Only allow ephemeral RSA keys in export ciphersuites.

OpenSSL clients would tolerate temporary RSA keys in non-export
ciphersuites. It also had an option SSL_OP_EPHEMERAL_RSA which
enabled this server side. Remove both options as they are a
protocol violation.

Thanks to Karthikeyan Bhargavan for reporting this issue.
(CVE-2015-0204)
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>

(cherry picked from commit 4b4c1fcc88aec8c9e001b0a0077d3cd4de1ed0e6)

Conflicts:
	CHANGES
	doc/ssl/SSL_CTX_set_options.pod
	ssl/d1_srvr.c
	ssl/s3_srvr.c

7 files changed, 30 insertions, 55 deletions

diff --git a/CHANGES b/CHANGES
index 75da406b62..ea460d6880 100644
--- a/CHANGES
+++ b/CHANGES
@@ -11,6 +11,14 @@
      (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]
+
   *) Fix various certificate fingerprint issues.
 
      By using non-DER or invalid encodings outside the signed portion of a
diff --git a/doc/ssl/SSL_CTX_set_options.pod b/doc/ssl/SSL_CTX_set_options.pod
index a2a570b610..307b157c5d 100644
--- a/doc/ssl/SSL_CTX_set_options.pod
+++ b/doc/ssl/SSL_CTX_set_options.pod
@@ -152,15 +152,7 @@ temporary/ephemeral DH parameters are used.
 
 =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 EDH (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
 
diff --git a/doc/ssl/SSL_CTX_set_tmp_rsa_callback.pod b/doc/ssl/SSL_CTX_set_tmp_rsa_callback.pod
index 534643cd9d..8794eb7ac3 100644
--- a/doc/ssl/SSL_CTX_set_tmp_rsa_callback.pod
+++ b/doc/ssl/SSL_CTX_set_tmp_rsa_callback.pod
@@ -74,21 +74,14 @@ exchange and use EDH (Ephemeral Diffie-Hellman) key exchange instead
 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
diff --git a/ssl/d1_srvr.c b/ssl/d1_srvr.c
index 0e6bf46c02..0e9bb204ad 100644
--- a/ssl/d1_srvr.c
+++ b/ssl/d1_srvr.c
@@ -371,23 +371,11 @@ int dtls1_accept(SSL *s)
 
 			/* clear this, it may get reset by
 			 * send_server_key_exchange */
-			if ((s->options & SSL_OP_EPHEMERAL_RSA)
-#ifndef OPENSSL_NO_KRB5
-				&& !(l & SSL_KRB5)
-#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;
+			s->s3->tmp.use_rsa_tmp=0;
 
 			/* only send if a DH key exchange, fortezza or
 			 * RSA but we have a sign only certificate */
-			if (s->s3->tmp.use_rsa_tmp
-			    || (l & (SSL_DH|SSL_kFZA))
+			if ((l & (SSL_DH|SSL_kFZA))
 			    || ((l & SSL_kRSA)
 				&& (s->cert->pkeys[SSL_PKEY_RSA_ENC].privatekey == NULL
 				    || (SSL_C_IS_EXPORT(s->s3->tmp.new_cipher)
diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 256fc94e26..2402a06163 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -1180,6 +1180,13 @@ int ssl3_get_key_exchange(SSL *s)
 #ifndef OPENSSL_NO_RSA
 	if (alg & 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);
diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c
index ca3e77aef6..18832e910b 100644
--- a/ssl/s3_srvr.c
+++ b/ssl/s3_srvr.c
@@ -355,18 +355,7 @@ int ssl3_accept(SSL *s)
 
 			/* clear this, it may get reset by
 			 * send_server_key_exchange */
-			if ((s->options & SSL_OP_EPHEMERAL_RSA)
-#ifndef OPENSSL_NO_KRB5
-				&& !(l & SSL_KRB5)
-#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;
+			s->s3->tmp.use_rsa_tmp=0;
 
 
 			/* only send if a DH key exchange, fortezza or
@@ -378,8 +367,7 @@ int ssl3_accept(SSL *s)
 			 * server certificate contains the server's 
 			 * public key for key exchange.
 			 */
-			if (s->s3->tmp.use_rsa_tmp
-			    || (l & SSL_kECDHE)
+			if ((l & SSL_kECDHE)
 			    || (l & (SSL_DH|SSL_kFZA))
 			    || ((l & SSL_kRSA)
 				&& (s->cert->pkeys[SSL_PKEY_RSA_ENC].privatekey == NULL
diff --git a/ssl/ssl.h b/ssl/ssl.h
index 4ea0d80124..8420100cf0 100644
--- a/ssl/ssl.h
+++ b/ssl/ssl.h
@@ -526,9 +526,8 @@ typedef struct ssl_session_st
 #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