1 /* Copyright (C) 2011 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
3 /** \file gcrypt.c Libgrcypt-based encryption/decryption routines. */
12 #include "crypt_backend.h"
16 //#define GCRYPT_DEBUG 1
19 static void dump_buffer(const char *msg, unsigned char *buf, int len)
23 fprintf(stderr, "%s (%d bytes): ", msg, len);
24 for (i = 0; i < len; i++)
25 fprintf(stderr, "%02x ", buf[i]);
26 fprintf(stderr, "\n");
29 /** Empty. Define GCRYPT_DEBUG to dump buffers. */
30 #define dump_buffer(a, b, c)
33 void hash_function(const char *data, unsigned long len, unsigned char *hash)
39 gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
41 gcry_md_write(handle, data, (size_t)len);
42 gcry_md_final(handle);
43 md = gcry_md_read(handle, GCRY_MD_SHA1);
45 memcpy(hash, md, HASH_SIZE);
46 gcry_md_close(handle);
49 void get_random_bytes_or_die(unsigned char *buf, int num)
51 gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
55 * This is called at the beginning of every program that uses libgcrypt. We
56 * don't have to initialize any random seed here, but we must initialize the
57 * gcrypt library. This task is performed by gcry_check_version() which can
58 * also check that the gcrypt library version is at least the minimal required
61 void init_random_seed_or_die(void)
63 const char *req_ver = "1.5.0";
65 if (gcry_check_version(req_ver))
67 PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
68 req_ver, gcry_check_version(NULL));
72 /** S-expression for the public part of an RSA key. */
73 #define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
74 /** S-expression for a private RSA key. */
75 #define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
76 /** S-expression for decryption. */
77 #define RSA_DECRYPT_SEXP "(enc-val(flags oaep)(rsa(a %m)))"
79 struct asymmetric_key {
84 static const char *gcrypt_strerror(gcry_error_t gret)
86 return gcry_strerror(gcry_err_code(gret));
89 static int decode_key(const char *key_file, const char *header_str,
90 const char *footer_str, unsigned char **result)
94 size_t map_size, key_size, blob_size;
95 unsigned char *blob = NULL;
96 char *begin, *footer, *key;
98 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
102 if (strncmp(map, header_str, strlen(header_str)))
104 footer = strstr(map, footer_str);
108 begin = map + strlen(header_str);
109 /* skip whitespace at the beginning */
110 for (; begin < footer; begin++) {
111 if (para_isspace(*begin))
119 key_size = footer - begin;
120 key = para_malloc(key_size + 1);
121 for (i = 0, j = 0; begin + i < footer; i++) {
122 if (para_isspace(begin[i]))
127 ret = base64_decode(key, j, (char **)&blob, &blob_size);
137 ret2 = para_munmap(map, map_size);
138 if (ret >= 0 && ret2 < 0)
149 /** ASN Types and their code. */
151 /** The next object is an integer. */
152 ASN1_TYPE_INTEGER = 0x2,
153 /** Bit string object. */
154 ASN1_TYPE_BIT_STRING = 0x03,
155 /** Keys start with one big type sequence. */
156 ASN1_TYPE_SEQUENCE = 0x30,
159 /* bit 6 has value 0 */
160 static inline bool is_primitive(unsigned char c)
162 return (c & (1<<6)) == 0;
165 static inline bool is_primitive_integer(unsigned char c)
167 if (!is_primitive(c))
169 return (c & 0x1f) == ASN1_TYPE_INTEGER;
172 /* Bit 8 is zero (and bits 7-1 give the length) */
173 static inline bool is_short_form(unsigned char c)
175 return (c & 0x80) == 0;
178 static inline int get_short_form_length(unsigned char c)
183 static inline int get_long_form_num_length_bytes(unsigned char c)
189 * Returns: Number of bytes scanned. This may differ from the value returned via
190 * bn_bytes because the latter does not include the ASN.1 prefix and a leading
191 * zero is not considered as an additional byte for bn_bytes.
193 static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
198 unsigned char *cp = start;
200 if (!is_primitive_integer(*cp))
201 return -E_BAD_PRIVATE_KEY;
203 if (is_short_form(*cp)) {
204 bn_size = get_short_form_length(*cp);
207 int num_bytes = get_long_form_num_length_bytes(*cp);
208 if (cp + num_bytes > end)
209 return -E_BAD_PRIVATE_KEY;
210 if (num_bytes > 4) /* nobody has such a large modulus */
211 return -E_BAD_PRIVATE_KEY;
214 for (i = 0; i < num_bytes; i++, cp++)
215 bn_size = (bn_size << 8) + *cp;
217 PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, (unsigned)bn_size);
218 gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
220 PARA_ERROR_LOG("%s while scanning n\n",
221 gcry_strerror(gcry_err_code(gret)));
225 * Don't take the first leading zero into account for the size of the
235 // unsigned char *buf;
236 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
237 // PARA_CRIT_LOG("bn: %s\n", buf);
241 static int find_privkey_bignum_offset(const unsigned char *data, int len)
243 const unsigned char *p = data, *end = data + len;
245 /* like the public key, the whole thing is contained in a sequence */
246 if (*p != ASN1_TYPE_SEQUENCE)
247 return -E_ASN1_PARSE;
250 return -E_ASN1_PARSE;
251 if (is_short_form(*p))
254 p += 1 + get_long_form_num_length_bytes(*p);
256 return -E_ASN1_PARSE;
258 /* skip next integer */
259 if (*p != ASN1_TYPE_INTEGER)
260 return -E_ASN1_PARSE;
263 return -E_ASN1_PARSE;
264 if (is_short_form(*p))
265 p += 1 + get_short_form_length(*p);
267 p += 1 + get_long_form_num_length_bytes(*p);
269 return -E_ASN1_PARSE;
273 /** Private keys start with this header. */
274 #define PRIVATE_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
275 /** Private keys end with this footer. */
276 #define PRIVATE_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
278 static int get_private_key(const char *key_file, struct asymmetric_key **result)
280 gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
282 unsigned char *blob, *cp, *end;
283 int blob_size, ret, n_size;
287 struct asymmetric_key *key;
290 ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
295 end = blob + blob_size;
296 ret = find_privkey_bignum_offset(blob, blob_size);
299 PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
302 ret = read_bignum(cp, end, &n, &n_size);
307 ret = read_bignum(cp, end, &e, NULL);
312 ret = read_bignum(cp, end, &d, NULL);
317 ret = read_bignum(cp, end, &p, NULL);
322 ret = read_bignum(cp, end, &q, NULL);
326 ret = read_bignum(cp, end, &u, NULL);
330 * OpenSSL uses slightly different parameters than gcrypt. To use these
331 * parameters we need to swap the values of p and q and recompute u.
333 if (gcry_mpi_cmp(p, q) > 0) {
335 gcry_mpi_invm(u, p, q);
337 gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
341 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
342 gcry_strerror(gcry_err_code(gret)));
346 key = para_malloc(sizeof(*key));
350 PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
368 static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
372 unsigned char *blob = NULL, *p, *end;
373 size_t nr_scanned, erroff, decoded_size;
374 gcry_mpi_t e = NULL, n = NULL;
376 PARA_DEBUG_LOG("decoding %d byte public rsa-ssh key\n", size);
377 ret = uudecode((char *)data, size, (char **)&blob, &decoded_size);
380 end = blob + decoded_size;
381 dump_buffer("decoded key", blob, decoded_size);
382 ret = check_ssh_key_header(blob, decoded_size);
389 PARA_DEBUG_LOG("scanning modulus and public exponent\n");
390 gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
393 PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
396 PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
397 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_e);
398 // PARA_CRIT_LOG("e: %s\n", buf);
402 gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
405 PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
408 PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
409 // gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_n);
410 // PARA_CRIT_LOG("n: %s\n", buf);
411 gret = gcry_sexp_build(result, &erroff, RSA_PUBKEY_SEXP, n, e);
413 PARA_ERROR_LOG("offset %zu: %s\n", erroff,
414 gcry_strerror(gcry_err_code(gret)));
418 ret = nr_scanned / 32 * 32;
419 PARA_INFO_LOG("successfully read %d bit ssh public key\n", ret * 8);
429 int get_public_key(const char *key_file, struct asymmetric_key **result)
434 unsigned char *start, *end;
436 struct asymmetric_key *key;
438 ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
441 ret = is_ssh_rsa_key(map, map_size);
443 para_munmap(map, map_size);
447 end = map + map_size;
451 ret = get_ssh_public_key(start, end - start, &sexp);
454 key = para_malloc(sizeof(*key));
455 key->num_bytes = ret;
459 ret2 = para_munmap(map, map_size);
460 if (ret >= 0 && ret2 < 0)
465 void free_public_key(struct asymmetric_key *key)
469 gcry_sexp_release(key->sexp);
473 static int decode_rsa(gcry_sexp_t sexp, unsigned char *outbuf, size_t *nbytes)
475 const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
478 return -E_RSA_DECODE;
479 memcpy(outbuf, p, *nbytes);
483 int priv_decrypt(const char *key_file, unsigned char *outbuf,
484 unsigned char *inbuf, int inlen)
488 struct asymmetric_key *priv;
489 gcry_mpi_t in_mpi = NULL;
490 gcry_sexp_t in, out, priv_key;
493 ret = check_private_key_file(key_file);
496 PARA_INFO_LOG("decrypting %d byte input\n", inlen);
497 /* key_file -> asymmetric key priv */
498 ret = get_private_key(key_file, &priv);
502 /* asymmetric key priv -> sexp priv_key */
504 priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
508 /* inbuf -> in_mpi */
509 gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
512 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
516 /* in_mpi -> in sexp */
517 gret = gcry_sexp_build(&in, NULL, RSA_DECRYPT_SEXP, in_mpi);
519 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
524 /* rsa decryption: in sexp -> out sexp */
525 gret = gcry_pk_decrypt(&out, in, priv_key);
527 PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
528 ret = -E_SEXP_DECRYPT;
531 ret = decode_rsa(out, outbuf, &nbytes);
534 PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
537 gcry_sexp_release(out);
539 gcry_sexp_release(in);
541 gcry_mpi_release(in_mpi);
543 gcry_sexp_release(priv_key);
545 gcry_sexp_release(priv->sexp);
550 int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
551 unsigned len, unsigned char *outbuf)
554 gcry_sexp_t pub_key, in, out, out_a;
555 gcry_mpi_t out_mpi = NULL;
559 PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
562 pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
565 gret = gcry_sexp_build(&in, NULL, "(data(flags oaep)(value %b))", len, inbuf);
567 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
571 /* rsa sexp encryption: in -> out */
572 gret = gcry_pk_encrypt(&out, in, pub_key);
574 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
575 ret = -E_SEXP_ENCRYPT;
578 /* extract a, an MPI with the result of the RSA operation */
580 out_a = gcry_sexp_find_token(out, "a", 0);
583 /* convert sexp out_a -> out_mpi */
584 out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
589 gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
591 PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
592 ret = -E_SEXP_ENCRYPT;
593 goto out_mpi_release;
595 PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
596 dump_buffer("enc buf", outbuf, nbytes);
600 gcry_mpi_release(out_mpi);
602 gcry_sexp_release(out_a);
604 gcry_sexp_release(out);
606 gcry_sexp_release(in);
608 gcry_sexp_release(pub_key);
612 struct stream_cipher {
613 gcry_cipher_hd_t handle;
616 struct stream_cipher *sc_new(const unsigned char *data, int len)
619 struct stream_cipher *sc = para_malloc(sizeof(*sc));
621 assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
622 gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_AES128,
623 GCRY_CIPHER_MODE_CTR, 0);
625 gret = gcry_cipher_setkey(sc->handle, data,
626 AES_CRT128_BLOCK_SIZE);
628 gret = gcry_cipher_setctr(sc->handle,
629 data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
634 void sc_free(struct stream_cipher *sc)
638 gcry_cipher_close(sc->handle);
642 void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
644 gcry_cipher_hd_t handle = sc->handle;
647 /* perform in-place encryption */
649 gret = gcry_cipher_encrypt(handle, src->iov_base, src->iov_len,