2 This file is part of GNUnet
3 Copyright (C) 2014 Christian Grothoff (and other contributing authors)
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11 A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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14 GNUnet; see the file COPYING. If not, If not, see <http://www.gnu.org/licenses/>
18 * @file util/crypto_rsa.c
19 * @brief Chaum-style Blind signatures based on RSA
20 * @author Sree Harsha Totakura <sreeharsha@totakura.in>
21 * @author Christian Grothoff
25 #include "gnunet_util_lib.h"
27 #define LOG(kind,...) GNUNET_log_from (kind, "util", __VA_ARGS__)
31 * The private information of an RSA key pair.
33 struct GNUNET_CRYPTO_rsa_PrivateKey
36 * Libgcrypt S-expression for the RSA private key.
43 * The public information of an RSA key pair.
45 struct GNUNET_CRYPTO_rsa_PublicKey
48 * Libgcrypt S-expression for the RSA public key.
55 * @brief an RSA signature
57 struct GNUNET_CRYPTO_rsa_Signature
60 * Libgcrypt S-expression for the RSA signature.
67 * @brief RSA blinding key
69 struct GNUNET_CRYPTO_rsa_BlindingKey
72 * Random value used for blinding.
79 * Extract values from an S-expression.
81 * @param array where to store the result(s)
82 * @param sexp S-expression to parse
83 * @param topname top-level name in the S-expression that is of interest
84 * @param elems names of the elements to extract
85 * @return 0 on success
88 key_from_sexp (gcry_mpi_t *array,
99 if (! (list = gcry_sexp_find_token (sexp, topname, 0)))
101 l2 = gcry_sexp_cadr (list);
102 gcry_sexp_release (list);
107 for (s = elems; *s; s++, idx++)
109 if (! (l2 = gcry_sexp_find_token (list, s, 1)))
111 for (i = 0; i < idx; i++)
113 gcry_free (array[i]);
116 gcry_sexp_release (list);
117 return 3; /* required parameter not found */
119 array[idx] = gcry_sexp_nth_mpi (l2, 1, GCRYMPI_FMT_USG);
120 gcry_sexp_release (l2);
123 for (i = 0; i < idx; i++)
125 gcry_free (array[i]);
128 gcry_sexp_release (list);
129 return 4; /* required parameter is invalid */
132 gcry_sexp_release (list);
138 * Create a new private key. Caller must free return value.
140 * @param len length of the key in bits (i.e. 2048)
141 * @return fresh private key
143 struct GNUNET_CRYPTO_rsa_PrivateKey *
144 GNUNET_CRYPTO_rsa_private_key_create (unsigned int len)
146 struct GNUNET_CRYPTO_rsa_PrivateKey *ret;
148 gcry_sexp_t s_keyparam;
151 gcry_sexp_build (&s_keyparam,
153 "(genkey(rsa(nbits %d)))",
156 gcry_pk_genkey (&s_key,
158 gcry_sexp_release (s_keyparam);
161 gcry_pk_testkey (s_key));
163 ret = GNUNET_new (struct GNUNET_CRYPTO_rsa_PrivateKey);
170 * Free memory occupied by the private key.
172 * @param key pointer to the memory to free
175 GNUNET_CRYPTO_rsa_private_key_free (struct GNUNET_CRYPTO_rsa_PrivateKey *key)
177 gcry_sexp_release (key->sexp);
183 * Encode the private key in a format suitable for
184 * storing it into a file.
186 * @param key the private key
187 * @param[out] buffer set to a buffer with the encoded key
188 * @return size of memory allocated in @a buffer
191 GNUNET_CRYPTO_rsa_private_key_encode (const struct GNUNET_CRYPTO_rsa_PrivateKey *key,
197 n = gcry_sexp_sprint (key->sexp,
198 GCRYSEXP_FMT_DEFAULT,
201 b = GNUNET_malloc (n);
202 GNUNET_assert ((n - 1) == /* since the last byte is \0 */
203 gcry_sexp_sprint (key->sexp,
204 GCRYSEXP_FMT_DEFAULT,
213 * Decode the private key from the data-format back
214 * to the "normal", internal format.
216 * @param buf the buffer where the private key data is stored
217 * @param len the length of the data in @a buf
218 * @return NULL on error
220 struct GNUNET_CRYPTO_rsa_PrivateKey *
221 GNUNET_CRYPTO_rsa_private_key_decode (const char *buf,
224 struct GNUNET_CRYPTO_rsa_PrivateKey *key;
226 key = GNUNET_new (struct GNUNET_CRYPTO_rsa_PrivateKey);
228 gcry_sexp_new (&key->sexp,
237 /* FIXME: verify that this is an RSA private key */
243 * Extract the public key of the given private key.
245 * @param priv the private key
246 * @retur NULL on error, otherwise the public key
248 struct GNUNET_CRYPTO_rsa_PublicKey *
249 GNUNET_CRYPTO_rsa_private_key_get_public (const struct GNUNET_CRYPTO_rsa_PrivateKey *priv)
251 struct GNUNET_CRYPTO_rsa_PublicKey *pub;
256 rc = key_from_sexp (ne, priv->sexp, "public-key", "ne");
258 rc = key_from_sexp (ne, priv->sexp, "private-key", "ne");
260 rc = key_from_sexp (ne, priv->sexp, "rsa", "ne");
266 rc = gcry_sexp_build (&result,
268 "(public-key(rsa(n %m)(e %m)))",
271 gcry_mpi_release (ne[0]);
272 gcry_mpi_release (ne[1]);
273 pub = GNUNET_new (struct GNUNET_CRYPTO_rsa_PublicKey);
280 * Free memory occupied by the public key.
282 * @param key pointer to the memory to free
285 GNUNET_CRYPTO_rsa_public_key_free (struct GNUNET_CRYPTO_rsa_PublicKey *key)
287 gcry_sexp_release (key->sexp);
293 * Encode the public key in a format suitable for
294 * storing it into a file.
296 * @param key the private key
297 * @param[out] buffer set to a buffer with the encoded key
298 * @return size of memory allocated in @a buffer
301 GNUNET_CRYPTO_rsa_public_key_encode (const struct GNUNET_CRYPTO_rsa_PublicKey *key,
307 n = gcry_sexp_sprint (key->sexp,
308 GCRYSEXP_FMT_ADVANCED,
311 b = GNUNET_malloc (n);
312 GNUNET_assert ((n -1) == /* since the last byte is \0 */
313 gcry_sexp_sprint (key->sexp,
314 GCRYSEXP_FMT_ADVANCED,
323 * Compute hash over the public key.
325 * @param key public key to hash
326 * @param hc where to store the hash code
329 GNUNET_CRYPTO_rsa_public_key_hash (const struct GNUNET_CRYPTO_rsa_PublicKey *key,
330 struct GNUNET_HashCode *hc)
335 buf_size = GNUNET_CRYPTO_rsa_public_key_encode (key,
337 GNUNET_CRYPTO_hash (buf,
345 * Decode the public key from the data-format back
346 * to the "normal", internal format.
348 * @param buf the buffer where the public key data is stored
349 * @param len the length of the data in @a buf
350 * @return NULL on error
352 struct GNUNET_CRYPTO_rsa_PublicKey *
353 GNUNET_CRYPTO_rsa_public_key_decode (const char *buf,
356 struct GNUNET_CRYPTO_rsa_PublicKey *key;
360 key = GNUNET_new (struct GNUNET_CRYPTO_rsa_PublicKey);
362 gcry_sexp_new (&key->sexp,
371 /* verify that this is an RSA public key */
372 ret = key_from_sexp (&n, key->sexp, "public-key", "n");
374 ret = key_from_sexp (&n, key->sexp, "rsa", "n");
377 /* this is no public RSA key */
379 gcry_sexp_release (key->sexp);
383 gcry_mpi_release (n);
389 * Create a blinding key
391 * @param len length of the key in bits (i.e. 2048)
392 * @return the newly created blinding key
394 struct GNUNET_CRYPTO_rsa_BlindingKey *
395 GNUNET_CRYPTO_rsa_blinding_key_create (unsigned int len)
397 struct GNUNET_CRYPTO_rsa_BlindingKey *blind;
399 blind = GNUNET_new (struct GNUNET_CRYPTO_rsa_BlindingKey);
400 blind->r = gcry_mpi_new (len);
401 gcry_mpi_randomize (blind->r,
409 * Compare the values of two blinding keys.
412 * @param b2 the other key
413 * @return 0 if the two are equal
416 GNUNET_CRYPTO_rsa_blinding_key_cmp (struct GNUNET_CRYPTO_rsa_BlindingKey *b1,
417 struct GNUNET_CRYPTO_rsa_BlindingKey *b2)
419 return gcry_mpi_cmp (b1->r,
425 * Destroy a blinding key
427 * @param bkey the blinding key to destroy
430 GNUNET_CRYPTO_rsa_blinding_key_free (struct GNUNET_CRYPTO_rsa_BlindingKey *bkey)
432 gcry_mpi_release (bkey->r);
438 * Encode the blinding key in a format suitable for
439 * storing it into a file.
441 * @param bkey the blinding key
442 * @param[out] buffer set to a buffer with the encoded key
443 * @return size of memory allocated in @a buffer
446 GNUNET_CRYPTO_rsa_blinding_key_encode (const struct GNUNET_CRYPTO_rsa_BlindingKey *bkey,
453 gcry_mpi_print (GCRYMPI_FMT_USG,
458 b = GNUNET_malloc (n);
460 gcry_mpi_print (GCRYMPI_FMT_USG,
471 * Decode the blinding key from the data-format back
472 * to the "normal", internal format.
474 * @param buf the buffer where the public key data is stored
475 * @param len the length of the data in @a buf
476 * @return NULL on error
478 struct GNUNET_CRYPTO_rsa_BlindingKey *
479 GNUNET_CRYPTO_rsa_blinding_key_decode (const char *buf,
482 struct GNUNET_CRYPTO_rsa_BlindingKey *bkey;
485 bkey = GNUNET_new (struct GNUNET_CRYPTO_rsa_BlindingKey);
487 gcry_mpi_scan (&bkey->r,
489 (const unsigned char *) buf,
502 * Blinds the given message with the given blinding key
504 * @param hash hash of the message to sign
505 * @param bkey the blinding key
506 * @param pkey the public key of the signer
507 * @param[out] buffer set to a buffer with the blinded message to be signed
508 * @return number of bytes stored in @a buffer
511 GNUNET_CRYPTO_rsa_blind (const struct GNUNET_HashCode *hash,
512 struct GNUNET_CRYPTO_rsa_BlindingKey *bkey,
513 struct GNUNET_CRYPTO_rsa_PublicKey *pkey,
526 ret = key_from_sexp (ne, pkey->sexp, "public-key", "ne");
528 ret = key_from_sexp (ne, pkey->sexp, "rsa", "ne");
535 if (0 != (rc = gcry_mpi_scan (&data,
537 (const unsigned char *) hash,
538 sizeof (struct GNUNET_HashCode),
542 gcry_mpi_release (ne[0]);
543 gcry_mpi_release (ne[1]);
547 r_e = gcry_mpi_new (0);
552 data_r_e = gcry_mpi_new (0);
553 gcry_mpi_mulm (data_r_e,
557 gcry_mpi_release (data);
558 gcry_mpi_release (ne[0]);
559 gcry_mpi_release (ne[1]);
560 gcry_mpi_release (r_e);
562 gcry_mpi_print (GCRYMPI_FMT_USG,
567 b = GNUNET_malloc (n);
568 rc = gcry_mpi_print (GCRYMPI_FMT_USG,
573 gcry_mpi_release (data_r_e);
580 * Convert the data specified in the given purpose argument to an
581 * S-expression suitable for signature operations.
583 * @param ptr pointer to the data to convert
584 * @param size the size of the data
585 * @return converted s-expression
588 data_to_sexp (const void *ptr, size_t size)
596 gcry_mpi_scan (&value,
602 gcry_sexp_build (&data,
604 "(data (flags raw) (value %M))",
606 gcry_mpi_release (value);
612 * Sign the given message.
614 * @param key private key to use for the signing
615 * @param msg the message to sign
616 * @param msg_len number of bytes in @a msg to sign
617 * @return NULL on error, signature on success
619 struct GNUNET_CRYPTO_rsa_Signature *
620 GNUNET_CRYPTO_rsa_sign (const struct GNUNET_CRYPTO_rsa_PrivateKey *key,
624 struct GNUNET_CRYPTO_rsa_Signature *sig;
628 data = data_to_sexp (msg,
631 gcry_pk_sign (&result,
638 gcry_sexp_release (data);
639 sig = GNUNET_new (struct GNUNET_CRYPTO_rsa_Signature);
646 * Free memory occupied by signature.
648 * @param sig memory to freee
651 GNUNET_CRYPTO_rsa_signature_free (struct GNUNET_CRYPTO_rsa_Signature *sig)
653 gcry_sexp_release (sig->sexp);
659 * Encode the given signature in a format suitable for storing it into a file.
661 * @param sig the signature
662 * @param[out] buffer set to a buffer with the encoded key
663 * @return size of memory allocated in @a buffer
666 GNUNET_CRYPTO_rsa_signature_encode (const struct GNUNET_CRYPTO_rsa_Signature *sig,
672 n = gcry_sexp_sprint (sig->sexp,
673 GCRYSEXP_FMT_ADVANCED,
676 b = GNUNET_malloc (n);
677 GNUNET_assert ((n - 1) == /* since the last byte is \0 */
678 gcry_sexp_sprint (sig->sexp,
679 GCRYSEXP_FMT_ADVANCED,
688 * Decode the signature from the data-format back to the "normal", internal
691 * @param buf the buffer where the public key data is stored
692 * @param len the length of the data in @a buf
693 * @return NULL on error
695 struct GNUNET_CRYPTO_rsa_Signature *
696 GNUNET_CRYPTO_rsa_signature_decode (const char *buf,
699 struct GNUNET_CRYPTO_rsa_Signature *sig;
703 sig = GNUNET_new (struct GNUNET_CRYPTO_rsa_Signature);
705 gcry_sexp_new (&sig->sexp,
714 /* verify that this is an RSA signature */
715 ret = key_from_sexp (&s, sig->sexp, "sig-val", "s");
717 ret = key_from_sexp (&s, sig->sexp, "rsa", "s");
720 /* this is no RSA Signature */
722 gcry_sexp_release (sig->sexp);
726 gcry_mpi_release (s);
732 * Unblind a blind-signed signature. The signature should have been generated
733 * with #GNUNET_CRYPTO_rsa_sign() using a hash that was blinded with
734 * #GNUNET_CRYPTO_rsa_blind().
736 * @param sig the signature made on the blinded signature purpose
737 * @param bkey the blinding key used to blind the signature purpose
738 * @param pkey the public key of the signer
739 * @return unblinded signature on success, NULL on error
741 struct GNUNET_CRYPTO_rsa_Signature *
742 GNUNET_CRYPTO_rsa_unblind (struct GNUNET_CRYPTO_rsa_Signature *sig,
743 struct GNUNET_CRYPTO_rsa_BlindingKey *bkey,
744 struct GNUNET_CRYPTO_rsa_PublicKey *pkey)
751 struct GNUNET_CRYPTO_rsa_Signature *sret;
753 ret = key_from_sexp (&n, pkey->sexp, "public-key", "n");
755 ret = key_from_sexp (&n, pkey->sexp, "rsa", "n");
761 ret = key_from_sexp (&s, sig->sexp, "sig-val", "s");
763 ret = key_from_sexp (&s, sig->sexp, "rsa", "s");
766 gcry_mpi_release (n);
770 r_inv = gcry_mpi_new (0);
772 gcry_mpi_invm (r_inv,
777 gcry_mpi_release (n);
778 gcry_mpi_release (r_inv);
779 gcry_mpi_release (s);
782 ubsig = gcry_mpi_new (0);
783 gcry_mpi_mulm (ubsig, s, r_inv, n);
784 gcry_mpi_release (n);
785 gcry_mpi_release (r_inv);
786 gcry_mpi_release (s);
788 sret = GNUNET_new (struct GNUNET_CRYPTO_rsa_Signature);
790 gcry_sexp_build (&sret->sexp,
792 "(sig-val (rsa (s %M)))",
794 gcry_mpi_release (ubsig);
800 * Verify whether the given hash corresponds to the given signature and the
801 * signature is valid with respect to the given public key.
803 * @param hash hash of the message to verify to match the @a sig
804 * @param sig signature that is being validated
805 * @param public_key public key of the signer
806 * @returns #GNUNET_OK if ok, #GNUNET_SYSERR if invalid
809 GNUNET_CRYPTO_rsa_verify (const struct GNUNET_HashCode *hash,
810 const struct GNUNET_CRYPTO_rsa_Signature *sig,
811 const struct GNUNET_CRYPTO_rsa_PublicKey *public_key)
816 data = data_to_sexp (hash,
817 sizeof (struct GNUNET_HashCode));
818 rc = gcry_pk_verify (sig->sexp,
821 gcry_sexp_release (data);
824 LOG (GNUNET_ERROR_TYPE_WARNING,
825 _("RSA signature verification failed at %s:%d: %s\n"),
829 return GNUNET_SYSERR;
835 /* end of util/rsa.c */