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authenticode.js new computes the new checksum on sign/unsign.

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Ylian Saint-Hilaire 2022-06-08 00:27:32 -07:00
parent 86429258dd
commit f5f4305841
1 changed files with 92 additions and 13 deletions
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105
authenticode.js
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@ -244,9 +244,6 @@ function createAuthenticodeHandler(path) {
obj.header.siglen = obj.header.dataDirectories.certificateTable.size
obj.header.signed = ((obj.header.sigpos != 0) && (obj.header.siglen != 0));
// Compute the checkSum value for this file
obj.header.peWindows.checkSumActual = getChecksum(readFileSlice(0, obj.filesize));
// The section headers are located after the optional PE header
obj.header.SectionHeadersPtr = obj.header.peOptionalHeaderLocation + obj.header.coff.sizeOfOptionalHeader;
@ -272,6 +269,9 @@ function createAuthenticodeHandler(path) {
obj.header.sections[sectionName] = section;
}
// Compute the checkSum value for this file
obj.header.peWindows.checkSumActual = runChecksum();
// If there is a .rsrc section, read the resource information and locations
if (obj.header.sections['.rsrc'] != null) {
obj.resources = readResourceTable(obj.header.sections['.rsrc'].rawAddr, 0); // Read all resources recursively
@ -742,18 +742,85 @@ function createAuthenticodeHandler(path) {
while (ptr < end) { const buf = readFileSlice(ptr, Math.min(65536, end - ptr)); hash.update(buf); ptr += buf.length; }
}
// Compute the PE checksum of an entire file
function getChecksum(data) {
var checksum = 0, top = Math.pow(2, 32);
// Checksum the file loading 64k chunks
function runChecksum() {
var ptr = 0, c = createChecksum();
while (ptr < obj.filesize) { const buf = readFileSlice(ptr, Math.min(65536, obj.filesize - ptr)); c.update(buf); ptr += buf.length; }
return c.digest();
}
// Checksum the open file loading 64k chunks
function runChecksumOnFile(fd, filesize) {
var ptr = 0, c = createChecksum(), buf = Buffer.alloc(65536);
while (ptr < filesize) { var len = fs.readSync(fd, buf, 0, Math.min(65536, filesize - ptr), ptr); c.update(buf, len); ptr += len; }
return c.digest();
}
// Steaming checksum methods
// TODO: Works only with files padded to 4 byte.
function createChecksum() {
const obj = { checksum: 0, length: 0 };
obj.update = function (data, len) {
if (!len) { len = data.length; }
for (var i = 0; i < (len / 4) ; i++) {
if (((obj.length / 4) + i) == 54) continue; // Skip PE checksum location
const dword = data.readUInt32LE(i * 4);
var checksumlo = (obj.checksum > 4294967296) ? (obj.checksum - 4294967296) : obj.checksum;
var checksumhi = (obj.checksum > 4294967296) ? 1 : 0;
obj.checksum = checksumlo + dword + checksumhi;
if (obj.checksum > 4294967296) {
checksumlo = (obj.checksum > 4294967296) ? (obj.checksum - 4294967296) : obj.checksum;
checksumhi = (obj.checksum > 4294967296) ? 1 : 0;
obj.checksum = checksumlo + checksumhi;
}
}
obj.length += len;
}
obj.digest = function () {
obj.checksum = (obj.checksum & 0xffff) + (obj.checksum >>> 16);
obj.checksum = (obj.checksum) + (obj.checksum >>> 16);
obj.checksum = obj.checksum & 0xffff;
obj.checksum += obj.length;
return obj.checksum;
}
return obj;
}
// Simple checksum method that works on a complete file at once
// TODO: Works only with files padded to 4 byte.
function updateChecksum(data) {
var checksum = 0;
for (var i = 0; i < (data.length / 4) ; i++) {
if (i == 54) continue; // Skip PE checksum location
var dword = data.readUInt32LE(i * 4);
var checksumlo = (checksum > top) ? (checksum - top) : checksum;
var checksumhi = (checksum > top) ? 1 : 0;
var checksumlo = (checksum > 4294967296) ? (checksum - 4294967296) : checksum;
var checksumhi = (checksum > 4294967296) ? 1 : 0;
checksum = checksumlo + dword + checksumhi;
if (checksum > top) {
checksumlo = (checksum > top) ? (checksum - top) : checksum;
checksumhi = (checksum > top) ? 1 : 0;
if (checksum > 4294967296) {
checksumlo = (checksum > 4294967296) ? (checksum - 4294967296) : checksum;
checksumhi = (checksum > 4294967296) ? 1 : 0;
checksum = checksumlo + checksumhi;
}
}
checksum = (checksum & 0xffff) + (checksum >>> 16);
checksum = (checksum) + (checksum >>> 16);
checksum = checksum & 0xffff;
checksum += data.length;
return checksum;
}
// Compute the PE checksum of an entire file
function getChecksum(data) {
var checksum = 0;
for (var i = 0; i < (data.length / 4) ; i++) {
if (i == 54) continue; // Skip PE checksum location
var dword = data.readUInt32LE(i * 4);
var checksumlo = (checksum > 4294967296) ? (checksum - 4294967296) : checksum;
var checksumhi = (checksum > 4294967296) ? 1 : 0;
checksum = checksumlo + dword + checksumhi;
if (checksum > 4294967296) {
checksumlo = (checksum > 4294967296) ? (checksum - 4294967296) : checksum;
checksumhi = (checksum > 4294967296) ? 1 : 0;
checksum = checksumlo + checksumhi;
}
}
@ -816,7 +883,7 @@ function createAuthenticodeHandler(path) {
// Open the output file
var output = null;
try { output = fs.openSync(args.out, 'w'); } catch (ex) { }
try { output = fs.openSync(args.out, 'w+'); } catch (ex) { }
if (output == null) return false;
var tmp, written = 0;
var executableSize = obj.header.sigpos ? obj.header.sigpos : this.filesize;
@ -853,6 +920,12 @@ function createAuthenticodeHandler(path) {
fs.writeSync(output, win);
fs.writeSync(output, p7signature);
if (padding > 0) { fs.writeSync(output, Buffer.alloc(padding, 0)); }
written += p7signature.length + padding + 8;
// Compute the checksum and write it in the PE header at position (54 * 4)
var tmp = Buffer.alloc(4);
tmp.writeUInt32LE(runChecksumOnFile(output, written));
fs.writeSync(output, tmp, 0, 4, 54 * 4);
// Close the file
fs.closeSync(output);
@ -862,7 +935,7 @@ function createAuthenticodeHandler(path) {
// Save an executable without the signature
obj.unsign = function (args) {
// Open the file
var output = fs.openSync(args.out, 'w');
var output = fs.openSync(args.out, 'w+');
var written = 0, totalWrite = obj.header.sigpos;
// Compute pre-header length and copy that to the new file
@ -881,6 +954,12 @@ function createAuthenticodeHandler(path) {
fs.writeSync(output, tmp);
written += tmp.length;
}
// Compute the checksum and write it in the PE header at position (54 * 4)
var tmp = Buffer.alloc(4);
tmp.writeUInt32LE(runChecksumOnFile(output, written));
fs.writeSync(output, tmp, 0, 4, 54 * 4);
fs.closeSync(output);
}