[#17] iam: Add converter to native/s3 policy

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

go.mod

@@ -2,10 +2,13 @@ module git.frostfs.info/TrueCloudLab/policy-engine
 
 go 1.20
 
-require github.com/stretchr/testify v1.8.1
+require github.com/stretchr/testify v1.8.4
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/kr/pretty v0.1.0 // indirect
+	github.com/kr/text v0.2.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,17 +1,18 @@
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
-github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

iam/converter.go

@@ -1,6 +1,7 @@
 package iam
 
 import (
+	"errors"
 	"fmt"
 	"strconv"
 	"strings"
@@ -9,9 +10,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
 )
 
-const (
-	RequestOwnerProperty = "Owner"
-)
+const condKeyAWSPrincipalARN = "aws:PrincipalArn"
 
 const (
 	// String condition operators.
@@ -52,168 +51,144 @@ const (
 	CondArnNotLike   string = "ArnNotLike"
 )
 
-func (p Policy) ToChain() (*chain.Chain, error) {
-	if err := p.Validate(GeneralPolicyType); err != nil {
+const (
+	arnIAMPrefix     = "arn:aws:iam::"
+	s3ResourcePrefix = "arn:aws:s3:::"
+	s3ActionPrefix   = "s3:"
+)
+
+var (
+	// ErrInvalidPrincipalFormat occurs when principal has unknown/unsupported format.
+	ErrInvalidPrincipalFormat = errors.New("invalid principal format")
+
+	// ErrInvalidResourceFormat occurs when resource has unknown/unsupported format.
+	ErrInvalidResourceFormat = errors.New("invalid resource format")
+)
+
+type formPrincipalConditionFunc func(string) chain.Condition
+
+type transformConditionFunc func(gr GroupedConditions) (GroupedConditions, error)
+
+func convertToChainConditions(c Conditions, transformer transformConditionFunc) ([]GroupedConditions, error) {
+	conditions, err := convertToChainCondition(c)
+	if err != nil {
 		return nil, err
 	}
 
-	var ch chain.Chain
-
-	for _, statement := range p.Statement {
-		status := chain.AccessDenied
-		if statement.Effect == AllowEffect {
-			status = chain.Allow
+	for i := range conditions {
+		if conditions[i], err = transformer(conditions[i]); err != nil {
+			return nil, fmt.Errorf("transform condition: %w", err)
 		}
+	}
 
-		var principals []string
-		var op chain.ConditionType
-		statementPrincipal, inverted := statement.principal()
-		if _, ok := statementPrincipal[Wildcard]; ok { // this can be true only if 'inverted' false
-			principals = []string{Wildcard}
-			op = chain.CondStringLike
-		} else {
-			for _, principal := range statementPrincipal {
-				principals = append(principals, principal...)
-			}
+	return conditions, nil
+}
 
-			op = chain.CondStringEquals
-			if inverted {
-				op = chain.CondStringNotEquals
-			}
-		}
+type GroupedConditions struct {
+	Conditions []chain.Condition
+	Any        bool
+}
 
-		var conditions []chain.Condition
-		for _, principal := range principals {
-			conditions = append(conditions, chain.Condition{
-				Op:     op,
-				Object: chain.ObjectRequest,
-				Key:    RequestOwnerProperty,
-				Value:  principal,
-			})
-		}
+func convertToChainCondition(c Conditions) ([]GroupedConditions, error) {
+	var grouped []GroupedConditions
 
-		conds, err := statement.Conditions.ToChainCondition()
+	for op, KVs := range c {
+		condType, convertValue, err := getConditionTypeAndConverter(op)
 		if err != nil {
 			return nil, err
 		}
-		conditions = append(conditions, conds...)
-
-		action, actionInverted := statement.action()
-		ruleAction := chain.Actions{Inverted: actionInverted, Names: action}
-
-		resource, resourceInverted := statement.resource()
-		ruleResource := chain.Resources{Inverted: resourceInverted, Names: resource}
-
-		r := chain.Rule{
-			Status:    status,
-			Actions:   ruleAction,
-			Resources: ruleResource,
-			Any:       true,
-			Condition: conditions,
-		}
-		ch.Rules = append(ch.Rules, r)
-	}
-
-	return &ch, nil
-}
-
-//nolint:funlen
-func (c Conditions) ToChainCondition() ([]chain.Condition, error) {
-	var conditions []chain.Condition
-
-	var convertValue convertFunction
-
-	for op, KVs := range c {
-		var condType chain.ConditionType
-
-		switch {
-		case strings.HasPrefix(op, "String"):
-			convertValue = noConvertFunction
-			switch op {
-			case CondStringEquals:
-				condType = chain.CondStringEquals
-			case CondStringNotEquals:
-				condType = chain.CondStringNotEquals
-			case CondStringEqualsIgnoreCase:
-				condType = chain.CondStringEqualsIgnoreCase
-			case CondStringNotEqualsIgnoreCase:
-				condType = chain.CondStringNotEqualsIgnoreCase
-			case CondStringLike:
-				condType = chain.CondStringLike
-			case CondStringNotLike:
-				condType = chain.CondStringNotLike
-			default:
-				return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
-			}
-		case strings.HasPrefix(op, "Arn"):
-			convertValue = noConvertFunction
-			switch op {
-			case CondArnEquals:
-				condType = chain.CondStringEquals
-			case CondArnNotEquals:
-				condType = chain.CondStringNotEquals
-			case CondArnLike:
-				condType = chain.CondStringLike
-			case CondArnNotLike:
-				condType = chain.CondStringNotLike
-			default:
-				return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
-			}
-		case strings.HasPrefix(op, "Numeric"):
-			// TODO
-		case strings.HasPrefix(op, "Date"):
-			convertValue = dateConvertFunction
-			switch op {
-			case CondDateEquals:
-				condType = chain.CondStringEquals
-			case CondDateNotEquals:
-				condType = chain.CondStringNotEquals
-			case CondDateLessThan:
-				condType = chain.CondStringLessThan
-			case CondDateLessThanEquals:
-				condType = chain.CondStringLessThanEquals
-			case CondDateGreaterThan:
-				condType = chain.CondStringGreaterThan
-			case CondDateGreaterThanEquals:
-				condType = chain.CondStringGreaterThanEquals
-			default:
-				return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
-			}
-		case op == CondBool:
-			convertValue = noConvertFunction
-			condType = chain.CondStringEqualsIgnoreCase
-		case op == CondIPAddress:
-			// todo consider using converters
-			//  "203.0.113.0/24" -> "203.0.113.*",
-			//  "2001:DB8:1234:5678::/64" -> "2001:DB8:1234:5678:*"
-			//  or having specific condition type for IP
-			convertValue = noConvertFunction
-			condType = chain.CondStringLike
-		case op == CondNotIPAddress:
-			convertValue = noConvertFunction
-			condType = chain.CondStringNotLike
-		default:
-			return nil, fmt.Errorf("unsupported condition operator: '%s'", op)
-		}
 
 		for key, values := range KVs {
-			for _, val := range values {
+			group := GroupedConditions{
+				Conditions: make([]chain.Condition, len(values)),
+				Any:        len(values) > 1,
+			}
+
+			for i, val := range values {
 				converted, err := convertValue(val)
 				if err != nil {
 					return nil, err
 				}
 
-				conditions = append(conditions, chain.Condition{
+				group.Conditions[i] = chain.Condition{
 					Op:     condType,
 					Object: chain.ObjectRequest,
 					Key:    key,
 					Value:  converted,
-				})
+				}
 			}
+			grouped = append(grouped, group)
 		}
 	}
 
-	return conditions, nil
+	return grouped, nil
+}
+
+func getConditionTypeAndConverter(op string) (chain.ConditionType, convertFunction, error) {
+	switch {
+	case strings.HasPrefix(op, "String"):
+		switch op {
+		case CondStringEquals:
+			return chain.CondStringEquals, noConvertFunction, nil
+		case CondStringNotEquals:
+			return chain.CondStringNotEquals, noConvertFunction, nil
+		case CondStringEqualsIgnoreCase:
+			return chain.CondStringEqualsIgnoreCase, noConvertFunction, nil
+		case CondStringNotEqualsIgnoreCase:
+			return chain.CondStringNotEqualsIgnoreCase, noConvertFunction, nil
+		case CondStringLike:
+			return chain.CondStringLike, noConvertFunction, nil
+		case CondStringNotLike:
+			return chain.CondStringNotLike, noConvertFunction, nil
+		default:
+			return 0, nil, fmt.Errorf("unsupported condition operator: '%s'", op)
+		}
+	case strings.HasPrefix(op, "Arn"):
+		switch op {
+		case CondArnEquals:
+			return chain.CondStringEquals, noConvertFunction, nil
+		case CondArnNotEquals:
+			return chain.CondStringNotEquals, noConvertFunction, nil
+		case CondArnLike:
+			return chain.CondStringLike, noConvertFunction, nil
+		case CondArnNotLike:
+			return chain.CondStringNotLike, noConvertFunction, nil
+		default:
+			return 0, nil, fmt.Errorf("unsupported condition operator: '%s'", op)
+		}
+	case strings.HasPrefix(op, "Numeric"):
+		// TODO
+		return 0, nil, fmt.Errorf("currently nummeric conditions unsupported: '%s'", op)
+	case strings.HasPrefix(op, "Date"):
+		switch op {
+		case CondDateEquals:
+			return chain.CondStringEquals, dateConvertFunction, nil
+		case CondDateNotEquals:
+			return chain.CondStringNotEquals, dateConvertFunction, nil
+		case CondDateLessThan:
+			return chain.CondStringLessThan, dateConvertFunction, nil
+		case CondDateLessThanEquals:
+			return chain.CondStringLessThanEquals, dateConvertFunction, nil
+		case CondDateGreaterThan:
+			return chain.CondStringGreaterThan, dateConvertFunction, nil
+		case CondDateGreaterThanEquals:
+			return chain.CondStringGreaterThanEquals, dateConvertFunction, nil
+		default:
+			return 0, nil, fmt.Errorf("unsupported condition operator: '%s'", op)
+		}
+	case op == CondBool:
+		return chain.CondStringEqualsIgnoreCase, noConvertFunction, nil
+	case op == CondIPAddress:
+		// todo consider using converters
+		//  "203.0.113.0/24" -> "203.0.113.*",
+		//  "2001:DB8:1234:5678::/64" -> "2001:DB8:1234:5678:*"
+		//  or having specific condition type for IP
+		return chain.CondStringLike, noConvertFunction, nil
+	case op == CondNotIPAddress:
+		return chain.CondStringNotLike, noConvertFunction, nil
+	default:
+		return 0, nil, fmt.Errorf("unsupported condition operator: '%s'", op)
+	}
 }
 
 type convertFunction func(string) (string, error)
@@ -234,3 +209,89 @@ func dateConvertFunction(val string) (string, error) {
 
 	return strconv.FormatInt(parsed.UTC().Unix(), 10), nil
 }
+
+func parsePrincipalAsIAMUser(principal string) (account string, user string, err error) {
+	if !strings.HasPrefix(principal, arnIAMPrefix) {
+		return "", "", ErrInvalidPrincipalFormat
+	}
+
+	// iam arn format arn:aws:iam::<account>:user/<user-name-with-path>
+	iamResource := strings.TrimPrefix(principal, arnIAMPrefix)
+	sepIndex := strings.Index(iamResource, ":user/")
+	if sepIndex < 0 {
+		return "", "", ErrInvalidPrincipalFormat
+	}
+
+	account = iamResource[:sepIndex]
+	user = iamResource[sepIndex+6:]
+	if len(user) == 0 {
+		return "", "", ErrInvalidPrincipalFormat
+	}
+
+	userNameIndex := strings.LastIndexByte(user, '/')
+	if userNameIndex > -1 {
+		user = user[userNameIndex+1:]
+		if len(user) == 0 {
+			return "", "", ErrInvalidPrincipalFormat
+		}
+	}
+
+	return account, user, nil
+}
+
+func parseResourceAsS3ARN(resource string) (bucket string, object string, err error) {
+	if !strings.HasPrefix(resource, s3ResourcePrefix) {
+		return "", "", ErrInvalidResourceFormat
+	}
+
+	// iam arn format arn:aws:s3:::<bucket-name>/<object-name>
+	s3Resource := strings.TrimPrefix(resource, s3ResourcePrefix)
+	sepIndex := strings.Index(s3Resource, "/")
+	if sepIndex < 0 {
+		return s3Resource, Wildcard, nil
+	}
+
+	bucket = s3Resource[:sepIndex]
+	object = s3Resource[sepIndex+1:]
+	if len(object) == 0 {
+		return bucket, Wildcard, nil
+	}
+
+	if bucket == Wildcard && object != Wildcard {
+		return "", "", ErrInvalidResourceFormat
+	}
+
+	return bucket, object, nil
+}
+
+func splitGroupedConditions(groupedConditions []GroupedConditions) [][]chain.Condition {
+	var orConditions []chain.Condition
+	commonConditions := make([]chain.Condition, 0, len(groupedConditions))
+	for _, grouped := range groupedConditions {
+		if grouped.Any {
+			orConditions = append(orConditions, grouped.Conditions...)
+		} else {
+			commonConditions = append(commonConditions, grouped.Conditions...)
+		}
+	}
+
+	if len(orConditions) == 0 {
+		return [][]chain.Condition{commonConditions}
+	}
+
+	res := make([][]chain.Condition, len(orConditions))
+	for i, condition := range orConditions {
+		res[i] = append([]chain.Condition{condition}, commonConditions...)
+	}
+
+	return res
+}
+
+func formStatus(statement Statement) chain.Status {
+	status := chain.AccessDenied
+	if statement.Effect == AllowEffect {
+		status = chain.Allow
+	}
+
+	return status
+}

iam/converter_native.go

@@ -0,0 +1,241 @@
+package iam
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
+	"git.frostfs.info/TrueCloudLab/policy-engine/schema/native"
+)
+
+const PropertyKeyFilePath = "FilePath"
+
+// ErrActionsNotApplicable occurs when failed to convert any actions.
+var ErrActionsNotApplicable = errors.New("actions not applicable")
+
+var actionToOpMap = map[string][]string{
+	supportedS3ActionDeleteObject: {native.MethodDeleteObject},
+	supportedS3ActionGetObject:    {native.MethodGetObject, native.MethodHeadObject, native.MethodSearchObject, native.MethodRangeObject, native.MethodHashObject},
+	supportedS3ActionHeadObject:   {native.MethodHeadObject, native.MethodSearchObject, native.MethodRangeObject, native.MethodHashObject},
+	supportedS3ActionPutObject:    {native.MethodPutObject},
+	supportedS3ActionListBucket:   {native.MethodGetObject, native.MethodHeadObject, native.MethodSearchObject, native.MethodRangeObject, native.MethodHashObject},
+}
+
+const (
+	supportedS3ActionDeleteObject = "DeleteObject"
+	supportedS3ActionGetObject    = "GetObject"
+	supportedS3ActionHeadObject   = "HeadObject"
+	supportedS3ActionPutObject    = "PutObject"
+	supportedS3ActionListBucket   = "ListBucket"
+)
+
+type NativeResolver interface {
+	GetUserKey(account, name string) (string, error)
+	GetBucketCID(bucket string) (string, error)
+}
+
+func ConvertToNativeChain(p Policy, resolver NativeResolver) (*chain.Chain, error) {
+	if err := p.Validate(ResourceBasedPolicyType); err != nil {
+		return nil, err
+	}
+
+	var engineChain chain.Chain
+
+	for _, statement := range p.Statement {
+		status := formStatus(statement)
+
+		action, actionInverted := statement.action()
+		ruleAction := chain.Actions{Inverted: actionInverted, Names: formNativeActionNames(action)}
+		if len(ruleAction.Names) == 0 {
+			continue
+		}
+
+		resource, resourceInverted := statement.resource()
+		groupedResources, err := formNativeResourceNamesAndConditions(resource, resolver)
+		if err != nil {
+			return nil, err
+		}
+
+		groupedConditions, err := convertToNativeChainCondition(statement.Conditions, resolver)
+		if err != nil {
+			return nil, err
+		}
+		splitConditions := splitGroupedConditions(groupedConditions)
+
+		principals, principalCondFn, err := getNativePrincipalsAndConditionFunc(statement, resolver)
+		if err != nil {
+			return nil, err
+		}
+
+		for _, groupedResource := range groupedResources {
+			for _, principal := range principals {
+				for _, conditions := range splitConditions {
+					ruleConditions := append([]chain.Condition{principalCondFn(principal)}, groupedResource.Conditions...)
+
+					r := chain.Rule{
+						Status:  status,
+						Actions: ruleAction,
+						Resources: chain.Resources{
+							Inverted: resourceInverted,
+							Names:    groupedResource.Names,
+						},
+						Condition: append(ruleConditions, conditions...),
+					}
+					engineChain.Rules = append(engineChain.Rules, r)
+				}
+			}
+		}
+	}
+
+	if len(engineChain.Rules) == 0 {
+		return nil, ErrActionsNotApplicable
+	}
+
+	return &engineChain, nil
+}
+
+func getNativePrincipalsAndConditionFunc(statement Statement, resolver NativeResolver) ([]string, formPrincipalConditionFunc, error) {
+	var principals []string
+	var op chain.ConditionType
+	statementPrincipal, inverted := statement.principal()
+	if _, ok := statementPrincipal[Wildcard]; ok { // this can be true only if 'inverted' false
+		principals = []string{Wildcard}
+		op = chain.CondStringLike
+	} else {
+		for principalType, principal := range statementPrincipal {
+			if principalType != AWSPrincipalType {
+				return nil, nil, fmt.Errorf("unsupported principal type '%s'", principalType)
+			}
+			parsedPrincipal, err := formNativePrincipal(principal, resolver)
+			if err != nil {
+				return nil, nil, fmt.Errorf("parse principal: %w", err)
+			}
+			principals = append(principals, parsedPrincipal...)
+		}
+
+		op = chain.CondStringEquals
+		if inverted {
+			op = chain.CondStringNotEquals
+		}
+	}
+
+	return principals, func(principal string) chain.Condition {
+		return chain.Condition{
+			Op:     op,
+			Object: chain.ObjectRequest,
+			Key:    native.PropertyKeyActorPublicKey,
+			Value:  principal,
+		}
+	}, nil
+}
+
+func convertToNativeChainCondition(c Conditions, resolver NativeResolver) ([]GroupedConditions, error) {
+	return convertToChainConditions(c, func(gr GroupedConditions) (GroupedConditions, error) {
+		for i := range gr.Conditions {
+			if gr.Conditions[i].Key == condKeyAWSPrincipalARN {
+				gr.Conditions[i].Key = native.PropertyKeyActorPublicKey
+				val, err := formPrincipalKey(gr.Conditions[i].Value, resolver)
+				if err != nil {
+					return GroupedConditions{}, err
+				}
+				gr.Conditions[i].Value = val
+			}
+		}
+
+		return gr, nil
+	})
+}
+
+type GroupedResources struct {
+	Names      []string
+	Conditions []chain.Condition
+}
+
+func formNativeResourceNamesAndConditions(names []string, resolver NativeResolver) ([]GroupedResources, error) {
+	res := make([]GroupedResources, 0, len(names))
+
+	var combined []string
+
+	for i := range names {
+		bkt, obj, err := parseResourceAsS3ARN(names[i])
+		if err != nil {
+			return nil, err
+		}
+
+		if bkt == Wildcard {
+			res = res[:0]
+			return append(res, GroupedResources{Names: []string{native.ResourceFormatAllObjects}}), nil
+		}
+
+		cnrID, err := resolver.GetBucketCID(bkt)
+		if err != nil {
+			return nil, err
+		}
+		resource := fmt.Sprintf(native.ResourceFormatRootContainerObjects, cnrID)
+
+		if obj == Wildcard {
+			combined = append(combined, resource)
+			continue
+		}
+
+		res = append(res, GroupedResources{
+			Names: []string{resource},
+			Conditions: []chain.Condition{
+				{
+					Op:     chain.CondStringLike,
+					Object: chain.ObjectResource,
+					Key:    PropertyKeyFilePath,
+					Value:  obj,
+				},
+			},
+		})
+	}
+
+	if len(combined) != 0 {
+		res = append(res, GroupedResources{Names: combined})
+	}
+
+	return res, nil
+}
+
+func formNativePrincipal(principal []string, resolver NativeResolver) ([]string, error) {
+	res := make([]string, len(principal))
+
+	var err error
+	for i := range principal {
+		if res[i], err = formPrincipalKey(principal[i], resolver); err != nil {
+			return nil, err
+		}
+	}
+
+	return res, nil
+}
+
+func formPrincipalKey(principal string, resolver NativeResolver) (string, error) {
+	account, user, err := parsePrincipalAsIAMUser(principal)
+	if err != nil {
+		return "", err
+	}
+
+	key, err := resolver.GetUserKey(account, user)
+	if err != nil {
+		return "", fmt.Errorf("get user key: %w", err)
+	}
+
+	return key, nil
+}
+
+func formNativeActionNames(names []string) []string {
+	res := make([]string, 0, len(names))
+
+	for i := range names {
+		trimmed := strings.TrimPrefix(names[i], s3ActionPrefix)
+		if trimmed == Wildcard {
+			return []string{Wildcard}
+		}
+		res = append(res, actionToOpMap[trimmed]...)
+	}
+
+	return res
+}

iam/converter_s3.go

@@ -0,0 +1,153 @@
+package iam
+
+import (
+	"fmt"
+	"strings"
+
+	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
+	"git.frostfs.info/TrueCloudLab/policy-engine/schema/s3"
+)
+
+type S3Resolver interface {
+	GetUserAddress(account, user string) (string, error)
+}
+
+func ConvertToS3Chain(p Policy, resolver S3Resolver) (*chain.Chain, error) {
+	if err := p.Validate(ResourceBasedPolicyType); err != nil {
+		return nil, err
+	}
+
+	var engineChain chain.Chain
+
+	for _, statement := range p.Statement {
+		status := formStatus(statement)
+
+		action, actionInverted := statement.action()
+		ruleAction := chain.Actions{Inverted: actionInverted, Names: formS3ActionNames(action)}
+
+		resource, resourceInverted := statement.resource()
+		ruleResource := chain.Resources{Inverted: resourceInverted, Names: formS3ResourceNamesAndConditions(resource)}
+
+		groupedConditions, err := convertToS3ChainCondition(statement.Conditions, resolver)
+		if err != nil {
+			return nil, err
+		}
+		splitConditions := splitGroupedConditions(groupedConditions)
+
+		principals, principalCondFn, err := getS3PrincipalsAndConditionFunc(statement, resolver)
+		if err != nil {
+			return nil, err
+		}
+
+		for _, principal := range principals {
+			for _, conditions := range splitConditions {
+				r := chain.Rule{
+					Status:    status,
+					Actions:   ruleAction,
+					Resources: ruleResource,
+					Condition: append([]chain.Condition{principalCondFn(principal)}, conditions...),
+				}
+				engineChain.Rules = append(engineChain.Rules, r)
+			}
+		}
+	}
+
+	return &engineChain, nil
+}
+
+func getS3PrincipalsAndConditionFunc(statement Statement, resolver S3Resolver) ([]string, formPrincipalConditionFunc, error) {
+	var principals []string
+	var op chain.ConditionType
+	statementPrincipal, inverted := statement.principal()
+	if _, ok := statementPrincipal[Wildcard]; ok { // this can be true only if 'inverted' false
+		principals = []string{Wildcard}
+		op = chain.CondStringLike
+	} else {
+		for principalType, principal := range statementPrincipal {
+			if principalType != AWSPrincipalType {
+				return nil, nil, fmt.Errorf("unsupported principal type '%s'", principalType)
+			}
+			parsedPrincipal, err := formS3Principal(principal, resolver)
+			if err != nil {
+				return nil, nil, fmt.Errorf("parse principal: %w", err)
+			}
+			principals = append(principals, parsedPrincipal...)
+		}
+
+		op = chain.CondStringEquals
+		if inverted {
+			op = chain.CondStringNotEquals
+		}
+	}
+
+	return principals, func(principal string) chain.Condition {
+		return chain.Condition{
+			Op:     op,
+			Object: chain.ObjectRequest,
+			Key:    s3.PropertyKeyOwner,
+			Value:  principal,
+		}
+	}, nil
+}
+
+func convertToS3ChainCondition(c Conditions, resolver S3Resolver) ([]GroupedConditions, error) {
+	return convertToChainConditions(c, func(gr GroupedConditions) (GroupedConditions, error) {
+		for i := range gr.Conditions {
+			if gr.Conditions[i].Key == condKeyAWSPrincipalARN {
+				gr.Conditions[i].Key = s3.PropertyKeyOwner
+				val, err := formPrincipalOwner(gr.Conditions[i].Value, resolver)
+				if err != nil {
+					return GroupedConditions{}, err
+				}
+				gr.Conditions[i].Value = val
+			}
+		}
+
+		return gr, nil
+	})
+}
+
+func formS3Principal(principal []string, resolver S3Resolver) ([]string, error) {
+	res := make([]string, len(principal))
+
+	var err error
+	for i := range principal {
+		if res[i], err = formPrincipalOwner(principal[i], resolver); err != nil {
+			return nil, err
+		}
+	}
+
+	return res, nil
+}
+
+func formPrincipalOwner(principal string, resolver S3Resolver) (string, error) {
+	account, user, err := parsePrincipalAsIAMUser(principal)
+	if err != nil {
+		return "", err
+	}
+
+	address, err := resolver.GetUserAddress(account, user)
+	if err != nil {
+		return "", fmt.Errorf("get user address: %w", err)
+	}
+
+	return address, nil
+}
+
+func formS3ResourceNamesAndConditions(names []string) []string {
+	res := make([]string, len(names))
+	for i := range names {
+		res[i] = strings.TrimPrefix(names[i], s3ResourcePrefix)
+	}
+
+	return res
+}
+
+func formS3ActionNames(names []string) []string {
+	res := make([]string, len(names))
+	for i := range names {
+		res[i] = strings.TrimPrefix(names[i], s3ActionPrefix)
+	}
+
+	return res
+}

iam/policy.go

@@ -222,6 +222,10 @@ func (p Policy) Validate(typ PolicyType) error {
 }
 
 func (p Policy) validate() error {
+	if len(p.Statement) == 0 {
+		return errors.New("'Statement' is missing")
+	}
+
 	for _, statement := range p.Statement {
 		if !statement.Effect.IsValid() {
 			return fmt.Errorf("unknown effect: '%s'", statement.Effect)

iam/policy_test.go

@@ -320,6 +320,12 @@ func TestValidatePolicies(t *testing.T) {
 			typ:     GeneralPolicyType,
 			isValid: false,
 		},
+		{
+			name:    "missing statement block",
+			policy:  Policy{},
+			typ:     GeneralPolicyType,
+			isValid: false,
+		},
 		{
 			name: "identity based valid",
 			policy: Policy{

schema/s3/consts.go

@@ -0,0 +1,9 @@
+package s3
+
+const (
+	PropertyKeyOwner = "Owner"
+
+	PropertyKeyDelimiter = "s3:delimiter"
+	PropertyKeyPrefix    = "s3:prefix"
+	PropertyKeyVersionID = "s3:VersionId"
+)