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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: crypt.c,v 1.2 1997/08/04 10:24:21 mdw Exp $ |
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4 | * |
5 | * Cryptographic transfer of `become' requests |
6 | * |
7 | * (c) 1997 EBI |
8 | */ |
9 | |
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10 | /*----- Licensing notice --------------------------------------------------* |
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11 | * |
12 | * This file is part of `become' |
13 | * |
14 | * `Become' is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * `Become' is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
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25 | * along with `become'; if not, write to the Free Software Foundation, |
26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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27 | */ |
28 | |
29 | /*----- Revision history --------------------------------------------------* |
30 | * |
31 | * $Log: crypt.c,v $ |
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32 | * Revision 1.2 1997/08/04 10:24:21 mdw |
33 | * Sources placed under CVS control. |
34 | * |
35 | * Revision 1.1 1997/07/21 13:47:51 mdw |
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36 | * Initial revision |
37 | * |
38 | */ |
39 | |
40 | /*----- Header files ------------------------------------------------------*/ |
41 | |
42 | /* --- ANSI headers --- */ |
43 | |
44 | #include <ctype.h> |
45 | #include <errno.h> |
46 | #include <stdio.h> |
47 | #include <stdlib.h> |
48 | #include <string.h> |
49 | #include <time.h> |
50 | |
51 | /* --- Unix headers --- */ |
52 | |
53 | #include <sys/types.h> |
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54 | #include <sys/time.h> |
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55 | #include <unistd.h> |
56 | #include <syslog.h> |
57 | #include <fcntl.h> |
58 | |
59 | /* --- Local headers --- */ |
60 | |
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61 | #include "become.h" |
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62 | #include "config.h" |
63 | #include "crypt.h" |
64 | #include "icrypt.h" |
65 | #include "idea.h" |
66 | #include "md5.h" |
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67 | #include "noise.h" |
68 | #include "rand.h" |
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69 | #include "tx.h" |
70 | #include "utils.h" |
71 | |
72 | /*----- Magic numbers -----------------------------------------------------*/ |
73 | |
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74 | #define crypt__timeError 60 /* Seconds error to permit */ |
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75 | |
76 | /*----- Main code ---------------------------------------------------------*/ |
77 | |
78 | /* --- @crypt__sessionKey@ --- * |
79 | * |
80 | * Arguments: @const char *seedfile@ = pointer to name of seed file |
81 | * @unsigned char *k@ = our secret key |
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82 | * @unsigned *sk@ = where to store the session key |
83 | * @unsigned char *iv@ = where to store the IV |
84 | * |
85 | * Returns: --- |
86 | * |
87 | * Use: Decides on a random session key and initialisation vector. |
88 | */ |
89 | |
90 | static void crypt__sessionKey(const char *seedfile, unsigned char *k, |
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91 | unsigned char *sk, unsigned char *iv) |
92 | { |
93 | FILE *fp; /* File handle for reading */ |
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94 | struct flock l; |
95 | int ok = 1; |
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96 | |
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97 | /* --- Open the random seed file --- * |
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98 | * |
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99 | * If I can't manage that, create a new one. |
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100 | */ |
101 | |
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102 | if ((fp = fopen(seedfile, "r+")) == 0) { |
103 | ok = 0; |
104 | if ((fp = fopen(seedfile, "w+")) == 0) |
105 | die("can't create random number file: %s", strerror(errno)); |
106 | rand_clear(); |
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107 | } |
108 | |
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109 | /* --- Lock the seed file against concurrency problems --- */ |
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110 | |
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111 | l.l_type = F_WRLCK; |
112 | l.l_whence = SEEK_SET; |
113 | l.l_start = 0; |
114 | l.l_len = 0; |
115 | if (fcntl(fileno(fp), F_SETLKW, &l) < 0) |
116 | die("can't lock random number file: %s", strerror(errno)); |
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117 | |
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118 | /* --- Now read the file, and launder the seed --- */ |
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119 | |
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120 | if (ok) |
121 | rand_read(fp); |
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122 | |
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123 | /* --- Encrypt the pool using the secret key --- */ |
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124 | |
125 | { |
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126 | icrypt_job j; |
127 | icrypt_init(&j, k, 0); |
128 | rand_encrypt(&j); |
129 | burn(j); |
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130 | } |
131 | |
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132 | /* --- Generate the session key and IV --- */ |
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133 | |
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134 | noise_acquire(); |
135 | rand_extract(sk, IDEA_KEYSIZE); |
136 | rand_extract(iv, IDEA_BLKSIZE); |
137 | |
138 | IF_TRACING(TRACE_CRYPTO, |
139 | traceblk(TRACE_CRYPTO, "crypto: session key:", sk, IDEA_KEYSIZE); |
140 | traceblk(TRACE_CRYPTO, "crypto: initialisation vector:", |
141 | iv, IDEA_BLKSIZE); |
142 | ); |
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143 | |
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144 | /* --- Write the seed back --- */ |
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145 | |
146 | rewind(fp); |
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147 | rand_write(fp); |
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148 | fclose(fp); |
149 | |
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150 | } |
151 | |
152 | /* --- @crypt_packRequest@ --- * |
153 | * |
154 | * Arguments: @request *rq@ = pointer to request block |
155 | * @unsigned char *buff@ = pointer to a buffer |
156 | * @time_t t@ = the current time |
157 | * @pid_t pid@ = my process ID |
158 | * @unsigned char *k@ = pointer to 128-bit key |
159 | * @unsigned char *sk@ = where to put the session key |
160 | * |
161 | * Returns: --- |
162 | * |
163 | * Use: Packs a request block into a buffer. The buffer should have |
164 | * space for at least @crq_size@ bytes. The buffer comes back |
165 | * encrypted and ready to send. |
166 | */ |
167 | |
168 | void crypt_packRequest(request *rq, unsigned char *buff, |
169 | time_t t, pid_t pid, |
170 | unsigned char *k, unsigned char *sk) |
171 | { |
172 | /* --- First, build the easy stuff in the block --- */ |
173 | |
174 | buff[crq_cryptType] = cryptType_idea; |
175 | store32(buff + crq_time, t); |
176 | store32(buff + crq_pid, pid); |
177 | store32(buff + crq_from, rq->from); |
178 | store32(buff + crq_to, rq->to); |
179 | |
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180 | /* --- Now generate session keys and things --- */ |
181 | |
182 | crypt__sessionKey(file_RANDSEED, k, sk, buff + crq_iv); |
183 | memcpy(buff + crq_session, sk, IDEA_KEYSIZE); |
184 | |
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185 | /* --- The string causes a few problems --- * |
186 | * |
187 | * There's a good chance that the string will be a good deal shorter than |
188 | * the space allowed for it. This will probably mean lots of zeroes, and a |
189 | * very easy known-plaintext job for a potential attacker. (An early |
190 | * version of this code used @strncpy@ which is even worse!) |
191 | * |
192 | * I'll fill the block with random (from @rand@(3) -- nothing too |
193 | * elaborate) and then encrypt it using IDEA in CFB mode, using the first |
194 | * few bytes as the key. This should provide a sufficiently unpredictable |
195 | * background for the block. |
196 | */ |
197 | |
198 | { |
199 | icrypt_job j; |
200 | unsigned char *p; |
201 | unsigned u; |
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202 | md5 md; |
203 | unsigned char qk[IDEA_KEYSIZE]; |
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204 | |
205 | /* --- Initialise the buffer with junk --- */ |
206 | |
207 | srand((unsigned int)(t ^ pid)); /* Seed the (bad) RNG */ |
208 | for (p = buff + crq_cmd; p < buff + crq_cmd + CMDLEN_MAX; p++) { |
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209 | u = rand(); *p = u ^ (u >> 8); |
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210 | } |
211 | |
212 | /* --- Now make the junk a whole lot harder to predict --- */ |
213 | |
214 | p = buff + crq_cmd; |
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215 | md5_init(&md); md5_buffer(&md, p, CMDLEN_MAX); md5_final(&md, qk); |
216 | icrypt_init(&j, qk, 0); icrypt_encrypt(&j, p, p, CMDLEN_MAX); |
217 | burn(j); burn(qk); burn(md); |
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218 | |
219 | /* --- Copy the string into here --- */ |
220 | |
221 | strcpy((char *)buff + crq_cmd, rq->cmd); |
222 | } |
223 | |
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224 | /* --- Checksum the finished data --- */ |
225 | |
226 | { |
227 | md5 md; |
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228 | unsigned char mdbuf[MD5_HASHSIZE]; |
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229 | |
230 | md5_init(&md); |
231 | md5_buffer(&md, buff + crq_cipher, crq_check - crq_cipher); |
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232 | md5_final(&md, mdbuf); |
233 | memcpy(buff + crq_check, mdbuf, 4); |
234 | burn(md); burn(mdbuf); |
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235 | } |
236 | |
237 | /* --- Encrypt the block --- * |
238 | * |
239 | * First, encrypt the session key using the master key. Since the session |
240 | * key is effectively random, this makes cracking the master key much |
241 | * harder. The rest of the block is then encrypted with the session key, |
242 | * using the IV left over from encrypting the session key. |
243 | */ |
244 | |
245 | { |
246 | icrypt_job j; |
247 | |
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248 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext request:", |
249 | buff, crq_size); ) |
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250 | |
251 | icrypt_init(&j, k, buff + crq_iv); |
252 | icrypt_encrypt(&j, buff + crq_session, buff + crq_session, IDEA_KEYSIZE); |
253 | icrypt_reset(&j, sk, 0); |
254 | icrypt_encrypt(&j, buff + crq_cipher, |
255 | buff + crq_cipher, crq_size - crq_cipher); |
256 | burn(j); |
257 | |
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258 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext request:", |
259 | buff, crq_size); ) |
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260 | } |
261 | } |
262 | |
263 | /* --- @crypt_unpackRequest@ --- * |
264 | * |
265 | * Arguments: @reqest *rq@ = pointer to destination request block |
266 | * @unsigned char *buff@ = pointer to source buffer |
267 | * @unsigned char *k@ = pointer to encryption key |
268 | * @unsigned char *sk@ = pointer to where to store session key |
269 | * @unsigned char *rpl@ = where to start building reply |
270 | * |
271 | * Returns: Nonzero if it was decrypted OK |
272 | * |
273 | * Use: Decrypts and unpacks a request buffer. |
274 | */ |
275 | |
276 | int crypt_unpackRequest(request *rq, unsigned char *buff, |
277 | unsigned char *k, unsigned char *sk, |
278 | unsigned char *rpl) |
279 | { |
280 | { |
281 | /* --- Check the encryption format --- */ |
282 | |
283 | if (buff[crq_cryptType] != cryptType_idea) |
284 | return (0); |
285 | } |
286 | |
287 | { |
288 | /* --- First things first: decrypt the block --- */ |
289 | |
290 | icrypt_job j; |
291 | |
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292 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext request:", |
293 | buff, crq_size); ) |
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294 | |
295 | icrypt_init(&j, k, buff + crq_iv); |
296 | icrypt_decrypt(&j, buff + crq_session, buff + crq_session, IDEA_KEYSIZE); |
297 | memcpy(sk, buff + crq_session, IDEA_KEYSIZE); |
298 | icrypt_reset(&j, sk, 0); |
299 | icrypt_decrypt(&j, buff + crq_cipher, |
300 | buff + crq_cipher, crq_size - crq_cipher); |
301 | icrypt_saveIV(&j, rpl + crp_iv); |
302 | |
303 | memset(buff + crq_session, 0, IDEA_KEYSIZE); /* Burn, baby, burn */ |
304 | burn(j); |
305 | |
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306 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext request:", |
307 | buff, crq_size); ) |
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308 | } |
309 | |
310 | { |
311 | /* --- Check the validity of the data therein --- */ |
312 | |
313 | md5 md; |
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314 | unsigned char mdbuf[MD5_HASHSIZE]; |
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315 | |
316 | md5_init(&md); |
317 | md5_buffer(&md, buff + crq_cipher, crq_check - crq_cipher); |
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318 | md5_final(&md, mdbuf); |
319 | if (memcmp(mdbuf, buff + crq_check, 4) != 0) { |
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320 | syslog(LOG_INFO, "packet rejected: bad checksum"); |
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321 | T( trace(TRACE_CRYPTO, "crypto: bad checksum on incoming request"); ) |
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322 | return (0); |
323 | } |
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324 | burn(md); burn(mdbuf); |
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325 | } |
326 | |
327 | { |
328 | /* --- Extract fields from the block --- */ |
329 | |
330 | rq->from = load32(buff + crq_from); |
331 | rq->to = load32(buff + crq_to); |
332 | memcpy(rq->cmd, buff + crq_cmd, CMDLEN_MAX); |
333 | } |
334 | |
335 | { |
336 | /* --- Fill in bits of the reply block --- */ |
337 | |
338 | long t = (long)time(0); |
339 | long u = (long)load32(buff + crq_time); |
340 | |
341 | if (t - u > crypt__timeError || u - t > crypt__timeError) { |
342 | syslog(LOG_INFO, "packet rejected: bad time"); |
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343 | T( trace(TRACE_CRYPTO, "crypto: bad time on incoming request"); ) |
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344 | return (0); |
345 | } |
346 | memcpy(rpl + crp_time, buff + crq_time, 8); |
347 | } |
348 | |
349 | /* --- Done --- */ |
350 | |
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351 | T( trace(TRACE_CRYPTO, "crypto: valid request received"); ) |
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352 | return (1); |
353 | } |
354 | |
355 | /* --- @crypt_packReply@ --- * |
356 | * |
357 | * Arguments: @char *buff@ = pointer to reply block |
358 | * @unsigned char *sk@ = pointer to session key |
359 | * @int answer@ = yes or no |
360 | * |
361 | * Returns: --- |
362 | * |
363 | * Use: Packs and encrypts a reply block. |
364 | */ |
365 | |
366 | void crypt_packReply(unsigned char *buff, unsigned char *sk, int answer) |
367 | { |
368 | { |
369 | /* --- Store the answer --- */ |
370 | |
371 | buff[crp_answer] = (answer != 0); |
372 | } |
373 | |
374 | { |
375 | /* --- Build the checksum --- */ |
376 | |
377 | md5 md; |
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378 | unsigned char mdbuf[MD5_HASHSIZE]; |
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379 | |
380 | md5_init(&md); |
381 | md5_buffer(&md, buff + crp_cipher, crp_check - crp_cipher); |
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382 | md5_final(&md, mdbuf); |
383 | memcpy(buff + crp_check, mdbuf, 4); |
384 | burn(md); burn(mdbuf); |
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385 | } |
386 | |
387 | { |
388 | /* --- Encrypt the buffer --- */ |
389 | |
390 | icrypt_job j; |
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391 | |
392 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext reply:", buff, crp_size); ) |
393 | |
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394 | icrypt_init(&j, sk, buff + crp_iv); |
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395 | icrypt_encrypt(&j, buff + crp_cipher, |
396 | buff + crp_cipher, crp_size - crp_cipher); |
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397 | burn(j); |
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398 | |
399 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext reply:", buff, crp_size); ) |
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400 | } |
401 | } |
402 | |
403 | /* --- @crypt_unpackReply@ --- * |
404 | * |
405 | * Arguments: @unsigned char *buff@ = pointer to reply buffer |
406 | * @unsigned char *sk@ = pointer to session key |
407 | * @time_t t@ = time at which request was sent |
408 | * @pid_t pid@ = my process ID |
409 | * |
410 | * Returns: >0 if request granted, zero if denied, <0 if reply rejected |
411 | * |
412 | * Use: Unpacks a reply block, and informs the caller of the outcome. |
413 | */ |
414 | |
415 | int crypt_unpackReply(unsigned char *buff, unsigned char *sk, |
416 | time_t t, pid_t pid) |
417 | { |
418 | { |
419 | /* --- Decrypt my reply block --- */ |
420 | |
421 | icrypt_job j; |
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422 | |
423 | T( traceblk(TRACE_CRYPTO, "crypto: ciphertext reply:", buff, crp_size); ) |
424 | |
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425 | icrypt_init(&j, sk, buff + crp_iv); |
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426 | icrypt_decrypt(&j, buff + crp_cipher, |
427 | buff + crp_cipher, crp_size - crp_cipher); |
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428 | burn(j); |
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429 | |
430 | T( traceblk(TRACE_CRYPTO, "crypto: plaintext reply:", buff, crp_size); ) |
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431 | } |
432 | |
433 | { |
434 | /* --- Check validity --- */ |
435 | |
436 | md5 md; |
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437 | unsigned char mdbuf[MD5_HASHSIZE]; |
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438 | char b[8]; |
439 | |
440 | /* --- Check the checksum --- */ |
441 | |
442 | md5_init(&md); |
443 | md5_buffer(&md, buff + crp_cipher, crp_check - crp_cipher); |
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444 | md5_final(&md, mdbuf); |
445 | if (memcmp(buff + crp_check, mdbuf, 4) != 0) { |
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446 | syslog(LOG_INFO, "reply rejected: bad checksum"); |
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447 | T( trace(TRACE_CRYPTO, "crypto: bad checksum on reply"); ) |
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448 | return (-1); |
449 | } |
450 | |
451 | /* --- Check the identifier --- */ |
452 | |
453 | store32(b + 0, t); store32(b + 4, pid); |
454 | if (memcmp(b, buff + crp_time, sizeof(b)) != 0) { |
455 | syslog(LOG_INFO, "reply rejected: bad identification marker"); |
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456 | T( trace(TRACE_CRYPTO, "crypto: bad id on reply"); ) |
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457 | return (-1); |
458 | } |
459 | } |
460 | |
461 | /* --- Return the value --- */ |
462 | |
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463 | T( trace(TRACE_CRYPTO, "crypto: valid reply received"); ) |
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464 | return (buff[crp_answer]); |
465 | } |
466 | |
467 | /*----- Test rig ----------------------------------------------------------*/ |
468 | |
469 | #ifdef TEST_RIG |
470 | |
471 | int main(int argc, char *argv[]) |
472 | { |
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473 | unsigned char buff[8]; |
474 | unsigned char sk[IDEA_KEYSIZE], k[IDEA_KEYSIZE]; |
475 | FILE *fp; |
476 | |
477 | ego(argv[0]); |
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478 | traceon(stdout, TRACE_CRYPTO); |
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479 | if (argc < 3) |
480 | die("bad args"); |
481 | fp = fopen(argv[1], "r"); |
482 | if (!fp) |
483 | die("fopen: %s", strerror(errno)); |
484 | tx_getBits(k, 128, fp); |
485 | fclose(fp); |
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486 | crypt__sessionKey(argv[2], k, sk, buff); |
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487 | return (0); |
488 | } |
489 | |
490 | #endif |
491 | |
492 | /*----- That's all, folks -------------------------------------------------*/ |