1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Safe gethostname implementation for busybox
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4 | *
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5 | * Copyright (C) 2008 Tito Ragusa <farmatito@tiscali.it>
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6 | *
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7 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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8 | */
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9 |
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10 | /*
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11 | * SUSv2 guarantees that "Host names are limited to 255 bytes"
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12 | * POSIX.1-2001 guarantees that "Host names (not including the terminating
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13 | * null byte) are limited to HOST_NAME_MAX bytes" (64 bytes on my box).
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14 | *
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15 | * RFC1123 says:
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16 | *
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17 | * The syntax of a legal Internet host name was specified in RFC-952
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18 | * [DNS:4]. One aspect of host name syntax is hereby changed: the
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19 | * restriction on the first character is relaxed to allow either a
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20 | * letter or a digit. Host software MUST support this more liberal
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21 | * syntax.
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22 | *
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23 | * Host software MUST handle host names of up to 63 characters and
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24 | * SHOULD handle host names of up to 255 characters.
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25 | */
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26 |
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27 | #include "libbb.h"
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28 | #include <sys/utsname.h>
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29 |
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30 | /*
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31 | * On success return the current malloced and NUL terminated hostname.
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32 | * On error return malloced and NUL terminated string "?".
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33 | * This is an illegal first character for a hostname.
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34 | * The returned malloced string must be freed by the caller.
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35 | */
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36 | char* FAST_FUNC safe_gethostname(void)
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37 | {
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38 | struct utsname uts;
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39 |
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40 | /* The length of the arrays in a struct utsname is unspecified;
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41 | * the fields are terminated by a null byte.
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42 | * Note that there is no standard that says that the hostname
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43 | * set by sethostname(2) is the same string as the nodename field of the
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44 | * struct returned by uname (indeed, some systems allow a 256-byte host-
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45 | * name and an 8-byte nodename), but this is true on Linux. The same holds
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46 | * for setdomainname(2) and the domainname field.
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47 | */
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48 |
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49 | /* Uname can fail only if you pass a bad pointer to it. */
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50 | uname(&uts);
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51 | return xstrndup(!uts.nodename[0] ? "?" : uts.nodename, sizeof(uts.nodename));
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52 | }
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53 |
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54 | /*
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55 | * On success return the current malloced and NUL terminated domainname.
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56 | * On error return malloced and NUL terminated string "?".
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57 | * This is an illegal first character for a domainname.
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58 | * The returned malloced string must be freed by the caller.
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59 | */
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60 | char* FAST_FUNC safe_getdomainname(void)
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61 | {
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62 | #if defined(__linux__)
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63 | /* The field domainname of struct utsname is Linux specific. */
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64 | struct utsname uts;
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65 | uname(&uts);
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66 | return xstrndup(!uts.domainname[0] ? "?" : uts.domainname, sizeof(uts.domainname));
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67 | #else
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68 | /* We really don't care about people with domain names wider than most screens */
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69 | char buf[256];
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70 | int r = getdomainname(buf, sizeof(buf));
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71 | buf[sizeof(buf)-1] = '\0';
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72 | return xstrdup(r < 0 ? "?" : buf);
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73 | #endif
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74 | }
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