WebCrypto promises don't seem to be getting called

Question

My code:

var keyData = `-----BEGIN PRIVATE KEY-----
...
-----END PRIVATE KEY-----`;

var ciphertext = '...';

// from https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/importKey#PKCS_8_import
function str2ab(str) {
    const buf = new ArrayBuffer(str.length);
    const bufView = new Uint8Array(buf);
    for (let i = 0, strLen = str.length; i < strLen; i++) {
        bufView[i] = str.charCodeAt(i);
    }
    return buf;
}

keyData = keyData
    .replace(/-+[^-]+-+/g, '')
    .replace("\n", '')
    .replace("\r", '');
keyData = str2ab(window.atob(keyData));

window.crypto.subtle.importKey(
   'pkcs8',
    keyData,
    {name: 'RSA-OAEP'},
    true,
    'decrypt'
).then(function(privateKey) {
alert('this far');
    window.crypto.subtle.decrypt(
    {
      name: "RSA-OAEP"
    },
    privateKey,
    ciphertext
  ).then(function(plaintext) {
      alert(plaintext);
  })
});

Here it is on JSFiddle (with the full private key and ciphertext):

https://jsfiddle.net/akcq65o7/1/

According to the documentation window.crypto.subtle.importKey returns a Promise, hence the then(). BUT the alert('this far'); line isn't ever being called. I'm not getting any errors in the JS console, either.

Any ideas?

Answer 1

There are a few minor issues in the script, which I marked in the posted code below:

var keyData = `-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----`;

var ciphertext = 'Sv99/pCslCtU+yAxV0dR+JyQ7yfiVF7+MCHErQEMSL7CyEndKikU7Al0IiRDx6Bd/PmKR6j0mU7WXISptZA1uE82jdDEAhcs9mQtdX18Or4OceIGcqHcHDCZWFQygHI0VMbywVv5C18ydFDuGvHL/dga9ji8IbFW393sEfjx6JtV8Nl4+yiEbee/+dBSQTg+E98asW1Tg59HUNc/fE1r7Muw6hgl7eiF/GxndYg7O957LNH4T3Vi6qutG4mP0frGJ3za6RNkuRrO5Wud3WnDOndHNAoLW7cuMyvzXzfhh3YMPqmkKtRsChJkV+DfPU8HdALfuyP/botQnUGCmwanKg==';

// from https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/importKey#PKCS_8_import
function str2ab(str) {
    const buf = new ArrayBuffer(str.length);
    const bufView = new Uint8Array(buf);
    for (let i = 0, strLen = str.length; i < strLen; i++) {
        bufView[i] = str.charCodeAt(i);
    }
    return buf;
}

keyData = keyData
    .replace(/-+[^-]+-+/g, '')
    .replace("\n", '')
    .replace("\r", '');
keyData = str2ab(window.atob(keyData));

window.crypto.subtle.importKey(
    'pkcs8',
    keyData,
    {
        name: 'RSA-OAEP', 
        hash: "SHA-256"                                     // Fix 1: Set digest
    },                                                      
    true,
    ['decrypt']                                             // Fix 2: Use brackets [...]
).then(function(privateKey) {
    console.log('this far');
    window.crypto.subtle.decrypt(
        {
            name: "RSA-OAEP"
        },
        privateKey,
        str2ab(window.atob(ciphertext))                     // Fix 3: Base64 decode ciphertext and load into ArrayBuffer
    ).then(function(plaintext) {
        console.log(new TextDecoder().decode(plaintext));   // Fix 4: UTF-8 decode plaintext
    })
});