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vpntlsserver.c
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vpntlsserver.c
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#include <arpa/inet.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <netdb.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <fcntl.h>
#include <linux/if.h>
#include <linux/if_tun.h>
#include <sys/ioctl.h>
#include <shadow.h>
#include <crypt.h>
#include <signal.h>
volatile sig_atomic_t exit_now = 0;
#define CHK_SSL(err) if ((err) < 1) { \
perror("Error"); \
int macro_sslerr = SSL_get_error(ssl, err); \
fprintf(stderr, "SSL ERROR %d\n", macro_sslerr); \
ERR_print_errors_fp(stderr); \
exit(2); \
}
#define CHK_ERR(err,s) if ((err)==-1) { perror(s); exit(1); }
#define MAX_CLIENTS 5
#define BUFF_SIZE 2000
#define CREDENTIAL_LEN 256
// volatile sig_atomic_t child_pids[] = sig_atomic_t[MAX_CLIENTS];
void signal_handler(int signal)
{
exit_now = 1;
}
int setupTCPServer(); // Defined in Listing 19.10
void processRequest(SSL* ssl, int sock); // Defined in Listing 19.12
int login(char *user, char *passwd)
{
struct spwd *pw;
char *epasswd;
pw = getspnam(user);
if (pw == NULL) {
return -1;
}
epasswd = crypt(passwd, pw->sp_pwdp);
int res = strcmp(epasswd, pw->sp_pwdp);
if (res == 0) {
return 1;
}
printf("Bad\n");
return -1;
}
/*
void sigchildhandle(int signum) {
int wstat;
union wait wstat;
pid_t pid;
while (TRUE) {
pid = wait3 (&wstat, WNOHANG, (struct rusage *)NULL );
if (pid == 0)
return;
else if (pid == -1)
return;
else {
printf ("Child Return code: %d\n", wstat.w_retcode);
for (int i = 0; i < MAX_CLIENTS; i++) {
if (child_pids[i] == pid) {
child_pids[i] = -1
}
}
}
}
}
*/
int createTunDevice()
{
int tunfd;
struct ifreq ifr;
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
tunfd = open("/dev/net/tun", O_RDWR);
ioctl(tunfd, TUNSETIFF, &ifr);
return tunfd;
}
int setupTCPServer()
{
struct sockaddr_in sa_server;
int listen_sock;
listen_sock= socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
CHK_ERR(listen_sock, "socket");
memset (&sa_server, '\0', sizeof(sa_server));
sa_server.sin_family = AF_INET;
sa_server.sin_addr.s_addr = INADDR_ANY;
sa_server.sin_port = htons (4433);
int err = bind(listen_sock, (struct sockaddr*)&sa_server, sizeof(sa_server));
CHK_ERR(err, "bind");
err = listen(listen_sock, 5);
CHK_ERR(err, "listen");
return listen_sock;
}
int childProcess(SSL* ssl, int sock, int parent_pipe_fd, int tunfd, int curr_client_no) {
SSL_set_fd (ssl, sock);
int err = SSL_accept (ssl);
CHK_SSL(err);
printf ("SSL connection established!\n");
in_addr_t conf_ip;
char user[CREDENTIAL_LEN];
char pass[CREDENTIAL_LEN];
bzero (&user, sizeof(char) * CREDENTIAL_LEN);
bzero (&pass, sizeof(char) * CREDENTIAL_LEN);
// Read IP addr so this child knows when to send.
SSL_read(ssl,&conf_ip,sizeof(in_addr_t));
// Read User & pass as user\r\npass\r\n.
SSL_read(ssl,&user,CREDENTIAL_LEN);
SSL_read(ssl,&pass,CREDENTIAL_LEN);
// Crop off \n
user[strlen((const char *)&user) - 1] = 0;
pass[strlen((const char *)&pass)] = 0;
int authorized = login(user, pass);
if (authorized == 1) {
fprintf(stderr, "Child %d - Access Granted. User: %s\n", curr_client_no, user);
SSL_write(ssl, "Authorized. \r\n", strlen("Authorized. \r\n"));
} else {
fprintf(stderr, "Child %d - Access Denied. User: %s\n", curr_client_no, user);
SSL_write(ssl, "Not Authorized.\r\n", strlen("Not Authorized.\r\n"));
SSL_shutdown(ssl); SSL_free(ssl);
return 1;
}
int len;
char buff[BUFF_SIZE];
char addr_as_string[INET_ADDRSTRLEN];
int read_blocked = 0;
inet_ntop(AF_INET, &conf_ip, addr_as_string, INET_ADDRSTRLEN);
printf ("Handled IP: %s\n", addr_as_string);
while (1) {
bzero(buff, BUFF_SIZE);
// Need to select on sock & pipe.
fd_set readFDSet;
FD_ZERO(&readFDSet);
FD_SET(sock, &readFDSet);
FD_SET(parent_pipe_fd, &readFDSet);
select(FD_SETSIZE, &readFDSet, NULL, NULL, NULL);
if (FD_ISSET(sock, &readFDSet)) {
// need to check for SSL errors
// Source: http://www.past5.com/tutorials/2014/02/21/openssl-and-select/
do {
read_blocked = 0;
int len = SSL_read(ssl,buff,BUFF_SIZE);
printf("SSL_read returned %d for Child %d\n", len, curr_client_no);
int ssl_error;
//check SSL errors
switch(ssl_error = SSL_get_error(ssl,len)){
case SSL_ERROR_NONE:
// Normal
printf("Read %d bytes from SSL tunnel for Child %d\n", len, curr_client_no);
len = write(tunfd, &buff, len);
if (len == 0) {
printf("Wrote zero bytes to TUN for Child %d\n", curr_client_no);
} else if (len < 0) {
fprintf(stderr, "Bad Write to TUN for child %d ", curr_client_no);
perror("Bad write to TUN");
} else {
printf("Wrote %d bytes to TUN for Child %d\n", len, curr_client_no);
}
break;
case SSL_ERROR_ZERO_RETURN:
//connection closed by client, clean up
printf("Client closed connection - child %d\n", curr_client_no);
SSL_shutdown(ssl); SSL_free(ssl);
return 0;
break;
case SSL_ERROR_WANT_READ:
//the operation did not complete, block the read
read_blocked = 1;
break;
case SSL_ERROR_WANT_WRITE:
//the operation did not complete
fprintf(stderr, "SSL_ERROR_WANT_WRITE - client %d\n", curr_client_no);
break;
case SSL_ERROR_SYSCALL:
//some I/O error occured (could be caused by false start in Chrome for instance), disconnect the client and clean up
fprintf(stderr, "SSL_ERROR_SYSCALL - client %d\n", curr_client_no);
ERR_print_errors_fp(stderr);
perror("Syscall error");
return 2;
break;
default:
//some other error, clean up
fprintf(stderr, "Other Read error - client %d\n", curr_client_no);
return 4;
}
} while (SSL_pending(ssl) && !read_blocked);
}
if (FD_ISSET(parent_pipe_fd, &readFDSet)) {
// Just forward along
// Wrong, only read the actual length set.
int supposed_to_read;
len = read(parent_pipe_fd, (char*)&supposed_to_read, 4);
len = read(parent_pipe_fd, buff, supposed_to_read);
printf("Read %d bytes from parent for Child %d\n", len, curr_client_no);
// len = read(tunfd, buff, BUFF_SIZE);
// need to send to child. But which one?
// bytes 30-33
if (len < 0) {
perror("Bad Read, quitting.");
return -1;
}
if (len < 34) {
// IPv4 header not present, bail.
printf("IPv4 Header not found, dropping packet.\n");
return 0;
}
in_addr_t dst_ip = *(in_addr_t*)(buff + 16); // please don't hate me!
// Take 4 bytes starting at byte 30; read as int.
// no, we're not checking the checksum.
inet_ntop(AF_INET, &dst_ip, addr_as_string, INET_ADDRSTRLEN);
printf("DST: %s\n", addr_as_string);
if (conf_ip != dst_ip) {
printf("Wrong child.\n");
continue;
}
int ret = SSL_write(ssl, &buff, len);
if (ret > 0) {
// no error
printf("Wrote %d bytes to SSL tunnel for child %d\n", ret, curr_client_no);
} else if (ret == 0) {
// error, likely close/shutdown
SSL_shutdown(ssl); SSL_free(ssl);
break;
} else {
// error, die
exit(1);
}
}
}
return 0;
}
// Two locations we can read from: SSL connection & TUN.
// if from SSL, then send to TUN.
// if from TUN then send to SSL.
// From tun0 -> SSL
int tunSelected(SSL* ssl, int tunfd, struct sockaddr_in *client_addrs, int curr_client_no, int pipe_fd_children[MAX_CLIENTS][2]){
// The hard one.
int len;
char buff[BUFF_SIZE];
char addr_as_string[INET_ADDRSTRLEN];
bzero(buff, BUFF_SIZE);
len = read(tunfd, buff, BUFF_SIZE);
// need to send to child. But which one?
// bytes 30-33
if (len < 0) {
perror("Bad Read, quitting.");
return -1;
}
if (len < 34) {
// IPv4 header not present, bail.
perror("IPv4 Header not found, dropping packet.\n");
return 0;
}
in_addr_t dst_ip = *(in_addr_t*)(buff + 16); // please don't hate me!
// Take 4 bytes starting at byte 30; read as int.
// no, we're not checking the checksum.
inet_ntop(AF_INET, &dst_ip, addr_as_string, INET_ADDRSTRLEN);
printf("Parent DST: %s\n", addr_as_string);
if (strncmp("192.168.5",addr_as_string,9) != 0) {
printf(" Bad Packet.\n");
//return 0;
}
printf("Parent Got %d bytes from TUN\n", len);
for (int i = 0; i < curr_client_no; i++) {
//inet_ntop(AF_INET, &client_addrs[i].sin_addr.s_addr, addr_as_string, INET_ADDRSTRLEN);
//printf("Potential: %s\n", addr_as_string);
//if (client_addrs[i].sin_addr.s_addr == dst_ip) {
//printf("Packet for child %d", i);
// found it!
char size_of_write[4];
memcpy(size_of_write, (char*)&len, sizeof(char) * 4);
int res = write(pipe_fd_children[i][1], &size_of_write, 4);
res = write(pipe_fd_children[i][1], &buff, len);
if (res < 0) {
// failed
if (errno == EBADF) {
continue;
}
if (errno == EPIPE) {
// we ignore this error, means a child closed out.
continue;
} else {
fprintf(stderr, "Write to child %d - ", i);
perror("Write failed");
return 1;
}
} else {
printf("Write to pipe for child %d\n", i);
}
//}
}
// fprintf(stderr, "Client not found, dropping packet\n");
return 0;
}
int main(){
SSL_METHOD *meth;
SSL_CTX* ctx;
SSL *ssl;
// int err;
int curr_client_no = 0;
// To handle Ctrl-C
signal(SIGTERM, signal_handler);
// To silence sigpipe
signal(SIGPIPE, SIG_IGN);
/*
if (signal(SIGCHLD, SIG_IGN) == SIG_ERR) {
perror(0);
exit(1);
}
*/
int pipe_fds[MAX_CLIENTS][2];
int tunfd;
struct sockaddr_in client_addrs[MAX_CLIENTS];
struct sockaddr_in client1;
memset(&client_addrs, 0, sizeof(struct sockaddr_in) * MAX_CLIENTS);
memset(&client1, 0, sizeof(struct sockaddr_in));
size_t client_lengths[MAX_CLIENTS];
for (int i = 0; i < MAX_CLIENTS; i++) {
client_lengths[i] = sizeof(struct sockaddr_in);
}
tunfd = createTunDevice();
// Step 0: OpenSSL library initialization
// This step is no longer needed as of version 1.1.0.
SSL_library_init();
SSL_load_error_strings();
SSLeay_add_ssl_algorithms();
// Step 1: SSL context initialization
meth = (SSL_METHOD *)TLSv1_2_method();
ctx = SSL_CTX_new(meth);
SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, NULL);
// Step 2: Set up the server certificate and private key
SSL_CTX_use_certificate_file(ctx, "./cert_server/mig_cert.pem", SSL_FILETYPE_PEM);
SSL_CTX_use_PrivateKey_file(ctx, "./cert_server/mig_key.pem", SSL_FILETYPE_PEM);
// Step 3: Create a new SSL structure for a connection
ssl = SSL_new (ctx);
// struct sockaddr_in sa_client;
// size_t client_len;
int listen_sock = setupTCPServer();
int do_listen = 1;
while (1) {
if (exit_now) {
exit (0);
}
if (do_listen == 0 || curr_client_no >= MAX_CLIENTS) {
do_listen = 0;
close(listen_sock);
}
fd_set readFDSet;
FD_ZERO(&readFDSet);
if (do_listen == 1) {
FD_SET(listen_sock, &readFDSet);
printf("Parent Listening\n");
} else {
printf("Waiting For Packets\n");
}
FD_SET(tunfd, &readFDSet);
select(FD_SETSIZE, &readFDSet, NULL, NULL, NULL);
if (FD_ISSET(listen_sock, &readFDSet)) {
struct sockaddr_in* currclient = &client_addrs[MAX_CLIENTS];
int sock = accept(listen_sock, (struct sockaddr*)currclient, &client_lengths[curr_client_no]);
char addr_as_string[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &(currclient->sin_addr).s_addr, addr_as_string, INET_ADDRSTRLEN);
printf("Parent Accepted from %s\n", addr_as_string);
// only make pipes as needed
if (pipe(pipe_fds[curr_client_no]) == -1) {
perror("pipe");
exit(1);
}
pid_t child_pid = fork();
if (child_pid == 0) { // The child process
close(listen_sock);
// close other child pipes
for (int i = 0; i < curr_client_no; i++) {
printf("Close pipe %d in child %d\n", i, curr_client_no);
// close(pipe_fds[i][0]);
close(pipe_fds[i][1]);
}
close(pipe_fds[curr_client_no][1]);
int exitVal = childProcess(ssl, sock, pipe_fds[curr_client_no][0], tunfd, curr_client_no); // returns on close, exits on fail.
printf("Client %d exited.\n", curr_client_no);
return exitVal;
} else { // The parent process
// child_pids[curr_client_no] = child_pid;
close(pipe_fds[curr_client_no][0]);
curr_client_no++;
close(sock);
continue;
}
}
if (FD_ISSET(tunfd, &readFDSet)) {
// We need to find out what child to send to, which means
// look at DST ip
// match (O(n)) with client_addrs
// We cannot figure out yet if a child exited, so addrs can't be reused without a full exit.
int ret = tunSelected(ssl, tunfd, client_addrs, curr_client_no, pipe_fds);
if (ret < 0) {
exit(1);
}
}
}
}