Line data Source code
1 : /* encrypt.c - Encrypt a message
2 : * Copyright (C) 2001, 2003, 2004, 2007, 2008,
3 : * 2010 Free Software Foundation, Inc.
4 : *
5 : * This file is part of GnuPG.
6 : *
7 : * GnuPG is free software; you can redistribute it and/or modify
8 : * it under the terms of the GNU General Public License as published by
9 : * the Free Software Foundation; either version 3 of the License, or
10 : * (at your option) any later version.
11 : *
12 : * GnuPG is distributed in the hope that it will be useful,
13 : * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 : * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 : * GNU General Public License for more details.
16 : *
17 : * You should have received a copy of the GNU General Public License
18 : * along with this program; if not, see <https://www.gnu.org/licenses/>.
19 : */
20 :
21 : #include <config.h>
22 : #include <stdio.h>
23 : #include <stdlib.h>
24 : #include <string.h>
25 : #include <errno.h>
26 : #include <unistd.h>
27 : #include <time.h>
28 : #include <assert.h>
29 :
30 : #include "gpgsm.h"
31 : #include <gcrypt.h>
32 : #include <ksba.h>
33 :
34 : #include "keydb.h"
35 : #include "i18n.h"
36 :
37 :
38 : struct dek_s {
39 : const char *algoid;
40 : int algo;
41 : gcry_cipher_hd_t chd;
42 : char key[32];
43 : int keylen;
44 : char iv[32];
45 : int ivlen;
46 : };
47 : typedef struct dek_s *DEK;
48 :
49 :
50 : /* Callback parameters for the encryption. */
51 : struct encrypt_cb_parm_s
52 : {
53 : estream_t fp;
54 : DEK dek;
55 : int eof_seen;
56 : int ready;
57 : int readerror;
58 : int bufsize;
59 : unsigned char *buffer;
60 : int buflen;
61 : };
62 :
63 :
64 :
65 :
66 :
67 : /* Initialize the data encryption key (session key). */
68 : static int
69 0 : init_dek (DEK dek)
70 : {
71 0 : int rc=0, mode, i;
72 :
73 0 : dek->algo = gcry_cipher_map_name (dek->algoid);
74 0 : mode = gcry_cipher_mode_from_oid (dek->algoid);
75 0 : if (!dek->algo || !mode)
76 : {
77 0 : log_error ("unsupported algorithm '%s'\n", dek->algoid);
78 0 : return gpg_error (GPG_ERR_UNSUPPORTED_ALGORITHM);
79 : }
80 :
81 : /* Extra check for algorithms we consider to be too weak for
82 : encryption, although we support them for decryption. Note that
83 : there is another check below discriminating on the key length. */
84 0 : switch (dek->algo)
85 : {
86 : case GCRY_CIPHER_DES:
87 : case GCRY_CIPHER_RFC2268_40:
88 0 : log_error ("cipher algorithm '%s' not allowed: too weak\n",
89 : gnupg_cipher_algo_name (dek->algo));
90 0 : return gpg_error (GPG_ERR_UNSUPPORTED_ALGORITHM);
91 : default:
92 0 : break;
93 : }
94 :
95 0 : dek->keylen = gcry_cipher_get_algo_keylen (dek->algo);
96 0 : if (!dek->keylen || dek->keylen > sizeof (dek->key))
97 0 : return gpg_error (GPG_ERR_BUG);
98 :
99 0 : dek->ivlen = gcry_cipher_get_algo_blklen (dek->algo);
100 0 : if (!dek->ivlen || dek->ivlen > sizeof (dek->iv))
101 0 : return gpg_error (GPG_ERR_BUG);
102 :
103 : /* Make sure we don't use weak keys. */
104 0 : if (dek->keylen < 100/8)
105 : {
106 0 : log_error ("key length of '%s' too small\n", dek->algoid);
107 0 : return gpg_error (GPG_ERR_UNSUPPORTED_ALGORITHM);
108 : }
109 :
110 0 : rc = gcry_cipher_open (&dek->chd, dek->algo, mode, GCRY_CIPHER_SECURE);
111 0 : if (rc)
112 : {
113 0 : log_error ("failed to create cipher context: %s\n", gpg_strerror (rc));
114 0 : return rc;
115 : }
116 :
117 0 : for (i=0; i < 8; i++)
118 : {
119 0 : gcry_randomize (dek->key, dek->keylen, GCRY_STRONG_RANDOM );
120 0 : rc = gcry_cipher_setkey (dek->chd, dek->key, dek->keylen);
121 0 : if (gpg_err_code (rc) != GPG_ERR_WEAK_KEY)
122 0 : break;
123 0 : log_info(_("weak key created - retrying\n") );
124 : }
125 0 : if (rc)
126 : {
127 0 : log_error ("failed to set the key: %s\n", gpg_strerror (rc));
128 0 : gcry_cipher_close (dek->chd);
129 0 : dek->chd = NULL;
130 0 : return rc;
131 : }
132 :
133 0 : gcry_create_nonce (dek->iv, dek->ivlen);
134 0 : rc = gcry_cipher_setiv (dek->chd, dek->iv, dek->ivlen);
135 0 : if (rc)
136 : {
137 0 : log_error ("failed to set the IV: %s\n", gpg_strerror (rc));
138 0 : gcry_cipher_close (dek->chd);
139 0 : dek->chd = NULL;
140 0 : return rc;
141 : }
142 :
143 0 : return 0;
144 : }
145 :
146 :
147 : static int
148 0 : encode_session_key (DEK dek, gcry_sexp_t * r_data)
149 : {
150 : gcry_sexp_t data;
151 : char *p;
152 : int rc;
153 :
154 0 : p = xtrymalloc (64 + 2 * dek->keylen);
155 0 : if (!p)
156 0 : return gpg_error_from_syserror ();
157 0 : strcpy (p, "(data\n (flags pkcs1)\n (value #");
158 0 : bin2hex (dek->key, dek->keylen, p + strlen (p));
159 0 : strcat (p, "#))\n");
160 0 : rc = gcry_sexp_sscan (&data, NULL, p, strlen (p));
161 0 : xfree (p);
162 0 : *r_data = data;
163 0 : return rc;
164 : }
165 :
166 :
167 : /* Encrypt the DEK under the key contained in CERT and return it as a
168 : canonical S-Exp in encval. */
169 : static int
170 0 : encrypt_dek (const DEK dek, ksba_cert_t cert, unsigned char **encval)
171 : {
172 : gcry_sexp_t s_ciph, s_data, s_pkey;
173 : int rc;
174 : ksba_sexp_t buf;
175 : size_t len;
176 :
177 0 : *encval = NULL;
178 :
179 : /* get the key from the cert */
180 0 : buf = ksba_cert_get_public_key (cert);
181 0 : if (!buf)
182 : {
183 0 : log_error ("no public key for recipient\n");
184 0 : return gpg_error (GPG_ERR_NO_PUBKEY);
185 : }
186 0 : len = gcry_sexp_canon_len (buf, 0, NULL, NULL);
187 0 : if (!len)
188 : {
189 0 : log_error ("libksba did not return a proper S-Exp\n");
190 0 : return gpg_error (GPG_ERR_BUG);
191 : }
192 0 : rc = gcry_sexp_sscan (&s_pkey, NULL, (char*)buf, len);
193 0 : xfree (buf); buf = NULL;
194 0 : if (rc)
195 : {
196 0 : log_error ("gcry_sexp_scan failed: %s\n", gpg_strerror (rc));
197 0 : return rc;
198 : }
199 :
200 : /* Put the encoded cleartext into a simple list. */
201 0 : s_data = NULL; /* (avoid compiler warning) */
202 0 : rc = encode_session_key (dek, &s_data);
203 0 : if (rc)
204 : {
205 0 : log_error ("encode_session_key failed: %s\n", gpg_strerror (rc));
206 0 : return rc;
207 : }
208 :
209 : /* pass it to libgcrypt */
210 0 : rc = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
211 0 : gcry_sexp_release (s_data);
212 0 : gcry_sexp_release (s_pkey);
213 :
214 : /* Reformat it. */
215 0 : if (!rc)
216 : {
217 0 : rc = make_canon_sexp (s_ciph, encval, NULL);
218 0 : gcry_sexp_release (s_ciph);
219 : }
220 0 : return rc;
221 : }
222 :
223 :
224 :
225 : /* do the actual encryption */
226 : static int
227 0 : encrypt_cb (void *cb_value, char *buffer, size_t count, size_t *nread)
228 : {
229 0 : struct encrypt_cb_parm_s *parm = cb_value;
230 0 : int blklen = parm->dek->ivlen;
231 : unsigned char *p;
232 : size_t n;
233 :
234 0 : *nread = 0;
235 0 : if (!buffer)
236 0 : return -1; /* not supported */
237 :
238 0 : if (parm->ready)
239 0 : return -1;
240 :
241 0 : if (count < blklen)
242 0 : BUG ();
243 :
244 0 : if (!parm->eof_seen)
245 : { /* fillup the buffer */
246 0 : p = parm->buffer;
247 0 : for (n=parm->buflen; n < parm->bufsize; n++)
248 : {
249 0 : int c = es_getc (parm->fp);
250 0 : if (c == EOF)
251 : {
252 0 : if (es_ferror (parm->fp))
253 : {
254 0 : parm->readerror = errno;
255 0 : return -1;
256 : }
257 0 : parm->eof_seen = 1;
258 0 : break;
259 : }
260 0 : p[n] = c;
261 : }
262 0 : parm->buflen = n;
263 : }
264 :
265 0 : n = parm->buflen < count? parm->buflen : count;
266 0 : n = n/blklen * blklen;
267 0 : if (n)
268 : { /* encrypt the stuff */
269 0 : gcry_cipher_encrypt (parm->dek->chd, buffer, n, parm->buffer, n);
270 0 : *nread = n;
271 : /* Who cares about cycles, take the easy way and shift the buffer */
272 0 : parm->buflen -= n;
273 0 : memmove (parm->buffer, parm->buffer+n, parm->buflen);
274 : }
275 0 : else if (parm->eof_seen)
276 : { /* no complete block but eof: add padding */
277 : /* fixme: we should try to do this also in the above code path */
278 0 : int i, npad = blklen - (parm->buflen % blklen);
279 0 : p = parm->buffer;
280 0 : for (n=parm->buflen, i=0; n < parm->bufsize && i < npad; n++, i++)
281 0 : p[n] = npad;
282 0 : gcry_cipher_encrypt (parm->dek->chd, buffer, n, parm->buffer, n);
283 0 : *nread = n;
284 0 : parm->ready = 1;
285 : }
286 :
287 0 : return 0;
288 : }
289 :
290 :
291 :
292 :
293 : /* Perform an encrypt operation.
294 :
295 : Encrypt the data received on DATA-FD and write it to OUT_FP. The
296 : recipients are take from the certificate given in recplist; if this
297 : is NULL it will be encrypted for a default recipient */
298 : int
299 0 : gpgsm_encrypt (ctrl_t ctrl, certlist_t recplist, int data_fd, estream_t out_fp)
300 : {
301 0 : int rc = 0;
302 0 : Base64Context b64writer = NULL;
303 : gpg_error_t err;
304 : ksba_writer_t writer;
305 0 : ksba_reader_t reader = NULL;
306 0 : ksba_cms_t cms = NULL;
307 : ksba_stop_reason_t stopreason;
308 0 : KEYDB_HANDLE kh = NULL;
309 : struct encrypt_cb_parm_s encparm;
310 0 : DEK dek = NULL;
311 : int recpno;
312 0 : estream_t data_fp = NULL;
313 : certlist_t cl;
314 : int count;
315 :
316 0 : memset (&encparm, 0, sizeof encparm);
317 :
318 0 : audit_set_type (ctrl->audit, AUDIT_TYPE_ENCRYPT);
319 :
320 : /* Check that the certificate list is not empty and that at least
321 : one certificate is not flagged as encrypt_to; i.e. is a real
322 : recipient. */
323 0 : for (cl = recplist; cl; cl = cl->next)
324 0 : if (!cl->is_encrypt_to)
325 0 : break;
326 0 : if (!cl)
327 : {
328 0 : log_error(_("no valid recipients given\n"));
329 0 : gpgsm_status (ctrl, STATUS_NO_RECP, "0");
330 0 : audit_log_i (ctrl->audit, AUDIT_GOT_RECIPIENTS, 0);
331 0 : rc = gpg_error (GPG_ERR_NO_PUBKEY);
332 0 : goto leave;
333 : }
334 :
335 0 : for (count = 0, cl = recplist; cl; cl = cl->next)
336 0 : count++;
337 0 : audit_log_i (ctrl->audit, AUDIT_GOT_RECIPIENTS, count);
338 :
339 0 : kh = keydb_new ();
340 0 : if (!kh)
341 : {
342 0 : log_error (_("failed to allocate keyDB handle\n"));
343 0 : rc = gpg_error (GPG_ERR_GENERAL);
344 0 : goto leave;
345 : }
346 :
347 : /* Fixme: We should use the unlocked version of the es functions. */
348 0 : data_fp = es_fdopen_nc (data_fd, "rb");
349 0 : if (!data_fp)
350 : {
351 0 : rc = gpg_error_from_syserror ();
352 0 : log_error ("fdopen() failed: %s\n", strerror (errno));
353 0 : goto leave;
354 : }
355 :
356 0 : err = ksba_reader_new (&reader);
357 0 : if (err)
358 0 : rc = err;
359 0 : if (!rc)
360 0 : rc = ksba_reader_set_cb (reader, encrypt_cb, &encparm);
361 0 : if (rc)
362 0 : goto leave;
363 :
364 0 : encparm.fp = data_fp;
365 :
366 0 : ctrl->pem_name = "ENCRYPTED MESSAGE";
367 0 : rc = gpgsm_create_writer (&b64writer, ctrl, out_fp, &writer);
368 0 : if (rc)
369 : {
370 0 : log_error ("can't create writer: %s\n", gpg_strerror (rc));
371 0 : goto leave;
372 : }
373 :
374 0 : err = ksba_cms_new (&cms);
375 0 : if (err)
376 : {
377 0 : rc = err;
378 0 : goto leave;
379 : }
380 :
381 0 : err = ksba_cms_set_reader_writer (cms, reader, writer);
382 0 : if (err)
383 : {
384 0 : log_debug ("ksba_cms_set_reader_writer failed: %s\n",
385 : gpg_strerror (err));
386 0 : rc = err;
387 0 : goto leave;
388 : }
389 :
390 0 : audit_log (ctrl->audit, AUDIT_GOT_DATA);
391 :
392 : /* We are going to create enveloped data with uninterpreted data as
393 : inner content */
394 0 : err = ksba_cms_set_content_type (cms, 0, KSBA_CT_ENVELOPED_DATA);
395 0 : if (!err)
396 0 : err = ksba_cms_set_content_type (cms, 1, KSBA_CT_DATA);
397 0 : if (err)
398 : {
399 0 : log_debug ("ksba_cms_set_content_type failed: %s\n",
400 : gpg_strerror (err));
401 0 : rc = err;
402 0 : goto leave;
403 : }
404 :
405 : /* Create a session key */
406 0 : dek = xtrycalloc_secure (1, sizeof *dek);
407 0 : if (!dek)
408 0 : rc = out_of_core ();
409 : else
410 : {
411 0 : dek->algoid = opt.def_cipher_algoid;
412 0 : rc = init_dek (dek);
413 : }
414 0 : if (rc)
415 : {
416 0 : log_error ("failed to create the session key: %s\n",
417 : gpg_strerror (rc));
418 0 : goto leave;
419 : }
420 :
421 0 : err = ksba_cms_set_content_enc_algo (cms, dek->algoid, dek->iv, dek->ivlen);
422 0 : if (err)
423 : {
424 0 : log_error ("ksba_cms_set_content_enc_algo failed: %s\n",
425 : gpg_strerror (err));
426 0 : rc = err;
427 0 : goto leave;
428 : }
429 :
430 0 : encparm.dek = dek;
431 : /* Use a ~8k (AES) or ~4k (3DES) buffer */
432 0 : encparm.bufsize = 500 * dek->ivlen;
433 0 : encparm.buffer = xtrymalloc (encparm.bufsize);
434 0 : if (!encparm.buffer)
435 : {
436 0 : rc = out_of_core ();
437 0 : goto leave;
438 : }
439 :
440 0 : audit_log_s (ctrl->audit, AUDIT_SESSION_KEY, dek->algoid);
441 :
442 : /* Gather certificates of recipients, encrypt the session key for
443 : each and store them in the CMS object */
444 0 : for (recpno = 0, cl = recplist; cl; recpno++, cl = cl->next)
445 : {
446 : unsigned char *encval;
447 :
448 0 : rc = encrypt_dek (dek, cl->cert, &encval);
449 0 : if (rc)
450 : {
451 0 : audit_log_cert (ctrl->audit, AUDIT_ENCRYPTED_TO, cl->cert, rc);
452 0 : log_error ("encryption failed for recipient no. %d: %s\n",
453 : recpno, gpg_strerror (rc));
454 0 : goto leave;
455 : }
456 :
457 0 : err = ksba_cms_add_recipient (cms, cl->cert);
458 0 : if (err)
459 : {
460 0 : audit_log_cert (ctrl->audit, AUDIT_ENCRYPTED_TO, cl->cert, err);
461 0 : log_error ("ksba_cms_add_recipient failed: %s\n",
462 : gpg_strerror (err));
463 0 : rc = err;
464 0 : xfree (encval);
465 0 : goto leave;
466 : }
467 :
468 0 : err = ksba_cms_set_enc_val (cms, recpno, encval);
469 0 : xfree (encval);
470 0 : audit_log_cert (ctrl->audit, AUDIT_ENCRYPTED_TO, cl->cert, err);
471 0 : if (err)
472 : {
473 0 : log_error ("ksba_cms_set_enc_val failed: %s\n",
474 : gpg_strerror (err));
475 0 : rc = err;
476 0 : goto leave;
477 : }
478 : }
479 :
480 : /* Main control loop for encryption. */
481 0 : recpno = 0;
482 : do
483 : {
484 0 : err = ksba_cms_build (cms, &stopreason);
485 0 : if (err)
486 : {
487 0 : log_debug ("ksba_cms_build failed: %s\n", gpg_strerror (err));
488 0 : rc = err;
489 0 : goto leave;
490 : }
491 : }
492 0 : while (stopreason != KSBA_SR_READY);
493 :
494 0 : if (encparm.readerror)
495 : {
496 0 : log_error ("error reading input: %s\n", strerror (encparm.readerror));
497 0 : rc = gpg_error (gpg_err_code_from_errno (encparm.readerror));
498 0 : goto leave;
499 : }
500 :
501 :
502 0 : rc = gpgsm_finish_writer (b64writer);
503 0 : if (rc)
504 : {
505 0 : log_error ("write failed: %s\n", gpg_strerror (rc));
506 0 : goto leave;
507 : }
508 0 : audit_log (ctrl->audit, AUDIT_ENCRYPTION_DONE);
509 0 : log_info ("encrypted data created\n");
510 :
511 : leave:
512 0 : ksba_cms_release (cms);
513 0 : gpgsm_destroy_writer (b64writer);
514 0 : ksba_reader_release (reader);
515 0 : keydb_release (kh);
516 0 : xfree (dek);
517 0 : es_fclose (data_fp);
518 0 : xfree (encparm.buffer);
519 0 : return rc;
520 : }
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