Add checks to the return value of EVP_Cipher to prevent silent encryption failure.

PR#1767

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit fe78f08d15)

ssl/s3_pkt.c

@@ -1040,8 +1040,7 @@ static int do_ssl3_write(SSL *s, int type, const unsigned char *buf,
 		wr->length += eivlen;
 		}
 
-	/* ssl3_enc can only have an error on read */
-	s->method->ssl3_enc->enc(s,1);
+	if(s->method->ssl3_enc->enc(s,1)<1) goto err;
 
 	/* record length after mac and block padding */
 	s2n(wr->length,plen);