Open Policy Agent - v0.36.0

This release contains a number of fixes and enhancements.

OpenTelemetry and opa exec

This release adds OpenTelemetry support to OPA. This makes it possible to emit spans to an OpenTelemetry collector via
gRPC on both incoming and outgoing (i.e. http.send) calls in the server. See the updated docs on
monitoring for more information and configuration options
(#1469) authored by @rvalkenaers

This release also adds a new opa exec command for doing one-off evaluations of policy against input similar to
opa eval, but using the full capabilities of the server (config file, plugins, etc). This is particularly useful in
contexts such as CI/CD or when enforcing policy for infrastructure as code, where one might want to run OPA with remote
bundles and decision logs but without having a running server. See the updated docs on
Terraform for an example use case.
(#3525)

Built-in Functions

• Four new functions for working with HMAC (crypto.hmac.md5, crypto.hmac.sha1, crypto.hmac.sha256, and crypto.hmac.sha512) was added (#1740) reported by @jshaw86
• array.reverse(array) and strings.reverse(string) was added for reversing arrays and strings (#3736) authored by @kristiansvalland and @olamiko
• The http.send built-in function now uses a metric for counting inter-query cache hits (#4023) authored by @mirayadav
• An overflow issue with dates very far in the future has been fixed in the time.* built-in functions (#4098) reported by @morgante

Tooling

• A problem with future keyword import of in was fixed for opa fmt (#4111) reported by @keshavprasadms
• An issue with opa fmt when refs contained operators was fixed (authored by @jaspervdj-luminal)
• Fix file renaming check in optimization using opa build (authored by @davidmarne-wf)
• The allow_net capability was added, allowing setting limits on what hosts can be reached in built-ins like http.send and net.lookup_ip_addr (#3665)

Server

• A new credential provider for AWS credential files was added (#2786) reported by @rgueldem
• The new --tls-cert-refresh-period flag can now be provided to opa run. If used with a positive duration, such as "5m" (5 minutes),
  "24h", etc, the server will track the certificate and key files' contents. When their content changes, the certificates will be
  reloaded (#2500) reported by @patoarvizu
• A new v1/status endpoint was added, providing the same data as the status plugin would send to a remote endpoint (#4089)
• The HTTP router of OPA is now exposed to the plugin manager (#2777) authored by @bhoriuchi reported by @mneil
• Calling print now works in decision masking policies
• An unintended switch between long/regular polling on 304 HTTP status was fixed (#3923) authored by @floriangasc
• The error message about prohibited config in the discovery plugin has been improved
• The discovery plugin no longer panics in Trigger() if downloader is nil
• The bundle plugin now ignores service errors for file:// resources
• The bundle plugin file loader was updated to support directories
• A timer to HTTP request was added to the downloader
• The requested_by field in the logging plugin is now optional

Rego

• The error message raised when using - with a number and a set is now more specific (as opposed to the correct usage with two sets, or two numbers) (#1643)
• Fixed an edge case when using print and arrays in unification (#4078)
• Improved performance of some array operations by caching an array's groundness bit (#3679)
• ⚠️ Stricter check of arity in undefined function stage (#4054).
  This change will fail evaluation in some unusual cases where it previously would succeed, but these policies should be very uncommon.

An example policy that previously would succeed but no longer will (wrong arity):

package policy

default p = false
p {
    x := is_blue()
    input.bar[x]
}

is_blue(fruit) = y { # doesn't use fruit
    y := input.foo
}

SDK

• The opa.runtime() built-in is now made available to the SDK (#4050 authored by @oren-zohar and @cmschuetz
• Plugins are now exposed on the SDK object
• The SDK now supports graceful shutdown (#3980) reported by @brianchhun-chime
• print output is now sent to the configured logger

Website and Documentation

• All pages in the docs now have a feedback button (#3664) authored by @alan-ma
• The Kafka docs have been updated to use the new Kafka plugin, and to use the OPA management APIs
• The Terraform tutorial was updated to use opa exec (#3965)
• The docs on Contributing as well as the Vendor Guidelines have been updated
• The term "whitelist" has been replaced by "allowlist" across the docs
• A simple destructuring assignment example was added to the docs
• The docs have been reviewed on the use of assignment, equality and comparison operators, to make sure they follow best practice

CI

• SHA256 checksums of CI builds now published to release directory (#3448) authored by @johanneslarsson reported by @raesene
• golangci-lint upgraded to v1.43.0 (authored by @shuheiktgw)
• The build now creates an executable for darwin/arm64. This should work as expected, but is currently tested in the CI pipeline like the other binaries
• PRs targeting the ecosystem page are now checked for mistakes using Rego policies