Clean up the EC key/curve configuration handling.

Over the years OpenSSL grew multiple ways of being able to specify EC keys
(and/or curves) for use with ECDH and ECDHE key exchange. You could specify
a static EC key (SSL{_CTX,}_set_tmp_ecdh()), use that as a curve and
generate ephemeral keys (SSL_OP_SINGLE_ECDH_USE), provide the EC key via
a callback that was provided with insufficient information
(SSL{_CTX,}_set_tmp_ecdh_cb()) or enable automatic selection and generation
of EC keys via SSL{_CTX,}_set_ecdh_auto(). This complexity leads to
problems (like ECDHE not being enabled) and potential weird configuration
(like being able to do ECDHE without the ephemeral part...).

We no longer support ECDH and ECDHE can be disabled by removing ECDHE
ciphers from the cipher list. As such, permanently enable automatic EC
curve selection and generation, effectively disabling all of the
configuration knobs. The only exception is the
SSL{_CTX,}_set_tmp_ecdh() functions, which retain part of their previous
behaviour by configuring the curve of the given EC key as the only curve
being enabled. Everything else becomes a no-op.

ok beck@ doug@

1 files changed, 14 insertions, 44 deletions

diff --git a/src/lib/libssl/s3_lib.c b/src/lib/libssl/s3_lib.c
index 1abe01cd88..abebaa0fc4 100644
--- a/src/lib/libssl/s3_lib.c
+++ b/src/lib/libssl/s3_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_lib.c,v 1.154 2017/08/09 17:49:54 jsing Exp $ */
+/* $OpenBSD: s3_lib.c,v 1.155 2017/08/10 17:18:38 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1838,39 +1838,26 @@ _SSL_set_dh_auto(SSL *s, int state)
 static int
 _SSL_set_tmp_ecdh(SSL *s, EC_KEY *ecdh)
 {
+        const EC_GROUP *group;
+        int nid;
+
         if (!ssl_cert_inst(&s->cert)) {
                 SSLerror(s, ERR_R_MALLOC_FAILURE);
                 return 0;
         }
 
-        if (ecdh == NULL) {
-                SSLerror(s, ERR_R_PASSED_NULL_PARAMETER);
+        if (ecdh == NULL)
                 return 0;
-        }
-
-        if (!EC_KEY_up_ref(ecdh)) {
-                SSLerror(s, ERR_R_ECDH_LIB);
+        if ((group = EC_KEY_get0_group(ecdh)) == NULL)
                 return 0;
-        }
-
-        if (!(s->internal->options & SSL_OP_SINGLE_ECDH_USE)) {
-                if (!EC_KEY_generate_key(ecdh)) {
-                        EC_KEY_free(ecdh);
-                        SSLerror(s, ERR_R_ECDH_LIB);
-                        return 0;
-                }
-        }
-
-        EC_KEY_free(s->cert->ecdh_tmp);
-        s->cert->ecdh_tmp = ecdh;
 
-        return 1;
+        nid = EC_GROUP_get_curve_name(group);
+        return SSL_set1_groups(s, &nid, 1);
 }
 
 static int
 _SSL_set_ecdh_auto(SSL *s, int state)
 {
-        s->cert->ecdh_tmp_auto = state;
         return 1;
 }
 
@@ -2095,7 +2082,6 @@ ssl3_callback_ctrl(SSL *s, int cmd, void (*fp)(void))
                 return 1;
 
         case SSL_CTRL_SET_TMP_ECDH_CB:
-                s->cert->ecdh_tmp_cb = (EC_KEY *(*)(SSL *, int, int))fp;
                 return 1;
 
         case SSL_CTRL_SET_TLSEXT_DEBUG_CB:
@@ -2133,35 +2119,21 @@ _SSL_CTX_set_dh_auto(SSL_CTX *ctx, int state)
 static int
 _SSL_CTX_set_tmp_ecdh(SSL_CTX *ctx, EC_KEY *ecdh)
 {
-        EC_KEY *ecdh_tmp;
+        const EC_GROUP *group;
+        int nid;
 
-        if (ecdh == NULL) {
-                SSLerrorx(ERR_R_ECDH_LIB);
+        if (ecdh == NULL)
                 return 0;
-        }
-
-        if ((ecdh_tmp = EC_KEY_dup(ecdh)) == NULL) {
-                SSLerrorx(ERR_R_EC_LIB);
+        if ((group = EC_KEY_get0_group(ecdh)) == NULL)
                 return 0;
-        }
-        if (!(ctx->internal->options & SSL_OP_SINGLE_ECDH_USE)) {
-                if (!EC_KEY_generate_key(ecdh_tmp)) {
-                        EC_KEY_free(ecdh_tmp);
-                        SSLerrorx(ERR_R_ECDH_LIB);
-                        return 0;
-                }
-        }
 
-        EC_KEY_free(ctx->internal->cert->ecdh_tmp);
-        ctx->internal->cert->ecdh_tmp = ecdh_tmp;
-
-        return 1;
+        nid = EC_GROUP_get_curve_name(group);
+        return SSL_CTX_set1_groups(ctx, &nid, 1);
 }
 
 static int
 _SSL_CTX_set_ecdh_auto(SSL_CTX *ctx, int state)
 {
-        ctx->internal->cert->ecdh_tmp_auto = state;
         return 1;
 }
 
@@ -2347,8 +2319,6 @@ ssl3_ctx_callback_ctrl(SSL_CTX *ctx, int cmd, void (*fp)(void))
                 return 1;
 
         case SSL_CTRL_SET_TMP_ECDH_CB:
-                ctx->internal->cert->ecdh_tmp_cb =
-                    (EC_KEY *(*)(SSL *, int, int))fp;
                 return 1;
 
         case SSL_CTRL_SET_TLSEXT_SERVERNAME_CB: