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Message-ID: <75b3fed9-e549-4ed0-c435-ec4795fc1e39@schaufler-ca.com>
Date: Wed, 19 Sep 2018 16:36:33 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Christian Göttsche <cgzones@...glemail.com>,
pablo@...filter.org, kadlec@...ckhole.kfki.hu, fw@...len.de,
davem@...emloft.net, netfilter-devel@...r.kernel.org,
coreteam@...filter.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, paul@...l-moore.com,
sds@...ho.nsa.gov, eparis@...isplace.org, jmorris@...ei.org,
serge@...lyn.com, selinux@...ho.nsa.gov,
linux-security-module@...r.kernel.org
Subject: Re: [PATCH] netfilter: nf_tables: add SECMARK support
On 9/19/2018 4:14 PM, Christian Göttsche wrote:
> Add the ability to set the security context of packets within the nf_tables framework.
> Add a nft_object for holding security contexts in the kernel and manipulating packets on the wire.
> The contexts are kept as strings and are evaluated to security identifiers at runtime (packet arrival),
> so that the nft_objects do not need to be refreshed after security changes.
> The maximum security context length is set to 256.
>
> Based on v4.18.6
>
> Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
I've only had a cursory look at your patch, but how is it
different from what's in xt_SECMARK.c ?
> ---
> include/net/netfilter/nf_tables_core.h | 4 +
> include/uapi/linux/netfilter/nf_tables.h | 18 ++++-
> net/netfilter/nf_tables_core.c | 28 ++++++-
> net/netfilter/nft_meta.c | 95 ++++++++++++++++++++++++
> 4 files changed, 140 insertions(+), 5 deletions(-)
>
> diff --git a/include/net/netfilter/nf_tables_core.h b/include/net/netfilter/nf_tables_core.h
> index a0513450..0d1f3b96 100644
> --- a/include/net/netfilter/nf_tables_core.h
> +++ b/include/net/netfilter/nf_tables_core.h
> @@ -16,6 +16,10 @@ extern struct nft_expr_type nft_meta_type;
> extern struct nft_expr_type nft_rt_type;
> extern struct nft_expr_type nft_exthdr_type;
>
> +#ifdef CONFIG_NETWORK_SECMARK
> +extern struct nft_object_type nft_secmark_obj_type;
> +#endif
> +
> int nf_tables_core_module_init(void);
> void nf_tables_core_module_exit(void);
>
> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> index 89438e68..f1527962 100644
> --- a/include/uapi/linux/netfilter/nf_tables.h
> +++ b/include/uapi/linux/netfilter/nf_tables.h
> @@ -1169,6 +1169,21 @@ enum nft_quota_attributes {
> };
> #define NFTA_QUOTA_MAX (__NFTA_QUOTA_MAX - 1)
>
> +/**
> + * enum nft_secmark_attributes - nf_tables secmark object netlink attributes
> + *
> + * @NFTA_SECMARK_CTX: security context (NLA_STRING)
> + */
> +enum nft_secmark_attributes {
> + NFTA_SECMARK_UNSPEC,
> + NFTA_SECMARK_CTX,
> + __NFTA_SECMARK_MAX,
> +};
> +#define NFTA_SECMARK_MAX (__NFTA_SECMARK_MAX - 1)
> +
> +/* Max security context length */
> +#define NFT_SECMARK_CTX_MAXLEN 256
> +
> /**
> * enum nft_reject_types - nf_tables reject expression reject types
> *
> @@ -1398,7 +1413,8 @@ enum nft_ct_helper_attributes {
> #define NFT_OBJECT_CT_HELPER 3
> #define NFT_OBJECT_LIMIT 4
> #define NFT_OBJECT_CONNLIMIT 5
> -#define __NFT_OBJECT_MAX 6
> +#define NFT_OBJECT_SECMARK 6
> +#define __NFT_OBJECT_MAX 7
> #define NFT_OBJECT_MAX (__NFT_OBJECT_MAX - 1)
>
> /**
> diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
> index 8de912ca..d59ebba0 100644
> --- a/net/netfilter/nf_tables_core.c
> +++ b/net/netfilter/nf_tables_core.c
> @@ -235,12 +235,24 @@ static struct nft_expr_type *nft_basic_types[] = {
> &nft_exthdr_type,
> };
>
> +static struct nft_object_type *nft_basic_objects[] = {
> +#ifdef CONFIG_NETWORK_SECMARK
> + &nft_secmark_obj_type,
> +#endif
> +};
> +
> int __init nf_tables_core_module_init(void)
> {
> - int err, i;
> + int err, i, j = 0;
> +
> + for (i = 0; i < ARRAY_SIZE(nft_basic_objects); i++) {
> + err = nft_register_obj(nft_basic_objects[i]);
> + if (err)
> + goto err;
> + }
>
> - for (i = 0; i < ARRAY_SIZE(nft_basic_types); i++) {
> - err = nft_register_expr(nft_basic_types[i]);
> + for (j = 0; j < ARRAY_SIZE(nft_basic_types); j++) {
> + err = nft_register_expr(nft_basic_types[j]);
> if (err)
> goto err;
> }
> @@ -248,8 +260,12 @@ int __init nf_tables_core_module_init(void)
> return 0;
>
> err:
> + while (j-- > 0)
> + nft_unregister_expr(nft_basic_types[j]);
> +
> while (i-- > 0)
> - nft_unregister_expr(nft_basic_types[i]);
> + nft_unregister_obj(nft_basic_objects[i]);
> +
> return err;
> }
>
> @@ -260,4 +276,8 @@ void nf_tables_core_module_exit(void)
> i = ARRAY_SIZE(nft_basic_types);
> while (i-- > 0)
> nft_unregister_expr(nft_basic_types[i]);
> +
> + i = ARRAY_SIZE(nft_basic_objects);
> + while (i-- > 0)
> + nft_unregister_obj(nft_basic_objects[i]);
> }
> diff --git a/net/netfilter/nft_meta.c b/net/netfilter/nft_meta.c
> index 1105a23b..26b79a3c 100644
> --- a/net/netfilter/nft_meta.c
> +++ b/net/netfilter/nft_meta.c
> @@ -540,3 +540,98 @@ struct nft_expr_type nft_meta_type __read_mostly = {
> .maxattr = NFTA_META_MAX,
> .owner = THIS_MODULE,
> };
> +
> +#ifdef CONFIG_NETWORK_SECMARK
> +
> +struct nft_secmark {
> + char ctx[NFT_SECMARK_CTX_MAXLEN];
> + int len;
> +};
> +
> +static const struct nla_policy nft_secmark_policy[NFTA_SECMARK_MAX + 1] = {
> + [NFTA_SECMARK_CTX] = { .type = NLA_STRING, .len = NFT_SECMARK_CTX_MAXLEN },
> +};
> +
> +
> +static void nft_secmark_obj_eval(struct nft_object *obj, struct nft_regs *regs, const struct nft_pktinfo *pkt)
> +{
> + const struct nft_secmark *priv = nft_obj_data(obj);
> + struct sk_buff *skb = pkt->skb;
> + int err;
> + u32 secid = 0;
> +
> + /* skip if packet has already a secmark */
> + if (skb->secmark)
> + return;
> +
> + err = security_secctx_to_secid(priv->ctx, priv->len, &secid);
> + if (err) {
> + if (err == -EINVAL)
> + pr_notice_ratelimited("invalid security context \'%s\'\n", priv->ctx);
> + else
> + pr_notice_ratelimited("unable to convert security context \'%s\': %d\n", priv->ctx, -err);
> + return;
> + }
> +
> + if (!secid) {
> + pr_notice_ratelimited("unable to map security context \'%s\'\n", priv->ctx);
> + return;
> + }
> +
> + err = security_secmark_relabel_packet(secid);
> + if (err) {
> + pr_notice_ratelimited("unable to obtain relabeling permission: %d\n", -err);
> + return;
> + }
> +
> + skb->secmark = secid;
> +}
> +
> +
> +static int nft_secmark_obj_init(const struct nft_ctx *ctx, const struct nlattr * const tb[], struct nft_object *obj)
> +{
> + struct nft_secmark *priv = nft_obj_data(obj);
> +
> + if (tb[NFTA_SECMARK_CTX] == NULL)
> + return -EINVAL;
> +
> + nla_strlcpy(priv->ctx, tb[NFTA_SECMARK_CTX], NFT_SECMARK_CTX_MAXLEN);
> + priv->len = strlen(priv->ctx);
> +
> + security_secmark_refcount_inc();
> +
> + return 0;
> +}
> +
> +static int nft_secmark_obj_dump(struct sk_buff *skb, struct nft_object *obj, bool reset)
> +{
> + const struct nft_secmark *priv = nft_obj_data(obj);
> +
> + if (nla_put_string(skb, NFTA_SECMARK_CTX, priv->ctx))
> + return -1;
> +
> + return 0;
> +}
> +
> +static void nft_secmark_obj_destroy(const struct nft_ctx *ctx, struct nft_object *obj)
> +{
> + security_secmark_refcount_dec();
> +}
> +
> +static const struct nft_object_ops nft_secmark_obj_ops = {
> + .type = &nft_secmark_obj_type,
> + .size = sizeof(struct nft_secmark),
> + .init = nft_secmark_obj_init,
> + .eval = nft_secmark_obj_eval,
> + .dump = nft_secmark_obj_dump,
> + .destroy = nft_secmark_obj_destroy,
> +};
> +struct nft_object_type nft_secmark_obj_type __read_mostly = {
> + .type = NFT_OBJECT_SECMARK,
> + .ops = &nft_secmark_obj_ops,
> + .maxattr = NFTA_SECMARK_MAX,
> + .policy = nft_secmark_policy,
> + .owner = THIS_MODULE,
> +};
> +
> +#endif /* CONFIG_NETWORK_SECMARK */
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