[ipsec-next,v5] xfrm: redact SA secret with lockdown confidentiality

diff --git a/include/linux/security.h b/include/linux/security.h
index bc2725491560..1112a79a7dba 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -127,6 +127,7 @@  enum lockdown_reason {
 	LOCKDOWN_PERF,
 	LOCKDOWN_TRACEFS,
 	LOCKDOWN_XMON_RW,
+	LOCKDOWN_XFRM_SECRET,
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
 
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index d0c32a8fcc4a..0727ac853b55 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -848,21 +848,84 @@  static int copy_user_offload(struct xfrm_state_offload *xso, struct sk_buff *skb
 	return 0;
 }
 
+static bool xfrm_redact(void)
+{
+	return IS_ENABLED(CONFIG_SECURITY) &&
+		security_locked_down(LOCKDOWN_XFRM_SECRET);
+}
+
 static int copy_to_user_auth(struct xfrm_algo_auth *auth, struct sk_buff *skb)
 {
 	struct xfrm_algo *algo;
+	struct xfrm_algo_auth *ap;
 	struct nlattr *nla;
+	bool redact_secret = xfrm_redact();
 
 	nla = nla_reserve(skb, XFRMA_ALG_AUTH,
 			  sizeof(*algo) + (auth->alg_key_len + 7) / 8);
 	if (!nla)
 		return -EMSGSIZE;
-
 	algo = nla_data(nla);
 	strncpy(algo->alg_name, auth->alg_name, sizeof(algo->alg_name));
-	memcpy(algo->alg_key, auth->alg_key, (auth->alg_key_len + 7) / 8);
+
+	if (redact_secret && auth->alg_key_len)
+		memset(algo->alg_key, 0, (auth->alg_key_len + 7) / 8);
+	else
+		memcpy(algo->alg_key, auth->alg_key,
+		       (auth->alg_key_len + 7) / 8);
 	algo->alg_key_len = auth->alg_key_len;
 
+	nla = nla_reserve(skb, XFRMA_ALG_AUTH_TRUNC, xfrm_alg_auth_len(auth));
+	if (!nla)
+		return -EMSGSIZE;
+	ap = nla_data(nla);
+	memcpy(ap, auth, sizeof(struct xfrm_algo_auth));
+	if (redact_secret && auth->alg_key_len)
+		memset(ap->alg_key, 0, (auth->alg_key_len + 7) / 8);
+	else
+		memcpy(ap->alg_key, auth->alg_key,
+		       (auth->alg_key_len + 7) / 8);
+	return 0;
+}
+
+static int copy_to_user_aead(struct xfrm_algo_aead *aead, struct sk_buff *skb)
+{
+	struct nlattr *nla = nla_reserve(skb, XFRMA_ALG_AEAD, aead_len(aead));
+	struct xfrm_algo_aead *ap;
+	bool redact_secret = xfrm_redact();
+
+	if (!nla)
+		return -EMSGSIZE;
+
+	ap = nla_data(nla);
+	memcpy(ap, aead, sizeof(*aead));
+
+	if (redact_secret && aead->alg_key_len)
+		memset(ap->alg_key, 0, (aead->alg_key_len + 7) / 8);
+	else
+		memcpy(ap->alg_key, aead->alg_key,
+		       (aead->alg_key_len + 7) / 8);
+	return 0;
+}
+
+static int copy_to_user_ealg(struct xfrm_algo *ealg, struct sk_buff *skb)
+{
+	struct xfrm_algo *ap;
+	bool redact_secret = xfrm_redact();
+	struct nlattr *nla = nla_reserve(skb, XFRMA_ALG_CRYPT,
+					 xfrm_alg_len(ealg));
+	if (!nla)
+		return -EMSGSIZE;
+
+	ap = nla_data(nla);
+	memcpy(ap, ealg, sizeof(*ealg));
+
+	if (redact_secret && ealg->alg_key_len)
+		memset(ap->alg_key, 0, (ealg->alg_key_len + 7) / 8);
+	else
+		memcpy(ap->alg_key, ealg->alg_key,
+		       (ealg->alg_key_len + 7) / 8);
+
 	return 0;
 }
 
@@ -906,20 +969,17 @@  static int copy_to_user_state_extra(struct xfrm_state *x,
 			goto out;
 	}
 	if (x->aead) {
-		ret = nla_put(skb, XFRMA_ALG_AEAD, aead_len(x->aead), x->aead);
+		ret = copy_to_user_aead(x->aead, skb);
 		if (ret)
 			goto out;
 	}
 	if (x->aalg) {
 		ret = copy_to_user_auth(x->aalg, skb);
-		if (!ret)
-			ret = nla_put(skb, XFRMA_ALG_AUTH_TRUNC,
-				      xfrm_alg_auth_len(x->aalg), x->aalg);
 		if (ret)
 			goto out;
 	}
 	if (x->ealg) {
-		ret = nla_put(skb, XFRMA_ALG_CRYPT, xfrm_alg_len(x->ealg), x->ealg);
+		ret = copy_to_user_ealg(x->ealg, skb);
 		if (ret)
 			goto out;
 	}
diff --git a/security/security.c b/security/security.c
index a28045dc9e7f..abff77c1c8a7 100644
--- a/security/security.c
+++ b/security/security.c
@@ -65,6 +65,7 @@  const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
 	[LOCKDOWN_PERF] = "unsafe use of perf",
 	[LOCKDOWN_TRACEFS] = "use of tracefs",
 	[LOCKDOWN_XMON_RW] = "xmon read and write access",
+	[LOCKDOWN_XFRM_SECRET] = "xfrm SA secret",
 	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };