how to use node-ffi with the crypt32.dll and CryptProtectData/CryptUnprotectData functions?

i want to use the node-ffi libary with the windows crypt32.dll to use data protection api and the functions “CryptProtectData” and “CryptUnprotectData”: (https://msdn.microsoft.com/de-de/library/windows/desktop/aa380261(v=vs.85).aspx).

i tried the following:

var crypt32 = new FFI.Library('crypt32',
{
   'CryptProtectData': [
      'int32', [ 'string', 'string', 'string', 'string', 'string', 'string', 'string' ]
   ]
});

but i am not sure in which way to use the variable types. how can i use the c++ type “DATA_BLOB” or a pointer in nodejs?

can you post a working sample for that case? thank you.

[magengbin]

I try …

const fs = require('fs'); 
const ref = require('ref');
const ffi = require('ffi');
const Struct = require('ref-struct')
const Array = require('ref-array')
const DATA_BLOB = Struct({
    cbData: ref.types.uint32,
    pbData: 'string' // ref.refType(ref.types.byte)
})
const PDATA_BLOB = new ref.refType(DATA_BLOB)
const Crypto = new ffi.Library('Crypt32', {
    'CryptUnprotectData': ['bool', [PDATA_BLOB, 'string', 'string', 'void *', 'string', 'int', PDATA_BLOB]],
});
const data_blob_input = new DATA_BLOB();
data_blob_input.cbData = row.encrypted_value.length;
data_blob_input.pbData = row.encrypted_value;
const data_blob_output = new DATA_BLOB();
const result = Crypto.CryptUnprotectData(data_blob_input.ref(), null, null, null, null, 0, data_blob_output.ref());
cookies[row.name] = data_blob_output.pbData.slice(0, data_blob_output.cbData);
console.log(row.name, cookies[row.name])

It is working ok.

[Wackerberg]

Below is a complete example that worked for me.

const fs = require("fs");
const ref = require("ref");
const ffi = require("ffi");
const Struct = require("ref-struct");

const DATA_BLOB = Struct({
    cbData: ref.types.uint32,
    pbData: ref.refType(ref.types.byte)
});
const PDATA_BLOB = new ref.refType(DATA_BLOB);
const Crypto = new ffi.Library('Crypt32', {
    "CryptUnprotectData": ['bool', [PDATA_BLOB, 'string', 'string', 'void *', 'string', 'int', PDATA_BLOB]],
    "CryptProtectData" : ['bool', [PDATA_BLOB, 'string', 'string', 'void *', 'string', 'int', PDATA_BLOB]]
});

function encrypt(plaintext) {
    let buf = Buffer.from(plaintext, 'utf16le');
    let dataBlobInput = new DATA_BLOB();
    dataBlobInput.pbData = buf;
    dataBlobInput.cbData = buf.length;
    let dataBlobOutput = ref.alloc(DATA_BLOB);
    let result = Crypto.CryptProtectData(dataBlobInput.ref(), null, null, null, null, 0, dataBlobOutput);    
    let outputDeref = dataBlobOutput.deref();
    let ciphertext = ref.reinterpret(outputDeref.pbData, outputDeref.cbData, 0);
    return ciphertext.toString('base64');
};

function decrypt(ciphertext) {
    let buf = Buffer.from(ciphertext, 'base64');
    let dataBlobInput = new DATA_BLOB();
    dataBlobInput.pbData = buf;
    dataBlobInput.cbData = buf.length;
    let dataBlobOutput = ref.alloc(DATA_BLOB);
    let result = Crypto.CryptUnprotectData(dataBlobInput.ref(), null, null, null, null, 0, dataBlobOutput);
    let outputDeref = dataBlobOutput.deref();
    let plaintext = ref.reinterpret(outputDeref.pbData, outputDeref.cbData, 0);
    return plaintext.toString('utf16le');
};

let text = "åäöÅÄÖ_éÉóÓ D25P";
let ciphertext = encrypt(text);
let plaintext = decrypt(ciphertext);

console.log("text:", text);
console.log("ciphertext:", ciphertext);
console.log("plaintext:", plaintext);