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/*
******************************************************************************
*
* File: knopmd.c
*
* Purpose: knopmd separates iptables messages from all other kernel
* messages. NOTE: This daemon is obselete since the main method
* of passive authorization is Single Packet Authorization (SPA),
* which offers better security properties than port knocking.
*
* Author: Michael Rash (mbr@cipherdyne.org)
*
* Version: 1.8
*
* Copyright (C) 2004-2009 Michael Rash (mbr@cipherdyne.org)
*
* License (GNU Public License):
*
* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
* NOTE: This code is essentially borrowed from kmsgsd.c that is bundled
* psad: http://www.cipherdyne.org/psad/
*
******************************************************************************
*
* $Id: knopmd.c 1519 2009-08-11 23:56:57Z mbr $
*/
/* includes */
#include "fwknop.h"
#include <getopt.h>
/* defines */
#define FWKNOP_CONF "/etc/fwknop/fwknop.conf"
/* globals */
static volatile sig_atomic_t received_sighup = 0;
extern char *optarg; /* for getopt */
extern int optind; /* for getopt */
char *fw_msg_search[MAX_GEN_LEN];
int num_fw_search_strings = 0;
int fw_search_all_flag = 1; /* default to parse all iptables messages */
char fwknopfifo_file[MAX_PATH_LEN];
char fwdata_file[MAX_PATH_LEN];
char config_file[MAX_PATH_LEN];
char fw_search_file[MAX_PATH_LEN];
char knopmd_pid_file[MAX_PATH_LEN];
char fwknop_dir[MAX_PATH_LEN];
char fwknop_fifo_dir[MAX_PATH_LEN];
char fwknop_run_dir[MAX_PATH_LEN];
/* prototypes */
static void parse_config(void);
static void find_sub_var_value(
char *value,
char *sub_var,
char *pre_str,
char *post_str
);
static void expand_config_vars(void);
static void check_auth_mode(void);
static int match_fw_msg(char *fw_mgs);
static void sighup_handler(int sig);
/* main */
int main(int argc, char *argv[]) {
char buf[MAX_LINE_BUF];
int fifo_fd, fwdata_fd; /* file descriptors */
int cmdlopt, numbytes;
#ifdef DEBUG
int matched_ipt_log_msg = 0;
int fwlinectr = 0;
#endif
#ifdef DEBUG
fprintf(stderr, "[+] Entering DEBUG mode\n");
fprintf(stderr, "[+] Firewall messages will be written to both ");
fprintf(stderr, "STDOUT _and_ to fwdata.\n\n");
#endif
strlcpy(config_file, FWKNOP_CONF, MAX_PATH_LEN);
while((cmdlopt = getopt(argc, argv, "c:")) != -1) {
switch(cmdlopt) {
case 'c':
strlcpy(config_file, optarg, MAX_PATH_LEN);
break;
default:
printf("[+] Usage: knopmd [-c <config file>] ");
exit(EXIT_FAILURE);
}
}
#ifdef DEBUG
fprintf(stderr, "[+] parsing config_file: %s\n", config_file);
#endif
/* parse config file (knopmd.conf) */
parse_config();
/* make sure there isn't another knopmd already running */
check_unique_pid(knopmd_pid_file, "knopmd");
#ifndef DEBUG
/* become a daemon */
daemonize_process(knopmd_pid_file);
#endif
/* install signal handler for HUP signals */
signal(SIGHUP, sighup_handler);
/* start doing the real work now that the daemon is running and
* the config file has been processed */
/* open the fwknopfifo named pipe. Note that we are opening the pipe
* _without_ the O_NONBLOCK flag since we want the read on the file
* descriptor to block until there is something new in the pipe.
* Also, not that we are opening with O_RDWR, since this seems to
* fix the problem with knopmd not blocking on the read() if the
* system logger dies (and hence closes its file descriptor for the
* fwknopfifo). */
if ((fifo_fd = open(fwknopfifo_file, O_RDWR)) < 0) {
fprintf(stderr, "[-] Could not open %s for reading.\n",
fwknopfifo_file);
exit(EXIT_FAILURE); /* could not open fwknopfifo named pipe */
}
/* open the fwdata file in append mode so we can write messages from
* the pipe into this file. */
if ((fwdata_fd = open(fwdata_file,
O_CREAT|O_WRONLY|O_APPEND, 0600)) < 0) {
fprintf(stderr, "[-] Could not open %s for writing.\n", fwdata_file);
exit(EXIT_FAILURE); /* could not open fwdata file */
}
/* MAIN LOOP;
* Read data from the pipe indefinitely (we opened it _without_
* O_NONBLOCK) and write it to the fwdata file if it is a firewall message
*/
while ((numbytes = read(fifo_fd, buf, MAX_LINE_BUF-1)) >= 0) {
#ifdef DEBUG
fprintf(stderr,
"read %d bytes from %s fifo.\n", numbytes, fwknopfifo_file);
#endif
/* make sure the buf contents qualifies as a string */
buf[numbytes] = '\0';
if (received_sighup) {
/* clear the signal flag */
received_sighup = 0;
/* re-parse the config file after receiving HUP signal */
parse_config();
/* close file descriptors and re-open them after
* re-reading config file */
close(fifo_fd);
close(fwdata_fd);
/* re-open fwknopfifo and fwdata files */
if ((fifo_fd = open(fwknopfifo_file, O_RDONLY)) < 0) {
fprintf(stderr, "[-] Could not open %s for reading.\n",
fwknopfifo_file);
exit(EXIT_FAILURE); /* could not open fwknopfifo named pipe */
}
if ((fwdata_fd = open(fwdata_file, O_CREAT|O_WRONLY|O_APPEND,
0600)) < 0) {
fprintf(stderr, "[-] Could not open %s for writing.\n",
fwdata_file);
exit(EXIT_FAILURE); /* could not open fwdata file */
}
slogr("fwknop(knopmd)",
"[+] received HUP signal, re-imported knopmd.conf");
}
/* see if we matched a firewall message and write it to the
* fwdata file */
if ((strstr(buf, "OUT") != NULL
&& strstr(buf, "IN") != NULL)) {
if (! fw_search_all_flag) { /* we are looking for specific log prefixes */
if (match_fw_msg(buf)) {
if (write(fwdata_fd, buf, numbytes) < 0) {
exit(EXIT_FAILURE); /* could not write to the fwdata file */
}
#ifdef DEBUG
matched_ipt_log_msg = 1;
#endif
}
} else {
if (write(fwdata_fd, buf, numbytes) < 0)
exit(EXIT_FAILURE); /* could not write to the fwdata file */
#ifdef DEBUG
matched_ipt_log_msg = 1;
#endif
}
#ifdef DEBUG
if (matched_ipt_log_msg) {
puts(buf);
fprintf(stderr, "[+] Line matched search strings.\n");
fwlinectr++;
if (fwlinectr % 50 == 0)
fprintf(stderr,
"[+] Processed %d firewall lines.\n", fwlinectr);
matched_ipt_log_msg = 0;
} else {
puts(buf);
printf("[-] Line did not match search strings.\n");
}
#endif
}
}
/* these statements don't get executed, but for completeness... */
close(fifo_fd);
close(fwdata_fd);
exit(EXIT_SUCCESS);
}
/******************** end main ********************/
static int match_fw_msg(char *fw_msg)
{
int i;
for (i=0; i < num_fw_search_strings; i++)
if (strstr(fw_msg, fw_msg_search[i]) != NULL)
return 1;
return 0;
}
static void parse_config(void)
{
FILE *config_ptr; /* FILE pointer to the config file */
unsigned int linectr = 0, i;
char config_buf[MAX_LINE_BUF], tmp_fw_search_buf[MAX_GEN_LEN];
char *index;
/* first check to see if knopmd should not be running (i.e.
* AUTH_MODE in the fwknop.conf file is set to a pcap-based
* method). */
check_auth_mode();
for (i=0; i < num_fw_search_strings; i++)
free(fw_msg_search[i]);
num_fw_search_strings = 0;
fw_msg_search[num_fw_search_strings] = NULL;
if ((config_ptr = fopen(config_file, "r")) == NULL) {
fprintf(stderr, "[-] Could not open %s for reading.\n",
config_file);
exit(EXIT_FAILURE);
}
/* increment through each line of the config file */
while ((fgets(config_buf, MAX_LINE_BUF, config_ptr)) != NULL) {
linectr++;
/* set the index pointer to the beginning of the line */
index = config_buf;
/* advance the index pointer through any whitespace
* at the beginning of the line */
while (*index == ' ' || *index == '\t') index++;
/* skip comments and blank lines, etc. */
if ((*index != '#') && (*index != '\n') &&
(*index != ';') && (index != NULL)) {
find_char_var("FWKNOP_DIR", fwknop_dir, index);
find_char_var("KNOPMD_FIFO", fwknopfifo_file, index);
find_char_var("FW_DATA_FILE", fwdata_file, index);
find_char_var("KNOPMD_PID_FILE", knopmd_pid_file, index);
find_char_var("FWKNOP_LIB_DIR", fwknop_fifo_dir, index);
find_char_var("FWKNOP_RUN_DIR", fwknop_run_dir, index);
if (find_char_var("FW_MSG_SEARCH", tmp_fw_search_buf, index)) {
fw_msg_search[num_fw_search_strings]
= (char *) safe_malloc(strlen(tmp_fw_search_buf)+1);
strlcpy(fw_msg_search[num_fw_search_strings],
tmp_fw_search_buf, MAX_GEN_LEN);
num_fw_search_strings++;
}
if (find_char_var("FW_SEARCH_ALL", tmp_fw_search_buf, index)) {
if (tmp_fw_search_buf[0] == 'N')
fw_search_all_flag = 0;
}
}
}
fclose(config_ptr);
/* resolve any embedded variables */
expand_config_vars();
#ifdef DEBUG
fprintf(stderr, "[+] FWKNOP_DIR: %s\n", fwknop_dir);
fprintf(stderr, "[+] KNOPMD_FIFO: %s\n", fwknopfifo_file);
fprintf(stderr, "[+] FW_DATA_FILE: %s\n", fwdata_file);
fprintf(stderr, "[+] KNOPMD_PID_FILE: %s\n", knopmd_pid_file);
#endif
return;
}
static void check_auth_mode(void)
{
FILE *config_ptr; /* FILE pointer to the config file */
char config_buf[MAX_LINE_BUF];
char auth_mode[MAX_GEN_LEN];
char *index;
if ((config_ptr = fopen(FWKNOP_CONF, "r")) == NULL) {
fprintf(stderr, "[-] Could not open %s for reading.\n",
FWKNOP_CONF);
exit(EXIT_FAILURE);
}
auth_mode[0] = '\0';
/* increment through each line of the config file */
while ((fgets(config_buf, MAX_LINE_BUF, config_ptr)) != NULL) {
/* set the index pointer to the beginning of the line */
index = config_buf;
/* advance the index pointer through any whitespace
* at the beginning of the line */
while (*index == ' ' || *index == '\t') index++;
/* skip comments and blank lines, etc. */
if ((*index != '#') && (*index != '\n') &&
(*index != ';') && (index != NULL)) {
find_char_var("AUTH_MODE ", auth_mode, index);
}
}
fclose(config_ptr);
/* see if we are using the ULOG_PCAP mode */
if (strncmp(auth_mode, "ULOG_PCAP", MAX_GEN_LEN) == 0)
exit(EXIT_FAILURE);
/* see if we are using the PCAP mode */
if (strncmp(auth_mode, "PCAP", MAX_GEN_LEN) == 0)
exit(EXIT_FAILURE);
return;
}
static void expand_config_vars(void)
{
char sub_var[MAX_GEN_LEN] = "";
char pre_str[MAX_GEN_LEN] = "";
char post_str[MAX_GEN_LEN] = "";
int found_sub_var = 1, resolve_ctr = 0;
while (found_sub_var) {
resolve_ctr++;
if (resolve_ctr >= 20) {
fprintf(stderr, "[*] Exceeded maximum variable resolution attempts.\n");
exit(EXIT_FAILURE);
}
found_sub_var = 0;
if (has_sub_var("FW_DATA_FILE", fwdata_file, sub_var,
pre_str, post_str)) {
find_sub_var_value(fwdata_file, sub_var, pre_str, post_str);
found_sub_var = 1;
}
if (has_sub_var("KNOPMD_FIFO", fwknopfifo_file, sub_var,
pre_str, post_str)) {
find_sub_var_value(fwknopfifo_file, sub_var, pre_str, post_str);
found_sub_var = 1;
}
if (has_sub_var("KNOPMD_PID_FILE", knopmd_pid_file, sub_var,
pre_str, post_str)) {
find_sub_var_value(knopmd_pid_file, sub_var, pre_str, post_str);
found_sub_var = 1;
}
}
return;
}
static void find_sub_var_value(char *value, char *sub_var, char *pre_str,
char *post_str)
{
int found_var = 0;
if (strncmp(sub_var, "FWKNOP_DIR", MAX_GEN_LEN) == 0) {
strlcpy(sub_var, fwknop_dir, MAX_GEN_LEN);
found_var = 1;
} else if (strncmp(sub_var, "FWKNOP_LIB_DIR", MAX_GEN_LEN) == 0) {
strlcpy(sub_var, fwknop_fifo_dir, MAX_GEN_LEN);
found_var = 1;
} else if (strncmp(sub_var, "FWKNOP_RUN_DIR", MAX_GEN_LEN) == 0) {
strlcpy(sub_var, fwknop_run_dir, MAX_GEN_LEN);
found_var = 1;
} else if (strncmp(sub_var, "FW_DATA_FILE", MAX_GEN_LEN) == 0) {
strlcpy(sub_var, fwdata_file, MAX_GEN_LEN);
found_var = 1;
} else if (strncmp(sub_var, "KNOPMD_FIFO", MAX_GEN_LEN) == 0) {
strlcpy(sub_var, fwknopfifo_file, MAX_GEN_LEN);
found_var = 1;
} else if (strncmp(sub_var, "KNOPMD_PID_FILE", MAX_GEN_LEN) == 0) {
strlcpy(sub_var, knopmd_pid_file, MAX_GEN_LEN);
found_var = 1;
}
if (found_var) {
/* substitute the variable value */
expand_sub_var_value(value, sub_var, pre_str, post_str);
} else {
fprintf(stderr, "[*] Could not resolve sub-var: %s to a value.\n",
sub_var);
exit(EXIT_FAILURE);
}
return;
}
static void sighup_handler(int sig)
{
received_sighup = 1;
}
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