LXR busybox/libbb/die_if_bad

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Check user and group names for illegal characters
   4 *
   5 * Copyright (C) 2008 Tito Ragusa <farmatito@tiscali.it>
   6 *
   7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8 */
   9#include "libbb.h"
  10
  11/* To avoid problems, the username should consist only of
  12 * letters, digits, underscores, periods, at signs and dashes,
  13 * and not start with a dash (as defined by IEEE Std 1003.1-2001).
  14 * For compatibility with Samba machine accounts $ is also supported
  15 * at the end of the username.
  16 */
  17
  18void FAST_FUNC die_if_bad_username(const char *name)
  19{
  20        const char *start = name;
  21
  22        /* 1st char being dash or dot isn't valid:
  23         * for example, name like ".." can make adduser
  24         * chown "/home/.." recursively - NOT GOOD.
  25         * Name of just a single "$" is also rejected.
  26         */
  27        goto skip;
  28
  29        do {
  30                unsigned char ch;
  31
  32                /* These chars are valid unless they are at the 1st pos: */
  33                if (*name == '-'
  34                 || *name == '.'
  35                /* $ is allowed if it's the last char: */
  36                 || (*name == '$' && !name[1])
  37                ) {
  38                        continue;
  39                }
  40 skip:
  41                ch = *name;
  42                if (ch == '_'
  43                /* || ch == '@' -- we disallow this too. Think about "user@host" */
  44                /* open-coded isalnum: */
  45                 || (ch >= '0' && ch <= '9')
  46                 || ((ch|0x20) >= 'a' && (ch|0x20) <= 'z')
  47                ) {
  48                        continue;
  49                }
  50                bb_error_msg_and_die("illegal character with code %u at position %u",
  51                                (unsigned)ch, (unsigned)(name - start));
  52        } while (*++name);
  53
  54        /* The minimum size of the login name is one char or two if
  55         * last char is the '$'. Violations of this are caught above.
  56         * The maximum size of the login name is LOGIN_NAME_MAX
  57         * including the terminating null byte.
  58         */
  59        if (name - start >= LOGIN_NAME_MAX)
  60                bb_error_msg_and_die("name is too long");
  61}
  62