Code: int ssl3_accept(SSL *s)
	{
	BUF_MEM *buf;
	unsigned long alg_k,Time=(unsigned long)time(NULL);
	void (*cb)(const SSL *ssl,int type,int val)=NULL;
	int ret= -1;
	int new_state,state,skip=0;

	RAND_add(&Time,sizeof(Time),0);
	ERR_clear_error();
	clear_sys_error();

	if (s->info_callback != NULL)
		cb=s->info_callback;
	else if (s->ctx->info_callback != NULL)
		cb=s->ctx->info_callback;

	/* init things to blank */
	s->in_handshake++;
	if (!SSL_in_init(s) || SSL_in_before(s)) SSL_clear(s);

	if (s->cert == NULL)
		{
		SSLerr(SSL_F_SSL3_ACCEPT,SSL_R_NO_CERTIFICATE_SET);
		return(-1);
		}

#ifndef OPENSSL_NO_HEARTBEATS
	/* If we're awaiting a HeartbeatResponse, pretend we
	 * already got and don't await it anymore, because
	 * Heartbeats don't make sense during handshakes anyway.
	 */
	if (s->tlsext_hb_pending)
		{
		s->tlsext_hb_pending = 0;
		s->tlsext_hb_seq++;
		}
#endif

	for (;;)
		{
		state=s->state;

		switch (s->state)
			{
		case SSL_ST_RENEGOTIATE:
			s->renegotiate=1;
			/* s->state=SSL_ST_ACCEPT; */

		case SSL_ST_BEFORE:
		case SSL_ST_ACCEPT:
		case SSL_ST_BEFORE|SSL_ST_ACCEPT:
		case SSL_ST_OK|SSL_ST_ACCEPT:

			s->server=1;
			if (cb != NULL) cb(s,SSL_CB_HANDSHAKE_START,1);

			if ((s->version>>8) != 3)
				{
				SSLerr(SSL_F_SSL3_ACCEPT, ERR_R_INTERNAL_ERROR);
				return -1;
				}

			if (!ssl_security(s, SSL_SECOP_VERSION, 0,
							s->version, NULL))
				{
				SSLerr(SSL_F_SSL3_ACCEPT, SSL_R_VERSION_TOO_LOW);
				return -1;
				}

			s->type=SSL_ST_ACCEPT;

			if (s->init_buf == NULL)
				{
				if ((buf=BUF_MEM_new()) == NULL)
					{
					ret= -1;
					goto end;
					}
				if (!BUF_MEM_grow(buf,SSL3_RT_MAX_PLAIN_LENGTH))
					{
					BUF_MEM_free(buf);
					ret= -1;
					goto end;
					}
				s->init_buf=buf;
				}

			if (!ssl3_setup_buffers(s))
				{
				ret= -1;
				goto end;
				}

			s->init_num=0;
			s->s3->flags &= ~TLS1_FLAGS_SKIP_CERT_VERIFY;
			s->s3->flags &= ~SSL3_FLAGS_CCS_OK;
			/* Should have been reset by ssl3_get_finished, too. */
			s->s3->change_cipher_spec = 0;

			if (s->state != SSL_ST_RENEGOTIATE)
				{
				/* Ok, we now need to push on a buffering BIO so that
				 * the output is sent in a way that TCP likes :-)
				 */
				if (!ssl_init_wbio_buffer(s,1)) { ret= -1; goto end; }
				
				ssl3_init_finished_mac(s);
				s->state=SSL3_ST_SR_CLNT_HELLO_A;
				s->ctx->stats.sess_accept++;
				}
			else if (!s->s3->send_connection_binding &&
				!(s->options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION))
				{
				/* Server attempting to renegotiate with
				 * client that doesn't support secure
				 * renegotiation.
				 */
				SSLerr(SSL_F_SSL3_ACCEPT, SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED);
				ssl3_send_alert(s,SSL3_AL_FATAL,SSL_AD_HANDSHAKE_FAILURE);
				ret = -1;
				goto end;
				}
			else
				{
				/* s->state == SSL_ST_RENEGOTIATE,
				 * we will just send a HelloRequest */
				s->ctx->stats.sess_accept_renegotiate++;
				s->state=SSL3_ST_SW_HELLO_REQ_A;
				}
			break;

		case SSL3_ST_SW_HELLO_REQ_A:
		case SSL3_ST_SW_HELLO_REQ_B:

			s->shutdown=0;
			ret=ssl3_send_hello_request(s);
			if (ret <= 0) goto end;
			s->s3->tmp.next_state=SSL3_ST_SW_HELLO_REQ_C;
			s->state=SSL3_ST_SW_FLUSH;
			s->init_num=0;

			ssl3_init_finished_mac(s);
			break;

		case SSL3_ST_SW_HELLO_REQ_C:
			s->state=SSL_ST_OK;
			break;

		case SSL3_ST_SR_CLNT_HELLO_A:
		case SSL3_ST_SR_CLNT_HELLO_B:
		case SSL3_ST_SR_CLNT_HELLO_C:

			ret=ssl3_get_client_hello(s);
			if (ret <= 0) goto end;
#ifndef OPENSSL_NO_SRP
			s->state = SSL3_ST_SR_CLNT_HELLO_D;
		case SSL3_ST_SR_CLNT_HELLO_D:
			{
			int al;
			if ((ret = ssl_check_srp_ext_ClientHello(s,&al))  < 0)
					{
					/* callback indicates firther work to be done */
					s->rwstate=SSL_X509_LOOKUP;
					goto end;
					}
			if (ret != SSL_ERROR_NONE)
				{
				ssl3_send_alert(s,SSL3_AL_FATAL,al);	
				/* This is not really an error but the only means to
                                   for a client to detect whether srp is supported. */
 				   if (al != TLS1_AD_UNKNOWN_PSK_IDENTITY) 	
					SSLerr(SSL_F_SSL3_ACCEPT,SSL_R_CLIENTHELLO_TLSEXT);			
				ret = SSL_TLSEXT_ERR_ALERT_FATAL;			
				ret= -1;
				goto end;	
				}
			}
#endif		
			
			s->renegotiate = 2;
			s->state=SSL3_ST_SW_SRVR_HELLO_A;
			s->init_num=0;
			break;

		case SSL3_ST_SW_SRVR_HELLO_A:
		case SSL3_ST_SW_SRVR_HELLO_B:
			ret=ssl3_send_server_hello(s);
			if (ret <= 0) goto end;
#ifndef OPENSSL_NO_TLSEXT
			if (s->hit)
				{
				if (s->tlsext_ticket_expected)
					s->state=SSL3_ST_SW_SESSION_TICKET_A;
				else
					s->state=SSL3_ST_SW_CHANGE_A;
				}
#else
			if (s->hit)
					s->state=SSL3_ST_SW_CHANGE_A;
#endif
			else
					s->state = SSL3_ST_SW_CERT_A;
			s->init_num = 0;
			break;

		case SSL3_ST_SW_CERT_A:
		case SSL3_ST_SW_CERT_B:
			/* Check if it is anon DH or anon ECDH, */
			/* normal PSK or KRB5 or SRP */
			if (!(s->s3->tmp.new_cipher->algorithm_auth & (SSL_aNULL|SSL_aKRB5|SSL_aSRP))
				&& !(s->s3->tmp.new_cipher->algorithm_mkey & SSL_kPSK))
				{
				ret=ssl3_send_server_certificate(s);
				if (ret <= 0) goto end;
#ifndef OPENSSL_NO_TLSEXT
				if (s->tlsext_status_expected)
					s->state=SSL3_ST_SW_CERT_STATUS_A;
				else
					s->state=SSL3_ST_SW_KEY_EXCH_A;
				}
			else
				{
				skip = 1;
				s->state=SSL3_ST_SW_KEY_EXCH_A;
				}
#else
				}
			else
				skip=1;

			s->state=SSL3_ST_SW_KEY_EXCH_A;
#endif
			s->init_num=0;
			break;

		case SSL3_ST_SW_KEY_EXCH_A:
 		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;
 
 
 			/* only send if a DH key exchange, fortezza or
			 * RSA but we have a sign only certificate
			 *
			 * PSK: may send PSK identity hints
			 *
			 * For ECC ciphersuites, we send a serverKeyExchange
			 * message only if the cipher suite is either
			 * ECDH-anon or ECDHE. In other cases, the
 			 * server certificate contains the server's
 			 * public key for key exchange.
 			 */
			if (s->s3->tmp.use_rsa_tmp
 			/* PSK: send ServerKeyExchange if PSK identity
 			 * hint if provided */
 #ifndef OPENSSL_NO_PSK
			    || ((alg_k & SSL_kPSK) && s->ctx->psk_identity_hint)
#endif
#ifndef OPENSSL_NO_SRP
			    /* SRP: send ServerKeyExchange */
			    || (alg_k & SSL_kSRP)
#endif
			    || (alg_k & SSL_kDHE)
			    || (alg_k & SSL_kECDHE)
			    || ((alg_k & SSL_kRSA)
				&& (s->cert->pkeys[SSL_PKEY_RSA_ENC].privatekey == NULL
				    || (SSL_C_IS_EXPORT(s->s3->tmp.new_cipher)
					&& EVP_PKEY_size(s->cert->pkeys[SSL_PKEY_RSA_ENC].privatekey)*8 > SSL_C_EXPORT_PKEYLENGTH(s->s3->tmp.new_cipher)
					)
				    )
				)
			    )
				{
				ret=ssl3_send_server_key_exchange(s);
				if (ret <= 0) goto end;
				}
			else
				skip=1;

			s->state=SSL3_ST_SW_CERT_REQ_A;
			s->init_num=0;
			break;

		case SSL3_ST_SW_CERT_REQ_A:
		case SSL3_ST_SW_CERT_REQ_B:
			if (/* don't request cert unless asked for it: */
				!(s->verify_mode & SSL_VERIFY_PEER) ||
				/* if SSL_VERIFY_CLIENT_ONCE is set,
				 * don't request cert during re-negotiation: */
				((s->session->peer != NULL) &&
				 (s->verify_mode & SSL_VERIFY_CLIENT_ONCE)) ||
				/* never request cert in anonymous ciphersuites
				 * (see section "Certificate request" in SSL 3 drafts
				 * and in RFC 2246): */
				((s->s3->tmp.new_cipher->algorithm_auth & SSL_aNULL) &&
				 /* ... except when the application insists on verification
				  * (against the specs, but s3_clnt.c accepts this for SSL 3) */
				 !(s->verify_mode & SSL_VERIFY_FAIL_IF_NO_PEER_CERT)) ||
				 /* never request cert in Kerberos ciphersuites */
				(s->s3->tmp.new_cipher->algorithm_auth & SSL_aKRB5) ||
				/* don't request certificate for SRP auth */
				(s->s3->tmp.new_cipher->algorithm_auth & SSL_aSRP)
				/* With normal PSK Certificates and
				 * Certificate Requests are omitted */
				|| (s->s3->tmp.new_cipher->algorithm_mkey & SSL_kPSK))
				{
				/* no cert request */
				skip=1;
				s->s3->tmp.cert_request=0;
				s->state=SSL3_ST_SW_SRVR_DONE_A;
				if (s->s3->handshake_buffer)
					if (!ssl3_digest_cached_records(s))
						return -1;
				}
			else
				{
				s->s3->tmp.cert_request=1;
				ret=ssl3_send_certificate_request(s);
				if (ret <= 0) goto end;
#ifndef NETSCAPE_HANG_BUG
				s->state=SSL3_ST_SW_SRVR_DONE_A;
#else
				s->state=SSL3_ST_SW_FLUSH;
				s->s3->tmp.next_state=SSL3_ST_SR_CERT_A;
#endif
				s->init_num=0;
				}
			break;

		case SSL3_ST_SW_SRVR_DONE_A:
		case SSL3_ST_SW_SRVR_DONE_B:
			ret=ssl3_send_server_done(s);
			if (ret <= 0) goto end;
			s->s3->tmp.next_state=SSL3_ST_SR_CERT_A;
			s->state=SSL3_ST_SW_FLUSH;
			s->init_num=0;
			break;
		
		case SSL3_ST_SW_FLUSH:

			/* This code originally checked to see if
			 * any data was pending using BIO_CTRL_INFO
			 * and then flushed. This caused problems
			 * as documented in PR#1939. The proposed
			 * fix doesn't completely resolve this issue
			 * as buggy implementations of BIO_CTRL_PENDING
			 * still exist. So instead we just flush
			 * unconditionally.
			 */

			s->rwstate=SSL_WRITING;
			if (BIO_flush(s->wbio) <= 0)
				{
				ret= -1;
				goto end;
				}
			s->rwstate=SSL_NOTHING;

			s->state=s->s3->tmp.next_state;
			break;

		case SSL3_ST_SR_CERT_A:
		case SSL3_ST_SR_CERT_B:
			if (s->s3->tmp.cert_request)
				{
				ret=ssl3_get_client_certificate(s);
				if (ret <= 0) goto end;
				}
			s->init_num=0;
			s->state=SSL3_ST_SR_KEY_EXCH_A;
			break;

		case SSL3_ST_SR_KEY_EXCH_A:
		case SSL3_ST_SR_KEY_EXCH_B:
			ret=ssl3_get_client_key_exchange(s);
			if (ret <= 0)
				goto end;
			if (ret == 2)
				{
				/* For the ECDH ciphersuites when
				 * the client sends its ECDH pub key in
				 * a certificate, the CertificateVerify
				 * message is not sent.
				 * Also for GOST ciphersuites when
				 * the client uses its key from the certificate
				 * for key exchange.
				 */
#if defined(OPENSSL_NO_TLSEXT) || defined(OPENSSL_NO_NEXTPROTONEG)
				s->state=SSL3_ST_SR_FINISHED_A;
#else
				if (s->s3->next_proto_neg_seen)
					s->state=SSL3_ST_SR_NEXT_PROTO_A;
				else
					s->state=SSL3_ST_SR_FINISHED_A;
#endif
				s->init_num = 0;
				}
			else if (SSL_USE_SIGALGS(s))
				{
				s->state=SSL3_ST_SR_CERT_VRFY_A;
				s->init_num=0;
				if (!s->session->peer)
					break;
				/* For sigalgs freeze the handshake buffer
				 * at this point and digest cached records.
				 */
				if (!s->s3->handshake_buffer)
					{
					SSLerr(SSL_F_SSL3_ACCEPT,ERR_R_INTERNAL_ERROR);
					return -1;
					}
				s->s3->flags |= TLS1_FLAGS_KEEP_HANDSHAKE;
				if (!ssl3_digest_cached_records(s))
					return -1;
				}
			else
				{
				int offset=0;
				int dgst_num;

				s->state=SSL3_ST_SR_CERT_VRFY_A;
				s->init_num=0;

				/* We need to get hashes here so if there is
				 * a client cert, it can be verified
				 * FIXME - digest processing for CertificateVerify
				 * should be generalized. But it is next step
				 */
				if (s->s3->handshake_buffer)
					if (!ssl3_digest_cached_records(s))
						return -1;
				for (dgst_num=0; dgst_num<SSL_MAX_DIGEST;dgst_num++)	
					if (s->s3->handshake_dgst[dgst_num]) 
						{
						int dgst_size;

						s->method->ssl3_enc->cert_verify_mac(s,EVP_MD_CTX_type(s->s3->handshake_dgst[dgst_num]),&(s->s3->tmp.cert_verify_md[offset]));
						dgst_size=EVP_MD_CTX_size(s->s3->handshake_dgst[dgst_num]);
						if (dgst_size < 0)
							{
							ret = -1;
							goto end;
							}
						offset+=dgst_size;
						}		
				}
			break;

		case SSL3_ST_SR_CERT_VRFY_A:
		case SSL3_ST_SR_CERT_VRFY_B:
			/*
			 * This *should* be the first time we enable CCS, but be
			 * extra careful about surrounding code changes. We need
			 * to set this here because we don't know if we're
			 * expecting a CertificateVerify or not.
			 */
			if (!s->s3->change_cipher_spec)
				s->s3->flags |= SSL3_FLAGS_CCS_OK;
			/* we should decide if we expected this one */
			ret=ssl3_get_cert_verify(s);
			if (ret <= 0) goto end;

#if defined(OPENSSL_NO_TLSEXT) || defined(OPENSSL_NO_NEXTPROTONEG)
			s->state=SSL3_ST_SR_FINISHED_A;
#else
			if (s->s3->next_proto_neg_seen)
				s->state=SSL3_ST_SR_NEXT_PROTO_A;
			else
				s->state=SSL3_ST_SR_FINISHED_A;
#endif
			s->init_num=0;
			break;

#if !defined(OPENSSL_NO_TLSEXT) && !defined(OPENSSL_NO_NEXTPROTONEG)
		case SSL3_ST_SR_NEXT_PROTO_A:
		case SSL3_ST_SR_NEXT_PROTO_B:
			/*
			 * Enable CCS for resumed handshakes with NPN.
			 * In a full handshake with NPN, we end up here through
			 * SSL3_ST_SR_CERT_VRFY_B, where SSL3_FLAGS_CCS_OK was
			 * already set. Receiving a CCS clears the flag, so make
			 * sure not to re-enable it to ban duplicates.
			 * s->s3->change_cipher_spec is set when a CCS is
			 * processed in s3_pkt.c, and remains set until
			 * the client's Finished message is read.
			 */
			if (!s->s3->change_cipher_spec)
				s->s3->flags |= SSL3_FLAGS_CCS_OK;

			ret=ssl3_get_next_proto(s);
			if (ret <= 0) goto end;
			s->init_num = 0;
			s->state=SSL3_ST_SR_FINISHED_A;
			break;
#endif

		case SSL3_ST_SR_FINISHED_A:
		case SSL3_ST_SR_FINISHED_B:
			/*
			 * Enable CCS for resumed handshakes without NPN.
			 * In a full handshake, we end up here through
			 * SSL3_ST_SR_CERT_VRFY_B, where SSL3_FLAGS_CCS_OK was
			 * already set. Receiving a CCS clears the flag, so make
			 * sure not to re-enable it to ban duplicates.
			 * s->s3->change_cipher_spec is set when a CCS is
			 * processed in s3_pkt.c, and remains set until
			 * the client's Finished message is read.
			 */
			if (!s->s3->change_cipher_spec)
				s->s3->flags |= SSL3_FLAGS_CCS_OK;
			ret=ssl3_get_finished(s,SSL3_ST_SR_FINISHED_A,
				SSL3_ST_SR_FINISHED_B);
			if (ret <= 0) goto end;
			if (s->hit)
				s->state=SSL_ST_OK;
#ifndef OPENSSL_NO_TLSEXT
			else if (s->tlsext_ticket_expected)
				s->state=SSL3_ST_SW_SESSION_TICKET_A;
#endif
			else
				s->state=SSL3_ST_SW_CHANGE_A;
			s->init_num=0;
			break;

#ifndef OPENSSL_NO_TLSEXT
		case SSL3_ST_SW_SESSION_TICKET_A:
		case SSL3_ST_SW_SESSION_TICKET_B:
			ret=ssl3_send_newsession_ticket(s);
			if (ret <= 0) goto end;
			s->state=SSL3_ST_SW_CHANGE_A;
			s->init_num=0;
			break;

		case SSL3_ST_SW_CERT_STATUS_A:
		case SSL3_ST_SW_CERT_STATUS_B:
			ret=ssl3_send_cert_status(s);
			if (ret <= 0) goto end;
			s->state=SSL3_ST_SW_KEY_EXCH_A;
			s->init_num=0;
			break;

#endif

		case SSL3_ST_SW_CHANGE_A:
		case SSL3_ST_SW_CHANGE_B:

			s->session->cipher=s->s3->tmp.new_cipher;
			if (!s->method->ssl3_enc->setup_key_block(s))
				{ ret= -1; goto end; }

			ret=ssl3_send_change_cipher_spec(s,
				SSL3_ST_SW_CHANGE_A,SSL3_ST_SW_CHANGE_B);

			if (ret <= 0) goto end;
			s->state=SSL3_ST_SW_FINISHED_A;
			s->init_num=0;

			if (!s->method->ssl3_enc->change_cipher_state(s,
				SSL3_CHANGE_CIPHER_SERVER_WRITE))
				{
				ret= -1;
				goto end;
				}

			break;

		case SSL3_ST_SW_FINISHED_A:
		case SSL3_ST_SW_FINISHED_B:
			ret=ssl3_send_finished(s,
				SSL3_ST_SW_FINISHED_A,SSL3_ST_SW_FINISHED_B,
				s->method->ssl3_enc->server_finished_label,
				s->method->ssl3_enc->server_finished_label_len);
			if (ret <= 0) goto end;
			s->state=SSL3_ST_SW_FLUSH;
			if (s->hit)
				{
#if defined(OPENSSL_NO_TLSEXT) || defined(OPENSSL_NO_NEXTPROTONEG)
				s->s3->tmp.next_state=SSL3_ST_SR_FINISHED_A;
#else
				if (s->s3->next_proto_neg_seen)
					{
					s->s3->tmp.next_state=SSL3_ST_SR_NEXT_PROTO_A;
					}
				else
					s->s3->tmp.next_state=SSL3_ST_SR_FINISHED_A;
#endif
				}
			else
				s->s3->tmp.next_state=SSL_ST_OK;
			s->init_num=0;
			break;

		case SSL_ST_OK:
			/* clean a few things up */
			ssl3_cleanup_key_block(s);

			BUF_MEM_free(s->init_buf);
			s->init_buf=NULL;

			/* remove buffering on output */
			ssl_free_wbio_buffer(s);

			s->init_num=0;

			if (s->renegotiate == 2) /* skipped if we just sent a HelloRequest */
				{
				s->renegotiate=0;
				s->new_session=0;
				
				ssl_update_cache(s,SSL_SESS_CACHE_SERVER);
				
				s->ctx->stats.sess_accept_good++;
				/* s->server=1; */
				s->handshake_func=ssl3_accept;

				if (cb != NULL) cb(s,SSL_CB_HANDSHAKE_DONE,1);
				}
			
			ret = 1;
			goto end;
			/* break; */

		default:
			SSLerr(SSL_F_SSL3_ACCEPT,SSL_R_UNKNOWN_STATE);
			ret= -1;
			goto end;
			/* break; */
			}
		
		if (!s->s3->tmp.reuse_message && !skip)
			{
			if (s->debug)
				{
				if ((ret=BIO_flush(s->wbio)) <= 0)
					goto end;
				}


			if ((cb != NULL) && (s->state != state))
				{
				new_state=s->state;
				s->state=state;
				cb(s,SSL_CB_ACCEPT_LOOP,1);
				s->state=new_state;
				}
			}
		skip=0;
		}

Vulnerability Type: 
CWE ID: CWE-310
Summary: The ssl3_get_key_exchange function in s3_clnt.c in OpenSSL before 0.9.8zd, 1.0.0 before 1.0.0p, and 1.0.1 before 1.0.1k allows remote SSL servers to conduct RSA-to-EXPORT_RSA downgrade attacks and facilitate brute-force decryption by offering a weak ephemeral RSA key in a noncompliant role, related to the *FREAK* issue.  NOTE: the scope of this CVE is only client code based on OpenSSL, not EXPORT_RSA issues associated with servers or other TLS implementations.
Commit Message: 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>