Mongoose encryption middleware doesn't call after aggregation

Question

I have a mongoose's schema with a 'mongoose-encryption' plugin, for example:

let someSchema = new Schema({name, age});

someSchema.plugin(mongoose-encryption, {
        encryptionKey: 'eKey',
        signingKey: 'sKey',
        encryptedFields: ['age'],
        decryptPostSave: false
    });

After initiating the model and the repository I tried to aggregate some query:

let aggregation = []; // just return all the docs.
someModel.aggregate(aggregation, (err, persons) => {
        return persons;
});

As a result I'm still getting the age field encrypted, little reading has revealed that the 'post' method of the 'init' event isn't called after aggregation (as explained here - Mongoose Middleware Docs).

Is there a good solution? or any other workaround?

• the data MUST be encrypt.

• the aggregation is also required (in real life - lookup to other collection)

Answer 1

As I didn't find a better answer, I changed my code (as workaround unfortunately) to decrypt the object by myself - using the code of mongoose-encryption to decrypt after the aggregation has finished.

Most of the code was taken from GitHub (called decryptOne in my code): decryptSync function of mongoose-encryption

The 'tricky' thing was to decrypt the inner lookup value - the inner document also has the "_ct" field that should be decrypted.

let lookup: { [innerField: string]: string[]; } = {
                    user: ['bio']
                };
this.decryptAggregation(aggregationResult, lookup);

My function gets a dictionary of the known lookup collection and its wanted fields after decryption. In that example, the other collection named users and its encrypted field is just his bio.

decryptAggregation(res: any[], innerLookup: { [innerField: string]: string[]; }) {
    for (let doc of res) {
        this.decryptSync(doc, innerLookup);
    }
}

private decryptSync(doc: any, innerLookup: { [innerField: string]: string[]; }) {
    this.decryptOne(doc, this.encryptedFields);
    for (let innerObj in innerLookup) {
        if (innerLookup.hasOwnProperty(innerObj)) {
            this.decryptOne(doc[innerObj], innerLookup[innerObj]);
        }
    }
};

private decryptOne(doc: any, fields: string[]) {
    let ct, ctWithIV, decipher, iv, idString, decryptedObject, decryptedObjectJSON, decipheredVal;

    if (doc._ct) {
        ctWithIV = doc._ct.hasOwnProperty('buffer') ? doc._ct.buffer : doc._ct;
        iv = ctWithIV.slice(this.VERSION_LENGTH, this.VERSION_LENGTH + this.IV_LENGTH);
        ct = ctWithIV.slice(this.VERSION_LENGTH + this.IV_LENGTH, ctWithIV.length);

        decipher = crypto.createDecipheriv(this.ENCRYPTION_ALGORITHM, this.encryptionKey, iv);
        try {
            decryptedObjectJSON = decipher.update(ct, undefined, 'utf8') + decipher.final('utf8');
            decryptedObject = JSON.parse(decryptedObjectJSON);
        } catch (err) {
            if (doc._id) {
                idString = doc._id.toString();
            } else {
                idString = 'unknown';
            }
            throw new Error('Error parsing JSON during decrypt of ' + idString + ': ' + err);
        }

        fields.forEach((field) => {
            decipheredVal = mpath.get(field, decryptedObject);

            //JSON.parse returns {type: "Buffer", data: Buffer} for Buffers
            //https://nodejs.org/api/buffer.html#buffer_buf_tojson
            if (_.isObject(decipheredVal) && decipheredVal.type === "Buffer") {
                this.setFieldValue(doc, field, decipheredVal.data);
            } else {
                this.setFieldValue(doc, field, decipheredVal);
            }
        });

        doc._ct = undefined;
        doc._ac = undefined;
    }
}

After those function I got my wanted object fully decrypted, the last thing to do was to project the wanted fields back to the client - with lodash.pick