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RT1744: SSL_CTX_set_dump_dh() doc feedback

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The description of when the server creates a DH key is
confusing.  This cleans it up.
(rsalz: also removed trailing whitespace.)

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
This commit is contained in:
David Gatwood 2014-08-26 13:02:03 -04:00 committed by Rich Salz
parent fd4592be3a
commit fa60b90950
1 changed files with 9 additions and 7 deletions
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16
doc/ssl/SSL_CTX_set_tmp_dh_callback.pod
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@ -48,12 +48,13 @@ even if he gets hold of the normal (certified) key, as this key was
only used for signing.
In order to perform a DH key exchange the server must use a DH group
(DH parameters) and generate a DH key. The server will always generate a new
DH key during the negotiation, when the DH parameters are supplied via
callback and/or when the SSL_OP_SINGLE_DH_USE option of
L<SSL_CTX_set_options(3)|SSL_CTX_set_options(3)> is set. It will
immediately create a DH key, when DH parameters are supplied via
SSL_CTX_set_tmp_dh() and SSL_OP_SINGLE_DH_USE is not set. In this case,
(DH parameters) and generate a DH key.
The server will always generate a new DH key during the negotiation
if either the DH parameters are supplied via callback or the
SSL_OP_SINGLE_DH_USE option of SSL_CTX_set_options(3) is set (or both).
It will immediately create a DH key if DH parameters are supplied via
SSL_CTX_set_tmp_dh() and SSL_OP_SINGLE_DH_USE is not set.
In this case,
it may happen that a key is generated on initialization without later
being needed, while on the other hand the computer time during the
negotiation is being saved.
@ -66,6 +67,7 @@ in order to prevent small subgroup attacks. Always using SSL_OP_SINGLE_DH_USE
has an impact on the computer time needed during negotiation, but it is not
very large, so application authors/users should consider to always enable
this option.
The option is required to implement perfect forward secrecy (PFS).
As generating DH parameters is extremely time consuming, an application
should not generate the parameters on the fly but supply the parameters.
@ -139,7 +141,7 @@ partly left out.)
dh_tmp = dh_512;
break;
case 1024:
if (!dh_1024)
if (!dh_1024)
dh_1024 = get_dh1024();
dh_tmp = dh_1024;
break;