unitybugworkaround.c

#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <dlfcn.h>

static FILE *opened_file = NULL;

FILE *fopen(const char *pathname, const char *mode) {
  static FILE *(*real_fopen)(const char *, const char *) = NULL;
 if (!real_fopen)
 {
  printf("Intecepting fopen() calls! \n");
  real_fopen = dlsym(RTLD_NEXT, "fopen");
 }
 opened_file = NULL;

 FILE* ret_val = real_fopen(pathname, mode);

 if (strncmp(pathname, "/proc/", 6) == 0) {
  // remember fopen() calls to /proc...
  opened_file = ret_val;
 }

 return ret_val;
}

FILE *fopen64(const char *pathname, const char *mode) {
 static FILE *(*real_fopen64)(const char *, const char *) = NULL;
 if (!real_fopen64)
 {
  printf("Intecepting fopen64() calls! \n");
  real_fopen64 = dlsym(RTLD_NEXT, "fopen64");
 }
 opened_file = NULL;

 FILE* ret_val = real_fopen64(pathname, mode);

 if (strncmp(pathname, "/proc/", 6) == 0)
 {
  // remember fopen() calls to /proc...
  opened_file = ret_val;
 }

 return ret_val;
}

size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream) {
 static size_t (*real_fread)(void *, size_t, size_t, FILE *) = NULL;
 if (!real_fread)
 {
  printf("Intecepting fread() calls! \n");
  real_fread = dlsym(RTLD_NEXT, "fread");
 }

 size_t ret_val = real_fread(ptr, size, nmemb, stream);

 if (stream == opened_file && strncmp(ptr, "/proc/self/exe", 14) == 0)
 {
  printf("Faking fread() return value! \n");
  memcpy(ptr, "/wutevawutevawuteva", 14);
 }

 return ret_val;
}