1/* $OpenBSD: utf8.c,v 1.8 2018/08/21 13:56:27 schwarze Exp $ */
2/*
3 * Copyright (c) 2016 Ingo Schwarze <schwarze@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18/*
19 * Utility functions for multibyte-character handling,
20 * in particular to sanitize untrusted strings for terminal output.
21 */
22
23#include "includes.h"
24
25#include <sys/types.h>
26#ifdef HAVE_LANGINFO_H
27# include <langinfo.h>
28#endif
29#include <limits.h>
30#include <locale.h>
31#include <stdarg.h>
32#include <stdio.h>
33#include <stdlib.h>
34#include <string.h>
35#if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H) && !defined(BROKEN_STRNVIS)
36# include <vis.h>
37#endif
38#ifdef HAVE_WCHAR_H
39# include <wchar.h>
40#endif
41
42#include "utf8.h"
43
44static int	 dangerous_locale(void);
45static int	 grow_dst(char **, size_t *, size_t, char **, size_t);
46static int	 vasnmprintf(char **, size_t, int *, const char *, va_list);
47
48
49/*
50 * For US-ASCII and UTF-8 encodings, we can safely recover from
51 * encoding errors and from non-printable characters.  For any
52 * other encodings, err to the side of caution and abort parsing:
53 * For state-dependent encodings, recovery is impossible.
54 * For arbitrary encodings, replacement of non-printable
55 * characters would be non-trivial and too fragile.
56 * The comments indicate what nl_langinfo(CODESET)
57 * returns for US-ASCII on various operating systems.
58 */
59
60static int
61dangerous_locale(void) {
62	char	*loc;
63
64	loc = nl_langinfo(CODESET);
65	return strcmp(loc, "UTF-8") != 0 &&
66	    strcmp(loc, "US-ASCII") != 0 &&		/* OpenBSD */
67	    strcmp(loc, "ANSI_X3.4-1968") != 0 &&	/* Linux */
68	    strcmp(loc, "ISO8859-1") != 0 &&		/* AIX */
69	    strcmp(loc, "646") != 0 &&			/* Solaris, NetBSD */
70	    strcmp(loc, "") != 0;			/* Solaris 6 */
71}
72
73static int
74grow_dst(char **dst, size_t *sz, size_t maxsz, char **dp, size_t need)
75{
76	char	*tp;
77	size_t	 tsz;
78
79	if (*dp + need < *dst + *sz)
80		return 0;
81	tsz = *sz + 128;
82	if (tsz > maxsz)
83		tsz = maxsz;
84	if ((tp = recallocarray(*dst, *sz, tsz, 1)) == NULL)
85		return -1;
86	*dp = tp + (*dp - *dst);
87	*dst = tp;
88	*sz = tsz;
89	return 0;
90}
91
92/*
93 * The following two functions limit the number of bytes written,
94 * including the terminating '\0', to sz.  Unless wp is NULL,
95 * they limit the number of display columns occupied to *wp.
96 * Whichever is reached first terminates the output string.
97 * To stay close to the standard interfaces, they return the number of
98 * non-NUL bytes that would have been written if both were unlimited.
99 * If wp is NULL, newline, carriage return, and tab are allowed;
100 * otherwise, the actual number of columns occupied by what was
101 * written is returned in *wp.
102 */
103
104static int
105vasnmprintf(char **str, size_t maxsz, int *wp, const char *fmt, va_list ap)
106{
107	char	*src;	/* Source string returned from vasprintf. */
108	char	*sp;	/* Pointer into src. */
109	char	*dst;	/* Destination string to be returned. */
110	char	*dp;	/* Pointer into dst. */
111	char	*tp;	/* Temporary pointer for dst. */
112	size_t	 sz;	/* Number of bytes allocated for dst. */
113	wchar_t	 wc;	/* Wide character at sp. */
114	int	 len;	/* Number of bytes in the character at sp. */
115	int	 ret;	/* Number of bytes needed to format src. */
116	int	 width;	/* Display width of the character wc. */
117	int	 total_width, max_width, print;
118
119	src = NULL;
120	if ((ret = vasprintf(&src, fmt, ap)) <= 0)
121		goto fail;
122
123	sz = strlen(src) + 1;
124	if ((dst = malloc(sz)) == NULL) {
125		free(src);
126		ret = -1;
127		goto fail;
128	}
129
130	if (maxsz > INT_MAX)
131		maxsz = INT_MAX;
132
133	sp = src;
134	dp = dst;
135	ret = 0;
136	print = 1;
137	total_width = 0;
138	max_width = wp == NULL ? INT_MAX : *wp;
139	while (*sp != '\0') {
140		if ((len = mbtowc(&wc, sp, MB_CUR_MAX)) == -1) {
141			(void)mbtowc(NULL, NULL, MB_CUR_MAX);
142			if (dangerous_locale()) {
143				ret = -1;
144				break;
145			}
146			len = 1;
147			width = -1;
148		} else if (wp == NULL &&
149		    (wc == L'\n' || wc == L'\r' || wc == L'\t')) {
150			/*
151			 * Don't use width uninitialized; the actual
152			 * value doesn't matter because total_width
153			 * is only returned for wp != NULL.
154			 */
155			width = 0;
156		} else if ((width = wcwidth(wc)) == -1 &&
157		    dangerous_locale()) {
158			ret = -1;
159			break;
160		}
161
162		/* Valid, printable character. */
163
164		if (width >= 0) {
165			if (print && (dp - dst >= (int)maxsz - len ||
166			    total_width > max_width - width))
167				print = 0;
168			if (print) {
169				if (grow_dst(&dst, &sz, maxsz,
170				    &dp, len) == -1) {
171					ret = -1;
172					break;
173				}
174				total_width += width;
175				memcpy(dp, sp, len);
176				dp += len;
177			}
178			sp += len;
179			if (ret >= 0)
180				ret += len;
181			continue;
182		}
183
184		/* Escaping required. */
185
186		while (len > 0) {
187			if (print && (dp - dst >= (int)maxsz - 4 ||
188			    total_width > max_width - 4))
189				print = 0;
190			if (print) {
191				if (grow_dst(&dst, &sz, maxsz,
192				    &dp, 4) == -1) {
193					ret = -1;
194					break;
195				}
196				tp = vis(dp, *sp, VIS_OCTAL | VIS_ALL, 0);
197				width = tp - dp;
198				total_width += width;
199				dp = tp;
200			} else
201				width = 4;
202			len--;
203			sp++;
204			if (ret >= 0)
205				ret += width;
206		}
207		if (len > 0)
208			break;
209	}
210	free(src);
211	*dp = '\0';
212	*str = dst;
213	if (wp != NULL)
214		*wp = total_width;
215
216	/*
217	 * If the string was truncated by the width limit but
218	 * would have fit into the size limit, the only sane way
219	 * to report the problem is using the return value, such
220	 * that the usual idiom "if (ret < 0 || ret >= sz) error"
221	 * works as expected.
222	 */
223
224	if (ret < (int)maxsz && !print)
225		ret = -1;
226	return ret;
227
228fail:
229	if (wp != NULL)
230		*wp = 0;
231	if (ret == 0) {
232		*str = src;
233		return 0;
234	} else {
235		*str = NULL;
236		return -1;
237	}
238}
239
240int
241snmprintf(char *str, size_t sz, int *wp, const char *fmt, ...)
242{
243	va_list	 ap;
244	char	*cp;
245	int	 ret;
246
247	va_start(ap, fmt);
248	ret = vasnmprintf(&cp, sz, wp, fmt, ap);
249	va_end(ap);
250	if (cp != NULL) {
251		(void)strlcpy(str, cp, sz);
252		free(cp);
253	} else
254		*str = '\0';
255	return ret;
256}
257
258/*
259 * To stay close to the standard interfaces, the following functions
260 * return the number of non-NUL bytes written.
261 */
262
263int
264vfmprintf(FILE *stream, const char *fmt, va_list ap)
265{
266	char	*str;
267	int	 ret;
268
269	if ((ret = vasnmprintf(&str, INT_MAX, NULL, fmt, ap)) < 0)
270		return -1;
271	if (fputs(str, stream) == EOF)
272		ret = -1;
273	free(str);
274	return ret;
275}
276
277int
278fmprintf(FILE *stream, const char *fmt, ...)
279{
280	va_list	 ap;
281	int	 ret;
282
283	va_start(ap, fmt);
284	ret = vfmprintf(stream, fmt, ap);
285	va_end(ap);
286	return ret;
287}
288
289int
290mprintf(const char *fmt, ...)
291{
292	va_list	 ap;
293	int	 ret;
294
295	va_start(ap, fmt);
296	ret = vfmprintf(stdout, fmt, ap);
297	va_end(ap);
298	return ret;
299}
300
301/*
302 * Set up libc for multibyte output in the user's chosen locale.
303 *
304 * XXX: we are known to have problems with Turkish (i/I confusion) so we
305 *      deliberately fall back to the C locale for now. Longer term we should
306 *      always prefer to select C.[encoding] if possible, but there's no
307 *      standardisation in locales between systems, so we'll need to survey
308 *      what's out there first.
309 */
310void
311msetlocale(void)
312{
313	const char *vars[] = { "LC_ALL", "LC_CTYPE", "LANG", NULL };
314	char *cp;
315	int i;
316
317	/*
318	 * We can't yet cope with dotless/dotted I in Turkish locales,
319	 * so fall back to the C locale for these.
320	 */
321	for (i = 0; vars[i] != NULL; i++) {
322		if ((cp = getenv(vars[i])) == NULL)
323			continue;
324		if (strncasecmp(cp, "TR", 2) != 0)
325			break;
326		/*
327		 * If we're in a UTF-8 locale then prefer to use
328		 * the C.UTF-8 locale (or equivalent) if it exists.
329		 */
330		if ((strcasestr(cp, "UTF-8") != NULL ||
331		    strcasestr(cp, "UTF8") != NULL) &&
332		    (setlocale(LC_CTYPE, "C.UTF-8") != NULL ||
333		    setlocale(LC_CTYPE, "POSIX.UTF-8") != NULL))
334			return;
335		setlocale(LC_CTYPE, "C");
336		return;
337	}
338	/* We can handle this locale */
339	setlocale(LC_CTYPE, "");
340}
341