == authentication.name or hasRole('ROLE_ADMIN')")

public void changePasswordForUser(String username, String newPassword) {

...

~~~

* UPDATE and CREATE of cdm instances is protected by a Hibernate interceptor, the `CdmSecurityHibernateInterceptor@. This interceptor implements the  @onSave()` and `onFlushDirty` methods and thus can control creation and updating of cdm objects. Hibernate calls these methods for any entity which needs to be persisted even if a save or update operations causes a cascading save of objects connected to the object graph which is being saved. **TODO** implement DELETE (#3079)

* READ permissions can not be implemented using the `CdmSecurityHibernateInterceptor@. Reasons: @onLoad()` is called just before an object is initialized, so the object has no uuid or anything else with would be needed to decide on principals authorisation. A row based access control mechanism is required, see [[HibernateSpringAndRowlevelSecurity]]

### Authorisation evaluation

One of the central classes for the evaluation of Roles and CdmAuthorities is the `CdmPermissionEvluator` with implements the `org.springframework.security.access.PermissionEvaluator@. The method @public boolean hasPermission(Authentication authentication, Object targetDomainObject, Object permission)` will always return true if the authentication has the role `ROLE_ADMIN` otherwise decission making is delegated to a `AccessDecisionManager` which should be `UnanimousBasedUnrevocable@. This @AccessDecisionManager` polls all configured AccessDecisionVoters grants access if only grant (or abstain) votes were received. The `AccessDecisionManager` then asks the set of plugged in **@AccessDecisionVoter@s*. The cdm specific voters are found in the package eu.etaxonomy.cdm.persistence.hibernate.permission.voter. For actual configuration details please see the *persistence_security.xml** , here is an example: 

~~~

<bean id="accessDecisionManager" class="org.springframework.security.access.vote.UnanimousBasedUnrevocable">

        <property name="decisionVoters">

            <list>

                <bean class="eu.etaxonomy.cdm.persistence.hibernate.permission.voter.GrantAlwaysVoter" />

                <bean class="eu.etaxonomy.cdm.persistence.hibernate.permission.voter.TaxonNodeVoter" />

                <bean class="eu.etaxonomy.cdm.persistence.hibernate.permission.voter.TaxonBaseVoter" />

                <bean class="eu.etaxonomy.cdm.persistence.hibernate.permission.voter.DescriptionBaseVoter" />

                <bean class="eu.etaxonomy.cdm.persistence.hibernate.permission.voter.DescriptionElementVoter" />

            </list>

        </property>

</bean>

<!--

    CdmPermissionEvaluator.hasPermissions() evaluates the CdmPermissions like TAXONNODE.[UPDATE]{20c8f083-5870-4cbd-bf56-c5b2b98ab6a7}

-->

<bean id="cdmPermissionEvaluator" class="eu.etaxonomy.cdm.persistence.hibernate.permission.CdmPermissionEvaluator">

    <property name="accessDecisionManager" ref="accessDecisionManager" />

</bean>

~~~

#### AccessDecisionVoters

As briefly described above, the AccessDecisionVoters are crucial for finding a decision on whether a user is allowed to perform an operation on a specific cdm object or class of cdm objects. The operations are the so called CRUD operations. This acronym refers to Create, Read, Update, Delete. 

A user can have one or multiple granted authorities, for more information on granted authorities please refer to the paragraph [[CdmAuthorisationAndAccessControl#CdmAuthority|CdmAuthority]] above. All voters will cast votes on all granted authorities a user has.

In the following we will just use the term voter as a short form for AccessDecisionVoter. 

Voters can cast three different vote:

* Allow

* Deny 

* Abstain

In order to make a access decision the AccessDecisionVoters are asked sequentially to cast their vote. If at least one voter casts _Deny_ the the whole operation will be denied. This behaviour is guaranteed by the `GrantAlwaysVoter` which will always cast an _Allow_.

All AccessDecisionVoters are responsible for a specific class of data entities and thus it will only cast an _Allow_ or _Deny_ vote when an operation on an object of this class is to be performed. If a voter is not responsible it will _Abstain_. If a voter "feels" not responsible it casts an _Abstain_. As a consequence of this concept everything is allowed unless a voter is responsible for a specific object class. Only in this case there is the potential that an operation will be denied.

Generally each of the voters will check if the user has a granted authority which matches the the operation and object. Voters can also perform additional checks (see TaxonNodeVoter, DescriptionElementVoter) which can take related objects into account (parent taxon nodes) or specific properties of of Objects (feature of description element).

List of existing AccessDecisionVoters in the order of their execution:

1. TaxonNodeVoter: 

  * responsible for TaxonNode

  * allows if voter is responsible for the object class in question and

    1. if the user has a granted authority for that specific object or for all objects of this class which matches the operation to be performed

    1. or if the user has a matching granted authority for any of the parent taxon nodes in the classification (e.g.: @TAXONNODE.UPDATE{20c8f083-5870-4cbd-bf56-c5b2b98ab6a7@})

  * denies otherwise

1. TaxonBaseVoter:  

  * responsible for Taxon, Synonym

  * allows if voter is responsible for the object class in question and

    1. if the user has a granted authority for that specific object or for all objects of this class which matches the operation to be performed (e.g.: @TAXONBASE.UPDATE@)

  * denies otherwise

1. DescriptionBaseVoter:  

  * responsible for TaxonDescription, SpecimenDescription

  * allows if voter is responsible for the object class in question and

    1. if the user has a granted authority for that specific object or for all objects of this class which matches the operation to be performed (e.g.: @DESCRIPTIONBASE.UPDATE@)

  * denies otherwise

1. DescriptionElementVoter:  

  * responsible for all types of DescriptionElements

  * allows if voter is responsible for the object class in question and

    1. if the user has a granted authority for that specific object or for all objects of this class which matches the operation to be performed

    1. if the the operation to be preformed is specific to the Feature of the Description Element and if the _Property_ of one of the users granted authorities matches this Feature. (e.g.: @DESCRIPTIONELEMENTBASE(Ecology).[UPDATE]@)

  * denies otherwise