pathchk.c

UNIX下SH的实现源码

/* pathchk - check pathnames for validity and portability */

/* Usage: pathchk [-p] path ...

   For each PATH, print a message if any of these conditions are false:
   * all existing leading directories in PATH have search (execute) permission
   * strlen (PATH) <= PATH_MAX
   * strlen (each_directory_in_PATH) <= NAME_MAX

   Exit status:
   0			All PATH names passed all of the tests.
   1			An error occurred.

   Options:
   -p			Instead of performing length checks on the
			underlying filesystem, test the length of the
			pathname and its components against the POSIX.1
			minimum limits for portability, _POSIX_NAME_MAX
			and _POSIX_PATH_MAX in 2.9.2.  Also check that
			the pathname contains no character not in the
			portable filename character set. */

/* See Makefile for compilation details. */

#include <config.h>

#include <sys/types.h>
#include "posixstat.h"

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#if defined (HAVE_LIMITS_H)
#  include <limits.h>
#endif

#include "bashansi.h"

#include <stdio.h>
#include <errno.h>

#include "builtins.h"
#include "shell.h"
#include "stdc.h"
#include "bashgetopt.h"
#include "maxpath.h"

#if !defined (errno)
extern int errno;
#endif

#if !defined (_POSIX_PATH_MAX)
#  define _POSIX_PATH_MAX 255
#endif
#if !defined (_POSIX_NAME_MAX)
#  define _POSIX_NAME_MAX 14
#endif

/* How do we get PATH_MAX? */
#if defined (_POSIX_VERSION) && !defined (PATH_MAX)
#  define PATH_MAX_FOR(p) pathconf ((p), _PC_PATH_MAX)
#endif

/* How do we get NAME_MAX? */
#if defined (_POSIX_VERSION) && !defined (NAME_MAX)
#  define NAME_MAX_FOR(p) pathconf ((p), _PC_NAME_MAX)
#endif

#if !defined (PATH_MAX_FOR)
#  define PATH_MAX_FOR(p)	PATH_MAX
#endif

#if !defined (NAME_MAX_FOR)
#  define NAME_MAX_FOR(p)	NAME_MAX
#endif

extern char *strerror ();

static int validate_path ();

pathchk_builtin (list)
     WORD_LIST *list;
{
  int retval, pflag, opt;

  reset_internal_getopt ();
  while ((opt = internal_getopt (list, "p")) != -1)
    {
      switch (opt)
	{
	case 'p':
	  pflag = 1;
	  break;
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }
  list = loptend;

  if (list == 0)
    {
      builtin_usage ();
      return (EX_USAGE);
    }

  for (retval = 0; list; list = list->next)
    retval |= validate_path (list->word->word, pflag);

  return (retval ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}

char *pathchk_doc[] = {
	"Check each pathname argument for validity (i.e., it may be used to",
	"create or access a file without casuing syntax errors) and portability",
	"(i.e., no filename truncation will result).  If the `-p' option is",
	"supplied, more extensive portability checks are performed.",
	(char *)NULL
};

/* The standard structure describing a builtin command.  bash keeps an array
   of these structures. */
struct builtin pathchk_struct = {
	"pathchk",		/* builtin name */
	pathchk_builtin,	/* function implementing the builtin */
	BUILTIN_ENABLED,	/* initial flags for builtin */
	pathchk_doc,		/* array of long documentation strings. */
	"pathchk [-p] pathname ...",	/* usage synopsis */
	0			/* reserved for internal use */
};

/* The remainder of this file is stolen shamelessly from `pathchk.c' in
   the sh-utils-1.12 distribution, by 

   David MacKenzie <[e-mail]>
   and Jim Meyering <[e-mail]> */

/* Each element is nonzero if the corresponding ASCII character is
   in the POSIX portable character set, and zero if it is not.
   In addition, the entry for `/' is nonzero to simplify checking. */
static char const portable_chars[256] =
{
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0-15 */
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 16-31 */
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, /* 32-47 */
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, /* 48-63 */
  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 64-79 */
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, /* 80-95 */
  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 96-111 */
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, /* 112-127 */
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/* If PATH contains only portable characters, return 1, else 0.  */

static int
portable_chars_only (path)
     const char *path;
{
  const char *p;

  for (p = path; *p; ++p)
    if (portable_chars[(const unsigned char) *p] == 0)
      {
	builtin_error ("path `%s' contains nonportable character `%c'", path, *p);
	return 0;
      }
  return 1;
}

/* On some systems, stat can return EINTR.  */

#ifndef EINTR
# define SAFE_STAT(name, buf) stat (name, buf)
#else
# define SAFE_STAT(name, buf) safe_stat (name, buf)
static inline int
safe_stat (name, buf)
     const char *name;
     struct stat *buf;
{
  int ret;

  do
    ret = stat (name, buf);
  while (ret < 0 && errno == EINTR);

  return ret;
}
#endif

/* Return 1 if PATH is a usable leading directory, 0 if not,
   2 if it doesn't exist.  */

static int
dir_ok (path)
     const char *path;
{
  struct stat stats;

  if (SAFE_STAT (path, &stats))
    return 2;

  if (!S_ISDIR (stats.st_mode))
    {
      builtin_error ("`%s' is not a directory", path);
      return 0;
    }

  /* Use access to test for search permission because
     testing permission bits of st_mode can lose with new
     access control mechanisms.  Of course, access loses if you're
     running setuid. */
  if (access (path, X_OK) != 0)
    {
      if (errno == EACCES)
	builtin_error ("directory `%s' is not searchable", path);
      else
	builtin_error ("%s: %s", path, strerror (errno));
      return 0;
    }

  return 1;
}

static char *
xstrdup (s)
     char *s;
{
  return (savestring (s));
}

/* Make sure that
   strlen (PATH) <= PATH_MAX
   && strlen (each-existing-directory-in-PATH) <= NAME_MAX

   If PORTABILITY is nonzero, compare against _POSIX_PATH_MAX and
   _POSIX_NAME_MAX instead, and make sure that PATH contains no
   characters not in the POSIX portable filename character set, which
   consists of A-Z, a-z, 0-9, ., _, -.

   Make sure that all leading directories along PATH that exist have
   `x' permission.

   Return 0 if all of these tests are successful, 1 if any fail. */

static int
validate_path (path, portability)
     char *path;
     int portability;
{
  int path_max;
  int last_elem;		/* Nonzero if checking last element of path. */
  int exists;			/* 2 if the path element exists.  */
  char *slash;
  char *parent;			/* Last existing leading directory so far.  */

  if (portability && !portable_chars_only (path))
    return 1;

  if (*path == '\0')
    return 0;

#ifdef lint
  /* Suppress `used before initialized' warning.  */
  exists = 0;
#endif

  /* Figure out the parent of the first element in PATH.  */
  parent = xstrdup (*path == '/' ? "/" : ".");

  slash = path;
  last_elem = 0;
  while (1)
    {
      int name_max;
      int length;		/* Length of partial path being checked. */
      char *start;		/* Start of path element being checked. */

      /* Find the end of this element of the path.
	 Then chop off the rest of the path after this element. */
      while (*slash == '/')
	slash++;
      start = slash;
      slash = strchr (slash, '/');
      if (slash != NULL)
	*slash = '\0';
      else
	{
	  last_elem = 1;
	  slash = strchr (start, '\0');
	}

      if (!last_elem)
	{
	  exists = dir_ok (path);
	  if (dir_ok == 0)
	    {
	      free (parent);
	      return 1;
	    }
	}

      length = slash - start;
      /* Since we know that `parent' is a directory, it's ok to call
	 pathconf with it as the argument.  (If `parent' isn't a directory
	 or doesn't exist, the behavior of pathconf is undefined.)
	 But if `parent' is a directory and is on a remote file system,
	 it's likely that pathconf can't give us a reasonable value
	 and will return -1.  (NFS and tempfs are not POSIX . . .)
	 In that case, we have no choice but to assume the pessimal
	 POSIX minimums.  */
      name_max = portability ? _POSIX_NAME_MAX : NAME_MAX_FOR (parent);
      if (name_max < 0)
	name_max = _POSIX_NAME_MAX;
      if (length > name_max)
	{
	  builtin_error ("name `%s' has length %d; exceeds limit of %d",
		 start, length, name_max);
	  free (parent);
	  return 1;
	}

      if (last_elem)
	break;

      if (exists == 1)
	{
	  free (parent);
	  parent = xstrdup (path);
	}

      *slash++ = '/';
    }

  /* `parent' is now the last existing leading directory in the whole path,
     so it's ok to call pathconf with it as the argument.  */
  path_max = portability ? _POSIX_PATH_MAX : PATH_MAX_FOR (parent);
  if (path_max < 0)
    path_max = _POSIX_PATH_MAX;
  free (parent);
  if (strlen (path) > path_max)
    {
      builtin_error ("path `%s' has length %d; exceeds limit of %d",
	     path, strlen (path), path_max);
      return 1;
    }

  return 0;
}