Subject: [RFC net-next 05/15] psp: add op for rotation of secret state

From: Jakub Kicinski <[email-masked]>
Date: Thu, 9 May 2024 20:04:25 -0700

Rotating the secret state is a key part of the PSP protocol design.
Some external daemon needs to do it once a day, or so.
Add a netlink op to perform this operation.
Add a notification group for informing users that key has been
rotated and they should rekey (next rotation will cut them off).

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 Documentation/netlink/specs/psp.yaml | 21 +++++++++++++++
 include/net/psp/types.h              |  5 ++++
 include/uapi/linux/psp.h             |  3 +++
 net/psp/psp-nl-gen.c                 | 15 +++++++++++
 net/psp/psp-nl-gen.h                 |  2 ++
 net/psp/psp_main.c                   |  3 ++-
 net/psp/psp_nl.c                     | 40 ++++++++++++++++++++++++++++
 7 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/Documentation/netlink/specs/psp.yaml b/Documentation/netlink/specs/psp.yaml
index dbb5ef148045..6ae598a60b3f 100644
--- a/Documentation/netlink/specs/psp.yaml
+++ b/Documentation/netlink/specs/psp.yaml
@@ -88,7 +88,28 @@ name: psp
       notify: dev-get
       mcgrp: mgmt
 
+    -
+      name: key-rotate
+      doc: Rotate the secret state.
+      attribute-set: dev
+      do:
+        request:
+          attributes:
+            - id
+        reply:
+          attributes:
+            - id
+        pre: psp-device-get-locked
+        post: psp-device-unlock
+    -
+      name: key-rotate-ntf
+      doc: Notification about secret state getting rotated.
+      notify: key-rotate
+      mcgrp: use
+
 mcast-groups:
   list:
     -
       name: mgmt
+    -
+      name: use
diff --git a/include/net/psp/types.h b/include/net/psp/types.h
index a23d9bd9ce96..43950caf70f1 100644
--- a/include/net/psp/types.h
+++ b/include/net/psp/types.h
@@ -104,6 +104,11 @@ struct psp_dev_ops {
 	 */
 	int (*set_config)(struct psp_dev *psd, struct psp_dev_config *conf,
 			  struct netlink_ext_ack *extack);
+
+	/**
+	 * @key_rotate: rotate the secret state
+	 */
+	int (*key_rotate)(struct psp_dev *psd, struct netlink_ext_ack *extack);
 };
 
 #endif /* __NET_PSP_H */
diff --git a/include/uapi/linux/psp.h b/include/uapi/linux/psp.h
index 4a404f085190..cbfbf3f0f364 100644
--- a/include/uapi/linux/psp.h
+++ b/include/uapi/linux/psp.h
@@ -32,11 +32,14 @@ enum {
 	PSP_CMD_DEV_DEL_NTF,
 	PSP_CMD_DEV_SET,
 	PSP_CMD_DEV_CHANGE_NTF,
+	PSP_CMD_KEY_ROTATE,
+	PSP_CMD_KEY_ROTATE_NTF,
 
 	__PSP_CMD_MAX,
 	PSP_CMD_MAX = (__PSP_CMD_MAX - 1)
 };
 
 #define PSP_MCGRP_MGMT	"mgmt"
+#define PSP_MCGRP_USE	"use"
 
 #endif /* _UAPI_LINUX_PSP_H */
diff --git a/net/psp/psp-nl-gen.c b/net/psp/psp-nl-gen.c
index 859712e7c2c1..7f49577ac72f 100644
--- a/net/psp/psp-nl-gen.c
+++ b/net/psp/psp-nl-gen.c
@@ -21,6 +21,11 @@ static const struct nla_policy psp_dev_set_nl_policy[PSP_A_DEV_PSP_VERSIONS_ENA
 	[PSP_A_DEV_PSP_VERSIONS_ENA] = NLA_POLICY_MASK(NLA_U32, 0xf),
 };
 
+/* PSP_CMD_KEY_ROTATE - do */
+static const struct nla_policy psp_key_rotate_nl_policy[PSP_A_DEV_ID + 1] = {
+	[PSP_A_DEV_ID] = NLA_POLICY_MIN(NLA_U32, 1),
+};
+
 /* Ops table for psp */
 static const struct genl_split_ops psp_nl_ops[] = {
 	{
@@ -46,10 +51,20 @@ static const struct genl_split_ops psp_nl_ops[] = {
 		.maxattr	= PSP_A_DEV_PSP_VERSIONS_ENA,
 		.flags		= GENL_CMD_CAP_DO,
 	},
+	{
+		.cmd		= PSP_CMD_KEY_ROTATE,
+		.pre_doit	= psp_device_get_locked,
+		.doit		= psp_nl_key_rotate_doit,
+		.post_doit	= psp_device_unlock,
+		.policy		= psp_key_rotate_nl_policy,
+		.maxattr	= PSP_A_DEV_ID,
+		.flags		= GENL_CMD_CAP_DO,
+	},
 };
 
 static const struct genl_multicast_group psp_nl_mcgrps[] = {
 	[PSP_NLGRP_MGMT] = { "mgmt", },
+	[PSP_NLGRP_USE] = { "use", },
 };
 
 struct genl_family psp_nl_family __ro_after_init = {
diff --git a/net/psp/psp-nl-gen.h b/net/psp/psp-nl-gen.h
index a099686cab5d..00a2d4ec59e4 100644
--- a/net/psp/psp-nl-gen.h
+++ b/net/psp/psp-nl-gen.h
@@ -20,9 +20,11 @@ psp_device_unlock(const struct genl_split_ops *ops, struct sk_buff *skb,
 int psp_nl_dev_get_doit(struct sk_buff *skb, struct genl_info *info);
 int psp_nl_dev_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
 int psp_nl_dev_set_doit(struct sk_buff *skb, struct genl_info *info);
+int psp_nl_key_rotate_doit(struct sk_buff *skb, struct genl_info *info);
 
 enum {
 	PSP_NLGRP_MGMT,
+	PSP_NLGRP_USE,
 };
 
 extern struct genl_family psp_nl_family;
diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
index cf463f757892..536f50d82fb2 100644
--- a/net/psp/psp_main.c
+++ b/net/psp/psp_main.c
@@ -54,7 +54,8 @@ psp_dev_create(struct net_device *netdev,
 	int err;
 
 	if (WARN_ON(!psd_caps->versions ||
-		    !psd_ops->set_config))
+		    !psd_ops->set_config ||
+		    !psd_ops->key_rotate))
 		return ERR_PTR(-EINVAL);
 
 	psd = kzalloc(sizeof(*psd), GFP_KERNEL);
diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c
index fda5ce800f82..b7006e50dc87 100644
--- a/net/psp/psp_nl.c
+++ b/net/psp/psp_nl.c
@@ -221,3 +221,43 @@ int psp_nl_dev_set_doit(struct sk_buff *skb, struct genl_info *info)
 	nlmsg_free(rsp);
 	return err;
 }
+
+int psp_nl_key_rotate_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct psp_dev *psd = info->user_ptr[0];
+	struct genl_info ntf_info;
+	struct sk_buff *ntf, *rsp;
+	int err;
+
+	rsp = psp_nl_reply_new(info);
+	if (!rsp)
+		return -ENOMEM;
+
+	genl_info_init_ntf(&ntf_info, &psp_nl_family, PSP_CMD_KEY_ROTATE);
+	ntf = psp_nl_reply_new(&ntf_info);
+	if (!ntf) {
+		err = -ENOMEM;
+		goto err_free_rsp;
+	}
+
+	if (nla_put_u32(rsp, PSP_A_DEV_ID, psd->id) ||
+	    nla_put_u32(ntf, PSP_A_DEV_ID, psd->id)) {
+		err = -EMSGSIZE;
+		goto err_free_ntf;
+	}
+
+	err = psd->ops->key_rotate(psd, info->extack);
+	if (err)
+		goto err_free_ntf;
+
+	nlmsg_end(ntf, (struct nlmsghdr *)ntf->data);
+	genlmsg_multicast_netns(&psp_nl_family, dev_net(psd->main_netdev), ntf,
+				0, PSP_NLGRP_USE, GFP_KERNEL);
+	return psp_nl_reply_send(rsp, info);
+
+err_free_ntf:
+	nlmsg_free(ntf);
+err_free_rsp:
+	nlmsg_free(rsp);
+	return err;
+}
-- 
2.45.0