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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_crypto_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;
225 key = GNUNET_new (struct GNUNET_CRYPTO_rsa_PrivateKey);
227 gcry_sexp_new (&key->sexp,
232 LOG (GNUNET_ERROR_TYPE_WARNING,
233 "Decoded private key is not valid\n");
237 if (0 != gcry_pk_testkey (key->sexp))
239 LOG (GNUNET_ERROR_TYPE_WARNING,
240 "Decoded private key is not valid\n");
241 GNUNET_CRYPTO_rsa_private_key_free (key);
249 * Extract the public key of the given private key.
251 * @param priv the private key
252 * @retur NULL on error, otherwise the public key
254 struct GNUNET_CRYPTO_rsa_PublicKey *
255 GNUNET_CRYPTO_rsa_private_key_get_public (const struct GNUNET_CRYPTO_rsa_PrivateKey *priv)
257 struct GNUNET_CRYPTO_rsa_PublicKey *pub;
262 rc = key_from_sexp (ne, priv->sexp, "public-key", "ne");
264 rc = key_from_sexp (ne, priv->sexp, "private-key", "ne");
266 rc = key_from_sexp (ne, priv->sexp, "rsa", "ne");
272 rc = gcry_sexp_build (&result,
274 "(public-key(rsa(n %m)(e %m)))",
277 gcry_mpi_release (ne[0]);
278 gcry_mpi_release (ne[1]);
279 pub = GNUNET_new (struct GNUNET_CRYPTO_rsa_PublicKey);
286 * Free memory occupied by the public key.
288 * @param key pointer to the memory to free
291 GNUNET_CRYPTO_rsa_public_key_free (struct GNUNET_CRYPTO_rsa_PublicKey *key)
293 gcry_sexp_release (key->sexp);
299 * Encode the public key in a format suitable for
300 * storing it into a file.
302 * @param key the private key
303 * @param[out] buffer set to a buffer with the encoded key
304 * @return size of memory allocated in @a buffer
307 GNUNET_CRYPTO_rsa_public_key_encode (const struct GNUNET_CRYPTO_rsa_PublicKey *key,
313 n = gcry_sexp_sprint (key->sexp,
314 GCRYSEXP_FMT_ADVANCED,
317 b = GNUNET_malloc (n);
318 GNUNET_assert ((n -1) == /* since the last byte is \0 */
319 gcry_sexp_sprint (key->sexp,
320 GCRYSEXP_FMT_ADVANCED,
329 * Compute hash over the public key.
331 * @param key public key to hash
332 * @param hc where to store the hash code
335 GNUNET_CRYPTO_rsa_public_key_hash (const struct GNUNET_CRYPTO_rsa_PublicKey *key,
336 struct GNUNET_HashCode *hc)
341 buf_size = GNUNET_CRYPTO_rsa_public_key_encode (key,
343 GNUNET_CRYPTO_hash (buf,
351 * Decode the public key from the data-format back
352 * to the "normal", internal format.
354 * @param buf the buffer where the public key data is stored
355 * @param len the length of the data in @a buf
356 * @return NULL on error
358 struct GNUNET_CRYPTO_rsa_PublicKey *
359 GNUNET_CRYPTO_rsa_public_key_decode (const char *buf,
362 struct GNUNET_CRYPTO_rsa_PublicKey *key;
366 key = GNUNET_new (struct GNUNET_CRYPTO_rsa_PublicKey);
368 gcry_sexp_new (&key->sexp,
377 /* verify that this is an RSA public key */
378 ret = key_from_sexp (&n, key->sexp, "public-key", "n");
380 ret = key_from_sexp (&n, key->sexp, "rsa", "n");
383 /* this is no public RSA key */
385 gcry_sexp_release (key->sexp);
389 gcry_mpi_release (n);
395 * Create a blinding key
397 * @param len length of the key in bits (i.e. 2048)
398 * @return the newly created blinding key
400 struct GNUNET_CRYPTO_rsa_BlindingKey *
401 GNUNET_CRYPTO_rsa_blinding_key_create (unsigned int len)
403 struct GNUNET_CRYPTO_rsa_BlindingKey *blind;
405 blind = GNUNET_new (struct GNUNET_CRYPTO_rsa_BlindingKey);
406 blind->r = gcry_mpi_new (len);
407 gcry_mpi_randomize (blind->r,
415 * Compare the values of two blinding keys.
418 * @param b2 the other key
419 * @return 0 if the two are equal
422 GNUNET_CRYPTO_rsa_blinding_key_cmp (struct GNUNET_CRYPTO_rsa_BlindingKey *b1,
423 struct GNUNET_CRYPTO_rsa_BlindingKey *b2)
425 return gcry_mpi_cmp (b1->r,
431 * Compare the values of two signatures.
433 * @param s1 one signature
434 * @param s2 the other signature
435 * @return 0 if the two are equal
438 GNUNET_CRYPTO_rsa_signature_cmp (struct GNUNET_CRYPTO_rsa_Signature *s1,
439 struct GNUNET_CRYPTO_rsa_Signature *s2)
447 z1 = GNUNET_CRYPTO_rsa_signature_encode (s1,
449 z2 = GNUNET_CRYPTO_rsa_signature_encode (s2,
464 * Compare the values of two public keys.
466 * @param p1 one public key
467 * @param p2 the other public key
468 * @return 0 if the two are equal
471 GNUNET_CRYPTO_rsa_public_key_cmp (struct GNUNET_CRYPTO_rsa_PublicKey *p1,
472 struct GNUNET_CRYPTO_rsa_PublicKey *p2)
480 z1 = GNUNET_CRYPTO_rsa_public_key_encode (p1,
482 z2 = GNUNET_CRYPTO_rsa_public_key_encode (p2,
497 * Compare the values of two private keys.
499 * @param p1 one private key
500 * @param p2 the other private key
501 * @return 0 if the two are equal
504 GNUNET_CRYPTO_rsa_private_key_cmp (struct GNUNET_CRYPTO_rsa_PrivateKey *p1,
505 struct GNUNET_CRYPTO_rsa_PrivateKey *p2)
513 z1 = GNUNET_CRYPTO_rsa_private_key_encode (p1,
515 z2 = GNUNET_CRYPTO_rsa_private_key_encode (p2,
530 * Obtain the length of the RSA key in bits.
532 * @param key the public key to introspect
533 * @return length of the key in bits
536 GNUNET_CRYPTO_rsa_public_key_len (const struct GNUNET_CRYPTO_rsa_PublicKey *key)
542 ret = key_from_sexp (&n, key->sexp, "rsa", "n");
545 /* this is no public RSA key */
549 rval = gcry_mpi_get_nbits (n);
550 gcry_mpi_release (n);
556 * Destroy a blinding key
558 * @param bkey the blinding key to destroy
561 GNUNET_CRYPTO_rsa_blinding_key_free (struct GNUNET_CRYPTO_rsa_BlindingKey *bkey)
563 gcry_mpi_release (bkey->r);
569 * Encode the blinding key in a format suitable for
570 * storing it into a file.
572 * @param bkey the blinding key
573 * @param[out] buffer set to a buffer with the encoded key
574 * @return size of memory allocated in @a buffer
577 GNUNET_CRYPTO_rsa_blinding_key_encode (const struct GNUNET_CRYPTO_rsa_BlindingKey *bkey,
584 gcry_mpi_print (GCRYMPI_FMT_USG,
589 b = GNUNET_malloc (n);
591 gcry_mpi_print (GCRYMPI_FMT_USG,
602 * Decode the blinding key from the data-format back
603 * to the "normal", internal format.
605 * @param buf the buffer where the public key data is stored
606 * @param len the length of the data in @a buf
607 * @return NULL on error
609 struct GNUNET_CRYPTO_rsa_BlindingKey *
610 GNUNET_CRYPTO_rsa_blinding_key_decode (const char *buf,
613 struct GNUNET_CRYPTO_rsa_BlindingKey *bkey;
616 bkey = GNUNET_new (struct GNUNET_CRYPTO_rsa_BlindingKey);
618 gcry_mpi_scan (&bkey->r,
620 (const unsigned char *) buf,
633 * Blinds the given message with the given blinding key
635 * @param hash hash of the message to sign
636 * @param bkey the blinding key
637 * @param pkey the public key of the signer
638 * @param[out] buffer set to a buffer with the blinded message to be signed
639 * @return number of bytes stored in @a buffer
642 GNUNET_CRYPTO_rsa_blind (const struct GNUNET_HashCode *hash,
643 struct GNUNET_CRYPTO_rsa_BlindingKey *bkey,
644 struct GNUNET_CRYPTO_rsa_PublicKey *pkey,
657 ret = key_from_sexp (ne, pkey->sexp, "public-key", "ne");
659 ret = key_from_sexp (ne, pkey->sexp, "rsa", "ne");
666 if (0 != (rc = gcry_mpi_scan (&data,
668 (const unsigned char *) hash,
669 sizeof (struct GNUNET_HashCode),
673 gcry_mpi_release (ne[0]);
674 gcry_mpi_release (ne[1]);
678 r_e = gcry_mpi_new (0);
683 data_r_e = gcry_mpi_new (0);
684 gcry_mpi_mulm (data_r_e,
688 gcry_mpi_release (data);
689 gcry_mpi_release (ne[0]);
690 gcry_mpi_release (ne[1]);
691 gcry_mpi_release (r_e);
693 gcry_mpi_print (GCRYMPI_FMT_USG,
698 b = GNUNET_malloc (n);
699 rc = gcry_mpi_print (GCRYMPI_FMT_USG,
704 gcry_mpi_release (data_r_e);
711 * Convert the data specified in the given purpose argument to an
712 * S-expression suitable for signature operations.
714 * @param ptr pointer to the data to convert
715 * @param size the size of the data
716 * @return converted s-expression
719 data_to_sexp (const void *ptr, size_t size)
727 gcry_mpi_scan (&value,
733 gcry_sexp_build (&data,
735 "(data (flags raw) (value %M))",
737 gcry_mpi_release (value);
743 * Sign the given message.
745 * @param key private key to use for the signing
746 * @param msg the message to sign
747 * @param msg_len number of bytes in @a msg to sign
748 * @return NULL on error, signature on success
750 struct GNUNET_CRYPTO_rsa_Signature *
751 GNUNET_CRYPTO_rsa_sign (const struct GNUNET_CRYPTO_rsa_PrivateKey *key,
755 struct GNUNET_CRYPTO_rsa_Signature *sig;
756 struct GNUNET_CRYPTO_rsa_PublicKey *public_key;
760 data = data_to_sexp (msg,
763 gcry_pk_sign (&result,
771 /* verify signature (guards against Lenstra's attack with fault injection...) */
772 public_key = GNUNET_CRYPTO_rsa_private_key_get_public (key);
774 gcry_pk_verify (result,
779 GNUNET_CRYPTO_rsa_public_key_free (public_key);
780 gcry_sexp_release (data);
781 gcry_sexp_release (result);
784 GNUNET_CRYPTO_rsa_public_key_free (public_key);
786 /* return signature */
787 gcry_sexp_release (data);
788 sig = GNUNET_new (struct GNUNET_CRYPTO_rsa_Signature);
795 * Free memory occupied by signature.
797 * @param sig memory to freee
800 GNUNET_CRYPTO_rsa_signature_free (struct GNUNET_CRYPTO_rsa_Signature *sig)
802 gcry_sexp_release (sig->sexp);
808 * Encode the given signature in a format suitable for storing it into a file.
810 * @param sig the signature
811 * @param[out] buffer set to a buffer with the encoded key
812 * @return size of memory allocated in @a buffer
815 GNUNET_CRYPTO_rsa_signature_encode (const struct GNUNET_CRYPTO_rsa_Signature *sig,
821 n = gcry_sexp_sprint (sig->sexp,
822 GCRYSEXP_FMT_ADVANCED,
825 b = GNUNET_malloc (n);
826 GNUNET_assert ((n - 1) == /* since the last byte is \0 */
827 gcry_sexp_sprint (sig->sexp,
828 GCRYSEXP_FMT_ADVANCED,
837 * Decode the signature from the data-format back to the "normal", internal
840 * @param buf the buffer where the public key data is stored
841 * @param len the length of the data in @a buf
842 * @return NULL on error
844 struct GNUNET_CRYPTO_rsa_Signature *
845 GNUNET_CRYPTO_rsa_signature_decode (const char *buf,
848 struct GNUNET_CRYPTO_rsa_Signature *sig;
852 sig = GNUNET_new (struct GNUNET_CRYPTO_rsa_Signature);
854 gcry_sexp_new (&sig->sexp,
863 /* verify that this is an RSA signature */
864 ret = key_from_sexp (&s, sig->sexp, "sig-val", "s");
866 ret = key_from_sexp (&s, sig->sexp, "rsa", "s");
869 /* this is no RSA Signature */
871 gcry_sexp_release (sig->sexp);
875 gcry_mpi_release (s);
881 * Duplicate the given public key
883 * @param key the public key to duplicate
884 * @return the duplicate key; NULL upon error
886 struct GNUNET_CRYPTO_rsa_PublicKey *
887 GNUNET_CRYPTO_rsa_public_key_dup (const struct GNUNET_CRYPTO_rsa_PublicKey *key)
889 struct GNUNET_CRYPTO_rsa_PublicKey *dup;
890 gcry_sexp_t dup_sexp;
893 /* check if we really are exporting a public key */
894 dup_sexp = gcry_sexp_find_token (key->sexp, "public-key", 0);
895 GNUNET_assert (NULL != dup_sexp);
896 gcry_sexp_release (dup_sexp);
898 GNUNET_assert (0 == gcry_sexp_build (&dup_sexp, &erroff, "%S", key->sexp));
899 dup = GNUNET_new (struct GNUNET_CRYPTO_rsa_PublicKey);
900 dup->sexp = dup_sexp;
906 * Unblind a blind-signed signature. The signature should have been generated
907 * with #GNUNET_CRYPTO_rsa_sign() using a hash that was blinded with
908 * #GNUNET_CRYPTO_rsa_blind().
910 * @param sig the signature made on the blinded signature purpose
911 * @param bkey the blinding key used to blind the signature purpose
912 * @param pkey the public key of the signer
913 * @return unblinded signature on success, NULL on error
915 struct GNUNET_CRYPTO_rsa_Signature *
916 GNUNET_CRYPTO_rsa_unblind (struct GNUNET_CRYPTO_rsa_Signature *sig,
917 struct GNUNET_CRYPTO_rsa_BlindingKey *bkey,
918 struct GNUNET_CRYPTO_rsa_PublicKey *pkey)
925 struct GNUNET_CRYPTO_rsa_Signature *sret;
927 ret = key_from_sexp (&n, pkey->sexp, "public-key", "n");
929 ret = key_from_sexp (&n, pkey->sexp, "rsa", "n");
935 ret = key_from_sexp (&s, sig->sexp, "sig-val", "s");
937 ret = key_from_sexp (&s, sig->sexp, "rsa", "s");
940 gcry_mpi_release (n);
944 r_inv = gcry_mpi_new (0);
946 gcry_mpi_invm (r_inv,
951 gcry_mpi_release (n);
952 gcry_mpi_release (r_inv);
953 gcry_mpi_release (s);
956 ubsig = gcry_mpi_new (0);
957 gcry_mpi_mulm (ubsig, s, r_inv, n);
958 gcry_mpi_release (n);
959 gcry_mpi_release (r_inv);
960 gcry_mpi_release (s);
962 sret = GNUNET_new (struct GNUNET_CRYPTO_rsa_Signature);
964 gcry_sexp_build (&sret->sexp,
966 "(sig-val (rsa (s %M)))",
968 gcry_mpi_release (ubsig);
974 * Verify whether the given hash corresponds to the given signature and the
975 * signature is valid with respect to the given public key.
977 * @param hash hash of the message to verify to match the @a sig
978 * @param sig signature that is being validated
979 * @param public_key public key of the signer
980 * @returns #GNUNET_OK if ok, #GNUNET_SYSERR if invalid
983 GNUNET_CRYPTO_rsa_verify (const struct GNUNET_HashCode *hash,
984 const struct GNUNET_CRYPTO_rsa_Signature *sig,
985 const struct GNUNET_CRYPTO_rsa_PublicKey *public_key)
990 data = data_to_sexp (hash,
991 sizeof (struct GNUNET_HashCode));
992 rc = gcry_pk_verify (sig->sexp,
995 gcry_sexp_release (data);
998 LOG (GNUNET_ERROR_TYPE_WARNING,
999 _("RSA signature verification failed at %s:%d: %s\n"),
1002 gcry_strerror (rc));
1003 return GNUNET_SYSERR;
1010 * Duplicate the given private key
1012 * @param key the private key to duplicate
1013 * @return the duplicate key; NULL upon error
1015 struct GNUNET_CRYPTO_rsa_PrivateKey *
1016 GNUNET_CRYPTO_rsa_private_key_dup (const struct GNUNET_CRYPTO_rsa_PrivateKey *key)
1018 struct GNUNET_CRYPTO_rsa_PrivateKey *dup;
1019 gcry_sexp_t dup_sexp;
1022 /* check if we really are exporting a private key */
1023 dup_sexp = gcry_sexp_find_token (key->sexp, "private-key", 0);
1024 GNUNET_assert (NULL != dup_sexp);
1025 gcry_sexp_release (dup_sexp);
1027 GNUNET_assert (0 == gcry_sexp_build (&dup_sexp, &erroff, "%S", key->sexp));
1028 dup = GNUNET_new (struct GNUNET_CRYPTO_rsa_PrivateKey);
1029 dup->sexp = dup_sexp;
1035 * Duplicate the given private key
1037 * @param key the private key to duplicate
1038 * @return the duplicate key; NULL upon error
1040 struct GNUNET_CRYPTO_rsa_Signature *
1041 GNUNET_CRYPTO_rsa_signature_dup (const struct GNUNET_CRYPTO_rsa_Signature *sig)
1043 struct GNUNET_CRYPTO_rsa_Signature *dup;
1044 gcry_sexp_t dup_sexp;
1049 /* verify that this is an RSA signature */
1050 ret = key_from_sexp (&s, sig->sexp, "sig-val", "s");
1052 ret = key_from_sexp (&s, sig->sexp, "rsa", "s");
1053 GNUNET_assert (0 == ret);
1054 gcry_mpi_release (s);
1056 GNUNET_assert (0 == gcry_sexp_build (&dup_sexp, &erroff, "%S", sig->sexp));
1057 dup = GNUNET_new (struct GNUNET_CRYPTO_rsa_Signature);
1058 dup->sexp = dup_sexp;
1063 /* end of util/rsa.c */