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
  10#include "libbb.h"
  11
  12/* To avoid problems, the username should consist only of
  13 * letters, digits, underscores, periods, at signs and dashes,
  14 * and not start with a dash (as defined by IEEE Std 1003.1-2001).
  15 * For compatibility with Samba machine accounts $ is also supported
  16 * at the end of the username.
  17 */
  18
  19void FAST_FUNC die_if_bad_username(const char *name)
  20{
  21        const char *start = name;
  22
  23        /* 1st char being dash or dot isn't valid:
  24         * for example, name like ".." can make adduser
  25         * chown "/home/.." recursively - NOT GOOD.
  26         * Name of just a single "$" is also rejected.
  27         */
  28        goto skip;
  29
  30        do {
  31                unsigned char ch;
  32
  33                /* These chars are valid unless they are at the 1st pos: */
  34                if (*name == '-'
  35                 || *name == '.'
  36                /* $ is allowed if it's the last char: */
  37                 || (*name == '$' && !name[1])
  38                ) {
  39                        continue;
  40                }
  41 skip:
  42                ch = *name;
  43                if (ch == '_'
  44                /* || ch == '@' -- we disallow this too. Think about "user@host" */
  45                /* open-coded isalnum: */
  46                 || (ch >= '0' && ch <= '9')
  47                 || ((ch|0x20) >= 'a' && (ch|0x20) <= 'z')
  48                ) {
  49                        continue;
  50                }
  51                bb_error_msg_and_die("illegal character with code %u at position %u",
  52                                (unsigned)ch, (unsigned)(name - start));
  53        } while (*++name);
  54
  55        /* The minimum size of the login name is one char or two if
  56         * last char is the '$'. Violations of this are caught above.
  57         * The maximum size of the login name is LOGIN_NAME_MAX
  58         * including the terminating null byte.
  59         */
  60        if (name - start >= LOGIN_NAME_MAX)
  61                bb_error_msg_and_die("name is too long");
  62}
  63