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Message-ID: <20201016133352.GA2338@moon.secunet.de>
Date: Fri, 16 Oct 2020 15:36:12 +0200
From: Antony Antony <antony.antony@...unet.com>
To: Steffen Klassert <steffen.klassert@...unet.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
"David S. Miller" <davem@...emloft.net>,
"Jakub Kicinski" <kuba@...nel.org>
CC: <netdev@...r.kernel.org>, <linux-security-module@...r.kernel.org>,
"Antony Antony" <antony.antony@...unet.com>,
Antony Antony <antony@...nome.org>,
Stephan Mueller <smueller@...onox.de>
Subject: [PATCH] xfrm: redact SA secret with lockdown confidentiality
redact XFRM SA secret in the netlink response to xfrm_get_sa()
or dumpall sa.
Enable this at build time and set kernel lockdown to confidentiality.
e.g.
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
Reviewed-by: Stephan Mueller <smueller@...onox.de>
Signed-off-by: Antony Antony <antony.antony@...unet.com>
---
include/linux/security.h | 1 +
net/xfrm/Kconfig | 9 +++++
net/xfrm/xfrm_user.c | 76 ++++++++++++++++++++++++++++++++++++----
security/security.c | 1 +
4 files changed, 80 insertions(+), 7 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index 0a0a03b36a3b..8438970473b1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -126,6 +126,7 @@ enum lockdown_reason {
LOCKDOWN_PERF,
LOCKDOWN_TRACEFS,
LOCKDOWN_XMON_RW,
+ LOCKDOWN_XFRM_SECRET,
LOCKDOWN_CONFIDENTIALITY_MAX,
};
diff --git a/net/xfrm/Kconfig b/net/xfrm/Kconfig
index 5b9a5ab48111..cb592524701d 100644
--- a/net/xfrm/Kconfig
+++ b/net/xfrm/Kconfig
@@ -91,6 +91,15 @@ config XFRM_ESP
select CRYPTO_SEQIV
select CRYPTO_SHA256
+config XFRM_REDACT_SECRET
+ bool "Redact xfrm SA secret"
+ depends on XFRM && SECURITY_LOCKDOWN_LSM
+ default n
+ help
+ Redats XFRM SA secret in the netlink message to user space.
+ Redacting secret is also a FIPS 140-2 requirement.
+ e.g. ip xfrm state; will show redacted the SA secret.
+
config XFRM_IPCOMP
tristate
select XFRM_ALGO
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index fbb7d9d06478..b57599d050dc 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -11,6 +11,7 @@
*
*/
+#include <linux/fips.h>
#include <linux/crypto.h>
#include <linux/module.h>
#include <linux/kernel.h>
@@ -848,21 +849,85 @@ 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) &&
+ IS_ENABLED(CONFIG_XFRM_REDACT_SECRET) &&
+ 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 +971,17 @@ 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 70a7ad357bc6..72d9aac7178a 100644
--- a/security/security.c
+++ b/security/security.c
@@ -64,6 +64,7 @@ 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",
};
--
2.20.1
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