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.
Try to genegarate HMAC on JS with CryptoJS lib from UTF8 string with UTF8 secret. Like PHP hash_hmac('sha1','...','...',true);
PHP :
$buf = ' accept';
$bufferedSecret = '��xDx�����4�J�?)#';
hash_hmac('sha1', $buf, $bufferedSecret, false);
/* d301cae776ed8c5d46ac93bd7441b01af4d1b888 */
hash_hmac('sha1', $buf, $bufferedSecret, true);
/* ���v�]F���tA��Ѹ� */
JavaScript :
var buf = ' accept';
var bufferedSecret = '��xDx�����4�J�?)#';
CryptoJS.HmacSHA1(buf, bufferedSecret).toString();
/* d301cae776ed8c5d46ac93bd7441b01af4d1b888 */
var forBase64 = CryptoJS.HmacSHA1(buf, bufferedSecret);
CryptoJS.enc.Base64.stringify(forBase64);
/* 0wHK53btjF1GrJO9dEGwGvTRuIg= */
How get same HMAC(SHA1) UTF8 value on JS?
I was found a way for get UTF-8 RAW.
Used "convertWordArrayToUint8Array()" from here:
https://gist.github.com/getify/7325764
and just decode it.
var wordArr = CryptoJS.HmacSHA1(buf, bufferedSecret);
var utf8Arr = convertWordArrayToUint8Array(wordArr);
var string = new TextDecoder('utf-8').decode(utf8Arr);
Buffer to UTF8
You can take your Buffer and convert it to UTF-8 in JavaScript using the toString method; make sure you specify which format in the parameters, suitable values are hex and utf8, read more here.
var buf = ' accept';
var bufferedSecret = '��xDx�����4�J�?) #';
CryptoJS.HmacSHA1(buf, bufferedSecret).toString('utf8');
I would like to concatenate a hex value and a string using JavaScript.
var hexValue = 0x89;
var png = "PNG";
The string "PNG" is equivalent to the concatenation of 0x50, 0x4E, and 0x47.
Concatenating hexValue and png via
var concatHex = String.fromCharCode(0x89) + String.fromCharCode(0x50)
+ String.fromCharCode(0x4E) + String.fromCharCode(0x47);
...give a result with a byte count of 5 because of the first hex value needing a control character:
C2 89 50 4E 47
I am working with raw image data where I have hexValue and png and need to concatenate them without this control character being included.
Is there a way to trim off the control character?
Given I have an array of bytes, is there a better way to concatenate them and a string while preserving the bytes?
Well i was investigating and i found that in javascript to achieve this eficienly JavaScript typed arrays is used.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays
http://msdn.microsoft.com/en-us/library/br212485(v=vs.94).aspx
Here i wrote a code (not tested) to perform what you want:
var png = "PNG";
var hexValue = 0x89;
var lenInBytes = (png.Length + 1) * 8; //left an extra space to concat hexValue
var buffer = new ArrayBuffer(lenInBytes); //create chunk of memory whose bytes are all pre-initialized to 0
var int8View = new Int8Array(buffer); //treat this memory like int8
for(int i = 0; i < png.Length ; i++)
int8View[i] = png[i] //here convert the png[i] to bytes
//at this point we have the string png as array of bytes
int8View[png.Length] = hexValue //here the concatenation is performed
Well hope it helps.
I am working with the FatSecret REST API
Im using the OAuthSimple javascript library to generate the signed url.
Here's the code I have -
params['oauth_timestamp'] = Math.floor(new Date().getTime()/1000);
params['oauth_nonce'] = '1234';
params['oauth_version'] = '1.0';
var paramStr = '';
for(var key in params){
paramStr += key+"="+params[key]+"&";
}
paramStr = paramStr.substring(0,paramStr.length-1);
var oauth = OAuthSimple();
oauth.setAction('GET');
var o = oauth.sign(
{
path:this.requestURL,
parameters: paramStr,
signatures:{
api_key:this.apiKey,
shared_secret:this.sharedSecret,
access_token: this.accessToken,
access_secret: this.accessSecret
}
});
console.log(o.signed_url);
return o.signed_url;
params is an associative array containing all the non oauth related parameters for this call.
When I use this signed url I get an "invalid/used nonce"
The OAuth Testing Tool uses the same OAuthSimple library and if I put in all the same parameters (including the timestamp) it generates exactly the same url.
The only difference is that the url generated by the testing tool works and gives me the full response from the server. The url generated by my code does't.
I tried various nonce values including sending a MD5 of the timestamp but I get the same error. The reason I'm using 1234 right now is that the testing tool uses 1234 by default and that seems to work.
Any help is appreciated. Thanks in advance.
Updating #Saravanan's answer with something that works on current browsers:
function genNonce() {
const charset = '0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz-._~'
const result = [];
window.crypto.getRandomValues(new Uint8Array(32)).forEach(c =>
result.push(charset[c % charset.length]));
return result.join('');
}
console.info(genNonce());
The nonce value as per twitter documentation:
The value for this request was generated by base64 encoding 32 bytes of random data, and stripping out all non-word characters, but any
approach which produces a relatively random alphanumeric string should
be OK here.
Based on the above notes, I use the following javascript code to generate nonce value each time I send a request:
var nonceLen = 32;
return crypto.randomBytes(Math.ceil(nonceLen * 3 / 4))
.toString('base64') // convert to base64 format
.slice(0, nonceLen) // return required number of characters
.replace(/\+/g, '0') // replace '+' with '0'
.replace(/\//g, '0'); // replace '/' with '0'
Try this if it works!
Try this
This works every time
var nonce = Math.random().toString(36).replace(/[^a-z]/, '').substr(2);
So I am building a java script that is used in conjunction of my C++ application for sending direct messages to users. the script does the work of building the request that i send. When i send a request i receive "Incorrect signature" or "can not authenticate you" Does anyone see something i am missing or am doing wrong? I am continuing to investigate. Thank you in advance
Javascript:
var nDate = new Date();
var epoch = nDate.getTime();
var nounce = "";
nounce = Base64.encode(epoch+randomString());
var Parameters = [
"oauth_consumerkey="+sConsumerKey,
"oauth_nonce="+nounce,
"oauth_signature_method=HMAC-SHA1",
"oauth_timestamp="+epoch,
"oauth_token="+sAccessToken,
"oauth_version=1.0",
"text="+sText,
"user="+sUser];
var SortedParameters = Parameters.sort();
var joinParameters = SortedParameters.join("&");
var encodeParameters = escape(joinParameters);
signature_base_string = escape("POST&"+NormalizedURL+"&"+encodeParameters);
signature_key = sConsumerSecret+"&"+sAccessSecret;
signature = Base64.encode(hmacsha1(signature_base_string,signature_key));
sAuthHeader = "
OAuth realm=,
oauth_nonce="+nounce+",
oauth_timestamp="+epoch+",
oauth_consumer_key="+sConsumerKey+",
oauth_signature_method=HMAC-SHA1,
oauth_version=1.0,
oauth_signature="+signature+",
oauth_token="+sAccessToken+",
text="+sText;
goNVOut.Set("Header.Authorization: ", sAuthHeader);
Here are a couple things to be careful about:
JavaScript's "escape" function will not work for OAuth URL encoding, as per the OAuth Spec.
5.1. Parameter Encoding
All parameter names and values are
escaped using the [RFC3986]
percent-encoding (%xx) mechanism.
Characters not in the unreserved
character set ([RFC3986] section 2.3)
MUST be encoded. Characters in the
unreserved character set MUST NOT be
encoded. Hexadecimal characters in
encodings MUST be upper case. Text
names and values MUST be encoded as
UTF-8 octets before percent-encoding
them per [RFC3629].
unreserved = ALPHA, DIGIT, '-', '.', '_', '~'
JavaScript's escape function will let # * + / through, unescaped. I'm confident that that will break the signature signing process, since the server will be escaping those, and the HMAC-SHA1 value it computes will be different than yours.
Be sure to URL encode your base URI, NormalizedURL, as well.
I found that getting the encoding correct is the most tedious part of OAuth. Be sure to use upper-case letters in your new "url_encode" function.
Here's my C++ code to do the URL encoding. It could be optimized a bit but should be easy to understand.
char hexdigit(int ch)
{
assert(ch < 16);
assert(ch >= 0);
if (ch >= 10)
return 'A' + ch - 10;
return '0' + ch;
}
std::string url_encode(const std::string &to_encode)
{
std::stringstream ss;
for (std::string::const_iterator ich = to_encode.begin();
ich != to_encode.end();
++ich)
{
unsigned char ch = (unsigned char)*ich;
if (isalpha(ch) || isdigit(ch) || ch == '-' || ch == '_' || ch == '.' || ch == '~')
{
ss << ch;
}
else
{
ss << '%';
ss << hexdigit(ch >> 4);
ss << hexdigit(ch & 0xf);
}
}
std::string encoded = ss.str();
return encoded;
}
Best of luck!