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#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <err.h>
#include <inttypes.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <netdb.h>
#include <mbedtls/pk.h>
#include <mbedtls/entropy.h>
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/gcm.h"
static const unsigned char pubkey[] =
"-----BEGIN PUBLIC KEY-----\n"
"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwWlNmLHOOzZpdrfp+EAA\n"
"Nwqab0FhQwCyZ/u+ySBW5XxPf6mobySvtJrLdsWzdwnup/UfwZiEhJk/4wpD4Qf/\n"
"2+syuJi3Rf7L+Jfh//Qf9uXAS80+LYad7dW0c1r5nt+F9Can5fBn7futnd8n672T\n"
"+y8QpHRwX9GtaILvYQe5GQac8cfq2rGUd5iYj5KSdcaIZnJ4YgnjLHg2PMbtEJwq\n"
"cV+2oAkcOPzTAJoNE7XjLZTwXmLlFgL/2cN4uJZBDnwv3RZSAhpdYF4KOJmE2GFs\n"
"2jdvRUrYO7WSl8fM16vRH4vz5MNNcaprg2MlXheVTPQa+WMdcz7dyQx8s9kRVPPU\n"
"SwIDAQAB \n"
"-----END PUBLIC KEY----- \n";
static const unsigned char pp[] = "9bf308b7ae027baa46091d980632e27b";
static const char *logging_host = "endpoint-de9XDJ0fH7.gsmk.de";
static const char *logging_port = "8238";
static struct sockaddr_storage logging_host_address;
static socklen_t logging_host_address_len = 0;
static int logging_socket = -1;
typedef uint64_t SessionId_t;
enum { SESSION_ID_LENGTH = 8, AES_KEY_LENGTH = 16, GCM_IV_LENGTH = 12, GCM_TAG_LENGTH = 16 };
static SessionId_t session_id;
static uint8_t aes_key[16];
static mbedtls_gcm_context ctx;
void send_udp(int sock, mbedtls_ctr_drbg_context *ctr_drbg, const uint8_t *text, size_t len) {
uint8_t iv[GCM_IV_LENGTH];
mbedtls_ctr_drbg_random(ctr_drbg, iv, GCM_IV_LENGTH);
const size_t total_length = 1 + SESSION_ID_LENGTH + GCM_IV_LENGTH + GCM_TAG_LENGTH + len;
uint8_t *output = alloca(total_length);
output[0] = 2;
memcpy(output + 1, (uint8_t*)&session_id, SESSION_ID_LENGTH);
memcpy(output + 1 + SESSION_ID_LENGTH, iv, GCM_IV_LENGTH);
if (!mbedtls_gcm_crypt_and_tag(&ctx, MBEDTLS_GCM_ENCRYPT, len, iv, GCM_IV_LENGTH, (uint8_t*)&session_id, SESSION_ID_LENGTH,
text, output + 1 + SESSION_ID_LENGTH + GCM_IV_LENGTH + GCM_TAG_LENGTH, GCM_TAG_LENGTH,
output + 1 + SESSION_ID_LENGTH + GCM_IV_LENGTH)) {
sendto(sock, output, total_length, 0, (struct sockaddr*)&logging_host_address, logging_host_address_len);
}
}
void new_session(int sock, mbedtls_ctr_drbg_context *ctr_drbg) {
mbedtls_ctr_drbg_random(ctr_drbg, (uint8_t*)&session_id, sizeof(session_id));
mbedtls_ctr_drbg_random(ctr_drbg, aes_key, sizeof(aes_key));
unsigned char output[512];
output[0] = 0;
memcpy(output + 1, (uint8_t*)&session_id, SESSION_ID_LENGTH);
mbedtls_pk_context pk;
mbedtls_pk_init(&pk);
int ret = 0;
printf("%zd\n", sizeof(pubkey));
if ((ret = mbedtls_pk_parse_public_key(&pk, pubkey, sizeof(pubkey)) ) != 0 )
errx(-1, "mbedtls_pk_parse_public_keyfile returned -0x%04x\n", -ret );
size_t olen = 0;
if ((ret = mbedtls_pk_encrypt(&pk, aes_key, AES_KEY_LENGTH, output + 1 + SESSION_ID_LENGTH, &olen,
sizeof(output) - 1 - SESSION_ID_LENGTH, mbedtls_ctr_drbg_random, ctr_drbg)) != 0)
errx(-1, "mbedtls_pk_encrypt returned -0x%04x\n", -ret );
mbedtls_pk_free(&pk);
sendto(sock, output, olen + 1 + SESSION_ID_LENGTH, 0, (struct sockaddr*)&logging_host_address, logging_host_address_len);
mbedtls_gcm_init(&ctx);
mbedtls_gcm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, aes_key, 8 * AES_KEY_LENGTH);
}
int main() {
struct addrinfo hints, *result, *rp;
memset (&hints, 0, sizeof (hints));
hints.ai_socktype = SOCK_DGRAM;
int sock = -1, res = getaddrinfo(logging_host, logging_port, &hints, &result);
if (res != 0)
errx(EXIT_FAILURE, "getaddrinfo: %s\n", gai_strerror(res));
for (rp = result; rp != NULL; rp = rp->ai_next) {
sock = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
if (sock == -1)
continue;
memcpy(&logging_host_address, rp->ai_addr, rp->ai_addrlen);
logging_host_address_len = rp->ai_addrlen;
}
if (sock == -1)
errx(EXIT_FAILURE, "Can't open socket");
freeaddrinfo(result);
// Setup
mbedtls_ctr_drbg_context ctr_drbg;
mbedtls_entropy_context entropy;
mbedtls_entropy_init(&entropy);
mbedtls_ctr_drbg_init(&ctr_drbg);
mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy, pp, sizeof(pp));
new_session(sock, &ctr_drbg);
sleep(3);
// Fire
const unsigned char *logline = (const unsigned char*)"Juchuuu, es klappt!\n";
send_udp(sock, &ctr_drbg, logline, strlen((char*)logline));
send_udp(sock, &ctr_drbg, logline, strlen((char*)logline));
send_udp(sock, &ctr_drbg, logline, strlen((char*)logline));
mbedtls_gcm_free(&ctx);
close(sock);
}
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