crypto: Remove support for ASN public keys.
[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 static bool libgcrypt_has_oaep;
23 static const char *rsa_decrypt_sexp;
24
25 #ifdef GCRYPT_DEBUG
26 static void dump_buffer(const char *msg, unsigned char *buf, int len)
27 {
28 int i;
29
30 fprintf(stderr, "%s (%d bytes): ", msg, len);
31 for (i = 0; i < len; i++)
32 fprintf(stderr, "%02x ", buf[i]);
33 fprintf(stderr, "\n");
34 }
35 #else
36 /** Empty. Define GCRYPT_DEBUG to dump buffers. */
37 #define dump_buffer(a, b, c)
38 #endif
39
40 void hash_function(const char *data, unsigned long len, unsigned char *hash)
41 {
42 gcry_error_t gret;
43 gcry_md_hd_t handle;
44 unsigned char *md;
45
46 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
47 assert(gret == 0);
48 gcry_md_write(handle, data, (size_t)len);
49 gcry_md_final(handle);
50 md = gcry_md_read(handle, GCRY_MD_SHA1);
51 assert(md);
52 memcpy(hash, md, HASH_SIZE);
53 gcry_md_close(handle);
54 }
55
56 void get_random_bytes_or_die(unsigned char *buf, int num)
57 {
58 gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
59 }
60
61 /*
62 * This is called at the beginning of every program that uses libgcrypt. We
63 * don't have to initialize any random seed here, but we must initialize the
64 * gcrypt library. This task is performed by gcry_check_version() which can
65 * also check that the gcrypt library version is at least the minimal required
66 * version. This function also tells us whether we have to use our own OAEP
67 * padding code.
68 */
69 void init_random_seed_or_die(void)
70 {
71 const char *ver, *req_ver;
72
73 ver = gcry_check_version(NULL);
74 req_ver = "1.4.0";
75 if (!gcry_check_version(req_ver)) {
76 PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
77 req_ver, ver);
78 exit(EXIT_FAILURE);
79 }
80 req_ver = "1.5.0";
81 if (gcry_check_version(req_ver)) {
82 libgcrypt_has_oaep = true;
83 rsa_decrypt_sexp = "(enc-val(flags oaep)(rsa(a %m)))";
84 } else {
85 libgcrypt_has_oaep = false;
86 rsa_decrypt_sexp = "(enc-val(rsa(a %m)))";
87 }
88 }
89
90 /** S-expression for the public part of an RSA key. */
91 #define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
92 /** S-expression for a private RSA key. */
93 #define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
94
95 /* rfc 3447, appendix B.2 */
96 static void mgf1(unsigned char *seed, size_t seed_len, unsigned result_len,
97 unsigned char *result)
98 {
99 gcry_error_t gret;
100 gcry_md_hd_t handle;
101 size_t n;
102 unsigned char *md;
103 unsigned char octet_string[4], *rp = result, *end = rp + result_len;
104
105 assert(result_len / HASH_SIZE < 1ULL << 31);
106 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
107 assert(gret == 0);
108 for (n = 0; rp < end; n++) {
109 gcry_md_write(handle, seed, seed_len);
110 octet_string[0] = (unsigned char)((n >> 24) & 255);
111 octet_string[1] = (unsigned char)((n >> 16) & 255);
112 octet_string[2] = (unsigned char)((n >> 8)) & 255;
113 octet_string[3] = (unsigned char)(n & 255);
114 gcry_md_write(handle, octet_string, 4);
115 gcry_md_final(handle);
116 md = gcry_md_read(handle, GCRY_MD_SHA1);
117 memcpy(rp, md, PARA_MIN(HASH_SIZE, (int)(end - rp)));
118 rp += HASH_SIZE;
119 gcry_md_reset(handle);
120 }
121 gcry_md_close(handle);
122 }
123
124 /** The sha1 hash of an empty file. */
125 static const unsigned char empty_hash[HASH_SIZE] =
126 "\xda" "\x39" "\xa3" "\xee" "\x5e"
127 "\x6b" "\x4b" "\x0d" "\x32" "\x55"
128 "\xbf" "\xef" "\x95" "\x60" "\x18"
129 "\x90" "\xaf" "\xd8" "\x07" "\x09";
130
131 /* rfc3447, section 7.1.1 */
132 static void pad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
133 size_t out_len)
134 {
135 size_t ps_len = out_len - in_len - 2 * HASH_SIZE - 2;
136 size_t n, mask_len = out_len - HASH_SIZE - 1;
137 unsigned char *seed = out + 1, *db = seed + HASH_SIZE,
138 *ps = db + HASH_SIZE, *one = ps + ps_len;
139 unsigned char *db_mask, seed_mask[HASH_SIZE];
140
141 assert(in_len <= out_len - 2 - 2 * HASH_SIZE);
142 assert(out_len > 2 * HASH_SIZE + 2);
143 PARA_DEBUG_LOG("padding %zu byte input -> %zu byte output\n",
144 in_len, out_len);
145 dump_buffer("unpadded buffer", in, in_len);
146
147 out[0] = '\0';
148 get_random_bytes_or_die(seed, HASH_SIZE);
149 memcpy(db, empty_hash, HASH_SIZE);
150 memset(ps, 0, ps_len);
151 *one = 0x01;
152 memcpy(one + 1, in, in_len);
153 db_mask = para_malloc(mask_len);
154 mgf1(seed, HASH_SIZE, mask_len, db_mask);
155 for (n = 0; n < mask_len; n++)
156 db[n] ^= db_mask[n];
157 mgf1(db, mask_len, HASH_SIZE, seed_mask);
158 for (n = 0; n < HASH_SIZE; n++)
159 seed[n] ^= seed_mask[n];
160 free(db_mask);
161 dump_buffer("padded buffer", out, out_len);
162 }
163
164 /* rfc 3447, section 7.1.2 */
165 static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
166 size_t *out_len)
167 {
168 unsigned char *masked_seed = in + 1;
169 unsigned char *db = in + 1 + HASH_SIZE;
170 unsigned char seed[HASH_SIZE], seed_mask[HASH_SIZE];
171 unsigned char *db_mask, *p;
172 size_t n, mask_len = in_len - HASH_SIZE - 1;
173
174 mgf1(db, mask_len, HASH_SIZE, seed_mask);
175 for (n = 0; n < HASH_SIZE; n++)
176 seed[n] = masked_seed[n] ^ seed_mask[n];
177 db_mask = para_malloc(mask_len);
178 mgf1(seed, HASH_SIZE, mask_len, db_mask);
179 for (n = 0; n < mask_len; n++)
180 db[n] ^= db_mask[n];
181 free(db_mask);
182 if (memcmp(db, empty_hash, HASH_SIZE))
183 return -E_OEAP;
184 for (p = db + HASH_SIZE; p < in + in_len - 1; p++)
185 if (*p != '\0')
186 break;
187 if (p >= in + in_len - 1)
188 return -E_OEAP;
189 p++;
190 *out_len = in + in_len - p;
191 memcpy(out, p, *out_len);
192 return 1;
193 }
194
195 struct asymmetric_key {
196 gcry_sexp_t sexp;
197 int num_bytes;
198 };
199
200 static const char *gcrypt_strerror(gcry_error_t gret)
201 {
202 return gcry_strerror(gcry_err_code(gret));
203 }
204
205 static int decode_key(const char *key_file, const char *header_str,
206 const char *footer_str, unsigned char **result)
207 {
208 int ret, ret2, i, j;
209 void *map;
210 size_t map_size, key_size, blob_size;
211 unsigned char *blob = NULL;
212 char *begin, *footer, *key;
213
214 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
215 if (ret < 0)
216 goto out;
217 ret = -E_KEY_MARKER;
218 if (strncmp(map, header_str, strlen(header_str)))
219 goto unmap;
220 footer = strstr(map, footer_str);
221 ret = -E_KEY_MARKER;
222 if (!footer)
223 goto unmap;
224 begin = map + strlen(header_str);
225 /* skip whitespace at the beginning */
226 for (; begin < footer; begin++) {
227 if (para_isspace(*begin))
228 continue;
229 break;
230 }
231 ret = -E_KEY_MARKER;
232 if (begin >= footer)
233 goto unmap;
234
235 key_size = footer - begin;
236 key = para_malloc(key_size + 1);
237 for (i = 0, j = 0; begin + i < footer; i++) {
238 if (para_isspace(begin[i]))
239 continue;
240 key[j++] = begin[i];
241 }
242 key[j] = '\0';
243 ret = base64_decode(key, j, (char **)&blob, &blob_size);
244 free(key);
245 if (ret < 0)
246 goto free_unmap;
247 ret = blob_size;
248 goto unmap;
249 free_unmap:
250 free(blob);
251 blob = NULL;
252 unmap:
253 ret2 = para_munmap(map, map_size);
254 if (ret >= 0 && ret2 < 0)
255 ret = ret2;
256 if (ret < 0) {
257 free(blob);
258 blob = NULL;
259 }
260 out:
261 *result = blob;
262 return ret;
263 }
264
265 /** ASN Types and their code. */
266 enum asn1_types {
267 /** The next object is an integer. */
268 ASN1_TYPE_INTEGER = 0x2,
269 /** Bit string object. */
270 ASN1_TYPE_BIT_STRING = 0x03,
271 /** Keys start with one big type sequence. */
272 ASN1_TYPE_SEQUENCE = 0x30,
273 };
274
275 /* bit 6 has value 0 */
276 static inline bool is_primitive(unsigned char c)
277 {
278 return (c & (1<<6)) == 0;
279 }
280
281 static inline bool is_primitive_integer(unsigned char c)
282 {
283 if (!is_primitive(c))
284 return false;
285 return (c & 0x1f) == ASN1_TYPE_INTEGER;
286 }
287
288 /* Bit 8 is zero (and bits 7-1 give the length) */
289 static inline bool is_short_form(unsigned char c)
290 {
291 return (c & 0x80) == 0;
292 }
293
294 static inline int get_short_form_length(unsigned char c)
295 {
296 return c & 0x7f;
297 }
298
299 static inline int get_long_form_num_length_bytes(unsigned char c)
300 {
301 return c & 0x7f;
302 }
303
304 /*
305 * Returns: Number of bytes scanned. This may differ from the value returned via
306 * bn_bytes because the latter does not include the ASN.1 prefix and a leading
307 * zero is not considered as an additional byte for bn_bytes.
308 */
309 static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
310 int *bn_bytes)
311 {
312 int i, bn_size;
313 gcry_error_t gret;
314 unsigned char *cp = start;
315
316 if (!is_primitive_integer(*cp))
317 return -E_BAD_PRIVATE_KEY;
318 cp++;
319 if (is_short_form(*cp)) {
320 bn_size = get_short_form_length(*cp);
321 cp++;
322 } else {
323 int num_bytes = get_long_form_num_length_bytes(*cp);
324 if (cp + num_bytes > end)
325 return -E_BAD_PRIVATE_KEY;
326 if (num_bytes > 4) /* nobody has such a large modulus */
327 return -E_BAD_PRIVATE_KEY;
328 cp++;
329 bn_size = 0;
330 for (i = 0; i < num_bytes; i++, cp++)
331 bn_size = (bn_size << 8) + *cp;
332 }
333 PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, (unsigned)bn_size);
334 gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
335 if (gret) {
336 PARA_ERROR_LOG("%s while scanning n\n",
337 gcry_strerror(gcry_err_code(gret)));
338 return-E_MPI_SCAN;
339 }
340 /*
341 * Don't take the first leading zero into account for the size of the
342 * bignum.
343 */
344 if (*cp == '\0') {
345 cp++;
346 bn_size--;
347 }
348 if (bn_bytes)
349 *bn_bytes = bn_size;
350 cp += bn_size;
351 // unsigned char *buf;
352 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
353 // PARA_CRIT_LOG("bn: %s\n", buf);
354 return cp - start;
355 }
356
357 static int find_privkey_bignum_offset(const unsigned char *data, int len)
358 {
359 const unsigned char *p = data, *end = data + len;
360
361 /* like the public key, the whole thing is contained in a sequence */
362 if (*p != ASN1_TYPE_SEQUENCE)
363 return -E_ASN1_PARSE;
364 p++;
365 if (p >= end)
366 return -E_ASN1_PARSE;
367 if (is_short_form(*p))
368 p++;
369 else
370 p += 1 + get_long_form_num_length_bytes(*p);
371 if (p >= end)
372 return -E_ASN1_PARSE;
373
374 /* skip next integer */
375 if (*p != ASN1_TYPE_INTEGER)
376 return -E_ASN1_PARSE;
377 p++;
378 if (p >= end)
379 return -E_ASN1_PARSE;
380 if (is_short_form(*p))
381 p += 1 + get_short_form_length(*p);
382 else
383 p += 1 + get_long_form_num_length_bytes(*p);
384 if (p >= end)
385 return -E_ASN1_PARSE;
386 return p - data;
387 }
388
389 /** Private keys start with this header. */
390 #define PRIVATE_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
391 /** Private keys end with this footer. */
392 #define PRIVATE_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
393
394 static int get_private_key(const char *key_file, struct asymmetric_key **result)
395 {
396 gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
397 u = NULL;
398 unsigned char *blob, *cp, *end;
399 int blob_size, ret, n_size;
400 gcry_error_t gret;
401 size_t erroff;
402 gcry_sexp_t sexp;
403 struct asymmetric_key *key;
404
405 *result = NULL;
406 ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
407 &blob);
408 if (ret < 0)
409 return ret;
410 blob_size = ret;
411 end = blob + blob_size;
412 ret = find_privkey_bignum_offset(blob, blob_size);
413 if (ret < 0)
414 goto free_blob;
415 PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
416 cp = blob + ret;
417
418 ret = read_bignum(cp, end, &n, &n_size);
419 if (ret < 0)
420 goto free_blob;
421 cp += ret;
422
423 ret = read_bignum(cp, end, &e, NULL);
424 if (ret < 0)
425 goto release_n;
426 cp += ret;
427
428 ret = read_bignum(cp, end, &d, NULL);
429 if (ret < 0)
430 goto release_e;
431 cp += ret;
432
433 ret = read_bignum(cp, end, &p, NULL);
434 if (ret < 0)
435 goto release_d;
436 cp += ret;
437
438 ret = read_bignum(cp, end, &q, NULL);
439 if (ret < 0)
440 goto release_p;
441 cp += ret;
442 ret = read_bignum(cp, end, &u, NULL);
443 if (ret < 0)
444 goto release_q;
445 /*
446 * OpenSSL uses slightly different parameters than gcrypt. To use these
447 * parameters we need to swap the values of p and q and recompute u.
448 */
449 if (gcry_mpi_cmp(p, q) > 0) {
450 gcry_mpi_swap(p, q);
451 gcry_mpi_invm(u, p, q);
452 }
453 gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
454 n, e, d, p, q, u);
455
456 if (gret) {
457 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
458 gcry_strerror(gcry_err_code(gret)));
459 ret = -E_SEXP_BUILD;
460 goto release_u;
461 }
462 key = para_malloc(sizeof(*key));
463 key->sexp = sexp;
464 *result = key;
465 ret = n_size * 8;
466 PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
467 release_u:
468 gcry_mpi_release(u);
469 release_q:
470 gcry_mpi_release(q);
471 release_p:
472 gcry_mpi_release(p);
473 release_d:
474 gcry_mpi_release(d);
475 release_e:
476 gcry_mpi_release(e);
477 release_n:
478 gcry_mpi_release(n);
479 free_blob:
480 free(blob);
481 return ret;
482 }
483
484 static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
485 {
486 int ret;
487 gcry_error_t gret;
488 unsigned char *blob = NULL, *p, *end;
489 size_t nr_scanned, erroff, decoded_size;
490 gcry_mpi_t e = NULL, n = NULL;
491
492 PARA_DEBUG_LOG("decoding %d byte public rsa-ssh key\n", size);
493 ret = uudecode((char *)data, size, (char **)&blob, &decoded_size);
494 if (ret < 0)
495 goto free_blob;
496 end = blob + decoded_size;
497 dump_buffer("decoded key", blob, decoded_size);
498 ret = check_ssh_key_header(blob, decoded_size);
499 if (ret < 0)
500 goto free_blob;
501 p = blob + ret;
502 ret = -E_SSH_PARSE;
503 if (p >= end)
504 goto free_blob;
505 PARA_DEBUG_LOG("scanning modulus and public exponent\n");
506 gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
507 if (gret) {
508 ret = -E_MPI_SCAN;
509 PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
510 goto free_blob;
511 }
512 PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
513 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_e);
514 // PARA_CRIT_LOG("e: %s\n", buf);
515 p += nr_scanned;
516 if (p >= end)
517 goto release_e;
518 gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
519 if (gret) {
520 ret = -E_MPI_SCAN;
521 PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
522 goto release_e;
523 }
524 PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
525 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_n);
526 // PARA_CRIT_LOG("n: %s\n", buf);
527 gret = gcry_sexp_build(result, &erroff, RSA_PUBKEY_SEXP, n, e);
528 if (gret) {
529 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
530 gcry_strerror(gcry_err_code(gret)));
531 ret = -E_SEXP_BUILD;
532 goto release_n;
533 }
534 ret = nr_scanned / 32 * 32;
535 PARA_INFO_LOG("successfully read %d bit ssh public key\n", ret * 8);
536 release_n:
537 gcry_mpi_release(n);
538 release_e:
539 gcry_mpi_release(e);
540 free_blob:
541 free(blob);
542 return ret;
543 }
544
545 int get_public_key(const char *key_file, struct asymmetric_key **result)
546 {
547 int ret, ret2;
548 void *map;
549 size_t map_size;
550 unsigned char *start, *end;
551 gcry_sexp_t sexp;
552 struct asymmetric_key *key;
553
554 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
555 if (ret < 0)
556 return ret;
557 ret = is_ssh_rsa_key(map, map_size);
558 if (!ret) {
559 para_munmap(map, map_size);
560 return -E_SSH_PARSE;
561 }
562 start = map + ret;
563 end = map + map_size;
564 ret = -E_SSH_PARSE;
565 if (start >= end)
566 goto unmap;
567 ret = get_ssh_public_key(start, end - start, &sexp);
568 if (ret < 0)
569 goto unmap;
570 key = para_malloc(sizeof(*key));
571 key->num_bytes = ret;
572 key->sexp = sexp;
573 *result = key;
574 unmap:
575 ret2 = para_munmap(map, map_size);
576 if (ret >= 0 && ret2 < 0)
577 ret = ret2;
578 return ret;
579 }
580
581 void free_public_key(struct asymmetric_key *key)
582 {
583 if (!key)
584 return;
585 gcry_sexp_release(key->sexp);
586 free(key);
587 }
588
589 static int decode_rsa(gcry_sexp_t sexp, int key_size, unsigned char *outbuf,
590 size_t *nbytes)
591 {
592 int ret;
593 gcry_error_t gret;
594 unsigned char oaep_buf[512];
595 gcry_mpi_t out_mpi;
596
597 if (libgcrypt_has_oaep) {
598 const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
599
600 if (!p) {
601 PARA_ERROR_LOG("could not get data from list\n");
602 return -E_OEAP;
603 }
604 memcpy(outbuf, p, *nbytes);
605 return 1;
606 }
607 out_mpi = gcry_sexp_nth_mpi(sexp, 0, GCRYMPI_FMT_USG);
608 if (!out_mpi)
609 return -E_SEXP_FIND;
610 gret = gcry_mpi_print(GCRYMPI_FMT_USG, oaep_buf, sizeof(oaep_buf),
611 nbytes, out_mpi);
612 if (gret) {
613 PARA_ERROR_LOG("mpi_print: %s\n", gcrypt_strerror(gret));
614 ret = -E_MPI_PRINT;
615 goto out_mpi_release;
616 }
617 /*
618 * An oaep-encoded buffer always starts with at least one zero byte.
619 * However, leading zeroes in an mpi are omitted in the output of
620 * gcry_mpi_print() when using the GCRYMPI_FMT_USG format. The
621 * alternative, GCRYMPI_FMT_STD, does not work either because here the
622 * leading zero(es) might also be omitted, depending on the value of
623 * the second byte.
624 *
625 * To circumvent this, we shift the oaep buffer to the right. But first
626 * we check that the buffer actually started with a zero byte, i.e. that
627 * nbytes < key_size. Otherwise a decoding error occurred.
628 */
629 ret = -E_SEXP_DECRYPT;
630 if (*nbytes >= key_size)
631 goto out_mpi_release;
632 memmove(oaep_buf + key_size - *nbytes, oaep_buf, *nbytes);
633 memset(oaep_buf, 0, key_size - *nbytes);
634
635 PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
636 key_size);
637 dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);
638 ret = unpad_oaep(oaep_buf, key_size, outbuf, nbytes);
639 if (ret < 0)
640 goto out_mpi_release;
641 PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
642 *nbytes);
643 dump_buffer("unpadded decrypted buffer", outbuf, *nbytes);
644 ret = 1;
645 out_mpi_release:
646 gcry_mpi_release(out_mpi);
647 return ret;
648 }
649
650 int priv_decrypt(const char *key_file, unsigned char *outbuf,
651 unsigned char *inbuf, int inlen)
652 {
653 gcry_error_t gret;
654 int ret, key_size;
655 struct asymmetric_key *priv;
656 gcry_mpi_t in_mpi = NULL;
657 gcry_sexp_t in, out, priv_key;
658 size_t nbytes;
659
660 ret = check_private_key_file(key_file);
661 if (ret < 0)
662 return ret;
663 PARA_INFO_LOG("decrypting %d byte input\n", inlen);
664 /* key_file -> asymmetric key priv */
665 ret = get_private_key(key_file, &priv);
666 if (ret < 0)
667 return ret;
668 key_size = ret / 8;
669
670 /* asymmetric key priv -> sexp priv_key */
671 ret = -E_SEXP_FIND;
672 priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
673 if (!priv_key)
674 goto free_key;
675
676 /* inbuf -> in_mpi */
677 gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
678 inlen, NULL);
679 if (gret) {
680 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
681 ret = -E_MPI_SCAN;
682 goto key_release;
683 }
684 /* in_mpi -> in sexp */
685 gret = gcry_sexp_build(&in, NULL, rsa_decrypt_sexp, in_mpi);
686 if (gret) {
687 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
688 ret = -E_SEXP_BUILD;
689 goto in_mpi_release;
690 }
691
692 /* rsa decryption: in sexp -> out sexp */
693 gret = gcry_pk_decrypt(&out, in, priv_key);
694 if (gret) {
695 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
696 ret = -E_SEXP_DECRYPT;
697 goto in_release;
698 }
699 ret = decode_rsa(out, key_size, outbuf, &nbytes);
700 if (ret < 0)
701 goto out_release;
702 PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
703 ret = nbytes;
704 out_release:
705 gcry_sexp_release(out);
706 in_release:
707 gcry_sexp_release(in);
708 in_mpi_release:
709 gcry_mpi_release(in_mpi);
710 key_release:
711 gcry_sexp_release(priv_key);
712 free_key:
713 gcry_sexp_release(priv->sexp);
714 free(priv);
715 return ret;
716 }
717
718 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
719 unsigned len, unsigned char *outbuf)
720 {
721 gcry_error_t gret;
722 gcry_sexp_t pub_key, in, out, out_a;
723 gcry_mpi_t out_mpi = NULL;
724 size_t nbytes;
725 int ret;
726
727 PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
728
729 /* get pub key */
730 pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
731 if (!pub_key)
732 return -E_SEXP_FIND;
733 if (libgcrypt_has_oaep) {
734 gret = gcry_sexp_build(&in, NULL,
735 "(data(flags oaep)(value %b))", len, inbuf);
736 } else {
737 unsigned char padded_input[256];
738 const size_t pad_size = 256;
739 /* inbuf -> padded inbuf */
740 pad_oaep(inbuf, len, padded_input, pad_size);
741 /* padded inbuf -> in sexp */
742 gret = gcry_sexp_build(&in, NULL,
743 "(data(flags raw)(value %b))", pad_size, padded_input);
744 }
745 if (gret) {
746 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
747 ret = -E_SEXP_BUILD;
748 goto key_release;
749 }
750 /* rsa sexp encryption: in -> out */
751 gret = gcry_pk_encrypt(&out, in, pub_key);
752 if (gret) {
753 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
754 ret = -E_SEXP_ENCRYPT;
755 goto in_release;
756 }
757 /* extract a, an MPI with the result of the RSA operation */
758 ret = -E_SEXP_FIND;
759 out_a = gcry_sexp_find_token(out, "a", 0);
760 if (!out_a)
761 goto out_release;
762 /* convert sexp out_a -> out_mpi */
763 out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
764 if (!out_mpi) {
765 ret = -E_SEXP_FIND;
766 goto out_a_release;
767 }
768 gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
769 if (gret) {
770 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
771 ret = -E_SEXP_ENCRYPT;
772 goto out_mpi_release;
773 }
774 PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
775 dump_buffer("enc buf", outbuf, nbytes);
776 ret = nbytes;
777
778 out_mpi_release:
779 gcry_mpi_release(out_mpi);
780 out_a_release:
781 gcry_sexp_release(out_a);
782 out_release:
783 gcry_sexp_release(out);
784 in_release:
785 gcry_sexp_release(in);
786 key_release:
787 gcry_sexp_release(pub_key);
788 return ret;
789 }
790
791 struct stream_cipher {
792 gcry_cipher_hd_t handle;
793 };
794
795 struct stream_cipher *sc_new(const unsigned char *data, int len,
796 bool use_aes)
797 {
798 gcry_error_t gret;
799 struct stream_cipher *sc = para_malloc(sizeof(*sc));
800
801 if (use_aes) {
802 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
803 gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_AES128,
804 GCRY_CIPHER_MODE_CTR, 0);
805 assert(gret == 0);
806 gret = gcry_cipher_setkey(sc->handle, data,
807 AES_CRT128_BLOCK_SIZE);
808 assert(gret == 0);
809 gret = gcry_cipher_setctr(sc->handle,
810 data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
811 assert(gret == 0);
812 return sc;
813 }
814 gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_ARCFOUR,
815 GCRY_CIPHER_MODE_STREAM, 0);
816 if (gret) {
817 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
818 free(sc);
819 return NULL;
820 }
821 gret = gcry_cipher_setkey(sc->handle, data, (size_t)len);
822 assert(gret == 0);
823 return sc;
824 }
825
826 void sc_free(struct stream_cipher *sc)
827 {
828 if (!sc)
829 return;
830 gcry_cipher_close(sc->handle);
831 free(sc);
832 }
833
834 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
835 {
836 gcry_cipher_hd_t handle = sc->handle;
837 gcry_error_t gret;
838
839 /* perform in-place encryption */
840 *dst = *src;
841 gret = gcry_cipher_encrypt(handle, src->iov_base, src->iov_len,
842 NULL, 0);
843 assert(gret == 0);
844 }