authorization: translate SDK policy to Envoy RBAC proto (#4523)

* Translates SDK authorization policy to Envoy RBAC proto.

authz/rbac_translator.go

@@ -0,0 +1,301 @@
+/*
+ * Copyright 2021 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package authz exposes methods to manage authorization within gRPC.
+//
+// Experimental
+//
+// Notice: This package is EXPERIMENTAL and may be changed or removed
+// in a later release.
+package authz
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	v3rbacpb "github.com/envoyproxy/go-control-plane/envoy/config/rbac/v3"
+	v3routepb "github.com/envoyproxy/go-control-plane/envoy/config/route/v3"
+	v3matcherpb "github.com/envoyproxy/go-control-plane/envoy/type/matcher/v3"
+)
+
+type header struct {
+	Key    string
+	Values []string
+}
+
+type peer struct {
+	Principals []string
+}
+
+type request struct {
+	Paths   []string
+	Headers []header
+}
+
+type rule struct {
+	Name    string
+	Source  peer
+	Request request
+}
+
+// Represents the SDK authorization policy provided by user.
+type authorizationPolicy struct {
+	Name       string
+	DenyRules  []rule `json:"deny_rules"`
+	AllowRules []rule `json:"allow_rules"`
+}
+
+func principalOr(principals []*v3rbacpb.Principal) *v3rbacpb.Principal {
+	return &v3rbacpb.Principal{
+		Identifier: &v3rbacpb.Principal_OrIds{
+			OrIds: &v3rbacpb.Principal_Set{
+				Ids: principals,
+			},
+		},
+	}
+}
+
+func permissionOr(permission []*v3rbacpb.Permission) *v3rbacpb.Permission {
+	return &v3rbacpb.Permission{
+		Rule: &v3rbacpb.Permission_OrRules{
+			OrRules: &v3rbacpb.Permission_Set{
+				Rules: permission,
+			},
+		},
+	}
+}
+
+func permissionAnd(permission []*v3rbacpb.Permission) *v3rbacpb.Permission {
+	return &v3rbacpb.Permission{
+		Rule: &v3rbacpb.Permission_AndRules{
+			AndRules: &v3rbacpb.Permission_Set{
+				Rules: permission,
+			},
+		},
+	}
+}
+
+func getStringMatcher(value string) *v3matcherpb.StringMatcher {
+	switch {
+	case value == "*":
+		return &v3matcherpb.StringMatcher{
+			MatchPattern: &v3matcherpb.StringMatcher_Prefix{},
+		}
+	case strings.HasSuffix(value, "*"):
+		prefix := strings.TrimSuffix(value, "*")
+		return &v3matcherpb.StringMatcher{
+			MatchPattern: &v3matcherpb.StringMatcher_Prefix{Prefix: prefix},
+		}
+	case strings.HasPrefix(value, "*"):
+		suffix := strings.TrimPrefix(value, "*")
+		return &v3matcherpb.StringMatcher{
+			MatchPattern: &v3matcherpb.StringMatcher_Suffix{Suffix: suffix},
+		}
+	default:
+		return &v3matcherpb.StringMatcher{
+			MatchPattern: &v3matcherpb.StringMatcher_Exact{Exact: value},
+		}
+	}
+}
+
+func getHeaderMatcher(key, value string) *v3routepb.HeaderMatcher {
+	switch {
+	case value == "*":
+		return &v3routepb.HeaderMatcher{
+			Name:                 key,
+			HeaderMatchSpecifier: &v3routepb.HeaderMatcher_PrefixMatch{},
+		}
+	case strings.HasSuffix(value, "*"):
+		prefix := strings.TrimSuffix(value, "*")
+		return &v3routepb.HeaderMatcher{
+			Name:                 key,
+			HeaderMatchSpecifier: &v3routepb.HeaderMatcher_PrefixMatch{PrefixMatch: prefix},
+		}
+	case strings.HasPrefix(value, "*"):
+		suffix := strings.TrimPrefix(value, "*")
+		return &v3routepb.HeaderMatcher{
+			Name:                 key,
+			HeaderMatchSpecifier: &v3routepb.HeaderMatcher_SuffixMatch{SuffixMatch: suffix},
+		}
+	default:
+		return &v3routepb.HeaderMatcher{
+			Name:                 key,
+			HeaderMatchSpecifier: &v3routepb.HeaderMatcher_ExactMatch{ExactMatch: value},
+		}
+	}
+}
+
+func parsePrincipalNames(principalNames []string) []*v3rbacpb.Principal {
+	var ps []*v3rbacpb.Principal
+	for _, principalName := range principalNames {
+		newPrincipalName := &v3rbacpb.Principal{
+			Identifier: &v3rbacpb.Principal_Authenticated_{
+				Authenticated: &v3rbacpb.Principal_Authenticated{
+					PrincipalName: getStringMatcher(principalName),
+				},
+			}}
+		ps = append(ps, newPrincipalName)
+	}
+	return ps
+}
+
+func parsePeer(source peer) (*v3rbacpb.Principal, error) {
+	if len(source.Principals) > 0 {
+		return principalOr(parsePrincipalNames(source.Principals)), nil
+	}
+	return &v3rbacpb.Principal{
+		Identifier: &v3rbacpb.Principal_Any{
+			Any: true,
+		},
+	}, nil
+}
+
+func parsePaths(paths []string) []*v3rbacpb.Permission {
+	var ps []*v3rbacpb.Permission
+	for _, path := range paths {
+		newPath := &v3rbacpb.Permission{
+			Rule: &v3rbacpb.Permission_UrlPath{
+				UrlPath: &v3matcherpb.PathMatcher{
+					Rule: &v3matcherpb.PathMatcher_Path{Path: getStringMatcher(path)}}}}
+		ps = append(ps, newPath)
+	}
+	return ps
+}
+
+func parseHeaderValues(key string, values []string) []*v3rbacpb.Permission {
+	var vs []*v3rbacpb.Permission
+	for _, value := range values {
+		newHeader := &v3rbacpb.Permission{
+			Rule: &v3rbacpb.Permission_Header{
+				Header: getHeaderMatcher(key, value)}}
+		vs = append(vs, newHeader)
+	}
+	return vs
+}
+
+var unsupportedHeaders = map[string]bool{
+	"host":                true,
+	"connection":          true,
+	"keep-alive":          true,
+	"proxy-authenticate":  true,
+	"proxy-authorization": true,
+	"te":                  true,
+	"trailer":             true,
+	"transfer-encoding":   true,
+	"upgrade":             true,
+}
+
+func unsupportedHeader(key string) bool {
+	return key[0] == ':' || strings.HasPrefix(key, "grpc-") || unsupportedHeaders[key]
+}
+
+func parseHeaders(headers []header) ([]*v3rbacpb.Permission, error) {
+	var hs []*v3rbacpb.Permission
+	for i, header := range headers {
+		if header.Key == "" {
+			return nil, fmt.Errorf(`"headers" %d: "key" is not present`, i)
+		}
+		header.Key = strings.ToLower(header.Key)
+		if unsupportedHeader(header.Key) {
+			return nil, fmt.Errorf(`"headers" %d: unsupported "key" %s`, i, header.Key)
+		}
+		if len(header.Values) == 0 {
+			return nil, fmt.Errorf(`"headers" %d: "values" is not present`, i)
+		}
+		values := parseHeaderValues(header.Key, header.Values)
+		hs = append(hs, permissionOr(values))
+	}
+	return hs, nil
+}
+
+func parseRequest(request request) (*v3rbacpb.Permission, error) {
+	var and []*v3rbacpb.Permission
+	if len(request.Paths) > 0 {
+		and = append(and, permissionOr(parsePaths(request.Paths)))
+	}
+	if len(request.Headers) > 0 {
+		headers, err := parseHeaders(request.Headers)
+		if err != nil {
+			return nil, err
+		}
+		and = append(and, permissionAnd(headers))
+	}
+	if len(and) > 0 {
+		return permissionAnd(and), nil
+	}
+	return &v3rbacpb.Permission{
+		Rule: &v3rbacpb.Permission_Any{
+			Any: true,
+		},
+	}, nil
+}
+
+func parseRules(rules []rule, prefixName string) (map[string]*v3rbacpb.Policy, error) {
+	policies := make(map[string]*v3rbacpb.Policy)
+	for i, rule := range rules {
+		if rule.Name == "" {
+			return policies, fmt.Errorf(`%d: "name" is not present`, i)
+		}
+		principal, err := parsePeer(rule.Source)
+		if err != nil {
+			return nil, fmt.Errorf("%d: %v", i, err)
+		}
+		permission, err := parseRequest(rule.Request)
+		if err != nil {
+			return nil, fmt.Errorf("%d: %v", i, err)
+		}
+		policyName := prefixName + "_" + rule.Name
+		policies[policyName] = &v3rbacpb.Policy{
+			Principals:  []*v3rbacpb.Principal{principal},
+			Permissions: []*v3rbacpb.Permission{permission},
+		}
+	}
+	return policies, nil
+}
+
+// translatePolicy translates SDK authorization policy in JSON format to two
+// Envoy RBAC polices (deny and allow policy). If the policy cannot be parsed
+// or is invalid, an error will be returned.
+func translatePolicy(policyStr string) (*v3rbacpb.RBAC, *v3rbacpb.RBAC, error) {
+	var policy authorizationPolicy
+	if err := json.Unmarshal([]byte(policyStr), &policy); err != nil {
+		return nil, nil, fmt.Errorf("failed to unmarshal policy: %v", err)
+	}
+	if policy.Name == "" {
+		return nil, nil, fmt.Errorf(`"name" is not present`)
+	}
+	if len(policy.AllowRules) == 0 {
+		return nil, nil, fmt.Errorf(`"allow_rules" is not present`)
+	}
+	allowPolicies, err := parseRules(policy.AllowRules, policy.Name)
+	if err != nil {
+		return nil, nil, fmt.Errorf(`"allow_rules" %v`, err)
+	}
+	allowRBAC := &v3rbacpb.RBAC{Action: v3rbacpb.RBAC_ALLOW, Policies: allowPolicies}
+	var denyRBAC *v3rbacpb.RBAC
+	if len(policy.DenyRules) > 0 {
+		denyPolicies, err := parseRules(policy.DenyRules, policy.Name)
+		if err != nil {
+			return nil, nil, fmt.Errorf(`"deny_rules" %v`, err)
+		}
+		denyRBAC = &v3rbacpb.RBAC{
+			Action:   v3rbacpb.RBAC_DENY,
+			Policies: denyPolicies,
+		}
+	}
+	return denyRBAC, allowRBAC, nil
+}