I need to convert a base64 encode string into an ArrayBuffer.
The base64 strings are user input, they will be copy and pasted from an email, so they're not there when the page is loaded.
I would like to do this in javascript without making an ajax call to the server if possible.
I found those links interesting, but they didt'n help me:
ArrayBuffer to base64 encoded string
this is about the opposite conversion, from ArrayBuffer to base64, not the other way round
http://jsperf.com/json-vs-base64/2
this looks good but i can't figure out how to use the code.
Is there an easy (maybe native) way to do the conversion? thanks
Try this:
function _base64ToArrayBuffer(base64) {
var binary_string = window.atob(base64);
var len = binary_string.length;
var bytes = new Uint8Array(len);
for (var i = 0; i < len; i++) {
bytes[i] = binary_string.charCodeAt(i);
}
return bytes.buffer;
}
Using TypedArray.from:
Uint8Array.from(atob(base64_string), c => c.charCodeAt(0))
Performance to be compared with the for loop version of Goran.it answer.
For Node.js users:
const myBuffer = Buffer.from(someBase64String, 'base64');
myBuffer will be of type Buffer which is a subclass of Uint8Array. Unfortunately, Uint8Array is NOT an ArrayBuffer as the OP was asking for. But when manipulating an ArrayBuffer I almost always wrap it with Uint8Array or something similar, so it should be close to what's being asked for.
Goran.it's answer does not work because of unicode problem in javascript - https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding.
I ended up using the function given on Daniel Guerrero's blog: http://blog.danguer.com/2011/10/24/base64-binary-decoding-in-javascript/
Function is listed on github link: https://github.com/danguer/blog-examples/blob/master/js/base64-binary.js
Use these lines
var uintArray = Base64Binary.decode(base64_string);
var byteArray = Base64Binary.decodeArrayBuffer(base64_string);
Async solution, it's better when the data is big:
// base64 to buffer
function base64ToBufferAsync(base64) {
var dataUrl = "data:application/octet-binary;base64," + base64;
fetch(dataUrl)
.then(res => res.arrayBuffer())
.then(buffer => {
console.log("base64 to buffer: " + new Uint8Array(buffer));
})
}
// buffer to base64
function bufferToBase64Async( buffer ) {
var blob = new Blob([buffer], {type:'application/octet-binary'});
console.log("buffer to blob:" + blob)
var fileReader = new FileReader();
fileReader.onload = function() {
var dataUrl = fileReader.result;
console.log("blob to dataUrl: " + dataUrl);
var base64 = dataUrl.substr(dataUrl.indexOf(',')+1)
console.log("dataUrl to base64: " + base64);
};
fileReader.readAsDataURL(blob);
}
Javascript is a fine development environment so it seems odd than it doesn't provide a solution to this small problem. The solutions offered elsewhere on this page are potentially slow. Here is my solution. It employs the inbuilt functionality that decodes base64 image and sound data urls.
var req = new XMLHttpRequest;
req.open('GET', "data:application/octet;base64," + base64Data);
req.responseType = 'arraybuffer';
req.onload = function fileLoaded(e)
{
var byteArray = new Uint8Array(e.target.response);
// var shortArray = new Int16Array(e.target.response);
// var unsignedShortArray = new Int16Array(e.target.response);
// etc.
}
req.send();
The send request fails if the base 64 string is badly formed.
The mime type (application/octet) is probably unnecessary.
Tested in chrome. Should work in other browsers.
Pure JS - no string middlestep (no atob)
I write following function which convert base64 in direct way (without conversion to string at the middlestep). IDEA
get 4 base64 characters chunk
find index of each character in base64 alphabet
convert index to 6-bit number (binary string)
join four 6 bit numbers which gives 24-bit numer (stored as binary string)
split 24-bit string to three 8-bit and covert each to number and store them in output array
corner case: if input base64 string ends with one/two = char, remove one/two numbers from output array
Below solution allows to process large input base64 strings. Similar function for convert bytes to base64 without btoa is HERE
function base64ToBytesArr(str) {
const abc = [..."ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"]; // base64 alphabet
let result = [];
for(let i=0; i<str.length/4; i++) {
let chunk = [...str.slice(4*i,4*i+4)]
let bin = chunk.map(x=> abc.indexOf(x).toString(2).padStart(6,0)).join('');
let bytes = bin.match(/.{1,8}/g).map(x=> +('0b'+x));
result.push(...bytes.slice(0,3 - (str[4*i+2]=="=") - (str[4*i+3]=="=")));
}
return result;
}
// --------
// TEST
// --------
let test = "Alice's Adventure in Wonderland.";
console.log('test string:', test.length, test);
let b64_btoa = btoa(test);
console.log('encoded string:', b64_btoa);
let decodedBytes = base64ToBytesArr(b64_btoa); // decode base64 to array of bytes
console.log('decoded bytes:', JSON.stringify(decodedBytes));
let decodedTest = decodedBytes.map(b => String.fromCharCode(b) ).join``;
console.log('Uint8Array', JSON.stringify(new Uint8Array(decodedBytes)));
console.log('decoded string:', decodedTest.length, decodedTest);
Caution!
If you want to decode base64 to STRING (not bytes array) and you know that result contains utf8 characters then atob will fail in general e.g. for character 💩 the atob("8J+SqQ==") will give wrong result . In this case you can use above solution and convert result bytes array to string in proper way e.g. :
function base64ToBytesArr(str) {
const abc = [..."ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"]; // base64 alphabet
let result = [];
for(let i=0; i<str.length/4; i++) {
let chunk = [...str.slice(4*i,4*i+4)]
let bin = chunk.map(x=> abc.indexOf(x).toString(2).padStart(6,0)).join('');
let bytes = bin.match(/.{1,8}/g).map(x=> +('0b'+x));
result.push(...bytes.slice(0,3 - (str[4*i+2]=="=") - (str[4*i+3]=="=")));
}
return result;
}
// --------
// TEST
// --------
let testB64 = "8J+SqQ=="; // for string: "💩";
console.log('input base64 :', testB64);
let decodedBytes = base64ToBytesArr(testB64); // decode base64 to array of bytes
console.log('decoded bytes :', JSON.stringify(decodedBytes));
let result = new TextDecoder("utf-8").decode(new Uint8Array(decodedBytes));
console.log('properly decoded string :', result);
let result_atob = atob(testB64);
console.log('decoded by atob :', result_atob);
Snippets tested 2022-08-04 on: chrome 103.0.5060.134 (arm64), safari 15.2, firefox 103.0.1 (64 bit), edge 103.0.1264.77 (arm64), and node-js v12.16.1
I would strongly suggest using an npm package implementing correctly the base64 specification.
The best one I know is rfc4648
The problem is that btoa and atob use binary strings instead of Uint8Array and trying to convert to and from it is cumbersome. Also there is a lot of bad packages in npm for that. I lose a lot of time before finding that one.
The creators of that specific package did a simple thing: they took the specification of Base64 (which is here by the way) and implemented it correctly from the beginning to the end. (Including other formats in the specification that are also useful like Base64-url, Base32, etc ...) That doesn't seem a lot but apparently that was too much to ask to the bunch of other libraries.
So yeah, I know I'm doing a bit of proselytism but if you want to avoid losing your time too just use rfc4648.
I used the accepted answer to this question to create base64Url string <-> arrayBuffer conversions in the realm of base64Url data transmitted via ASCII-cookie [atob, btoa are base64[with +/]<->js binary string], so I decided to post the code.
Many of us may want both conversions and client-server communication may use the base64Url version (though a cookie may contain +/ as well as -_ characters if I understand well, only ",;\ characters and some wicked characters from the 128 ASCII are disallowed). But a url cannot contain / character, hence the wider use of b64 url version which of course not what atob-btoa supports...
Seeing other comments, I would like to stress that my use case here is base64Url data transmission via url/cookie and trying to use this crypto data with the js crypto api (2017) hence the need for ArrayBuffer representation and b64u <-> arrBuff conversions... if array buffers represent other than base64 (part of ascii) this conversion wont work since atob, btoa is limited to ascii(128). Check out an appropriate converter like below:
The buff -> b64u version is from a tweet from Mathias Bynens, thanks for that one (too)! He also wrote a base64 encoder/decoder:
https://github.com/mathiasbynens/base64
Coming from java, it may help when trying to understand the code that java byte[] is practically js Int8Array (signed int) but we use here the unsigned version Uint8Array since js conversions work with them. They are both 256bit, so we call it byte[] in js now...
The code is from a module class, that is why static.
//utility
/**
* Array buffer to base64Url string
* - arrBuff->byte[]->biStr->b64->b64u
* #param arrayBuffer
* #returns {string}
* #private
*/
static _arrayBufferToBase64Url(arrayBuffer) {
console.log('base64Url from array buffer:', arrayBuffer);
let base64Url = window.btoa(String.fromCodePoint(...new Uint8Array(arrayBuffer)));
base64Url = base64Url.replaceAll('+', '-');
base64Url = base64Url.replaceAll('/', '_');
console.log('base64Url:', base64Url);
return base64Url;
}
/**
* Base64Url string to array buffer
* - b64u->b64->biStr->byte[]->arrBuff
* #param base64Url
* #returns {ArrayBufferLike}
* #private
*/
static _base64UrlToArrayBuffer(base64Url) {
console.log('array buffer from base64Url:', base64Url);
let base64 = base64Url.replaceAll('-', '+');
base64 = base64.replaceAll('_', '/');
const binaryString = window.atob(base64);
const length = binaryString.length;
const bytes = new Uint8Array(length);
for (let i = 0; i < length; i++) {
bytes[i] = binaryString.charCodeAt(i);
}
console.log('array buffer:', bytes.buffer);
return bytes.buffer;
}
made a ArrayBuffer from a base64:
function base64ToArrayBuffer(base64) {
var binary_string = window.atob(base64);
var len = binary_string.length;
var bytes = new Uint8Array(len);
for (var i = 0; i < len; i++) {
bytes[i] = binary_string.charCodeAt(i);
}
return bytes.buffer;
}
I was trying to use above code and It's working fine.
The result of atob is a string that is separated with some comma
,
A simpler way is to convert this string to a json array string and after that parse it to a byteArray
below code can simply be used to convert base64 to an array of number
let byteArray = JSON.parse('['+atob(base64)+']');
let buffer = new Uint8Array(byteArray);
Solution without atob
I've seen many people complaining about using atob and btoa in the replies. There are some issues to take into account when using them.
There's a solution without using them in the MDN page about Base64. Below you can find the code to convert a base64 string into a Uint8Array copied from the docs.
Note that the function below returns a Uint8Array. To get the ArrayBuffer version you just need to do uintArray.buffer.
function b64ToUint6(nChr) {
return nChr > 64 && nChr < 91
? nChr - 65
: nChr > 96 && nChr < 123
? nChr - 71
: nChr > 47 && nChr < 58
? nChr + 4
: nChr === 43
? 62
: nChr === 47
? 63
: 0;
}
function base64DecToArr(sBase64, nBlocksSize) {
const sB64Enc = sBase64.replace(/[^A-Za-z0-9+/]/g, "");
const nInLen = sB64Enc.length;
const nOutLen = nBlocksSize
? Math.ceil(((nInLen * 3 + 1) >> 2) / nBlocksSize) * nBlocksSize
: (nInLen * 3 + 1) >> 2;
const taBytes = new Uint8Array(nOutLen);
let nMod3;
let nMod4;
let nUint24 = 0;
let nOutIdx = 0;
for (let nInIdx = 0; nInIdx < nInLen; nInIdx++) {
nMod4 = nInIdx & 3;
nUint24 |= b64ToUint6(sB64Enc.charCodeAt(nInIdx)) << (6 * (3 - nMod4));
if (nMod4 === 3 || nInLen - nInIdx === 1) {
nMod3 = 0;
while (nMod3 < 3 && nOutIdx < nOutLen) {
taBytes[nOutIdx] = (nUint24 >>> ((16 >>> nMod3) & 24)) & 255;
nMod3++;
nOutIdx++;
}
nUint24 = 0;
}
}
return taBytes;
}
If you're interested in the reverse operation, ArrayBuffer to base64, you can find how to do it in the same link.
I have 2 piece of codes.
1ST ONE
const hash1 = (data) => createHash('sha256').update(data).digest('hex');
var a1 = hash1("A");
var b1 = hash1("B");
console.log(hash1(a1+b1));
2ND ONE
const hash2 = (data) => createHash('sha256').update(data).digest();
var a2 = hash2("A");
var b2 = hash2("B");
console.log(hash2(Buffer.concat([a2,b2])).toString('hex'));
Why do they print the different results ?
digest('hex') and digest() are the same , but in different kind of format, but still the same. So, why do I get different results in console ? is it the + operator when I sum up the hexes versus when i sum up buffers ? why ?
The default encoding for hash.digest([encoding]) is utf-8. utf-8 is a variable-length encoding system. It will only use as many bytes as necessary to represent each character (anywhere between 1-4 bytes).
However, when you specify hex as the encoding, each character is stored as exactly 2 hexadecimal characters.
When you call hash.toString('hex') on a utf-8 encoded hash, the resulting hex representation is equivalent to hashing with hex encoding in the first place (as in hash.digest('hex')).
So, even though the hex representation is the same in each case, the actual data is different. i.e.:
hash.digest() != hash.digest('hex'), but
hash.digest().toString('hex') == hash.digest('hex').
digest('hex') and digest() technically different
Please try this code
var crypto = require('crypto');
const hash1 = (data) => crypto.createHash('sha256').update(data).digest('hex');
var a1 = hash1("A");
var b1 = hash1("B");
//console.log(a1)
//console.log(b1)
console.log(hash1(a1+b1));
const hash2 = (data) => crypto.createHash('sha256').update(data).digest();
var a2 = hash2("A");
var b2 = hash2("B");
//console.log(a2.toString("hex"))
//console.log(b2.toString("hex"))
console.log(hash2(a2.toString("hex") + b2.toString("hex") ).toString("hex"));
In the first you are appending two hex string and passing to hash1
In the second you are appending two non hex string and passing to hash2
Run Nodejs online
I am following the solutions from here:
How can I return a JavaScript string from a WebAssembly function
and here:
How to return a string (or similar) from Rust in WebAssembly?
However, when reading from memory I am not getting the desired results.
AssemblyScript file, helloWorldModule.ts:
export function getMessageLocation(): string {
return "Hello World";
}
index.html:
<script>
fetch("helloWorldModule.wasm").then(response =>
response.arrayBuffer()
).then(bytes =>
WebAssembly.instantiate(bytes, {imports: {}})
).then(results => {
var linearMemory = results.instance.exports.memory;
var offset = results.instance.exports.getMessageLocation();
var stringBuffer = new Uint8Array(linearMemory.buffer, offset, 11);
let str = '';
for (let i=0; i<stringBuffer.length; i++) {
str += String.fromCharCode(stringBuffer[i]);
}
debugger;
});
</script>
This returns an offset of 32. And finally yields a string that starts too early and has spaces between each letter of "Hello World":
However, if I change the array to an Int16Array, and add 8 to the offset (which was 32), to make an offset of 40. Like so:
<script>
fetch("helloWorldModule.wasm").then(response =>
response.arrayBuffer()
).then(bytes =>
WebAssembly.instantiate(bytes, {imports: {}})
).then(results => {
var linearMemory = results.instance.exports.memory;
var offset = results.instance.exports.getMessageLocation();
var stringBuffer = new Int16Array(linearMemory.buffer, offset+8, 11);
let str = '';
for (let i=0; i<stringBuffer.length; i++) {
str += String.fromCharCode(stringBuffer[i]);
}
debugger;
});
</script>
Then we get the correct result:
Why does the first set of code not work like its supposed to in the links I provided? Why do I need to change it to work with Int16Array to get rid of the space between "H" and "e" for example? Why do I need to add 8 bytes to the offset?
In summary, what on earth is going on here?
Edit: Another clue, is if I use a TextDecoder on the UInt8 array, decoding as UTF-16 looks more correct than decoding as UTF-8:
AssemblyScript uses utf-16: https://github.com/AssemblyScript/assemblyscript/issues/43
Additionally AssemblyScript stores the length of the string in the first 32 or 64 bits.
That's why my code behaves differently. The examples in the links at the top of this post were for C++ and Rust, which do string encoding differently
I am trying to use RNCryptor-JS which uses SJCL but for some reason, SJCL bit array concatenation does not seem to work.
var SALT_SIZE = 64/8;
var plaintext = "Hello, World!";
var password = "myPassword";
function keyForPassword(password, salt){
// Using CryptoJS for pbkdf2, aes, sha256, and random word arrays
var pbkdf2_key = CryptoJS.PBKDF2(
password,
salt,
{
keySize: 256/32,
iterations: 1000,
hasher: CryptoJS.algo.SHA256
}
);
return pbkdf2_key;
}
var encryption_salt = CryptoJS.lib.WordArray.random(SALT_SIZE);
var encryption_key = keyForPassword(password, encryption_salt);
var hmac_salt = CryptoJS.lib.WordArray.random(SALT_SIZE);
var hmac_key = keyForPassword(password, hmac_salt);
var iv = CryptoJS.lib.WordArray.random(128/8);
var version = sjcl.codec.hex.toBits("03");
var options = sjcl.codec.hex.toBits("01");
var message = sjcl.bitArray.concat(version, iv);
message = sjcl.bitArray.concat(message, encryption_salt);
message = sjcl.bitArray.concat(message, hmac_salt);
message = sjcl.bitArray.concat(message, iv);
// Progressive cipher
var aesEncryptor = CryptoJS.algo.AES.createEncryptor(encryption_key, {iv: iv});
var ciphertext = aesEncryptor.process(plaintext);
message = sjcl.bitArray.concat(message, ciphertext);
var hmac = new sjcl.misc.hmac(hmac_key).encrypt(message);
var encrypted_data = sjcl.bitArray.concat(message, hmac);
var output = sjcl.codec.hex.fromBits(encrypted_data);
console.log(output);
When I log the output of message after the first set of sjcl.bitArray.concat is done, all that returns is the first concatenation of version and iv. The final hex output is just that first concatenation and hmac concatenated. This reinforces my suspicion that it might be CryptoJS's fault because the output concatenation works and is between two sjcl variables.
I tried using SJCL random bit arrays but had some trouble. SJCL's generator, prng, did not work when using
new sjcl.prng.randomWords(32/4);
or
new sjcl.prng(32/4);
And sjcl.random.randomWords does not seem to work anymore.
CryptoJS (WordArray) and SJCL (bitArray) have different internal representations of data. You can't simply concatenate them.
The easiest way would be probably to encode it into an intermediate format such as Hex and let the other side decode into its internal format:
message = sjcl.bitArray.concat(version, sjcl.codec.hex.toBits(iv.toString()));
WordArray#toString() automatically uses Hex encoding. You would have to do this for all lines, but this is a little overkill, since you can concatenate Hex strings as strings:
message = sjcl.codec.hex.toBits("03" + iv + encryption_salt + hmac_salt + iv);
This should work as expected, because adding a WordArray such as iv to a string automatically calls its toString() function which in turn produces a big-endian hex-encoded string.
I wonder why you're using iv twice. Perhaps you meant options on one of them.
What needs to change:
function convert(wordArray){
return sjcl.codec.hex.toBits(wordArray.toString());
}
var message = "0301" + encryption_salt + hmac_salt + iv;
var ciphertext = CryptoJS.AES.encrypt(plaintext, encryption_key, {iv: iv}).ciphertext;
message += ciphertext;
message = sjcl.codec.hex.toBits(message);
var hmac = new sjcl.misc.hmac(convert(hmac_key)).encrypt(message);
var encrypted_data = sjcl.bitArray.concat(message, hmac);
var output = sjcl.codec.hex.fromBits(encrypted_data);
console.log(output);
NOTE: Yes, I understand there is a lot of code in this message, but you do encourage us to show prior research and how we've been trying.
Let me preface this by saying, I am not interested in the security of this function. All I want is to encrypt and decrypt arbitrarily long messages using RSA. Usually to do this, the message is encrypted using a block cipher (such as AES) and encrypting the key with the RSA cipher. However, I am just trying to find the easiest way to encrypt/decrypt long messages, irregardless of security. Hence why I am using RC4 in place of the block cipher.
Now, I can encrypt properly using the following code:
function encryptLong(signedCert, msg) {
var key256Bits = CryptoJS.SHA256("password");
var ciphertext = CryptoJS.RC4.encrypt(msg, key256Bits);
key = new RSAKey();
var m = CryptoJS.SHA256("password").toString(CryptoJS.enc.Hex);
m = new BigInteger(m, 16);
key.setPublic(signedCert.msg.subject.pk.n, signedCert.msg.subject.pk.e);
var ctxt = key.doPublic(m).toString(16);
var cipherstring = ciphertext + ":" + ctxt;
var obj = { "type": "CTXT-LONG", "encrypted": cipherstring };
return JSON.stringify(obj);
}
The message and the key are encrypted properly. I tested them individually using these functions.
function encryptRSA(signedCert, msg) {
//create a new RSA key object
var key = new RSAKey();
//convert ASCII message to hex
var m = asciiToHex(msg);
// create new BigInterger from m
m = new BigInteger(m, 16);
// set the values for the public key
key.setPublic(signedCert.msg.subject.pk.n, signedCert.msg.subject.pk.e);
// compute the RSA public key operation, and convert to a hex value
var ctxt = key.doPublic(m).toString(16);
//enter ctxt into the JSON obj
var obj = { "type": "CTXT-SHORT", "c": ctxt };
return JSON.stringify(obj);
}
And...
function encryptRSA(password, message) {
var key256Bits = CryptoJS.SHA256(password);
var ciphertext = CryptoJS.RC4.encrypt(CryptoJS.enc.Utf8.parse(message), key256Bits);
return ciphertext;
}
Now, here is our decryption code:
function decryptLong(sk, ctxt) {
key = new RSAKey();
encryptedStuff = JSON.stringify(ctxt.encrypted);
log(encryptedStuff);
splitEncryptedstuff = encryptedStuff.split(":");
rsaencryption = splitEncryptedstuff[1];
log(rsaencryption);
rc4encryption = splitEncryptedstuff[0];
log(rc4encryption);
c = new BigInteger(rsaencryption, 16);
key.setPrivate(sk.n, sk.e, sk.d);
var key256Bits = key.doPrivate(c).toString(16);
log(key256Bits);
// RC4 decryption
var message = CryptoJS.RC4.decrypt(rc4encryption, key224Bits);
// var ptxt = CryptoJS.enc.Utf8.stringify(message);
// log(ptxt);
return CryptoJS.enc.Utf8.stringify(message);
}
This code doesn't decrypt properly, but I know parts of it work. For example, where I have
log(key356Bits);
it returns the key exactly. So I know that at least the RSA decryption works. What I don't understand is, I followed the decryption function that I have exactly. Which is as follows.
function decryptRC4(password, ciphertext) {
var key256Bits = CryptoJS.SHA256(password);
var message = CryptoJS.RC4.decrypt(ciphertext, key256Bits);
return CryptoJS.enc.Utf8.stringify(message);
}
Well not exactly, I don't have to take the Hash of the password to get the key, as I already have the key. But, I still don't understand what is not working. When we decrypt our ciphertext using this individual function, the plaintext is correct.
Any assistance in this matter would be greatly appreciated.
Knowing my luck, it's probably just something annoying like it's in the wrong encoding type thing.