Initial commit

memoryScanner.js

@@ -0,0 +1,74 @@
+const fs = require("fs");
+
+function findPatternInBuffer(buffer, bytesRead, signature, mask) {
+    const bufferLength = bytesRead + signature.length - 1;
+
+    for (let i = 0; i <= bytesRead - signature.length; i++) {
+        if (isMatch(buffer, signature, mask, i)) return i;
+    }
+
+    return -1;
+}
+
+
+function isMatch(buffer, signature, mask, offset) {
+    for (let i = 0; i < signature.length; i++) {
+        if (mask[i] === "x" && buffer[offset + i] !== signature[i]) return false;
+    }
+    return true;
+}
+
+function parseSignature(signature) {
+    const signatureBytes = [];
+    let mask = "";
+
+    const tokens = signature.split(" ");
+    tokens.forEach((token) => {
+        if (token === "??" || token === "?") {
+            signatureBytes.push(0);
+            mask += "?";
+        } else {
+            signatureBytes.push(parseInt(token, 16));
+            mask += "x";
+        }
+    });
+
+    return { signature: Buffer.from(signatureBytes), mask };
+}
+
+
+async function patchBySignature(filePath, functionSignature, patchBytes, patchOffset) {
+    const { signature, mask } = parseSignature(functionSignature);
+
+    const bufferSize = 8192;
+    const buffer = Buffer.alloc(bufferSize + signature.length - 1);
+
+    const fileHandle = await fs.promises.open(filePath, "r+");
+
+    let filePosition = 0;
+    try {
+        while (true) {
+            const { bytesRead } = await fileHandle.read(buffer, 0, bufferSize, filePosition);
+            if (bytesRead === 0) break;
+
+            const matchIndex = findPatternInBuffer(buffer, bytesRead, signature, mask);
+            if (matchIndex !== -1) {
+                const functionStartPosition = filePosition + matchIndex;
+
+                // Go to patch position
+                await fileHandle.write(Buffer.from(patchBytes), 0, patchBytes.length, functionStartPosition + patchOffset);
+
+                return functionStartPosition; // Return the address of the function start by signature
+            }
+
+            filePosition += bytesRead;
+            buffer.copy(buffer, 0, bufferSize, bufferSize + signature.length - 1);
+        }
+    } finally {
+        await fileHandle.close();
+    }
+
+    return -1;
+}
+
+module.exports = patchBySignature;