src/pcre2_valid_utf.c

/*************************************************
*      Perl-Compatible Regular Expressions       *
*************************************************/

/* PCRE is a library of functions to support regular expressions whose syntax
and semantics are as close as possible to those of the Perl 5 language.

                       Written by Philip Hazel
     Original API code Copyright (c) 1997-2012 University of Cambridge
          New API code Copyright (c) 2016-2020 University of Cambridge

-----------------------------------------------------------------------------
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    * Redistributions of source code must retain the above copyright notice,
      this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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*/


/* This module contains an internal function for validating UTF character
strings. This file is also #included by the pcre2test program, which uses
macros to change names from _pcre2_xxx to xxxx, thereby avoiding name clashes
with the library. In this case, PCRE2_PCRE2TEST is defined. */

#ifndef PCRE2_PCRE2TEST           /* We're compiling the library */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "pcre2_internal.h"
#endif /* PCRE2_PCRE2TEST */


#ifndef SUPPORT_UNICODE
/*************************************************
*  Dummy function when Unicode is not supported  *
*************************************************/

/* This function should never be called when Unicode is not supported. */

int
PRIV(valid_utf)(PCRE2_SPTR string, PCRE2_SIZE length, PCRE2_SIZE *erroroffset)
{
(void)string;
(void)length;
(void)erroroffset;
return 0;
}
#else  /* UTF is supported */



/*************************************************
*           Validate a UTF string                *
*************************************************/

/* This function is called (optionally) at the start of compile or match, to
check that a supposed UTF string is actually valid. The early check means
that subsequent code can assume it is dealing with a valid string. The check
can be turned off for maximum performance, but the consequences of supplying an
invalid string are then undefined.

Arguments:
  string       points to the string
  length       length of string
  errp         pointer to an error position offset variable

Returns:       == 0    if the string is a valid UTF string
               != 0    otherwise, setting the offset of the bad character
*/

int
PRIV(valid_utf)(PCRE2_SPTR string, PCRE2_SIZE length, PCRE2_SIZE *erroroffset)
{
PCRE2_SPTR p;
uint32_t c;

/* ----------------- Check a UTF-8 string ----------------- */

#if PCRE2_CODE_UNIT_WIDTH == 8

/* Originally, this function checked according to RFC 2279, allowing for values
in the range 0 to 0x7fffffff, up to 6 bytes long, but ensuring that they were
in the canonical format. Once somebody had pointed out RFC 3629 to me (it
obsoletes 2279), additional restrictions were applied. The values are now
limited to be between 0 and 0x0010ffff, no more than 4 bytes long, and the
subrange 0xd000 to 0xdfff is excluded. However, the format of 5-byte and 6-byte
characters is still checked. Error returns are as follows:

PCRE2_ERROR_UTF8_ERR1   Missing 1 byte at the end of the string
PCRE2_ERROR_UTF8_ERR2   Missing 2 bytes at the end of the string
PCRE2_ERROR_UTF8_ERR3   Missing 3 bytes at the end of the string
PCRE2_ERROR_UTF8_ERR4   Missing 4 bytes at the end of the string
PCRE2_ERROR_UTF8_ERR5   Missing 5 bytes at the end of the string
PCRE2_ERROR_UTF8_ERR6   2nd-byte's two top bits are not 0x80
PCRE2_ERROR_UTF8_ERR7   3rd-byte's two top bits are not 0x80
PCRE2_ERROR_UTF8_ERR8   4th-byte's two top bits are not 0x80
PCRE2_ERROR_UTF8_ERR9   5th-byte's two top bits are not 0x80
PCRE2_ERROR_UTF8_ERR10  6th-byte's two top bits are not 0x80
PCRE2_ERROR_UTF8_ERR11  5-byte character is not permitted by RFC 3629
PCRE2_ERROR_UTF8_ERR12  6-byte character is not permitted by RFC 3629
PCRE2_ERROR_UTF8_ERR13  4-byte character with value > 0x10ffff is not permitted
PCRE2_ERROR_UTF8_ERR14  3-byte character with value 0xd800-0xdfff is not permitted
PCRE2_ERROR_UTF8_ERR15  Overlong 2-byte sequence
PCRE2_ERROR_UTF8_ERR16  Overlong 3-byte sequence
PCRE2_ERROR_UTF8_ERR17  Overlong 4-byte sequence
PCRE2_ERROR_UTF8_ERR18  Overlong 5-byte sequence (won't ever occur)
PCRE2_ERROR_UTF8_ERR19  Overlong 6-byte sequence (won't ever occur)
PCRE2_ERROR_UTF8_ERR20  Isolated 0x80 byte (not within UTF-8 character)
PCRE2_ERROR_UTF8_ERR21  Byte with the illegal value 0xfe or 0xff
*/

for (p = string; length > 0; p++)
  {
  uint32_t ab, d;

  c = *p;
  length--;

  if (c < 128) continue;                /* ASCII character */

  if (c < 0xc0)                         /* Isolated 10xx xxxx byte */
    {
    *erroroffset = (PCRE2_SIZE)(p - string);
    return PCRE2_ERROR_UTF8_ERR20;
    }

  if (c >= 0xfe)                        /* Invalid 0xfe or 0xff bytes */
    {
    *erroroffset = (PCRE2_SIZE)(p - string);
    return PCRE2_ERROR_UTF8_ERR21;
    }

  ab = PRIV(utf8_table4)[c & 0x3f];     /* Number of additional bytes (1-5) */
  if (length < ab)                      /* Missing bytes */
    {
    *erroroffset = (PCRE2_SIZE)(p - string);
    switch(ab - length)
      {
      case 1: return PCRE2_ERROR_UTF8_ERR1;
      case 2: return PCRE2_ERROR_UTF8_ERR2;
      case 3: return PCRE2_ERROR_UTF8_ERR3;
      case 4: return PCRE2_ERROR_UTF8_ERR4;
      case 5: return PCRE2_ERROR_UTF8_ERR5;
      }
    }
  length -= ab;                         /* Length remaining */

  /* Check top bits in the second byte */

  if (((d = *(++p)) & 0xc0) != 0x80)
    {
    *erroroffset = (int)(p - string) - 1;
    return PCRE2_ERROR_UTF8_ERR6;
    }

  /* For each length, check that the remaining bytes start with the 0x80 bit
  set and not the 0x40 bit. Then check for an overlong sequence, and for the
  excluded range 0xd800 to 0xdfff. */

  switch (ab)
    {
    /* 2-byte character. No further bytes to check for 0x80. Check first byte
    for for xx00 000x (overlong sequence). */

    case 1: if ((c & 0x3e) == 0)
      {
      *erroroffset = (int)(p - string) - 1;
      return PCRE2_ERROR_UTF8_ERR15;
      }
    break;

    /* 3-byte character. Check third byte for 0x80. Then check first 2 bytes
      for 1110 0000, xx0x xxxx (overlong sequence) or
          1110 1101, 1010 xxxx (0xd800 - 0xdfff) */

    case 2:
    if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
      {
      *erroroffset = (int)(p - string) - 2;
      return PCRE2_ERROR_UTF8_ERR7;
      }
    if (c == 0xe0 && (d & 0x20) == 0)
      {
      *erroroffset = (int)(p - string) - 2;
      return PCRE2_ERROR_UTF8_ERR16;
      }
    if (c == 0xed && d >= 0xa0)
      {
      *erroroffset = (int)(p - string) - 2;
      return PCRE2_ERROR_UTF8_ERR14;
      }
    break;

    /* 4-byte character. Check 3rd and 4th bytes for 0x80. Then check first 2
       bytes for for 1111 0000, xx00 xxxx (overlong sequence), then check for a
       character greater than 0x0010ffff (f4 8f bf bf) */

    case 3:
    if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
      {
      *erroroffset = (int)(p - string) - 2;
      return PCRE2_ERROR_UTF8_ERR7;
      }
    if ((*(++p) & 0xc0) != 0x80)     /* Fourth byte */
      {
      *erroroffset = (int)(p - string) - 3;
      return PCRE2_ERROR_UTF8_ERR8;
      }
    if (c == 0xf0 && (d & 0x30) == 0)
      {
      *erroroffset = (int)(p - string) - 3;
      return PCRE2_ERROR_UTF8_ERR17;
      }
    if (c > 0xf4 || (c == 0xf4 && d > 0x8f))
      {
      *erroroffset = (int)(p - string) - 3;
      return PCRE2_ERROR_UTF8_ERR13;
      }
    break;

    /* 5-byte and 6-byte characters are not allowed by RFC 3629, and will be
    rejected by the length test below. However, we do the appropriate tests
    here so that overlong sequences get diagnosed, and also in case there is
    ever an option for handling these larger code points. */

    /* 5-byte character. Check 3rd, 4th, and 5th bytes for 0x80. Then check for
    1111 1000, xx00 0xxx */

    case 4:
    if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
      {
      *erroroffset = (int)(p - string) - 2;
      return PCRE2_ERROR_UTF8_ERR7;
      }
    if ((*(++p) & 0xc0) != 0x80)     /* Fourth byte */
      {
      *erroroffset = (int)(p - string) - 3;
      return PCRE2_ERROR_UTF8_ERR8;
      }
    if ((*(++p) & 0xc0) != 0x80)     /* Fifth byte */
      {
      *erroroffset = (int)(p - string) - 4;
      return PCRE2_ERROR_UTF8_ERR9;
      }
    if (c == 0xf8 && (d & 0x38) == 0)
      {
      *erroroffset = (int)(p - string) - 4;
      return PCRE2_ERROR_UTF8_ERR18;
      }
    break;

    /* 6-byte character. Check 3rd-6th bytes for 0x80. Then check for
    1111 1100, xx00 00xx. */

    case 5:
    if ((*(++p) & 0xc0) != 0x80)     /* Third byte */
      {
      *erroroffset = (int)(p - string) - 2;
      return PCRE2_ERROR_UTF8_ERR7;
      }
    if ((*(++p) & 0xc0) != 0x80)     /* Fourth byte */
      {
      *erroroffset = (int)(p - string) - 3;
      return PCRE2_ERROR_UTF8_ERR8;
      }
    if ((*(++p) & 0xc0) != 0x80)     /* Fifth byte */
      {
      *erroroffset = (int)(p - string) - 4;
      return PCRE2_ERROR_UTF8_ERR9;
      }
    if ((*(++p) & 0xc0) != 0x80)     /* Sixth byte */
      {
      *erroroffset = (int)(p - string) - 5;
      return PCRE2_ERROR_UTF8_ERR10;
      }
    if (c == 0xfc && (d & 0x3c) == 0)
      {
      *erroroffset = (int)(p - string) - 5;
      return PCRE2_ERROR_UTF8_ERR19;
      }
    break;
    }

  /* Character is valid under RFC 2279, but 4-byte and 5-byte characters are
  excluded by RFC 3629. The pointer p is currently at the last byte of the
  character. */

  if (ab > 3)
    {
    *erroroffset = (int)(p - string) - ab;
    return (ab == 4)? PCRE2_ERROR_UTF8_ERR11 : PCRE2_ERROR_UTF8_ERR12;
    }
  }
return 0;


/* ----------------- Check a UTF-16 string ----------------- */

#elif PCRE2_CODE_UNIT_WIDTH == 16

/* There's not so much work, nor so many errors, for UTF-16.
PCRE2_ERROR_UTF16_ERR1  Missing low surrogate at the end of the string
PCRE2_ERROR_UTF16_ERR2  Invalid low surrogate
PCRE2_ERROR_UTF16_ERR3  Isolated low surrogate
*/

for (p = string; length > 0; p++)
  {
  c = *p;
  length--;

  if ((c & 0xf800) != 0xd800)
    {
    /* Normal UTF-16 code point. Neither high nor low surrogate. */
    }
  else if ((c & 0x0400) == 0)
    {
    /* High surrogate. Must be a followed by a low surrogate. */
    if (length == 0)
      {
      *erroroffset = p - string;
      return PCRE2_ERROR_UTF16_ERR1;
      }
    p++;
    length--;
    if ((*p & 0xfc00) != 0xdc00)
      {
      *erroroffset = p - string - 1;
      return PCRE2_ERROR_UTF16_ERR2;
      }
    }
  else
    {
    /* Isolated low surrogate. Always an error. */
    *erroroffset = p - string;
    return PCRE2_ERROR_UTF16_ERR3;
    }
  }
return 0;



/* ----------------- Check a UTF-32 string ----------------- */

#else

/* There is very little to do for a UTF-32 string.
PCRE2_ERROR_UTF32_ERR1  Surrogate character
PCRE2_ERROR_UTF32_ERR2  Character > 0x10ffff
*/

for (p = string; length > 0; length--, p++)
  {
  c = *p;
  if ((c & 0xfffff800u) != 0xd800u)
    {
    /* Normal UTF-32 code point. Neither high nor low surrogate. */
    if (c > 0x10ffffu)
      {
      *erroroffset = p - string;
      return PCRE2_ERROR_UTF32_ERR2;
      }
    }
  else
    {
    /* A surrogate */
    *erroroffset = p - string;
    return PCRE2_ERROR_UTF32_ERR1;
    }
  }
return 0;
#endif  /* CODE_UNIT_WIDTH */
}
#endif  /* SUPPORT_UNICODE */

/* End of pcre2_valid_utf.c */