Mongoose encryption middleware doesn't call after aggregation - node.js

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