diff options
| -rw-r--r-- | src/util/crypto_rsa.c | 41 |
1 files changed, 27 insertions, 14 deletions
diff --git a/src/util/crypto_rsa.c b/src/util/crypto_rsa.c index c09daa412d..cddb87bf79 100644 --- a/src/util/crypto_rsa.c +++ b/src/util/crypto_rsa.c @@ -393,6 +393,31 @@ GNUNET_CRYPTO_rsa_public_key_decode (const char *buf, /** + * 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 Asserts gcd(r,n) = 1 + */ +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); + GNUNET_assert( t ); + return t; +} + + +/** * Create a blinding key * * @param len length of the key in bits (i.e. 2048) @@ -406,7 +431,6 @@ rsa_blinding_key_derive (const struct GNUNET_CRYPTO_RsaPublicKey *pkey, char *xts = "Blinding KDF extrator HMAC key"; /* Trusts bks' randomness more */ struct RsaBlindingKey *blind; gcry_mpi_t n; - gcry_mpi_t g; blind = GNUNET_new (struct RsaBlindingKey); @@ -419,12 +443,7 @@ rsa_blinding_key_derive (const struct GNUNET_CRYPTO_RsaPublicKey *pkey, xts, strlen(xts), bks, sizeof(*bks), "Blinding KDF"); - - /* If gcd(*r,n) != 1 then n must be a malicious fake RSA key - designed to deanomize the user. */ - g = gcry_mpi_new (0); - GNUNET_assert( gcry_mpi_gcd(g,blind->r,n) ); - gcry_mpi_release (g); + rsa_gcd_validate(blind->r,n); gcry_mpi_release (n); return blind; @@ -661,7 +680,6 @@ rsa_full_domain_hash (gcry_mpi_t *r, gcry_mpi_t n; char *xts; size_t xts_len; - gcry_mpi_t g; /* Extract the composite n from the RSA public key */ GNUNET_assert( 0 == key_from_sexp (&n, pkey->sexp, "rsa", "n") ); @@ -678,14 +696,9 @@ rsa_full_domain_hash (gcry_mpi_t *r, xts, xts_len, hash, sizeof(*hash), "RSA-FDA FTpsW!"); - GNUNET_free (xts); - /* If gcd(*r,n) != 1 then n must be a malicious fake RSA key - designed to deanomize the user. */ - g = gcry_mpi_new (0); - GNUNET_assert( gcry_mpi_gcd(g,*r,n) ); - gcry_mpi_release (g); + rsa_gcd_validate(*r,n); gcry_mpi_release (n); } |