Merge branch 't/audioc_cleanups'
[paraslash.git] / gcrypt.c
1 /*
2 * Copyright (C) 2011-2012 Andre Noll <maan@systemlinux.org>
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
19 //#define GCRYPT_DEBUG 1
20
21 static bool libgcrypt_has_oaep;
22 static const char *rsa_decrypt_sexp;
23
24 #ifdef GCRYPT_DEBUG
25 static void dump_buffer(const char *msg, unsigned char *buf, int len)
26 {
27 int i;
28
29 fprintf(stderr, "%s (%u bytes): ", msg, len);
30 for (i = 0; i < len; i++)
31 fprintf(stderr, "%02x ", buf[i]);
32 fprintf(stderr, "\n");
33 }
34 #else
35 /** Empty. Define GCRYPT_DEBUG to dump buffers. */
36 #define dump_buffer(a, b, c)
37 #endif
38
39 void hash_function(const char *data, unsigned long len, unsigned char *hash)
40 {
41 gcry_error_t gret;
42 gcry_md_hd_t handle;
43 unsigned char *md;
44
45 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
46 assert(gret == 0);
47 gcry_md_write(handle, data, (size_t)len);
48 gcry_md_final(handle);
49 md = gcry_md_read(handle, GCRY_MD_SHA1);
50 assert(md);
51 memcpy(hash, md, HASH_SIZE);
52 gcry_md_close(handle);
53 }
54
55 void get_random_bytes_or_die(unsigned char *buf, int num)
56 {
57 gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
58 }
59
60 /*
61 * This is called at the beginning of every program that uses libgcrypt. We
62 * don't have to initialize any random seed here, but we must initialize the
63 * gcrypt library. This task is performed by gcry_check_version() which can
64 * also check that the gcrypt library version is at least the minimal required
65 * version. This function also tells us whether we have to use our own OAEP
66 * padding code.
67 */
68 void init_random_seed_or_die(void)
69 {
70 const char *ver, *req_ver;
71
72 ver = gcry_check_version(NULL);
73 req_ver = "1.4.0";
74 if (!gcry_check_version(req_ver)) {
75 PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
76 req_ver, ver);
77 exit(EXIT_FAILURE);
78 }
79 req_ver = "1.5.0";
80 if (gcry_check_version(req_ver)) {
81 libgcrypt_has_oaep = true;
82 rsa_decrypt_sexp = "(enc-val(flags oaep)(rsa(a %m)))";
83 } else {
84 libgcrypt_has_oaep = false;
85 rsa_decrypt_sexp = "(enc-val(rsa(a %m)))";
86 }
87 }
88
89 /** S-expression for the public part of an RSA key. */
90 #define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
91 /** S-expression for a private RSA key. */
92 #define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
93
94 /* rfc 3447, appendix B.2 */
95 static void mgf1(unsigned char *seed, size_t seed_len, unsigned result_len,
96 unsigned char *result)
97 {
98 gcry_error_t gret;
99 gcry_md_hd_t handle;
100 size_t n;;
101 unsigned char *md;
102 unsigned char octet_string[4], *rp = result, *end = rp + result_len;
103
104 assert(result_len / HASH_SIZE < 1ULL << 31);
105 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
106 assert(gret == 0);
107 for (n = 0; rp < end; n++) {
108 gcry_md_write(handle, seed, seed_len);
109 octet_string[0] = (unsigned char)((n >> 24) & 255);
110 octet_string[1] = (unsigned char)((n >> 16) & 255);
111 octet_string[2] = (unsigned char)((n >> 8)) & 255;
112 octet_string[3] = (unsigned char)(n & 255);
113 gcry_md_write(handle, octet_string, 4);
114 gcry_md_final(handle);
115 md = gcry_md_read(handle, GCRY_MD_SHA1);
116 memcpy(rp, md, PARA_MIN(HASH_SIZE, (int)(end - rp)));
117 rp += HASH_SIZE;
118 gcry_md_reset(handle);
119 }
120 gcry_md_close(handle);
121 }
122
123 /** The sha1 hash of an empty file. */
124 static const unsigned char empty_hash[HASH_SIZE] =
125 "\xda" "\x39" "\xa3" "\xee" "\x5e"
126 "\x6b" "\x4b" "\x0d" "\x32" "\x55"
127 "\xbf" "\xef" "\x95" "\x60" "\x18"
128 "\x90" "\xaf" "\xd8" "\x07" "\x09";
129
130 /* rfc3447, section 7.1.1 */
131 static void pad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
132 size_t out_len)
133 {
134 size_t ps_len = out_len - in_len - 2 * HASH_SIZE - 2;
135 size_t n, mask_len = out_len - HASH_SIZE - 1;
136 unsigned char *seed = out + 1, *db = seed + HASH_SIZE,
137 *ps = db + HASH_SIZE, *one = ps + ps_len;
138 unsigned char *db_mask, seed_mask[HASH_SIZE];
139
140 assert(in_len <= out_len - 2 - 2 * HASH_SIZE);
141 assert(out_len > 2 * HASH_SIZE + 2);
142 PARA_DEBUG_LOG("padding %zu byte input -> %zu byte output\n",
143 in_len, out_len);
144 dump_buffer("unpadded buffer", in, in_len);
145
146 out[0] = '\0';
147 get_random_bytes_or_die(seed, HASH_SIZE);
148 memcpy(db, empty_hash, HASH_SIZE);
149 memset(ps, 0, ps_len);
150 *one = 0x01;
151 memcpy(one + 1, in, in_len);
152 db_mask = para_malloc(mask_len);
153 mgf1(seed, HASH_SIZE, mask_len, db_mask);
154 for (n = 0; n < mask_len; n++)
155 db[n] ^= db_mask[n];
156 mgf1(db, mask_len, HASH_SIZE, seed_mask);
157 for (n = 0; n < HASH_SIZE; n++)
158 seed[n] ^= seed_mask[n];
159 free(db_mask);
160 dump_buffer("padded buffer", out, out_len);
161 }
162
163 /* rfc 3447, section 7.1.2 */
164 static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
165 size_t *out_len)
166 {
167 unsigned char *masked_seed = in + 1;
168 unsigned char *db = in + 1 + HASH_SIZE;
169 unsigned char seed[HASH_SIZE], seed_mask[HASH_SIZE];
170 unsigned char *db_mask, *p;
171 size_t n, mask_len = in_len - HASH_SIZE - 1;
172
173 mgf1(db, mask_len, HASH_SIZE, seed_mask);
174 for (n = 0; n < HASH_SIZE; n++)
175 seed[n] = masked_seed[n] ^ seed_mask[n];
176 db_mask = para_malloc(mask_len);
177 mgf1(seed, HASH_SIZE, mask_len, db_mask);
178 for (n = 0; n < mask_len; n++)
179 db[n] ^= db_mask[n];
180 free(db_mask);
181 if (memcmp(db, empty_hash, HASH_SIZE))
182 return -E_OEAP;
183 for (p = db + HASH_SIZE; p < in + in_len - 1; p++)
184 if (*p != '\0')
185 break;
186 if (p >= in + in_len - 1)
187 return -E_OEAP;
188 p++;
189 *out_len = in + in_len - p;
190 memcpy(out, p, *out_len);
191 return 1;
192 }
193
194 struct asymmetric_key {
195 gcry_sexp_t sexp;
196 int num_bytes;
197 };
198
199 static const char *gcrypt_strerror(gcry_error_t gret)
200 {
201 return gcry_strerror(gcry_err_code(gret));
202 }
203
204 static int decode_key(const char *key_file, const char *header_str,
205 const char *footer_str, unsigned char **result)
206 {
207 int ret, ret2, i, j;
208 void *map;
209 size_t map_size, key_size, blob_size;
210 unsigned char *blob = NULL;
211 char *begin, *footer, *key;
212
213 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
214 if (ret < 0)
215 return ret;
216 ret = -E_KEY_MARKER;
217 if (strncmp(map, header_str, strlen(header_str)))
218 goto unmap;
219 footer = strstr(map, footer_str);
220 ret = -E_KEY_MARKER;
221 if (!footer)
222 goto unmap;
223 begin = map + strlen(header_str);
224 /* skip whitespace at the beginning */
225 for (; begin < footer; begin++) {
226 if (para_isspace(*begin))
227 continue;
228 break;
229 }
230 ret = -E_KEY_MARKER;
231 if (begin >= footer)
232 goto unmap;
233
234 key_size = footer - begin;
235 key = para_malloc(key_size + 1);
236 for (i = 0, j = 0; begin + i < footer; i++) {
237 if (para_isspace(begin[i]))
238 continue;
239 key[j++] = begin[i];
240 }
241 key[j] = '\0';
242 //PARA_CRIT_LOG("key: %s\n", key);
243 blob_size = key_size * 2;
244 blob = para_malloc(blob_size);
245 ret = base64_decode(key, blob, blob_size);
246 free(key);
247 if (ret < 0)
248 goto free_unmap;
249 goto unmap;
250 free_unmap:
251 free(blob);
252 blob = NULL;
253 unmap:
254 ret2 = para_munmap(map, map_size);
255 if (ret >= 0 && ret2 < 0)
256 ret = ret2;
257 if (ret < 0) {
258 free(blob);
259 blob = NULL;
260 }
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 static int find_pubkey_bignum_offset(const unsigned char *data, int len)
305 {
306 const unsigned char *p = data, *end = data + len;
307
308 /* the whole thing istarts with one sequence */
309 if (*p != ASN1_TYPE_SEQUENCE)
310 return -E_ASN1_PARSE;
311 p++;
312 if (p >= end)
313 return -E_ASN1_PARSE;
314 if (is_short_form(*p))
315 p++;
316 else
317 p += 1 + get_long_form_num_length_bytes(*p);
318 if (p >= end)
319 return -E_ASN1_PARSE;
320 /* another sequence containing the object id, skip it */
321 if (*p != ASN1_TYPE_SEQUENCE)
322 return -E_ASN1_PARSE;
323 p++;
324 if (p >= end)
325 return -E_ASN1_PARSE;
326 if (!is_short_form(*p))
327 return -E_ASN1_PARSE;
328 p += 1 + get_short_form_length(*p);
329 if (p >= end)
330 return -E_ASN1_PARSE;
331 /* all numbers are wrapped in a bit string object that follows */
332 if (*p != ASN1_TYPE_BIT_STRING)
333 return -E_ASN1_PARSE;
334 p++;
335 if (p >= end)
336 return -E_ASN1_PARSE;
337 if (is_short_form(*p))
338 p++;
339 else
340 p += 1 + get_long_form_num_length_bytes(*p);
341 p++; /* skip number of unused bits in the bit string */
342 if (p >= end)
343 return -E_ASN1_PARSE;
344
345 /* next, we have a sequence of two integers (n and e) */
346 if (*p != ASN1_TYPE_SEQUENCE)
347 return -E_ASN1_PARSE;
348 p++;
349 if (p >= end)
350 return -E_ASN1_PARSE;
351 if (is_short_form(*p))
352 p++;
353 else
354 p += 1 + get_long_form_num_length_bytes(*p);
355 if (p >= end)
356 return -E_ASN1_PARSE;
357 if (*p != ASN1_TYPE_INTEGER)
358 return -E_ASN1_PARSE;
359 return p - data;
360 }
361
362 /*
363 * Returns: Number of bytes scanned. This may differ from the value returned via
364 * bn_bytes because the latter does not include the ASN.1 prefix and a leading
365 * zero is not considered as an additional byte for bn_bytes.
366 */
367 static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
368 int *bn_bytes)
369 {
370 int i, bn_size;
371 gcry_error_t gret;
372 unsigned char *cp = start;
373
374 if (!is_primitive_integer(*cp))
375 return -E_BAD_PRIVATE_KEY;
376 cp++;
377 if (is_short_form(*cp)) {
378 bn_size = get_short_form_length(*cp);
379 cp++;
380 } else {
381 int num_bytes = get_long_form_num_length_bytes(*cp);
382 if (cp + num_bytes > end)
383 return -E_BAD_PRIVATE_KEY;
384 if (num_bytes > 4) /* nobody has such a large modulus */
385 return -E_BAD_PRIVATE_KEY;
386 cp++;
387 bn_size = 0;
388 for (i = 0; i < num_bytes; i++, cp++)
389 bn_size = (bn_size << 8) + *cp;
390 }
391 PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, bn_size);
392 gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
393 if (gret) {
394 PARA_ERROR_LOG("%s while scanning n\n",
395 gcry_strerror(gcry_err_code(gret)));
396 return-E_MPI_SCAN;
397 }
398 /*
399 * Don't take the first leading zero into account for the size of the
400 * bignum.
401 */
402 if (*cp == '\0') {
403 cp++;
404 bn_size--;
405 }
406 if (bn_bytes)
407 *bn_bytes = bn_size;
408 cp += bn_size;
409 // unsigned char *buf;
410 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
411 // PARA_CRIT_LOG("bn: %s\n", buf);
412 return cp - start;
413 }
414
415 static int find_privkey_bignum_offset(const unsigned char *data, int len)
416 {
417 const unsigned char *p = data, *end = data + len;
418
419 /* like the public key, the whole thing is contained in a sequence */
420 if (*p != ASN1_TYPE_SEQUENCE)
421 return -E_ASN1_PARSE;
422 p++;
423 if (p >= end)
424 return -E_ASN1_PARSE;
425 if (is_short_form(*p))
426 p++;
427 else
428 p += 1 + get_long_form_num_length_bytes(*p);
429 if (p >= end)
430 return -E_ASN1_PARSE;
431
432 /* Skip next integer */
433 if (*p != ASN1_TYPE_INTEGER)
434 return -E_ASN1_PARSE;
435 p++;
436 if (p >= end)
437 return -E_ASN1_PARSE;
438 if (is_short_form(*p))
439 p += 1 + get_short_form_length(*p);
440 else
441 p += 1 + get_long_form_num_length_bytes(*p);
442 if (p >= end)
443 return -E_ASN1_PARSE;
444 return p - data;
445 }
446
447 /** Private keys start with this header. */
448 #define PRIVATE_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
449 /** Private keys end with this footer. */
450 #define PRIVATE_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
451
452 static int get_private_key(const char *key_file, struct asymmetric_key **result)
453 {
454 gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
455 u = NULL;
456 unsigned char *blob, *cp, *end;
457 int blob_size, ret, n_size;
458 gcry_error_t gret;
459 size_t erroff;
460 gcry_sexp_t sexp;
461 struct asymmetric_key *key;
462
463 ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
464 &blob);
465 if (ret < 0)
466 return ret;
467 blob_size = ret;
468 end = blob + blob_size;
469 ret = find_privkey_bignum_offset(blob, blob_size);
470 if (ret < 0)
471 goto free_blob;
472 PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
473 cp = blob + ret;
474
475 ret = read_bignum(cp, end, &n, &n_size);
476 if (ret < 0)
477 goto free_blob;
478 cp += ret;
479
480 ret = read_bignum(cp, end, &e, NULL);
481 if (ret < 0)
482 goto release_n;
483 cp += ret;
484
485 ret = read_bignum(cp, end, &d, NULL);
486 if (ret < 0)
487 goto release_e;
488 cp += ret;
489
490 ret = read_bignum(cp, end, &p, NULL);
491 if (ret < 0)
492 goto release_d;
493 cp += ret;
494
495 ret = read_bignum(cp, end, &q, NULL);
496 if (ret < 0)
497 goto release_p;
498 cp += ret;
499 ret = read_bignum(cp, end, &u, NULL);
500 if (ret < 0)
501 goto release_q;
502 cp += ret;
503 /*
504 * OpenSSL uses slightly different parameters than gcrypt. To use these
505 * parameters we need to swap the values of p and q and recompute u.
506 */
507 if (gcry_mpi_cmp(p, q) > 0) {
508 gcry_mpi_swap(p, q);
509 gcry_mpi_invm(u, p, q);
510 }
511 gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
512 n, e, d, p, q, u);
513
514 if (gret) {
515 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
516 gcry_strerror(gcry_err_code(gret)));
517 ret = -E_SEXP_BUILD;
518 goto release_u;
519 }
520 key = para_malloc(sizeof(*key));
521 key->sexp = sexp;
522 *result = key;
523 ret = n_size * 8;
524 PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
525 release_u:
526 gcry_mpi_release(u);
527 release_q:
528 gcry_mpi_release(q);
529 release_p:
530 gcry_mpi_release(p);
531 release_d:
532 gcry_mpi_release(d);
533 release_e:
534 gcry_mpi_release(e);
535 release_n:
536 gcry_mpi_release(n);
537 free_blob:
538 free(blob);
539 return ret;
540 }
541
542 /** Public keys start with this header. */
543 #define PUBLIC_KEY_HEADER "-----BEGIN PUBLIC KEY-----"
544 /** Public keys end with this footer. */
545 #define PUBLIC_KEY_FOOTER "-----END PUBLIC KEY-----"
546
547 static int get_asn_public_key(const char *key_file, struct asymmetric_key **result)
548 {
549 gcry_mpi_t n = NULL, e = NULL;
550 unsigned char *blob, *cp, *end;
551 int blob_size, ret, n_size;
552 gcry_error_t gret;
553 size_t erroff;
554 gcry_sexp_t sexp;
555 struct asymmetric_key *key;
556
557 ret = decode_key(key_file, PUBLIC_KEY_HEADER, PUBLIC_KEY_FOOTER,
558 &blob);
559 if (ret < 0)
560 return ret;
561 blob_size = ret;
562 end = blob + blob_size;
563 ret = find_pubkey_bignum_offset(blob, blob_size);
564 if (ret < 0)
565 goto free_blob;
566 PARA_DEBUG_LOG("decoding public RSA params at offset %d\n", ret);
567 cp = blob + ret;
568
569 ret = read_bignum(cp, end, &n, &n_size);
570 if (ret < 0)
571 goto free_blob;
572 cp += ret;
573
574 ret = read_bignum(cp, end, &e, NULL);
575 if (ret < 0)
576 goto release_n;
577 cp += ret;
578
579 gret = gcry_sexp_build(&sexp, &erroff, RSA_PUBKEY_SEXP, n, e);
580 if (gret) {
581 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
582 gcry_strerror(gcry_err_code(gret)));
583 ret = -E_SEXP_BUILD;
584 goto release_e;
585 }
586 key = para_malloc(sizeof(*key));
587 key->sexp = sexp;
588 *result = key;
589 ret = n_size;
590 PARA_INFO_LOG("successfully read %u bit asn public key\n", n_size * 8);
591
592 release_e:
593 gcry_mpi_release(e);
594 release_n:
595 gcry_mpi_release(n);
596 free_blob:
597 free(blob);
598 return ret;
599 }
600
601 static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
602 {
603 int ret;
604 gcry_error_t gret;
605 unsigned char *blob = NULL, *p, *end;
606 size_t nr_scanned, erroff, decoded_size;
607 gcry_mpi_t e = NULL, n = NULL;
608
609 PARA_DEBUG_LOG("decoding %d byte public rsa-ssh key\n", size);
610 if (size > INT_MAX / 4)
611 return -ERRNO_TO_PARA_ERROR(EOVERFLOW);
612 blob = para_malloc(2 * size);
613 ret = uudecode((char *)data, blob, 2 * size);
614 if (ret < 0)
615 goto free_blob;
616 decoded_size = ret;
617 end = blob + decoded_size;
618 dump_buffer("decoded key", blob, decoded_size);
619 ret = check_ssh_key_header(blob, decoded_size);
620 if (ret < 0)
621 goto free_blob;
622 p = blob + ret;
623 ret = -E_SSH_PARSE;
624 if (p >= end)
625 goto free_blob;
626 PARA_DEBUG_LOG("scanning modulus and public exponent\n");
627 gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
628 if (gret) {
629 ret = -E_MPI_SCAN;
630 PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
631 goto free_blob;
632 }
633 PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
634 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_e);
635 // PARA_CRIT_LOG("e: %s\n", buf);
636 p += nr_scanned;
637 if (p >= end)
638 goto release_e;
639 gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
640 if (gret) {
641 ret = -E_MPI_SCAN;
642 PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
643 goto release_e;
644 }
645 PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
646 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_n);
647 // PARA_CRIT_LOG("n: %s\n", buf);
648 gret = gcry_sexp_build(result, &erroff, RSA_PUBKEY_SEXP, n, e);
649 if (gret) {
650 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
651 gcry_strerror(gcry_err_code(gret)));
652 ret = -E_SEXP_BUILD;
653 goto release_n;
654 }
655 ret = nr_scanned / 32 * 32;
656 PARA_INFO_LOG("successfully read %u bit ssh public key\n", ret * 8);
657 release_n:
658 gcry_mpi_release(n);
659 release_e:
660 gcry_mpi_release(e);
661 free_blob:
662 free(blob);
663 return ret;
664 }
665
666 int get_asymmetric_key(const char *key_file, int private,
667 struct asymmetric_key **result)
668 {
669 int ret, ret2;
670 void *map;
671 size_t map_size;
672 unsigned char *start, *end;
673 gcry_sexp_t sexp;
674 struct asymmetric_key *key;
675
676 if (private)
677 return get_private_key(key_file, result);
678 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
679 if (ret < 0)
680 return ret;
681 ret = is_ssh_rsa_key(map, map_size);
682 if (!ret) {
683 ret = para_munmap(map, map_size);
684 if (ret < 0)
685 return ret;
686 return get_asn_public_key(key_file, result);
687 }
688 start = map + ret;
689 end = map + map_size;
690 ret = -E_SSH_PARSE;
691 if (start >= end)
692 goto unmap;
693 ret = get_ssh_public_key(start, end - start, &sexp);
694 if (ret < 0)
695 goto unmap;
696 key = para_malloc(sizeof(*key));
697 key->num_bytes = ret;
698 key->sexp = sexp;
699 *result = key;
700 ret = key->num_bytes;
701 unmap:
702 ret2 = para_munmap(map, map_size);
703 if (ret >= 0 && ret2 < 0)
704 ret = ret2;
705 return ret;
706 }
707
708 void free_asymmetric_key(struct asymmetric_key *key)
709 {
710 if (!key)
711 return;
712 gcry_sexp_release(key->sexp);
713 free(key);
714 }
715
716 static int decode_rsa(gcry_sexp_t sexp, int key_size, unsigned char *outbuf,
717 size_t *nbytes)
718 {
719 int ret;
720 gcry_error_t gret;
721 unsigned char oaep_buf[512];
722 gcry_mpi_t out_mpi;
723
724 if (libgcrypt_has_oaep) {
725 const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
726
727 if (!p) {
728 PARA_ERROR_LOG("could not get data from list\n");
729 return -E_OEAP;
730 }
731 memcpy(outbuf, p, *nbytes);
732 return 1;
733 }
734 out_mpi = gcry_sexp_nth_mpi(sexp, 0, GCRYMPI_FMT_USG);
735 if (!out_mpi)
736 return -E_SEXP_FIND;
737 gret = gcry_mpi_print(GCRYMPI_FMT_USG, oaep_buf, sizeof(oaep_buf),
738 nbytes, out_mpi);
739 if (gret) {
740 PARA_ERROR_LOG("mpi_print: %s\n", gcrypt_strerror(gret));
741 ret = -E_MPI_PRINT;
742 goto out_mpi_release;
743 }
744 /*
745 * An oaep-encoded buffer always starts with at least one zero byte.
746 * However, leading zeroes in an mpi are omitted in the output of
747 * gcry_mpi_print() when using the GCRYMPI_FMT_USG format. The
748 * alternative, GCRYMPI_FMT_STD, does not work either because here the
749 * leading zero(es) might also be omitted, depending on the value of
750 * the second byte.
751 *
752 * To circumvent this, we shift the oaep buffer to the right. But first
753 * we check that the buffer actually started with a zero byte, i.e. that
754 * nbytes < key_size. Otherwise a decoding error occurred.
755 */
756 ret = -E_SEXP_DECRYPT;
757 if (*nbytes >= key_size)
758 goto out_mpi_release;
759 memmove(oaep_buf + key_size - *nbytes, oaep_buf, *nbytes);
760 memset(oaep_buf, 0, key_size - *nbytes);
761
762 PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
763 key_size);
764 dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);;
765 ret = unpad_oaep(oaep_buf, key_size, outbuf, nbytes);
766 if (ret < 0)
767 goto out_mpi_release;
768 PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
769 *nbytes);
770 dump_buffer("unpadded decrypted buffer", outbuf, *nbytes);;
771 ret = 1;
772 out_mpi_release:
773 gcry_mpi_release(out_mpi);
774 return ret;
775 }
776
777 int priv_decrypt(const char *key_file, unsigned char *outbuf,
778 unsigned char *inbuf, int inlen)
779 {
780 gcry_error_t gret;
781 int ret, key_size;
782 struct asymmetric_key *priv;
783 gcry_mpi_t in_mpi = NULL;
784 gcry_sexp_t in, out, priv_key;
785 size_t nbytes;
786
787 PARA_INFO_LOG("decrypting %d byte input\n", inlen);
788 /* key_file -> asymmetric key priv */
789 ret = get_private_key(key_file, &priv);
790 if (ret < 0)
791 return ret;
792 key_size = ret / 8;
793
794 /* asymmetric key priv -> sexp priv_key */
795 ret = -E_SEXP_FIND;
796 priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
797 if (!priv_key)
798 goto free_key;
799
800 /* inbuf -> in_mpi */
801 gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
802 inlen, NULL);
803 if (gret) {
804 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
805 ret = -E_MPI_SCAN;
806 goto key_release;
807 }
808 /* in_mpi -> in sexp */
809 gret = gcry_sexp_build(&in, NULL, rsa_decrypt_sexp, in_mpi);
810 if (gret) {
811 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
812 ret = -E_SEXP_BUILD;
813 goto in_mpi_release;
814 }
815
816 /* rsa decryption: in sexp -> out sexp */
817 gret = gcry_pk_decrypt(&out, in, priv_key);
818 if (gret) {
819 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
820 ret = -E_SEXP_DECRYPT;
821 goto in_release;
822 }
823 ret = decode_rsa(out, key_size, outbuf, &nbytes);
824 if (ret < 0)
825 goto out_release;
826 PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
827 ret = nbytes;
828 out_release:
829 gcry_sexp_release(out);
830 in_release:
831 gcry_sexp_release(in);
832 in_mpi_release:
833 gcry_mpi_release(in_mpi);
834 key_release:
835 gcry_sexp_release(priv_key);
836 free_key:
837 free_asymmetric_key(priv);
838 return ret;
839 }
840
841 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
842 unsigned len, unsigned char *outbuf)
843 {
844 gcry_error_t gret;
845 gcry_sexp_t pub_key, in, out, out_a;
846 gcry_mpi_t out_mpi = NULL;
847 size_t nbytes;
848 int ret;
849
850 PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
851
852 /* get pub key */
853 pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
854 if (!pub_key)
855 return -E_SEXP_FIND;
856 if (libgcrypt_has_oaep) {
857 gret = gcry_sexp_build(&in, NULL,
858 "(data(flags oaep)(value %b))", len, inbuf);
859 } else {
860 unsigned char padded_input[256];
861 const size_t pad_size = 256;
862 /* inbuf -> padded inbuf */
863 pad_oaep(inbuf, len, padded_input, pad_size);
864 /* padded inbuf -> in sexp */
865 gret = gcry_sexp_build(&in, NULL,
866 "(data(flags raw)(value %b))", pad_size, padded_input);
867 }
868 if (gret) {
869 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
870 ret = -E_SEXP_BUILD;
871 goto key_release;
872 }
873 /* rsa sexp encryption: in -> out */
874 gret = gcry_pk_encrypt(&out, in, pub_key);
875 if (gret) {
876 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
877 ret = -E_SEXP_ENCRYPT;
878 goto in_release;
879 }
880 /* extract a, an MPI with the result of the RSA operation */
881 ret = -E_SEXP_FIND;
882 out_a = gcry_sexp_find_token(out, "a", 0);
883 if (!out_a)
884 goto out_release;
885 /* convert sexp out_a -> out_mpi */
886 out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
887 if (!out_mpi) {
888 ret = -E_SEXP_FIND;
889 goto out_a_release;
890 }
891 gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
892 if (gret) {
893 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
894 ret = -E_SEXP_ENCRYPT;
895 goto out_mpi_release;
896 }
897 PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
898 dump_buffer("enc buf", outbuf, nbytes);
899 ret = nbytes;
900
901 out_mpi_release:
902 gcry_mpi_release(out_mpi);
903 out_a_release:
904 gcry_sexp_release(out_a);
905 out_release:
906 gcry_sexp_release(out);
907 in_release:
908 gcry_sexp_release(in);
909 key_release:
910 gcry_sexp_release(pub_key);
911 return ret;
912 }
913
914 struct stream_cipher {
915 gcry_cipher_hd_t handle;
916 };
917
918 struct stream_cipher *sc_new(const unsigned char *data, int len)
919 {
920 gcry_error_t gret;
921
922 struct stream_cipher *sc = para_malloc(sizeof(*sc));
923 gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_ARCFOUR,
924 GCRY_CIPHER_MODE_STREAM, 0);
925 if (gret) {
926 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
927 free(sc);
928 return NULL;
929 }
930 gret = gcry_cipher_setkey(sc->handle, data, (size_t)len);
931 assert(gret == 0);
932 return sc;
933 }
934
935 void sc_free(struct stream_cipher *sc)
936 {
937 if (!sc)
938 return;
939 gcry_cipher_close(sc->handle);
940 free(sc);
941 }
942
943 int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
944 size_t size)
945 {
946 gcry_error_t gret;
947 int ret;
948 unsigned char *tmp = para_malloc(size);
949
950 assert(size);
951 gret = gcry_cipher_encrypt(scc->send->handle, tmp, size,
952 (unsigned char *)buf, size);
953 assert(gret == 0);
954 ret = xwrite(scc->fd, (char *)tmp, size);
955 free(tmp);
956 return ret;
957 }
958
959 int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
960 size_t size)
961 {
962 gcry_error_t gret;
963 ssize_t ret = recv(scc->fd, buf, size, 0);
964
965 if (ret < 0)
966 ret = -ERRNO_TO_PARA_ERROR(errno);
967 if (ret <= 0)
968 return ret;
969 /* perform in-place encryption */
970 gret = gcry_cipher_encrypt(scc->recv->handle, (unsigned char *)buf, ret,
971 NULL, 0);
972 assert(gret == 0);
973 return ret;
974 }