release/src/router/busybox/libbb/die_if_bad_username.c

   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
  19 void 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 }