summaryrefslogtreecommitdiff
path: root/receiver.c
diff options
context:
space:
mode:
Diffstat (limited to 'receiver.c')
-rw-r--r--receiver.c298
1 files changed, 298 insertions, 0 deletions
diff --git a/receiver.c b/receiver.c
new file mode 100644
index 0000000..b7171d9
--- /dev/null
+++ b/receiver.c
@@ -0,0 +1,298 @@
1#include <regex.h>
2#include <string.h>
3#include <dirent.h>
4#include <err.h>
5#include <stdio.h>
6#include <inttypes.h>
7#include <fcntl.h>
8#include <unistd.h>
9#include <sys/socket.h>
10#include <netinet/in.h>
11
12#include <mbedtls/pk.h>
13#include <mbedtls/entropy.h>
14#include "mbedtls/ctr_drbg.h"
15#include "mbedtls/gcm.h"
16
17const unsigned short PORT = 58132;
18
19static const unsigned char privkey[] =
20"-----BEGIN RSA PRIVATE KEY-----\n"
21"MIIEpAIBAAKCAQEAwWlNmLHOOzZpdrfp+EAANwqab0FhQwCyZ/u+ySBW5XxPf6mo\n"
22"bySvtJrLdsWzdwnup/UfwZiEhJk/4wpD4Qf/2+syuJi3Rf7L+Jfh//Qf9uXAS80+\n"
23"LYad7dW0c1r5nt+F9Can5fBn7futnd8n672T+y8QpHRwX9GtaILvYQe5GQac8cfq\n"
24"2rGUd5iYj5KSdcaIZnJ4YgnjLHg2PMbtEJwqcV+2oAkcOPzTAJoNE7XjLZTwXmLl\n"
25"FgL/2cN4uJZBDnwv3RZSAhpdYF4KOJmE2GFs2jdvRUrYO7WSl8fM16vRH4vz5MNN\n"
26"caprg2MlXheVTPQa+WMdcz7dyQx8s9kRVPPUSwIDAQABAoIBAH1KD8A4flYRO2Ry\n"
27"YxgzrW/6aGxlt/HFg8ykYcS8NE5Yps8WQkwtQb0HAYKhM06LmpQm0DmC6WVUOPSE\n"
28"c9BUdEQsKiE2nJK1KcCR8w7xP7uavWTdQcgQCkJFS63mYwmt1oKAgAcOIuUhQiig\n"
29"pKWrmy7+IBPIcftAQssO9q6uaBNy+ONu6KU/FYd4UAoEt07MzuIAl5rybROOWCrA\n"
30"cjuOKK830Q2Mi2ESwwlO0+3Vyz9VhSha5wW2WwFv9zx8YQblaVXxfXC6O5XcXb0j\n"
31"O2rTpgHMmOVik3Zrg3XoRXsNZCvFQqbIevwGhRNEFQTnzakh/5g0VDa54RAK/APC\n"
32"t3ABEAECgYEA+rnqDqmXQc/xMCLOhJduxRFvZbT6EbUVJG5+l6XtATTa4LWzqx1B\n"
33"QDXS/Dixxc9FA1vSH2rAW//6wbr8KXihSeI7YxgIfWyrSIxbS3Dd1qwddvniYIpx\n"
34"ms9vYpQKAewv2p310nf7fyuURES8YikhpSuff3DhzXBEi7s3Y7gIIEsCgYEAxXrD\n"
35"6xjgLSgbbdyqxKeNk8ADMifbj8ZoiNIHkJ6sShFaTEbyHweOJ4RY7OmTBUDhgzUY\n"
36"1oynztilADFaq8KhsiMqzI3DgZ3/2OElGYReEAbXljvgudL3tmiBWc5j9S7XNLBe\n"
37"u9f3WYAYDu7/BVqmQWa/QtD9JquoZ1xgV2D6nAECgYEA29w9t9/VSJvM9xX+nNyi\n"
38"AON6GOjrRK3TPWA7WEXjH+S2bshHJi0ANAs+2Xfpw/kunnRdPLmCtuowfMO4LbGf\n"
39"VcexpgLEJyAszvBteikeDwpcyCD19wxP9J4kIYCJiggQKpfLoWUfP/P6DydrPnSt\n"
40"EUbAlaNqDpl9Mj7YonQVhCMCgYEAv0c9M5+hrDuX7d76zYaZvI4UymUO54E/yZ7e\n"
41"UvdOXGPYed+SL/oKeD5aQAeyLzl79bHdgBs3g0QW9kvXzly0cC5eC0oZH5hhs7nI\n"
42"TKII1i86bLtM3dD5vQYWnF0sNtWK/+8Bo6L5ZAiNxRE7lP0L4ndaNKbnPaixcoRo\n"
43"kNpPhAECgYAg7jmNlw+7VVurzR36LKKE+d6veraF5ltpJiboDb3j38RGe3982LLq\n"
44"WaBKm1gkHfXgBjkNzS4r2kyRijw0GQ9JgmWooR7BXFH30HkPNl4gFTSsrOG5zGLi\n"
45"0aexkDpXQuKsgBzqU0Wn94GZMM+RhuOYec/56JFT+8U5Tcntb26wwA==\n"
46"-----END RSA PRIVATE KEY-----\n";
47
48static const unsigned char pp[] = "IJUHZGFDXTZKHJKHGFDHZLUÖDRTFGHHJGHH";
49
50/*
51 1 byte type: 0 allocate session, 1 log to session, rest: discard
52 8 bytes session id
53 type 0:
54 256 bytes rsa 2048 data yielding 32 byte AES session key
55 type 1:
56 16 bytes iv
57 16 bytes tag
58 rest cipher text
59
60 File name format: 2020-10-13-23-42-05-SSSSSSSSSSSSSSSS-KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK.log
61
62*/
63
64enum { SESSION_ID_LENGTH = 8, AES_KEY_LENGTH = 16, GCM_IV_LENGTH = 16, GCM_TAG_LENGTH = 16 };
65typedef struct {
66 uint8_t session_id[SESSION_ID_LENGTH];
67 uint8_t key[AES_KEY_LENGTH];
68 int fd; // or -1 if not existing
69 time_t last_access;
70 char file_name[80];
71} SESSION;
72static SESSION *g_sessions = 0;
73static size_t g_session_count = 0;
74
75int session_compare(const void *a, const void *b) { return memcmp(a, b, 8); }
76
77enum { SIDOFFS = 20, KEYOFFS = 37, };
78
79static uint8_t hex2nyble(char c)
80{
81 return (c>='0'&&c<='9') ? (uint8_t)(c-'0')
82 : (c>='a'&&c<='f') ? (uint8_t)(c-'a'+10)
83 : (c>='A'&&c<='F') ? (uint8_t)(c-'A'+10)
84 : 0;
85}
86
87static void import_sessions(const char *dirname) {
88 DIR * dirp = opendir(dirname);
89 if (!dirp)
90 errx(-1, "Fatal: Can't open dir %s\n", dirname);
91
92 free(g_sessions);
93 g_session_count = 0;
94
95 size_t allocated = 1024;
96 g_sessions = malloc(allocated * sizeof(SESSION));
97 if (!g_sessions)
98 errx(-1, "Fatal: Out of memory");
99
100 regex_t regex;
101 if (regcomp(&regex, "^[[:digit:]]{4}-[[:digit:]][[:digit:]]-[[:digit:]][[:digit:]]-[[:digit:]][[:digit:]]-[[:digit:]][[:digit:]]-"
102 "[[:digit:]][[:digit:]]-[[:xdigit:]]{16}-[[:xdigit:]]{32}.log$", REG_EXTENDED))
103 errx(-1, "Fatal: Can't compile re");
104
105 struct dirent * entry;
106 while ((entry = readdir(dirp)) != NULL) {
107 // We expect a very specific format
108 if (entry->d_type != DT_REG || entry->d_namlen != 73) {
109 fprintf(stderr, "Skipping wrong length file: %*s\n", entry->d_namlen, entry->d_name);
110 continue;
111 }
112
113 SESSION *ns = g_sessions + g_session_count;
114
115 memcpy(ns->file_name, entry->d_name, entry->d_namlen);
116 ns->file_name[entry->d_namlen] = 0;
117 ns->fd = -1;
118 ns->last_access = 0;
119
120 if (regexec(&regex, ns->file_name, (size_t) 0, NULL, 0)) {
121 fprintf(stderr, "Skipping non-re-matching file: %s\n", ns->file_name);
122 continue;
123 }
124
125 if (sscanf(ns->file_name + SIDOFFS, "%" SCNx64, (uint64_t*)&ns->session_id) != 1) {
126 fprintf(stderr, "Skipping non-parsable file: %s\n", ns->file_name);
127 continue;
128 }
129 const char * hexkey = ns->file_name + KEYOFFS;
130 for (int i=0; i<16; ++i)
131 ns->key[i] = (hex2nyble(hexkey[2*i]) << 4 ) | hex2nyble(hexkey[2*i+1]);
132
133 // Need more memory?
134 if (++g_session_count > allocated) {
135 allocated += 1024;
136 g_sessions = realloc(g_sessions, allocated * sizeof(SESSION));
137 if (!g_sessions)
138 errx(-1, "Fatal: Out of memory");
139 }
140 }
141 closedir(dirp);
142 regfree(&regex);
143
144 qsort(g_sessions, g_session_count, sizeof(SESSION), session_compare);
145}
146
147static void add_session(uint8_t *session_id, uint8_t aes_key[AES_KEY_LENGTH]) {
148 // We don't overwrite existing sessions
149 if (bsearch(session_id, g_sessions, g_session_count, sizeof(SESSION), session_compare))
150 return;
151
152 SESSION * sessions_realloc = realloc(g_sessions, sizeof(SESSION) * (1 + g_session_count));
153
154 if (!sessions_realloc)
155 errx(-1, "Fatal: Out of memory");
156
157 g_sessions = sessions_realloc;
158 SESSION * new_session = &g_sessions[g_session_count];
159 g_session_count++;
160
161 memcpy(new_session->session_id, session_id, SESSION_ID_LENGTH);
162 memcpy(new_session->key, aes_key, AES_KEY_LENGTH);
163 new_session->fd = -1;
164 new_session->last_access = 0;
165
166 time_t t = time(NULL);
167 struct tm * jetzt = localtime(&t);
168 char tprefix[32], hexkey[2*AES_KEY_LENGTH + 1];
169 size_t nlen = strftime(tprefix, sizeof(tprefix), "%F-%H-%M-%S", jetzt);
170 for (int i=0; i<AES_KEY_LENGTH; ++i)
171 sprintf(hexkey + 2 * i, "%02x", aes_key[i]);
172 int off = snprintf(new_session->file_name, sizeof(new_session->file_name),
173 "%s-%" PRIx64 "-%s.log", tprefix, *(uint64_t*)session_id, hexkey);
174 int fd = open("new_session->file_name", O_RDWR|O_CREAT, 0755);
175 close(fd);
176
177 mergesort(g_sessions, g_session_count, sizeof(SESSION), session_compare);
178}
179
180static time_t now() {
181 struct timespec tp;
182 clock_gettime(CLOCK_MONOTONIC, &tp);
183 return tp.tv_sec;
184}
185
186static void log_to_session(const uint8_t *packet, size_t len) {
187 // First check if the packet holds enough space for session id, iv and at least one gcm block
188 if (len < SESSION_ID_LENGTH + GCM_IV_LENGTH + GCM_TAG_LENGTH) {
189 fprintf(stderr, "Error: Short packet, size %zd\n", len);
190 return;
191 }
192
193 const uint8_t *session_id = packet;
194 const uint8_t *iv = packet + SESSION_ID_LENGTH;
195 const uint8_t *tag = packet + SESSION_ID_LENGTH + GCM_IV_LENGTH;
196 packet += SESSION_ID_LENGTH + GCM_IV_LENGTH + GCM_TAG_LENGTH;
197 len -= SESSION_ID_LENGTH + GCM_IV_LENGTH + GCM_TAG_LENGTH;
198
199 SESSION * s = bsearch(session_id, g_sessions, g_session_count, sizeof(SESSION), session_compare);
200 if (!s) {
201 fprintf(stderr, "Error: Can't log to unknown session 0x%" PRIx64 "\n", *(uint64_t*)session_id);
202 return;
203 }
204
205 // Create output file if it doesn't exist
206 if (s->fd < 0)
207 s->fd = open(s->file_name, O_WRONLY | O_APPEND | O_CREAT, 0755);
208 if (s->fd < 0) {
209 fprintf(stderr, "Error: Can't create file %s for session 0x%" PRIx64 "\n", s->file_name, *(uint64_t*)packet);
210 return;
211 }
212
213 // Now decrypt
214 mbedtls_gcm_context ctx;
215 mbedtls_gcm_init(&ctx);
216 mbedtls_gcm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, s->key, 8 * AES_KEY_LENGTH);
217
218 // Prepare output scratch space
219 uint8_t *output = alloca(len);
220
221 // This should fail on invalid input sizes
222 switch(mbedtls_gcm_auth_decrypt(&ctx, len, iv, GCM_IV_LENGTH, session_id, SESSION_ID_LENGTH, tag, GCM_TAG_LENGTH, packet, output))
223 {
224 case 0:
225 write(s->fd, output, len);
226 s->last_access = now();
227 break;
228 case MBEDTLS_ERR_GCM_BAD_INPUT:
229 fprintf(stderr, "Error: Invalid log data\n");
230 break;
231 case MBEDTLS_ERR_GCM_AUTH_FAILED :
232 fprintf(stderr, "Error: Can't decrypt\n");
233 break;
234 default:
235 fprintf(stderr, "Error: Unknown gcm error\n");
236 }
237
238 mbedtls_gcm_free(&ctx);
239}
240
241int main() {
242 mbedtls_ctr_drbg_context ctr_drbg;
243 mbedtls_entropy_context entropy;
244 mbedtls_pk_context pk;
245 int ret = 0;
246 unsigned char result[256];
247 unsigned char input[256];
248 size_t inputlen = 0;
249
250 chdir("sessions");
251
252 mbedtls_pk_init( &pk );
253 mbedtls_entropy_init( &entropy );
254 mbedtls_ctr_drbg_init( &ctr_drbg );
255 mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy, pp, sizeof(pp));
256
257 if ((ret = mbedtls_pk_parse_key(&pk, privkey, sizeof(privkey), NULL, 0) ) != 0 )
258 errx(-1, "Fatal: mbedtls_pk_parse_key returned -0x%04x\n", -ret );
259
260 int sock = socket(AF_INET, SOCK_DGRAM, 0);
261 if (sock < 0)
262 errx(-1, "Fatal: Can not make socket\n");
263
264 struct sockaddr_in servaddr, peer;
265 servaddr.sin_family = AF_INET;
266 servaddr.sin_addr.s_addr = INADDR_ANY;
267 servaddr.sin_port = htons(PORT);
268 if (bind(sock, (const struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)
269 errx(-1, "Fatal: Can't bind to port %d\n", PORT);
270
271 import_sessions(".");
272
273 while(1) {
274 uint8_t packet[16*1024];
275 uint8_t rsa_plain_text[AES_KEY_LENGTH];
276 size_t olen;
277 socklen_t peer_len = sizeof(peer);
278
279 ssize_t len = recvfrom(sock, packet, sizeof(packet), MSG_WAITALL, (struct sockaddr *) &peer, &peer_len);
280 if (len <= 0)
281 errx(-1, "Fatal: recvfrom yields %zd\n", len);
282 switch(packet[0]) {
283 case 0: // Session setup
284 ret = mbedtls_pk_decrypt(&pk, packet + 1 + SESSION_ID_LENGTH, len - 1 - SESSION_ID_LENGTH,
285 rsa_plain_text, &olen, sizeof(rsa_plain_text), mbedtls_ctr_drbg_random, &ctr_drbg);
286 if (ret < 0)
287 fprintf(stderr, "Error: Failed to decrypt key (error %d) for session 0x%" PRIx64 "\n", -ret, *(uint64_t *)(packet + 1));
288 else
289 add_session(packet + 1, rsa_plain_text);
290 break;
291 case 1:
292 log_to_session(packet + 1, len - 1);
293 break;
294 default:
295 break;
296 }
297 }
298}