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566d06ae508ae2f23c555506434028239b2b5b21
systemd/src/basic/escape.c
Zbigniew Jędrzejewski-Szmek 566d06ae50 basic/escape: always escape newlines in shell_escape() 
shell_escape() is mostly used for mount paths and similar, where we assume
no newlines are present in the string. But if any were ever present, we
should escape them. So let's simplify the code by making this unconditional.
2021-05-05 12:12:42 +02:00

543 lines
15 KiB
C
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#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"
int cescape_char(char c, char *buf) {
char *buf_old = buf;
/* Needs space for 4 characters in the buffer */
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, bool accept_nul) {
int r = 1;
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_MAX && 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_MAX && 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 && !accept_nul)
return -EINVAL;
*ret = (a << 4U) | b;
*eight_bit = true;
r = 3;
break;
}
case 'u': {
/* C++11 style 16bit unicode */
int a[4];
size_t i;
uint32_t c;
if (length != SIZE_MAX && 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 && !accept_nul)
return -EINVAL;
*ret = c;
r = 5;
break;
}
case 'U': {
/* C++11 style 32bit unicode */
int a[8];
size_t i;
char32_t c;
if (length != SIZE_MAX && 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 && !accept_nul)
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_MAX && 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 && !accept_nul)
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 = strlen_ptr(prefix);
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, flags & UNESCAPE_ACCEPT_NUL);
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;
}
char* xescape_full(const char *s, const char *bad, size_t console_width, bool eight_bits) {
char *ans, *t, *prev, *prev2;
const char *f;
/* Escapes all chars in bad, in addition to \ and all special chars, in \xFF style escaping. May be
* reversed with cunescape(). If eight_bits is true, characters >= 127 are let through unchanged.
* This corresponds to non-ASCII printable characters in pre-unicode encodings.
*
* If console_width is reached, output is truncated and "..." is appended. */
if (console_width == 0)
return strdup("");
ans = new(char, MIN(strlen(s), console_width) * 4 + 1);
if (!ans)
return NULL;
memset(ans, '_', MIN(strlen(s), console_width) * 4);
ans[MIN(strlen(s), console_width) * 4] = 0;
for (f = s, t = prev = prev2 = ans; ; f++) {
char *tmp_t = t;
if (!*f) {
*t = 0;
return ans;
}
if ((unsigned char) *f < ' ' || (!eight_bits && (unsigned char) *f >= 127) ||
*f == '\\' || strchr(bad, *f)) {
if ((size_t) (t - ans) + 4 > console_width)
break;
*(t++) = '\\';
*(t++) = 'x';
*(t++) = hexchar(*f >> 4);
*(t++) = hexchar(*f);
} else {
if ((size_t) (t - ans) + 1 > console_width)
break;
*(t++) = *f;
}
/* We might need to go back two cycles to fit three dots, so remember two positions */
prev2 = prev;
prev = tmp_t;
}
/* We can just write where we want, since chars are one-byte */
size_t c = MIN(console_width, 3u); /* If the console is too narrow, write fewer dots */
size_t off;
if (console_width - c >= (size_t) (t - ans))
off = (size_t) (t - ans);
else if (console_width - c >= (size_t) (prev - ans))
off = (size_t) (prev - ans);
else if (console_width - c >= (size_t) (prev2 - ans))
off = (size_t) (prev2 - ans);
else
off = console_width - c;
assert(off <= (size_t) (t - ans));
memcpy(ans + off, "...", c);
ans[off + c] = '\0';
return ans;
}
char* escape_non_printable_full(const char *str, size_t console_width, bool eight_bit) {
if (eight_bit)
return xescape_full(str, "", console_width, true);
else
return utf8_escape_non_printable_full(str, console_width);
}
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 || IN_SET(*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) {
assert(bad);
for (; *s; s++) {
if (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);
*t = 0;
return r;
}
char* shell_maybe_quote(const char *s, ShellEscapeFlags flags) {
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. */
if (FLAGS_SET(flags, SHELL_ESCAPE_EMPTY) && isempty(s))
return strdup("\"\""); /* We don't use $'' here in the POSIX mode. "" is fine too. */
for (p = s; *p; p++)
if (*p <= ' ' ||
*p >= 127 ||
strchr(SHELL_NEED_QUOTES, *p))
break;
if (!*p)
return strdup(s);
r = new(char, FLAGS_SET(flags, SHELL_ESCAPE_POSIX) + 1 + strlen(s)*2 + 1 + 1);
if (!r)
return NULL;
t = r;
if (FLAGS_SET(flags, SHELL_ESCAPE_POSIX)) {
*(t++) = '$';
*(t++) = '\'';
} else
*(t++) = '"';
t = mempcpy(t, s, p - s);
t = strcpy_backslash_escaped(t, p,
FLAGS_SET(flags, SHELL_ESCAPE_POSIX) ? SHELL_NEED_ESCAPE_POSIX : SHELL_NEED_ESCAPE);
if (FLAGS_SET(flags, SHELL_ESCAPE_POSIX))
*(t++) = '\'';
else
*(t++) = '"';
*t = 0;
return r;
}
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