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xfrm: redact SA secret with lockdown confidentiality

Browse source 
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: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Antony Antony 2020-11-17 17:47:23 +01:00 committed by Steffen Klassert
parent 8be33ecfc1
commit c7a5899eb2
3 changed files with 69 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
include/linux/security.h
View file

@ -127,6 +127,7 @@ enum lockdown_reason {
LOCKDOWN_PERF,
LOCKDOWN_TRACEFS,
LOCKDOWN_XMON_RW,
LOCKDOWN_XFRM_SECRET,
LOCKDOWN_CONFIDENTIALITY_MAX,
};

74
net/xfrm/xfrm_user.c
View file

@ -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;
}

1
security/security.c
View file

@ -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",
};