ECDH downgrade bug fix.
Fix bug where an OpenSSL client would accept a handshake using an
ephemeral ECDH ciphersuites with the server key exchange message omitted.
Thanks to Karthikeyan Bhargavan for reporting this issue.
CVE-2014-3572
Reviewed-by: Matt Caswell <matt@openssl.org>
diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 4ca2774..2313fbc 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -1376,6 +1376,8 @@
int encoded_pt_len = 0;
#endif
+ EVP_MD_CTX_init(&md_ctx);
+
/* use same message size as in ssl3_get_certificate_request()
* as ServerKeyExchange message may be skipped */
n=s->method->ssl_get_message(s,
@@ -1386,14 +1388,26 @@
&ok);
if (!ok) return((int)n);
+ alg_k=s->s3->tmp.new_cipher->algorithm_mkey;
+
if (s->s3->tmp.message_type != SSL3_MT_SERVER_KEY_EXCHANGE)
{
+ /*
+ * Can't skip server key exchange if this is an ephemeral
+ * ciphersuite.
+ */
+ if (alg_k & (SSL_kDHE|SSL_kECDHE))
+ {
+ SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_UNEXPECTED_MESSAGE);
+ al = SSL_AD_UNEXPECTED_MESSAGE;
+ goto f_err;
+ }
#ifndef OPENSSL_NO_PSK
/* In plain PSK ciphersuite, ServerKeyExchange can be
omitted if no identity hint is sent. Set
session->sess_cert anyway to avoid problems
later.*/
- if (s->s3->tmp.new_cipher->algorithm_mkey & SSL_kPSK)
+ if (alg_k & SSL_kPSK)
{
s->session->sess_cert=ssl_sess_cert_new();
if (s->ctx->psk_identity_hint)
@@ -1438,9 +1452,7 @@
/* Total length of the parameters including the length prefix */
param_len=0;
- alg_k=s->s3->tmp.new_cipher->algorithm_mkey;
alg_a=s->s3->tmp.new_cipher->algorithm_auth;
- EVP_MD_CTX_init(&md_ctx);
al=SSL_AD_DECODE_ERROR;
