Merge branch 'refs/heads/t/rm_rc4'
[paraslash.git] / gcrypt.c
1 /*
2 * Copyright (C) 2011 Andre Noll <maan@tuebingen.mpg.de>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file gcrypt.c Libgrcypt-based encryption/decryption routines. */
8
9 #include <regex.h>
10 #include <gcrypt.h>
11
12 #include "para.h"
13 #include "error.h"
14 #include "string.h"
15 #include "crypt.h"
16 #include "crypt_backend.h"
17 #include "fd.h"
18 #include "base64.h"
19
20 //#define GCRYPT_DEBUG 1
21
22 #ifdef GCRYPT_DEBUG
23 static void dump_buffer(const char *msg, unsigned char *buf, int len)
24 {
25 int i;
26
27 fprintf(stderr, "%s (%d bytes): ", msg, len);
28 for (i = 0; i < len; i++)
29 fprintf(stderr, "%02x ", buf[i]);
30 fprintf(stderr, "\n");
31 }
32 #else
33 /** Empty. Define GCRYPT_DEBUG to dump buffers. */
34 #define dump_buffer(a, b, c)
35 #endif
36
37 void hash_function(const char *data, unsigned long len, unsigned char *hash)
38 {
39 gcry_error_t gret;
40 gcry_md_hd_t handle;
41 unsigned char *md;
42
43 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
44 assert(gret == 0);
45 gcry_md_write(handle, data, (size_t)len);
46 gcry_md_final(handle);
47 md = gcry_md_read(handle, GCRY_MD_SHA1);
48 assert(md);
49 memcpy(hash, md, HASH_SIZE);
50 gcry_md_close(handle);
51 }
52
53 void get_random_bytes_or_die(unsigned char *buf, int num)
54 {
55 gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
56 }
57
58 /*
59 * This is called at the beginning of every program that uses libgcrypt. We
60 * don't have to initialize any random seed here, but we must initialize the
61 * gcrypt library. This task is performed by gcry_check_version() which can
62 * also check that the gcrypt library version is at least the minimal required
63 * version.
64 */
65 void init_random_seed_or_die(void)
66 {
67 const char *req_ver = "1.5.0";
68
69 if (gcry_check_version(req_ver))
70 return;
71 PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
72 req_ver, gcry_check_version(NULL));
73 exit(EXIT_FAILURE);
74 }
75
76 /** S-expression for the public part of an RSA key. */
77 #define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
78 /** S-expression for a private RSA key. */
79 #define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
80 /** S-expression for decryption. */
81 #define RSA_DECRYPT_SEXP "(enc-val(flags oaep)(rsa(a %m)))"
82
83 struct asymmetric_key {
84 gcry_sexp_t sexp;
85 int num_bytes;
86 };
87
88 static const char *gcrypt_strerror(gcry_error_t gret)
89 {
90 return gcry_strerror(gcry_err_code(gret));
91 }
92
93 static int decode_key(const char *key_file, const char *header_str,
94 const char *footer_str, unsigned char **result)
95 {
96 int ret, ret2, i, j;
97 void *map;
98 size_t map_size, key_size, blob_size;
99 unsigned char *blob = NULL;
100 char *begin, *footer, *key;
101
102 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
103 if (ret < 0)
104 goto out;
105 ret = -E_KEY_MARKER;
106 if (strncmp(map, header_str, strlen(header_str)))
107 goto unmap;
108 footer = strstr(map, footer_str);
109 ret = -E_KEY_MARKER;
110 if (!footer)
111 goto unmap;
112 begin = map + strlen(header_str);
113 /* skip whitespace at the beginning */
114 for (; begin < footer; begin++) {
115 if (para_isspace(*begin))
116 continue;
117 break;
118 }
119 ret = -E_KEY_MARKER;
120 if (begin >= footer)
121 goto unmap;
122
123 key_size = footer - begin;
124 key = para_malloc(key_size + 1);
125 for (i = 0, j = 0; begin + i < footer; i++) {
126 if (para_isspace(begin[i]))
127 continue;
128 key[j++] = begin[i];
129 }
130 key[j] = '\0';
131 ret = base64_decode(key, j, (char **)&blob, &blob_size);
132 free(key);
133 if (ret < 0)
134 goto free_unmap;
135 ret = blob_size;
136 goto unmap;
137 free_unmap:
138 free(blob);
139 blob = NULL;
140 unmap:
141 ret2 = para_munmap(map, map_size);
142 if (ret >= 0 && ret2 < 0)
143 ret = ret2;
144 if (ret < 0) {
145 free(blob);
146 blob = NULL;
147 }
148 out:
149 *result = blob;
150 return ret;
151 }
152
153 /** ASN Types and their code. */
154 enum asn1_types {
155 /** The next object is an integer. */
156 ASN1_TYPE_INTEGER = 0x2,
157 /** Bit string object. */
158 ASN1_TYPE_BIT_STRING = 0x03,
159 /** Keys start with one big type sequence. */
160 ASN1_TYPE_SEQUENCE = 0x30,
161 };
162
163 /* bit 6 has value 0 */
164 static inline bool is_primitive(unsigned char c)
165 {
166 return (c & (1<<6)) == 0;
167 }
168
169 static inline bool is_primitive_integer(unsigned char c)
170 {
171 if (!is_primitive(c))
172 return false;
173 return (c & 0x1f) == ASN1_TYPE_INTEGER;
174 }
175
176 /* Bit 8 is zero (and bits 7-1 give the length) */
177 static inline bool is_short_form(unsigned char c)
178 {
179 return (c & 0x80) == 0;
180 }
181
182 static inline int get_short_form_length(unsigned char c)
183 {
184 return c & 0x7f;
185 }
186
187 static inline int get_long_form_num_length_bytes(unsigned char c)
188 {
189 return c & 0x7f;
190 }
191
192 /*
193 * Returns: Number of bytes scanned. This may differ from the value returned via
194 * bn_bytes because the latter does not include the ASN.1 prefix and a leading
195 * zero is not considered as an additional byte for bn_bytes.
196 */
197 static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
198 int *bn_bytes)
199 {
200 int i, bn_size;
201 gcry_error_t gret;
202 unsigned char *cp = start;
203
204 if (!is_primitive_integer(*cp))
205 return -E_BAD_PRIVATE_KEY;
206 cp++;
207 if (is_short_form(*cp)) {
208 bn_size = get_short_form_length(*cp);
209 cp++;
210 } else {
211 int num_bytes = get_long_form_num_length_bytes(*cp);
212 if (cp + num_bytes > end)
213 return -E_BAD_PRIVATE_KEY;
214 if (num_bytes > 4) /* nobody has such a large modulus */
215 return -E_BAD_PRIVATE_KEY;
216 cp++;
217 bn_size = 0;
218 for (i = 0; i < num_bytes; i++, cp++)
219 bn_size = (bn_size << 8) + *cp;
220 }
221 PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, (unsigned)bn_size);
222 gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
223 if (gret) {
224 PARA_ERROR_LOG("%s while scanning n\n",
225 gcry_strerror(gcry_err_code(gret)));
226 return-E_MPI_SCAN;
227 }
228 /*
229 * Don't take the first leading zero into account for the size of the
230 * bignum.
231 */
232 if (*cp == '\0') {
233 cp++;
234 bn_size--;
235 }
236 if (bn_bytes)
237 *bn_bytes = bn_size;
238 cp += bn_size;
239 // unsigned char *buf;
240 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
241 // PARA_CRIT_LOG("bn: %s\n", buf);
242 return cp - start;
243 }
244
245 static int find_privkey_bignum_offset(const unsigned char *data, int len)
246 {
247 const unsigned char *p = data, *end = data + len;
248
249 /* like the public key, the whole thing is contained in a sequence */
250 if (*p != ASN1_TYPE_SEQUENCE)
251 return -E_ASN1_PARSE;
252 p++;
253 if (p >= end)
254 return -E_ASN1_PARSE;
255 if (is_short_form(*p))
256 p++;
257 else
258 p += 1 + get_long_form_num_length_bytes(*p);
259 if (p >= end)
260 return -E_ASN1_PARSE;
261
262 /* skip next integer */
263 if (*p != ASN1_TYPE_INTEGER)
264 return -E_ASN1_PARSE;
265 p++;
266 if (p >= end)
267 return -E_ASN1_PARSE;
268 if (is_short_form(*p))
269 p += 1 + get_short_form_length(*p);
270 else
271 p += 1 + get_long_form_num_length_bytes(*p);
272 if (p >= end)
273 return -E_ASN1_PARSE;
274 return p - data;
275 }
276
277 /** Private keys start with this header. */
278 #define PRIVATE_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
279 /** Private keys end with this footer. */
280 #define PRIVATE_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
281
282 static int get_private_key(const char *key_file, struct asymmetric_key **result)
283 {
284 gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
285 u = NULL;
286 unsigned char *blob, *cp, *end;
287 int blob_size, ret, n_size;
288 gcry_error_t gret;
289 size_t erroff;
290 gcry_sexp_t sexp;
291 struct asymmetric_key *key;
292
293 *result = NULL;
294 ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
295 &blob);
296 if (ret < 0)
297 return ret;
298 blob_size = ret;
299 end = blob + blob_size;
300 ret = find_privkey_bignum_offset(blob, blob_size);
301 if (ret < 0)
302 goto free_blob;
303 PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
304 cp = blob + ret;
305
306 ret = read_bignum(cp, end, &n, &n_size);
307 if (ret < 0)
308 goto free_blob;
309 cp += ret;
310
311 ret = read_bignum(cp, end, &e, NULL);
312 if (ret < 0)
313 goto release_n;
314 cp += ret;
315
316 ret = read_bignum(cp, end, &d, NULL);
317 if (ret < 0)
318 goto release_e;
319 cp += ret;
320
321 ret = read_bignum(cp, end, &p, NULL);
322 if (ret < 0)
323 goto release_d;
324 cp += ret;
325
326 ret = read_bignum(cp, end, &q, NULL);
327 if (ret < 0)
328 goto release_p;
329 cp += ret;
330 ret = read_bignum(cp, end, &u, NULL);
331 if (ret < 0)
332 goto release_q;
333 /*
334 * OpenSSL uses slightly different parameters than gcrypt. To use these
335 * parameters we need to swap the values of p and q and recompute u.
336 */
337 if (gcry_mpi_cmp(p, q) > 0) {
338 gcry_mpi_swap(p, q);
339 gcry_mpi_invm(u, p, q);
340 }
341 gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
342 n, e, d, p, q, u);
343
344 if (gret) {
345 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
346 gcry_strerror(gcry_err_code(gret)));
347 ret = -E_SEXP_BUILD;
348 goto release_u;
349 }
350 key = para_malloc(sizeof(*key));
351 key->sexp = sexp;
352 *result = key;
353 ret = n_size * 8;
354 PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
355 release_u:
356 gcry_mpi_release(u);
357 release_q:
358 gcry_mpi_release(q);
359 release_p:
360 gcry_mpi_release(p);
361 release_d:
362 gcry_mpi_release(d);
363 release_e:
364 gcry_mpi_release(e);
365 release_n:
366 gcry_mpi_release(n);
367 free_blob:
368 free(blob);
369 return ret;
370 }
371
372 static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
373 {
374 int ret;
375 gcry_error_t gret;
376 unsigned char *blob = NULL, *p, *end;
377 size_t nr_scanned, erroff, decoded_size;
378 gcry_mpi_t e = NULL, n = NULL;
379
380 PARA_DEBUG_LOG("decoding %d byte public rsa-ssh key\n", size);
381 ret = uudecode((char *)data, size, (char **)&blob, &decoded_size);
382 if (ret < 0)
383 goto free_blob;
384 end = blob + decoded_size;
385 dump_buffer("decoded key", blob, decoded_size);
386 ret = check_ssh_key_header(blob, decoded_size);
387 if (ret < 0)
388 goto free_blob;
389 p = blob + ret;
390 ret = -E_SSH_PARSE;
391 if (p >= end)
392 goto free_blob;
393 PARA_DEBUG_LOG("scanning modulus and public exponent\n");
394 gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
395 if (gret) {
396 ret = -E_MPI_SCAN;
397 PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
398 goto free_blob;
399 }
400 PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
401 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_e);
402 // PARA_CRIT_LOG("e: %s\n", buf);
403 p += nr_scanned;
404 if (p >= end)
405 goto release_e;
406 gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
407 if (gret) {
408 ret = -E_MPI_SCAN;
409 PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
410 goto release_e;
411 }
412 PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
413 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_n);
414 // PARA_CRIT_LOG("n: %s\n", buf);
415 gret = gcry_sexp_build(result, &erroff, RSA_PUBKEY_SEXP, n, e);
416 if (gret) {
417 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
418 gcry_strerror(gcry_err_code(gret)));
419 ret = -E_SEXP_BUILD;
420 goto release_n;
421 }
422 ret = nr_scanned / 32 * 32;
423 PARA_INFO_LOG("successfully read %d bit ssh public key\n", ret * 8);
424 release_n:
425 gcry_mpi_release(n);
426 release_e:
427 gcry_mpi_release(e);
428 free_blob:
429 free(blob);
430 return ret;
431 }
432
433 int get_public_key(const char *key_file, struct asymmetric_key **result)
434 {
435 int ret, ret2;
436 void *map;
437 size_t map_size;
438 unsigned char *start, *end;
439 gcry_sexp_t sexp;
440 struct asymmetric_key *key;
441
442 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
443 if (ret < 0)
444 return ret;
445 ret = is_ssh_rsa_key(map, map_size);
446 if (!ret) {
447 para_munmap(map, map_size);
448 return -E_SSH_PARSE;
449 }
450 start = map + ret;
451 end = map + map_size;
452 ret = -E_SSH_PARSE;
453 if (start >= end)
454 goto unmap;
455 ret = get_ssh_public_key(start, end - start, &sexp);
456 if (ret < 0)
457 goto unmap;
458 key = para_malloc(sizeof(*key));
459 key->num_bytes = ret;
460 key->sexp = sexp;
461 *result = key;
462 unmap:
463 ret2 = para_munmap(map, map_size);
464 if (ret >= 0 && ret2 < 0)
465 ret = ret2;
466 return ret;
467 }
468
469 void free_public_key(struct asymmetric_key *key)
470 {
471 if (!key)
472 return;
473 gcry_sexp_release(key->sexp);
474 free(key);
475 }
476
477 static int decode_rsa(gcry_sexp_t sexp, unsigned char *outbuf, size_t *nbytes)
478 {
479 const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
480
481 if (!p)
482 return -E_RSA_DECODE;
483 memcpy(outbuf, p, *nbytes);
484 return 1;
485 }
486
487 int priv_decrypt(const char *key_file, unsigned char *outbuf,
488 unsigned char *inbuf, int inlen)
489 {
490 gcry_error_t gret;
491 int ret;
492 struct asymmetric_key *priv;
493 gcry_mpi_t in_mpi = NULL;
494 gcry_sexp_t in, out, priv_key;
495 size_t nbytes;
496
497 ret = check_private_key_file(key_file);
498 if (ret < 0)
499 return ret;
500 PARA_INFO_LOG("decrypting %d byte input\n", inlen);
501 /* key_file -> asymmetric key priv */
502 ret = get_private_key(key_file, &priv);
503 if (ret < 0)
504 return ret;
505
506 /* asymmetric key priv -> sexp priv_key */
507 ret = -E_SEXP_FIND;
508 priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
509 if (!priv_key)
510 goto free_key;
511
512 /* inbuf -> in_mpi */
513 gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
514 inlen, NULL);
515 if (gret) {
516 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
517 ret = -E_MPI_SCAN;
518 goto key_release;
519 }
520 /* in_mpi -> in sexp */
521 gret = gcry_sexp_build(&in, NULL, RSA_DECRYPT_SEXP, in_mpi);
522 if (gret) {
523 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
524 ret = -E_SEXP_BUILD;
525 goto in_mpi_release;
526 }
527
528 /* rsa decryption: in sexp -> out sexp */
529 gret = gcry_pk_decrypt(&out, in, priv_key);
530 if (gret) {
531 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
532 ret = -E_SEXP_DECRYPT;
533 goto in_release;
534 }
535 ret = decode_rsa(out, outbuf, &nbytes);
536 if (ret < 0)
537 goto out_release;
538 PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
539 ret = nbytes;
540 out_release:
541 gcry_sexp_release(out);
542 in_release:
543 gcry_sexp_release(in);
544 in_mpi_release:
545 gcry_mpi_release(in_mpi);
546 key_release:
547 gcry_sexp_release(priv_key);
548 free_key:
549 gcry_sexp_release(priv->sexp);
550 free(priv);
551 return ret;
552 }
553
554 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
555 unsigned len, unsigned char *outbuf)
556 {
557 gcry_error_t gret;
558 gcry_sexp_t pub_key, in, out, out_a;
559 gcry_mpi_t out_mpi = NULL;
560 size_t nbytes;
561 int ret;
562
563 PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
564
565 /* get pub key */
566 pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
567 if (!pub_key)
568 return -E_SEXP_FIND;
569 gret = gcry_sexp_build(&in, NULL, "(data(flags oaep)(value %b))", len, inbuf);
570 if (gret) {
571 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
572 ret = -E_SEXP_BUILD;
573 goto key_release;
574 }
575 /* rsa sexp encryption: in -> out */
576 gret = gcry_pk_encrypt(&out, in, pub_key);
577 if (gret) {
578 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
579 ret = -E_SEXP_ENCRYPT;
580 goto in_release;
581 }
582 /* extract a, an MPI with the result of the RSA operation */
583 ret = -E_SEXP_FIND;
584 out_a = gcry_sexp_find_token(out, "a", 0);
585 if (!out_a)
586 goto out_release;
587 /* convert sexp out_a -> out_mpi */
588 out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
589 if (!out_mpi) {
590 ret = -E_SEXP_FIND;
591 goto out_a_release;
592 }
593 gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
594 if (gret) {
595 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
596 ret = -E_SEXP_ENCRYPT;
597 goto out_mpi_release;
598 }
599 PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
600 dump_buffer("enc buf", outbuf, nbytes);
601 ret = nbytes;
602
603 out_mpi_release:
604 gcry_mpi_release(out_mpi);
605 out_a_release:
606 gcry_sexp_release(out_a);
607 out_release:
608 gcry_sexp_release(out);
609 in_release:
610 gcry_sexp_release(in);
611 key_release:
612 gcry_sexp_release(pub_key);
613 return ret;
614 }
615
616 struct stream_cipher {
617 gcry_cipher_hd_t handle;
618 };
619
620 struct stream_cipher *sc_new(const unsigned char *data, int len)
621 {
622 gcry_error_t gret;
623 struct stream_cipher *sc = para_malloc(sizeof(*sc));
624
625 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
626 gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_AES128,
627 GCRY_CIPHER_MODE_CTR, 0);
628 assert(gret == 0);
629 gret = gcry_cipher_setkey(sc->handle, data,
630 AES_CRT128_BLOCK_SIZE);
631 assert(gret == 0);
632 gret = gcry_cipher_setctr(sc->handle,
633 data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
634 assert(gret == 0);
635 return sc;
636 }
637
638 void sc_free(struct stream_cipher *sc)
639 {
640 if (!sc)
641 return;
642 gcry_cipher_close(sc->handle);
643 free(sc);
644 }
645
646 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
647 {
648 gcry_cipher_hd_t handle = sc->handle;
649 gcry_error_t gret;
650
651 /* perform in-place encryption */
652 *dst = *src;
653 gret = gcry_cipher_encrypt(handle, src->iov_base, src->iov_len,
654 NULL, 0);
655 assert(gret == 0);
656 }