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opa-openshift

An OPA-compatible API for making OpenShift access review requests.

API

POST /v1/data/{package}/{rule}

The opa-openshift HTTP server exposes a single endpoint of the OPA Data API and fulfills requests by translating them into Kubernetes SubjectAccessReviews. This endpoint expects an OPA Input Document in the body of the request with the following structure:

{
    "input": {
        "groups": ["string"],
        "permission": "string",
        "resource": "string",
        "subject": "string",
        "tenant": "string"
    }
}

It returns a response with the following structure:

{
    "result": "boolean"
}

Optionally, if a label set matcher is set by --opa.matcher, it returns a response with the following structure:

{
    "result": {
        "allowed": "boolean",
        "data": [{
            "name": "string", 
            "type": "string", 
            "value": "string"
        }]
    }
}

The data section represents a PromQL-style Label matcher:

Key Description
name The value of the --opa.matcher flag
type The value is per default MatchRegexp
value A comma-separated list of OpenShift projects the subject has access to.

Design

The opa-openshift authorization process translates in general an OPA Data Request V1 into a SubjectAccessReview.

To authorize the subject against a resource for a tenant, the server requires a list of tenant to api group mappings, e.g.:

./opa-openshift \
   --openshift-mappings=tenant-a=observatorium.openshift.io

Assuming an input data request, e.g.:

{
    "input": {
        "groups": ["system:authenticated"],
        "permission": "read",
        "resource": "resource-name",
        "subject": "k8suser",
        "tenant": "tenant-a"
    }
}

The input is translated to the following SelfSubjectAccessReview:

{
    "apiVersion": "authorization.k8s.io/v1",
    "kind": "SelfSubjectAccessReview",
    "spec": {
        "resourceAttributes": {
            "resource": "tenant-a",
            "resourceName": "resource-name",
            "verb": "get",
            "apiGroup": "observatorium.openshift.io"
        }
    }
}

If the subject's k8suser role bindings allow an access to the resource description in resourceAttributes, then the SelfSubjectAccessReview's status will result in:

{
    "apiVersion": "authorization.k8s.io/v1",
    "kind": "SelfSubjectAccessReview",
    "spec": {},
    "status": {                                                                                                                                                                                  
        "allowed": true,
        "reason": "RBAC: allowed by RoleBinding \"tenant-a-binding\" of Role \"tenant-a\" to User \"k8suser\""
    }
}

Usage

Usage of ./opa-openshift:
      --debug.name string                      A name to add as a prefix to log lines. (default "opa-openshift")
      --log.format string                      The log format to use. Options: 'logfmt', 'json'. (default "logfmt")
      --log.level string                       The log filtering level. Options: 'error', 'warn', 'info', 'debug'. (default "info")
      --memcached strings                      One or more Memcached server addresses.
      --memcached.expire int32                 Time after which keys stored in Memcached should expire, given in seconds. (default 3600)
      --memcached.interval int32               The interval at which to update the Memcached DNS, given in seconds; use 0 to disable. (default 10)
      --opa.matcher string                     The label key of the OPA label matcher returned to the requesting client.
      --opa.package string                     The name of the OPA package that opa-openshift should implement, see https://www.openpolicyagent.org/docs/latest/policy-language/#packages.
      --opa.rule string                        The name of the OPA rule for which opa-openshift should provide a result, see https://www.openpolicyagent.org/docs/latest/policy-language/#rules. (default "allow")
      --openshift.kubeconfig string            A path to the kubeconfig against to use for authorizing client requests.
      --openshift.mappings strings             A map of tenantIDs to resource api groups to check to apply a given role to a user, e.g. tenant-a=observatorium.openshift.io
      --tls.cipher-suites string               Comma-separated list of cipher suites for the server. Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants). If omitted, the default Go cipher suites will be used. Note that TLS 1.3 ciphersuites are not configurable.
      --tls.internal.server.ca-file string     File containing the TLS CA against which to verify servers. If no server CA is specified, the client will use the system certificates.
      --tls.internal.server.cert-file string   File containing the default x509 Certificate for internal HTTPS. Leave blank to disable TLS.
      --tls.internal.server.key-file string    File containing the default x509 private key matching --tls.internal.server.cert-file. Leave blank to disable TLS.
      --tls.min-version string                 Minimum TLS version supported. Value must match version names from https://golang.org/pkg/crypto/tls/#pkg-constants. (default "VersionTLS13")
      --tls.server.cert-file string            File containing the default x509 Certificate for HTTPS. Leave blank to disable TLS.
      --tls.server.key-file string             File containing the default x509 private key matching --tls.server.cert-file. Leave blank to disable TLS.
      --web.healthchecks.url string            The URL against which to run healthchecks. (default "http://localhost:8080")
      --web.internal.listen string             The address on which the internal server listens. (default ":8081")
      --web.listen string                      The address on which the public server listens. (default ":8080")