(CVE-2014-3572)
[Steve Henson]
+ *) Remove non-export ephemeral RSA code on client and server. This code
+ violated the TLS standard by allowing the use of temporary RSA keys in
+ non-export ciphersuites and could be used by a server to effectively
+ downgrade the RSA key length used to a value smaller than the server
+ certificate. Thanks for Karthikeyan Bhargavan for reporting this issue.
+ (CVE-2015-0204)
+ [Steve Henson]
+
*) Ensure that the session ID context of an SSL is updated when its
SSL_CTX is updated via SSL_set_SSL_CTX.
=item SSL_OP_EPHEMERAL_RSA
-Always use ephemeral (temporary) RSA key when doing RSA operations
-(see L<SSL_CTX_set_tmp_rsa_callback(3)|SSL_CTX_set_tmp_rsa_callback(3)>).
-According to the specifications this is only done, when a RSA key
-can only be used for signature operations (namely under export ciphers
-with restricted RSA keylength). By setting this option, ephemeral
-RSA keys are always used. This option breaks compatibility with the
-SSL/TLS specifications and may lead to interoperability problems with
-clients and should therefore never be used. Ciphers with DHE (ephemeral
-Diffie-Hellman) key exchange should be used instead.
+This option is no longer implemented and is treated as no op.
=item SSL_OP_CIPHER_SERVER_PREFERENCE
in order to achieve forward secrecy (see
L<SSL_CTX_set_tmp_dh_callback(3)|SSL_CTX_set_tmp_dh_callback(3)>).
-On OpenSSL servers ephemeral RSA key exchange is therefore disabled by default
-and must be explicitly enabled using the SSL_OP_EPHEMERAL_RSA option of
-L<SSL_CTX_set_options(3)|SSL_CTX_set_options(3)>, violating the TLS/SSL
-standard. When ephemeral RSA key exchange is required for export ciphers,
-it will automatically be used without this option!
-
-An application may either directly specify the key or can supply the key via
-a callback function. The callback approach has the advantage, that the
-callback may generate the key only in case it is actually needed. As the
-generation of a RSA key is however costly, it will lead to a significant
-delay in the handshake procedure. Another advantage of the callback function
-is that it can supply keys of different size (e.g. for SSL_OP_EPHEMERAL_RSA
-usage) while the explicit setting of the key is only useful for key size of
-512 bits to satisfy the export restricted ciphers and does give away key length
-if a longer key would be allowed.
+An application may either directly specify the key or can supply the key via a
+callback function. The callback approach has the advantage, that the callback
+may generate the key only in case it is actually needed. As the generation of a
+RSA key is however costly, it will lead to a significant delay in the handshake
+procedure. Another advantage of the callback function is that it can supply
+keys of different size while the explicit setting of the key is only useful for
+key size of 512 bits to satisfy the export restricted ciphers and does give
+away key length if a longer key would be allowed.
The B<tmp_rsa_callback> is called with the B<keylength> needed and
the B<is_export> information. The B<is_export> flag is set, when the
case SSL3_ST_SW_KEY_EXCH_B:
alg_k = s->s3->tmp.new_cipher->algorithm_mkey;
- /* clear this, it may get reset by
- * send_server_key_exchange */
- if ((s->options & SSL_OP_EPHEMERAL_RSA)
-#ifndef OPENSSL_NO_KRB5
- && !(alg_k & SSL_kKRB5)
-#endif /* OPENSSL_NO_KRB5 */
- )
- /* option SSL_OP_EPHEMERAL_RSA sends temporary RSA key
- * even when forbidden by protocol specs
- * (handshake may fail as clients are not required to
- * be able to handle this) */
- s->s3->tmp.use_rsa_tmp=1;
- else
- s->s3->tmp.use_rsa_tmp=0;
+ /*
+ * clear this, it may get reset by
+ * send_server_key_exchange
+ */
+ s->s3->tmp.use_rsa_tmp=0;
/* only send if a DH key exchange or
* RSA but we have a sign only certificate */
- if (s->s3->tmp.use_rsa_tmp
+ if (0
/* PSK: send ServerKeyExchange if PSK identity
* hint if provided */
#ifndef OPENSSL_NO_PSK
#ifndef OPENSSL_NO_RSA
if (alg_k & SSL_kRSA)
{
+ /* Temporary RSA keys only allowed in export ciphersuites */
+ if (!SSL_C_IS_EXPORT(s->s3->tmp.new_cipher))
+ {
+ al=SSL_AD_UNEXPECTED_MESSAGE;
+ SSLerr(SSL_F_SSL3_GET_SERVER_CERTIFICATE,SSL_R_UNEXPECTED_MESSAGE);
+ goto f_err;
+ }
if ((rsa=RSA_new()) == NULL)
{
SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_MALLOC_FAILURE);
case SSL3_ST_SW_KEY_EXCH_B:
alg_k = s->s3->tmp.new_cipher->algorithm_mkey;
- /* clear this, it may get reset by
- * send_server_key_exchange */
- if ((s->options & SSL_OP_EPHEMERAL_RSA)
-#ifndef OPENSSL_NO_KRB5
- && !(alg_k & SSL_kKRB5)
-#endif /* OPENSSL_NO_KRB5 */
- )
- /* option SSL_OP_EPHEMERAL_RSA sends temporary RSA key
- * even when forbidden by protocol specs
- * (handshake may fail as clients are not required to
- * be able to handle this) */
- s->s3->tmp.use_rsa_tmp=1;
- else
- s->s3->tmp.use_rsa_tmp=0;
+ /*
+ * clear this, it may get reset by
+ * send_server_key_exchange
+ */
+ s->s3->tmp.use_rsa_tmp=0;
/* only send if a DH key exchange, fortezza or
* server certificate contains the server's
* public key for key exchange.
*/
- if (s->s3->tmp.use_rsa_tmp
+ if (0
/* PSK: send ServerKeyExchange if PSK identity
* hint if provided */
#ifndef OPENSSL_NO_PSK
#define SSL_OP_SINGLE_ECDH_USE 0x00080000L
/* If set, always create a new key when using tmp_dh parameters */
#define SSL_OP_SINGLE_DH_USE 0x00100000L
-/* Set to always use the tmp_rsa key when doing RSA operations,
- * even when this violates protocol specs */
-#define SSL_OP_EPHEMERAL_RSA 0x00200000L
+/* Does nothing: retained for compatibiity */
+#define SSL_OP_EPHEMERAL_RSA 0x0
/* Set on servers to choose the cipher according to the server's
* preferences */
#define SSL_OP_CIPHER_SERVER_PREFERENCE 0x00400000L
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