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#ifndef LOGIN_NAME_MAX
  12#define LOGIN_NAME_MAX 256
  13#endif
  14
  15/* To avoid problems, the username should consist only of
  16 * letters, digits, underscores, periods, at signs and dashes,
  17 * and not start with a dash (as defined by IEEE Std 1003.1-2001).
  18 * For compatibility with Samba machine accounts $ is also supported
  19 * at the end of the username.
  20 */
  21
  22void FAST_FUNC die_if_bad_username(const char *name)
  23{
  24        const char *start = name;
  25
  26        /* 1st char being dash or dot isn't valid:
  27         * for example, name like ".." can make adduser
  28         * chown "/home/.." recursively - NOT GOOD.
  29         * Name of just a single "$" is also rejected.
  30         */
  31        goto skip;
  32
  33        do {
  34                unsigned char ch;
  35
  36                /* These chars are valid unless they are at the 1st pos: */
  37                if (*name == '-'
  38                 || *name == '.'
  39                /* $ is allowed if it's the last char: */
  40                 || (*name == '$' && !name[1])
  41                ) {
  42                        continue;
  43                }
  44 skip:
  45                ch = *name;
  46                if (ch == '_'
  47                /* || ch == '@' -- we disallow this too. Think about "user@host" */
  48                /* open-coded isalnum: */
  49                 || (ch >= '0' && ch <= '9')
  50                 || ((ch|0x20) >= 'a' && (ch|0x20) <= 'z')
  51                ) {
  52                        continue;
  53                }
  54                bb_error_msg_and_die("illegal character with code %u at position %u",
  55                                (unsigned)ch, (unsigned)(name - start));
  56        } while (*++name);
  57
  58        /* The minimum size of the login name is one char or two if
  59         * last char is the '$'. Violations of this are caught above.
  60         * The maximum size of the login name is LOGIN_NAME_MAX
  61         * including the terminating null byte.
  62         */
  63        if (name - start >= LOGIN_NAME_MAX)
  64                bb_simple_error_msg_and_die("name is too long");
  65}
  66