xref: /openssh-portable/utf8.c (revision 31909696)
1 /* $OpenBSD: utf8.c,v 1.11 2020/05/01 06:28:52 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 
47 
48 /*
49  * For US-ASCII and UTF-8 encodings, we can safely recover from
50  * encoding errors and from non-printable characters.  For any
51  * other encodings, err to the side of caution and abort parsing:
52  * For state-dependent encodings, recovery is impossible.
53  * For arbitrary encodings, replacement of non-printable
54  * characters would be non-trivial and too fragile.
55  * The comments indicate what nl_langinfo(CODESET)
56  * returns for US-ASCII on various operating systems.
57  */
58 
59 static int
dangerous_locale(void)60 dangerous_locale(void) {
61 	char	*loc;
62 
63 	loc = nl_langinfo(CODESET);
64 	return strcmp(loc, "UTF-8") != 0 &&
65 	    strcmp(loc, "US-ASCII") != 0 &&		/* OpenBSD */
66 	    strcmp(loc, "ANSI_X3.4-1968") != 0 &&	/* Linux */
67 	    strcmp(loc, "ISO8859-1") != 0 &&		/* AIX */
68 	    strcmp(loc, "646") != 0 &&			/* Solaris, NetBSD */
69 	    strcmp(loc, "") != 0;			/* Solaris 6 */
70 }
71 
72 static int
grow_dst(char ** dst,size_t * sz,size_t maxsz,char ** dp,size_t need)73 grow_dst(char **dst, size_t *sz, size_t maxsz, char **dp, size_t need)
74 {
75 	char	*tp;
76 	size_t	 tsz;
77 
78 	if (*dp + need < *dst + *sz)
79 		return 0;
80 	tsz = *sz + 128;
81 	if (tsz > maxsz)
82 		tsz = maxsz;
83 	if ((tp = recallocarray(*dst, *sz, tsz, 1)) == NULL)
84 		return -1;
85 	*dp = tp + (*dp - *dst);
86 	*dst = tp;
87 	*sz = tsz;
88 	return 0;
89 }
90 
91 /*
92  * The following two functions limit the number of bytes written,
93  * including the terminating '\0', to sz.  Unless wp is NULL,
94  * they limit the number of display columns occupied to *wp.
95  * Whichever is reached first terminates the output string.
96  * To stay close to the standard interfaces, they return the number of
97  * non-NUL bytes that would have been written if both were unlimited.
98  * If wp is NULL, newline, carriage return, and tab are allowed;
99  * otherwise, the actual number of columns occupied by what was
100  * written is returned in *wp.
101  */
102 
103 int
vasnmprintf(char ** str,size_t maxsz,int * wp,const char * fmt,va_list ap)104 vasnmprintf(char **str, size_t maxsz, int *wp, const char *fmt, va_list ap)
105 {
106 	char	*src;	/* Source string returned from vasprintf. */
107 	char	*sp;	/* Pointer into src. */
108 	char	*dst;	/* Destination string to be returned. */
109 	char	*dp;	/* Pointer into dst. */
110 	char	*tp;	/* Temporary pointer for dst. */
111 	size_t	 sz;	/* Number of bytes allocated for dst. */
112 	wchar_t	 wc;	/* Wide character at sp. */
113 	int	 len;	/* Number of bytes in the character at sp. */
114 	int	 ret;	/* Number of bytes needed to format src. */
115 	int	 width;	/* Display width of the character wc. */
116 	int	 total_width, max_width, print;
117 
118 	src = NULL;
119 	if ((ret = vasprintf(&src, fmt, ap)) <= 0)
120 		goto fail;
121 
122 	sz = strlen(src) + 1;
123 	if ((dst = malloc(sz)) == NULL) {
124 		free(src);
125 		ret = -1;
126 		goto fail;
127 	}
128 
129 	if (maxsz > INT_MAX)
130 		maxsz = INT_MAX;
131 
132 	sp = src;
133 	dp = dst;
134 	ret = 0;
135 	print = 1;
136 	total_width = 0;
137 	max_width = wp == NULL ? INT_MAX : *wp;
138 	while (*sp != '\0') {
139 		if ((len = mbtowc(&wc, sp, MB_CUR_MAX)) == -1) {
140 			(void)mbtowc(NULL, NULL, MB_CUR_MAX);
141 			if (dangerous_locale()) {
142 				ret = -1;
143 				break;
144 			}
145 			len = 1;
146 			width = -1;
147 		} else if (wp == NULL &&
148 		    (wc == L'\n' || wc == L'\r' || wc == L'\t')) {
149 			/*
150 			 * Don't use width uninitialized; the actual
151 			 * value doesn't matter because total_width
152 			 * is only returned for wp != NULL.
153 			 */
154 			width = 0;
155 		} else if ((width = wcwidth(wc)) == -1 &&
156 		    dangerous_locale()) {
157 			ret = -1;
158 			break;
159 		}
160 
161 		/* Valid, printable character. */
162 
163 		if (width >= 0) {
164 			if (print && (dp - dst >= (int)maxsz - len ||
165 			    total_width > max_width - width))
166 				print = 0;
167 			if (print) {
168 				if (grow_dst(&dst, &sz, maxsz,
169 				    &dp, len) == -1) {
170 					ret = -1;
171 					break;
172 				}
173 				total_width += width;
174 				memcpy(dp, sp, len);
175 				dp += len;
176 			}
177 			sp += len;
178 			if (ret >= 0)
179 				ret += len;
180 			continue;
181 		}
182 
183 		/* Escaping required. */
184 
185 		while (len > 0) {
186 			if (print && (dp - dst >= (int)maxsz - 4 ||
187 			    total_width > max_width - 4))
188 				print = 0;
189 			if (print) {
190 				if (grow_dst(&dst, &sz, maxsz,
191 				    &dp, 4) == -1) {
192 					ret = -1;
193 					break;
194 				}
195 				tp = vis(dp, *sp, VIS_OCTAL | VIS_ALL, 0);
196 				width = tp - dp;
197 				total_width += width;
198 				dp = tp;
199 			} else
200 				width = 4;
201 			len--;
202 			sp++;
203 			if (ret >= 0)
204 				ret += width;
205 		}
206 		if (len > 0)
207 			break;
208 	}
209 	free(src);
210 	*dp = '\0';
211 	*str = dst;
212 	if (wp != NULL)
213 		*wp = total_width;
214 
215 	/*
216 	 * If the string was truncated by the width limit but
217 	 * would have fit into the size limit, the only sane way
218 	 * to report the problem is using the return value, such
219 	 * that the usual idiom "if (ret < 0 || ret >= sz) error"
220 	 * works as expected.
221 	 */
222 
223 	if (ret < (int)maxsz && !print)
224 		ret = -1;
225 	return ret;
226 
227 fail:
228 	if (wp != NULL)
229 		*wp = 0;
230 	if (ret == 0) {
231 		*str = src;
232 		return 0;
233 	} else {
234 		*str = NULL;
235 		return -1;
236 	}
237 }
238 
239 int
snmprintf(char * str,size_t sz,int * wp,const char * fmt,...)240 snmprintf(char *str, size_t sz, int *wp, const char *fmt, ...)
241 {
242 	va_list	 ap;
243 	char	*cp = NULL;
244 	int	 ret;
245 
246 	va_start(ap, fmt);
247 	ret = vasnmprintf(&cp, sz, wp, fmt, ap);
248 	va_end(ap);
249 	if (cp != NULL) {
250 		(void)strlcpy(str, cp, sz);
251 		free(cp);
252 	} else
253 		*str = '\0';
254 	return ret;
255 }
256 
257 int
asmprintf(char ** outp,size_t sz,int * wp,const char * fmt,...)258 asmprintf(char **outp, size_t sz, int *wp, const char *fmt, ...)
259 {
260 	va_list	 ap;
261 	int	 ret;
262 
263 	*outp = NULL;
264 	va_start(ap, fmt);
265 	ret = vasnmprintf(outp, sz, wp, fmt, ap);
266 	va_end(ap);
267 
268 	return ret;
269 }
270 
271 /*
272  * To stay close to the standard interfaces, the following functions
273  * return the number of non-NUL bytes written.
274  */
275 
276 int
vfmprintf(FILE * stream,const char * fmt,va_list ap)277 vfmprintf(FILE *stream, const char *fmt, va_list ap)
278 {
279 	char	*str = NULL;
280 	int	 ret;
281 
282 	if ((ret = vasnmprintf(&str, INT_MAX, NULL, fmt, ap)) < 0) {
283 		free(str);
284 		return -1;
285 	}
286 	if (fputs(str, stream) == EOF)
287 		ret = -1;
288 	free(str);
289 	return ret;
290 }
291 
292 int
fmprintf(FILE * stream,const char * fmt,...)293 fmprintf(FILE *stream, const char *fmt, ...)
294 {
295 	va_list	 ap;
296 	int	 ret;
297 
298 	va_start(ap, fmt);
299 	ret = vfmprintf(stream, fmt, ap);
300 	va_end(ap);
301 	return ret;
302 }
303 
304 int
mprintf(const char * fmt,...)305 mprintf(const char *fmt, ...)
306 {
307 	va_list	 ap;
308 	int	 ret;
309 
310 	va_start(ap, fmt);
311 	ret = vfmprintf(stdout, fmt, ap);
312 	va_end(ap);
313 	return ret;
314 }
315 
316 /*
317  * Set up libc for multibyte output in the user's chosen locale.
318  *
319  * XXX: we are known to have problems with Turkish (i/I confusion) so we
320  *      deliberately fall back to the C locale for now. Longer term we should
321  *      always prefer to select C.[encoding] if possible, but there's no
322  *      standardisation in locales between systems, so we'll need to survey
323  *      what's out there first.
324  */
325 void
msetlocale(void)326 msetlocale(void)
327 {
328 	const char *vars[] = { "LC_ALL", "LC_CTYPE", "LANG", NULL };
329 	char *cp;
330 	int i;
331 
332 	/*
333 	 * We can't yet cope with dotless/dotted I in Turkish locales,
334 	 * so fall back to the C locale for these.
335 	 */
336 	for (i = 0; vars[i] != NULL; i++) {
337 		if ((cp = getenv(vars[i])) == NULL)
338 			continue;
339 		if (strncasecmp(cp, "TR", 2) != 0)
340 			break;
341 		/*
342 		 * If we're in a UTF-8 locale then prefer to use
343 		 * the C.UTF-8 locale (or equivalent) if it exists.
344 		 */
345 		if ((strcasestr(cp, "UTF-8") != NULL ||
346 		    strcasestr(cp, "UTF8") != NULL) &&
347 		    (setlocale(LC_CTYPE, "C.UTF-8") != NULL ||
348 		    setlocale(LC_CTYPE, "POSIX.UTF-8") != NULL))
349 			return;
350 		setlocale(LC_CTYPE, "C");
351 		return;
352 	}
353 	/* We can handle this locale */
354 	setlocale(LC_CTYPE, "");
355 }
356