/* If dhparam is set, expand it, and load up the parameters for DH encryption.
Arguments:
- dhparam DH parameter file
+ dhparam DH parameter file or fixed parameter identity string
host connected host, if client; NULL if server
Returns: TRUE if OK (nothing to set up, or setup worked)
*/
static BOOL
-init_dh(uschar *dhparam, host_item *host)
+init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
{
-BOOL yield = TRUE;
BIO *bio;
DH *dh;
uschar *dhexpanded;
+const char *pem;
if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
return FALSE;
-if (dhexpanded == NULL) return TRUE;
-
-if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL)
+if (dhexpanded == NULL || *dhexpanded == '\0')
{
- tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
- host, (uschar *)strerror(errno));
- yield = FALSE;
+ bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
}
-else
+else if (dhexpanded[0] == '/')
{
- if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL)
+ bio = BIO_new_file(CS dhexpanded, "r");
+ if (bio == NULL)
{
tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
- host, NULL);
- yield = FALSE;
+ host, US strerror(errno));
+ return FALSE;
}
- else
+ }
+else
+ {
+ if (Ustrcmp(dhexpanded, "none") == 0)
{
- if ((8*DH_size(dh)) > tls_dh_max_bits)
- {
- DEBUG(D_tls)
- debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
- 8*DH_size(dh), tls_dh_max_bits);
- }
- else
- {
- SSL_CTX_set_tmp_dh(ctx, dh);
- DEBUG(D_tls)
- debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n",
- dhexpanded, 8*DH_size(dh));
- }
- DH_free(dh);
+ DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
+ return TRUE;
+ }
+
+ pem = std_dh_prime_named(dhexpanded);
+ if (!pem)
+ {
+ tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
+ host, US strerror(errno));
+ return FALSE;
}
+ bio = BIO_new_mem_buf(CS pem, -1);
+ }
+
+dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
+if (dh == NULL)
+ {
BIO_free(bio);
+ tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
+ host, NULL);
+ return FALSE;
+ }
+
+/* Even if it is larger, we silently return success rather than cause things
+ * to fail out, so that a too-large DH will not knock out all TLS; it's a
+ * debatable choice. */
+if ((8*DH_size(dh)) > tls_dh_max_bits)
+ {
+ DEBUG(D_tls)
+ debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
+ 8*DH_size(dh), tls_dh_max_bits);
+ }
+else
+ {
+ SSL_CTX_set_tmp_dh(sctx, dh);
+ DEBUG(D_tls)
+ debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
+ dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
}
-return yield;
+DH_free(dh);
+BIO_free(bio);
+
+return TRUE;
}
rc = tls_expand_session_files(ctx_sni, cbinfo);
if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
+rc = init_dh(ctx_sni, cbinfo->dhparam, NULL);
+if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
+
DEBUG(D_tls) debug_printf("Switching SSL context.\n");
SSL_set_SSL_CTX(s, ctx_sni);
EVP_add_digest(EVP_sha256());
#endif
-/* Create a context */
+/* Create a context.
+The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant
+negotiation in the different methods; as far as I can tell, the only
+*_{server,client}_method which allows negotiation is SSLv23, which exists even
+when OpenSSL is built without SSLv2 support.
+By disabling with openssl_options, we can let admins re-enable with the
+existing knob. */
ctx = SSL_CTX_new((host == NULL)?
SSLv23_server_method() : SSLv23_client_method());
/* Initialize with DH parameters if supplied */
-if (!init_dh(dhparam, host)) return DEFER;
+if (!init_dh(ctx, dhparam, host)) return DEFER;
/* Set up certificate and key (and perhaps OCSP info) */
result = 0L;
/* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed
* from default because it increases BEAST susceptibility. */
+#ifdef SSL_OP_NO_SSLv2
+result |= SSL_OP_NO_SSLv2;
+#endif
if (option_spec == NULL)
{