Re: [PATCH ghak124 v3] audit: log nftables configuration change events

From: Richard Guy Briggs
Date: Wed Jun 24 2020 - 08:35:19 EST

On 2020-06-24 12:03, Pablo Neira Ayuso wrote:
> On Thu, Jun 04, 2020 at 09:20:49AM -0400, Richard Guy Briggs wrote:
> > iptables, ip6tables, arptables and ebtables table registration,
> > replacement and unregistration configuration events are logged for the
> > native (legacy) iptables setsockopt api, but not for the
> > nftables netlink api which is used by the nft-variant of iptables in
> > addition to nftables itself.
> >
> > Add calls to log the configuration actions in the nftables netlink api.
> >
> > This uses the same NETFILTER_CFG record format but overloads the table
> > field.
> >
> > type=NETFILTER_CFG msg=audit(2020-05-28 17:46:41.878:162) : table=?:0;?:0 family=unspecified entries=2 op=nft_register_gen pid=396 subj=system_u:system_r:firewalld_t:s0 comm=firewalld
> > ...
> > type=NETFILTER_CFG msg=audit(2020-05-28 17:46:41.878:162) : table=firewalld:1;?:0 family=inet entries=0 op=nft_register_table pid=396 subj=system_u:system_r:firewalld_t:s0 comm=firewalld
> > ...
> > type=NETFILTER_CFG msg=audit(2020-05-28 17:46:41.911:163) : table=firewalld:1;filter_FORWARD:85 family=inet entries=8 op=nft_register_chain pid=396 subj=system_u:system_r:firewalld_t:s0 comm=firewalld
> > ...
> > type=NETFILTER_CFG msg=audit(2020-05-28 17:46:41.911:163) : table=firewalld:1;filter_FORWARD:85 family=inet entries=101 op=nft_register_rule pid=396 subj=system_u:system_r:firewalld_t:s0 comm=firewalld
> > ...
> > type=NETFILTER_CFG msg=audit(2020-05-28 17:46:41.911:163) : table=firewalld:1;__set0:87 family=inet entries=87 op=nft_register_setelem pid=396 subj=system_u:system_r:firewalld_t:s0 comm=firewalld
> > ...
> > type=NETFILTER_CFG msg=audit(2020-05-28 17:46:41.911:163) : table=firewalld:1;__set0:87 family=inet entries=0 op=nft_register_set pid=396 subj=system_u:system_r:firewalld_t:s0 comm=firewalld
> >
> > For further information please see issue
> > https://github.com/linux-audit/audit-kernel/issues/124
> >
> > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> > ---
> > Changelog:
> > v3:
> > - inline message type rather than table
> >
> > v2:
> > - differentiate between xtables and nftables
> > - add set, setelem, obj, flowtable, gen
> > - use nentries field as appropriate per type
> > - overload the "tables" field with table handle and chain/set/flowtable
> >
> > include/linux/audit.h | 18 ++++++++
> > kernel/auditsc.c | 24 ++++++++--
> > net/netfilter/nf_tables_api.c | 103 ++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 142 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index 3fcd9ee49734..604ede630580 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -12,6 +12,7 @@
> > #include <linux/sched.h>
> > #include <linux/ptrace.h>
> > #include <uapi/linux/audit.h>
> > +#include <uapi/linux/netfilter/nf_tables.h>
> >
> > #define AUDIT_INO_UNSET ((unsigned long)-1)
> > #define AUDIT_DEV_UNSET ((dev_t)-1)
> > @@ -98,6 +99,23 @@ enum audit_nfcfgop {
> > AUDIT_XT_OP_REGISTER,
> > AUDIT_XT_OP_REPLACE,
> > AUDIT_XT_OP_UNREGISTER,
> > + AUDIT_NFT_OP_TABLE_REGISTER,
> > + AUDIT_NFT_OP_TABLE_UNREGISTER,
> > + AUDIT_NFT_OP_CHAIN_REGISTER,
> > + AUDIT_NFT_OP_CHAIN_UNREGISTER,
> > + AUDIT_NFT_OP_RULE_REGISTER,
> > + AUDIT_NFT_OP_RULE_UNREGISTER,
> > + AUDIT_NFT_OP_SET_REGISTER,
> > + AUDIT_NFT_OP_SET_UNREGISTER,
> > + AUDIT_NFT_OP_SETELEM_REGISTER,
> > + AUDIT_NFT_OP_SETELEM_UNREGISTER,
> > + AUDIT_NFT_OP_GEN_REGISTER,
> > + AUDIT_NFT_OP_OBJ_REGISTER,
> > + AUDIT_NFT_OP_OBJ_UNREGISTER,
> > + AUDIT_NFT_OP_OBJ_RESET,
> > + AUDIT_NFT_OP_FLOWTABLE_REGISTER,
> > + AUDIT_NFT_OP_FLOWTABLE_UNREGISTER,
> > + AUDIT_NFT_OP_INVALID,
> > };
> >
> > extern int is_audit_feature_set(int which);
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index 468a23390457..3a9100e95fda 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -75,6 +75,7 @@
> > #include <linux/uaccess.h>
> > #include <linux/fsnotify_backend.h>
> > #include <uapi/linux/limits.h>
> > +#include <uapi/linux/netfilter/nf_tables.h>
> >
> > #include "audit.h"
> >
> > @@ -136,9 +137,26 @@ struct audit_nfcfgop_tab {
> > };
> >
> > static const struct audit_nfcfgop_tab audit_nfcfgs[] = {
> > - { AUDIT_XT_OP_REGISTER, "register" },
> > - { AUDIT_XT_OP_REPLACE, "replace" },
> > - { AUDIT_XT_OP_UNREGISTER, "unregister" },
> > + { AUDIT_XT_OP_REGISTER, "xt_register" },
> > + { AUDIT_XT_OP_REPLACE, "xt_replace" },
> > + { AUDIT_XT_OP_UNREGISTER, "xt_unregister" },
> > + { AUDIT_NFT_OP_TABLE_REGISTER, "nft_register_table" },
> > + { AUDIT_NFT_OP_TABLE_UNREGISTER, "nft_unregister_table" },
> > + { AUDIT_NFT_OP_CHAIN_REGISTER, "nft_register_chain" },
> > + { AUDIT_NFT_OP_CHAIN_UNREGISTER, "nft_unregister_chain" },
> > + { AUDIT_NFT_OP_RULE_REGISTER, "nft_register_rule" },
> > + { AUDIT_NFT_OP_RULE_UNREGISTER, "nft_unregister_rule" },
> > + { AUDIT_NFT_OP_SET_REGISTER, "nft_register_set" },
> > + { AUDIT_NFT_OP_SET_UNREGISTER, "nft_unregister_set" },
> > + { AUDIT_NFT_OP_SETELEM_REGISTER, "nft_register_setelem" },
> > + { AUDIT_NFT_OP_SETELEM_UNREGISTER, "nft_unregister_setelem" },
> > + { AUDIT_NFT_OP_GEN_REGISTER, "nft_register_gen" },
> > + { AUDIT_NFT_OP_OBJ_REGISTER, "nft_register_obj" },
> > + { AUDIT_NFT_OP_OBJ_UNREGISTER, "nft_unregister_obj" },
> > + { AUDIT_NFT_OP_OBJ_RESET, "nft_reset_obj" },
> > + { AUDIT_NFT_OP_FLOWTABLE_REGISTER, "nft_register_flowtable" },
> > + { AUDIT_NFT_OP_FLOWTABLE_UNREGISTER, "nft_unregister_flowtable" },
> > + { AUDIT_NFT_OP_INVALID, "nft_invalid" },
> > };
> >
> > static int audit_match_perm(struct audit_context *ctx, int mask)
> > diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> > index 3558e76e2733..b9e7440cc87d 100644
> > --- a/net/netfilter/nf_tables_api.c
> > +++ b/net/netfilter/nf_tables_api.c
> > @@ -12,6 +12,7 @@
> > #include <linux/netlink.h>
> > #include <linux/vmalloc.h>
> > #include <linux/rhashtable.h>
> > +#include <linux/audit.h>
> > #include <linux/netfilter.h>
> > #include <linux/netfilter/nfnetlink.h>
> > #include <linux/netfilter/nf_tables.h>
> > @@ -693,6 +694,16 @@ static void nf_tables_table_notify(const struct nft_ctx *ctx, int event)
> > {
> > struct sk_buff *skb;
> > int err;
> > + char *buf = kasprintf(GFP_KERNEL, "%s:%llu;?:0",
> > + ctx->table->name, ctx->table->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + ctx->family,
> > + ctx->table->use,
> > + event == NFT_MSG_NEWTABLE ?
> > + AUDIT_NFT_OP_TABLE_REGISTER :
> > + AUDIT_NFT_OP_TABLE_UNREGISTER);
> > + kfree(buf);
>
> As a follow up: Would you wrap this code into a function?
>
> nft_table_audit()
>
> Same thing for other pieces of code below.

If I'm guessing right, you are asking for a supplementary follow-up
cleanup patch to this one (or are you nacking this patch)?

Also, I gather you would like to see the kasprintf and kfree hidden in
nft_table_audit(), handing this function at least 8 parameters? This
sounds pretty messy given the format of the table field.

> Thanks.

- RGB

--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635