src/pathrewrite.c

   1 /**
   2  * pathrewrite.c
   3  *
   4  * Compile with: gcc -D _GNU_SOURCE -shared -fPIC -o pathrewrite.so pathrewrite.c
   5  *
   6  * Usage: LD_PRELOAD=./pathrewrite.so PATHREWRITE_FROM=/usr/bin PATHREWRITE_TO=/usr/local/bin someprogramm ...
   7  */
   8
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <dlfcn.h>
  12 #include <string.h>
  13 #include <bits/posix1_lim.h>
  14
  15
  16 void pathrewrite_rewrite(const char *orig, char *rw, const char *caller_name)
  17 {
  18         char temp[_POSIX_PATH_MAX];
  19         char *pattern;
  20         char *newstring;
  21         char *index;
  22
  23         strcpy(rw, orig);
  24         pattern = getenv("PATHREWRITE_FROM");
  25         newstring = getenv("PATHREWRITE_TO");
  26
  27         if(pattern != NULL && newstring != NULL)
  28         {
  29                 index = strstr(rw, pattern);
  30                 if(index != NULL)
  31                 {
  32                         //fprintf(stderr, "index = %s\n", index);
  33                         strcpy(temp, &index[strlen(pattern)]);
  34                         strcpy(index, newstring);
  35                         strcpy(&index[strlen(newstring)], temp);
  36                         fprintf(stderr, "pathrewrite.so: %s(%s -> %s)\n", caller_name, orig, rw);
  37                 }
  38         }
  39 }
  40
  41
  42 int __xstat(int ver, const char *path, struct stat *buf)
  43 {
  44         char pathrw[_POSIX_PATH_MAX];
  45
  46         pathrewrite_rewrite(path, pathrw, __func__);
  47
  48         int (*orig___xstat)(int, const char *, struct stat *) = dlsym(RTLD_NEXT, "__xstat");
  49         return orig___xstat(ver, pathrw, buf);
  50 }
  51
  52 int __lxstat(int ver, const char *path, struct stat *buf)
  53 {
  54         char pathrw[_POSIX_PATH_MAX];
  55
  56         pathrewrite_rewrite(path, pathrw, __func__);
  57
  58         int (*orig___lxstat)(int, const char *, struct stat *) = dlsym(RTLD_NEXT, "__lxstat");
  59         return orig___lxstat(ver, pathrw, buf);
  60 }
  61
  62
  63 int open(const char *pathname, int flags, mode_t mode)
  64 {
  65         char pathrw[_POSIX_PATH_MAX];
  66
  67         pathrewrite_rewrite(pathname, pathrw, __func__);
  68
  69         int (*orig_open)(const char *, int, mode_t) = dlsym(RTLD_NEXT, "open");
  70         return orig_open(pathrw, flags, mode);
  71 }
  72
  73 FILE *fopen(__const char *__restrict pathname, __const char *__restrict mode)
  74 {
  75         char pathrw[_POSIX_PATH_MAX];
  76
  77         pathrewrite_rewrite(pathname, pathrw, __func__);
  78
  79         FILE *(*orig_fopen)(__const char *__restrict, __const char *__restrict) = dlsym(RTLD_NEXT, "fopen");
  80         return orig_fopen(pathrw, mode);
  81 }
  82