Commit c7a5899e authored by Antony Antony's avatar Antony Antony Committed by Steffen Klassert
Browse files

xfrm: redact SA secret with lockdown confidentiality 



redact XFRM SA secret in the netlink response to xfrm_get_sa()
or dumpall sa.
Enable lockdown, confidentiality mode, at boot or at run time.

e.g. when enabled:
cat /sys/kernel/security/lockdown
none integrity [confidentiality]

ip xfrm state
src 172.16.1.200 dst 172.16.1.100
	proto esp spi 0x00000002 reqid 2 mode tunnel
	replay-window 0
	aead rfc4106(gcm(aes)) 0x0000000000000000000000000000000000000000 96

note: the aead secret is redacted.
Redacting secret is also a FIPS 140-2 requirement.

v1->v2
 - add size checks before memset calls
v2->v3
 - replace spaces with tabs for consistency
v3->v4
 - use kernel lockdown instead of a /proc setting
v4->v5
 - remove kconfig option

Reviewed-by: default avatarStephan Mueller <smueller@chronox.de>
Signed-off-by: default avatarAntony Antony <antony.antony@secunet.com>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent 8be33ecf

include/linux/security.h

+1 −0
Original line number Diff line number Diff line
@@ -127,6 +127,7 @@ enum lockdown_reason { 
	LOCKDOWN_PERF,

	LOCKDOWN_TRACEFS,

	LOCKDOWN_XMON_RW,

	LOCKDOWN_XFRM_SECRET,

	LOCKDOWN_CONFIDENTIALITY_MAX,

};

net/xfrm/xfrm_user.c

+67 −7
Original line number Diff line number Diff line
@@ -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;

	}

security/security.c

+1 −0
Original line number Diff line number Diff line
@@ -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",

};

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