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: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/include/linux/security.h b/include/linux/security.h
index bc27254..1112a79 100644 (file)
--- 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 d0c32a8..0727ac8 100644 (file)
--- 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 a28045d..abff77c 100644 (file)
--- 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",
 };