crypto/openssh/utf8.c

   1 /* $OpenBSD: utf8.c,v 1.3 2016/05/30 12:57:21 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 <stdarg.h>
  31 #include <stdio.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H) && !defined(BROKEN_STRNVIS)
  35 # include <vis.h>
  36 #endif
  37 #ifdef HAVE_WCHAR_H
  38 # include <wchar.h>
  39 #endif
  40
  41 #include "utf8.h"
  42
  43 static int       dangerous_locale(void);
  44 static int       grow_dst(char **, size_t *, size_t, char **, size_t);
  45 static int       vasnmprintf(char **, size_t, int *, const char *, va_list);
  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  */
  56
  57 static int
  58 dangerous_locale(void) {
  59         char    *loc;
  60
  61         loc = nl_langinfo(CODESET);
  62         return strcmp(loc, "US-ASCII") && strcmp(loc, "UTF-8");
  63 }
  64
  65 static int
  66 grow_dst(char **dst, size_t *sz, size_t maxsz, char **dp, size_t need)
  67 {
  68         char    *tp;
  69         size_t   tsz;
  70
  71         if (*dp + need < *dst + *sz)
  72                 return 0;
  73         tsz = *sz + 128;
  74         if (tsz > maxsz)
  75                 tsz = maxsz;
  76         if ((tp = realloc(*dst, tsz)) == NULL)
  77                 return -1;
  78         *dp = tp + (*dp - *dst);
  79         *dst = tp;
  80         *sz = tsz;
  81         return 0;
  82 }
  83
  84 /*
  85  * The following two functions limit the number of bytes written,
  86  * including the terminating '\0', to sz.  Unless wp is NULL,
  87  * they limit the number of display columns occupied to *wp.
  88  * Whichever is reached first terminates the output string.
  89  * To stay close to the standard interfaces, they return the number of
  90  * non-NUL bytes that would have been written if both were unlimited.
  91  * If wp is NULL, newline, carriage return, and tab are allowed;
  92  * otherwise, the actual number of columns occupied by what was
  93  * written is returned in *wp.
  94  */
  95
  96 static int
  97 vasnmprintf(char **str, size_t maxsz, int *wp, const char *fmt, va_list ap)
  98 {
  99         char    *src;   /* Source string returned from vasprintf. */
 100         char    *sp;    /* Pointer into src. */
 101         char    *dst;   /* Destination string to be returned. */
 102         char    *dp;    /* Pointer into dst. */
 103         char    *tp;    /* Temporary pointer for dst. */
 104         size_t   sz;    /* Number of bytes allocated for dst. */
 105         wchar_t  wc;    /* Wide character at sp. */
 106         int      len;   /* Number of bytes in the character at sp. */
 107         int      ret;   /* Number of bytes needed to format src. */
 108         int      width; /* Display width of the character wc. */
 109         int      total_width, max_width, print;
 110
 111         src = NULL;
 112         if ((ret = vasprintf(&src, fmt, ap)) <= 0)
 113                 goto fail;
 114
 115         sz = strlen(src) + 1;
 116         if ((dst = malloc(sz)) == NULL) {
 117                 free(src);
 118                 goto fail;
 119         }
 120
 121         if (maxsz > INT_MAX)
 122                 maxsz = INT_MAX;
 123
 124         sp = src;
 125         dp = dst;
 126         ret = 0;
 127         print = 1;
 128         total_width = 0;
 129         max_width = wp == NULL ? INT_MAX : *wp;
 130         while (*sp != '\0') {
 131                 if ((len = mbtowc(&wc, sp, MB_CUR_MAX)) == -1) {
 132                         (void)mbtowc(NULL, NULL, MB_CUR_MAX);
 133                         if (dangerous_locale()) {
 134                                 ret = -1;
 135                                 break;
 136                         }
 137                         len = 1;
 138                         width = -1;
 139                 } else if (wp == NULL &&
 140                     (wc == L'\n' || wc == L'\r' || wc == L'\t')) {
 141                         /*
 142                          * Don't use width uninitialized; the actual
 143                          * value doesn't matter because total_width
 144                          * is only returned for wp != NULL.
 145                          */
 146                         width = 0;
 147                 } else if ((width = wcwidth(wc)) == -1 &&
 148                     dangerous_locale()) {
 149                         ret = -1;
 150                         break;
 151                 }
 152
 153                 /* Valid, printable character. */
 154
 155                 if (width >= 0) {
 156                         if (print && (dp - dst >= (int)maxsz - len ||
 157                             total_width > max_width - width))
 158                                 print = 0;
 159                         if (print) {
 160                                 if (grow_dst(&dst, &sz, maxsz,
 161                                     &dp, len) == -1) {
 162                                         ret = -1;
 163                                         break;
 164                                 }
 165                                 total_width += width;
 166                                 memcpy(dp, sp, len);
 167                                 dp += len;
 168                         }
 169                         sp += len;
 170                         if (ret >= 0)
 171                                 ret += len;
 172                         continue;
 173                 }
 174
 175                 /* Escaping required. */
 176
 177                 while (len > 0) {
 178                         if (print && (dp - dst >= (int)maxsz - 4 ||
 179                             total_width > max_width - 4))
 180                                 print = 0;
 181                         if (print) {
 182                                 if (grow_dst(&dst, &sz, maxsz,
 183                                     &dp, 4) == -1) {
 184                                         ret = -1;
 185                                         break;
 186                                 }
 187                                 tp = vis(dp, *sp, VIS_OCTAL | VIS_ALL, 0);
 188                                 width = tp - dp;
 189                                 total_width += width;
 190                                 dp = tp;
 191                         } else
 192                                 width = 4;
 193                         len--;
 194                         sp++;
 195                         if (ret >= 0)
 196                                 ret += width;
 197                 }
 198                 if (len > 0)
 199                         break;
 200         }
 201         free(src);
 202         *dp = '\0';
 203         *str = dst;
 204         if (wp != NULL)
 205                 *wp = total_width;
 206
 207         /*
 208          * If the string was truncated by the width limit but
 209          * would have fit into the size limit, the only sane way
 210          * to report the problem is using the return value, such
 211          * that the usual idiom "if (ret < 0 || ret >= sz) error"
 212          * works as expected.
 213          */
 214
 215         if (ret < (int)maxsz && !print)
 216                 ret = -1;
 217         return ret;
 218
 219 fail:
 220         if (wp != NULL)
 221                 *wp = 0;
 222         if (ret == 0) {
 223                 *str = src;
 224                 return 0;
 225         } else {
 226                 *str = NULL;
 227                 return -1;
 228         }
 229 }
 230
 231 int
 232 snmprintf(char *str, size_t sz, int *wp, const char *fmt, ...)
 233 {
 234         va_list  ap;
 235         char    *cp;
 236         int      ret;
 237
 238         va_start(ap, fmt);
 239         ret = vasnmprintf(&cp, sz, wp, fmt, ap);
 240         va_end(ap);
 241         if (cp != NULL) {
 242                 (void)strlcpy(str, cp, sz);
 243                 free(cp);
 244         } else
 245                 *str = '\0';
 246         return ret;
 247 }
 248
 249 /*
 250  * To stay close to the standard interfaces, the following functions
 251  * return the number of non-NUL bytes written.
 252  */
 253
 254 int
 255 vfmprintf(FILE *stream, const char *fmt, va_list ap)
 256 {
 257         char    *str;
 258         int      ret;
 259
 260         if ((ret = vasnmprintf(&str, INT_MAX, NULL, fmt, ap)) < 0)
 261                 return -1;
 262         if (fputs(str, stream) == EOF)
 263                 ret = -1;
 264         free(str);
 265         return ret;
 266 }
 267
 268 int
 269 fmprintf(FILE *stream, const char *fmt, ...)
 270 {
 271         va_list  ap;
 272         int      ret;
 273
 274         va_start(ap, fmt);
 275         ret = vfmprintf(stream, fmt, ap);
 276         va_end(ap);
 277         return ret;
 278 }
 279
 280 int
 281 mprintf(const char *fmt, ...)
 282 {
 283         va_list  ap;
 284         int      ret;
 285
 286         va_start(ap, fmt);
 287         ret = vfmprintf(stdout, fmt, ap);
 288         va_end(ap);
 289         return ret;
 290 }