2 * Copyright (C) 2011 Andre Noll <maan@tuebingen.mpg.de>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file gcrypt.c Libgrcypt-based encryption/decryption routines. */
16 #include "crypt_backend.h"
20 //#define GCRYPT_DEBUG 1
22 static bool libgcrypt_has_oaep;
23 static const char *rsa_decrypt_sexp;
26 static void dump_buffer(const char *msg, unsigned char *buf, int len)
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");
36 /** Empty. Define GCRYPT_DEBUG to dump buffers. */
37 #define dump_buffer(a, b, c)
40 void hash_function(const char *data, unsigned long len, unsigned char *hash)
46 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
48 gcry_md_write(handle, data, (size_t)len);
49 gcry_md_final(handle);
50 md = gcry_md_read(handle, GCRY_MD_SHA1);
52 memcpy(hash, md, HASH_SIZE);
53 gcry_md_close(handle);
56 void get_random_bytes_or_die(unsigned char *buf, int num)
58 gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
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
69 void init_random_seed_or_die(void)
71 const char *ver, *req_ver;
73 ver = gcry_check_version(NULL);
75 if (!gcry_check_version(req_ver)) {
76 PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
81 if (gcry_check_version(req_ver)) {
82 libgcrypt_has_oaep = true;
83 rsa_decrypt_sexp = "(enc-val(flags oaep)(rsa(a %m)))";
85 libgcrypt_has_oaep = false;
86 rsa_decrypt_sexp = "(enc-val(rsa(a %m)))";
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)))"
95 /* rfc 3447, appendix B.2 */
96 static void mgf1(unsigned char *seed, size_t seed_len, unsigned result_len,
97 unsigned char *result)
103 unsigned char octet_string[4], *rp = result, *end = rp + result_len;
105 assert(result_len / HASH_SIZE < 1ULL << 31);
106 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 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)));
119 gcry_md_reset(handle);
121 gcry_md_close(handle);
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";
131 /* rfc3447, section 7.1.1 */
132 static void pad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
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];
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",
145 dump_buffer("unpadded buffer", in, in_len);
148 get_random_bytes_or_die(seed, HASH_SIZE);
149 memcpy(db, empty_hash, HASH_SIZE);
150 memset(ps, 0, ps_len);
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++)
157 mgf1(db, mask_len, HASH_SIZE, seed_mask);
158 for (n = 0; n < HASH_SIZE; n++)
159 seed[n] ^= seed_mask[n];
161 dump_buffer("padded buffer", out, out_len);
164 /* rfc 3447, section 7.1.2 */
165 static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
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;
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++)
182 if (memcmp(db, empty_hash, HASH_SIZE))
184 for (p = db + HASH_SIZE; p < in + in_len - 1; p++)
187 if (p >= in + in_len - 1)
190 *out_len = in + in_len - p;
191 memcpy(out, p, *out_len);
195 struct asymmetric_key {
200 static const char *gcrypt_strerror(gcry_error_t gret)
202 return gcry_strerror(gcry_err_code(gret));
205 static int decode_key(const char *key_file, const char *header_str,
206 const char *footer_str, unsigned char **result)
210 size_t map_size, key_size, blob_size;
211 unsigned char *blob = NULL;
212 char *begin, *footer, *key;
214 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
218 if (strncmp(map, header_str, strlen(header_str)))
220 footer = strstr(map, footer_str);
224 begin = map + strlen(header_str);
225 /* skip whitespace at the beginning */
226 for (; begin < footer; begin++) {
227 if (para_isspace(*begin))
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]))
243 ret = base64_decode(key, j, (char **)&blob, &blob_size);
253 ret2 = para_munmap(map, map_size);
254 if (ret >= 0 && ret2 < 0)
265 /** ASN Types and their code. */
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,
275 /* bit 6 has value 0 */
276 static inline bool is_primitive(unsigned char c)
278 return (c & (1<<6)) == 0;
281 static inline bool is_primitive_integer(unsigned char c)
283 if (!is_primitive(c))
285 return (c & 0x1f) == ASN1_TYPE_INTEGER;
288 /* Bit 8 is zero (and bits 7-1 give the length) */
289 static inline bool is_short_form(unsigned char c)
291 return (c & 0x80) == 0;
294 static inline int get_short_form_length(unsigned char c)
299 static inline int get_long_form_num_length_bytes(unsigned char c)
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.
309 static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
314 unsigned char *cp = start;
316 if (!is_primitive_integer(*cp))
317 return -E_BAD_PRIVATE_KEY;
319 if (is_short_form(*cp)) {
320 bn_size = get_short_form_length(*cp);
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;
330 for (i = 0; i < num_bytes; i++, cp++)
331 bn_size = (bn_size << 8) + *cp;
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);
336 PARA_ERROR_LOG("%s while scanning n\n",
337 gcry_strerror(gcry_err_code(gret)));
341 * Don't take the first leading zero into account for the size of the
351 // unsigned char *buf;
352 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
353 // PARA_CRIT_LOG("bn: %s\n", buf);
357 static int find_privkey_bignum_offset(const unsigned char *data, int len)
359 const unsigned char *p = data, *end = data + len;
361 /* like the public key, the whole thing is contained in a sequence */
362 if (*p != ASN1_TYPE_SEQUENCE)
363 return -E_ASN1_PARSE;
366 return -E_ASN1_PARSE;
367 if (is_short_form(*p))
370 p += 1 + get_long_form_num_length_bytes(*p);
372 return -E_ASN1_PARSE;
374 /* skip next integer */
375 if (*p != ASN1_TYPE_INTEGER)
376 return -E_ASN1_PARSE;
379 return -E_ASN1_PARSE;
380 if (is_short_form(*p))
381 p += 1 + get_short_form_length(*p);
383 p += 1 + get_long_form_num_length_bytes(*p);
385 return -E_ASN1_PARSE;
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-----"
394 static int get_private_key(const char *key_file, struct asymmetric_key **result)
396 gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
398 unsigned char *blob, *cp, *end;
399 int blob_size, ret, n_size;
403 struct asymmetric_key *key;
406 ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
411 end = blob + blob_size;
412 ret = find_privkey_bignum_offset(blob, blob_size);
415 PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
418 ret = read_bignum(cp, end, &n, &n_size);
423 ret = read_bignum(cp, end, &e, NULL);
428 ret = read_bignum(cp, end, &d, NULL);
433 ret = read_bignum(cp, end, &p, NULL);
438 ret = read_bignum(cp, end, &q, NULL);
442 ret = read_bignum(cp, end, &u, NULL);
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.
449 if (gcry_mpi_cmp(p, q) > 0) {
451 gcry_mpi_invm(u, p, q);
453 gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
457 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
458 gcry_strerror(gcry_err_code(gret)));
462 key = para_malloc(sizeof(*key));
466 PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
484 static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
488 unsigned char *blob = NULL, *p, *end;
489 size_t nr_scanned, erroff, decoded_size;
490 gcry_mpi_t e = NULL, n = NULL;
492 PARA_DEBUG_LOG("decoding %d byte public rsa-ssh key\n", size);
493 ret = uudecode((char *)data, size, (char **)&blob, &decoded_size);
496 end = blob + decoded_size;
497 dump_buffer("decoded key", blob, decoded_size);
498 ret = check_ssh_key_header(blob, decoded_size);
505 PARA_DEBUG_LOG("scanning modulus and public exponent\n");
506 gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
509 PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
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);
518 gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
521 PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
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);
529 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
530 gcry_strerror(gcry_err_code(gret)));
534 ret = nr_scanned / 32 * 32;
535 PARA_INFO_LOG("successfully read %d bit ssh public key\n", ret * 8);
545 int get_public_key(const char *key_file, struct asymmetric_key **result)
550 unsigned char *start, *end;
552 struct asymmetric_key *key;
554 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
557 ret = is_ssh_rsa_key(map, map_size);
559 para_munmap(map, map_size);
563 end = map + map_size;
567 ret = get_ssh_public_key(start, end - start, &sexp);
570 key = para_malloc(sizeof(*key));
571 key->num_bytes = ret;
575 ret2 = para_munmap(map, map_size);
576 if (ret >= 0 && ret2 < 0)
581 void free_public_key(struct asymmetric_key *key)
585 gcry_sexp_release(key->sexp);
589 static int decode_rsa(gcry_sexp_t sexp, int key_size, unsigned char *outbuf,
594 unsigned char oaep_buf[512];
597 if (libgcrypt_has_oaep) {
598 const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
601 PARA_ERROR_LOG("could not get data from list\n");
604 memcpy(outbuf, p, *nbytes);
607 out_mpi = gcry_sexp_nth_mpi(sexp, 0, GCRYMPI_FMT_USG);
610 gret = gcry_mpi_print(GCRYMPI_FMT_USG, oaep_buf, sizeof(oaep_buf),
613 PARA_ERROR_LOG("mpi_print: %s\n", gcrypt_strerror(gret));
615 goto out_mpi_release;
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
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.
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);
635 PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
637 dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);
638 ret = unpad_oaep(oaep_buf, key_size, outbuf, nbytes);
640 goto out_mpi_release;
641 PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
643 dump_buffer("unpadded decrypted buffer", outbuf, *nbytes);
646 gcry_mpi_release(out_mpi);
650 int priv_decrypt(const char *key_file, unsigned char *outbuf,
651 unsigned char *inbuf, int inlen)
655 struct asymmetric_key *priv;
656 gcry_mpi_t in_mpi = NULL;
657 gcry_sexp_t in, out, priv_key;
660 ret = check_private_key_file(key_file);
663 PARA_INFO_LOG("decrypting %d byte input\n", inlen);
664 /* key_file -> asymmetric key priv */
665 ret = get_private_key(key_file, &priv);
670 /* asymmetric key priv -> sexp priv_key */
672 priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
676 /* inbuf -> in_mpi */
677 gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
680 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
684 /* in_mpi -> in sexp */
685 gret = gcry_sexp_build(&in, NULL, rsa_decrypt_sexp, in_mpi);
687 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
692 /* rsa decryption: in sexp -> out sexp */
693 gret = gcry_pk_decrypt(&out, in, priv_key);
695 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
696 ret = -E_SEXP_DECRYPT;
699 ret = decode_rsa(out, key_size, outbuf, &nbytes);
702 PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
705 gcry_sexp_release(out);
707 gcry_sexp_release(in);
709 gcry_mpi_release(in_mpi);
711 gcry_sexp_release(priv_key);
713 gcry_sexp_release(priv->sexp);
718 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
719 unsigned len, unsigned char *outbuf)
722 gcry_sexp_t pub_key, in, out, out_a;
723 gcry_mpi_t out_mpi = NULL;
727 PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
730 pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
733 if (libgcrypt_has_oaep) {
734 gret = gcry_sexp_build(&in, NULL,
735 "(data(flags oaep)(value %b))", len, inbuf);
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);
746 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
750 /* rsa sexp encryption: in -> out */
751 gret = gcry_pk_encrypt(&out, in, pub_key);
753 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
754 ret = -E_SEXP_ENCRYPT;
757 /* extract a, an MPI with the result of the RSA operation */
759 out_a = gcry_sexp_find_token(out, "a", 0);
762 /* convert sexp out_a -> out_mpi */
763 out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
768 gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
770 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
771 ret = -E_SEXP_ENCRYPT;
772 goto out_mpi_release;
774 PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
775 dump_buffer("enc buf", outbuf, nbytes);
779 gcry_mpi_release(out_mpi);
781 gcry_sexp_release(out_a);
783 gcry_sexp_release(out);
785 gcry_sexp_release(in);
787 gcry_sexp_release(pub_key);
791 struct stream_cipher {
792 gcry_cipher_hd_t handle;
795 struct stream_cipher *sc_new(const unsigned char *data, int len,
799 struct stream_cipher *sc = para_malloc(sizeof(*sc));
802 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
803 gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_AES128,
804 GCRY_CIPHER_MODE_CTR, 0);
806 gret = gcry_cipher_setkey(sc->handle, data,
807 AES_CRT128_BLOCK_SIZE);
809 gret = gcry_cipher_setctr(sc->handle,
810 data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
814 gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_ARCFOUR,
815 GCRY_CIPHER_MODE_STREAM, 0);
817 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
821 gret = gcry_cipher_setkey(sc->handle, data, (size_t)len);
826 void sc_free(struct stream_cipher *sc)
830 gcry_cipher_close(sc->handle);
834 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
836 gcry_cipher_hd_t handle = sc->handle;
839 /* perform in-place encryption */
841 gret = gcry_cipher_encrypt(handle, src->iov_base, src->iov_len,