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Don't preserve existing keys in DH_generate_key.

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This commit is contained in:
Bodo Möller 2001-07-25 17:20:34 +00:00
parent daba492c3a
commit 6aecef815c
3 changed files with 45 additions and 9 deletions
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31
CHANGES
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@ -12,6 +12,37 @@
*) applies to 0.9.6a/0.9.6b/0.9.6c and 0.9.7
+) applies to 0.9.7 only
*) In crypto/dh/dh_key.c, change generate_key() (the default
implementation of DH_generate_key()) so that a new key is
generated each time DH_generate_key() is used on a DH object.
Previously, DH_generate_key() did not change existing keys
-- but ssl/s3_srvr.c always expected it to do so (in effect,
SSL_OP_SINGLE_DH_USE was ignored in servers reusing the same SSL
object for multiple connections; however, each new SSL object
created from an SSL_CTX got its own key).
[Bodo Moeller]
*) In OpenSSL 0.9.6a and 0.9.6b, crypto/dh/dh_key.c ignored
dh->length and always used
BN_rand_range(priv_key, dh->p).
BN_rand_range() is not necessary for Diffie-Hellman, and this
specific range makes Diffie-Hellman unnecessarily inefficient if
dh->length (recommended exponent length) is much smaller than the
length of dh->p. We could use BN_rand_range() if the order of
the subgroup was stored in the DH structure, but we only have
dh->length.
So switch back to
BN_rand(priv_key, l, ...)
where 'l' is dh->length if this is defined, or BN_num_bits(dh->p)-1
otherwise.
[Bodo Moeller]
*) In
RSA_eay_public_encrypt

16
crypto/dh/dh_key.c
View File

@ -101,6 +101,7 @@ const DH_METHOD *DH_OpenSSL(void)
static int generate_key(DH *dh)
{
int ok=0;
unsigned l;
BN_CTX *ctx;
BN_MONT_CTX *mont;
BIGNUM *pub_key=NULL,*priv_key=NULL;
@ -112,9 +113,6 @@ static int generate_key(DH *dh)
{
priv_key=BN_new();
if (priv_key == NULL) goto err;
do
if (!BN_rand_range(priv_key, dh->p)) goto err;
while (BN_is_zero(priv_key));
}
else
priv_key=dh->priv_key;
@ -135,9 +133,15 @@ static int generate_key(DH *dh)
}
mont=(BN_MONT_CTX *)dh->method_mont_p;
if (!ENGINE_get_DH(dh->engine)->bn_mod_exp(dh, pub_key, dh->g,
priv_key,dh->p,ctx,mont))
goto err;
l = dh->length ? dh->length : BN_num_bits(dh->p)-1; /* secret exponent length */
do
{
if (!BN_rand(priv_key, l, 0, 0)) goto err;
if (!ENGINE_get_DH(dh->engine)->bn_mod_exp(dh, pub_key, dh->g,
priv_key,dh->p,ctx,mont)) goto err;
}
while (BN_is_one(priv_key));
dh->pub_key=pub_key;
dh->priv_key=priv_key;

7
doc/crypto/DH_generate_key.pod
View File

@ -21,9 +21,8 @@ value to compute the shared key.
DH_generate_key() expects B<dh> to contain the shared parameters
B<dh-E<gt>p> and B<dh-E<gt>g>. It generates a random private DH value
unless B<dh-E<gt>priv_key> is already set, and computes the
corresponding public value B<dh-E<gt>pub_key>, which can then be
published.
B<dh-E<gt>priv_key>, and it computes the corresponding public value
B<dh-E<gt>pub_key>, which can then be published.
DH_compute_key() computes the shared secret from the private DH value
in B<dh> and the other party's public value in B<pub_key> and stores
@ -46,5 +45,7 @@ L<dh(3)|dh(3)>, L<err(3)|err(3)>, L<rand(3)|rand(3)>, L<DH_size(3)|DH_size(3)>
DH_generate_key() and DH_compute_key() are available in all versions
of SSLeay and OpenSSL.
Up to version 0.9.6b, DH_generate_key() would not generate a new
key if B<dh-E<gt>priv_key> was already set.
=cut