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gcrypt: Move shared secret calculation to get_shared_secret()

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This commit is contained in:
Tobias Brunner 2021-07-23 16:29:44 +02:00
parent ed3494ef7b
commit d95082ce0d
1 changed files with 15 additions and 17 deletions
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32
src/libstrongswan/plugins/gcrypt/gcrypt_dh.c
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@ -100,25 +100,22 @@ METHOD(key_exchange_t, set_public_key, bool,
p_min_1 = gcry_mpi_new(this->p_len * 8);
gcry_mpi_sub_ui(p_min_1, this->p, 1);
/* check public value:
* 1. 0 or 1 is invalid as 0^a = 0 and 1^a = 1
* 2. a public value larger or equal the modulus is invalid */
if (gcry_mpi_cmp_ui(this->yb, 1) > 0 &&
gcry_mpi_cmp(this->yb, p_min_1) < 0)
/* check that the public value y satisfies 1 < y < p-1.
* according to RFC 6989, section 2.1, this is enough for the common safe-
* prime DH groups (i.e. with q=(p-1)/2 being prime) and also for those
* with small subgroups (22, 23, 24) if private keys are not reused, which
* we never do and explicitly prevent by not resetting this->zz when a
* different public key is set. */
if (gcry_mpi_cmp_ui(this->yb, 1) <= 0 ||
gcry_mpi_cmp(this->yb, p_min_1) >= 0)
{
if (!this->zz)
{
this->zz = gcry_mpi_new(this->p_len * 8);
}
gcry_mpi_powm(this->zz, this->yb, this->xa, this->p);
}
else
{
DBG1(DBG_LIB, "public DH value verification failed:"
" y < 2 || y > p - 1 ");
DBG1(DBG_LIB, "public DH value verification failed: "
"y <= 1 || y >= p - 1");
gcry_mpi_release(p_min_1);
return FALSE;
}
gcry_mpi_release(p_min_1);
return this->zz != NULL;
return TRUE;
}
/**
@ -169,7 +166,8 @@ METHOD(key_exchange_t, get_shared_secret, bool,
{
if (!this->zz)
{
return FALSE;
this->zz = gcry_mpi_new(this->p_len * 8);
gcry_mpi_powm(this->zz, this->yb, this->xa, this->p);
}
*secret = export_mpi(this->zz, this->p_len);
return TRUE;