From 453774dc91d1fc3a7119223d2dc637c1303f0e82 Mon Sep 17 00:00:00 2001
From: Khabalov Pavel <khabalov.pv@phystech.edu>
Date: Tue, 30 Apr 2024 14:35:40 +0300
Subject: [PATCH] =?UTF-8?q?=D0=94=D0=BE=D0=B1=D0=B0=D0=B2=D0=B8=D0=BB=20?=
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---
 tasks/reverse/server/khabalov.c | 51 +++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 tasks/reverse/server/khabalov.c

diff --git a/tasks/reverse/server/khabalov.c b/tasks/reverse/server/khabalov.c
new file mode 100644
index 0000000..df27d7e
--- /dev/null
+++ b/tasks/reverse/server/khabalov.c
@@ -0,0 +1,51 @@
+#include <time.h>
+#include <stdio.h>
+#include <stdlib.h>
+#define _GNU_SOURCE
+#include <string.h>
+
+
+unsigned int MakeChecksum(unsigned char *buffer, int len)
+{
+  unsigned int result;
+
+  result = 0;
+  for (int i = 0; i < len; i = i + 1) {
+    result = (result << 3 | result >> 0x1d) ^ buffer[i];
+  }
+
+  return result;
+}
+
+
+unsigned char *make_message(const unsigned char* s) {
+    int len = strlen(s);
+    unsigned char* message = (char*) calloc(1, len + 11);
+
+    message[8] = len + 7;
+    message[10] = len;
+
+    message[9] = 0x2A;
+
+    memcpy(message + 11, s, len);
+
+    *((unsigned int*)message + 1) = time(0LL);
+    
+    *(unsigned int*) message = MakeChecksum(message + 4, len + 7);
+
+    return message;
+}
+
+int main() {
+    unsigned char message[] = "g1mm3_th3_k3y";
+
+    size_t len = strlen(message);
+
+    for (int i = 0; i < len; i++) {
+        message[i] ^= 42;
+    }
+
+    fwrite(make_message(message), 1, strlen(message) + 11, stdout);
+
+    return 0;
+}