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(DH_check_pubkey): doxygen + if g == 2, pub_key have more then one bit

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set, if bits set is 1, log_2(pub_key) is trival


git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@22222 ec53bebd-3082-4978-b11e-865c3cabbd6b
This commit is contained in:
Love Hörnquist Åstrand
2007-12-08 16:40:59 +00:00
parent 7ad26a420f
commit 0d71c026fa
1 changed files with 44 additions and 4 deletions
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48
lib/hcrypto/dh.c
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@@ -149,12 +149,17 @@ DH_generate_parameters_ex(DH *dh, int prime_len, int generator, BN_GENCB *cb)
return 0;
}
/*
* Check that
/**
* Check that the public key is sane.
*
* pub_key > 1 and pub_key < p - 1
* @param dh the local peer DH parameters.
* @param pub_key the remote peer public key parameters.
* @param codes return that the failures of the pub_key are.
*
* to avoid small subgroups attack.
* @return 1 on success, 0 on failure and *codes is set the the
* combined fail check for the public key
*
* @ingroup hcrypto_dh
*/
int
@@ -165,6 +170,19 @@ DH_check_pubkey(const DH *dh, const BIGNUM *pub_key, int *codes)
*codes = 0;
/**
* Checks that the function performs are:
* - pub_key is not negative
*/
if (BN_is_negative(pub_key))
goto out;
/**
* - pub_key > 1 and pub_key < p - 1,
* to avoid small subgroups attack.
*/
bn = BN_new();
if (bn == NULL)
goto out;
@@ -184,6 +202,28 @@ DH_check_pubkey(const DH *dh, const BIGNUM *pub_key, int *codes)
if (BN_cmp(sum, dh->p) >= 0)
*codes |= DH_CHECK_PUBKEY_TOO_LARGE;
/**
* - if g == 2, pub_key have more then one bit set,
* if bits set is 1, log_2(pub_key) is trival
*/
if (!BN_set_word(bn, 2))
goto out;
if (BN_cmp(bn, pub_key) == 0) {
unsigned i, n = BN_num_bits(pub_key);
unsigned bits = 0;
for (i = 0; i <= n; i++)
if (BN_is_bit_set(pub_key, i))
bits++;
if (bits > 1) {
*codes |= DH_CHECK_PUBKEY_TOO_SMALL;
goto out;
}
}
ret = 1;
out:
if (bn)