add support for ECDH as well as custom ec+dh params in certificate

2 files changed, 71 insertions, 6 deletions

diff --git a/qmail-smtpd.c b/qmail-smtpd.c
index 817524d..fe33249 100644
--- a/qmail-smtpd.c
+++ b/qmail-smtpd.c
@@ -1148,15 +1148,14 @@ void smtp_tls(char *arg)
 static DH *make_dh_params(BIGNUM *(*prime)(BIGNUM *), const char *gen)
 {
     DH *dh = DH_new();
+    if (!dh)
+      return NULL;
 
-    if (!dh) {
-        return NULL;
-    }
     dh->p = prime(NULL);
     BN_dec2bn(&dh->g, gen);
     if (!dh->p || !dh->g) {
-        DH_free(dh);
-        return NULL;
+      DH_free(dh);
+      return NULL;
     }
     return dh;
 }
@@ -1182,7 +1181,7 @@ static struct dhparam {
  * contrast to the keys itself) and code safe as the returned structure
  * is duplicated by OpenSSL anyway. Hence no modification happens
  * to our copy. */
-DH *tmp_dh_cb(SSL *ssl, int export, int keylen)
+static DH *tmp_dh_cb(SSL *ssl, int export, int keylen)
 {
   EVP_PKEY *pkey = SSL_get_privatekey(ssl);
   int type = pkey ? EVP_PKEY_type(pkey->type) : EVP_PKEY_NONE;
@@ -1214,6 +1213,37 @@ DH *tmp_dh_cb(SSL *ssl, int export, int keylen)
   return NULL; /* impossible to reach. */
 }
 
+static DH *ssl_dh_GetParamFromFile(const char *file)
+{
+  DH *dh = NULL;
+  BIO *bio;
+
+  if ((bio = BIO_new_file(file, "r")) == NULL)
+    return NULL;
+  dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
+  BIO_free(bio);
+  return dh;
+}
+
+#ifdef HAVE_ECC
+static EC_GROUP *ssl_ec_GetParamFromFile(const char *file)
+{
+  EC_GROUP *group = NULL;
+  BIO *bio;
+
+  if ((bio = BIO_new_file(file, "r")) == NULL)
+    return NULL;
+  group = PEM_read_bio_ECPKParameters(bio, NULL, NULL, NULL);
+  BIO_free(bio);
+  return group;
+}
+
+static EC_KEY *tmp_ecdh_cb(SSL *ssl, int export, int keylen)
+{
+  return EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
+}
+#endif
+
 /* don't want to fail handshake if cert isn't verifiable */
 int verify_cb(int preverify_ok, X509_STORE_CTX *ctx) { return 1; }
 
@@ -1324,6 +1354,12 @@ void tls_init()
   X509_STORE *store;
   X509_LOOKUP *lookup;
   const char *servercert;
+  DH *dhparams;
+#ifdef HAVE_ECC
+  EC_GROUP *ecparams;
+  int nid;
+  EC_KEY *eckey = NULL;
+#endif
 
   /* if set, use servercert selected through SMTP_SERVERCERT env var */
   servercert = env_get("SMTP_SERVERCERT");
@@ -1376,6 +1412,30 @@ void tls_init()
   alloc_free(saciphers.s);
 
   SSL_set_tmp_dh_callback(myssl, tmp_dh_cb);
+
+  /* try to read DH parameters from certificate */
+  if ((dhparams = ssl_dh_GetParamFromFile(servercert)))
+    SSL_set_tmp_dh(myssl, dhparams);
+
+#ifdef HAVE_ECC
+  /* similarly, try to read the ECDH curve name from certificate... */
+  if ((ecparams = ssl_ec_GetParamFromFile(servercert)) &&
+      (nid = EC_GROUP_get_curve_name(ecparams)) &&
+      (eckey = EC_KEY_new_by_curve_name(nid))) {
+    SSL_set_tmp_ecdh(myssl, eckey);
+  }
+  else {
+#if defined(SSL_set_ecdh_auto)
+    /* ...otherwise, enable auto curve selection (OpenSSL 1.0.2 and later) */
+    SSL_set_ecdh_auto(myssl, 1);
+#else
+    /* or set callback, which will configure NIST P-256 */
+    SSL_set_tmp_ecdh_callback(myssl, tmp_ecdh_cb);
+#endif
+  }
+  EC_KEY_free(eckey);
+#endif
+
   SSL_set_rfd(myssl, ssl_rfd = substdio_fileno(&ssin));
   SSL_set_wfd(myssl, ssl_wfd = substdio_fileno(&ssout));
 
diff --git a/tls.h b/tls.h
index a4650af..808b115 100644
--- a/tls.h
+++ b/tls.h
@@ -3,6 +3,11 @@
 
 #include <openssl/ssl.h>
 
+/* ECC: make sure we have at least 1.0.0 */
+#if !defined(OPENSSL_NO_EC) && defined(TLSEXT_ECPOINTFORMAT_uncompressed)
+#define HAVE_ECC
+#endif
+
 extern int smtps;
 extern SSL *ssl;