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Systemd/src/basic/escape.c
Zbigniew Jędrzejewski-Szmek 3565e09594 basic/escape: merge utf8 and non-utf8 paths in cunescape_one 
Not every byte sequence is valid utf8. We allow escaping of non-utf8
sequences in strings by using octal and hexadecimal escape sequences
(\123 and \0xAB) for bytes at or above 128. Users of cunescape_one
could infer whether such use occured when they received an answer
between 128 and 256 in *ret (a non-ascii one byte character). But this
is subtle and misleading: the comments were wrong, because ascii is a
subset of unicode, so c != 0 did not mean non-unicode, but rather
ascii-subset-of-unicode-or-raw-byte. This was all rather confusing, so
make the "single byte" condition explicit.

I'm not convinced that allowing non-utf8 sequences to be produced is
useful in all cases where we allow it (e.g. in config files), but that
behaviour is unchanged, just made more explicit.

This also fixes an (invalid) gcc warning about unitialized variable
(*ret_unicode) in callers of cunescape_one.
2016-01-18 15:20:32 -05:00

477 lines
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd 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.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "alloc-util.h"
#include "escape.h"
#include "hexdecoct.h"
#include "macro.h"
#include "utf8.h"
size_t cescape_char(char c, char *buf) {
char * buf_old = buf;
switch (c) {
case '\a':
*(buf++) = '\\';
*(buf++) = 'a';
break;
case '\b':
*(buf++) = '\\';
*(buf++) = 'b';
break;
case '\f':
*(buf++) = '\\';
*(buf++) = 'f';
break;
case '\n':
*(buf++) = '\\';
*(buf++) = 'n';
break;
case '\r':
*(buf++) = '\\';
*(buf++) = 'r';
break;
case '\t':
*(buf++) = '\\';
*(buf++) = 't';
break;
case '\v':
*(buf++) = '\\';
*(buf++) = 'v';
break;
case '\\':
*(buf++) = '\\';
*(buf++) = '\\';
break;
case '"':
*(buf++) = '\\';
*(buf++) = '"';
break;
case '\'':
*(buf++) = '\\';
*(buf++) = '\'';
break;
default:
/* For special chars we prefer octal over
* hexadecimal encoding, simply because glib's
* g_strescape() does the same */
if ((c < ' ') || (c >= 127)) {
*(buf++) = '\\';
*(buf++) = octchar((unsigned char) c >> 6);
*(buf++) = octchar((unsigned char) c >> 3);
*(buf++) = octchar((unsigned char) c);
} else
*(buf++) = c;
break;
}
return buf - buf_old;
}
char *cescape_length(const char *s, size_t n) {
const char *f;
char *r, *t;
assert(s || n == 0);
/* Does C style string escaping. May be reversed with
* cunescape(). */
r = new(char, n*4 + 1);
if (!r)
return NULL;
for (f = s, t = r; f < s + n; f++)
t += cescape_char(*f, t);
*t = 0;
return r;
}
char *cescape(const char *s) {
assert(s);
return cescape_length(s, strlen(s));
}
int cunescape_one(const char *p, size_t length, uint32_t *ret, bool *eight_bit) {
int r = 1;
assert(p);
assert(*p);
assert(ret);
/* Unescapes C style. Returns the unescaped character in ret.
* Sets *eight_bit to true if the escaped sequence either fits in
* one byte in UTF-8 or is a non-unicode literal byte and should
* instead be copied directly.
*/
if (length != (size_t) -1 && length < 1)
return -EINVAL;
switch (p[0]) {
case 'a':
*ret = '\a';
break;
case 'b':
*ret = '\b';
break;
case 'f':
*ret = '\f';
break;
case 'n':
*ret = '\n';
break;
case 'r':
*ret = '\r';
break;
case 't':
*ret = '\t';
break;
case 'v':
*ret = '\v';
break;
case '\\':
*ret = '\\';
break;
case '"':
*ret = '"';
break;
case '\'':
*ret = '\'';
break;
case 's':
/* This is an extension of the XDG syntax files */
*ret = ' ';
break;
case 'x': {
/* hexadecimal encoding */
int a, b;
if (length != (size_t) -1 && length < 3)
return -EINVAL;
a = unhexchar(p[1]);
if (a < 0)
return -EINVAL;
b = unhexchar(p[2]);
if (b < 0)
return -EINVAL;
/* Don't allow NUL bytes */
if (a == 0 && b == 0)
return -EINVAL;
*ret = (a << 4U) | b;
*eight_bit = true;
r = 3;
break;
}
case 'u': {
/* C++11 style 16bit unicode */
int a[4];
unsigned i;
uint32_t c;
if (length != (size_t) -1 && length < 5)
return -EINVAL;
for (i = 0; i < 4; i++) {
a[i] = unhexchar(p[1 + i]);
if (a[i] < 0)
return a[i];
}
c = ((uint32_t) a[0] << 12U) | ((uint32_t) a[1] << 8U) | ((uint32_t) a[2] << 4U) | (uint32_t) a[3];
/* Don't allow 0 chars */
if (c == 0)
return -EINVAL;
*ret = c;
r = 5;
break;
}
case 'U': {
/* C++11 style 32bit unicode */
int a[8];
unsigned i;
uint32_t c;
if (length != (size_t) -1 && length < 9)
return -EINVAL;
for (i = 0; i < 8; i++) {
a[i] = unhexchar(p[1 + i]);
if (a[i] < 0)
return a[i];
}
c = ((uint32_t) a[0] << 28U) | ((uint32_t) a[1] << 24U) | ((uint32_t) a[2] << 20U) | ((uint32_t) a[3] << 16U) |
((uint32_t) a[4] << 12U) | ((uint32_t) a[5] << 8U) | ((uint32_t) a[6] << 4U) | (uint32_t) a[7];
/* Don't allow 0 chars */
if (c == 0)
return -EINVAL;
/* Don't allow invalid code points */
if (!unichar_is_valid(c))
return -EINVAL;
*ret = c;
r = 9;
break;
}
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7': {
/* octal encoding */
int a, b, c;
uint32_t m;
if (length != (size_t) -1 && length < 3)
return -EINVAL;
a = unoctchar(p[0]);
if (a < 0)
return -EINVAL;
b = unoctchar(p[1]);
if (b < 0)
return -EINVAL;
c = unoctchar(p[2]);
if (c < 0)
return -EINVAL;
/* don't allow NUL bytes */
if (a == 0 && b == 0 && c == 0)
return -EINVAL;
/* Don't allow bytes above 255 */
m = ((uint32_t) a << 6U) | ((uint32_t) b << 3U) | (uint32_t) c;
if (m > 255)
return -EINVAL;
*ret = m;
*eight_bit = true;
r = 3;
break;
}
default:
return -EINVAL;
}
return r;
}
int cunescape_length_with_prefix(const char *s, size_t length, const char *prefix, UnescapeFlags flags, char **ret) {
char *r, *t;
const char *f;
size_t pl;
assert(s);
assert(ret);
/* Undoes C style string escaping, and optionally prefixes it. */
pl = prefix ? strlen(prefix) : 0;
r = new(char, pl+length+1);
if (!r)
return -ENOMEM;
if (prefix)
memcpy(r, prefix, pl);
for (f = s, t = r + pl; f < s + length; f++) {
size_t remaining;
uint32_t u;
bool eight_bit = false;
int k;
remaining = s + length - f;
assert(remaining > 0);
if (*f != '\\') {
/* A literal literal, copy verbatim */
*(t++) = *f;
continue;
}
if (remaining == 1) {
if (flags & UNESCAPE_RELAX) {
/* A trailing backslash, copy verbatim */
*(t++) = *f;
continue;
}
free(r);
return -EINVAL;
}
k = cunescape_one(f + 1, remaining - 1, &u, &eight_bit);
if (k < 0) {
if (flags & UNESCAPE_RELAX) {
/* Invalid escape code, let's take it literal then */
*(t++) = '\\';
continue;
}
free(r);
return k;
}
f += k;
if (eight_bit)
/* One byte? Set directly as specified */
*(t++) = u;
else
/* Otherwise encode as multi-byte UTF-8 */
t += utf8_encode_unichar(t, u);
}
*t = 0;
*ret = r;
return t - r;
}
int cunescape_length(const char *s, size_t length, UnescapeFlags flags, char **ret) {
return cunescape_length_with_prefix(s, length, NULL, flags, ret);
}
int cunescape(const char *s, UnescapeFlags flags, char **ret) {
return cunescape_length(s, strlen(s), flags, ret);
}
char *xescape(const char *s, const char *bad) {
char *r, *t;
const char *f;
/* Escapes all chars in bad, in addition to \ and all special
* chars, in \xFF style escaping. May be reversed with
* cunescape(). */
r = new(char, strlen(s) * 4 + 1);
if (!r)
return NULL;
for (f = s, t = r; *f; f++) {
if ((*f < ' ') || (*f >= 127) ||
(*f == '\\') || strchr(bad, *f)) {
*(t++) = '\\';
*(t++) = 'x';
*(t++) = hexchar(*f >> 4);
*(t++) = hexchar(*f);
} else
*(t++) = *f;
}
*t = 0;
return r;
}
static char *strcpy_backslash_escaped(char *t, const char *s, const char *bad) {
assert(bad);
for (; *s; s++) {
if (*s == '\\' || strchr(bad, *s))
*(t++) = '\\';
*(t++) = *s;
}
return t;
}
char *shell_escape(const char *s, const char *bad) {
char *r, *t;
r = new(char, strlen(s)*2+1);
if (!r)
return NULL;
t = strcpy_backslash_escaped(r, s, bad);
*t = 0;
return r;
}
char *shell_maybe_quote(const char *s) {
const char *p;
char *r, *t;
assert(s);
/* Encloses a string in double quotes if necessary to make it
* OK as shell string. */
for (p = s; *p; p++)
if (*p <= ' ' ||
*p >= 127 ||
strchr(SHELL_NEED_QUOTES, *p))
break;
if (!*p)
return strdup(s);
r = new(char, 1+strlen(s)*2+1+1);
if (!r)
return NULL;
t = r;
*(t++) = '"';
t = mempcpy(t, s, p - s);
t = strcpy_backslash_escaped(t, p, SHELL_NEED_ESCAPE);
*(t++)= '"';
*t = 0;
return r;
}
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