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

[Steve Grubb <sgrubb@redhat.com>]

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@redhat.com>
> ---
> 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.

-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;