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opaauthorizerequest.go
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/
opaauthorizerequest.go
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package opaauthorizerequest
import (
"encoding/json"
"errors"
"io"
"net/http"
"time"
ext_authz_v3_core "github.com/envoyproxy/go-control-plane/envoy/config/core/v3"
"github.com/zalando/skipper/filters"
"gopkg.in/yaml.v2"
"github.com/zalando/skipper/filters/openpolicyagent"
"github.com/zalando/skipper/filters/openpolicyagent/internal/envoy"
)
const responseHeadersKey = "open-policy-agent:decision-response-headers"
type spec struct {
registry *openpolicyagent.OpenPolicyAgentRegistry
opts []func(*openpolicyagent.OpenPolicyAgentInstanceConfig) error
name string
bodyParsing bool
}
func NewOpaAuthorizeRequestSpec(registry *openpolicyagent.OpenPolicyAgentRegistry, opts ...func(*openpolicyagent.OpenPolicyAgentInstanceConfig) error) filters.Spec {
return &spec{
registry: registry,
opts: opts,
name: filters.OpaAuthorizeRequestName,
}
}
func NewOpaAuthorizeRequestWithBodySpec(registry *openpolicyagent.OpenPolicyAgentRegistry, opts ...func(*openpolicyagent.OpenPolicyAgentInstanceConfig) error) filters.Spec {
return &spec{
registry: registry,
opts: opts,
name: filters.OpaAuthorizeRequestWithBodyName,
bodyParsing: true,
}
}
func (s *spec) Name() string {
return s.name
}
func (s *spec) CreateFilter(args []interface{}) (filters.Filter, error) {
var err error
if len(args) < 1 {
return nil, filters.ErrInvalidFilterParameters
}
if len(args) > 2 {
return nil, filters.ErrInvalidFilterParameters
}
bundleName, ok := args[0].(string)
if !ok {
return nil, filters.ErrInvalidFilterParameters
}
envoyContextExtensions := map[string]string{}
if len(args) > 1 {
_, ok := args[1].(string)
if !ok {
return nil, filters.ErrInvalidFilterParameters
}
err = yaml.Unmarshal([]byte(args[1].(string)), &envoyContextExtensions)
if err != nil {
return nil, err
}
}
configOptions := s.opts
opaConfig, err := openpolicyagent.NewOpenPolicyAgentConfig(configOptions...)
if err != nil {
return nil, err
}
opa, err := s.registry.NewOpenPolicyAgentInstance(bundleName, *opaConfig, s.Name())
if err != nil {
return nil, err
}
return &opaAuthorizeRequestFilter{
opa: opa,
registry: s.registry,
envoyContextExtensions: envoyContextExtensions,
bodyParsing: s.bodyParsing,
}, nil
}
type opaAuthorizeRequestFilter struct {
opa *openpolicyagent.OpenPolicyAgentInstance
registry *openpolicyagent.OpenPolicyAgentRegistry
envoyContextExtensions map[string]string
bodyParsing bool
}
func (f *opaAuthorizeRequestFilter) Request(fc filters.FilterContext) {
req := fc.Request()
span, ctx := f.opa.StartSpanFromFilterContext(fc)
defer span.Finish()
var rawBodyBytes []byte
if f.bodyParsing {
var body io.ReadCloser
var err error
var finalizer func()
body, rawBodyBytes, finalizer, err = f.opa.ExtractHttpBodyOptionally(req)
defer finalizer()
if err != nil {
f.opa.HandleInvalidDecisionError(fc, span, nil, err, !f.opa.EnvoyPluginConfig().DryRun)
return
}
req.Body = body
}
authzreq := envoy.AdaptToExtAuthRequest(req, f.opa.InstanceConfig().GetEnvoyMetadata(), f.envoyContextExtensions, rawBodyBytes)
start := time.Now()
result, err := f.opa.Eval(ctx, authzreq)
fc.Metrics().MeasureSince(f.opa.MetricsKey("eval_time"), start)
var jsonErr *json.SyntaxError
if errors.As(err, &jsonErr) {
f.opa.HandleEvaluationError(fc, span, result, err, !f.opa.EnvoyPluginConfig().DryRun, http.StatusBadRequest)
return
}
if err != nil {
f.opa.HandleInvalidDecisionError(fc, span, result, err, !f.opa.EnvoyPluginConfig().DryRun)
return
}
if f.opa.EnvoyPluginConfig().DryRun {
return
}
allowed, err := result.IsAllowed()
if err != nil {
f.opa.HandleInvalidDecisionError(fc, span, result, err, !f.opa.EnvoyPluginConfig().DryRun)
return
}
if !allowed {
fc.Metrics().IncCounter(f.opa.MetricsKey("decision.deny"))
f.opa.ServeResponse(fc, span, result)
return
}
fc.Metrics().IncCounter(f.opa.MetricsKey("decision.allow"))
headersToRemove, err := result.GetRequestHTTPHeadersToRemove()
if err != nil {
f.opa.HandleInvalidDecisionError(fc, span, result, err, !f.opa.EnvoyPluginConfig().DryRun)
return
}
removeRequestHeaders(fc, headersToRemove)
headers, err := result.GetResponseHTTPHeaders()
if err != nil {
f.opa.HandleInvalidDecisionError(fc, span, result, err, !f.opa.EnvoyPluginConfig().DryRun)
return
}
addRequestHeaders(fc, headers)
if responseHeaders, err := result.GetResponseHTTPHeadersToAdd(); err != nil {
f.opa.HandleInvalidDecisionError(fc, span, result, err, !f.opa.EnvoyPluginConfig().DryRun)
return
} else if len(responseHeaders) > 0 {
fc.StateBag()[responseHeadersKey] = responseHeaders
}
}
func removeRequestHeaders(fc filters.FilterContext, headersToRemove []string) {
for _, header := range headersToRemove {
fc.Request().Header.Del(header)
}
}
func addRequestHeaders(fc filters.FilterContext, headers http.Header) {
for key, values := range headers {
for _, value := range values {
// This is the default behavior from https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/core/v3/base.proto#config-core-v3-headervalueoption
fc.Request().Header.Add(key, value)
}
}
}
func (f *opaAuthorizeRequestFilter) Response(fc filters.FilterContext) {
if headers, ok := fc.StateBag()[responseHeadersKey].([]*ext_authz_v3_core.HeaderValueOption); ok {
addResponseHeaders(fc, headers)
}
}
func addResponseHeaders(fc filters.FilterContext, headersToAdd []*ext_authz_v3_core.HeaderValueOption) {
for _, headerToAdd := range headersToAdd {
header := headerToAdd.GetHeader()
fc.Response().Header.Add(header.GetKey(), header.GetValue())
}
}
func (f *opaAuthorizeRequestFilter) OpenPolicyAgent() *openpolicyagent.OpenPolicyAgentInstance {
return f.opa
}