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

From: Richard Guy Briggs
Date: Thu Jun 04 2020 - 13:58:17 EST

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On 2020-06-04 13:03, Steve Grubb wrote:
> On Thursday, June 4, 2020 9:20:49 AM EDT 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"
> },
> > };
>
> I still don't like the event format because it doesn't give complete subject
> information. However, I thought I'd comment on this string table. Usually
> it's sufficient to log the number and then have the string table in user space
> which looks it up during interpretation.

That is a good idea that would help reduce kernel cycles and netlink
bandwidth, but the format was set in 2011 so it is a bit late to change
that now:
fbabf31e4d48 ("netfilter: create audit records for x_tables replaces")

> -Steve
>
> > 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);
> >
> > if (!ctx->report &&
> > !nfnetlink_has_listeners(ctx->net, NFNLGRP_NFTABLES))
> > @@ -1428,6 +1439,17 @@ static void nf_tables_chain_notify(const struct
> > nft_ctx *ctx, int event) {
> > struct sk_buff *skb;
> > int err;
> > + char *buf = kasprintf(GFP_KERNEL, "%s:%llu;%s:%llu",
> > + ctx->table->name, ctx->table->handle,
> > + ctx->chain->name, ctx->chain->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + ctx->family,
> > + ctx->chain->use,
> > + event == NFT_MSG_NEWCHAIN ?
> > + AUDIT_NFT_OP_CHAIN_REGISTER :
> > + AUDIT_NFT_OP_CHAIN_UNREGISTER);
> > + kfree(buf);
> >
> > if (!ctx->report &&
> > !nfnetlink_has_listeners(ctx->net, NFNLGRP_NFTABLES))
> > @@ -2691,6 +2713,17 @@ static void nf_tables_rule_notify(const struct
> > nft_ctx *ctx, {
> > struct sk_buff *skb;
> > int err;
> > + char *buf = kasprintf(GFP_KERNEL, "%s:%llu;%s:%llu",
> > + ctx->table->name, ctx->table->handle,
> > + ctx->chain->name, ctx->chain->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + ctx->family,
> > + rule->handle,
> > + event == NFT_MSG_NEWRULE ?
> > + AUDIT_NFT_OP_RULE_REGISTER :
> > + AUDIT_NFT_OP_RULE_UNREGISTER);
> > + kfree(buf);
> >
> > if (!ctx->report &&
> > !nfnetlink_has_listeners(ctx->net, NFNLGRP_NFTABLES))
> > @@ -3693,6 +3726,17 @@ static void nf_tables_set_notify(const struct
> > nft_ctx *ctx, struct sk_buff *skb;
> > u32 portid = ctx->portid;
> > int err;
> > + char *buf = kasprintf(gfp_flags, "%s:%llu;%s:%llu",
> > + ctx->table->name, ctx->table->handle,
> > + set->name, set->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + ctx->family,
> > + set->field_count,
> > + event == NFT_MSG_NEWSET ?
> > + AUDIT_NFT_OP_SET_REGISTER :
> > + AUDIT_NFT_OP_SET_UNREGISTER);
> > + kfree(buf);
> >
> > if (!ctx->report &&
> > !nfnetlink_has_listeners(ctx->net, NFNLGRP_NFTABLES))
> > @@ -4809,6 +4853,17 @@ static void nf_tables_setelem_notify(const struct
> > nft_ctx *ctx, u32 portid = ctx->portid;
> > struct sk_buff *skb;
> > int err;
> > + char *buf = kasprintf(GFP_KERNEL, "%s:%llu;%s:%llu",
> > + ctx->table->name, ctx->table->handle,
> > + set->name, set->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + ctx->family,
> > + set->handle,
> > + event == NFT_MSG_NEWSETELEM ?
> > + AUDIT_NFT_OP_SETELEM_REGISTER :
> > + AUDIT_NFT_OP_SETELEM_UNREGISTER);
> > + kfree(buf);
> >
> > if (!ctx->report && !nfnetlink_has_listeners(net, NFNLGRP_NFTABLES))
> > return;
> > @@ -5890,6 +5945,19 @@ static int nf_tables_dump_obj(struct sk_buff *skb,
> > struct netlink_callback *cb) obj->ops->type->type != filter->type)
> > goto cont;
> >
> > + if (reset) {
> > + char *buf = kasprintf(GFP_KERNEL,
> > + "%s:%llu;?:0",
> > + table->name,
> > + table->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + family,
> > + obj->handle,
> > + AUDIT_NFT_OP_OBJ_RESET);
> > + kfree(buf);
> > + }
> > +
> > if (nf_tables_fill_obj_info(skb, net, NETLINK_CB(cb-
> >skb).portid,
> > cb->nlh->nlmsg_seq,
> > NFT_MSG_NEWOBJ,
> > @@ -6000,6 +6068,17 @@ static int nf_tables_getobj(struct net *net, struct
> > sock *nlsk, if (NFNL_MSG_TYPE(nlh->nlmsg_type) == NFT_MSG_GETOBJ_RESET)
> > reset = true;
> >
> > + if (reset) {
> > + char *buf = kasprintf(GFP_KERNEL, "%s:%llu;?:0",
> > + table->name, table->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + family,
> > + obj->handle,
> > + AUDIT_NFT_OP_OBJ_RESET);
> > + kfree(buf);
> > + }
> > +
> > err = nf_tables_fill_obj_info(skb2, net, NETLINK_CB(skb).portid,
> > nlh->nlmsg_seq, NFT_MSG_NEWOBJ, 0,
> > family, table, obj, reset);
> > @@ -6075,6 +6154,16 @@ void nft_obj_notify(struct net *net, const struct
> > nft_table *table, {
> > struct sk_buff *skb;
> > int err;
> > + char *buf = kasprintf(GFP_KERNEL, "%s:%llu;?:0",
> > + table->name, table->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + family,
> > + obj->handle,
> > + event == NFT_MSG_NEWOBJ ?
> > + AUDIT_NFT_OP_OBJ_REGISTER :
> > + AUDIT_NFT_OP_OBJ_UNREGISTER);
> > + kfree(buf);
> >
> > if (!report &&
> > !nfnetlink_has_listeners(net, NFNLGRP_NFTABLES))
> > @@ -6701,6 +6790,17 @@ static void nf_tables_flowtable_notify(struct
> > nft_ctx *ctx, {
> > struct sk_buff *skb;
> > int err;
> > + char *buf = kasprintf(GFP_KERNEL, "%s:%llu;%s:%llu",
> > + flowtable->table->name, flowtable->table->handle,
> > + flowtable->name, flowtable->handle);
> > +
> > + audit_log_nfcfg(buf,
> > + ctx->family,
> > + flowtable->hooknum,
> > + event == NFT_MSG_NEWFLOWTABLE ?
> > + AUDIT_NFT_OP_FLOWTABLE_REGISTER :
> > + AUDIT_NFT_OP_FLOWTABLE_UNREGISTER);
> > + kfree(buf);
> >
> > if (ctx->report &&
> > !nfnetlink_has_listeners(ctx->net, NFNLGRP_NFTABLES))
> > @@ -6822,6 +6922,9 @@ static void nf_tables_gen_notify(struct net *net,
> > struct sk_buff *skb, struct sk_buff *skb2;
> > int err;
> >
> > + audit_log_nfcfg("?:0;?:0", 0, net->nft.base_seq,
> > + AUDIT_NFT_OP_GEN_REGISTER);
> > +
> > if (nlmsg_report(nlh) &&
> > !nfnetlink_has_listeners(net, NFNLGRP_NFTABLES))
> > return;
>
>
>
>

- 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

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In reply to: Steve Grubb: "Re: [PATCH ghak124 v3] audit: log nftables configuration change events"
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