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    1 /*************************************************
    2 *      Perl-Compatible Regular Expressions       *
    3 *************************************************/
    4 
    5 /* PCRE is a library of functions to support regular expressions whose syntax
    6 and semantics are as close as possible to those of the Perl 5 language.
    7 
    8                        Written by Philip Hazel
    9            Copyright (c) 1997-2012 University of Cambridge
   10 
   11 -----------------------------------------------------------------------------
   12 Redistribution and use in source and binary forms, with or without
   13 modification, are permitted provided that the following conditions are met:
   14 
   15     * Redistributions of source code must retain the above copyright notice,
   16       this list of conditions and the following disclaimer.
   17 
   18     * Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in the
   20       documentation and/or other materials provided with the distribution.
   21 
   22     * Neither the name of the University of Cambridge nor the names of its
   23       contributors may be used to endorse or promote products derived from
   24       this software without specific prior written permission.
   25 
   26 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   27 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   28 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   29 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   30 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   31 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   32 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   33 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   34 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   35 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   36 POSSIBILITY OF SUCH DAMAGE.
   37 -----------------------------------------------------------------------------
   38 */
   39 
   40 
   41 /* This module contains an internal function for validating UTF-8 character
   42 strings. */
   43 
   44 
   45 #ifdef HAVE_CONFIG_H
   46 #include "config.h"
   47 #endif
   48 
   49 #include "pcre_internal.h"
   50 
   51 
   52 /*************************************************
   53 *         Validate a UTF-8 string                *
   54 *************************************************/
   55 
   56 /* This function is called (optionally) at the start of compile or match, to
   57 check that a supposed UTF-8 string is actually valid. The early check means
   58 that subsequent code can assume it is dealing with a valid string. The check
   59 can be turned off for maximum performance, but the consequences of supplying an
   60 invalid string are then undefined.
   61 
   62 Originally, this function checked according to RFC 2279, allowing for values in
   63 the range 0 to 0x7fffffff, up to 6 bytes long, but ensuring that they were in
   64 the canonical format. Once somebody had pointed out RFC 3629 to me (it
   65 obsoletes 2279), additional restrictions were applied. The values are now
   66 limited to be between 0 and 0x0010ffff, no more than 4 bytes long, and the
   67 subrange 0xd000 to 0xdfff is excluded. However, the format of 5-byte and 6-byte
   68 characters is still checked.
   69 
   70 From release 8.13 more information about the details of the error are passed
   71 back in the returned value:
   72 
   73 PCRE_UTF8_ERR0   No error
   74 PCRE_UTF8_ERR1   Missing 1 byte at the end of the string
   75 PCRE_UTF8_ERR2   Missing 2 bytes at the end of the string
   76 PCRE_UTF8_ERR3   Missing 3 bytes at the end of the string
   77 PCRE_UTF8_ERR4   Missing 4 bytes at the end of the string
   78 PCRE_UTF8_ERR5   Missing 5 bytes at the end of the string
   79 PCRE_UTF8_ERR6   2nd-byte's two top bits are not 0x80
   80 PCRE_UTF8_ERR7   3rd-byte's two top bits are not 0x80
   81 PCRE_UTF8_ERR8   4th-byte's two top bits are not 0x80
   82 PCRE_UTF8_ERR9   5th-byte's two top bits are not 0x80
   83 PCRE_UTF8_ERR10  6th-byte's two top bits are not 0x80
   84 PCRE_UTF8_ERR11  5-byte character is not permitted by RFC 3629
   85 PCRE_UTF8_ERR12  6-byte character is not permitted by RFC 3629
   86 PCRE_UTF8_ERR13  4-byte character with value > 0x10ffff is not permitted
   87 PCRE_UTF8_ERR14  3-byte character with value 0xd000-0xdfff is not permitted
   88 PCRE_UTF8_ERR15  Overlong 2-byte sequence
   89 PCRE_UTF8_ERR16  Overlong 3-byte sequence
   90 PCRE_UTF8_ERR17  Overlong 4-byte sequence
   91 PCRE_UTF8_ERR18  Overlong 5-byte sequence (won't ever occur)
   92 PCRE_UTF8_ERR19  Overlong 6-byte sequence (won't ever occur)
   93 PCRE_UTF8_ERR20  Isolated 0x80 byte (not within UTF-8 character)
   94 PCRE_UTF8_ERR21  Byte with the illegal value 0xfe or 0xff
   95 
   96 Arguments:
   97   string       points to the string
   98   length       length of string, or -1 if the string is zero-terminated
   99   errp         pointer to an error position offset variable
  100 
  101 Returns:       = 0    if the string is a valid UTF-8 string
  102                > 0    otherwise, setting the offset of the bad character
  103 */
  104 
  105 int
  106 PRIV(valid_utf)(PCRE_PUCHAR string, int length, int *erroroffset)
  107 {
  108 #ifdef SUPPORT_UTF
  109 register PCRE_PUCHAR p;
  110 
  111 if (length < 0)
  112   {
  113   for (p = string; *p != 0; p++);
  114   length = (int)(p - string);
  115   }
  116 
  117 for (p = string; length-- > 0; p++)
  118   {
  119   register int ab, c, d;
  120 
  121   c = *p;
  122   if (c < 128) continue;                /* ASCII character */
  123 
  124   if (c < 0xc0)                         /* Isolated 10xx xxxx byte */
  125     {
  126     *erroroffset = (int)(p - string);
  127     return PCRE_UTF8_ERR20;
  128     }
  129 
  130   if (c >= 0xfe)                        /* Invalid 0xfe or 0xff bytes */
  131     {
  132     *erroroffset = (int)(p - string);
  133     return PCRE_UTF8_ERR21;
  134     }
  135 
  136   ab = PRIV(utf8_table4)[c & 0x3f];     /* Number of additional bytes */
  137   if (length < ab)
  138     {
  139     *erroroffset = (int)(p - string);          /* Missing bytes */
  140     return ab - length;                 /* Codes ERR1 to ERR5 */
  141     }
  142   length -= ab;                         /* Length remaining */
  143 
  144   /* Check top bits in the second byte */
  145 
  146   if (((d = *(++p)) & 0xc0) != 0x80)
  147     {
  148     *erroroffset = (int)(p - string) - 1;
  149     return PCRE_UTF8_ERR6;
  150     }
  151 
  152   /* For each length, check that the remaining bytes start with the 0x80 bit
  153   set and not the 0x40 bit. Then check for an overlong sequence, and for the
  154   excluded range 0xd800 to 0xdfff. */
  155 
  156   switch (ab)
  157     {
  158     /* 2-byte character. No further bytes to check for 0x80. Check first byte
  159     for for xx00 000x (overlong sequence). */
  160 
  161     case 1: if ((c & 0x3e) == 0)
  162       {
  163       *erroroffset = (int)(p - string) - 1;
  164       return PCRE_UTF8_ERR15;
  165       }
  166     break;
  167 
  168     /* 3-byte character. Check third byte for 0x80. Then check first 2 bytes
  169       for 1110 0000, xx0x xxxx (overlong sequence) or
  170           1110 1101, 1010 xxxx (0xd800 - 0xdfff) */
  171 
  172     case 2:
  173     if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
  174       {
  175       *erroroffset = (int)(p - string) - 2;
  176       return PCRE_UTF8_ERR7;
  177       }
  178     if (c == 0xe0 && (d & 0x20) == 0)
  179       {
  180       *erroroffset = (int)(p - string) - 2;
  181       return PCRE_UTF8_ERR16;
  182       }
  183     if (c == 0xed && d >= 0xa0)
  184       {
  185       *erroroffset = (int)(p - string) - 2;
  186       return PCRE_UTF8_ERR14;
  187       }
  188     break;
  189 
  190     /* 4-byte character. Check 3rd and 4th bytes for 0x80. Then check first 2
  191        bytes for for 1111 0000, xx00 xxxx (overlong sequence), then check for a
  192        character greater than 0x0010ffff (f4 8f bf bf) */
  193 
  194     case 3:
  195     if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
  196       {
  197       *erroroffset = (int)(p - string) - 2;
  198       return PCRE_UTF8_ERR7;
  199       }
  200     if ((*(++p) & 0xc0) != 0x80)     /* Fourth byte */
  201       {
  202       *erroroffset = (int)(p - string) - 3;
  203       return PCRE_UTF8_ERR8;
  204       }
  205     if (c == 0xf0 && (d & 0x30) == 0)
  206       {
  207       *erroroffset = (int)(p - string) - 3;
  208       return PCRE_UTF8_ERR17;
  209       }
  210     if (c > 0xf4 || (c == 0xf4 && d > 0x8f))
  211       {
  212       *erroroffset = (int)(p - string) - 3;
  213       return PCRE_UTF8_ERR13;
  214       }
  215     break;
  216 
  217     /* 5-byte and 6-byte characters are not allowed by RFC 3629, and will be
  218     rejected by the length test below. However, we do the appropriate tests
  219     here so that overlong sequences get diagnosed, and also in case there is
  220     ever an option for handling these larger code points. */
  221 
  222     /* 5-byte character. Check 3rd, 4th, and 5th bytes for 0x80. Then check for
  223     1111 1000, xx00 0xxx */
  224 
  225     case 4:
  226     if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
  227       {
  228       *erroroffset = (int)(p - string) - 2;
  229       return PCRE_UTF8_ERR7;
  230       }
  231     if ((*(++p) & 0xc0) != 0x80)     /* Fourth byte */
  232       {
  233       *erroroffset = (int)(p - string) - 3;
  234       return PCRE_UTF8_ERR8;
  235       }
  236     if ((*(++p) & 0xc0) != 0x80)     /* Fifth byte */
  237       {
  238       *erroroffset = (int)(p - string) - 4;
  239       return PCRE_UTF8_ERR9;
  240       }
  241     if (c == 0xf8 && (d & 0x38) == 0)
  242       {
  243       *erroroffset = (int)(p - string) - 4;
  244       return PCRE_UTF8_ERR18;
  245       }
  246     break;
  247 
  248     /* 6-byte character. Check 3rd-6th bytes for 0x80. Then check for
  249     1111 1100, xx00 00xx. */
  250 
  251     case 5:
  252     if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
  253       {
  254       *erroroffset = (int)(p - string) - 2;
  255       return PCRE_UTF8_ERR7;
  256       }
  257     if ((*(++p) & 0xc0) != 0x80)     /* Fourth byte */
  258       {
  259       *erroroffset = (int)(p - string) - 3;
  260       return PCRE_UTF8_ERR8;
  261       }
  262     if ((*(++p) & 0xc0) != 0x80)     /* Fifth byte */
  263       {
  264       *erroroffset = (int)(p - string) - 4;
  265       return PCRE_UTF8_ERR9;
  266       }
  267     if ((*(++p) & 0xc0) != 0x80)     /* Sixth byte */
  268       {
  269       *erroroffset = (int)(p - string) - 5;
  270       return PCRE_UTF8_ERR10;
  271       }
  272     if (c == 0xfc && (d & 0x3c) == 0)
  273       {
  274       *erroroffset = (int)(p - string) - 5;
  275       return PCRE_UTF8_ERR19;
  276       }
  277     break;
  278     }
  279 
  280   /* Character is valid under RFC 2279, but 4-byte and 5-byte characters are
  281   excluded by RFC 3629. The pointer p is currently at the last byte of the
  282   character. */
  283 
  284   if (ab > 3)
  285     {
  286     *erroroffset = (int)(p - string) - ab;
  287     return (ab == 4)? PCRE_UTF8_ERR11 : PCRE_UTF8_ERR12;
  288     }
  289   }
  290 
  291 #else  /* SUPPORT_UTF */
  292 (void)(string);  /* Keep picky compilers happy */
  293 (void)(length);
  294 #endif
  295 
  296 return PCRE_UTF8_ERR0;   /* This indicates success */
  297 }
  298 
  299 /* End of pcre_valid_utf8.c */