From 4638e0dfc3be720962990e5529587ee22d62f219 Mon Sep 17 00:00:00 2001 From: Dirk Engling Date: Fri, 4 Dec 2020 06:11:14 +0100 Subject: Server and client implementation for encrypted udp logger --- sender.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 sender.c (limited to 'sender.c') diff --git a/sender.c b/sender.c new file mode 100644 index 0000000..3469735 --- /dev/null +++ b/sender.c @@ -0,0 +1,110 @@ +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include "mbedtls/ctr_drbg.h" +#include "mbedtls/gcm.h" + +const unsigned short PORT = 58132; + +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[] = "IJUHZGFDXTZKHJKHGFDHZLUÖDRTFGHHJGHH"; + +enum { SESSION_ID_LENGTH = 8, AES_KEY_LENGTH = 16, GCM_IV_LENGTH = 16, GCM_TAG_LENGTH = 16 }; +static uint8_t session_id[8] = { 0xef, 0xcd, 0xab, 0x89, 0x67, 0x45, 0x23, 0x01 }; +static uint8_t aes_key[16] = { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef }; + +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, sizeof(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] = 1; + memcpy(output + 1, session_id, SESSION_ID_LENGTH); + memcpy(output + 1 + SESSION_ID_LENGTH, iv, GCM_IV_LENGTH); + + mbedtls_gcm_context ctx; + mbedtls_gcm_init(&ctx); + mbedtls_gcm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, aes_key, 8 * AES_KEY_LENGTH); + + if (!mbedtls_gcm_crypt_and_tag(&ctx, MBEDTLS_GCM_ENCRYPT, len, iv, GCM_IV_LENGTH, 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)) { + struct sockaddr_in to; + memset(&to, 0, sizeof(to)); + to.sin_family = AF_INET; + to.sin_addr.s_addr = inet_addr("127.0.0.1"); + to.sin_port = htons(PORT); + + sendto(sock, output, total_length, 0, (struct sockaddr*)&to, sizeof(to)); + } + + mbedtls_gcm_free(&ctx); +} + +void new_session(int sock, mbedtls_ctr_drbg_context *ctr_drbg) { + mbedtls_ctr_drbg_random(ctr_drbg, 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, session_id, SESSION_ID_LENGTH); + + mbedtls_pk_context pk; + mbedtls_pk_init(&pk); + int ret = 0; + 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); + + struct sockaddr_in to; + memset(&to, 0, sizeof(to)); + to.sin_family = AF_INET; + to.sin_addr.s_addr = inet_addr("127.0.0.1"); + to.sin_port = htons(PORT); + + sendto(sock, output, olen + 1 + SESSION_ID_LENGTH, 0, (struct sockaddr*)&to, sizeof(to)); +} + +int main() { + 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)); + + int sock = socket(AF_INET, SOCK_DGRAM, 0); + + new_session(sock, &ctr_drbg); + + sleep(3); + + const unsigned char *logline = (const unsigned char*)"Juchuuu, es klappt!\n"; + send_udp(sock, &ctr_drbg, logline, strlen((char*)logline)); + + close(sock); +} -- cgit v1.2.3