clamav/libclamav/yara_lexer.l

/*
 * YARA rule lexer for ClamAV
 *
 * Copyright (C) 2014-2023 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
 *
 * Authors: Steven Morgan
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License version 2 as published by the
 * Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
/* This file was originally derived from yara 3.1.0 libyara/lexer.l and is
   revised for running YARA rules in ClamAV. Following is the YARA copyright. */
/*
Copyright (c) 2007-2013. The YARA Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

/* Lexical analyzer for YARA */

%{

#include <math.h>
#include <stdio.h>
#ifdef REAL_YARA
#include <stdint.h>
#endif
#include <string.h>
#include <setjmp.h>

#ifdef REAL_YARA
#include <yara/lexer.h>
#include <yara/rules.h>
#include <yara/sizedstr.h>
#include <yara/error.h>
#include <yara/mem.h>
#include <yara/utils.h>

#include "grammar.h"
#else
#include "others.h"
#include "yara_clam.h"
#include "yara_grammar.h"
#include "yara_lexer.h"
#endif

#define LEX_CHECK_SPACE_OK(data, current_size, max_length) \
    if (strlen(data) + current_size >= max_length - 1) \
    { \
      yyerror(yyscanner, compiler, "out of space in lex_buf"); \
      yyterminate(); \
    }

#define YYTEXT_TO_BUFFER \
    { \
      char *yptr = yytext; \
      LEX_CHECK_SPACE_OK(yptr, yyextra->lex_buf_len, LEX_BUF_SIZE); \
      while(*yptr) \
      { \
        *yyextra->lex_buf_ptr++ = *yptr++; \
        yyextra->lex_buf_len++; \
      } \
    }

#ifdef _WIN32
#define snprintf _snprintf
#endif

%}

%option reentrant bison-bridge
%option noyywrap
%option nounistd
%option noinput
%option nounput
%option yylineno
/* %option prefix="yara_yy" */
%option outfile="yara_lexer.c"

%option verbose
%option warn

%x str
%x regexp
%x include
%x comment

digit         [0-9]
letter        [a-zA-Z]
hexdigit      [a-fA-F0-9]

%%

"<"                     { return _LT_;          }
">"                     { return _GT_;          }
"<="                    { return _LE_;          }
">="                    { return _GE_;          }
"=="                    { return _EQ_;          }
"!="                    { return _NEQ_;         }
"<<"                    { return _SHIFT_LEFT_;  }
">>"                    { return _SHIFT_RIGHT_; }
"private"               { return _PRIVATE_;     }
"global"                { return _GLOBAL_;      }
"rule"                  { return _RULE_;        }
"meta"                  { return _META_;        }
"strings"               { return _STRINGS_;     }
"ascii"                 { return _ASCII_;       }
"wide"                  { return _WIDE_;        }
"fullword"              { return _FULLWORD_;    }
"nocase"                { return _NOCASE_;      }
"condition"             { return _CONDITION_;   }
"true"                  { return _TRUE_;        }
"false"                 { return _FALSE_;       }
"not"                   { return _NOT_;         }
"and"                   { return _AND_;         }
"or"                    { return _OR_;          }
"at"                    { return _AT_;          }
"in"                    { return _IN_;          }
"of"                    { return _OF_;          }
"them"                  { return _THEM_;        }
"for"                   { return _FOR_;         }
"all"                   { return _ALL_;         }
"any"                   { return _ANY_;         }
"entrypoint"            { return _ENTRYPOINT_;  }
"filesize"              { return _FILESIZE_;    }
"uint8"                 { return _UINT8_;       }
"uint16"                { return _UINT16_;      }
"uint32"                { return _UINT32_;      }
"int8"                  { return _INT8_;        }
"int16"                 { return _INT16_;       }
"int32"                 { return _INT32_;       }
"matches"               { return _MATCHES_;     }
"contains"              { return _CONTAINS_;    }
"import"                { return _IMPORT_;      }


"/*"                    { BEGIN(comment);       }
<comment>"*/"           { BEGIN(INITIAL);       }
<comment>(.|\n)         { /* skip comments */   }


"//"[^\n]*              { /* skip single-line comments */ }


include[ \t]+\"         {
                          yyextra->lex_buf_ptr = yyextra->lex_buf;
                          yyextra->lex_buf_len = 0;
                          BEGIN(include);
                        }


<include>[^\"]+         { YYTEXT_TO_BUFFER; }


<include>\"             {

  char            buffer[1024];
  char            *current_file_name;
  char            *s = NULL;
  char            *b = NULL;
  char            *f;
  FILE*           fh;

  if (compiler->allow_includes)
  {
    *yyextra->lex_buf_ptr = '\0'; // null-terminate included file path

    // move path of current source file into buffer
    current_file_name = yr_compiler_get_current_file_name(compiler);

    if (current_file_name != NULL)
    {
      strlcpy(buffer, current_file_name, sizeof(buffer));
    }
    else
    {
      buffer[0] = '\0';
    }

    // make included file path relative to current source file
    s = strrchr(buffer, '/');

    #ifdef _WIN32
    b = strrchr(buffer, '\\'); // in Windows both path delimiters are accepted
    #endif

    if (s != NULL || b != NULL)
    {
      f = (b > s)? (b + 1): (s + 1);

      strlcpy(f, yyextra->lex_buf, sizeof(buffer) - (f - buffer));

      f = buffer;

      // SECURITY: Potential for directory traversal here.
      fh = fopen(buffer, "r");

      // if include file was not found relative to current source file,
      // try to open it with path as specified by user (maybe user wrote
      // a full path)

      if (fh == NULL)
      {
        f = yyextra->lex_buf;

        // SECURITY: Potential for directory traversal here.
        fh = fopen(yyextra->lex_buf, "r");
      }
    }
    else
    {
      f = yyextra->lex_buf;

      // SECURITY: Potential for directory traversal here.
      fh = fopen(yyextra->lex_buf, "r");
    }

    if (fh != NULL)
    {
      int error_code = _yr_compiler_push_file_name(compiler, f);

      if (error_code != ERROR_SUCCESS)
      {
        if (error_code == ERROR_INCLUDES_CIRCULAR_REFERENCE)
        {
          yyerror(yyscanner, compiler, "includes circular reference");
        }
        else if (error_code == ERROR_INCLUDE_DEPTH_EXCEEDED)
        {
          yyerror(yyscanner, compiler, "includes depth exceeded");
        }

        yyterminate();
      }

      _yr_compiler_push_file(compiler, fh);
      yypush_buffer_state(
          yy_create_buffer(fh, YY_BUF_SIZE, yyscanner), yyscanner);
    }
    else
    {
      snprintf(buffer, sizeof(buffer),
               "can't open include file: %s", yyextra->lex_buf);
      yyerror(yyscanner, compiler, buffer);
    }
  }
  else // not allowing includes
  {
    yyerror(yyscanner, compiler, "includes are disabled");
    yyterminate();
  }

  BEGIN(INITIAL);
}


<<EOF>> {

  YR_COMPILER* compiler = yyget_extra(yyscanner);
  FILE* file = _yr_compiler_pop_file(compiler);

  if (file != NULL)
  {
    fclose(file);
  }

  _yr_compiler_pop_file_name(compiler);
  yypop_buffer_state(yyscanner);

  if (!YY_CURRENT_BUFFER)
  {
    yyterminate();
  }
}


$({letter}|{digit}|_)*"*"  {

  yylval->c_string = yr_strdup(yytext);

  if (yylval->c_string == NULL)
  {
    yyerror(yyscanner, compiler, "not enough memory");
    yyterminate();
  }

  return _STRING_IDENTIFIER_WITH_WILDCARD_;
}


$({letter}|{digit}|_)*  {

  yylval->c_string = yr_strdup(yytext);

  if (yylval->c_string == NULL)
  {
    yyerror(yyscanner, compiler, "not enough memory");
    yyterminate();
  }

  return _STRING_IDENTIFIER_;
}


#({letter}|{digit}|_)*  {

  yylval->c_string = yr_strdup(yytext);

  if (yylval->c_string == NULL)
  {
    yyerror(yyscanner, compiler, "not enough memory");
    yyterminate();
  }

  yylval->c_string[0] = '$'; /* replace # by $*/
  return _STRING_COUNT_;
}


@({letter}|{digit}|_)*  {

  yylval->c_string = yr_strdup(yytext);

  if (yylval->c_string == NULL)
  {
    yyerror(yyscanner, compiler, "not enough memory");
    yyterminate();
  }

  yylval->c_string[0] = '$'; /* replace @ by $*/
  return _STRING_OFFSET_;
}


({letter}|_)({letter}|{digit}|_)*  {

  if (strlen(yytext) > 128)
  {
    yyerror(yyscanner, compiler, "indentifier too long");
  }

  yylval->c_string = yr_strdup(yytext);

  if (yylval->c_string == NULL)
  {
    yyerror(yyscanner, compiler, "not enough memory");
    yyterminate();
  }
  return _IDENTIFIER_;
}


{digit}+(MB|KB){0,1}  {

  yylval->integer = (size_t) atol(yytext);

  if (strstr(yytext, "KB") != NULL)
  {
     yylval->integer *= 1024;
  }
  else if (strstr(yytext, "MB") != NULL)
  {
     yylval->integer *= 1048576;
  }
  return _NUMBER_;
}


0x{hexdigit}+  {

  yylval->integer = xtoi(yytext + 2);
  return _NUMBER_;
}


<str>\"   {     /* saw closing quote - all done */

  SIZED_STRING* s;

  if (yyextra->lex_buf_len == 0)
  {
    yyerror(yyscanner, compiler, "empty string");
  }

  *yyextra->lex_buf_ptr = '\0';

  BEGIN(INITIAL);

  s = (SIZED_STRING*) yr_malloc(yyextra->lex_buf_len + sizeof(SIZED_STRING));
  s->length = yyextra->lex_buf_len;
  s->flags = 0;

  memcpy(s->c_string, yyextra->lex_buf, yyextra->lex_buf_len + 1);
  yylval->sized_string = s;

  return _TEXT_STRING_;
}


<str>\\t   {

  LEX_CHECK_SPACE_OK("\t", yyextra->lex_buf_len, LEX_BUF_SIZE);
  *yyextra->lex_buf_ptr++ = '\t';
  yyextra->lex_buf_len++;
}


<str>\\n   {

  LEX_CHECK_SPACE_OK("\n", yyextra->lex_buf_len, LEX_BUF_SIZE);
  *yyextra->lex_buf_ptr++ = '\n';
  yyextra->lex_buf_len++;
}


<str>\\\"   {

  LEX_CHECK_SPACE_OK("\"", yyextra->lex_buf_len, LEX_BUF_SIZE);
  *yyextra->lex_buf_ptr++ = '\"';
  yyextra->lex_buf_len++;
}


<str>\\\\   {

  LEX_CHECK_SPACE_OK("\\", yyextra->lex_buf_len, LEX_BUF_SIZE);
  *yyextra->lex_buf_ptr++ = '\\';
  yyextra->lex_buf_len++;
}


<str>\\x{hexdigit}{2} {

   int result;

   sscanf( yytext + 2, "%x", &result );
   LEX_CHECK_SPACE_OK("X", yyextra->lex_buf_len, LEX_BUF_SIZE);
   *yyextra->lex_buf_ptr++ = result;
   yyextra->lex_buf_len++;
}


<str>[^\\\n\"]+   { YYTEXT_TO_BUFFER; }


<str>\n  {

  yyerror(yyscanner, compiler, "unterminated string");
  yyterminate();
}

<str>\\(.|\n) {

  yyerror(yyscanner, compiler, "illegal escape sequence");
}


<regexp>\/i?s?  {

  SIZED_STRING* s;

  if (yyextra->lex_buf_len == 0)
  {
    yyerror(yyscanner, compiler, "empty regular expression");
  }

  *yyextra->lex_buf_ptr = '\0';

  BEGIN(INITIAL);

  s = (SIZED_STRING*) yr_malloc(yyextra->lex_buf_len + sizeof(SIZED_STRING));
  s->flags = 0;

  if (yytext[1] == 'i')
    s->flags |= SIZED_STRING_FLAGS_NO_CASE;

  if (yytext[1] == 's' || yytext[2] == 's')
    s->flags |= SIZED_STRING_FLAGS_DOT_ALL;

  s->length = yyextra->lex_buf_len;
  strlcpy(s->c_string, yyextra->lex_buf, s->length + 1);

  yylval->sized_string = s;

  return _REGEXP_;
}


<regexp>\\\/  {

  LEX_CHECK_SPACE_OK("/", yyextra->lex_buf_len, LEX_BUF_SIZE);
  *yyextra->lex_buf_ptr++ = '/';
  yyextra->lex_buf_len++ ;
}


<regexp>\\. {

  LEX_CHECK_SPACE_OK("\\.", yyextra->lex_buf_len, LEX_BUF_SIZE);
  *yyextra->lex_buf_ptr++ = yytext[0];
  *yyextra->lex_buf_ptr++ = yytext[1];
  yyextra->lex_buf_len += 2;
}


<regexp>[^/\n\\]+ { YYTEXT_TO_BUFFER; }


<regexp>\n  {

  yyerror(yyscanner, compiler, "unterminated regular expression");
  yyterminate();
}


\"  {

  yyextra->lex_buf_ptr = yyextra->lex_buf;
  yyextra->lex_buf_len = 0;
  BEGIN(str);
}


"/"  {

  yyextra->lex_buf_ptr = yyextra->lex_buf;
  yyextra->lex_buf_len = 0;
  BEGIN(regexp);
}


\{({hexdigit}|[ \-|\?\[\]\(\)\n\t])+\}  {

  int len = strlen(yytext);
  SIZED_STRING* s = (SIZED_STRING*) yr_malloc(len + sizeof(SIZED_STRING));

  s->length = len;
  s->flags = 0;

  strlcpy(s->c_string, yytext, s->length + 1);
  yylval->sized_string = s;

  return _HEX_STRING_;
}


[ \t\r\n]   /* skip whitespace */

.   {

  if (yytext[0] >= 32 && yytext[0] < 127)
  {
    return yytext[0];
  }
  else
  {
    yyerror(yyscanner, compiler, "non-ascii character");
    yyterminate();
  }
}

%%


void yywarning(
    yyscan_t yyscanner,
    const char *warning_message)
{
  YR_COMPILER* compiler = yyget_extra(yyscanner);
  char* file_name;

  if (compiler->file_name_stack_ptr > 0)
    file_name = compiler->file_name_stack[compiler->file_name_stack_ptr - 1];
  else
    file_name = NULL;

#ifdef REAL_YARA
  compiler->callback(
      YARA_ERROR_LEVEL_WARNING,
      file_name,
      yyget_lineno(yyscanner),
      warning_message);
#else
    cli_warnmsg("yywarning(): %s line %d %s\n", file_name?file_name:"(file name missing)", compiler->last_error_line, warning_message);
#endif
}


void yyfatal(
    yyscan_t yyscanner,
    const char *error_message)
{
  YR_COMPILER* compiler = yyget_extra(yyscanner);
  int last_result = compiler->last_result;

  yyerror(yyscanner, compiler, error_message);
  compiler->last_result = last_result;
  longjmp(compiler->error_recovery, 1);
}


void yyerror(
    yyscan_t yyscanner,
    YR_COMPILER* compiler,
    const char *error_message)
{
  char message[512] = {'\0'};
  char* file_name = NULL;

  /*
    if error_message != NULL the error comes from yyparse internal code
    else the error comes from my code and the error code is set in
    compiler->last_result
  */

  compiler->errors++;

  if (compiler->error_line != 0)
    compiler->last_error_line = compiler->error_line;
  else
    compiler->last_error_line = yyget_lineno(yyscanner);

  compiler->error_line = 0;

  if (compiler->file_name_stack_ptr > 0)
  {
    file_name = compiler->file_name_stack[compiler->file_name_stack_ptr - 1];
  }
  else
  {
    file_name = NULL;
  }

  if (error_message != NULL)
  {
    yr_compiler_set_error_extra_info(compiler, error_message);
    compiler->last_error = ERROR_SYNTAX_ERROR;

#ifdef REAL_YARA
    if (compiler->callback != NULL)
    {
      compiler->callback(
          YARA_ERROR_LEVEL_ERROR,
          file_name,
          compiler->last_error_line,
          error_message);
    }
#else
    cli_errmsg("yyerror(): %s line %d %s\n", file_name?file_name:"(file name missing)", compiler->last_error_line, error_message);
#endif
  }
  else
  {
    compiler->last_error = compiler->last_result;

#ifdef REAL_YARA
    if (compiler->callback != NULL)
    {
      yr_compiler_get_error_message(compiler, message, sizeof(message));

      compiler->callback(
        YARA_ERROR_LEVEL_ERROR,
        file_name,
        compiler->last_error_line,
        message);
    }
#else
    yr_compiler_get_error_message(compiler, message, sizeof(message));
    cli_errmsg("yyerror(): %s line %d %s\n", file_name?file_name:"NULL filename", compiler->last_error_line, message);
#endif
  }

  compiler->last_result = ERROR_SUCCESS;
}


int yr_lex_parse_rules_string(
  const char* rules_string,
  YR_COMPILER* compiler)
{
#ifdef REAL_YARA
  yyscan_t yyscanner;

  compiler->errors = 0;

  if (setjmp(compiler->error_recovery) != 0)
    return compiler->errors;

  yylex_init(&yyscanner);

  yyset_debug(1, yyscanner);

  yyset_extra(compiler, yyscanner);

  yy_scan_string(rules_string, yyscanner);

  yyset_lineno(1, yyscanner);
  yyparse(yyscanner, compiler);
  yylex_destroy(yyscanner);

  return compiler->errors;
#else
  (void)rules_string;
  (void)compiler;
  cli_errmsg("yara_lexer:yr_lex_parse_rules_string() disabled\n");
  return 0;
#endif
}


int yr_lex_parse_rules_file(
  FILE* rules_file,
  YR_COMPILER* compiler)
{
  yyscan_t yyscanner;

  compiler->errors = 0;

  if (setjmp(compiler->error_recovery) != 0)
    return compiler->errors;

  yylex_init(&yyscanner);

  #if YYDEBUG
  printf("debug enabled");
  #endif

  yyset_debug(1, yyscanner);

  yyset_in(rules_file, yyscanner);
  yyset_extra(compiler, yyscanner);
  yyparse(yyscanner, compiler);
  yylex_destroy(yyscanner);

  return compiler->errors;
}