verify.go 9.57 KB
Newer Older
1 2 3 4 5 6
package irma

import (
	"fmt"
	"math/big"
	"time"
7 8 9

	"github.com/go-errors/errors"
	"github.com/mhe/gabi"
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
)

// ProofStatus is the status of the complete proof
type ProofStatus string

const (
	VALID              = ProofStatus("VALID")
	EXPIRED            = ProofStatus("EXPIRED")
	INVALID_CRYPTO     = ProofStatus("INVALID_CRYPTO")
	INVALID_SYNTAX     = ProofStatus("INVALID_SYNTAX")
	MISSING_ATTRIBUTES = ProofStatus("MISSING_ATTRIBUTES")
)

// ProofResult is a result of a complete proof, containing all the disclosed attributes and corresponding request
type ProofResult struct {
	disjunctions []*DisclosedAttributeDisjunction
	ProofStatus  ProofStatus
}

type SignatureProofResult struct {
30
	*ProofResult
31 32 33 34 35 36 37 38 39
	message string
}

// DisclosedCredential contains raw disclosed credentials, without any extra parsing information
type DisclosedCredential struct {
	metadataAttribute *MetadataAttribute
	Attributes        map[AttributeTypeIdentifier]*big.Int
}

40 41 42 43 44 45
type DisclosedCredentialList []*DisclosedCredential

// 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
// al can be nil if you don't want to include attribute status for proof
46
func (disclosed DisclosedCredentialList) isAttributeSatisfied(attributeId AttributeTypeIdentifier, requestedValue *string) (bool, *AttributeResult) {
47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
	ar := AttributeResult{
		AttributeId: attributeId,
	}

	for _, cred := range disclosed {
		disclosedAttributeValue := cred.GetAttributeValue(attributeId)

		// Continue to next credential if requested attribute isn't disclosed in this credential
		if disclosedAttributeValue == "" {
			continue
		}

		// If this is the disclosed attribute, check if value matches
		// Attribute is satisfied if:
		// - Attribute is disclosed (i.e. not nil)
		// - Value is empty OR value equal to disclosedValue
		ar.AttributeValue = disclosedAttributeValue

65
		if requestedValue == nil || disclosedAttributeValue == *requestedValue {
66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115
			ar.AttributeProofStatus = PRESENT
			return true, &ar
		} 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
			ar.AttributeProofStatus = INVALID_VALUE
		}
	}

	// If there is never a value assigned, then this attribute isn't disclosed, and thus missing
	if ar.AttributeValue == "" {
		ar.AttributeProofStatus = MISSING
	}
	return false, &ar
}

// Create a signature proof result and check disclosed credentials against a signature request
func (disclosed DisclosedCredentialList) createAndCheckSignatureProofResult(configuration *Configuration, sigRequest *SignatureRequest) *SignatureProofResult {
	signatureProofResult := SignatureProofResult{
		ProofResult: &ProofResult{},
		message:     sigRequest.Message,
	}
	for _, content := range sigRequest.Content {
		isSatisfied, disjunction := content.SatisfyDisclosed(disclosed, configuration)
		signatureProofResult.disjunctions = append(signatureProofResult.disjunctions, disjunction)

		// If satisfied, continue to next one
		if isSatisfied {
			continue
		}

		// Else, set proof status to missing_attributes, but check other as well to add other disjunctions to result
		// (so user also knows attribute status of other disjunctions)
		signatureProofResult.ProofStatus = MISSING_ATTRIBUTES
	}

	signatureProofResult.disjunctions = addExtraAttributes(disclosed, signatureProofResult.ProofResult)
	return &signatureProofResult
}

// Returns true if one of the disclosed credentials is expired
func (disclosed DisclosedCredentialList) IsExpired() bool {
	for _, cred := range disclosed {
		if cred.IsExpired() {
			return true
		}
	}
	return false
}

116
func (proofResult *ProofResult) ToAttributeResultList() AttributeResultList {
117 118 119 120 121 122 123 124 125
	var resultList AttributeResultList

	for _, v := range proofResult.disjunctions {
		result := AttributeResult{
			AttributeValue:       v.DisclosedValue,
			AttributeId:          v.DisclosedId,
			AttributeProofStatus: v.ProofStatus,
		}

126
		resultList = append(resultList, &result)
127
	}
128
	return resultList
129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178
}

// Returns true if this attrId is present in one of the disjunctions
func (proofResult *ProofResult) ContainsAttribute(attrId AttributeTypeIdentifier) bool {
	for _, disj := range proofResult.disjunctions {
		for _, attr := range disj.Attributes {
			if attr == attrId {
				return true
			}
		}
	}

	return false
}

// Get string value of disclosed attribute, or nil if request attribute isn't disclosed in this credential
func (cred *DisclosedCredential) GetAttributeValue(id AttributeTypeIdentifier) string {
	attr := cred.Attributes[id]
	if attr != nil {
		return string(attr.Bytes())
	}

	return ""
}

func (cred *DisclosedCredential) IsExpired() bool {
	return cred.metadataAttribute.Expiry().Before(time.Now())
}

func NewDisclosedCredentialFromADisclosed(aDisclosed map[int]*big.Int, configuration *Configuration) *DisclosedCredential {
	attributes := make(map[AttributeTypeIdentifier]*big.Int)

	metadata := MetadataFromInt(aDisclosed[1], configuration) // index 1 is metadata attribute
	cred := metadata.CredentialType()

	for k, v := range aDisclosed {
		if k < 2 {
			continue
		}

		description := cred.Attributes[k-2]
		attributes[description.GetAttributeTypeIdentifier(cred.Identifier())] = v
	}

	return &DisclosedCredential{
		metadataAttribute: metadata,
		Attributes:        attributes,
	}
}

179 180
func extractPublicKeys(configuration *Configuration, proofList gabi.ProofList) ([]*gabi.PublicKey, error) {
	var publicKeys = make([]*gabi.PublicKey, 0, len(proofList))
181

182
	for _, v := range proofList {
183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198
		switch v.(type) {
		case *gabi.ProofD:
			proof := v.(*gabi.ProofD)
			metadata := MetadataFromInt(proof.ADisclosed[1], configuration) // index 1 is metadata attribute
			publicKey, err := metadata.PublicKey()
			if err != nil {
				return nil, err
			}
			publicKeys = append(publicKeys, publicKey)
		default:
			return nil, errors.New("Cannot extract public key, not a disclosure proofD!")
		}
	}
	return publicKeys, nil
}

199 200
func extractDisclosedCredentials(conf *Configuration, proofList gabi.ProofList) (DisclosedCredentialList, error) {
	var credentials = make(DisclosedCredentialList, 0, len(proofList))
201

202
	for _, v := range proofList {
203 204 205 206 207 208 209 210 211 212 213 214 215 216
		switch v.(type) {
		case *gabi.ProofD:
			proof := v.(*gabi.ProofD)
			cred := NewDisclosedCredentialFromADisclosed(proof.ADisclosed, conf)
			credentials = append(credentials, cred)
		default:
			return nil, errors.New("Cannot extract credentials from proof, not a disclosure proofD!")
		}
	}

	return credentials, nil
}

// Add extra disclosed attributes to an existing and checked ProofResult in 'dummy disjunctions'
217 218 219
func addExtraAttributes(disclosed DisclosedCredentialList, proofResult *ProofResult) []*DisclosedAttributeDisjunction {
	returnDisjunctions := make([]*DisclosedAttributeDisjunction, len(proofResult.disjunctions))
	copy(returnDisjunctions, proofResult.disjunctions)
220

221
	for _, cred := range disclosed {
222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239
		for attrId := range cred.Attributes {
			if proofResult.ContainsAttribute(attrId) {
				continue
			}

			dummyDisj := DisclosedAttributeDisjunction{
				DisclosedValue: cred.GetAttributeValue(attrId),
				DisclosedId:    attrId,
				ProofStatus:    EXTRA,
			}
			returnDisjunctions = append(returnDisjunctions, &dummyDisj)
		}
	}

	return returnDisjunctions
}

// Check an gabi prooflist against a signature proofrequest
240 241
func checkProofWithRequest(configuration *Configuration, proofList gabi.ProofList, sigRequest *SignatureRequest) *SignatureProofResult {
	disclosed, err := extractDisclosedCredentials(configuration, proofList)
242 243 244 245

	if err != nil {
		fmt.Println(err)
		return &SignatureProofResult{
246
			ProofResult: &ProofResult{
247 248 249 250 251
				ProofStatus: INVALID_CRYPTO,
			},
		}
	}

252
	signatureProofResult := disclosed.createAndCheckSignatureProofResult(configuration, sigRequest)
253 254 255 256 257 258 259 260

	// Return MISSING_ATTRIBUTES as proofstatus if one attribute is missing
	// This status takes priority over 'EXPIRED'
	if signatureProofResult.ProofStatus == MISSING_ATTRIBUTES {
		return signatureProofResult
	}

	// If all disjunctions are satisfied, check if a credential is expired
261 262 263
	if disclosed.IsExpired() {
		signatureProofResult.ProofStatus = EXPIRED
		return signatureProofResult
264 265 266 267 268 269 270 271
	}

	// All disjunctions satisfied and nothing expired, proof is valid!
	signatureProofResult.ProofStatus = VALID
	return signatureProofResult
}

// Verify an IRMA proof cryptographically
272
func verify(configuration *Configuration, proofList gabi.ProofList, context *big.Int, nonce *big.Int, isSig bool) bool {
273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291
	// Extract public keys
	pks, err := extractPublicKeys(configuration, proofList)
	if err != nil {
		return false
	}

	return proofList.Verify(pks, context, nonce, true, isSig)
}

// Verify a signature proof and check if the attributes match the attributes in the original request
func VerifySig(configuration *Configuration, proofString string, sigRequest *SignatureRequest) *SignatureProofResult {

	// First, unmarshal proof and check if all the attributes in the proofstring match the signature request
	var proofList gabi.ProofList
	proofBytes := []byte(proofString)

	err := proofList.UnmarshalJSON(proofBytes)
	if err != nil {
		return &SignatureProofResult{
292
			ProofResult: &ProofResult{
293 294 295 296 297 298
				ProofStatus: INVALID_SYNTAX,
			},
		}
	}

	// Now, cryptographically verify the signature
299
	if !verify(configuration, proofList, sigRequest.GetContext(), sigRequest.GetNonce(), true) {
300
		return &SignatureProofResult{
301
			ProofResult: &ProofResult{
302 303 304 305 306 307
				ProofStatus: INVALID_CRYPTO,
			},
		}
	}

	// Finally, check whether attribute values in proof satisfy the original signature request
308
	return checkProofWithRequest(configuration, proofList, sigRequest)
309
}