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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
/*------------------------------------------------------------*/
#define RULE_LINE_LEN 4096
#define MAX_CONTENT 2048
#define HEADER_LEN 54
#define MAX_RULE 8192
#define UNUSED(x) (void)x
/* content & regular expression g_vars */
//static char **g_pcre_string;
//static int *g_pcre_len;
char **g_content;
int *g_content_len;
char *null_payload;
static const int packet_size = 1514;
/* Function headers */
int readSnortRules(const char *);
void cleanupRules(int);
/*------------------------------------------------------------*/
int
readSnortRules(const char *filename)
{
FILE *fp;
char *p, *result, *saveptr, *temp, *end, *pcre[MAX_RULE];
char line[RULE_LINE_LEN], new_content[MAX_CONTENT], ox[2];
int num_rule, i, j, loc, len_temp, flag, hex_num, rule_dec;
char hex[6] = "0x";
/* set null_payload */
null_payload = calloc(1, packet_size);
if (null_payload == NULL) {
fprintf(stderr, "Not enough memory to initialize null payload!\n");
exit(EXIT_FAILURE);
}
loc = num_rule = flag = rule_dec = 0;
/* calculate number of rules */
if ((fp = fopen(filename, "r")) == NULL) {
fprintf(stderr, "[%s:%d]] File %s failed to open!\n",
__FUNCTION__, __LINE__, filename);
exit(EXIT_FAILURE);
}
while (fgets(line, sizeof(line), fp) != NULL) {
if (*line == '#' || *line == '\0')
continue;
else
num_rule++;
}
/*
* rewind. I know this is inefficent, but will improve
* on this in the next iteration
*/
rewind(fp);
/* for content */
if ((p = (char *)calloc(/*4 * */sizeof(char),
MAX_CONTENT * num_rule)) == NULL) {
fprintf(stderr, "[%s:%d] Memory allocation for "
"contents failed\n", __FUNCTION__, __LINE__);
exit(EXIT_FAILURE);
}
if ((g_content = (char **)calloc(num_rule,
sizeof(char *))) == NULL) {
fprintf(stderr, "[%s:%d] Malloc for content failed\n",
__FUNCTION__, __LINE__);
exit(EXIT_FAILURE);
}
if ((g_content_len = (int *)calloc(num_rule,
sizeof(int))) == NULL) {
fprintf(stderr, "[%s:%d] Malloc for g_content_len failed\n",
__FUNCTION__, __LINE__);
exit(EXIT_FAILURE);
}
for (i = 0; i < num_rule; i++) {
if (fgets(line, sizeof(line), fp) == NULL) {
fprintf(stderr, "[%s:%d] Reading %dth rule failed\n",
__FUNCTION__, __LINE__, i);
exit(EXIT_FAILURE);
}
result = strstr(line, "content:");
if (result == NULL) {
strcpy(new_content, "No_Content");
loc = strlen(new_content);
} else {
result = strtok_r(result, "\"", &saveptr);
result = strtok_r(NULL, "\"", &saveptr);
if ((temp = strdup(result)) == NULL) {
fprintf(stderr, "[%s:%d] Reading content failed\n",
__FUNCTION__, __LINE__);
exit(EXIT_FAILURE);
}
len_temp = strlen(temp);
memset(new_content, 0, MAX_CONTENT);
for (j = 0; j < len_temp; j++) {
if (temp[j] == '|') {
if (flag == false) {
flag = true;
continue;
} else if (flag == true) {
flag = false;
continue;
}
}
if (flag == true) {
if (temp[j] == ' ')
continue;
memset(hex, 0, 5);
strcpy(hex, "0x");
ox[0] = temp[j];
ox[1] = temp[j + 1];
strncat(hex, ox, 2);
sscanf(hex, "0x%2X", &hex_num);
new_content[loc] = hex_num;
loc++;
j++;
} else if (flag == false) {
new_content[loc] = temp[j];
loc++;
}
}
free(temp);
}
if (loc + 1 <= packet_size - HEADER_LEN) {
memcpy(p, new_content, loc + 1);
g_content[i - rule_dec] = p;
g_content_len[i - rule_dec] = loc + 1;
p += (loc + 1);
} else
rule_dec++;
flag = false;
loc = 0;
}
/* rewind again */
rewind(fp);
#if 0
for (i = 0; i < num_rule; i++) {
if (fgets(line, sizeof(line), fp) == NULL) {
fprintf(stderr, "[%s:%d]: Reading %dth rule failed\n",
__FUNCTION__, __LINE__, i);
exit(EXIT_FAILURE);
}
result = strstr(line, "pcre:");
if (result == NULL)
continue;
end = strstr(result, "\"");
result = end + 1;
end = strstr(result, "\"; ");
end[0] = '\0';
if ((temp = strdup(result)) == NULL) {
fprintf(stderr, "[%s:%d] Reading PCRE failed\n",
__FUNCTION__, __LINE__);
exit(EXIT_FAILURE);
}
pcre[i] = temp;
}
#endif
fclose(fp);
#ifdef TEST_SNORT_RULE_PARSING
printf("rule_dec: %d\n", rule_dec);
for(i = 0; i < num_rule - rule_dec; i++) {
fprintf(stdout, "%d: content: ", i);
for (j = 0; j < g_content_len[i]; j++)
fprintf(stdout, "0x%02X ", g_content[i][j]);
fprintf(stdout, "pcre: %s\n", pcre[i]);
}
#else
UNUSED(pcre);
#endif
UNUSED(end);
return num_rule - rule_dec;
}
/*------------------------------------------------------------*/
void
cleanupRules(int num_rules)
{
/* freeing up all resources allocated */
free(null_payload);
free(g_content_len);
free(g_content);
}
/*------------------------------------------------------------*/
#ifdef TEST_SNORT_RULE_PARSING
int
main(int argc, char **argv)
{
int num_rules;
if (argc != 2) {
fprintf(stderr, "[%s:%d]Usage: %s <snort_rule_file>\n",
__FUNCTION__, __LINE__, argv[0]);
exit(EXIT_FAILURE);
}
num_rules = readSnortRules(argv[1]);
if (num_rules <= 0) {
fprintf(stderr, "[%s:%d] There are no rules in the file\n",
__FUNCTION__, __LINE__);
exit(EXIT_FAILURE);
}
cleanupRules(num_rules);
return EXIT_SUCCESS;
}
#endif
/*------------------------------------------------------------*/
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