@@ -94,6 +94,128 @@ init_key_dco_bi(struct tls_multi *multi, struct key_state *ks,
ciphername);
}
+/**
+ * Find a usable key that is not the primary (i.e. the secondary key)
+ *
+ * @param multi The TLS struct to retrieve keys from
+ * @param primary The primary key that should be skipped during the scan
+ *
+ * @return The secondary key or NULL if none could be found
+ */
+static struct key_state *
+dco_get_secondary_key(struct tls_multi *multi, const struct key_state *primary)
+{
+ for (int i = 0; i < KEY_SCAN_SIZE; ++i)
+ {
+ struct key_state *ks = get_key_scan(multi, i);
+ struct key_ctx_bi *key = &ks->crypto_options.key_ctx_bi;
+
+ if (ks == primary)
+ {
+ continue;
+ }
+
+ if (ks->state >= S_GENERATED_KEYS && ks->authenticated == KS_AUTH_TRUE)
+ {
+ ASSERT(key->initialized);
+ return ks;
+ }
+ }
+
+ return NULL;
+}
+
+void
+dco_update_keys(dco_context_t *dco, struct tls_multi *multi)
+{
+ msg(D_DCO_DEBUG, "%s: peer_id=%d", __func__, multi->peer_id);
+
+ /* this function checks if keys have to be swapped or erased, therefore it
+ * can't do much if we don't have any key installed
+ */
+ if (multi->dco_keys_installed == 0)
+ {
+ return;
+ }
+
+ struct key_state *primary = tls_select_encryption_key(multi);
+ /* no primary key available -> no usable key exists, therefore we should
+ * tell DCO to simply wipe all keys
+ */
+ if (!primary)
+ {
+ msg(D_DCO, "No encryption key found. Purging data channel keys");
+
+ int ret = dco_del_key(dco, multi->peer_id, OVPN_KEY_SLOT_PRIMARY);
+ if (ret < 0)
+ {
+ msg(D_DCO, "Cannot delete primary key during wipe: %s (%d)", strerror(-ret), ret);
+ return;
+ }
+
+ ret = dco_del_key(dco, multi->peer_id, OVPN_KEY_SLOT_SECONDARY);
+ if (ret < 0)
+ {
+ msg(D_DCO, "Cannot delete secondary key during wipe: %s (%d)", strerror(-ret), ret);
+ return;
+ }
+
+ multi->dco_keys_installed = 0;
+ return;
+ }
+
+ /* if we have a primary key, it must have been installed already (keys
+ * are installed upon generation in the TLS code)
+ */
+ ASSERT(primary->dco_status != DCO_NOT_INSTALLED);
+
+ struct key_state *secondary = dco_get_secondary_key(multi, primary);
+ /* the current primary key was installed as secondary in DCO, this means
+ * we have promoted it and we should tell DCO to swap keys
+ */
+ if (primary->dco_status == DCO_INSTALLED_SECONDARY)
+ {
+ msg(D_DCO_DEBUG, "Swapping primary and secondary keys, now: id1=%d id2=%d",
+ primary->key_id, secondary ? secondary->key_id : -1);
+
+ int ret = dco_swap_keys(dco, multi->peer_id);
+ if (ret < 0)
+ {
+ msg(D_DCO, "Cannot swap keys: %s (%d)", strerror(-ret), ret);
+ return;
+ }
+
+ primary->dco_status = DCO_INSTALLED_PRIMARY;
+ if (secondary)
+ {
+ ASSERT(secondary->dco_status == DCO_INSTALLED_PRIMARY);
+ secondary->dco_status = DCO_INSTALLED_SECONDARY;
+ }
+ }
+
+ /* if we have no secondary key anymore, inform DCO about it */
+ if (!secondary && multi->dco_keys_installed == 2)
+ {
+ int ret = dco_del_key(dco, multi->peer_id, OVPN_KEY_SLOT_SECONDARY);
+ if (ret < 0)
+ {
+ msg(D_DCO, "Cannot delete secondary key: %s (%d)", strerror(-ret), ret);
+ return;
+ }
+ multi->dco_keys_installed = 1;
+ }
+
+ /* all keys that are not installed are set to NOT installed */
+ for (int i = 0; i < KEY_SCAN_SIZE; ++i)
+ {
+ struct key_state *ks = get_key_scan(multi, i);
+ if (ks != primary && ks != secondary)
+ {
+ ks->dco_status = DCO_NOT_INSTALLED;
+ }
+ }
+}
+
static bool
dco_check_option_conflict_platform(int msglevel, const struct options *o)
{
@@ -132,6 +132,14 @@ int init_key_dco_bi(struct tls_multi *multi, struct key_state *ks,
const struct key2 *key2, int key_direction,
const char *ciphername, bool server);
+/**
+ * Possibly swap or wipe keys from DCO
+ *
+ * @param dco DCO device context
+ * @param multi TLS multi instance
+ */
+void dco_update_keys(dco_context_t *dco, struct tls_multi *multi);
+
#else /* if defined(ENABLE_DCO) */
typedef void *dco_context_t;
@@ -192,5 +200,11 @@ init_key_dco_bi(struct tls_multi *multi, struct key_state *ks,
return 0;
}
+static inline void
+dco_update_keys(dco_context_t *dco, struct tls_multi *multi)
+{
+ ASSERT(false);
+}
+
#endif /* defined(ENABLE_DCO) */
#endif /* ifndef DCO_H */
@@ -41,6 +41,7 @@
#include "dhcp.h"
#include "common.h"
#include "ssl_verify.h"
+#include "dco.h"
#include "memdbg.h"
@@ -140,6 +141,18 @@ context_reschedule_sec(struct context *c, int sec)
}
}
+void
+check_dco_key_status(struct context *c)
+{
+ /* DCO context is not yet initialised or enabled */
+ if (!dco_enabled(&c->options))
+ {
+ return;
+ }
+
+ dco_update_keys(&c->c1.tuntap->dco, c->c2.tls_multi);
+}
+
/*
* In TLS mode, let TLS level respond to any control-channel
* packets which were received, or prepare any packets for
@@ -182,6 +195,12 @@ check_tls(struct context *c)
interval_schedule_wakeup(&c->c2.tmp_int, &wakeup);
+ /* Our current code has no good hooks in the TLS machinery to update
+ * DCO keys. So we check the key status after the whole TLS machinery
+ * has been completed and potentially update them
+ */
+ check_dco_key_status(c);
+
if (wakeup)
{
context_reschedule_sec(c, wakeup);
Data channel keys are periodically regenarated and installed in ovpn-dco. However, there is a certain moment when keys are rotated in order to elect the new primary one. Check the key status in userspace so that kernelspace can be informed as well when rotations happen. Signed-off-by: Antonio Quartulli <a@unstable.cc> --- Changes from v2: * reworked dco_update_keys(): ** removed existing ASSERTs on keys and converted into something more logic and related to the flow ** fixed comment about userspace (use "we" for more clarity) ** add error code handling. The idea is to abort operations as soon as a failure is detected, so that the next iteration can make another attempt. Changes from v1: * added comments to ASSERT() in dco_update_keys() --- src/openvpn/dco.c | 122 ++++++++++++++++++++++++++++++++++++++++++ src/openvpn/dco.h | 14 +++++ src/openvpn/forward.c | 19 +++++++ 3 files changed, 155 insertions(+)