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Systemd/src/basic/escape.c
Zbigniew Jędrzejewski-Szmek 804ee07c13 Use "dollar-single-quotes" to escape shell-sensitive strings 
Also called "ANSI-C Quoting" in info:(bash) ANSI-C Quoting.

The escaping rules are a POSIX proposal, and are described in
http://austingroupbugs.net/view.php?id=249. There's a lot of back-and-forth on
the details of escaping of control characters, but we'll be only using a small
subset of the syntax that is common to all proposals and is widely supported.
Unfortunately dash and fish and maybe some other shells do not support it (see
the man page patch for a list).

This allows environment variables to be safely exported using show-environment
and imported into the shell. Shells which do not support this syntax will have
to do something like
    export $(systemctl show-environment|grep -v '=\$')
or whatever is appropriate in their case. I think csh and fish do not support
the A=B syntax anyway, so the change is moot for them.

Fixes #5536.

v2:
- also escape newlines (which currently disallowed in shell values, so this
  doesn't really matter), and tabs (as $'\t'), and ! (as $'!'). This way quoted
  output can be included directly in both interactive and noninteractive bash.
2017-06-19 19:39:43 -04:00

523 lines
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/***
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, char32_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;
char32_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;
char32_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;
bool eight_bit = false;
char32_t u;
int k;
remaining = s + length - f;
assert(remaining > 0);
if (*f != '\\') {
/* A 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;
}
char *octescape(const char *s, size_t len) {
char *r, *t;
const char *f;
/* Escapes all chars in bad, in addition to \ and " chars,
* in \nnn style escaping. */
r = new(char, len * 4 + 1);
if (!r)
return NULL;
for (f = s, t = r; f < s + len; f++) {
if (*f < ' ' || *f >= 127 || *f == '\\' || *f == '"') {
*(t++) = '\\';
*(t++) = '0' + (*f >> 6);
*(t++) = '0' + ((*f >> 3) & 8);
*(t++) = '0' + (*f & 8);
} else
*(t++) = *f;
}
*t = 0;
return r;
}
static char *strcpy_backslash_escaped(char *t, const char *s, const char *bad, bool escape_tab_nl) {
assert(bad);
for (; *s; s++) {
if (escape_tab_nl && IN_SET(*s, '\n', '\t')) {
*(t++) = '\\';
*(t++) = *s == '\n' ? 'n' : 't';
continue;
}
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, false);
*t = 0;
return r;
}
char* shell_maybe_quote(const char *s, EscapeStyle style) {
const char *p;
char *r, *t;
assert(s);
/* Encloses a string in quotes if necessary to make it OK as a shell
* string. Note that we treat benign UTF-8 characters as needing
* escaping too, but that should be OK. */
for (p = s; *p; p++)
if (*p <= ' ' ||
*p >= 127 ||
strchr(SHELL_NEED_QUOTES, *p))
break;
if (!*p)
return strdup(s);
r = new(char, (style == ESCAPE_POSIX) + 1 + strlen(s)*2 + 1 + 1);
if (!r)
return NULL;
t = r;
if (style == ESCAPE_BACKSLASH)
*(t++) = '"';
else if (style == ESCAPE_POSIX) {
*(t++) = '$';
*(t++) = '\'';
} else
assert_not_reached("Bad EscapeStyle");
t = mempcpy(t, s, p - s);
if (style == ESCAPE_BACKSLASH)
t = strcpy_backslash_escaped(t, p, SHELL_NEED_ESCAPE, false);
else
t = strcpy_backslash_escaped(t, p, SHELL_NEED_ESCAPE_POSIX, true);
if (style == ESCAPE_BACKSLASH)
*(t++) = '"';
else
*(t++) = '\'';
*t = 0;
return r;
}
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