xref: /openssh-portable/utf8.c (revision f8500b2b)
1 /* $OpenBSD: utf8.c,v 1.6 2017/04/17 14:31:23 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 
44 static int	 dangerous_locale(void);
45 static int	 grow_dst(char **, size_t *, size_t, char **, size_t);
46 static 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  */
57 
58 static int
59 dangerous_locale(void) {
60 	char	*loc;
61 
62 	loc = nl_langinfo(CODESET);
63 	return strcmp(loc, "US-ASCII") != 0 && strcmp(loc, "UTF-8") != 0 &&
64 	    strcmp(loc, "ANSI_X3.4-1968") != 0 && strcmp(loc, "646") != 0 &&
65 	    strcmp(loc, "") != 0;
66 }
67 
68 static int
69 grow_dst(char **dst, size_t *sz, size_t maxsz, char **dp, size_t need)
70 {
71 	char	*tp;
72 	size_t	 tsz;
73 
74 	if (*dp + need < *dst + *sz)
75 		return 0;
76 	tsz = *sz + 128;
77 	if (tsz > maxsz)
78 		tsz = maxsz;
79 	if ((tp = realloc(*dst, tsz)) == NULL)
80 		return -1;
81 	*dp = tp + (*dp - *dst);
82 	*dst = tp;
83 	*sz = tsz;
84 	return 0;
85 }
86 
87 /*
88  * The following two functions limit the number of bytes written,
89  * including the terminating '\0', to sz.  Unless wp is NULL,
90  * they limit the number of display columns occupied to *wp.
91  * Whichever is reached first terminates the output string.
92  * To stay close to the standard interfaces, they return the number of
93  * non-NUL bytes that would have been written if both were unlimited.
94  * If wp is NULL, newline, carriage return, and tab are allowed;
95  * otherwise, the actual number of columns occupied by what was
96  * written is returned in *wp.
97  */
98 
99 static int
100 vasnmprintf(char **str, size_t maxsz, int *wp, const char *fmt, va_list ap)
101 {
102 	char	*src;	/* Source string returned from vasprintf. */
103 	char	*sp;	/* Pointer into src. */
104 	char	*dst;	/* Destination string to be returned. */
105 	char	*dp;	/* Pointer into dst. */
106 	char	*tp;	/* Temporary pointer for dst. */
107 	size_t	 sz;	/* Number of bytes allocated for dst. */
108 	wchar_t	 wc;	/* Wide character at sp. */
109 	int	 len;	/* Number of bytes in the character at sp. */
110 	int	 ret;	/* Number of bytes needed to format src. */
111 	int	 width;	/* Display width of the character wc. */
112 	int	 total_width, max_width, print;
113 
114 	src = NULL;
115 	if ((ret = vasprintf(&src, fmt, ap)) <= 0)
116 		goto fail;
117 
118 	sz = strlen(src) + 1;
119 	if ((dst = malloc(sz)) == NULL) {
120 		free(src);
121 		ret = -1;
122 		goto fail;
123 	}
124 
125 	if (maxsz > INT_MAX)
126 		maxsz = INT_MAX;
127 
128 	sp = src;
129 	dp = dst;
130 	ret = 0;
131 	print = 1;
132 	total_width = 0;
133 	max_width = wp == NULL ? INT_MAX : *wp;
134 	while (*sp != '\0') {
135 		if ((len = mbtowc(&wc, sp, MB_CUR_MAX)) == -1) {
136 			(void)mbtowc(NULL, NULL, MB_CUR_MAX);
137 			if (dangerous_locale()) {
138 				ret = -1;
139 				break;
140 			}
141 			len = 1;
142 			width = -1;
143 		} else if (wp == NULL &&
144 		    (wc == L'\n' || wc == L'\r' || wc == L'\t')) {
145 			/*
146 			 * Don't use width uninitialized; the actual
147 			 * value doesn't matter because total_width
148 			 * is only returned for wp != NULL.
149 			 */
150 			width = 0;
151 		} else if ((width = wcwidth(wc)) == -1 &&
152 		    dangerous_locale()) {
153 			ret = -1;
154 			break;
155 		}
156 
157 		/* Valid, printable character. */
158 
159 		if (width >= 0) {
160 			if (print && (dp - dst >= (int)maxsz - len ||
161 			    total_width > max_width - width))
162 				print = 0;
163 			if (print) {
164 				if (grow_dst(&dst, &sz, maxsz,
165 				    &dp, len) == -1) {
166 					ret = -1;
167 					break;
168 				}
169 				total_width += width;
170 				memcpy(dp, sp, len);
171 				dp += len;
172 			}
173 			sp += len;
174 			if (ret >= 0)
175 				ret += len;
176 			continue;
177 		}
178 
179 		/* Escaping required. */
180 
181 		while (len > 0) {
182 			if (print && (dp - dst >= (int)maxsz - 4 ||
183 			    total_width > max_width - 4))
184 				print = 0;
185 			if (print) {
186 				if (grow_dst(&dst, &sz, maxsz,
187 				    &dp, 4) == -1) {
188 					ret = -1;
189 					break;
190 				}
191 				tp = vis(dp, *sp, VIS_OCTAL | VIS_ALL, 0);
192 				width = tp - dp;
193 				total_width += width;
194 				dp = tp;
195 			} else
196 				width = 4;
197 			len--;
198 			sp++;
199 			if (ret >= 0)
200 				ret += width;
201 		}
202 		if (len > 0)
203 			break;
204 	}
205 	free(src);
206 	*dp = '\0';
207 	*str = dst;
208 	if (wp != NULL)
209 		*wp = total_width;
210 
211 	/*
212 	 * If the string was truncated by the width limit but
213 	 * would have fit into the size limit, the only sane way
214 	 * to report the problem is using the return value, such
215 	 * that the usual idiom "if (ret < 0 || ret >= sz) error"
216 	 * works as expected.
217 	 */
218 
219 	if (ret < (int)maxsz && !print)
220 		ret = -1;
221 	return ret;
222 
223 fail:
224 	if (wp != NULL)
225 		*wp = 0;
226 	if (ret == 0) {
227 		*str = src;
228 		return 0;
229 	} else {
230 		*str = NULL;
231 		return -1;
232 	}
233 }
234 
235 int
236 snmprintf(char *str, size_t sz, int *wp, const char *fmt, ...)
237 {
238 	va_list	 ap;
239 	char	*cp;
240 	int	 ret;
241 
242 	va_start(ap, fmt);
243 	ret = vasnmprintf(&cp, sz, wp, fmt, ap);
244 	va_end(ap);
245 	if (cp != NULL) {
246 		(void)strlcpy(str, cp, sz);
247 		free(cp);
248 	} else
249 		*str = '\0';
250 	return ret;
251 }
252 
253 /*
254  * To stay close to the standard interfaces, the following functions
255  * return the number of non-NUL bytes written.
256  */
257 
258 int
259 vfmprintf(FILE *stream, const char *fmt, va_list ap)
260 {
261 	char	*str;
262 	int	 ret;
263 
264 	if ((ret = vasnmprintf(&str, INT_MAX, NULL, fmt, ap)) < 0)
265 		return -1;
266 	if (fputs(str, stream) == EOF)
267 		ret = -1;
268 	free(str);
269 	return ret;
270 }
271 
272 int
273 fmprintf(FILE *stream, const char *fmt, ...)
274 {
275 	va_list	 ap;
276 	int	 ret;
277 
278 	va_start(ap, fmt);
279 	ret = vfmprintf(stream, fmt, ap);
280 	va_end(ap);
281 	return ret;
282 }
283 
284 int
285 mprintf(const char *fmt, ...)
286 {
287 	va_list	 ap;
288 	int	 ret;
289 
290 	va_start(ap, fmt);
291 	ret = vfmprintf(stdout, fmt, ap);
292 	va_end(ap);
293 	return ret;
294 }
295 
296 /*
297  * Set up libc for multibyte output in the user's chosen locale.
298  *
299  * XXX: we are known to have problems with Turkish (i/I confusion) so we
300  *      deliberately fall back to the C locale for now. Longer term we should
301  *      always prefer to select C.[encoding] if possible, but there's no
302  *      standardisation in locales between systems, so we'll need to survey
303  *      what's out there first.
304  */
305 void
306 msetlocale(void)
307 {
308 	const char *vars[] = { "LC_ALL", "LC_CTYPE", "LANG", NULL };
309 	char *cp;
310 	int i;
311 
312 	/*
313 	 * We can't yet cope with dotless/dotted I in Turkish locales,
314 	 * so fall back to the C locale for these.
315 	 */
316 	for (i = 0; vars[i] != NULL; i++) {
317 		if ((cp = getenv(vars[i])) == NULL)
318 			continue;
319 		if (strncasecmp(cp, "TR", 2) != 0)
320 			break;
321 		/*
322 		 * If we're in a UTF-8 locale then prefer to use
323 		 * the C.UTF-8 locale (or equivalent) if it exists.
324 		 */
325 		if ((strcasestr(cp, "UTF-8") != NULL ||
326 		    strcasestr(cp, "UTF8") != NULL) &&
327 		    (setlocale(LC_CTYPE, "C.UTF-8") != NULL ||
328 		    setlocale(LC_CTYPE, "POSIX.UTF-8") != NULL))
329 			return;
330 		setlocale(LC_CTYPE, "C");
331 		return;
332 	}
333 	/* We can handle this locale */
334 	setlocale(LC_CTYPE, "");
335 }
336