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#include "http_config.h"
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#include "http_protocol.h"
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#include "apr_optional.h"
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#include "modsecurity.h"
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#define ALPHABET_SIZE 256
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#define MAX_PATTERN_SIZE 64
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static void initBoyerMooreHorspool(const char *pattern, int patlength,
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int *bm_badcharacter_array);
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static int BoyerMooreHorspool(const char *pattern, int patlength,
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const char *text, int textlen, int *bm_badcharacter_array);
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* Operator parameter initialisation entry point.
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static int op_strstr_init(msre_rule *rule, char **error_msg) {
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/* Operator initialisation function will be called once per
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* statement where operator is used. It is meant to be used
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* to check the parameters to see whether they are present
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* and if they are in the correct format.
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/* In this example we just look for a simple non-empty parameter. */
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if ((rule->op_param == NULL)||(strlen(rule->op_param) == 0)) {
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*error_msg = apr_psprintf(rule->ruleset->mp, "Missing parameter for operator 'strstr'.");
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/* If you need to transform the data in the parameter into something
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* else you should do that here. Simply create a new structure to hold
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* the transformed data and place the pointer to it into rule->op_param_data.
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* You will have access to this pointer later on.
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rule->op_param_data = apr_pcalloc(rule->ruleset->mp, ALPHABET_SIZE * sizeof(int));
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initBoyerMooreHorspool(rule->op_param, strlen(rule->op_param), (int *)rule->op_param_data);
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* Operator execution entry point.
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static int op_strstr_exec(modsec_rec *msr, msre_rule *rule, msre_var *var, char **error_msg) {
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/* Here we need to inspect the contents of the supplied variable. */
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/* In a general case it is possible for the value
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* to be NULL. What you need to do in this case
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* depends on your operator. In this example we return
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* a "no match" response.
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if (var->value == NULL) return 0; /* No match. */
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/* Another thing to note is that variables are not C strings,
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* meaning the NULL byte is not used to determine the end
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* of the string. Variable length var->value_len should be
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* used for this purpose.
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if (BoyerMooreHorspool(rule->op_param, strlen(rule->op_param),
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var->value, var->value_len, (int *)rule->op_param_data) >= 0)
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return 1; /* Match. */
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return 0; /* No match. */
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static int hook_pre_config(apr_pool_t *mp, apr_pool_t *mp_log, apr_pool_t *mp_temp) {
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void (*fn)(const char *name, void *fn_init, void *fn_exec);
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/* Look for the registration function
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* exported by ModSecurity.
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fn = APR_RETRIEVE_OPTIONAL_FN(modsec_register_operator);
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/* Use it to register our new
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* transformation function under the
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fn("strstr", (void *)op_strstr_init, (void *)op_strstr_exec);
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static void register_hooks(apr_pool_t *p) {
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ap_hook_pre_config(hook_pre_config, NULL, NULL, APR_HOOK_LAST);
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/* Dispatch list for API hooks */
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module AP_MODULE_DECLARE_DATA op_strstr_module = {
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STANDARD20_MODULE_STUFF,
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NULL, /* create per-dir config structures */
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NULL, /* merge per-dir config structures */
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NULL, /* create per-server config structures */
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NULL, /* merge per-server config structures */
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NULL, /* table of config file commands */
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register_hooks /* register hooks */
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This example uses an implementation Boyer-Moore-Horspool
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matching algorithm as implemented in Streamline (http://ffpf.sourceforge.net).
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Copyright (c) 2004-2006, Vrije Universiteit Amsterdam
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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Neither the name of the Vrije Universiteit nor the names of its contributors
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may be used to endorse or promote products derived from this software without
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specific prior written permission.
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static void precompute_badcharacter(const char *pattern, int patlength,
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int bm_badcharacter_array[])
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for (i = 0; i < ALPHABET_SIZE; ++i) {
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bm_badcharacter_array[i] = patlength;
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for (i = 0; i < patlength - 1; ++i){
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bm_badcharacter_array[(uint8_t)pattern[i]] = patlength - i - 1;
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static void initBoyerMooreHorspool(const char *pattern, int patlength,
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int *bm_badcharacter_array)
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precompute_badcharacter(pattern,
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(patlength < MAX_PATTERN_SIZE ? patlength : MAX_PATTERN_SIZE), bm_badcharacter_array);
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static int BoyerMooreHorspool(const char *pattern, int patlength,
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const char *text, int textlen, int *bm_badcharacter_array)
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while (j <= textlen - patlength) {
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c = text[j + patlength - 1];
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if (pattern[patlength - 1] == c && memcmp(pattern, text + j, patlength - 1) == 0) {
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j += bm_badcharacter_array[(uint8_t)c];
added
removed
apache2/api/mod_op_strstr.c
