Back to index

glibc  2.9
Defines | Functions
chroot_canon.c File Reference
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <ldconfig.h>

Go to the source code of this file.

Defines

#define PATH_MAX   1024

Functions

char * chroot_canon (const char *chroot, const char *name)

Define Documentation

#define PATH_MAX   1024

Definition at line 33 of file chroot_canon.c.


Function Documentation

char* chroot_canon ( const char *  chroot,
const char *  name 
)

Definition at line 43 of file chroot_canon.c.

{
  char *rpath;
  char *dest;
  char *extra_buf = NULL;
  char *rpath_root;
  const char *start;
  const char *end;
  const char *rpath_limit;
  int num_links = 0;
  size_t chroot_len = strlen (chroot);

  if (chroot_len < 1)
    {
      __set_errno (EINVAL);
      return NULL;
    }

  rpath = malloc (chroot_len + PATH_MAX);
  if (rpath == NULL)
    return NULL;

  rpath_limit = rpath + chroot_len + PATH_MAX;

  rpath_root = (char *) mempcpy (rpath, chroot, chroot_len) - 1;
  if (*rpath_root != '/')
    *++rpath_root = '/';
  dest = rpath_root + 1;

  for (start = end = name; *start; start = end)
    {
      struct stat64 st;
      int n;

      /* Skip sequence of multiple path-separators.  */
      while (*start == '/')
       ++start;

      /* Find end of path component.  */
      for (end = start; *end && *end != '/'; ++end)
       /* Nothing.  */;

      if (end - start == 0)
       break;
      else if (end - start == 1 && start[0] == '.')
       /* nothing */;
      else if (end - start == 2 && start[0] == '.' && start[1] == '.')
       {
         /* Back up to previous component, ignore if at root already.  */
         if (dest > rpath_root + 1)
           while ((--dest)[-1] != '/');
       }
      else
       {
         size_t new_size;

         if (dest[-1] != '/')
           *dest++ = '/';

         if (dest + (end - start) >= rpath_limit)
           {
             ptrdiff_t dest_offset = dest - rpath;
             char *new_rpath;

             new_size = rpath_limit - rpath;
             if (end - start + 1 > PATH_MAX)
              new_size += end - start + 1;
             else
              new_size += PATH_MAX;
             new_rpath = (char *) realloc (rpath, new_size);
             if (new_rpath == NULL)
              goto error;
             rpath = new_rpath;
             rpath_limit = rpath + new_size;

             dest = rpath + dest_offset;
           }

         dest = mempcpy (dest, start, end - start);
         *dest = '\0';

         if (lstat64 (rpath, &st) < 0)
           {
             if (*end == '\0')
              goto done;
             goto error;
           }

         if (S_ISLNK (st.st_mode))
           {
             char *buf = alloca (PATH_MAX);
             size_t len;

             if (++num_links > MAXSYMLINKS)
              {
                __set_errno (ELOOP);
                goto error;
              }

             n = readlink (rpath, buf, PATH_MAX);
             if (n < 0)
              {
                if (*end == '\0')
                  goto done;
                goto error;
              }
             buf[n] = '\0';

             if (!extra_buf)
              extra_buf = alloca (PATH_MAX);

             len = strlen (end);
             if ((long int) (n + len) >= PATH_MAX)
              {
                __set_errno (ENAMETOOLONG);
                goto error;
              }

             /* Careful here, end may be a pointer into extra_buf... */
             memmove (&extra_buf[n], end, len + 1);
             name = end = memcpy (extra_buf, buf, n);

             if (buf[0] == '/')
              dest = rpath_root + 1;      /* It's an absolute symlink */
             else
              /* Back up to previous component, ignore if at root already: */
              if (dest > rpath_root + 1)
                while ((--dest)[-1] != '/');
           }
       }
    }
 done:
  if (dest > rpath_root + 1 && dest[-1] == '/')
    --dest;
  *dest = '\0';

  return rpath;

 error:
  free (rpath);
  return NULL;
}

Here is the call graph for this function:

Here is the caller graph for this function: