[PATCH net-next v9 19/23] ovpn: implement key add/del/swap via netlink

Antonio Quartulli
2024-10-16T01:04:22Z

This change introduces the netlink commands needed to add, delete and
swap keys for a specific peer.

Userspace is expected to use these commands to create, destroy and
rotate session keys for a specific peer.

Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
---
drivers/net/ovpn/netlink.c | 210 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 207 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ovpn/netlink.c b/drivers/net/ovpn/netlink.c
index d504445325ef82db04f87367c858adaf025f6297..bb96645205b6704f7066b7de9a003e01e63c10f7 100644
--- a/drivers/net/ovpn/netlink.c
+++ b/drivers/net/ovpn/netlink.c
@@ -679,9 +679,140 @@ int ovpn_nl_peer_del_doit(struct sk_buff *skb, struct genl_info *info)
return ret;
}

+static int ovpn_nl_get_key_dir(struct genl_info *info, struct nlattr *key,
+ enum ovpn_cipher_alg cipher,
+ struct ovpn_key_direction *dir)
+{
+ struct nlattr *attrs[OVPN_A_KEYDIR_MAX + 1];
+ int ret;
+
+ ret = nla_parse_nested(attrs, OVPN_A_KEYDIR_MAX, key,
+ ovpn_keydir_nl_policy, info->extack);
+ if (ret)
+ return ret;
+
+ switch (cipher) {
+ case OVPN_CIPHER_ALG_AES_GCM:
+ case OVPN_CIPHER_ALG_CHACHA20_POLY1305:
+ if (NL_REQ_ATTR_CHECK(info->extack, key, attrs,
+ OVPN_A_KEYDIR_CIPHER_KEY) ||
+ NL_REQ_ATTR_CHECK(info->extack, key, attrs,
+ OVPN_A_KEYDIR_NONCE_TAIL))
+ return -EINVAL;
+
+ dir->cipher_key = nla_data(attrs[OVPN_A_KEYDIR_CIPHER_KEY]);
+ dir->cipher_key_size = nla_len(attrs[OVPN_A_KEYDIR_CIPHER_KEY]);
+
+ /* These algorithms require a 96bit nonce,
+ * Construct it by combining 4-bytes packet id and
+ * 8-bytes nonce-tail from userspace
+ */
+ dir->nonce_tail = nla_data(attrs[OVPN_A_KEYDIR_NONCE_TAIL]);
+ dir->nonce_tail_size = nla_len(attrs[OVPN_A_KEYDIR_NONCE_TAIL]);
+ break;
+ default:
+ NL_SET_ERR_MSG_MOD(info->extack, "unsupported cipher");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/**
+ * ovpn_nl_key_new_doit - configure a new key for the specified peer
+ * @skb: incoming netlink message
+ * @info: genetlink metadata
+ *
+ * This function allows the user to install a new key in the peer crypto
+ * state.
+ * Each peer has two 'slots', namely 'primary' and 'secondary', where
+ * keys can be installed. The key in the 'primary' slot is used for
+ * encryption, while both keys can be used for decryption by matching the
+ * key ID carried in the incoming packet.
+ *
+ * The user is responsible for rotating keys when necessary. The user
+ * may fetch peer traffic statistics via netlink in order to better
+ * identify the right time to rotate keys.
+ * The renegotiation follows these steps:
+ * 1. a new key is computed by the user and is installed in the 'secondary'
+ * slot
+ * 2. at user discretion (usually after a predetermined time) 'primary' and
+ * 'secondary' contents are swapped and the new key starts being used for
+ * encryption, while the old key is kept around for decryption of late
+ * packets.
+ *
+ * Return: 0 on success or a negative error code otherwise.
+ */
int ovpn_nl_key_new_doit(struct sk_buff *skb, struct genl_info *info)
{
- return -EOPNOTSUPP;
+ struct nlattr *attrs[OVPN_A_KEYCONF_MAX + 1];
+ struct ovpn_struct *ovpn = info->user_ptr[0];
+ struct ovpn_peer_key_reset pkr;
+ struct ovpn_peer *peer;
+ u32 peer_id;
+ int ret;
+
+ if (GENL_REQ_ATTR_CHECK(info, OVPN_A_KEYCONF))
+ return -EINVAL;
+
+ ret = nla_parse_nested(attrs, OVPN_A_KEYCONF_MAX,
+ info->attrs[OVPN_A_KEYCONF],
+ ovpn_keyconf_nl_policy, info->extack);
+ if (ret)
+ return ret;
+
+ if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_PEER_ID))
+ return -EINVAL;
+
+ if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_SLOT) ||
+ NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_KEY_ID) ||
+ NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_CIPHER_ALG) ||
+ NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_ENCRYPT_DIR) ||
+ NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_DECRYPT_DIR))
+ return -EINVAL;
+
+ peer_id = nla_get_u32(attrs[OVPN_A_KEYCONF_PEER_ID]);
+ pkr.slot = nla_get_u8(attrs[OVPN_A_KEYCONF_SLOT]);
+ pkr.key.key_id = nla_get_u16(attrs[OVPN_A_KEYCONF_KEY_ID]);
+ pkr.key.cipher_alg = nla_get_u16(attrs[OVPN_A_KEYCONF_CIPHER_ALG]);
+
+ ret = ovpn_nl_get_key_dir(info, attrs[OVPN_A_KEYCONF_ENCRYPT_DIR],
+ pkr.key.cipher_alg, &pkr.key.encrypt);
+ if (ret < 0)
+ return ret;
+
+ ret = ovpn_nl_get_key_dir(info, attrs[OVPN_A_KEYCONF_DECRYPT_DIR],
+ pkr.key.cipher_alg, &pkr.key.decrypt);
+ if (ret < 0)
+ return ret;
+
+ peer = ovpn_peer_get_by_id(ovpn, peer_id);
+ if (!peer) {
+ NL_SET_ERR_MSG_FMT_MOD(info->extack,
+ "no peer with id %u to set key for",
+ peer_id);
+ return -ENOENT;
+ }
+
+ ret = ovpn_crypto_state_reset(&peer->crypto, &pkr);
+ if (ret < 0) {
+ NL_SET_ERR_MSG_FMT_MOD(info->extack,
+ "cannot install new key for peer %u",
+ peer_id);
+ goto out;
+ }
+
+ netdev_dbg(ovpn->dev, "%s: new key installed (id=%u) for peer %u\n",
+ __func__, pkr.key.key_id, peer_id);
+out:
+ ovpn_peer_put(peer);
+ return ret;
}

int ovpn_nl_key_get_doit(struct sk_buff *skb, struct genl_info *info)
@@ -691,12 +822,85 @@ int ovpn_nl_key_get_doit(struct sk_buff *skb, struct genl_info *info)

int ovpn_nl_key_swap_doit(struct sk_buff *skb, struct genl_info *info)
{
- return -EOPNOTSUPP;
+ struct ovpn_struct *ovpn = info->user_ptr[0];
+ struct nlattr *attrs[OVPN_A_PEER_MAX + 1];
+ struct ovpn_peer *peer;
+ u32 peer_id;
+ int ret;
+
+ if (GENL_REQ_ATTR_CHECK(info, OVPN_A_KEYCONF))
+ return -EINVAL;
+
+ ret = nla_parse_nested(attrs, OVPN_A_KEYCONF_MAX,
+ info->attrs[OVPN_A_KEYCONF],
+ ovpn_keyconf_nl_policy, info->extack);
+ if (ret)
+ return ret;
+
+ if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_PEER_ID))
+ return -EINVAL;
+
+ peer_id = nla_get_u32(attrs[OVPN_A_KEYCONF_PEER_ID]);
+
+ peer = ovpn_peer_get_by_id(ovpn, peer_id);
+ if (!peer) {
+ NL_SET_ERR_MSG_FMT_MOD(info->extack,
+ "no peer with id %u to swap keys for",
+ peer_id);
+ return -ENOENT;
+ }
+
+ ovpn_crypto_key_slots_swap(&peer->crypto);
+ ovpn_peer_put(peer);
+
+ return 0;
}

int ovpn_nl_key_del_doit(struct sk_buff *skb, struct genl_info *info)
{
- return -EOPNOTSUPP;
+ struct nlattr *attrs[OVPN_A_KEYCONF_MAX + 1];
+ struct ovpn_struct *ovpn = info->user_ptr[0];
+ enum ovpn_key_slot slot;
+ struct ovpn_peer *peer;
+ u32 peer_id;
+ int ret;
+
+ if (GENL_REQ_ATTR_CHECK(info, OVPN_A_KEYCONF))
+ return -EINVAL;
+
+ ret = nla_parse_nested(attrs, OVPN_A_KEYCONF_MAX,
+ info->attrs[OVPN_A_KEYCONF],
+ ovpn_keyconf_nl_policy, info->extack);
+ if (ret)
+ return ret;
+
+ if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_PEER_ID))
+ return -EINVAL;
+
+ if (ret)
+ return ret;
+
+ if (NL_REQ_ATTR_CHECK(info->extack, info->attrs[OVPN_A_KEYCONF], attrs,
+ OVPN_A_KEYCONF_SLOT))
+ return -EINVAL;
+
+ peer_id = nla_get_u32(attrs[OVPN_A_KEYCONF_PEER_ID]);
+ slot = nla_get_u8(attrs[OVPN_A_KEYCONF_SLOT]);
+
+ peer = ovpn_peer_get_by_id(ovpn, peer_id);
+ if (!peer) {
+ NL_SET_ERR_MSG_FMT_MOD(info->extack,
+ "no peer with id %u to delete key for",
+ peer_id);
+ return -ENOENT;
+ }
+
+ ovpn_crypto_key_slot_delete(&peer->crypto, slot);
+ ovpn_peer_put(peer);
+
+ return 0;
}

/**

--
2.45.2