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-rw-r--r--sender.c110
1 files changed, 110 insertions, 0 deletions
diff --git a/sender.c b/sender.c
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1#include <sys/socket.h>
2#include <netinet/in.h>
3#include <string.h>
4#include <err.h>
5#include <inttypes.h>
6#include <arpa/inet.h>
7#include <unistd.h>
8
9#include <mbedtls/pk.h>
10#include <mbedtls/entropy.h>
11#include "mbedtls/ctr_drbg.h"
12#include "mbedtls/gcm.h"
13
14const unsigned short PORT = 58132;
15
16static const unsigned char pubkey[] =
17"-----BEGIN PUBLIC KEY-----\n"
18"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwWlNmLHOOzZpdrfp+EAA\n"
19"Nwqab0FhQwCyZ/u+ySBW5XxPf6mobySvtJrLdsWzdwnup/UfwZiEhJk/4wpD4Qf/\n"
20"2+syuJi3Rf7L+Jfh//Qf9uXAS80+LYad7dW0c1r5nt+F9Can5fBn7futnd8n672T\n"
21"+y8QpHRwX9GtaILvYQe5GQac8cfq2rGUd5iYj5KSdcaIZnJ4YgnjLHg2PMbtEJwq\n"
22"cV+2oAkcOPzTAJoNE7XjLZTwXmLlFgL/2cN4uJZBDnwv3RZSAhpdYF4KOJmE2GFs\n"
23"2jdvRUrYO7WSl8fM16vRH4vz5MNNcaprg2MlXheVTPQa+WMdcz7dyQx8s9kRVPPU\n"
24"SwIDAQAB \n"
25"-----END PUBLIC KEY----- \n";
26
27static const unsigned char pp[] = "IJUHZGFDXTZKHJKHGFDHZLUÖDRTFGHHJGHH";
28
29enum { SESSION_ID_LENGTH = 8, AES_KEY_LENGTH = 16, GCM_IV_LENGTH = 16, GCM_TAG_LENGTH = 16 };
30static uint8_t session_id[8] = { 0xef, 0xcd, 0xab, 0x89, 0x67, 0x45, 0x23, 0x01 };
31static uint8_t aes_key[16] = { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef };
32
33void send_udp(int sock, mbedtls_ctr_drbg_context *ctr_drbg, const uint8_t *text, size_t len) {
34 uint8_t iv[GCM_IV_LENGTH];
35 mbedtls_ctr_drbg_random(ctr_drbg, iv, sizeof(GCM_IV_LENGTH));
36
37 const size_t total_length = 1 + SESSION_ID_LENGTH + GCM_IV_LENGTH + GCM_TAG_LENGTH + len;
38 uint8_t *output = alloca(total_length);
39 output[0] = 1;
40 memcpy(output + 1, session_id, SESSION_ID_LENGTH);
41 memcpy(output + 1 + SESSION_ID_LENGTH, iv, GCM_IV_LENGTH);
42
43 mbedtls_gcm_context ctx;
44 mbedtls_gcm_init(&ctx);
45 mbedtls_gcm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, aes_key, 8 * AES_KEY_LENGTH);
46
47 if (!mbedtls_gcm_crypt_and_tag(&ctx, MBEDTLS_GCM_ENCRYPT, len, iv, GCM_IV_LENGTH, session_id, SESSION_ID_LENGTH,
48 text, output + 1 + SESSION_ID_LENGTH + GCM_IV_LENGTH + GCM_TAG_LENGTH, GCM_TAG_LENGTH,
49 output + 1 + SESSION_ID_LENGTH + GCM_IV_LENGTH)) {
50 struct sockaddr_in to;
51 memset(&to, 0, sizeof(to));
52 to.sin_family = AF_INET;
53 to.sin_addr.s_addr = inet_addr("127.0.0.1");
54 to.sin_port = htons(PORT);
55
56 sendto(sock, output, total_length, 0, (struct sockaddr*)&to, sizeof(to));
57 }
58
59 mbedtls_gcm_free(&ctx);
60}
61
62void new_session(int sock, mbedtls_ctr_drbg_context *ctr_drbg) {
63 mbedtls_ctr_drbg_random(ctr_drbg, session_id, sizeof(session_id));
64 mbedtls_ctr_drbg_random(ctr_drbg, aes_key, sizeof(aes_key));
65
66 unsigned char output[512];
67 output[0] = 0;
68 memcpy(output + 1, session_id, SESSION_ID_LENGTH);
69
70 mbedtls_pk_context pk;
71 mbedtls_pk_init(&pk);
72 int ret = 0;
73 if ((ret = mbedtls_pk_parse_public_key(&pk, pubkey, sizeof(pubkey)) ) != 0 )
74 errx(-1, "mbedtls_pk_parse_public_keyfile returned -0x%04x\n", -ret );
75
76 size_t olen = 0;
77 if ((ret = mbedtls_pk_encrypt(&pk, aes_key, AES_KEY_LENGTH, output + 1 + SESSION_ID_LENGTH, &olen,
78 sizeof(output) - 1 - SESSION_ID_LENGTH, mbedtls_ctr_drbg_random, ctr_drbg)) != 0)
79 errx(-1, "mbedtls_pk_encrypt returned -0x%04x\n", -ret );
80
81 mbedtls_pk_free(&pk);
82
83 struct sockaddr_in to;
84 memset(&to, 0, sizeof(to));
85 to.sin_family = AF_INET;
86 to.sin_addr.s_addr = inet_addr("127.0.0.1");
87 to.sin_port = htons(PORT);
88
89 sendto(sock, output, olen + 1 + SESSION_ID_LENGTH, 0, (struct sockaddr*)&to, sizeof(to));
90}
91
92int main() {
93 mbedtls_ctr_drbg_context ctr_drbg;
94 mbedtls_entropy_context entropy;
95
96 mbedtls_entropy_init(&entropy);
97 mbedtls_ctr_drbg_init(&ctr_drbg);
98 mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy, pp, sizeof(pp));
99
100 int sock = socket(AF_INET, SOCK_DGRAM, 0);
101
102 new_session(sock, &ctr_drbg);
103
104 sleep(3);
105
106 const unsigned char *logline = (const unsigned char*)"Juchuuu, es klappt!\n";
107 send_udp(sock, &ctr_drbg, logline, strlen((char*)logline));
108
109 close(sock);
110}