I'm attempting to encrypt a Blob of a PDF file and save it in the localStorage for later decryption when offline.
My AngularJS app uses forge for encryption.
Below is the code to download the PDF file:
$http.get(url, {
headers: {
"Application-Authorization": appContext.user.token
},
responseType: "blob"
}).then(function(response) {
backendCipherService.encryptPDF(response.data, appContext.user.password).then(function(data) {
$localForage.setItem("document::" + document.documentId + "::pdf", data.json).then(function(success) {
console.log("cached pdf", document.documentId);
deferred.resolve();
}, function(error) {
console.log("Error", response.data, document.documentName);
deferred.reject(error);
});
});
}, function(error) {
deferred.reject(error);
});Here is the code for encryption and decryption (backendCipherService):
this.encryptPDF = function(blob, password) {
var salt = forge.random.getBytesSync(256);
var key = forge.pkcs5.pbkdf2(password, salt, 40, 32);
var iv = forge.random.getBytesSync(32);
var cipher = forge.cipher.createCipher('AES-CBC', key);
cipher.start({iv: iv});
var deferred = $q.defer();
var uint8Array = null;
var arrayBuffer = null;
var fileReader = new FileReader();
fileReader.onload = function(progressEvent) {
arrayBuffer = this.result;
uint8Array = new Uint8Array(arrayBuffer);
};
fileReader.readAsArrayBuffer(blob);
fileReader.onloadend = function() {
var inp = uint8Array;
console.log(inp);
cipher.update(forge.util.createBuffer(inp));
cipher.finish();
var encrypted = cipher.output;
var data = forge.util.bytesToHex(encrypted);
var obj = {"salt": forge.util.bytesToHex(salt), "iv": forge.util.bytesToHex(iv), "encrypted": data};
deferred.resolve({
json: angular.toJson(obj)
});
};
return deferred.promise;
};
this.decryptPDF = function(json, password) {
var obj = angular.fromJson(json);
var key = forge.pkcs5.pbkdf2(password, forge.util.hexToBytes(obj.salt), 40, 32);
var iv = forge.util.createBuffer();
var data = forge.util.createBuffer();
iv.putBytes(forge.util.hexToBytes(obj.iv));
data.putBytes(forge.util.hexToBytes(obj.encrypted));
var decipher = forge.cipher.createDecipher('AES-CBC', key);
decipher.start({iv: iv});
decipher.update(data);
decipher.finish();
return decipher.output.data;
};And here is the code to convert the decrypted value back to a Blob:
return $localForage.getItem("document::" + documentId + "::pdf").then(function(pdf) {
var pdfBlob = new Blob([backendCipherService.decryptPDF(pdf, appContext.user.password)], {type: 'application/pdf'});
return pdfBlob;
}, function(error) {
return error;
});While this generally works, I'm unable to read the PDF using PDF.js and encountering the following error:
Error: Bad FCHECK in flate stream: 120, 194
pdf.worker.js:252 at error (http://localhost:8080/client/components/pdfjs-dist/build/pdf.worker.js:252:15)
at Object.FlateStream (http://localhost:8080/client/components/pdfjs-dist/build/pdf.worker.js:31394:7)
at Object.Parser_makeFilter [as makeFilter] (http://localhost:8080/client/components/pdfjs-dist/build/pdf.worker.js:30281:18)
... (error continues)
pdf.worker.js:235 Warning: Unsupported feature "unknown"
pdf.worker.js:235 Warning: Invalid stream: "Error: Bad FCHECK in flate stream: 120, 194"It seems the PDF is somehow corrupted.
Any insights on what might be going wrong? Thanks