From: Antonio Quartulli Date: Tue, 2 Aug 2022 15:16:04 +0000 (+0200) Subject: dco: periodically check and possibly rotate/delete keys X-Git-Tag: v2.6_beta1~142 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cd4ba9279d9c4cf13cdc3d8c49143c57eb0fe448;p=thirdparty%2Fopenvpn.git dco: periodically check and possibly rotate/delete keys Data channel keys are periodically regenerated 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 Acked-by: Gert Doering Message-Id: <20220802151604.2801-1-a@unstable.cc> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24785.html Signed-off-by: Gert Doering --- diff --git a/src/openvpn/dco.c b/src/openvpn/dco.c index b0dd922a1..b92a0e9c9 100644 --- a/src/openvpn/dco.c +++ b/src/openvpn/dco.c @@ -94,6 +94,129 @@ 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); + /* if the current primary key was installed as secondary in DCO, + * this means we have promoted it since installation in DCO, and + * we now need to 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) { diff --git a/src/openvpn/dco.h b/src/openvpn/dco.h index 1692f5c34..b926e2369 100644 --- a/src/openvpn/dco.h +++ b/src/openvpn/dco.h @@ -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 */ diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c index 28f3c088a..38d2683ca 100644 --- a/src/openvpn/forward.c +++ b/src/openvpn/forward.c @@ -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);