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/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/* GLIB - Library of useful routines for C programming
* Copyright (C) 2008 Red Hat, Inc.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "config.h"
#include "glibconfig.h"
#include <string.h>
#ifdef G_OS_UNIX
#include <unistd.h>
#endif
#include "ghostutils.h"
#include "garray.h"
#include "gmem.h"
#include "gstring.h"
#include "gstrfuncs.h"
#include "glibintl.h"
#ifdef G_PLATFORM_WIN32
#include <windows.h>
#endif
/**
* SECTION:ghostutils
* @short_description: Internet hostname utilities
*
* Functions for manipulating internet hostnames; in particular, for
* converting between Unicode and ASCII-encoded forms of
* Internationalized Domain Names (IDNs).
*
* The
* [Internationalized Domain Names for Applications (IDNA)](http://www.ietf.org/rfc/rfc3490.txt)
* standards allow for the use
* of Unicode domain names in applications, while providing
* backward-compatibility with the old ASCII-only DNS, by defining an
* ASCII-Compatible Encoding of any given Unicode name, which can be
* used with non-IDN-aware applications and protocols. (For example,
* "Παν語.org" maps to "xn--4wa8awb4637h.org".)
**/
#define IDNA_ACE_PREFIX "xn--"
#define IDNA_ACE_PREFIX_LEN 4
/* Punycode constants, from RFC 3492. */
#define PUNYCODE_BASE 36
#define PUNYCODE_TMIN 1
#define PUNYCODE_TMAX 26
#define PUNYCODE_SKEW 38
#define PUNYCODE_DAMP 700
#define PUNYCODE_INITIAL_BIAS 72
#define PUNYCODE_INITIAL_N 0x80
#define PUNYCODE_IS_BASIC(cp) ((guint)(cp) < 0x80)
/* Encode/decode a single base-36 digit */
static inline gchar
encode_digit (guint dig)
{
if (dig < 26)
return dig + 'a';
else
return dig - 26 + '0';
}
static inline guint
decode_digit (gchar dig)
{
if (dig >= 'A' && dig <= 'Z')
return dig - 'A';
else if (dig >= 'a' && dig <= 'z')
return dig - 'a';
else if (dig >= '0' && dig <= '9')
return dig - '0' + 26;
else
return G_MAXUINT;
}
/* Punycode bias adaptation algorithm, RFC 3492 section 6.1 */
static guint
adapt (guint delta,
guint numpoints,
gboolean firsttime)
{
guint k;
delta = firsttime ? delta / PUNYCODE_DAMP : delta / 2;
delta += delta / numpoints;
k = 0;
while (delta > ((PUNYCODE_BASE - PUNYCODE_TMIN) * PUNYCODE_TMAX) / 2)
{
delta /= PUNYCODE_BASE - PUNYCODE_TMIN;
k += PUNYCODE_BASE;
}
return k + ((PUNYCODE_BASE - PUNYCODE_TMIN + 1) * delta /
(delta + PUNYCODE_SKEW));
}
/* Punycode encoder, RFC 3492 section 6.3. The algorithm is
* sufficiently bizarre that it's not really worth trying to explain
* here.
*/
static gboolean
punycode_encode (const gchar *input_utf8,
gsize input_utf8_length,
GString *output)
{
guint delta, handled_chars, num_basic_chars, bias, j, q, k, t, digit;
gunichar n, m, *input;
glong written_chars;
gsize input_length;
gboolean success = FALSE;
/* Convert from UTF-8 to Unicode code points */
input = g_utf8_to_ucs4 (input_utf8, input_utf8_length, NULL,
&written_chars, NULL);
if (!input)
return FALSE;
input_length = (gsize) (written_chars > 0 ? written_chars : 0);
/* Copy basic chars */
for (j = num_basic_chars = 0; j < input_length; j++)
{
if (PUNYCODE_IS_BASIC (input[j]))
{
g_string_append_c (output, g_ascii_tolower (input[j]));
num_basic_chars++;
}
}
if (num_basic_chars)
g_string_append_c (output, '-');
handled_chars = num_basic_chars;
/* Encode non-basic chars */
delta = 0;
bias = PUNYCODE_INITIAL_BIAS;
n = PUNYCODE_INITIAL_N;
while (handled_chars < input_length)
{
/* let m = the minimum {non-basic} code point >= n in the input */
for (m = G_MAXUINT, j = 0; j < input_length; j++)
{
if (input[j] >= n && input[j] < m)
m = input[j];
}
if (m - n > (G_MAXUINT - delta) / (handled_chars + 1))
goto fail;
delta += (m - n) * (handled_chars + 1);
n = m;
for (j = 0; j < input_length; j++)
{
if (input[j] < n)
{
if (++delta == 0)
goto fail;
}
else if (input[j] == n)
{
q = delta;
for (k = PUNYCODE_BASE; ; k += PUNYCODE_BASE)
{
if (k <= bias)
t = PUNYCODE_TMIN;
else if (k >= bias + PUNYCODE_TMAX)
t = PUNYCODE_TMAX;
else
t = k - bias;
if (q < t)
break;
digit = t + (q - t) % (PUNYCODE_BASE - t);
g_string_append_c (output, encode_digit (digit));
q = (q - t) / (PUNYCODE_BASE - t);
}
g_string_append_c (output, encode_digit (q));
bias = adapt (delta, handled_chars + 1, handled_chars == num_basic_chars);
delta = 0;
handled_chars++;
}
}
delta++;
n++;
}
success = TRUE;
fail:
g_free (input);
return success;
}
/* From RFC 3454, Table B.1 */
#define idna_is_junk(ch) ((ch) == 0x00AD || (ch) == 0x1806 || (ch) == 0x200B || (ch) == 0x2060 || (ch) == 0xFEFF || (ch) == 0x034F || (ch) == 0x180B || (ch) == 0x180C || (ch) == 0x180D || (ch) == 0x200C || (ch) == 0x200D || ((ch) >= 0xFE00 && (ch) <= 0xFE0F))
/* Scan @str for "junk" and return a cleaned-up string if any junk
* is found. Else return %NULL.
*/
static gchar *
remove_junk (const gchar *str,
gint len)
{
GString *cleaned = NULL;
const gchar *p;
gunichar ch;
for (p = str; len == -1 ? *p : p < str + len; p = g_utf8_next_char (p))
{
ch = g_utf8_get_char (p);
if (idna_is_junk (ch))
{
if (!cleaned)
{
cleaned = g_string_new (NULL);
g_string_append_len (cleaned, str, p - str);
}
}
else if (cleaned)
g_string_append_unichar (cleaned, ch);
}
if (cleaned)
return g_string_free (cleaned, FALSE);
else
return NULL;
}
static inline gboolean
contains_uppercase_letters (const gchar *str,
gint len)
{
const gchar *p;
for (p = str; len == -1 ? *p : p < str + len; p = g_utf8_next_char (p))
{
if (g_unichar_isupper (g_utf8_get_char (p)))
return TRUE;
}
return FALSE;
}
static inline gboolean
contains_non_ascii (const gchar *str,
gint len)
{
const gchar *p;
for (p = str; len == -1 ? *p : p < str + len; p++)
{
if ((guchar)*p > 0x80)
return TRUE;
}
return FALSE;
}
/* RFC 3454, Appendix C. ish. */
static inline gboolean
idna_is_prohibited (gunichar ch)
{
switch (g_unichar_type (ch))
{
case G_UNICODE_CONTROL:
case G_UNICODE_FORMAT:
case G_UNICODE_UNASSIGNED:
case G_UNICODE_PRIVATE_USE:
case G_UNICODE_SURROGATE:
case G_UNICODE_LINE_SEPARATOR:
case G_UNICODE_PARAGRAPH_SEPARATOR:
case G_UNICODE_SPACE_SEPARATOR:
return TRUE;
case G_UNICODE_OTHER_SYMBOL:
if (ch == 0xFFFC || ch == 0xFFFD ||
(ch >= 0x2FF0 && ch <= 0x2FFB))
return TRUE;
return FALSE;
case G_UNICODE_NON_SPACING_MARK:
if (ch == 0x0340 || ch == 0x0341)
return TRUE;
return FALSE;
default:
return FALSE;
}
}
/* RFC 3491 IDN cleanup algorithm. */
static gchar *
nameprep (const gchar *hostname,
gint len,
gboolean *is_unicode)
{
gchar *name, *tmp = NULL, *p;
/* It would be nice if we could do this without repeatedly
* allocating strings and converting back and forth between
* gunichars and UTF-8... The code does at least avoid doing most of
* the sub-operations when they would just be equivalent to a
* g_strdup().
*/
/* Remove presentation-only characters */
name = remove_junk (hostname, len);
if (name)
{
tmp = name;
len = -1;
}
else
name = (gchar *)hostname;
/* Convert to lowercase */
if (contains_uppercase_letters (name, len))
{
name = g_utf8_strdown (name, len);
g_free (tmp);
tmp = name;
len = -1;
}
/* If there are no UTF8 characters, we're done. */
if (!contains_non_ascii (name, len))
{
*is_unicode = FALSE;
if (name == (gchar *)hostname)
return len == -1 ? g_strdup (hostname) : g_strndup (hostname, len);
else
return name;
}
*is_unicode = TRUE;
/* Normalize */
name = g_utf8_normalize (name, len, G_NORMALIZE_NFKC);
g_free (tmp);
tmp = name;
if (!name)
return NULL;
/* KC normalization may have created more capital letters (eg,
* angstrom -> capital A with ring). So we have to lowercasify a
* second time. (This is more-or-less how the nameprep algorithm
* does it. If tolower(nfkc(tolower(X))) is guaranteed to be the
* same as tolower(nfkc(X)), then we could skip the first tolower,
* but I'm not sure it is.)
*/
if (contains_uppercase_letters (name, -1))
{
name = g_utf8_strdown (name, -1);
g_free (tmp);
tmp = name;
}
/* Check for prohibited characters */
for (p = name; *p; p = g_utf8_next_char (p))
{
if (idna_is_prohibited (g_utf8_get_char (p)))
{
name = NULL;
g_free (tmp);
goto done;
}
}
/* FIXME: We're supposed to verify certain constraints on bidi
* characters, but glib does not appear to have that information.
*/
done:
return name;
}
/* RFC 3490, section 3.1 says '.', 0x3002, 0xFF0E, and 0xFF61 count as
* label-separating dots. @str must be '\0'-terminated.
*/
#define idna_is_dot(str) ( \
((guchar)(str)[0] == '.') || \
((guchar)(str)[0] == 0xE3 && (guchar)(str)[1] == 0x80 && (guchar)(str)[2] == 0x82) || \
((guchar)(str)[0] == 0xEF && (guchar)(str)[1] == 0xBC && (guchar)(str)[2] == 0x8E) || \
((guchar)(str)[0] == 0xEF && (guchar)(str)[1] == 0xBD && (guchar)(str)[2] == 0xA1) )
static const gchar *
idna_end_of_label (const gchar *str)
{
for (; *str; str = g_utf8_next_char (str))
{
if (idna_is_dot (str))
return str;
}
return str;
}
static gsize
get_hostname_max_length_bytes (void)
{
#if defined(G_OS_WIN32)
wchar_t tmp[MAX_COMPUTERNAME_LENGTH];
return sizeof (tmp) / sizeof (tmp[0]);
#elif defined(_SC_HOST_NAME_MAX)
glong max = sysconf (_SC_HOST_NAME_MAX);
if (max > 0)
return (gsize) max;
#ifdef HOST_NAME_MAX
return HOST_NAME_MAX;
#else
return _POSIX_HOST_NAME_MAX;
#endif /* HOST_NAME_MAX */
#else
/* Fallback to some reasonable value
* See https://stackoverflow.com/questions/8724954/what-is-the-maximum-number-of-characters-for-a-host-name-in-unix/28918017#28918017 */
return 255;
#endif
}
/* Returns %TRUE if `strlen (str) > comparison_length`, but without actually
* running `strlen(str)`, as that would take a very long time for long
* (untrusted) input strings. */
static gboolean
strlen_greater_than (const gchar *str,
gsize comparison_length)
{
gsize i;
for (i = 0; str[i] != '\0'; i++)
if (i > comparison_length)
return TRUE;
return FALSE;
}
/**
* g_hostname_to_ascii:
* @hostname: a valid UTF-8 or ASCII hostname
*
* Converts @hostname to its canonical ASCII form; an ASCII-only
* string containing no uppercase letters and not ending with a
* trailing dot.
*
* Returns: (nullable) (transfer full): an ASCII hostname, which must be freed,
* or %NULL if @hostname is in some way invalid.
*
* Since: 2.22
**/
gchar *
g_hostname_to_ascii (const gchar *hostname)
{
gchar *name, *label, *p;
GString *out;
gssize llen, oldlen;
gboolean unicode;
gsize hostname_max_length_bytes = get_hostname_max_length_bytes ();
/* Do an initial check on the hostname length, as overlong hostnames take a
* long time in the IDN cleanup algorithm in nameprep(). The ultimate
* restriction is that the IDN-decoded (i.e. pure ASCII) hostname cannot be
* longer than 255 bytes. That’s the least restrictive limit on hostname
* length of all the ways hostnames can be interpreted. Typically, the
* hostname will be an FQDN, which is limited to 253 bytes long. POSIX
* hostnames are limited to `get_hostname_max_length_bytes()` (typically 255
* bytes).
*
* See https://stackoverflow.com/a/28918017/2931197
*
* It’s possible for a hostname to be %-encoded, in which case its decoded
* length will be as much as 3× shorter.
*
* It’s also possible for a hostname to use overlong UTF-8 encodings, in which
* case its decoded length will be as much as 4× shorter.
*
* Note: This check is not intended as an absolute guarantee that a hostname
* is the right length and will be accepted by other systems. It’s intended to
* stop wildly-invalid hostnames from taking forever in nameprep().
*/
if (hostname_max_length_bytes <= G_MAXSIZE / 4 &&
strlen_greater_than (hostname, 4 * MAX (255, hostname_max_length_bytes)))
return NULL;
label = name = nameprep (hostname, -1, &unicode);
if (!name || !unicode)
return name;
out = g_string_new (NULL);
do
{
unicode = FALSE;
for (p = label; *p && !idna_is_dot (p); p++)
{
if ((guchar)*p > 0x80)
unicode = TRUE;
}
oldlen = out->len;
llen = p - label;
if (unicode)
{
if (!strncmp (label, IDNA_ACE_PREFIX, IDNA_ACE_PREFIX_LEN))
goto fail;
g_string_append (out, IDNA_ACE_PREFIX);
if (!punycode_encode (label, llen, out))
goto fail;
}
else
g_string_append_len (out, label, llen);
if (out->len - oldlen > 63)
goto fail;
label += llen;
if (*label)
label = g_utf8_next_char (label);
if (*label)
g_string_append_c (out, '.');
}
while (*label);
g_free (name);
return g_string_free (out, FALSE);
fail:
g_free (name);
g_string_free (out, TRUE);
return NULL;
}
/**
* g_hostname_is_non_ascii:
* @hostname: a hostname
*
* Tests if @hostname contains Unicode characters. If this returns
* %TRUE, you need to encode the hostname with g_hostname_to_ascii()
* before using it in non-IDN-aware contexts.
*
* Note that a hostname might contain a mix of encoded and unencoded
* segments, and so it is possible for g_hostname_is_non_ascii() and
* g_hostname_is_ascii_encoded() to both return %TRUE for a name.
*
* Returns: %TRUE if @hostname contains any non-ASCII characters
*
* Since: 2.22
**/
gboolean
g_hostname_is_non_ascii (const gchar *hostname)
{
return contains_non_ascii (hostname, -1);
}
/* Punycode decoder, RFC 3492 section 6.2. As with punycode_encode(),
* read the RFC if you want to understand what this is actually doing.
*/
static gboolean
punycode_decode (const gchar *input,
gsize input_length,
GString *output)
{
GArray *output_chars;
gunichar n;
guint i, bias;
guint oldi, w, k, digit, t;
const gchar *split;
n = PUNYCODE_INITIAL_N;
i = 0;
bias = PUNYCODE_INITIAL_BIAS;
split = input + input_length - 1;
while (split > input && *split != '-')
split--;
if (split > input)
{
output_chars = g_array_sized_new (FALSE, FALSE, sizeof (gunichar),
split - input);
input_length -= (split - input) + 1;
while (input < split)
{
gunichar ch = (gunichar)*input++;
if (!PUNYCODE_IS_BASIC (ch))
goto fail;
g_array_append_val (output_chars, ch);
}
input++;
}
else
output_chars = g_array_new (FALSE, FALSE, sizeof (gunichar));
while (input_length)
{
oldi = i;
w = 1;
for (k = PUNYCODE_BASE; ; k += PUNYCODE_BASE)
{
if (!input_length--)
goto fail;
digit = decode_digit (*input++);
if (digit >= PUNYCODE_BASE)
goto fail;
if (digit > (G_MAXUINT - i) / w)
goto fail;
i += digit * w;
if (k <= bias)
t = PUNYCODE_TMIN;
else if (k >= bias + PUNYCODE_TMAX)
t = PUNYCODE_TMAX;
else
t = k - bias;
if (digit < t)
break;
if (w > G_MAXUINT / (PUNYCODE_BASE - t))
goto fail;
w *= (PUNYCODE_BASE - t);
}
bias = adapt (i - oldi, output_chars->len + 1, oldi == 0);
if (i / (output_chars->len + 1) > G_MAXUINT - n)
goto fail;
n += i / (output_chars->len + 1);
i %= (output_chars->len + 1);
g_array_insert_val (output_chars, i++, n);
}
for (i = 0; i < output_chars->len; i++)
g_string_append_unichar (output, g_array_index (output_chars, gunichar, i));
g_array_free (output_chars, TRUE);
return TRUE;
fail:
g_array_free (output_chars, TRUE);
return FALSE;
}
/**
* g_hostname_to_unicode:
* @hostname: a valid UTF-8 or ASCII hostname
*
* Converts @hostname to its canonical presentation form; a UTF-8
* string in Unicode normalization form C, containing no uppercase
* letters, no forbidden characters, and no ASCII-encoded segments,
* and not ending with a trailing dot.
*
* Of course if @hostname is not an internationalized hostname, then
* the canonical presentation form will be entirely ASCII.
*
* Returns: (nullable) (transfer full): a UTF-8 hostname, which must be freed,
* or %NULL if @hostname is in some way invalid.
*
* Since: 2.22
**/
gchar *
g_hostname_to_unicode (const gchar *hostname)
{
GString *out;
gssize llen;
gsize hostname_max_length_bytes = get_hostname_max_length_bytes ();
/* See the comment at the top of g_hostname_to_ascii(). */
if (hostname_max_length_bytes <= G_MAXSIZE / 4 &&
strlen_greater_than (hostname, 4 * MAX (255, hostname_max_length_bytes)))
return NULL;
out = g_string_new (NULL);
do
{
llen = idna_end_of_label (hostname) - hostname;
if (!g_ascii_strncasecmp (hostname, IDNA_ACE_PREFIX, IDNA_ACE_PREFIX_LEN))
{
hostname += IDNA_ACE_PREFIX_LEN;
llen -= IDNA_ACE_PREFIX_LEN;
if (!punycode_decode (hostname, llen, out))
{
g_string_free (out, TRUE);
return NULL;
}
}
else
{
gboolean unicode;
gchar *canonicalized = nameprep (hostname, llen, &unicode);
if (!canonicalized)
{
g_string_free (out, TRUE);
return NULL;
}
g_string_append (out, canonicalized);
g_free (canonicalized);
}
hostname += llen;
if (*hostname)
hostname = g_utf8_next_char (hostname);
if (*hostname)
g_string_append_c (out, '.');
}
while (*hostname);
return g_string_free (out, FALSE);
}
/**
* g_hostname_is_ascii_encoded:
* @hostname: a hostname
*
* Tests if @hostname contains segments with an ASCII-compatible
* encoding of an Internationalized Domain Name. If this returns
* %TRUE, you should decode the hostname with g_hostname_to_unicode()
* before displaying it to the user.
*
* Note that a hostname might contain a mix of encoded and unencoded
* segments, and so it is possible for g_hostname_is_non_ascii() and
* g_hostname_is_ascii_encoded() to both return %TRUE for a name.
*
* Returns: %TRUE if @hostname contains any ASCII-encoded
* segments.
*
* Since: 2.22
**/
gboolean
g_hostname_is_ascii_encoded (const gchar *hostname)
{
while (1)
{
if (!g_ascii_strncasecmp (hostname, IDNA_ACE_PREFIX, IDNA_ACE_PREFIX_LEN))
return TRUE;
hostname = idna_end_of_label (hostname);
if (*hostname)
hostname = g_utf8_next_char (hostname);
if (!*hostname)
return FALSE;
}
}
/**
* g_hostname_is_ip_address:
* @hostname: a hostname (or IP address in string form)
*
* Tests if @hostname is the string form of an IPv4 or IPv6 address.
* (Eg, "192.168.0.1".)
*
* Since 2.66, IPv6 addresses with a zone-id are accepted (RFC6874).
*
* Returns: %TRUE if @hostname is an IP address
*
* Since: 2.22
**/
gboolean
g_hostname_is_ip_address (const gchar *hostname)
{
gchar *p, *end;
gint nsegments, octet;
/* On Linux we could implement this using inet_pton, but the Windows
* equivalent of that requires linking against winsock, so we just
* figure this out ourselves. Tested by tests/hostutils.c.
*/
p = (char *)hostname;
if (strchr (p, ':'))
{
gboolean skipped;
/* If it contains a ':', it's an IPv6 address (assuming it's an
* IP address at all). This consists of eight ':'-separated
* segments, each containing a 1-4 digit hex number, except that
* optionally: (a) the last two segments can be replaced by an
* IPv4 address, and (b) a single span of 1 to 8 "0000" segments
* can be replaced with just "::".
*/
nsegments = 0;
skipped = FALSE;
while (*p && *p != '%' && nsegments < 8)
{
/* Each segment after the first must be preceded by a ':'.
* (We also handle half of the "string starts with ::" case
* here.)
*/
if (p != (char *)hostname || (p[0] == ':' && p[1] == ':'))
{
if (*p != ':')
return FALSE;
p++;
}
/* If there's another ':', it means we're skipping some segments */
if (*p == ':' && !skipped)
{
skipped = TRUE;
nsegments++;
/* Handle the "string ends with ::" case */
if (!p[1])
p++;
continue;
}
/* Read the segment, make sure it's valid. */
for (end = p; g_ascii_isxdigit (*end); end++)
;
if (end == p || end > p + 4)
return FALSE;
if (*end == '.')
{
if ((nsegments == 6 && !skipped) || (nsegments <= 6 && skipped))
goto parse_ipv4;
else
return FALSE;
}
nsegments++;
p = end;
}
return (!*p || (p[0] == '%' && p[1])) && (nsegments == 8 || skipped);
}
parse_ipv4:
/* Parse IPv4: N.N.N.N, where each N <= 255 and doesn't have leading 0s. */
for (nsegments = 0; nsegments < 4; nsegments++)
{
if (nsegments != 0)
{
if (*p != '.')
return FALSE;
p++;
}
/* Check the segment; a little tricker than the IPv6 case since
* we can't allow extra leading 0s, and we can't assume that all
* strings of valid length are within range.
*/
octet = 0;
if (*p == '0')
end = p + 1;
else
{
for (end = p; g_ascii_isdigit (*end); end++)
{
octet = 10 * octet + (*end - '0');
if (octet > 255)
break;
}
}
if (end == p || end > p + 3 || octet > 255)
return FALSE;
p = end;
}
/* If there's nothing left to parse, then it's ok. */
return !*p;
}
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