Previous: Echo server with X.509 authentication, Up: Server examples [Contents][Index]
This example is a very simple echo server using Datagram TLS and X.509 authentication.
/* This example code is placed in the public domain. */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/select.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include <gnutls/gnutls.h>
#include <gnutls/dtls.h>
#define KEYFILE "key.pem"
#define CERTFILE "cert.pem"
#define CAFILE "/etc/ssl/certs/ca-certificates.crt"
#define CRLFILE "crl.pem"
/* This is a sample DTLS echo server, using X.509 authentication.
* Note that error checking is minimal to simplify the example.
*/
#define LOOP_CHECK(rval, cmd) \
do { \
rval = cmd; \
} while (rval == GNUTLS_E_AGAIN || rval == GNUTLS_E_INTERRUPTED)
#define MAX_BUFFER 1024
#define PORT 5557
typedef struct {
gnutls_session_t session;
int fd;
struct sockaddr *cli_addr;
socklen_t cli_addr_size;
} priv_data_st;
static int pull_timeout_func(gnutls_transport_ptr_t ptr, unsigned int ms);
static ssize_t push_func(gnutls_transport_ptr_t p, const void *data,
size_t size);
static ssize_t pull_func(gnutls_transport_ptr_t p, void *data, size_t size);
static const char *human_addr(const struct sockaddr *sa, socklen_t salen,
char *buf, size_t buflen);
static int wait_for_connection(int fd);
/* Use global credentials and parameters to simplify
* the example. */
static gnutls_certificate_credentials_t x509_cred;
static gnutls_priority_t priority_cache;
int main(void)
{
int listen_sd;
int sock, ret;
struct sockaddr_in sa_serv;
struct sockaddr_in cli_addr;
socklen_t cli_addr_size;
gnutls_session_t session;
char buffer[MAX_BUFFER];
priv_data_st priv;
gnutls_datum_t cookie_key;
gnutls_dtls_prestate_st prestate;
int mtu = 1400;
unsigned char sequence[8];
/* this must be called once in the program
*/
gnutls_global_init();
gnutls_certificate_allocate_credentials(&x509_cred);
gnutls_certificate_set_x509_trust_file(x509_cred, CAFILE,
GNUTLS_X509_FMT_PEM);
gnutls_certificate_set_x509_crl_file(x509_cred, CRLFILE,
GNUTLS_X509_FMT_PEM);
ret = gnutls_certificate_set_x509_key_file(x509_cred, CERTFILE, KEYFILE,
GNUTLS_X509_FMT_PEM);
if (ret < 0) {
printf("No certificate or key were found\n");
exit(1);
}
gnutls_certificate_set_known_dh_params(x509_cred,
GNUTLS_SEC_PARAM_MEDIUM);
/* pre-3.6.3 equivalent:
* gnutls_priority_init(&priority_cache,
* "NORMAL:-VERS-TLS-ALL:+VERS-DTLS1.0:%SERVER_PRECEDENCE",
* NULL);
*/
gnutls_priority_init2(&priority_cache, "%SERVER_PRECEDENCE", NULL,
GNUTLS_PRIORITY_INIT_DEF_APPEND);
gnutls_key_generate(&cookie_key, GNUTLS_COOKIE_KEY_SIZE);
/* Socket operations
*/
listen_sd = socket(AF_INET, SOCK_DGRAM, 0);
memset(&sa_serv, '\0', sizeof(sa_serv));
sa_serv.sin_family = AF_INET;
sa_serv.sin_addr.s_addr = INADDR_ANY;
sa_serv.sin_port = htons(PORT);
{ /* DTLS requires the IP don't fragment (DF) bit to be set */
#if defined(IP_DONTFRAG)
int optval = 1;
setsockopt(listen_sd, IPPROTO_IP, IP_DONTFRAG,
(const void *)&optval, sizeof(optval));
#elif defined(IP_MTU_DISCOVER)
int optval = IP_PMTUDISC_DO;
setsockopt(listen_sd, IPPROTO_IP, IP_MTU_DISCOVER,
(const void *)&optval, sizeof(optval));
#endif
}
bind(listen_sd, (struct sockaddr *)&sa_serv, sizeof(sa_serv));
printf("UDP server ready. Listening to port '%d'.\n\n", PORT);
for (;;) {
printf("Waiting for connection...\n");
sock = wait_for_connection(listen_sd);
if (sock < 0)
continue;
cli_addr_size = sizeof(cli_addr);
ret = recvfrom(sock, buffer, sizeof(buffer), MSG_PEEK,
(struct sockaddr *)&cli_addr, &cli_addr_size);
if (ret > 0) {
memset(&prestate, 0, sizeof(prestate));
ret = gnutls_dtls_cookie_verify(&cookie_key, &cli_addr,
sizeof(cli_addr),
buffer, ret, &prestate);
if (ret < 0) { /* cookie not valid */
priv_data_st s;
memset(&s, 0, sizeof(s));
s.fd = sock;
s.cli_addr = (void *)&cli_addr;
s.cli_addr_size = sizeof(cli_addr);
printf("Sending hello verify request to %s\n",
human_addr((struct sockaddr *)&cli_addr,
sizeof(cli_addr), buffer,
sizeof(buffer)));
gnutls_dtls_cookie_send(
&cookie_key, &cli_addr,
sizeof(cli_addr), &prestate,
(gnutls_transport_ptr_t)&s, push_func);
/* discard peeked data */
recvfrom(sock, buffer, sizeof(buffer), 0,
(struct sockaddr *)&cli_addr,
&cli_addr_size);
usleep(100);
continue;
}
printf("Accepted connection from %s\n",
human_addr((struct sockaddr *)&cli_addr,
sizeof(cli_addr), buffer,
sizeof(buffer)));
} else
continue;
gnutls_init(&session, GNUTLS_SERVER | GNUTLS_DATAGRAM);
gnutls_priority_set(session, priority_cache);
gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE,
x509_cred);
gnutls_dtls_prestate_set(session, &prestate);
gnutls_dtls_set_mtu(session, mtu);
priv.session = session;
priv.fd = sock;
priv.cli_addr = (struct sockaddr *)&cli_addr;
priv.cli_addr_size = sizeof(cli_addr);
gnutls_transport_set_ptr(session, &priv);
gnutls_transport_set_push_function(session, push_func);
gnutls_transport_set_pull_function(session, pull_func);
gnutls_transport_set_pull_timeout_function(session,
pull_timeout_func);
LOOP_CHECK(ret, gnutls_handshake(session));
/* Note that DTLS may also receive GNUTLS_E_LARGE_PACKET.
* In that case the MTU should be adjusted.
*/
if (ret < 0) {
fprintf(stderr, "Error in handshake(): %s\n",
gnutls_strerror(ret));
gnutls_deinit(session);
continue;
}
printf("- Handshake was completed\n");
for (;;) {
LOOP_CHECK(ret, gnutls_record_recv_seq(session, buffer,
MAX_BUFFER,
sequence));
if (ret < 0 && gnutls_error_is_fatal(ret) == 0) {
fprintf(stderr, "*** Warning: %s\n",
gnutls_strerror(ret));
continue;
} else if (ret < 0) {
fprintf(stderr, "Error in recv(): %s\n",
gnutls_strerror(ret));
break;
}
if (ret == 0) {
printf("EOF\n\n");
break;
}
buffer[ret] = 0;
printf("received[%.2x%.2x%.2x%.2x%.2x%.2x%.2x%.2x]: %s\n",
sequence[0], sequence[1], sequence[2],
sequence[3], sequence[4], sequence[5],
sequence[6], sequence[7], buffer);
/* reply back */
LOOP_CHECK(ret,
gnutls_record_send(session, buffer, ret));
if (ret < 0) {
fprintf(stderr, "Error in send(): %s\n",
gnutls_strerror(ret));
break;
}
}
LOOP_CHECK(ret, gnutls_bye(session, GNUTLS_SHUT_WR));
gnutls_deinit(session);
}
close(listen_sd);
gnutls_certificate_free_credentials(x509_cred);
gnutls_priority_deinit(priority_cache);
gnutls_global_deinit();
return 0;
}
static int wait_for_connection(int fd)
{
fd_set rd, wr;
int n;
FD_ZERO(&rd);
FD_ZERO(&wr);
FD_SET(fd, &rd);
/* waiting part */
n = select(fd + 1, &rd, &wr, NULL, NULL);
if (n == -1 && errno == EINTR)
return -1;
if (n < 0) {
perror("select()");
exit(1);
}
return fd;
}
/* Wait for data to be received within a timeout period in milliseconds
*/
static int pull_timeout_func(gnutls_transport_ptr_t ptr, unsigned int ms)
{
fd_set rfds;
struct timeval tv;
priv_data_st *priv = ptr;
struct sockaddr_in cli_addr;
socklen_t cli_addr_size;
int ret;
char c;
FD_ZERO(&rfds);
FD_SET(priv->fd, &rfds);
tv.tv_sec = ms / 1000;
tv.tv_usec = (ms % 1000) * 1000;
ret = select(priv->fd + 1, &rfds, NULL, NULL, &tv);
if (ret <= 0)
return ret;
/* only report ok if the next message is from the peer we expect
* from
*/
cli_addr_size = sizeof(cli_addr);
ret = recvfrom(priv->fd, &c, 1, MSG_PEEK, (struct sockaddr *)&cli_addr,
&cli_addr_size);
if (ret > 0) {
if (cli_addr_size == priv->cli_addr_size &&
memcmp(&cli_addr, priv->cli_addr, sizeof(cli_addr)) == 0)
return 1;
}
return 0;
}
static ssize_t push_func(gnutls_transport_ptr_t p, const void *data,
size_t size)
{
priv_data_st *priv = p;
return sendto(priv->fd, data, size, 0, priv->cli_addr,
priv->cli_addr_size);
}
static ssize_t pull_func(gnutls_transport_ptr_t p, void *data, size_t size)
{
priv_data_st *priv = p;
struct sockaddr_in cli_addr;
socklen_t cli_addr_size;
char buffer[64];
int ret;
cli_addr_size = sizeof(cli_addr);
ret = recvfrom(priv->fd, data, size, 0, (struct sockaddr *)&cli_addr,
&cli_addr_size);
if (ret == -1)
return ret;
if (cli_addr_size == priv->cli_addr_size &&
memcmp(&cli_addr, priv->cli_addr, sizeof(cli_addr)) == 0)
return ret;
printf("Denied connection from %s\n",
human_addr((struct sockaddr *)&cli_addr, sizeof(cli_addr),
buffer, sizeof(buffer)));
gnutls_transport_set_errno(priv->session, EAGAIN);
return -1;
}
static const char *human_addr(const struct sockaddr *sa, socklen_t salen,
char *buf, size_t buflen)
{
const char *save_buf = buf;
size_t l;
if (!buf || !buflen)
return NULL;
*buf = '\0';
switch (sa->sa_family) {
#if HAVE_IPV6
case AF_INET6:
snprintf(buf, buflen, "IPv6 ");
break;
#endif
case AF_INET:
snprintf(buf, buflen, "IPv4 ");
break;
}
l = strlen(buf);
buf += l;
buflen -= l;
if (getnameinfo(sa, salen, buf, buflen, NULL, 0, NI_NUMERICHOST) != 0)
return NULL;
l = strlen(buf);
buf += l;
buflen -= l;
strncat(buf, " port ", buflen);
l = strlen(buf);
buf += l;
buflen -= l;
if (getnameinfo(sa, salen, NULL, 0, buf, buflen, NI_NUMERICSERV) != 0)
return NULL;
return save_buf;
}
Previous: Echo server with X.509 authentication, Up: Server examples [Contents][Index]