crypto/openssh/utf8.c

   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
  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
  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
 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
 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
 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
 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
 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
 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
 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 }