xref: /openssh-portable/utf8.c (revision 011c8ffb)
1 /* $OpenBSD: utf8.c,v 1.5 2017/02/19 00:10:57 djm 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;
65 }
66 
67 static int
68 grow_dst(char **dst, size_t *sz, size_t maxsz, char **dp, size_t need)
69 {
70 	char	*tp;
71 	size_t	 tsz;
72 
73 	if (*dp + need < *dst + *sz)
74 		return 0;
75 	tsz = *sz + 128;
76 	if (tsz > maxsz)
77 		tsz = maxsz;
78 	if ((tp = realloc(*dst, tsz)) == NULL)
79 		return -1;
80 	*dp = tp + (*dp - *dst);
81 	*dst = tp;
82 	*sz = tsz;
83 	return 0;
84 }
85 
86 /*
87  * The following two functions limit the number of bytes written,
88  * including the terminating '\0', to sz.  Unless wp is NULL,
89  * they limit the number of display columns occupied to *wp.
90  * Whichever is reached first terminates the output string.
91  * To stay close to the standard interfaces, they return the number of
92  * non-NUL bytes that would have been written if both were unlimited.
93  * If wp is NULL, newline, carriage return, and tab are allowed;
94  * otherwise, the actual number of columns occupied by what was
95  * written is returned in *wp.
96  */
97 
98 static int
99 vasnmprintf(char **str, size_t maxsz, int *wp, const char *fmt, va_list ap)
100 {
101 	char	*src;	/* Source string returned from vasprintf. */
102 	char	*sp;	/* Pointer into src. */
103 	char	*dst;	/* Destination string to be returned. */
104 	char	*dp;	/* Pointer into dst. */
105 	char	*tp;	/* Temporary pointer for dst. */
106 	size_t	 sz;	/* Number of bytes allocated for dst. */
107 	wchar_t	 wc;	/* Wide character at sp. */
108 	int	 len;	/* Number of bytes in the character at sp. */
109 	int	 ret;	/* Number of bytes needed to format src. */
110 	int	 width;	/* Display width of the character wc. */
111 	int	 total_width, max_width, print;
112 
113 	src = NULL;
114 	if ((ret = vasprintf(&src, fmt, ap)) <= 0)
115 		goto fail;
116 
117 	sz = strlen(src) + 1;
118 	if ((dst = malloc(sz)) == NULL) {
119 		free(src);
120 		ret = -1;
121 		goto fail;
122 	}
123 
124 	if (maxsz > INT_MAX)
125 		maxsz = INT_MAX;
126 
127 	sp = src;
128 	dp = dst;
129 	ret = 0;
130 	print = 1;
131 	total_width = 0;
132 	max_width = wp == NULL ? INT_MAX : *wp;
133 	while (*sp != '\0') {
134 		if ((len = mbtowc(&wc, sp, MB_CUR_MAX)) == -1) {
135 			(void)mbtowc(NULL, NULL, MB_CUR_MAX);
136 			if (dangerous_locale()) {
137 				ret = -1;
138 				break;
139 			}
140 			len = 1;
141 			width = -1;
142 		} else if (wp == NULL &&
143 		    (wc == L'\n' || wc == L'\r' || wc == L'\t')) {
144 			/*
145 			 * Don't use width uninitialized; the actual
146 			 * value doesn't matter because total_width
147 			 * is only returned for wp != NULL.
148 			 */
149 			width = 0;
150 		} else if ((width = wcwidth(wc)) == -1 &&
151 		    dangerous_locale()) {
152 			ret = -1;
153 			break;
154 		}
155 
156 		/* Valid, printable character. */
157 
158 		if (width >= 0) {
159 			if (print && (dp - dst >= (int)maxsz - len ||
160 			    total_width > max_width - width))
161 				print = 0;
162 			if (print) {
163 				if (grow_dst(&dst, &sz, maxsz,
164 				    &dp, len) == -1) {
165 					ret = -1;
166 					break;
167 				}
168 				total_width += width;
169 				memcpy(dp, sp, len);
170 				dp += len;
171 			}
172 			sp += len;
173 			if (ret >= 0)
174 				ret += len;
175 			continue;
176 		}
177 
178 		/* Escaping required. */
179 
180 		while (len > 0) {
181 			if (print && (dp - dst >= (int)maxsz - 4 ||
182 			    total_width > max_width - 4))
183 				print = 0;
184 			if (print) {
185 				if (grow_dst(&dst, &sz, maxsz,
186 				    &dp, 4) == -1) {
187 					ret = -1;
188 					break;
189 				}
190 				tp = vis(dp, *sp, VIS_OCTAL | VIS_ALL, 0);
191 				width = tp - dp;
192 				total_width += width;
193 				dp = tp;
194 			} else
195 				width = 4;
196 			len--;
197 			sp++;
198 			if (ret >= 0)
199 				ret += width;
200 		}
201 		if (len > 0)
202 			break;
203 	}
204 	free(src);
205 	*dp = '\0';
206 	*str = dst;
207 	if (wp != NULL)
208 		*wp = total_width;
209 
210 	/*
211 	 * If the string was truncated by the width limit but
212 	 * would have fit into the size limit, the only sane way
213 	 * to report the problem is using the return value, such
214 	 * that the usual idiom "if (ret < 0 || ret >= sz) error"
215 	 * works as expected.
216 	 */
217 
218 	if (ret < (int)maxsz && !print)
219 		ret = -1;
220 	return ret;
221 
222 fail:
223 	if (wp != NULL)
224 		*wp = 0;
225 	if (ret == 0) {
226 		*str = src;
227 		return 0;
228 	} else {
229 		*str = NULL;
230 		return -1;
231 	}
232 }
233 
234 int
235 snmprintf(char *str, size_t sz, int *wp, const char *fmt, ...)
236 {
237 	va_list	 ap;
238 	char	*cp;
239 	int	 ret;
240 
241 	va_start(ap, fmt);
242 	ret = vasnmprintf(&cp, sz, wp, fmt, ap);
243 	va_end(ap);
244 	if (cp != NULL) {
245 		(void)strlcpy(str, cp, sz);
246 		free(cp);
247 	} else
248 		*str = '\0';
249 	return ret;
250 }
251 
252 /*
253  * To stay close to the standard interfaces, the following functions
254  * return the number of non-NUL bytes written.
255  */
256 
257 int
258 vfmprintf(FILE *stream, const char *fmt, va_list ap)
259 {
260 	char	*str;
261 	int	 ret;
262 
263 	if ((ret = vasnmprintf(&str, INT_MAX, NULL, fmt, ap)) < 0)
264 		return -1;
265 	if (fputs(str, stream) == EOF)
266 		ret = -1;
267 	free(str);
268 	return ret;
269 }
270 
271 int
272 fmprintf(FILE *stream, const char *fmt, ...)
273 {
274 	va_list	 ap;
275 	int	 ret;
276 
277 	va_start(ap, fmt);
278 	ret = vfmprintf(stream, fmt, ap);
279 	va_end(ap);
280 	return ret;
281 }
282 
283 int
284 mprintf(const char *fmt, ...)
285 {
286 	va_list	 ap;
287 	int	 ret;
288 
289 	va_start(ap, fmt);
290 	ret = vfmprintf(stdout, fmt, ap);
291 	va_end(ap);
292 	return ret;
293 }
294 
295 /*
296  * Set up libc for multibyte output in the user's chosen locale.
297  *
298  * XXX: we are known to have problems with Turkish (i/I confusion) so we
299  *      deliberately fall back to the C locale for now. Longer term we should
300  *      always prefer to select C.[encoding] if possible, but there's no
301  *      standardisation in locales between systems, so we'll need to survey
302  *      what's out there first.
303  */
304 void
305 msetlocale(void)
306 {
307 	const char *vars[] = { "LC_ALL", "LC_CTYPE", "LANG", NULL };
308 	char *cp;
309 	int i;
310 
311 	/*
312 	 * We can't yet cope with dotless/dotted I in Turkish locales,
313 	 * so fall back to the C locale for these.
314 	 */
315 	for (i = 0; vars[i] != NULL; i++) {
316 		if ((cp = getenv(vars[i])) == NULL)
317 			continue;
318 		if (strncasecmp(cp, "TR", 2) != 0)
319 			break;
320 		/*
321 		 * If we're in a UTF-8 locale then prefer to use
322 		 * the C.UTF-8 locale (or equivalent) if it exists.
323 		 */
324 		if ((strcasestr(cp, "UTF-8") != NULL ||
325 		    strcasestr(cp, "UTF8") != NULL) &&
326 		    (setlocale(LC_CTYPE, "C.UTF-8") != NULL ||
327 		    setlocale(LC_CTYPE, "POSIX.UTF-8") != NULL))
328 			return;
329 		setlocale(LC_CTYPE, "C");
330 		return;
331 	}
332 	/* We can handle this locale */
333 	setlocale(LC_CTYPE, "");
334 }
335