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Protocol version selection and negotiation rewrite

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The protocol selection code is now consolidated in a few consecutive
short functions in a single file and is table driven.  Protocol-specific
constraints that influence negotiation are moved into the flags
field of the method structure.  The same protocol version constraints
are now applied in all code paths.  It is now much easier to add
new protocol versions without reworking the protocol selection
logic.

In the presence of "holes" in the list of enabled client protocols
we no longer select client protocols below the hole based on a
subset of the constraints and then fail shortly after when it is
found that these don't meet the remaining constraints (suiteb, FIPS,
security level, ...).  Ideally, with the new min/max controls users
will be less likely to create "holes" in the first place.

Reviewed-by: Kurt Roeckx <kurt@openssl.org>
This commit is contained in:
Viktor Dukhovni
2015-12-29 03:24:17 -05:00
parent 57ce7b617c
commit 4fa52141b0
16 changed files with 543 additions and 479 deletions
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27
ssl/s3_lib.c
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@@ -3777,33 +3777,6 @@ long ssl3_ctrl(SSL *s, int cmd, long larg, void *parg)
}
#endif
case SSL_CTRL_CHECK_PROTO_VERSION:
/*
* For library-internal use; checks that the current protocol is the
* highest enabled version (according to s->ctx->method, as version
* negotiation may have changed s->method).
*/
if (s->version == s->ctx->method->version)
return 1;
/*
* Apparently we're using a version-flexible SSL_METHOD (not at its
* highest protocol version).
*/
if (s->ctx->method->version == TLS_method()->version) {
#if TLS_MAX_VERSION != TLS1_2_VERSION
# error Code needs update for TLS_method() support beyond TLS1_2_VERSION.
#endif
if (!(s->options & SSL_OP_NO_TLSv1_2))
return s->version == TLS1_2_VERSION;
if (!(s->options & SSL_OP_NO_TLSv1_1))
return s->version == TLS1_1_VERSION;
if (!(s->options & SSL_OP_NO_TLSv1))
return s->version == TLS1_VERSION;
if (!(s->options & SSL_OP_NO_SSLv3))
return s->version == SSL3_VERSION;
}
return 0; /* Unexpected state; fail closed. */
default:
break;
}