StoRM WebDAV storage area configuration

Each storage area is configured by placing a properties file in the /etc/storm/webdav/sa.d directory. StoRM WebDAV will look for configuration in all files ending with .properties in this directory. If no configuration files are found, the service will not start.

Storage area configuration properties

Authorization configuration

Up to version 1.2.0, StoRM WebDAV supported only flat authorization on storage areas. This means that the same access privileges would be granted to all the members of trusted VOMS Virtual Organization, or OpenID Connect/OAuth token issuer.

This authorization model is good enough in many scientific computing scenarios, and is the main one in use in WLCG computing.

Starting with version 1.3.1, StoRM WebDAV introduces a new authorization engine that allows for finer-grained auhtorization.

Flat authorization configuration

Anonymous access

To grant anonymous read access on the storage area, set anonymousReadEnabled=true.

X.509 authenticated access

To grant anonymous read access to users authenticated with an X.509 certificate issued by a trusted CA (i.e., users without VOMS credentials), set authenticatedReadEnabled=true.

VOMS authorization

Flat VOMS authorization is configured by including the VO that needs to be trusted in the vos property of the storage area configuration.

OAuth/OIDC authorization

Flat OAuth/OIDC authorization is enabled by including the token issuer in the orgs property of the storage area configuration.

Note that the token issuer must also be included in the list of trusted issuer for the whole service in the /etc/storm/webdav/config/application.yml file.

By default, only read access is granted to the storage area. To enable write access, set orgsGrantWritePermission=true.

WLCG JWT scope-based authorization

Starting with version 1.3.1, StoRM WebDAV introduces support for WLCG JWT profile scope-based authorization.

For this to work, add the trusted token issuer to the trusted ones (see above) and set wlcgScopeAuthzEnabled=true.

By default, adding a token issuer to the list of the trusted ones for a storage area will grant read access to the storage area. If you want to enforce WLCG scope-based authorization completely, set orgsGrantReadPermission=false.

Fine-grained authorization

Starting with version 1.3.1, StoRM WebDAV introduces a new authorization engine which allows for finer-grained authorization. It’s possible to define access policies for individual files/folders in the storage area, and targeting specific authenticated users or group of users.

More flexibility means also more configuration complexity. To enable fine-grained authorization on a storage area, set fineGrainedAuthzEnabled=true. The authorization engine will be activated together with other authorization mechanism described above.

Fine-grained authorization policies

Fine-grained authorization policies are defined using spring application configuration YAML files, i.e., typically by editing the /etc/storm/webdav/config/application.yml file.

An example set of policies is given below:

storm:
  authz:
    policies:
    - sa: wlcg
      actions:
      - list
      - read
      effect: permit
      description: Grant read access to any user
      principals:
      - type: anyone
    - sa: wlcg
      actions:
      - all
      effect: permit
      description: Grant read/write access to WLCG VOMS vo users
      principals:
      - type: vo
        params:
          vo: wlcg

Two policies are defined, for the wlcg storage area. These policies are flat, i.e. cover the whole storage area. The first policy allows read access to anonymous users. The second one allows read/write access to any user authenticated with VOMS credentials from the wlcg VO.

The policy above is basically equivalent to these settings in the storage area configuration.

anonymousReadEnabled=true
vos=wlcg

Using the fine-grained authorization engine is not convenient if the access model for the storage area is flat.

Policies are evaluated in the order in which they are defined, and the fist applicable one is used to render the authorization decision.

A policy contains the following directives:

• sa: The nome of the storage area to which the policy applies.

• actions: a list of actions that the policy is authorizing. Possible values:

  • list: the ability to list directory contents
  • read: the ability to read files
  • write: the ability to write files and create directories
  • delete: the ability to delete files/directories
  • all: a catchall for all other actions

• paths: the list of paths, within the storage area, the policy applies to. If omitted, the policy will apply to all paths.

  To match a directory and all its contents, use a wildcard like the following: /some/dir/**

• effect:

  • permit: defines a permit policy
  • deny: defines a deny policy

• description: A textual description of the policy. This is a required field, and is mainly useful to help debugging authorization problems.

• principals: a list of principals that the policy will apply to. Simple principal types are defined by a string value, while complex principal types require parameters.

  For example, the anyone principal is a simple principal type, while the jwt-group principal is a complex type that requires two parameters: the token issuer URI, and the group name.

  Principal	Type	Description	Parameters
  anyone	simple	will match any user (authenticated or not)	N/A
  any-authenticated-user	simple	will match any authenticated user	N/A
  anonymous	simple	will match any anonymous user	N/A
  vo	complex	will match authenticated users presenting a valid VOMS credential for a given VO.	vo: the name of the VO
  fqan	complex	will match authenticated users presenting a valid VOMS credential that contains the given FQAN.	fqan: the VOMS fqan
  jwt-group	complex	will match authenticated users with valid JWT token and belonging to the given group.	iss: the token issuer, group: the group name
  jwt-scope	complex	will match authenticated users with valid JWT token bearing the requested scope.	iss: the token issuer, scope: the scope
  jwt-issuer	complex	will match authenticated users with valid JWT token issued by the required token issuer	iss: the token issuer
  jwt-subject	complex	will match authenticated users with valid JWT token and presenting the requested subject claim.	iss: the token issuer, sub: the subject
  x509-subject	complex	will match authenticated users presenting a valid x.509 credential and a given subject	subject: the certificate subject, in RFC2253 format

Examples

storm:
  authz:
    policies:
    - sa: example
      actions:
      - list
      - read
      effect: permit
      paths:
      - /read-only/**
      description: Grant read access to any authenticated user to /read-only data
      principals:
      - type: anyone
    - sa: example
      actions:
      - all
      effect: permit
      description: Grant read/write access to the whole sa to /example/admins group members
      principals:
      - type: jwt-group
        params:
            iss: https://iam.example
            group: /example/admins
      - type: fqan
        params:
          fqan: /example/admins

The policies above grant:

• read-only access to anyone on the /read-only folder, in the example storage area
• all access to the example storage area to users in the group /example/admins, authenticated with VOMS or OpenID Connect