diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/util/crypto.c | 423 |
1 files changed, 0 insertions, 423 deletions
diff --git a/src/util/crypto.c b/src/util/crypto.c index 4f084b19c..a7ea4f4c5 100644 --- a/src/util/crypto.c +++ b/src/util/crypto.c @@ -25,18 +25,6 @@ #include "taler_util.h" #include <gcrypt.h> -/** - * Should we use the RSA blind signing implementation from libgnunetutil? The - * blinding only works correctly with a current version of libgnunetutil. - * - * Only applies to blinding and unblinding, but - * not to blind signing. - * - * FIXME: Can we define some macro for this in configure.ac - * to detect the version? - */ -#define USE_GNUNET_RSA_BLINDING 0 - /** * Function called by libgcrypt on serious errors. @@ -312,280 +300,6 @@ TALER_refresh_get_commitment (struct TALER_RefreshCommitmentP *rc, } -#if ! USE_GNUNET_RSA_BLINDING - - -/** - * The private information of an RSA key pair. - * - * FIXME: This declaration is evil, as it defines - * an opaque struct that is "owned" by GNUnet. - */ -struct GNUNET_CRYPTO_RsaPrivateKey -{ - /** - * Libgcrypt S-expression for the RSA private key. - */ - gcry_sexp_t sexp; -}; - - -/** - * The public information of an RSA key pair. - * - * FIXME: This declaration is evil, as it defines - * an opaque struct that is "owned" by GNUnet. - */ -struct GNUNET_CRYPTO_RsaPublicKey -{ - /** - * Libgcrypt S-expression for the RSA public key. - */ - gcry_sexp_t sexp; -}; - -/** - * @brief an RSA signature - * - * FIXME: This declaration is evil, as it defines - * an opaque struct that is "owned" by GNUnet. - */ -struct GNUNET_CRYPTO_RsaSignature -{ - /** - * Libgcrypt S-expression for the RSA signature. - */ - gcry_sexp_t sexp; -}; - -/** - * @brief RSA blinding key - */ -struct RsaBlindingKey -{ - /** - * Random value used for blinding. - */ - gcry_mpi_t r; -}; - - -/** - * Destroy a blinding key - * - * @param bkey the blinding key to destroy - */ -static void -rsa_blinding_key_free (struct RsaBlindingKey *bkey) -{ - gcry_mpi_release (bkey->r); - GNUNET_free (bkey); -} - - -/** - * Extract values from an S-expression. - * - * @param array where to store the result(s) - * @param sexp S-expression to parse - * @param topname top-level name in the S-expression that is of interest - * @param elems names of the elements to extract - * @return 0 on success - */ -static int -key_from_sexp (gcry_mpi_t *array, - gcry_sexp_t sexp, - const char *topname, - const char *elems) -{ - gcry_sexp_t list; - gcry_sexp_t l2; - const char *s; - unsigned int idx; - - if (! (list = gcry_sexp_find_token (sexp, topname, 0))) - return 1; - l2 = gcry_sexp_cadr (list); - gcry_sexp_release (list); - list = l2; - if (! list) - return 2; - idx = 0; - for (s = elems; *s; s++, idx++) - { - if (! (l2 = gcry_sexp_find_token (list, s, 1))) - { - for (unsigned int i = 0; i < idx; i++) - { - gcry_free (array[i]); - array[i] = NULL; - } - gcry_sexp_release (list); - return 3; /* required parameter not found */ - } - array[idx] = gcry_sexp_nth_mpi (l2, 1, GCRYMPI_FMT_USG); - gcry_sexp_release (l2); - if (! array[idx]) - { - for (unsigned int i = 0; i < idx; i++) - { - gcry_free (array[i]); - array[i] = NULL; - } - gcry_sexp_release (list); - return 4; /* required parameter is invalid */ - } - } - gcry_sexp_release (list); - return 0; -} - - -/** - * Test for malicious RSA key. - * - * Assuming n is an RSA modulous and r is generated using a call to - * GNUNET_CRYPTO_kdf_mod_mpi, if gcd(r,n) != 1 then n must be a - * malicious RSA key designed to deanomize the user. - * - * @param r KDF result - * @param n RSA modulus - * @return True if gcd(r,n) = 1, False means RSA key is malicious - */ -static int -rsa_gcd_validate (gcry_mpi_t r, gcry_mpi_t n) -{ - gcry_mpi_t g; - int t; - - g = gcry_mpi_new (0); - t = gcry_mpi_gcd (g, r, n); - gcry_mpi_release (g); - return t; -} - - -/** - * Computes a full domain hash seeded by the given public key. - * This gives a measure of provable security to the Taler exchange - * against one-more forgery attacks. See: - * https://eprint.iacr.org/2001/002.pdf - * http://www.di.ens.fr/~pointche/Documents/Papers/2001_fcA.pdf - * - * @param hash initial hash of the message to sign - * @param pkey the public key of the signer - * @return MPI value set to the FDH, NULL if RSA key is malicious - */ -static gcry_mpi_t -rsa_full_domain_hash (const struct GNUNET_CRYPTO_RsaPublicKey *pkey, - const struct GNUNET_HashCode *hash) -{ - gcry_mpi_t r, n; - void *xts; - size_t xts_len; - int ok; - - /* Extract the composite n from the RSA public key */ - GNUNET_assert (0 == key_from_sexp (&n, pkey->sexp, "rsa", "n")); - /* Assert that it at least looks like an RSA key */ - GNUNET_assert (0 == gcry_mpi_get_flag (n, GCRYMPI_FLAG_OPAQUE)); - - /* We key with the public denomination key as a homage to RSA-PSS by * - * Mihir Bellare and Phillip Rogaway. Doing this lowers the degree * - * of the hypothetical polyomial-time attack on RSA-KTI created by a * - * polynomial-time one-more forgary attack. Yey seeding! */ - xts_len = GNUNET_CRYPTO_rsa_public_key_encode (pkey, &xts); - - GNUNET_CRYPTO_kdf_mod_mpi (&r, - n, - xts, xts_len, - hash, sizeof(*hash), - "RSA-FDA FTpsW!"); - GNUNET_free (xts); - - ok = rsa_gcd_validate (r, n); - gcry_mpi_release (n); - if (ok) - return r; - gcry_mpi_release (r); - return NULL; -} - - -/** - * Create a blinding key - * - * @param pkey the public key to blind for - * @param bks pre-secret to use to derive the blinding key - * @return the newly created blinding key, NULL if RSA key is malicious - */ -static struct RsaBlindingKey * -rsa_blinding_key_derive (const struct GNUNET_CRYPTO_RsaPublicKey *pkey, - const struct GNUNET_CRYPTO_RsaBlindingKeySecret *bks) -{ - char *xts = "Blinding KDF extractor HMAC key"; /* Trusts bks' randomness more */ - struct RsaBlindingKey *blind; - gcry_mpi_t n; - - blind = GNUNET_new (struct RsaBlindingKey); - GNUNET_assert (NULL != blind); - - /* Extract the composite n from the RSA public key */ - GNUNET_assert (0 == key_from_sexp (&n, pkey->sexp, "rsa", "n")); - /* Assert that it at least looks like an RSA key */ - GNUNET_assert (0 == gcry_mpi_get_flag (n, GCRYMPI_FLAG_OPAQUE)); - - GNUNET_CRYPTO_kdf_mod_mpi (&blind->r, - n, - xts, strlen (xts), - bks, sizeof(*bks), - "Blinding KDF"); - if (0 == rsa_gcd_validate (blind->r, n)) - { - GNUNET_free (blind); - blind = NULL; - } - - gcry_mpi_release (n); - return blind; -} - - -/** - * Print an MPI to a newly created buffer - * - * @param v MPI to print. - * @param[out] buffer newly allocated buffer containing the result - * @return number of bytes stored in @a buffer - */ -static size_t -numeric_mpi_alloc_n_print (gcry_mpi_t v, - char **buffer) -{ - size_t n; - char *b; - size_t rsize; - - gcry_mpi_print (GCRYMPI_FMT_USG, - NULL, - 0, - &n, - v); - b = GNUNET_malloc (n); - GNUNET_assert (0 == - gcry_mpi_print (GCRYMPI_FMT_USG, - (unsigned char *) b, - n, - &rsize, - v)); - *buffer = b; - return n; -} - - -#endif /* ! USE_GNUNET_RSA_BLINDING */ - - enum GNUNET_GenericReturnValue TALER_rsa_blind (const struct GNUNET_HashCode *hash, const struct GNUNET_CRYPTO_RsaBlindingKeySecret *bks, @@ -593,75 +307,11 @@ TALER_rsa_blind (const struct GNUNET_HashCode *hash, void **buf, size_t *buf_size) { -#if USE_GNUNET_RSA_BLINDING return GNUNET_CRYPTO_rsa_blind (hash, bks, pkey, buf, buf_size); -#else - struct RsaBlindingKey *bkey; - gcry_mpi_t data; - gcry_mpi_t ne[2]; - gcry_mpi_t r_e; - gcry_mpi_t data_r_e; - int ret; - - GNUNET_assert (buf != NULL); - GNUNET_assert (buf_size != NULL); - ret = key_from_sexp (ne, pkey->sexp, "public-key", "ne"); - if (0 != ret) - ret = key_from_sexp (ne, pkey->sexp, "rsa", "ne"); - if (0 != ret) - { - GNUNET_break (0); - *buf = NULL; - *buf_size = 0; - return GNUNET_NO; - } - - data = rsa_full_domain_hash (pkey, hash); - if (NULL == data) - goto rsa_gcd_validate_failure; - - bkey = rsa_blinding_key_derive (pkey, bks); - if (NULL == bkey) - { - gcry_mpi_release (data); - goto rsa_gcd_validate_failure; - } - - r_e = gcry_mpi_new (0); - gcry_mpi_powm (r_e, - bkey->r, - ne[1], - ne[0]); - data_r_e = gcry_mpi_new (0); - gcry_mpi_mulm (data_r_e, - data, - r_e, - ne[0]); - gcry_mpi_release (data); - gcry_mpi_release (ne[0]); - gcry_mpi_release (ne[1]); - gcry_mpi_release (r_e); - rsa_blinding_key_free (bkey); - - *buf_size = numeric_mpi_alloc_n_print (data_r_e, - (char **) buf); - gcry_mpi_release (data_r_e); - - return GNUNET_YES; - -rsa_gcd_validate_failure: - /* We know the RSA key is malicious here, so warn the wallet. */ - /* GNUNET_break_op (0); */ - gcry_mpi_release (ne[0]); - gcry_mpi_release (ne[1]); - *buf = NULL; - *buf_size = 0; - return GNUNET_NO; -#endif } @@ -670,82 +320,9 @@ TALER_rsa_unblind (const struct GNUNET_CRYPTO_RsaSignature *sig, const struct GNUNET_CRYPTO_RsaBlindingKeySecret *bks, struct GNUNET_CRYPTO_RsaPublicKey *pkey) { -#if USE_GNUNET_RSA_BLINDING return GNUNET_CRYPTO_rsa_unblind (sig, bks, pkey); -#else - struct RsaBlindingKey *bkey; - gcry_mpi_t n; - gcry_mpi_t s; - gcry_mpi_t r_inv; - gcry_mpi_t ubsig; - int ret; - struct GNUNET_CRYPTO_RsaSignature *sret; - - ret = key_from_sexp (&n, pkey->sexp, "public-key", "n"); - if (0 != ret) - ret = key_from_sexp (&n, pkey->sexp, "rsa", "n"); - if (0 != ret) - { - GNUNET_break_op (0); - return NULL; - } - ret = key_from_sexp (&s, sig->sexp, "sig-val", "s"); - if (0 != ret) - ret = key_from_sexp (&s, sig->sexp, "rsa", "s"); - if (0 != ret) - { - gcry_mpi_release (n); - GNUNET_break_op (0); - return NULL; - } - - bkey = rsa_blinding_key_derive (pkey, bks); - if (NULL == bkey) - { - /* RSA key is malicious since rsa_gcd_validate failed here. - * It should have failed during GNUNET_CRYPTO_rsa_blind too though, - * so the exchange is being malicious in an unfamilair way, maybe - * just trying to crash us. */ - GNUNET_break_op (0); - gcry_mpi_release (n); - gcry_mpi_release (s); - return NULL; - } - - r_inv = gcry_mpi_new (0); - if (1 != - gcry_mpi_invm (r_inv, - bkey->r, - n)) - { - /* We cannot find r mod n, so gcd(r,n) != 1, which should get * - * caught above, but we handle it the same here. */ - GNUNET_break_op (0); - gcry_mpi_release (r_inv); - rsa_blinding_key_free (bkey); - gcry_mpi_release (n); - gcry_mpi_release (s); - return NULL; - } - - ubsig = gcry_mpi_new (0); - gcry_mpi_mulm (ubsig, s, r_inv, n); - gcry_mpi_release (n); - gcry_mpi_release (r_inv); - gcry_mpi_release (s); - rsa_blinding_key_free (bkey); - - sret = GNUNET_new (struct GNUNET_CRYPTO_RsaSignature); - GNUNET_assert (0 == - gcry_sexp_build (&sret->sexp, - NULL, - "(sig-val (rsa (s %M)))", - ubsig)); - gcry_mpi_release (ubsig); - return sret; -#endif } |