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/*
* gcc fopen_failure.c -o fopen_failure.so -shared -ldl
* LD_PRELOAD=./fopen_failure.so FAILURE_PATH=/etc/shadow ./test /etc/shadow
*/
#define _GNU_SOURCE
#include <dlfcn.h>
#include <errno.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
typedef FILE * (*fopen_type) (const char *path, const char *mode);
static fopen_type next_fopen;
static const char *failure_path = NULL;
FILE *fopen64 (const char *path, const char *mode)
{
printf ("fopen64(%s, %s)\n", path, mode);
if (NULL == next_fopen)
{
next_fopen = dlsym (RTLD_NEXT, "fopen64");
assert (NULL != next_fopen);
}
if (NULL == failure_path) {
failure_path = getenv ("FAILURE_PATH");
if (NULL == failure_path) {
fputs ("No FAILURE_PATH defined\n", stderr);
}
}
if ( (NULL != path)
&& (NULL != failure_path)
&& (strcmp (path, failure_path) == 0))
{
fprintf (stderr, "fopen64 FAILURE %s %s ...\n", path, mode);
errno = EIO;
return NULL;
}
return next_fopen (path, mode);
}
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