feat: encrypted credential response

Signed-off-by: Andrii Holovko <andriy.holovko@gmail.com>

docs/v1/openapi.yaml

@@ -797,6 +797,9 @@ paths:
             application/json:
               schema:
                 $ref: '#/components/schemas/CredentialResponse'
+            application/jwt:
+              schema:
+                type: string
       operationId: oidc-credential
       description: Issues credentials in exchange for an authorization token.
       requestBody:
@@ -812,7 +815,7 @@ paths:
         - oidc4ci
       responses:
         '204':
-            description: Ok
+          description: Ok
         '400':
           description: Error
           content:
@@ -826,7 +829,7 @@ paths:
           application/json:
             schema:
               $ref: '#/components/schemas/AckRequest'
-      parameters: [ ]
+      parameters: []
 components:
   schemas:
     HealthCheckResponse:
@@ -919,7 +922,7 @@ components:
           type: string
           description: "URL of the Credential Issuer's Notification Endpoint. This URL MUST use the https scheme and MAY contain port, path, and query parameter components. If omitted, the Credential Issuer does not support the Notification Endpoint."
         credential_response_encryption:
-          $ref: '#/components/schemas/CredentialResponseEncryption'
+          $ref: '#/components/schemas/CredentialResponseEncryptionSupported'
         credential_identifiers_supported:
           type: boolean
           description: "Boolean value specifying whether the Credential Issuer supports returning credential_identifiers parameter in the authorization_details Token Response parameter, with true indicating support. If omitted, the default value is false."
@@ -1794,8 +1797,8 @@ components:
           type: string
           description: The "aud" claim received from the client.
         hashed_token:
-            type: string
-            description: Hashed token received from the client.
+          type: string
+          description: Hashed token received from the client.
       required:
         - tx_id
         - types
@@ -1819,8 +1822,8 @@ components:
           type: string
           description: OIDC credential format
         ack_id:
-            type: string
-            description: String identifying an issued Credential that the Wallet includes in the acknowledgement request.
+          type: string
+          description: String identifying an issued Credential that the Wallet includes in the acknowledgement request.
         retry:
           type: boolean
           description: TRUE if claim data is not yet available in the issuer OP server. This will indicate VCS OIDC to issue acceptance_token instead of credential response (Deferred Credential flow).
@@ -1838,16 +1841,38 @@ components:
       properties:
         types:
           type: array
+          description: Array of types of the credential being issued.
           items:
             type: string
-          description: Array of types of the credential being issued.
         format:
           type: string
           description: Format of the credential being issued.
         proof:
           $ref: '#/components/schemas/JWTProof'
+        credential_response_encryption:
+          $ref: '#/components/schemas/CredentialResponseEncryption'
       required:
         - types
+    CredentialResponseEncryption:
+      title: CredentialResponseEncryption
+      x-tags:
+        - oidc4ci
+      type: object
+      description: Object containing information for encrypting the Credential Response.
+      properties:
+        jwk:
+          type: string
+          description: Object containing a single public key as a JWK used for encrypting the Credential Response.
+        alg:
+          type: string
+          description: JWE alg algorithm for encrypting the Credential Response.
+        enc:
+          type: string
+          description: JWE enc algorithm for encrypting the Credential Response.
+      required:
+        - jwk
+        - alg
+        - enc
     JWTProof:
       title: JWTProof
       x-tags:
@@ -1873,7 +1898,7 @@ components:
         credentials:
           type: array
           items:
-              $ref: '#/components/schemas/AcpRequestItem'
+            $ref: '#/components/schemas/AcpRequestItem'
       required:
         - credentials
     AcpRequestItem:
@@ -1955,17 +1980,17 @@ components:
             type: string
           description: Array of case sensitive strings that identify how the Credential is bound to the identifier of the End-User who possesses the Credential.
         cryptographic_suites_supported:
-            type: array
-            items:
-              type: string
-            description: Array of case sensitive strings that identify the cryptographic suites that are supported for the cryptographic_binding_methods_supported.
+          type: array
+          items:
+            type: string
+          description: Array of case sensitive strings that identify the cryptographic suites that are supported for the cryptographic_binding_methods_supported.
         credential_definition:
-           $ref: '#/components/schemas/CredentialConfigurationsSupportedDefinition'
+          $ref: '#/components/schemas/CredentialConfigurationsSupportedDefinition'
         proof_types:
-              type: array
-              items:
-                type: string
-              description: A JSON array of case sensitive strings, each representing proof_type that the Credential Issuer supports. If omitted, the default value is jwt.
+          type: array
+          items:
+            type: string
+          description: A JSON array of case sensitive strings, each representing proof_type that the Credential Issuer supports. If omitted, the default value is jwt.
         display:
           type: array
           description: An array of objects, where each object contains the display properties of the supported credential for a certain language.
@@ -1974,7 +1999,7 @@ components:
       required:
         - format
     CredentialConfigurationsSupportedDefinition:
-      title: CredentialSupported.CredentialDefinition object definition.
+      title: CredentialConfigurationsSupportedDefinition object definition.
       x-tags:
         - issuer
       type: object
@@ -1986,11 +2011,11 @@ components:
             type: string
           description: Array designating the types a certain credential type supports
         credentialSubject:
-            type: object
-            description: An object containing a list of name/value pairs, where each name identifies a claim offered in the Credential. The value can be another such object (nested data structures), or an array of such objects.
+          type: object
+          description: An object containing a list of name/value pairs, where each name identifies a claim offered in the Credential. The value can be another such object (nested data structures), or an array of such objects.
       required:
         - type
-    CredentialResponseEncryption:
+    CredentialResponseEncryptionSupported:
       title: CredentialResponseEncryption object definition.
       x-tags:
         - issuer

pkg/restapi/v1/oidc4ci/controller.go

@@ -622,7 +622,7 @@ func (c *Controller) OidcAcknowledgement(e echo.Context) error {
 }
 
 // OidcCredential handles OIDC credential request (POST /oidc/credential).
-func (c *Controller) OidcCredential(e echo.Context) error {
+func (c *Controller) OidcCredential(e echo.Context) error { //nolint:funlen
 	req := e.Request()
 
 	ctx, span := c.tracer.Start(req.Context(), "OidcCredential")
@@ -715,13 +715,35 @@ func (c *Controller) OidcCredential(e echo.Context) error {
 	session.Extra[cNonceKey] = nonce
 	session.Extra[cNonceExpiresAtKey] = time.Now().Add(cNonceTTL).Unix()
 
-	return apiUtil.WriteOutput(e)(CredentialResponse{
+	credentialResponse := &CredentialResponse{
 		Credential:      result.Credential,
 		Format:          result.OidcFormat,
 		CNonce:          lo.ToPtr(nonce),
 		CNonceExpiresIn: lo.ToPtr(int(cNonceTTL.Seconds())),
 		AckId:           result.AckId,
-	}, nil)
+	}
+
+	if credentialRequest.CredentialResponseEncryption != nil {
+		var encryptedResponse string
+
+		if encryptedResponse, err = encryptCredentialResponse(
+			credentialResponse,
+			credentialRequest.CredentialResponseEncryption,
+		); err != nil {
+			return fmt.Errorf("encrypt credential response: %w", err)
+		}
+
+		e.Response().Header().Set("Content-Type", "application/jwt")
+		e.Response().WriteHeader(http.StatusOK)
+
+		if _, err = e.Response().Write([]byte(encryptedResponse)); err != nil {
+			return err
+		}
+
+		return nil
+	}
+
+	return apiUtil.WriteOutput(e)(credentialResponse, nil)
 }
 
 func validateCredentialRequest(e echo.Context, req *CredentialRequest) error {
@@ -745,6 +767,43 @@ func validateCredentialRequest(e echo.Context, req *CredentialRequest) error {
 	return nil
 }
 
+func encryptCredentialResponse(resp *CredentialResponse, enc *CredentialResponseEncryption) (string, error) {
+	var jwk gojose.JSONWebKey
+
+	if err := json.Unmarshal([]byte(enc.Jwk), &jwk); err != nil {
+		return "", fmt.Errorf("unmarshal jwk: %w", err)
+	}
+
+	encrypter, err := gojose.NewEncrypter(
+		gojose.ContentEncryption(enc.Enc),
+		gojose.Recipient{
+			Algorithm: gojose.KeyAlgorithm(enc.Alg),
+			Key:       &jwk,
+		},
+		nil,
+	)
+	if err != nil {
+		return "", fmt.Errorf("create encrypter: %w", err)
+	}
+
+	b, err := json.Marshal(resp)
+	if err != nil {
+		return "", fmt.Errorf("marshal credential response: %w", err)
+	}
+
+	encrypted, err := encrypter.Encrypt(b)
+	if err != nil {
+		return "", fmt.Errorf("encrypt credential response: %w", err)
+	}
+
+	jwe, err := encrypted.CompactSerialize()
+	if err != nil {
+		return "", fmt.Errorf("serialize credential response: %w", err)
+	}
+
+	return jwe, nil
+}
+
 //nolint:gocognit
 func (c *Controller) validateProofClaims(
 	clientID string,