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refining changeset 4483 by introducing charon.dh_exponent_ansi_x9_42 key

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This commit is contained in:
Andreas Steffen
2008-10-28 01:59:01 +00:00
parent 85ac2fa547
commit f5ab7f5f57
3 changed files with 62 additions and 27 deletions
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src/libstrongswan/plugins/gmp/gmp_diffie_hellman.c
+35 -11
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@@ -303,6 +303,11 @@ struct modulus_entry_t {
*/
size_t modulus_len;
/*
* Optimum length of exponent in bytes.
*/
size_t opt_exponent_len;
/*
* Generator value.
*/
@@ -310,17 +315,17 @@ struct modulus_entry_t {
};
/**
* All supported modulus values.
* All supported modulus values - optimum exponent size according to RFC 3526.
*/
static modulus_entry_t modulus_entries[] = {
{MODP_768_BIT, group1_modulus, sizeof(group1_modulus), 2},
{MODP_1024_BIT, group2_modulus, sizeof(group2_modulus), 2},
{MODP_1536_BIT, group5_modulus, sizeof(group5_modulus), 2},
{MODP_2048_BIT, group14_modulus, sizeof(group14_modulus), 2},
{MODP_3072_BIT, group15_modulus, sizeof(group15_modulus), 2},
{MODP_4096_BIT, group16_modulus, sizeof(group16_modulus), 2},
{MODP_6144_BIT, group17_modulus, sizeof(group17_modulus), 2},
{MODP_8192_BIT, group18_modulus, sizeof(group18_modulus), 2},
{MODP_768_BIT, group1_modulus, sizeof(group1_modulus), 32, 2},
{MODP_1024_BIT, group2_modulus, sizeof(group2_modulus), 32, 2},
{MODP_1536_BIT, group5_modulus, sizeof(group5_modulus), 32, 2},
{MODP_2048_BIT, group14_modulus, sizeof(group14_modulus), 48, 2},
{MODP_3072_BIT, group15_modulus, sizeof(group15_modulus), 48, 2},
{MODP_4096_BIT, group16_modulus, sizeof(group16_modulus), 64, 2},
{MODP_6144_BIT, group17_modulus, sizeof(group17_modulus), 64, 2},
{MODP_8192_BIT, group18_modulus, sizeof(group18_modulus), 64, 2},
};
typedef struct private_gmp_diffie_hellman_t private_gmp_diffie_hellman_t;
@@ -374,6 +379,11 @@ struct private_gmp_diffie_hellman_t {
*/
size_t p_len;
/**
* Optimal exponent length.
*/
size_t opt_exponent_len;
/**
* True if shared secret is computed and stored in my_public_value.
*/
@@ -504,6 +514,7 @@ static status_t set_modulus(private_gmp_diffie_hellman_t *this)
chunk.len = modulus_entries[i].modulus_len;
mpz_import(this->p, chunk.len, 1, 1, 1, 0, chunk.ptr);
this->p_len = chunk.len;
this->opt_exponent_len = modulus_entries[i].opt_exponent_len;
mpz_set_ui(this->g, modulus_entries[i].generator);
status = SUCCESS;
break;
@@ -534,6 +545,8 @@ gmp_diffie_hellman_t *gmp_diffie_hellman_create(diffie_hellman_group_t group)
private_gmp_diffie_hellman_t *this = malloc_thing(private_gmp_diffie_hellman_t);
rng_t *rng;
chunk_t random;
bool ansi_x9_42;
size_t exponent_len;
/* public functions */
this->public.dh.get_shared_secret = (status_t (*)(diffie_hellman_t *, chunk_t *)) get_shared_secret;
@@ -567,11 +580,22 @@ gmp_diffie_hellman_t *gmp_diffie_hellman_create(diffie_hellman_group_t group)
destroy(this);
return NULL;
}
rng->allocate_bytes(rng, DH_EXPONENT_ENTROPY_SIZE / BITS_PER_BYTE, &random);
ansi_x9_42 = lib->settings->get_int(lib->settings,
"charon.dh_exponent_ansi_x9_42", TRUE);
exponent_len = (ansi_x9_42) ? this->p_len : this->opt_exponent_len;
rng->allocate_bytes(rng, exponent_len, &random);
rng->destroy(rng);
if (ansi_x9_42)
{
/* achieve bitsof(p)-1 by setting MSB to 0 */
*random.ptr &= 0x7F;
}
mpz_import(this->xa, random.len, 1, 1, 1, 0, random.ptr);
chunk_free(&random);
DBG2("size of DH secret exponent: %u bits", mpz_sizeinbase(this->xa, 2));
mpz_powm(this->ya, this->g, this->xa, this->p);
return &this->public;