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MeshCentral/authenticode.js

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/**
* @description Authenticode parsing
* @author Bryan Roe & Ylian Saint-Hilaire
* @copyright Intel Corporation 2018-2022
* @license Apache-2.0
* @version v0.0.1
*/
function createAuthenticodeHandler(path) {
const obj = {};
const fs = require('fs');
const crypto = require('crypto');
const forge = require('node-forge');
const pki = forge.pki;
const p7 = forge.pkcs7;
obj.header = { path: path }
// Read a file slice
function readFileSlice(start, length) {
var buffer = Buffer.alloc(length);
var len = fs.readSync(obj.fd, buffer, 0, buffer.length, start);
if (len < buffer.length) { buffer = buffer.slice(0, len); }
return buffer;
}
// Close the file
obj.close = function () {
if (obj.fd == null) return;
fs.closeSync(obj.fd);
delete obj.fd;
}
// Private OIDS
obj.Oids = {
SPC_INDIRECT_DATA_OBJID: '1.3.6.1.4.1.311.2.1.4',
SPC_STATEMENT_TYPE_OBJID: '1.3.6.1.4.1.311.2.1.11',
SPC_SP_OPUS_INFO_OBJID: '1.3.6.1.4.1.311.2.1.12',
SPC_INDIVIDUAL_SP_KEY_PURPOSE_OBJID: '1.3.6.1.4.1.311.2.1.21',
SPC_COMMERCIAL_SP_KEY_PURPOSE_OBJID: '1.3.6.1.4.1.311.2.1.22',
SPC_MS_JAVA_SOMETHING: '1.3.6.1.4.1.311.15.1',
SPC_PE_IMAGE_DATA_OBJID: '1.3.6.1.4.1.311.2.1.15',
SPC_CAB_DATA_OBJID: '1.3.6.1.4.1.311.2.1.25',
SPC_TIME_STAMP_REQUEST_OBJID: '1.3.6.1.4.1.311.3.2.1',
SPC_SIPINFO_OBJID: '1.3.6.1.4.1.311.2.1.30',
SPC_PE_IMAGE_PAGE_HASHES_V1: '1.3.6.1.4.1.311.2.3.1',
SPC_PE_IMAGE_PAGE_HASHES_V2: '1.3.6.1.4.1.311.2.3.2',
SPC_NESTED_SIGNATURE_OBJID: '1.3.6.1.4.1.311.2.4.1',
SPC_RFC3161_OBJID: '1.3.6.1.4.1.311.3.3.1'
}
// Open the file and read header information
function openFile() {
if (obj.fd != null) return;
// Open the file descriptor
obj.path = path;
obj.fd = fs.openSync(path);
obj.stats = fs.fstatSync(obj.fd);
obj.filesize = obj.stats.size;
if (obj.filesize < 64) { throw ('File too short.'); }
// Read the PE header size
var buf = readFileSlice(60, 4);
obj.header.header_size = buf.readUInt32LE(0);
// Check file size and PE header
if (obj.filesize < (160 + obj.header.header_size)) { throw ('Invalid SizeOfHeaders.'); }
if (readFileSlice(obj.header.header_size, 4).toString('hex') != '50450000') { throw ('Invalid PE File.'); }
// Check header magic data
var magic = readFileSlice(obj.header.header_size + 24, 2).readUInt16LE(0);
switch (magic) {
case 0x20b: obj.header.pe32plus = 1; break;
case 0x10b: obj.header.pe32plus = 0; break;
default: throw ('Invalid Magic in PE');
}
// Read PE header information
obj.header.pe_checksum = readFileSlice(obj.header.header_size + 88, 4).readUInt32LE(0);
obj.header.numRVA = readFileSlice(obj.header.header_size + 116 + (obj.header.pe32plus * 16), 4).readUInt32LE(0);
buf = readFileSlice(obj.header.header_size + 152 + (obj.header.pe32plus * 16), 8);
obj.header.sigpos = buf.readUInt32LE(0);
obj.header.siglen = buf.readUInt32LE(4);
obj.header.signed = ((obj.header.sigpos != 0) && (obj.header.siglen != 0));
if (obj.header.signed) {
// Read signature block
// Check if the file size allows for the signature block
if (obj.filesize < (obj.header.sigpos + obj.header.siglen)) { throw ('Executable file too short to contain the signature block.'); }
// Remove the padding if needed
var i, pkcs7raw = readFileSlice(obj.header.sigpos + 8, obj.header.siglen - 8);
var derlen = forge.asn1.getBerValueLength(forge.util.createBuffer(pkcs7raw.slice(1, 5))) + 4;
if (derlen != pkcs7raw.length) { pkcs7raw = pkcs7raw.slice(0, derlen); }
//console.log('pkcs7raw', pkcs7raw.toString('base64'));
// Decode the signature block
var pkcs7der = forge.asn1.fromDer(forge.util.createBuffer(pkcs7raw));
// To work around ForgeJS PKCS#7 limitation
// Switch content type from 1.3.6.1.4.1.311.2.1.4 to forge.pki.oids.data (1.2.840.113549.1.7.1)
// TODO: Find forge.asn1.oidToDer('1.3.6.1.4.1.311.2.1.4').data and switch it.
pkcs7der.value[1].value[0].value[2].value[0].value = forge.asn1.oidToDer(forge.pki.oids.data).data;
// Convert the ASN1 content data into binary and place back
var pkcs7content = forge.asn1.toDer(pkcs7der.value[1].value[0].value[2].value[1].value[0]).data;
pkcs7der.value[1].value[0].value[2].value[1].value[0] = { tagClass: 0, type: 4, constructed: false, composed: false, value: pkcs7content };
// DEBUG: Print out the new DER
//console.log(Buffer.from(forge.asn1.toDer(pkcs7der).data, 'binary').toString('base64'));
// Decode the PKCS7 message
var pkcs7 = p7.messageFromAsn1(pkcs7der);
var pkcs7content = forge.asn1.fromDer(pkcs7.rawCapture.content.value[0].value);
obj.rawSignedContent = pkcs7.rawCapture.content.value[0].value;
//console.log('p7content', JSON.stringify(pkcs7content));
// DEBUG: Print out the content
//console.log(Buffer.from(pkcs7.rawCapture.content.value[0].value, 'binary').toString('hex'));
// Set the certificate chain
obj.certificates = pkcs7.certificates;
// Get the file hashing algorithm
var hashAlgoOid = forge.asn1.derToOid(pkcs7content.value[1].value[0].value[0].value);
switch (hashAlgoOid) {
case forge.pki.oids.sha256: { obj.fileHashAlgo = 'sha256'; break; }
case forge.pki.oids.sha384: { obj.fileHashAlgo = 'sha384'; break; }
case forge.pki.oids.sha512: { obj.fileHashAlgo = 'sha512'; break; }
case forge.pki.oids.sha224: { obj.fileHashAlgo = 'sha224'; break; }
case forge.pki.oids.md5: { obj.fileHashAlgo = 'md5'; break; }
}
// Get the signed file hash
obj.fileHashSigned = Buffer.from(pkcs7content.value[1].value[1].value, 'binary')
// Compute the actual file hash
if (obj.fileHashAlgo != null) { obj.fileHashActual = getHash(obj.fileHashAlgo); }
}
}
// Hash the file using the selected hashing system
function getHash(algo) {
var hash = crypto.createHash(algo);
runHash(hash, 0, obj.header.header_size + 88);
runHash(hash, obj.header.header_size + 88 + 4, obj.header.header_size + 152 + (obj.header.pe32plus * 16));
runHash(hash, obj.header.header_size + 152 + (obj.header.pe32plus * 16) + 8, obj.header.sigpos > 0 ? obj.header.sigpos : obj.filesize);
return hash.digest();
}
// Hash the file from start to end loading 64k chunks
function runHash(hash, start, end) {
var ptr = start;
while (ptr < end) { const buf = readFileSlice(ptr, Math.min(65536, end - ptr)); hash.update(buf); ptr += buf.length; }
}
// Generate a test self-signed certificate with code signing extension
obj.createSelfSignedCert = function () {
var keys = pki.rsa.generateKeyPair(2048);
var cert = pki.createCertificate();
cert.publicKey = keys.publicKey;
cert.serialNumber = '00000001';
cert.validity.notBefore = new Date();
cert.validity.notAfter = new Date();
cert.validity.notAfter.setFullYear(cert.validity.notBefore.getFullYear() + 3);
var attrs = [
{ name: 'commonName', value: 'example.org' },
{ name: 'countryName', value: 'US' },
{ shortName: 'ST', value: 'California' },
{ name: 'localityName', value: 'Santa Clara' },
{ name: 'organizationName', value: 'Test' },
{ shortName: 'OU', value: 'Test' }
];
cert.setSubject(attrs);
cert.setIssuer(attrs);
cert.setExtensions([{ name: 'basicConstraints', cA: false }, { name: 'keyUsage', keyCertSign: false, digitalSignature: true, nonRepudiation: false, keyEncipherment: false, dataEncipherment: false }, { name: 'extKeyUsage', codeSigning: true }, { name: "subjectKeyIdentifier" }]);
cert.sign(keys.privateKey, forge.md.sha384.create());
return { cert: cert, key: keys.privateKey };
}
// Sign the file using the certificate and key. If none is specified, generate a dummy one
obj.sign = function (cert, key) {
if ((cert == null) || (key == null)) { var c = obj.createSelfSignedCert(); cert = c.cert; key = c.key; }
var fileHash = getHash('sha384');
var p7 = forge.pkcs7.createSignedData();
p7.content = forge.asn1.toDer({ "tagClass": 0, "type": 16, "constructed": true, "composed": true, "value": [{ "tagClass": 0, "type": 16, "constructed": true, "composed": true, "value": [{ "tagClass": 0, "type": 6, "constructed": false, "composed": false, "value": forge.asn1.oidToDer("1.3.6.1.4.1.311.2.1.15").data }, { "tagClass": 0, "type": 16, "constructed": true, "composed": true, "value": [{ "tagClass": 0, "type": 3, "constructed": false, "composed": false, "value": "\u0000", "bitStringContents": "\u0000", "original": { "tagClass": 0, "type": 3, "constructed": false, "composed": false, "value": "\u0000" } }, { "tagClass": 128, "type": 0, "constructed": true, "composed": true, "value": [{ "tagClass": 128, "type": 2, "constructed": true, "composed": true, "value": [{ "tagClass": 128, "type": 0, "constructed": false, "composed": false, "value": "" }] }] }] }] }, { "tagClass": 0, "type": 16, "constructed": true, "composed": true, "value": [{ "tagClass": 0, "type": 16, "constructed": true, "composed": true, "value": [{ "tagClass": 0, "type": 6, "constructed": false, "composed": false, "value": forge.asn1.oidToDer(forge.pki.oids.sha384).data }, { "tagClass": 0, "type": 5, "constructed": false, "composed": false, "value": "" }] }, { "tagClass": 0, "type": 4, "constructed": false, "composed": false, "value": fileHash.toString('binary') }] }] });
p7.addCertificate(cert);
p7.addSigner({
key: key,
certificate: cert,
digestAlgorithm: forge.pki.oids.sha384,
authenticatedAttributes:
[
{ type: obj.Oids.SPC_INDIRECT_DATA_OBJID, },
{ type: forge.pki.oids.contentType, value: forge.pki.oids.data },
{ type: forge.pki.oids.messageDigest }, // value will be auto-populated at signing time
{ type: forge.pki.oids.signingTime, value: new Date() } // value can also be auto-populated at signing time
]
});
p7.sign();
var p7signature = Buffer.from(forge.pkcs7.messageToPem(p7).split('-----BEGIN PKCS7-----')[1].split('-----END PKCS7-----')[0], 'base64');
// Correct the signed data type
// Decode the signature block
var pkcs7der = forge.asn1.fromDer(forge.util.createBuffer(p7signature.toString('binary')));
// To work around ForgeJS PKCS#7 limitation
// Switch content type from 1.2.840.113549.1.7.1 to forge.pki.oids.data (1.3.6.1.4.1.311.2.1.4)
pkcs7der.value[1].value[0].value[2].value[0].value = forge.asn1.oidToDer('1.3.6.1.4.1.311.2.1.4').data;
// Convert the ASN1 content data into binary and place back
var pkcs7content = forge.asn1.fromDer(forge.util.createBuffer(Buffer.from(pkcs7der.value[1].value[0].value[2].value[1].value[0].value, 'binary').toString('binary')));
pkcs7der.value[1].value[0].value[2].value[1].value = [ pkcs7content ];
p7signature = Buffer.from(forge.asn1.toDer(pkcs7der).data, 'binary');
// Create the output filename
var outputFileName = this.path.split('.');
outputFileName[outputFileName.length - 2] += '-jsigned';
outputFileName = outputFileName.join('.');
// Open the file
var output = fs.openSync(outputFileName, 'w');
var tmp, written = 0;
var executableSize = obj.header.sigpos ? obj.header.sigpos : this.filesize;
// Compute pre-header length and copy that to the new file
var preHeaderLen = (obj.header.header_size + 152 + (obj.header.pe32plus * 16));
var tmp = readFileSlice(written, preHeaderLen);
fs.writeSync(output, tmp);
written += tmp.length;
// Quad Align the results, adding padding if necessary
var len = executableSize + p7signature.length;
var padding = (8 - ((len) % 8)) % 8;
// Write the signature header
var addresstable = Buffer.alloc(8);
addresstable.writeUInt32LE(executableSize);
addresstable.writeUInt32LE(8 + p7signature.length + padding, 4);
fs.writeSync(output, addresstable);
written += addresstable.length;
// Copy the rest of the file until the start of the signature block
while ((executableSize - written) > 0) {
tmp = readFileSlice(written, Math.min(executableSize - written, 65536));
fs.writeSync(output, tmp);
written += tmp.length;
}
// Write the signature block header and signature
var win = Buffer.alloc(8); // WIN CERTIFICATE Structure
win.writeUInt32LE(p7signature.length + padding + 8); // DWORD length
win.writeUInt16LE(512, 4); // WORD revision
win.writeUInt16LE(2, 6); // WORD type
fs.writeSync(output, win);
fs.writeSync(output, p7signature);
if (padding > 0) { fs.writeSync(output, Buffer.alloc(padding, 0)); }
// Close the file
fs.closeSync(output);
}
// Save an executable without the signature
obj.unsign = function (cert, key) {
// Create the output filename
var outputFileName = this.path.split('.');
outputFileName[outputFileName.length - 2] += '-junsigned';
outputFileName = outputFileName.join('.');
// Open the file
var output = fs.openSync(outputFileName, 'w');
var written = 0, totalWrite = obj.header.sigpos;
// Compute pre-header length and copy that to the new file
var preHeaderLen = (obj.header.header_size + 152 + (obj.header.pe32plus * 16));
var tmp = readFileSlice(written, preHeaderLen);
fs.writeSync(output, tmp);
written += tmp.length;
// Write the new signature header
fs.writeSync(output, Buffer.alloc(8));
written += 8;
// Copy the rest of the file until the start of the signature block
while ((totalWrite - written) > 0) {
tmp = readFileSlice(written, Math.min(totalWrite - written, 65536));
fs.writeSync(output, tmp);
written += tmp.length;
}
fs.closeSync(output);
}
openFile();
return obj;
}
function start() {
// Show tool help
if (process.argv.length < 4) {
console.log("MeshCentral Authenticode Tool.");
console.log("Usage:");
console.log(" node authenticode.js [command] [exepath]");
console.log("Commands:");
console.log(" info - Show information about an executable.");
console.log(" sign - Sign an executable using a dummy certificate.");
console.log(" unsign - Remove the signature from the executable.");
return;
}
// Check that a valid command is passed in
if (['info', 'sign', 'unsign'].indexOf(process.argv[2].toLowerCase()) == -1) {
console.log("Invalid command: " + process.argv[2]);
return;
}
// Check the file exists
var stats = null;
try { stats = require('fs').statSync(process.argv[3]); } catch (ex) { }
if (stats == null) {
console.log("Unable to open file: " + process.argv[3]);
return;
}
// Open the file
var exe = createAuthenticodeHandler(process.argv[3]);
// Execute the command
var command = process.argv[2].toLowerCase();
if (command == 'info') {
console.log('Header', exe.header);
if (exe.fileHashAlgo != null) { console.log('fileHashMethod', exe.fileHashAlgo); }
if (exe.fileHashSigned != null) { console.log('fileHashSigned', exe.fileHashSigned.toString('hex')); }
if (exe.fileHashActual != null) { console.log('fileHashActual', exe.fileHashActual.toString('hex')); }
if (exe.signatureBlock) { console.log('Signature', exe.signatureBlock.toString('hex')); }
console.log('FileLen: ' + exe.filesize);
}
if (command == 'sign') {
console.log('Signing...'); exe.sign(); console.log('Done.');
}
if (command == 'unsign') {
if (exe.header.signed) { console.log('Unsigning...'); exe.unsign(); console.log('Done.'); } else { console.log('Executable is not signed.'); }
}
// Close the file
exe.close();
}
start();
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