summaryrefslogtreecommitdiff
path: root/src/openvpn/ssl_ncp.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/openvpn/ssl_ncp.c')
-rw-r--r--src/openvpn/ssl_ncp.c330
1 files changed, 330 insertions, 0 deletions
diff --git a/src/openvpn/ssl_ncp.c b/src/openvpn/ssl_ncp.c
new file mode 100644
index 0000000..f522b8f
--- /dev/null
+++ b/src/openvpn/ssl_ncp.c
@@ -0,0 +1,330 @@
+/*
+ * OpenVPN -- An application to securely tunnel IP networks
+ * over a single TCP/UDP port, with support for SSL/TLS-based
+ * session authentication and key exchange,
+ * packet encryption, packet authentication, and
+ * packet compression.
+ *
+ * Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
+ * Copyright (C) 2010-2018 Fox Crypto B.V. <openvpn@fox-it.com>
+ * Copyright (C) 2008-2013 David Sommerseth <dazo@users.sourceforge.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/**
+ * @file Control Channel SSL/Data dynamic negotion Module
+ * This file is split from ssl.c to be able to unit test it.
+ */
+
+/*
+ * The routines in this file deal with dynamically negotiating
+ * the data channel HMAC and cipher keys through a TLS session.
+ *
+ * Both the TLS session and the data channel are multiplexed
+ * over the same TCP/UDP port.
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#elif defined(_MSC_VER)
+#include "config-msvc.h"
+#endif
+
+#include "syshead.h"
+#include "win32.h"
+
+#include "error.h"
+#include "common.h"
+
+#include "ssl_ncp.h"
+#include "openvpn.h"
+
+/**
+ * Return the Negotiable Crypto Parameters version advertised in the peer info
+ * string, or 0 if none specified.
+ */
+static int
+tls_peer_info_ncp_ver(const char *peer_info)
+{
+ const char *ncpstr = peer_info ? strstr(peer_info, "IV_NCP=") : NULL;
+ if (ncpstr)
+ {
+ int ncp = 0;
+ int r = sscanf(ncpstr, "IV_NCP=%d", &ncp);
+ if (r == 1)
+ {
+ return ncp;
+ }
+ }
+ return 0;
+}
+
+/**
+ * Returns whether the client supports NCP either by
+ * announcing IV_NCP>=2 or the IV_CIPHERS list
+ */
+bool
+tls_peer_supports_ncp(const char *peer_info)
+{
+ if (!peer_info)
+ {
+ return false;
+ }
+ else if (tls_peer_info_ncp_ver(peer_info) >= 2
+ || strstr(peer_info, "IV_CIPHERS="))
+ {
+ return true;
+ }
+ else
+ {
+ return false;
+ }
+}
+
+char *
+mutate_ncp_cipher_list(const char *list, struct gc_arena *gc)
+{
+ bool error_found = false;
+
+ struct buffer new_list = alloc_buf(MAX_NCP_CIPHERS_LENGTH);
+
+ char *const tmp_ciphers = string_alloc(list, NULL);
+ const char *token = strtok(tmp_ciphers, ":");
+ while (token)
+ {
+ /*
+ * Going through a roundtrip by using cipher_kt_get/cipher_kt_name
+ * (and translate_cipher_name_from_openvpn/
+ * translate_cipher_name_to_openvpn) also normalises the cipher name,
+ * e.g. replacing AeS-128-gCm with AES-128-GCM
+ */
+ const cipher_kt_t *ktc = cipher_kt_get(token);
+ if (!ktc)
+ {
+ msg(M_WARN, "Unsupported cipher in --data-ciphers: %s", token);
+ error_found = true;
+ }
+ else
+ {
+ const char *ovpn_cipher_name = cipher_kt_name(ktc);
+
+ if (buf_len(&new_list)> 0)
+ {
+ /* The next if condition ensure there is always space for
+ * a :
+ */
+ buf_puts(&new_list, ":");
+ }
+
+ /* Ensure buffer has capacity for cipher name + : + \0 */
+ if (!(buf_forward_capacity(&new_list) >
+ strlen(ovpn_cipher_name) + 2))
+ {
+ msg(M_WARN, "Length of --data-ciphers is over the "
+ "limit of 127 chars");
+ error_found = true;
+ }
+ else
+ {
+ buf_puts(&new_list, ovpn_cipher_name);
+ }
+ }
+ token = strtok(NULL, ":");
+ }
+
+
+
+ char *ret = NULL;
+ if (!error_found && buf_len(&new_list) > 0)
+ {
+ buf_null_terminate(&new_list);
+ ret = string_alloc(buf_str(&new_list), gc);
+ }
+ free(tmp_ciphers);
+ free_buf(&new_list);
+
+ return ret;
+}
+
+bool
+tls_item_in_cipher_list(const char *item, const char *list)
+{
+ char *tmp_ciphers = string_alloc(list, NULL);
+ char *tmp_ciphers_orig = tmp_ciphers;
+
+ const char *token = strtok(tmp_ciphers, ":");
+ while (token)
+ {
+ if (0 == strcmp(token, item))
+ {
+ break;
+ }
+ token = strtok(NULL, ":");
+ }
+ free(tmp_ciphers_orig);
+
+ return token != NULL;
+}
+
+const char *
+tls_peer_ncp_list(const char *peer_info, struct gc_arena *gc)
+{
+ /* Check if the peer sends the IV_CIPHERS list */
+ const char *ncp_ciphers_start;
+ if (peer_info && (ncp_ciphers_start = strstr(peer_info, "IV_CIPHERS=")))
+ {
+ ncp_ciphers_start += strlen("IV_CIPHERS=");
+ const char *ncp_ciphers_end = strstr(ncp_ciphers_start, "\n");
+ if (!ncp_ciphers_end)
+ {
+ /* IV_CIPHERS is at end of the peer_info list and no '\n'
+ * follows */
+ ncp_ciphers_end = ncp_ciphers_start + strlen(ncp_ciphers_start);
+ }
+
+ char *ncp_ciphers_peer = string_alloc(ncp_ciphers_start, gc);
+ /* NULL terminate the copy at the right position */
+ ncp_ciphers_peer[ncp_ciphers_end - ncp_ciphers_start] = '\0';
+ return ncp_ciphers_peer;
+
+ }
+ else if (tls_peer_info_ncp_ver(peer_info)>=2)
+ {
+ /* If the peer announces IV_NCP=2 then it supports the AES GCM
+ * ciphers */
+ return "AES-256-GCM:AES-128-GCM";
+ }
+ else
+ {
+ return "";
+ }
+}
+
+char *
+ncp_get_best_cipher(const char *server_list, const char *peer_info,
+ const char *remote_cipher, struct gc_arena *gc)
+{
+ /*
+ * The gc of the parameter is tied to the VPN session, create a
+ * short lived gc arena that is only valid for the duration of
+ * this function
+ */
+
+ struct gc_arena gc_tmp = gc_new();
+
+ const char *peer_ncp_list = tls_peer_ncp_list(peer_info, &gc_tmp);
+
+ /* non-NCP client without OCC? "assume nothing" */
+ /* For client doing the newer version of NCP (that send IV_CIPHER)
+ * we cannot assume that they will accept remote_cipher */
+ if (remote_cipher == NULL ||
+ (peer_info && strstr(peer_info, "IV_CIPHERS=")))
+ {
+ remote_cipher = "";
+ }
+
+ char *tmp_ciphers = string_alloc(server_list, &gc_tmp);
+
+ const char *token;
+ while ((token = strsep(&tmp_ciphers, ":")))
+ {
+ if (tls_item_in_cipher_list(token, peer_ncp_list)
+ || streq(token, remote_cipher))
+ {
+ break;
+ }
+ }
+
+ char *ret = NULL;
+ if (token != NULL)
+ {
+ ret = string_alloc(token, gc);
+ }
+
+ gc_free(&gc_tmp);
+ return ret;
+}
+
+/**
+ * "Poor man's NCP": Use peer cipher if it is an allowed (NCP) cipher.
+ * Allows non-NCP peers to upgrade their cipher individually.
+ *
+ * Returns true if we switched to the peer's cipher
+ *
+ * Make sure to call tls_session_update_crypto_params() after calling this
+ * function.
+ */
+static bool
+tls_poor_mans_ncp(struct options *o, const char *remote_ciphername)
+{
+ if (remote_ciphername
+ && 0 != strcmp(o->ciphername, remote_ciphername))
+ {
+ if (tls_item_in_cipher_list(remote_ciphername, o->ncp_ciphers))
+ {
+ o->ciphername = string_alloc(remote_ciphername, &o->gc);
+ msg(D_TLS_DEBUG_LOW, "Using peer cipher '%s'", o->ciphername);
+ return true;
+ }
+ }
+ return false;
+}
+
+bool
+check_pull_client_ncp(struct context *c, const int found)
+{
+ if (found & OPT_P_NCP)
+ {
+ msg(D_PUSH, "OPTIONS IMPORT: data channel crypto options modified");
+ return true;
+ }
+
+ if (!c->options.ncp_enabled)
+ {
+ return true;
+ }
+ /* If the server did not push a --cipher, we will switch to the
+ * remote cipher if it is in our ncp-ciphers list */
+ bool useremotecipher = tls_poor_mans_ncp(&c->options,
+ c->c2.tls_multi->remote_ciphername);
+
+
+ /* We could not figure out the peer's cipher but we have fallback
+ * enabled */
+ if (!useremotecipher && c->options.enable_ncp_fallback)
+ {
+ return true;
+ }
+
+ /* We failed negotiation, give appropiate error message */
+ if (c->c2.tls_multi->remote_ciphername)
+ {
+ msg(D_TLS_ERRORS, "OPTIONS ERROR: failed to negotiate "
+ "cipher with server. Add the server's "
+ "cipher ('%s') to --data-ciphers (currently '%s') if "
+ "you want to connect to this server.",
+ c->c2.tls_multi->remote_ciphername,
+ c->options.ncp_ciphers);
+ return false;
+
+ }
+ else
+ {
+ msg(D_TLS_ERRORS, "OPTIONS ERROR: failed to negotiate "
+ "cipher with server. Configure "
+ "--data-ciphers-fallback if you want to connect "
+ "to this server.");
+ return false;
+ }
+} \ No newline at end of file