xref: /openssh-portable/utf8.c (revision b8ae02a2)
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 
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  * The comments indicate what nl_langinfo(CODESET)
57  * returns for US-ASCII on various operating systems.
58  */
59 
60 static int
dangerous_locale(void)61 dangerous_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 
73 static int
grow_dst(char ** dst,size_t * sz,size_t maxsz,char ** dp,size_t need)74 grow_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 
104 static int
vasnmprintf(char ** str,size_t maxsz,int * wp,const char * fmt,va_list ap)105 vasnmprintf(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 
228 fail:
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 
240 int
snmprintf(char * str,size_t sz,int * wp,const char * fmt,...)241 snmprintf(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 
263 int
vfmprintf(FILE * stream,const char * fmt,va_list ap)264 vfmprintf(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 
277 int
fmprintf(FILE * stream,const char * fmt,...)278 fmprintf(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 
289 int
mprintf(const char * fmt,...)290 mprintf(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  */
310 void
msetlocale(void)311 msetlocale(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