crypto/openssh/utf8.c

   1 /* $OpenBSD: utf8.c,v 1.7 2017/05/31 09:15:42 deraadt 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 = recallocarray(*dst, *sz, tsz, 1)) == 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 }