Add detour library for hooking

https://github.com/8dcc/detour-lib

Makefile

@@ -5,7 +5,7 @@ INCLUDES=-Isrc/include/sdk/common -Isrc/include/sdk/public -Isrc/include/sdk/pm_
 CFLAGS=-Wall -Wextra -Wno-write-strings -m32 -fPIC $(INCLUDES)
 LDFLAGS=-lm
 
-OBJS=obj/main.c.o obj/globals.c.o obj/cvars.c.o obj/hooks.c.o obj/util.c.o obj/features/movement.c.o obj/features/esp.c.o obj/features/chams.c.o
+OBJS=obj/main.c.o obj/globals.c.o obj/cvars.c.o obj/hooks.c.o obj/detour.c.o obj/util.c.o obj/features/movement.c.o obj/features/esp.c.o obj/features/chams.c.o
 BIN=libhlcheat.so
 
 .PHONY: clean all inject

src/detour.c

@@ -0,0 +1,110 @@
+/**
+ * @file      detour.c
+ * @brief     Detour hooking library source
+ * @author    8dcc
+ *
+ * https://github.com/8dcc/detour-lib
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>   /* getpagesize */
+#include <sys/mman.h> /* mprotect */
+
+#include "include/detour.h"
+
+#define PAGE_SIZE          getpagesize()
+#define PAGE_MASK          (~(PAGE_SIZE - 1))
+#define PAGE_ALIGN(x)      ((x + PAGE_SIZE - 1) & PAGE_MASK)
+#define PAGE_ALIGN_DOWN(x) (PAGE_ALIGN(x) - PAGE_SIZE)
+
+static bool protect_addr(void* ptr, int new_flags) {
+    void* p  = (void*)PAGE_ALIGN_DOWN((detour_ptr_t)ptr);
+    int pgsz = getpagesize();
+
+    if (mprotect(p, pgsz, new_flags) == -1)
+        return false;
+
+    return true;
+}
+
+/*
+ * 64 bits:
+ *   0:  48 b8 45 55 46 84 45    movabs rax,0x454584465545
+ *   7:  45 00 00
+ *   a:  ff e0                   jmp    rax
+ *
+ * 32 bits:
+ *   0:  b8 01 00 00 00          mov    eax,0x1
+ *   5:  ff e0                   jmp    eax
+ */
+#ifdef __i386__
+static uint8_t def_jmp_bytes[] = { 0xB8, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xE0 };
+#define JMP_BYTES_PTR 1 /* Offset inside the array where the ptr should go */
+#else
+static uint8_t def_jmp_bytes[] = { 0x48, 0xB8, 0x00, 0x00, 0x00, 0x00,
+                                   0x00, 0x00, 0x00, 0x00, 0xFF, 0xE0 };
+#define JMP_BYTES_PTR 2 /* Offset inside the array where the ptr should go */
+#endif
+
+void detour_init(detour_data_t* data, void* orig, void* hook) {
+    data->detoured = false;
+    data->orig     = orig;
+    data->hook     = hook;
+
+    /* Store the first N bytes of the original function, where N is the size of
+     * the jmp instructions */
+    memcpy(data->saved_bytes, orig, sizeof(data->saved_bytes));
+
+    /* Default jmp bytes */
+    memcpy(data->jmp_bytes, &def_jmp_bytes, sizeof(def_jmp_bytes));
+
+    /* JMP_BYTES_PTR is defined bellow def_jmp_bytes, and it changes depending
+     * on the arch.
+     * We use "&hook" and not "hook" because we want the address of
+     * the func, not the first bytes of it like before. */
+    memcpy(&data->jmp_bytes[JMP_BYTES_PTR], &hook, sizeof(detour_ptr_t));
+}
+
+bool detour_add(detour_data_t* d) {
+    /* Already detoured, nothing to do */
+    if (d->detoured)
+        return true;
+
+    /* See util.c */
+    if (!protect_addr(d->orig, PROT_READ | PROT_WRITE | PROT_EXEC))
+        return false;
+
+    /* Copy our jmp instruction with our hook address to the orig */
+    memcpy(d->orig, d->jmp_bytes, sizeof(d->jmp_bytes));
+
+    /* Restore old protection */
+    if (protect_addr(d->orig, PROT_READ | PROT_EXEC)) {
+        d->detoured = true;
+        return true;
+    }
+
+    return false;
+}
+
+bool detour_del(detour_data_t* d) {
+    /* Not detoured, nothing to do */
+    if (!d->detoured)
+        return true;
+
+    /* See util.c */
+    if (!protect_addr(d->orig, PROT_READ | PROT_WRITE | PROT_EXEC))
+        return false;
+
+    /* Restore the bytes that were at the start of orig (we saved on init) */
+    memcpy(d->orig, d->saved_bytes, sizeof(d->saved_bytes));
+
+    /* Restore old protection */
+    if (protect_addr(d->orig, PROT_READ | PROT_EXEC)) {
+        d->detoured = false;
+        return true;
+    }
+
+    return false;
+}

src/include/detour.h

@@ -0,0 +1,48 @@
+/**
+ * @file      detour.h
+ * @brief     Detour hooking library header
+ * @author    8dcc
+ *
+ * https://github.com/8dcc/detour-lib
+ */
+
+#ifndef DETOUR_H_
+#define DETOUR_H_
+
+#ifdef __i386__
+typedef uint32_t detour_ptr_t;
+#define JMP_SZ_ 7 /* Size of jmp instructions in 32bit */
+#else
+typedef uint64_t detour_ptr_t;
+#define JMP_SZ_ 12 /* Size of jmp instructions in 64bit */
+#endif
+
+typedef struct {
+    bool detoured;
+    void* orig;
+    void* hook;
+    uint8_t jmp_bytes[JMP_SZ_];
+    uint8_t saved_bytes[JMP_SZ_];
+} detour_data_t;
+
+/*----------------------------------------------------------------------------*/
+
+void detour_init(detour_data_t* data, void* orig, void* hook);
+bool detour_add(detour_data_t* d);
+bool detour_del(detour_data_t* d);
+
+/*----------------------------------------------------------------------------*/
+
+/* Declare the type for the original function */
+#define DECL_DETOUR_TYPE(funcRet, funcName, ...) \
+    typedef funcRet (*funcName##_t)(__VA_ARGS__);
+
+/* Reset original bytes, call original, detour again. detourData is NOT a ptr */
+#define CALL_ORIGINAL(detourData, funcName, ...)      \
+    {                                                 \
+        detour_del(&detourData);                      \
+        ((funcName##_t)detourData.orig)(__VA_ARGS__); \
+        detour_add(&detourData);                      \
+    }
+
+#endif /* DETOUR_H_ */