[#XX] Add IAM policy unmarshaler

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

chain.go

@@ -0,0 +1,193 @@
+package policyengine
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+	"strings"
+)
+
+// Engine ...
+type Engine interface {
+	// IsAllowed returns status for the operation after all checks.
+	// The second return value signifies whether a matching rule was found.
+	IsAllowed(name Name, namespace string, r Request) (Status, bool)
+}
+
+type Chain struct {
+	Rules []Rule
+}
+
+func init() {
+	// FIXME #1 (@fyrchik): Introduce more optimal serialization format.
+	gob.Register(Chain{})
+}
+
+func (c *Chain) Bytes() []byte {
+	b := bytes.NewBuffer(nil)
+	e := gob.NewEncoder(b)
+	if err := e.Encode(c); err != nil {
+		panic(err)
+	}
+	return b.Bytes()
+}
+
+func (c *Chain) DecodeBytes(b []byte) error {
+	r := bytes.NewReader(b)
+	d := gob.NewDecoder(r)
+	return d.Decode(c)
+}
+
+type Rule struct {
+	Status Status
+	// Actions the operation is applied to.
+	Action []string
+	// List of the resources the operation is applied to.
+	Resource []string
+	// True iff individual conditions must be combined with the logical OR.
+	// By default AND is used, so _each_ condition must pass.
+	Any       bool
+	Condition []Condition
+}
+
+type Condition struct {
+	Op     ConditionType
+	Object ObjectType
+	Key    string
+	Value  string
+}
+
+type ObjectType byte
+
+const (
+	ObjectResource ObjectType = iota
+	ObjectRequest
+	ObjectActor
+)
+
+// TODO @fyrchik: replace string with int-like type.
+type ConditionType string
+
+// TODO @fyrchik: reduce the number of conditions.
+// Everything from here should be expressable, but we do not need them all.
+// https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_condition_operators.html
+const (
+	// String condition operators.
+	CondStringEquals              ConditionType = "StringEquals"
+	CondStringNotEquals           ConditionType = "StringNotEquals"
+	CondStringEqualsIgnoreCase    ConditionType = "StringEqualsIgnoreCase"
+	CondStringNotEqualsIgnoreCase ConditionType = "StringNotEqualsIgnoreCase"
+	CondStringLike                ConditionType = "StringLike"
+	CondStringNotLike             ConditionType = "StringNotLike"
+
+	// Numeric condition operators.
+	CondNumericEquals            ConditionType = "NumericEquals"
+	CondNumericNotEquals         ConditionType = "NumericNotEquals"
+	CondNumericLessThan          ConditionType = "NumericLessThan"
+	CondNumericLessThanEquals    ConditionType = "NumericLessThanEquals"
+	CondNumericGreaterThan       ConditionType = "NumericGreaterThan"
+	CondNumericGreaterThanEquals ConditionType = "NumericGreaterThanEquals"
+
+	// Date condition operators.
+	CondDateEquals            ConditionType = "DateEquals"
+	CondDateNotEquals         ConditionType = "DateNotEquals"
+	CondDateLessThan          ConditionType = "DateLessThan"
+	CondDateLessThanEquals    ConditionType = "DateLessThanEquals"
+	CondDateGreaterThan       ConditionType = "DateGreaterThan"
+	CondDateGreaterThanEquals ConditionType = "DateGreaterThanEquals"
+
+	// Bolean condition operators.
+	CondBool ConditionType = "Bool"
+
+	// IP address condition operators.
+	CondIPAddress    ConditionType = "IpAddress"
+	CondNotIPAddress ConditionType = "NotIpAddress"
+
+	// ARN condition operators.
+	CondArnEquals    ConditionType = "ArnEquals"
+	CondArnLike      ConditionType = "ArnLike"
+	CondArnNotEquals ConditionType = "ArnNotEquals"
+	CondArnNotLike   ConditionType = "ArnNotLike"
+)
+
+func (c *Condition) Match(obj Request) bool {
+	var val string
+	switch c.Object {
+	case ObjectResource:
+		val = obj.Resource().Property(c.Key)
+	case ObjectRequest:
+		val = obj.Property(c.Key)
+	default:
+		return false
+	}
+
+	switch c.Op {
+	default:
+		panic(fmt.Sprintf("unimplemented: %s", c.Op))
+	case CondStringEquals:
+		return val == c.Value
+	case CondStringNotEquals:
+		return val != c.Value
+	case CondStringEqualsIgnoreCase:
+		return strings.EqualFold(val, c.Value)
+	case CondStringNotEqualsIgnoreCase:
+		return !strings.EqualFold(val, c.Value)
+	case CondStringLike:
+		return globMatch(val, c.Value)
+	case CondStringNotLike:
+		return !globMatch(val, c.Value)
+	}
+}
+
+func (r *Rule) Match(req Request) (status Status, matched bool) {
+	found := len(r.Resource) == 0
+	for i := range r.Resource {
+		if globMatch(req.Resource().Name(), r.Resource[i]) {
+			found = true
+			break
+		}
+	}
+	if !found {
+		return NoRuleFound, false
+	}
+	for i := range r.Action {
+		if globMatch(r.Action[i], req.Operation()) {
+			return r.matchCondition(req)
+		}
+	}
+	return NoRuleFound, false
+}
+
+func (r *Rule) matchCondition(obj Request) (status Status, matched bool) {
+	if r.Any {
+		return r.matchAny(obj)
+	}
+	return r.matchAll(obj)
+}
+func (r *Rule) matchAny(obj Request) (status Status, matched bool) {
+	for i := range r.Condition {
+		if r.Condition[i].Match(obj) {
+
+			return r.Status, true
+		}
+	}
+	return NoRuleFound, false
+}
+func (r *Rule) matchAll(obj Request) (status Status, matched bool) {
+	for i := range r.Condition {
+		if !r.Condition[i].Match(obj) {
+			return NoRuleFound, false
+		}
+	}
+	return r.Status, true
+}
+
+func (c *Chain) Match(req Request) (status Status, matched bool) {
+	for i := range c.Rules {
+		status, matched := c.Rules[i].Match(req)
+		if matched {
+			return status, true
+		}
+	}
+	return NoRuleFound, false
+}

chain_names.go

@@ -0,0 +1,10 @@
+package policyengine
+
+// Name represents the place in the request lifecycle where policy is applied.
+type Name string
+
+const (
+	// Ingress represents chains applied when crossing user/storage network boundary.
+	// It is not applied when talking between nodes.
+	Ingress Name = "ingress"
+)

chain_test.go

@@ -0,0 +1,33 @@
+package policyengine
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestEncodeDecode(t *testing.T) {
+	expected := Chain{
+		Rules: []Rule{
+			{
+				Status: Allow,
+				Action: []string{
+					"native::PutObject",
+				},
+				Resource: []string{"*"},
+				Condition: []Condition{
+					{
+						Op:    CondStringEquals,
+						Key:   "Name",
+						Value: "NNS",
+					},
+				},
+			},
+		},
+	}
+	data := expected.Bytes()
+
+	var actual Chain
+	require.NoError(t, actual.DecodeBytes(data))
+	require.Equal(t, expected, actual)
+}

error.go

@@ -0,0 +1,35 @@
+package policyengine
+
+import "fmt"
+
+// Status is the status for policy application
+type Status byte
+
+const (
+	Allow Status = iota
+	NoRuleFound
+	AccessDenied
+	QuotaLimitReached
+	last
+)
+
+// Valid returns true if the status is valid.
+func (s Status) Valid() bool {
+	return s < last
+}
+
+// String implements the fmt.Stringer interface.
+func (s Status) String() string {
+	switch s {
+	case Allow:
+		return "Allowed"
+	case NoRuleFound:
+		return "NoRuleFound"
+	case AccessDenied:
+		return "Access denied"
+	case QuotaLimitReached:
+		return "Quota limit reached"
+	default:
+		return fmt.Sprintf("Denied with status: %d", s)
+	}
+}

glob.go

@@ -0,0 +1,22 @@
+package policyengine
+
+import (
+	"strings"
+	"unicode/utf8"
+)
+
+// Matches s against the pattern.
+// ? in pattern correspond to any symbol.
+// * in pattern correspond to any sequence of symbols.
+// Currently only '*' in the suffix is supported.
+func globMatch(s, pattern string) bool {
+	index := strings.IndexByte(pattern, '*')
+	switch index {
+	default:
+		panic("unimplemented")
+	case -1:
+		return pattern == s
+	case utf8.RuneCountInString(pattern) - 1:
+		return strings.HasPrefix(s, pattern[:len(pattern)-1])
+	}
+}

go.mod

@@ -0,0 +1,11 @@
+module git.frostfs.info/TrueCloudLab/policy-engine
+
+go 1.20
+
+require github.com/stretchr/testify v1.8.1
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,17 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+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/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=
+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/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

inmemory.go

@@ -0,0 +1,76 @@
+package policyengine
+
+type inmemory struct {
+	namespace map[Name][]chain
+	resource  map[Name][]chain
+	local     map[Name][]*Chain
+}
+
+type chain struct {
+	object string
+	chain  *Chain
+}
+
+// NewInMemory returns new inmemory instance of chain storage.
+func NewInMemory() CachedChainStorage {
+	return &inmemory{
+		namespace: make(map[Name][]chain),
+		resource:  make(map[Name][]chain),
+		local:     make(map[Name][]*Chain),
+	}
+}
+
+// TODO параметры для actor (IP)
+// TODO
+func (s *inmemory) IsAllowed(name Name, namespace string, r Request) (Status, bool) {
+	var ruleFound bool
+	if local, ok := s.local[name]; ok {
+		for _, c := range local {
+			if status, matched := c.Match(r); matched && status != Allow {
+				return status, true
+			}
+		}
+	}
+	if cs, ok := s.namespace[name]; ok {
+		status, ok := matchArray(cs, namespace, r)
+		if ok && status != Allow {
+			return status, true
+		}
+		ruleFound = ruleFound || ok
+	}
+	if cs, ok := s.resource[name]; ok {
+		status, ok := matchArray(cs, r.Resource().Name(), r)
+		if ok {
+			return status, true
+		}
+		ruleFound = ruleFound || ok
+	}
+	if ruleFound {
+		return Allow, true
+	}
+	return NoRuleFound, false
+}
+
+func matchArray(cs []chain, object string, r Request) (Status, bool) {
+	for _, c := range cs {
+		if !globMatch(object, c.object) {
+			continue
+		}
+		if status, matched := c.chain.Match(r); matched {
+			return status, true
+		}
+	}
+	return NoRuleFound, false
+}
+
+func (s *inmemory) AddResourceChain(name Name, resource string, c *Chain) {
+	s.resource[name] = append(s.resource[name], chain{resource, c})
+}
+
+func (s *inmemory) AddNameSpaceChain(name Name, namespace string, c *Chain) {
+	s.namespace[name] = append(s.namespace[name], chain{namespace, c})
+}
+
+func (s *inmemory) AddOverride(name Name, c *Chain) {
+	s.local[name] = append(s.local[name], c)
+}

inmemory_test.go

@@ -0,0 +1,166 @@
+package policyengine
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestInmemory(t *testing.T) {
+	const (
+		object    = "native::object::abc/xyz"
+		container = "native::object::abc/*"
+		namespace = "Tenant1"
+		actor1    = "owner1"
+		actor2    = "owner2"
+	)
+
+	s := NewInMemory()
+
+	// Object which was put via S3.
+	res := newResource(object, map[string]string{"FromS3": "true"})
+	// Request initiating from the trusted subnet and actor.
+	reqGood := newRequest("native::object::put", res, map[string]string{
+		"SourceIP": "10.1.1.12",
+		"Actor":    actor1,
+	})
+
+	status, ok := s.IsAllowed(Ingress, namespace, reqGood)
+	require.Equal(t, NoRuleFound, status)
+	require.False(t, ok)
+
+	s.AddNameSpaceChain(Ingress, namespace, &Chain{
+		Rules: []Rule{
+			{ // Restrict to remove ANY object from the namespace.
+				Status:   AccessDenied,
+				Action:   []string{"native::object::delete"},
+				Resource: []string{"native::object::*"},
+			},
+			{ // Allow to put object only from the trusted subnet AND trusted actor, deny otherwise.
+				Status:   AccessDenied,
+				Action:   []string{"native::object::put"},
+				Resource: []string{"native::object::*"},
+				Any:      true,
+				Condition: []Condition{
+					{
+						Op:     CondStringNotLike,
+						Object: ObjectRequest,
+						Key:    "SourceIP",
+						Value:  "10.1.1.*",
+					},
+					{
+						Op:     CondStringNotEquals,
+						Object: ObjectRequest,
+						Key:    "Actor",
+						Value:  actor1,
+					},
+				},
+			},
+		},
+	})
+
+	s.AddResourceChain(Ingress, container, &Chain{
+		Rules: []Rule{
+			{ // Allow to actor2 to get objects from the specific container only if they have `Department=HR` attribute.
+				Status:   Allow,
+				Action:   []string{"native::object::get"},
+				Resource: []string{"native::object::abc/*"},
+				Condition: []Condition{
+					{
+						Op:     CondStringEquals,
+						Object: ObjectResource,
+						Key:    "Department",
+						Value:  "HR",
+					},
+					{
+						Op:     CondStringEquals,
+						Object: ObjectRequest,
+						Key:    "Actor",
+						Value:  actor2,
+					},
+				},
+			},
+		},
+	})
+
+	t.Run("bad subnet, namespace deny", func(t *testing.T) {
+		// Request initiating from the untrusted subnet.
+		reqBadIP := newRequest("native::object::put", res, map[string]string{
+			"SourceIP": "10.122.1.20",
+			"Actor":    actor1,
+		})
+		status, ok := s.IsAllowed(Ingress, namespace, reqBadIP)
+		require.Equal(t, AccessDenied, status)
+		require.True(t, ok)
+	})
+	t.Run("bad actor, namespace deny", func(t *testing.T) {
+		// Request initiating from the untrusted actor.
+		reqBadActor := newRequest("native::object::put", res, map[string]string{
+			"SourceIP": "10.1.1.13",
+			"Actor":    actor2,
+		})
+		status, ok := s.IsAllowed(Ingress, namespace, reqBadActor)
+		require.Equal(t, AccessDenied, status)
+		require.True(t, ok)
+	})
+	t.Run("bad object, container deny", func(t *testing.T) {
+		objGood := newResource("native::object::abc/id1", map[string]string{"Department": "HR"})
+		objBadAttr := newResource("native::object::abc/id2", map[string]string{"Department": "Support"})
+
+		status, ok := s.IsAllowed(Ingress, namespace, newRequest("native::object::get", objGood, map[string]string{
+			"SourceIP": "10.1.1.14",
+			"Actor":    actor2,
+		}))
+		require.Equal(t, Allow, status)
+		require.True(t, ok)
+
+		status, ok = s.IsAllowed(Ingress, namespace, newRequest("native::object::get", objBadAttr, map[string]string{
+			"SourceIP": "10.1.1.14",
+			"Actor":    actor2,
+		}))
+		require.Equal(t, NoRuleFound, status)
+		require.False(t, ok)
+	})
+	t.Run("bad operation, namespace deny", func(t *testing.T) {
+		// Request with the forbidden operation.
+		reqBadOperation := newRequest("native::object::delete", res, map[string]string{
+			"SourceIP": "10.1.1.12",
+			"Actor":    actor1,
+		})
+		status, ok := s.IsAllowed(Ingress, namespace, reqBadOperation)
+		require.Equal(t, AccessDenied, status)
+		require.True(t, ok)
+	})
+	t.Run("good", func(t *testing.T) {
+		status, ok = s.IsAllowed(Ingress, namespace, reqGood)
+		require.Equal(t, NoRuleFound, status)
+		require.False(t, ok)
+
+		t.Run("quota on a different container", func(t *testing.T) {
+			s.AddOverride(Ingress, &Chain{
+				Rules: []Rule{{
+					Status:   QuotaLimitReached,
+					Action:   []string{"native::object::put"},
+					Resource: []string{"native::object::cba/*"},
+				}},
+			})
+
+			status, ok = s.IsAllowed(Ingress, namespace, reqGood)
+			require.Equal(t, NoRuleFound, status)
+			require.False(t, ok)
+		})
+		t.Run("quota on the request container", func(t *testing.T) {
+			s.AddOverride(Ingress, &Chain{
+				Rules: []Rule{{
+					Status:   QuotaLimitReached,
+					Action:   []string{"native::object::put"},
+					Resource: []string{"native::object::abc/*"},
+				}},
+			})
+
+			status, ok = s.IsAllowed(Ingress, namespace, reqGood)
+			require.Equal(t, QuotaLimitReached, status)
+			require.True(t, ok)
+		})
+	})
+}

interface.go

@@ -0,0 +1,12 @@
+package policyengine
+
+// CachedChainStorage ...
+type CachedChainStorage interface {
+	Engine
+	// Adds a policy chain used for all operations with a specific resource.
+	AddResourceChain(name Name, resource string, c *Chain)
+	// Adds a policy chain used for all operations in the namespace.
+	AddNameSpaceChain(name Name, namespace string, c *Chain)
+	// Adds a local policy chain used for all operations with this service.
+	AddOverride(name Name, c *Chain)
+}

policy.go

@@ -0,0 +1,139 @@
+package policyengine
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+type (
+	// IAMPolicy grammar https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_grammar.html
+	IAMPolicy struct {
+		Version   string        `json:"Version,omitempty"`
+		ID        string        `json:"Id,omitempty"`
+		Statement IAMStatements `json:"Statement"`
+	}
+
+	IAMStatements []IAMStatement
+
+	IAMStatement struct {
+		SID       string       `json:"Sid,omitempty"`
+		Principal IAMPrincipal `json:"Principal,omitempty"`
+		Effect    IAMEffect    `json:"Effect"`
+		Action    IAMAction    `json:"Action"`
+		Resource  IAMResource  `json:"Resource"`
+		Condition IAMCondition `json:"Condition,omitempty"`
+	}
+
+	IAMPrincipal map[string][]string
+
+	IAMEffect string
+
+	IAMAction []string
+
+	IAMResource []string
+
+	IAMCondition map[string]map[string]string
+)
+
+const IAMWildcard = "*"
+
+const (
+	IAMAllowEffect IAMEffect = "Allow"
+	IAMDenyEffect  IAMEffect = "Deny"
+)
+
+func (s *IAMStatements) UnmarshalJSON(data []byte) error {
+	var list []IAMStatement
+	if err := json.Unmarshal(data, &list); err == nil {
+		*s = list
+		return nil
+	}
+
+	var elem IAMStatement
+	if err := json.Unmarshal(data, &elem); err != nil {
+		return err
+	}
+
+	*s = []IAMStatement{elem}
+
+	return nil
+}
+
+func (p *IAMPrincipal) UnmarshalJSON(data []byte) error {
+	*p = make(IAMPrincipal)
+
+	var str string
+
+	if err := json.Unmarshal(data, &str); err == nil {
+		if str != IAMWildcard {
+			return errors.New("invalid IAM string principal")
+		}
+		(*p)[IAMWildcard] = nil
+		return nil
+	}
+
+	m := make(map[string]interface{})
+	if err := json.Unmarshal(data, &m); err != nil {
+		return err
+	}
+
+	for key, val := range m {
+		element, ok := val.(string)
+		if ok {
+			(*p)[key] = []string{element}
+			continue
+		}
+
+		list, ok := val.([]interface{})
+		if !ok {
+			return errors.New("invalid principal format")
+		}
+
+		resList := make([]string, len(list))
+		for i := range list {
+			val, ok := list[i].(string)
+			if !ok {
+				return errors.New("invalid principal format")
+			}
+			resList[i] = val
+		}
+
+		(*p)[key] = resList
+	}
+
+	return nil
+}
+
+func (a *IAMAction) UnmarshalJSON(data []byte) error {
+	var list []string
+	if err := json.Unmarshal(data, &list); err == nil {
+		*a = list
+		return nil
+	}
+
+	var elem string
+	if err := json.Unmarshal(data, &elem); err != nil {
+		return err
+	}
+
+	*a = []string{elem}
+
+	return nil
+}
+
+func (r *IAMResource) UnmarshalJSON(data []byte) error {
+	var list []string
+	if err := json.Unmarshal(data, &list); err == nil {
+		*r = list
+		return nil
+	}
+
+	var elem string
+	if err := json.Unmarshal(data, &elem); err != nil {
+		return err
+	}
+
+	*r = []string{elem}
+
+	return nil
+}

policy_test.go

@@ -0,0 +1,151 @@
+package policyengine
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUnmarshalIAMPolicy(t *testing.T) {
+	t.Run("simple fields", func(t *testing.T) {
+		policy := `{
+	"Version": "2012-10-17",
+	"Id": "PutObjPolicy",
+	"Statement": {
+		"Sid": "DenyObjectsThatAreNotSSEKMS",
+		"Principal": "*",
+		"Effect": "Deny",
+		"Action": "s3:PutObject",
+		"Resource": "arn:aws:s3:::DOC-EXAMPLE-BUCKET/*",
+		"Condition": {
+			"Null": {
+				"s3:x-amz-server-side-encryption-aws-kms-key-id": "true"
+			}
+		}
+	}
+}`
+
+		expected := IAMPolicy{
+			Version: "2012-10-17",
+			ID:      "PutObjPolicy",
+			Statement: []IAMStatement{{
+				SID: "DenyObjectsThatAreNotSSEKMS",
+				Principal: map[string][]string{
+					"*": nil,
+				},
+				Effect:   IAMDenyEffect,
+				Action:   []string{"s3:PutObject"},
+				Resource: []string{"arn:aws:s3:::DOC-EXAMPLE-BUCKET/*"},
+				Condition: map[string]map[string]string{
+					"Null": {
+						"s3:x-amz-server-side-encryption-aws-kms-key-id": "true",
+					},
+				},
+			}},
+		}
+
+		var p IAMPolicy
+		err := json.Unmarshal([]byte(policy), &p)
+		require.NoError(t, err)
+		require.Equal(t, expected, p)
+	})
+
+	t.Run("complex fields", func(t *testing.T) {
+		policy := `{
+	"Version": "2012-10-17",
+	"Statement": [{
+		"Principal":{
+			"AWS":[
+				"arn:aws:iam::111122223333:user/JohnDoe"
+			]
+		},
+		"Effect": "Allow",
+		"Action": [
+			"s3:PutObject"
+		],
+		"Resource": [
+			"arn:aws:s3:::DOC-EXAMPLE-BUCKET/*"
+		],
+		"Condition": {
+			"StringEquals": {
+				"s3:RequestObjectTag/Department": "Finance"
+			}
+		}
+	}]
+}`
+
+		expected := IAMPolicy{
+			Version: "2012-10-17",
+			Statement: []IAMStatement{{
+				Principal: map[string][]string{
+					"AWS": {"arn:aws:iam::111122223333:user/JohnDoe"},
+				},
+				Effect:   IAMAllowEffect,
+				Action:   []string{"s3:PutObject"},
+				Resource: []string{"arn:aws:s3:::DOC-EXAMPLE-BUCKET/*"},
+				Condition: map[string]map[string]string{
+					"StringEquals": {
+						"s3:RequestObjectTag/Department": "Finance",
+					},
+				},
+			}},
+		}
+
+		var p IAMPolicy
+		err := json.Unmarshal([]byte(policy), &p)
+		require.NoError(t, err)
+		require.Equal(t, expected, p)
+
+		raw, err := json.Marshal(expected)
+		require.NoError(t, err)
+		require.JSONEq(t, policy, string(raw))
+	})
+
+	t.Run("check principal AWS", func(t *testing.T) {
+		policy := `{
+	"Statement": [{
+		"Principal":{
+			"AWS":"arn:aws:iam::111122223333:user/JohnDoe"
+		}
+	}]
+}`
+
+		expected := IAMPolicy{
+			Statement: []IAMStatement{{
+				Principal: map[string][]string{
+					"AWS": {"arn:aws:iam::111122223333:user/JohnDoe"},
+				},
+			}},
+		}
+
+		var p IAMPolicy
+		err := json.Unmarshal([]byte(policy), &p)
+		require.NoError(t, err)
+		require.Equal(t, expected, p)
+	})
+
+	t.Run("native example", func(t *testing.T) {
+		policy := `
+{
+	"Version": "xyz",
+	"Statement": [
+	  {
+		"Effect": "Allow",
+		"Action": [
+		  "native:*",
+		  "s3:PutObject",
+		  "s3:GetObject"
+		],
+		"Resource": ["*"],
+		"Principal": {"FrostFS": ["did:frostfs:039e3ee771a223361fe7862f532e9511b57baaae3c3e2622682e99d0e660f7671"]},
+		"Condition": {"StringEquals": {"native::object::attribute": "iamuser-admin"}}
+	  }
+	]
+}`
+
+		var p IAMPolicy
+		err := json.Unmarshal([]byte(policy), &p)
+		require.NoError(t, err)
+	})
+}

resource.go

@@ -0,0 +1,19 @@
+package policyengine
+
+// Request represents generic named resource (bucket, container etc.).
+// Name is resource depenent but should be globally unique for any given
+// type of resource.
+type Request interface {
+	// Name is the operation name, such as Object.Put. Must not include wildcards.
+	Operation() string
+	// Property returns request properties, such as IP address of the origin.
+	Property(string) string
+	// Resource returns resource the operation is applied to.
+	Resource() Resource
+}
+
+// Resource represents the resource operation is applied to.
+type Resource interface {
+	Name() string
+	Property(string) string
+}

resource_test.go

@@ -0,0 +1,49 @@
+package policyengine
+
+type resource struct {
+	name       string
+	properties map[string]string
+}
+
+func (r *resource) Name() string {
+	return r.name
+}
+
+func (r *resource) Property(name string) string {
+	return r.properties[name]
+}
+
+func newResource(name string, properties map[string]string) *resource {
+	if properties == nil {
+		properties = make(map[string]string)
+	}
+	return &resource{name: name, properties: properties}
+}
+
+type request struct {
+	operation  string
+	properties map[string]string
+	resource   *resource
+}
+
+var _ Request = (*request)(nil)
+
+func (r *request) Operation() string {
+	return r.operation
+}
+
+func (r *request) Resource() Resource {
+	return r.resource
+}
+
+func (r *request) Property(name string) string {
+	return r.properties[name]
+}
+
+func newRequest(op string, r *resource, properties map[string]string) *request {
+	return &request{
+		operation:  op,
+		properties: properties,
+		resource:   r,
+	}
+}