attributes.go 18 KB
Newer Older
1
package irma
2
3
4

import (
	"crypto/sha256"
5
	"encoding/binary"
Sietse Ringers's avatar
Sietse Ringers committed
6
	"encoding/hex"
7
	"encoding/json"
8
	"math/big"
9
	"time"
10

11
	"fmt"
Sietse Ringers's avatar
Sietse Ringers committed
12
	"github.com/go-errors/errors"
13
14
15
	"github.com/mhe/gabi"
)

16
17
const (
	// ExpiryFactor is the precision for the expiry attribute. Value is one week.
18
19
	ExpiryFactor   = 60 * 60 * 24 * 7
	metadataLength = 1 + 3 + 2 + 2 + 16
20
21
)

22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
type AttributeResultList struct {
	AttributeResults []*AttributeResult
}

type AttributeResult struct {
	AttributeValue       TranslatedString // Value of the disclosed attribute
	AttributeId          AttributeTypeIdentifier
	AttributeProofStatus AttributeProofStatus
}

type AttributeProofStatus string

const (
	PRESENT       = AttributeProofStatus("PRESENT")       // Attribute is disclosed and matches the value
	UNKNOWN       = AttributeProofStatus("UNKNOWN")       // Attribute is disclosed, but status is yet unknown
	MISSING       = AttributeProofStatus("MISSING")       // Attribute is NOT disclosed, but should be according to request
	INVALID_VALUE = AttributeProofStatus("INVALID_VALUE") // Attribute is disclosed, but has invalid value according to request
)

41
42
43
var (
	metadataVersion = []byte{0x02}

Sietse Ringers's avatar
Sietse Ringers committed
44
45
46
47
48
	versionField     = metadataField{1, 0}
	signingDateField = metadataField{3, 1}
	validityField    = metadataField{2, 4}
	keyCounterField  = metadataField{2, 6}
	credentialID     = metadataField{16, 8}
49
50
)

Sietse Ringers's avatar
Sietse Ringers committed
51
52
// metadataField contains the length and offset of a field within a metadata attribute.
type metadataField struct {
53
54
55
56
57
58
	length int
	offset int
}

// MetadataAttribute represent a metadata attribute. Contains the credential type, signing date, validity, and the public key counter.
type MetadataAttribute struct {
59
60
61
	Int  *big.Int
	pk   *gabi.PublicKey
	Conf *Configuration
62
63
}

64
65
66
// AttributeList contains attributes, excluding the secret key,
// providing convenient access to the metadata attribute.
type AttributeList struct {
67
	*MetadataAttribute `json:"-"`
68
	Ints               []*big.Int
Sietse Ringers's avatar
Sietse Ringers committed
69
	strings            []TranslatedString
70
	info               *CredentialInfo
71
	h                  string
72
73
}

74
// NewAttributeListFromInts initializes a new AttributeList from a list of bigints.
75
func NewAttributeListFromInts(ints []*big.Int, conf *Configuration) *AttributeList {
76
	return &AttributeList{
77
		Ints:              ints,
78
		MetadataAttribute: MetadataFromInt(ints[0], conf),
79
	}
80
81
}

82
83
84
85
86
87
88
89
90
91
// NewAttributeListFromInts initializes a new AttributeList from disclosed attributes of a prooflist
func NewAttributeListFromADisclosed(aResponses map[int]*big.Int, aDisclosed map[int]*big.Int, conf *Configuration) (*AttributeList, error) {
	ints, err := convertProofResponsesToInts(aResponses, aDisclosed)
	if err != nil {
		return nil, err
	}

	return NewAttributeListFromInts(ints, conf), nil
}

92
func (al *AttributeList) Info() *CredentialInfo {
93
	if al.info == nil {
94
		al.info = NewCredentialInfo(al.Ints, al.Conf)
95
	}
96
	return al.info
97
98
}

99
func (al *AttributeList) Hash() string {
100
101
102
	if al.h == "" {
		bytes := []byte{}
		for _, i := range al.Ints {
103
104
105
			if i != nil {
				bytes = append(bytes, i.Bytes()...)
			}
106
107
108
		}
		shasum := sha256.Sum256(bytes)
		al.h = hex.EncodeToString(shasum[:])
109
	}
110
	return al.h
111
112
}

113
// Strings converts the current instance to human-readable strings.
Sietse Ringers's avatar
Sietse Ringers committed
114
func (al *AttributeList) Strings() []TranslatedString {
115
	if al.strings == nil {
Sietse Ringers's avatar
Sietse Ringers committed
116
		al.strings = make([]TranslatedString, len(al.Ints)-1)
117
		for index, num := range al.Ints[1:] { // skip metadata
118
119
120
121
122
			if num == nil {
				al.strings[index] = nil
			} else {
				al.strings[index] = map[string]string{"en": string(num.Bytes()), "nl": string(num.Bytes())} // TODO
			}
123
124
125
126
		}
	}
	return al.strings
}
127

128
func (al *AttributeList) UntranslatedAttribute(identifier AttributeTypeIdentifier) string {
129
130
131
	if al.CredentialType().Identifier() != identifier.CredentialTypeIdentifier() {
		return ""
	}
132
	for i, desc := range al.CredentialType().Attributes {
133
		if desc.ID == string(identifier.Name()) {
Sietse Ringers's avatar
Sietse Ringers committed
134
			return string(al.Ints[i+1].Bytes())
135
136
137
138
139
		}
	}
	return ""
}

Sietse Ringers's avatar
Sietse Ringers committed
140
141
142
143
144
145
146
147
148
149
150
151
152
// Attribute returns the content of the specified attribute, or "" if not present in this attribute list.
func (al *AttributeList) Attribute(identifier AttributeTypeIdentifier) TranslatedString {
	if al.CredentialType().Identifier() != identifier.CredentialTypeIdentifier() {
		return nil
	}
	for i, desc := range al.CredentialType().Attributes {
		if desc.ID == string(identifier.Name()) {
			return al.Strings()[i]
		}
	}
	return nil
}

153
// MetadataFromInt wraps the given Int
154
155
func MetadataFromInt(i *big.Int, conf *Configuration) *MetadataAttribute {
	return &MetadataAttribute{Int: i, Conf: conf}
156
157
158
159
160
161
162
163
}

// NewMetadataAttribute constructs a new instance containing the default values:
// 0x02 as versionField
// now as signing date
// 0 as keycounter
// ValidityDefault (half a year) as default validity.
func NewMetadataAttribute() *MetadataAttribute {
164
	val := MetadataAttribute{new(big.Int), nil, nil}
165
166
167
	val.setField(versionField, metadataVersion)
	val.setSigningDate()
	val.setKeyCounter(0)
168
	val.setDefaultValidityDuration()
169
170
171
172
173
174
175
176
177
178
179
180
181
182
	return &val
}

// Bytes returns this metadata attribute as a byte slice.
func (attr *MetadataAttribute) Bytes() []byte {
	bytes := attr.Int.Bytes()
	if len(bytes) < metadataLength {
		bytes = append(bytes, make([]byte, metadataLength-len(bytes))...)
	}
	return bytes
}

// PublicKey extracts identifier of the Idemix public key with which this instance was signed,
// and returns this public key.
183
func (attr *MetadataAttribute) PublicKey() (*gabi.PublicKey, error) {
184
	if attr.pk == nil {
185
		var err error
186
		attr.pk, err = attr.Conf.PublicKey(attr.CredentialType().IssuerIdentifier(), attr.KeyCounter())
187
188
189
		if err != nil {
			return nil, err
		}
190
	}
191
	return attr.pk, nil
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
}

// Version returns the metadata version of this instance
func (attr *MetadataAttribute) Version() byte {
	return attr.field(versionField)[0]
}

// SigningDate returns the time at which this instance was signed
func (attr *MetadataAttribute) SigningDate() time.Time {
	bytes := attr.field(signingDateField)
	bytes = bytes[1:] // The signing date field is one byte too long
	timestamp := int64(binary.BigEndian.Uint16(bytes)) * ExpiryFactor
	return time.Unix(timestamp, 0)
}

func (attr *MetadataAttribute) setSigningDate() {
	attr.setField(signingDateField, shortToByte(int(time.Now().Unix()/ExpiryFactor)))
}

// KeyCounter return the public key counter of the metadata attribute
func (attr *MetadataAttribute) KeyCounter() int {
	return int(binary.BigEndian.Uint16(attr.field(keyCounterField)))
}

func (attr *MetadataAttribute) setKeyCounter(i int) {
	attr.setField(keyCounterField, shortToByte(i))
}

// ValidityDuration returns the amount of epochs during which this instance is valid
func (attr *MetadataAttribute) ValidityDuration() int {
	return int(binary.BigEndian.Uint16(attr.field(validityField)))
}

func (attr *MetadataAttribute) setValidityDuration(weeks int) {
	attr.setField(validityField, shortToByte(weeks))
}

229
230
231
232
func (attr *MetadataAttribute) setDefaultValidityDuration() {
	attr.setExpiryDate(nil)
}

Sietse Ringers's avatar
Sietse Ringers committed
233
func (attr *MetadataAttribute) setExpiryDate(timestamp *Timestamp) error {
234
	var expiry int64
Sietse Ringers's avatar
Sietse Ringers committed
235
	if timestamp == nil {
236
		expiry = time.Now().AddDate(0, 6, 0).Unix()
237
238
	} else {
		expiry = time.Time(*timestamp).Unix()
Sietse Ringers's avatar
Sietse Ringers committed
239
	}
Sietse Ringers's avatar
Sietse Ringers committed
240
241
242
243
244
	signing := attr.SigningDate().Unix()
	attr.setValidityDuration(int((expiry - signing) / ExpiryFactor))
	return nil
}

245
// CredentialType returns the credential type of the current instance
246
// using the Configuration.
247
func (attr *MetadataAttribute) CredentialType() *CredentialType {
248
	return attr.Conf.hashToCredentialType(attr.field(credentialID))
249
250
}

251
func (attr *MetadataAttribute) setCredentialTypeIdentifier(id string) {
252
253
254
255
	bytes := sha256.Sum256([]byte(id))
	attr.setField(credentialID, bytes[:16])
}

256
257
258
259
func (attr *MetadataAttribute) CredentialTypeHash() []byte {
	return attr.field(credentialID)
}

260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
// Expiry returns the expiry date of this instance
func (attr *MetadataAttribute) Expiry() time.Time {
	expiry := attr.SigningDate().Unix() + int64(attr.ValidityDuration()*ExpiryFactor)
	return time.Unix(expiry, 0)
}

// IsValidOn returns whether this instance is still valid at the given time
func (attr *MetadataAttribute) IsValidOn(t time.Time) bool {
	return attr.Expiry().After(t)
}

// IsValid returns whether this instance is valid.
func (attr *MetadataAttribute) IsValid() bool {
	return attr.IsValidOn(time.Now())
}

Sietse Ringers's avatar
Sietse Ringers committed
276
func (attr *MetadataAttribute) field(field metadataField) []byte {
277
278
279
	return attr.Bytes()[field.offset : field.offset+field.length]
}

Sietse Ringers's avatar
Sietse Ringers committed
280
func (attr *MetadataAttribute) setField(field metadataField, value []byte) {
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
	if len(value) > field.length {
		panic("Specified metadata field too large")
	}

	bytes := attr.Bytes()

	// Push the value to the right within the field. Graphical representation:
	// --xxxXXX----
	// "-" indicates a byte of another field
	// "X" is a byte of the value and "x" of our field
	// In this example, our field has offset 2, length 6,
	// but the specified value is only 3 bytes long.
	startindex := field.length - len(value)
	for i := 0; i < field.length; i++ {
		if i < startindex {
			bytes[i+field.offset] = 0
		} else {
			bytes[i+field.offset] = value[i-startindex]
		}
	}

	attr.Int.SetBytes(bytes)
}

func shortToByte(x int) []byte {
	bytes := make([]byte, 2)
	binary.BigEndian.PutUint16(bytes, uint16(x))
	return bytes
}
310

311
312
313
314
315
// A DisclosureChoice contains the attributes chosen to be disclosed.
type DisclosureChoice struct {
	Attributes []*AttributeIdentifier
}

316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
// An AttributeDisjunction encapsulates a list of possible attributes, one
// of which should be disclosed.
type AttributeDisjunction struct {
	Label      string
	Attributes []AttributeTypeIdentifier
	Values     map[AttributeTypeIdentifier]string

	selected *AttributeTypeIdentifier
}

// An AttributeDisjunctionList is a list of AttributeDisjunctions.
type AttributeDisjunctionList []*AttributeDisjunction

// HasValues indicates if the attributes of this disjunction have values
// that should be satisfied.
func (disjunction *AttributeDisjunction) HasValues() bool {
	return disjunction.Values != nil && len(disjunction.Values) != 0
}

// Satisfied indicates if this disjunction has a valid chosen attribute
// to be disclosed.
func (disjunction *AttributeDisjunction) Satisfied() bool {
	if disjunction.selected == nil {
		return false
	}
	for _, attr := range disjunction.Attributes {
		if *disjunction.selected == attr {
			return true
		}
	}
	return false
}

349
350
351
// Helper function to check if an attribute is satisfied against a list of disclosed attributes
// This is the case if:
// attribute is contained in disclosed AND if a value is present: equal to that value
352
353
// al can be nil if you don't want to include attribute status for proof
func isAttributeSatisfied(attribute AttributeTypeIdentifier, value string, disclosed []*CredentialInfo, conf *Configuration, al *AttributeResultList) bool {
354
355
356
357
358
359
360
361
362
363
	for _, cred := range disclosed {
		credentialType := cred.GetCredentialType(conf)
		index, err := credentialType.IndexOf(attribute)

		if err != nil {
			// Specified credential does not contain this attribute, move to next cred in list of disclosed credentials
			continue
		}

		disclosedAttributeValue := cred.Attributes[index]
364
365
		// If it contains this attribute, check if value matches (it must be disclosed (i.e. not nil) and match the value)
		// Attribute is satisfied if:
366
367
		// - Attribute is disclosed (i.e. not nil)
		// - Value is empty OR value equal to disclosedValue
368
369
370
371
372
373
374
375
376
		if disclosedAttributeValue != nil {
			if value == "" || disclosedAttributeValue["en"] == value { // TODO: fix translation/attr typing
				al.SetProofStatus(attribute, disclosedAttributeValue, PRESENT)
				return true
			} else {
				// If attribute is disclosed and present, but not equal to required value, mark it as invalid_value
				// We won't return true and continue searching in other disclosed attributes
				al.SetProofStatus(attribute, disclosedAttributeValue, INVALID_VALUE)
			}
377
378
379
380
381
382
383
		}
	}
	return false
}

// Check whether specified attributedisjunction satisfy a list of disclosed attributes
// We return true if one of the attributes in the disjunction is satisfied
384
func (disjunction *AttributeDisjunction) SatisfyDisclosed(disclosed []*CredentialInfo, conf *Configuration, al *AttributeResultList) bool {
385
386
387
	for _, attr := range disjunction.Attributes {
		value := disjunction.Values[attr]

388
		if isAttributeSatisfied(attr, value, disclosed, conf, al) {
389
390
391
392
			return true
		}
	}

393
394
395
396
397
398
399
400
401
402
403
	// Add all missing attributes
	for _, attr := range disjunction.Attributes {
		ar := AttributeResult{
			AttributeId:          attr,
			AttributeProofStatus: MISSING,
		}
		if !al.ContainsAttributeId(ar.AttributeId) {
			al.Append(ar)
		}
	}

404
405
406
	return false
}

407
408
409
// MatchesConfig returns true if all attributes contained in the disjunction are
// present in the specified configuration.
func (disjunction *AttributeDisjunction) MatchesConfig(conf *Configuration) bool {
410
	for ai := range disjunction.Values {
411
		creddescription, exists := conf.CredentialTypes[ai.CredentialTypeIdentifier()]
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
		if !exists {
			return false
		}
		if !creddescription.ContainsAttribute(ai) {
			return false
		}
	}
	return true
}

// Satisfied indicates whether each contained attribute disjunction has a chosen attribute.
func (dl AttributeDisjunctionList) Satisfied() bool {
	for _, disjunction := range dl {
		if !disjunction.Satisfied() {
			return false
		}
	}
	return true
}

// Find searches for and returns the disjunction that contains the specified attribute identifier, or nil if not found.
func (dl AttributeDisjunctionList) Find(ai AttributeTypeIdentifier) *AttributeDisjunction {
	for _, disjunction := range dl {
		for _, attr := range disjunction.Attributes {
			if attr == ai {
				return disjunction
			}
		}
	}
	return nil
}

// MarshalJSON marshals the disjunction to JSON.
func (disjunction *AttributeDisjunction) MarshalJSON() ([]byte, error) {
	if !disjunction.HasValues() {
		temp := struct {
			Label      string                    `json:"label"`
			Attributes []AttributeTypeIdentifier `json:"attributes"`
		}{
			Label:      disjunction.Label,
			Attributes: disjunction.Attributes,
		}
		return json.Marshal(temp)
	}

	temp := struct {
		Label      string                             `json:"label"`
		Attributes map[AttributeTypeIdentifier]string `json:"attributes"`
	}{
		Label:      disjunction.Label,
		Attributes: disjunction.Values,
	}
	return json.Marshal(temp)
}

// UnmarshalJSON unmarshals an attribute disjunction from JSON.
func (disjunction *AttributeDisjunction) UnmarshalJSON(bytes []byte) error {
	if disjunction.Values == nil {
		disjunction.Values = make(map[AttributeTypeIdentifier]string)
	}
	if disjunction.Attributes == nil {
		disjunction.Attributes = make([]AttributeTypeIdentifier, 0, 3)
	}

	// We don't know if the json element "attributes" is a list, or a map.
	// So we unmarshal it into a temporary struct that has interface{} as the
	// type of "attributes", so that we can check which of the two it is.
	temp := struct {
		Label      string      `json:"label"`
		Attributes interface{} `json:"attributes"`
	}{}
Sietse Ringers's avatar
Sietse Ringers committed
483
484
485
	if err := json.Unmarshal(bytes, &temp); err != nil {
		return err
	}
486
487
488
489
490
491
492
493
	disjunction.Label = temp.Label

	switch temp.Attributes.(type) {
	case map[string]interface{}:
		temp := struct {
			Label      string            `json:"label"`
			Attributes map[string]string `json:"attributes"`
		}{}
Sietse Ringers's avatar
Sietse Ringers committed
494
495
496
		if err := json.Unmarshal(bytes, &temp); err != nil {
			return err
		}
497
498
499
500
501
502
503
504
505
506
		for str, value := range temp.Attributes {
			id := NewAttributeTypeIdentifier(str)
			disjunction.Attributes = append(disjunction.Attributes, id)
			disjunction.Values[id] = value
		}
	case []interface{}:
		temp := struct {
			Label      string   `json:"label"`
			Attributes []string `json:"attributes"`
		}{}
Sietse Ringers's avatar
Sietse Ringers committed
507
508
509
		if err := json.Unmarshal(bytes, &temp); err != nil {
			return err
		}
510
511
512
513
514
515
516
517
518
		for _, str := range temp.Attributes {
			disjunction.Attributes = append(disjunction.Attributes, NewAttributeTypeIdentifier(str))
		}
	default:
		return errors.New("could not parse attribute disjunction: element 'attributes' was incorrect")
	}

	return nil
}
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602

// From here attributeResult related functions. TODO: move to separate file?

func (al *AttributeResultList) Append(result AttributeResult) {
	al.AttributeResults = append(al.AttributeResults, &result)
}

func (al *AttributeResultList) ContainsAttributeId(attrId AttributeTypeIdentifier) bool {
	for _, ar := range al.AttributeResults {
		if ar.AttributeId == attrId {
			return true
		}
	}
	return false
}

func (al *AttributeResultList) String() string {
	// TODO: pretty print?
	str := "Attribute --- Value --- ProofStatus:"
	for _, v := range al.AttributeResults {
		str = str + "\n" + v.String()
	}
	return str
}

// Set the proof status to a new status for a specified attribute. An attribute is specified by an attributeTypeIdentifier
func (al *AttributeResultList) SetProofStatus(attrID AttributeTypeIdentifier, attrValue TranslatedString, status AttributeProofStatus) bool {
	for _, ar := range al.AttributeResults {
		// TODO: translation
		if ar.AttributeId == attrID && ar.AttributeValue["en"] == attrValue["en"] {
			ar.AttributeProofStatus = status
			return true
		}
	}
	return false
}

func (ar *AttributeResult) GetAttributeDescription(conf *Configuration) (*AttributeDescription, error) {
	cred := conf.CredentialTypes[NewCredentialTypeIdentifier(ar.AttributeId.Parent())]
	index, err := cred.IndexOf(ar.AttributeId)

	if err != nil {
		return nil, err
	}

	return &cred.Attributes[index], nil
}

func (ar *AttributeResult) String() string {
	// TODO: translated string!
	return fmt.Sprintf("%v --- %v --- %v",
		ar.AttributeId,
		ar.AttributeValue["en"],
		ar.AttributeProofStatus)
}

func AttributeResultListFromDisclosed(disclosed []*CredentialInfo, conf *Configuration) *AttributeResultList {
	al := AttributeResultList{}

	for _, cred := range disclosed {
		credentialType := cred.GetCredentialType(conf)

		for _, attr := range credentialType.Attributes {
			attrId := NewAttributeTypeIdentifier(cred.CredentialTypeID.String() + "." + attr.ID)

			index, err := credentialType.IndexOf(attrId)
			if err != nil {
				// Specified credential does not contain this attribute, move to next
				break
			}

			disclosedAttributeValue := cred.Attributes[index]

			if disclosedAttributeValue != nil {
				al.Append(AttributeResult{
					AttributeValue:       disclosedAttributeValue,
					AttributeId:          attrId,
					AttributeProofStatus: UNKNOWN,
				})
			}
		}
	}
	return &al
}