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/*-
* Copyright 2021 Vsevolod Stakhov
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "css_util.hxx"
#include "css.hxx"
#include <unicode/utf8.h>
namespace rspamd::css {
std::string_view unescape_css(rspamd_mempool_t *pool,
const std::string_view &sv)
{
auto *nspace = reinterpret_cast<char *>(rspamd_mempool_alloc(pool, sv.length()));
auto *d = nspace;
auto nleft = sv.length ();
enum {
normal = 0,
quoted,
escape,
skip_spaces,
} state = normal;
char quote_char, prev_c = 0;
auto escape_offset = 0, i = 0;
#define MAYBE_CONSUME_CHAR(c) do { \
if ((c) == '"' || (c) == '\'') { \
state = quoted; \
quote_char = (c); \
nleft--; \
*d++ = (c); \
} \
else if ((c) == '\\') { \
escape_offset = i; \
state = escape; \
} \
else { \
state = normal; \
nleft--; \
*d++ = g_ascii_tolower(c); \
} \
} while (0)
for (const auto c : sv) {
if (nleft == 0) {
msg_err_css("cannot unescape css: truncated buffer of size %d",
(int)sv.length());
break;
}
switch (state) {
case normal:
MAYBE_CONSUME_CHAR(c);
break;
case quoted:
if (c == quote_char) {
if (prev_c != '\\') {
state = normal;
}
}
prev_c = c;
nleft --;
*d++ = c;
break;
case escape:
if (!g_ascii_isxdigit(c)) {
if (i > escape_offset + 1) {
/* Try to decode an escape */
const auto *escape_start = &sv[escape_offset + 1];
unsigned long val;
if (!rspamd_xstrtoul(escape_start, i - escape_offset - 1, &val)) {
msg_debug_css("invalid broken escape found at pos %d",
escape_offset);
}
else {
if (val < 0x80) {
/* Trivial case: ascii character */
*d++ = (unsigned char)g_ascii_tolower(val);
nleft --;
}
else {
UChar32 uc = val;
auto off = 0;
UTF8_APPEND_CHAR_SAFE((uint8_t *) d, off,
sv.length (), u_tolower(uc));
d += off;
nleft -= off;
}
}
}
else {
/* Empty escape, ignore it */
msg_debug_css("invalid empty escape found at pos %d",
escape_offset);
}
if (nleft <= 0) {
msg_err_css("cannot unescape css: truncated buffer of size %d",
(int)sv.length());
}
else {
/* Escape is done, advance forward */
if (g_ascii_isspace (c)) {
state = skip_spaces;
}
else {
MAYBE_CONSUME_CHAR(c);
}
}
}
break;
case skip_spaces:
if (!g_ascii_isspace(c)) {
MAYBE_CONSUME_CHAR(c);
}
/* Ignore spaces */
break;
}
i ++;
}
return std::string_view{nspace, sv.size() - nleft};
}
}
/* C API */
const gchar *rspamd_css_unescape (rspamd_mempool_t *pool,
const guchar *begin,
gsize len,
gsize *outlen)
{
auto sv = rspamd::css::unescape_css(pool, {(const char*)begin, len});
const auto *v = sv.begin();
if (outlen) {
*outlen = sv.size();
}
return v;
}
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