Re: [PATCH 1/2] security/smack implement logging V3

[Casey Schaufler <casey@schaufler-ca.com>]

Etienne Basset wrote:
> This patch creates auditing functions usable by LSM to audit security
> events. It provides standard dumping of FS, NET, task etc ... events
> (code borrowed from SELinux)
> and provides 2 callbacks to define LSM specific auditing, which should be 
> flexible enough to convert SELinux too.
>
> Signed-off-by: Etienne Basset <etienne.basset@numericable.fr>
>   

Acked-by: Casey Schaufler <casey@schaufler-ca.com>

My tests are passing. I am not explicitly testing audit.

> ---
>  include/linux/lsm_audit.h |  111 +++++++++++++
>  security/lsm_audit.c      |  386 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 497 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
> new file mode 100644
> index 0000000..e461b2c
> --- /dev/null
> +++ b/include/linux/lsm_audit.h
> @@ -0,0 +1,111 @@
> +/*
> + * Common LSM logging functions
> + * Heavily borrowed from selinux/avc.h
> + *
> + * Author : Etienne BASSET  <etienne.basset@ensta.org>
> + *
> + * All credits to : Stephen Smalley, <sds@epoch.ncsc.mil>
> + * All BUGS to : Etienne BASSET  <etienne.basset@ensta.org>
> + */
> +#ifndef _LSM_COMMON_LOGGING_
> +#define _LSM_COMMON_LOGGING_
> +
> +#include <linux/stddef.h>
> +#include <linux/errno.h>
> +#include <linux/kernel.h>
> +#include <linux/kdev_t.h>
> +#include <linux/spinlock.h>
> +#include <linux/init.h>
> +#include <linux/audit.h>
> +#include <linux/in6.h>
> +#include <linux/path.h>
> +#include <linux/key.h>
> +#include <linux/skbuff.h>
> +#include <asm/system.h>
> +
> +
> +/* Auxiliary data to use in generating the audit record. */
> +struct common_audit_data {
> +	char    type;
> +#define LSM_AUDIT_DATA_FS      1
> +#define LSM_AUDIT_DATA_NET     2
> +#define LSM_AUDIT_DATA_CAP     3
> +#define LSM_AUDIT_DATA_IPC     4
> +#define LSM_AUDIT_DATA_TASK    5
> +#define LSM_AUDIT_DATA_KEY     6
> +	struct task_struct *tsk;
> +	union 	{
> +		struct {
> +			struct path path;
> +			struct inode *inode;
> +		} fs;
> +		struct {
> +			int netif;
> +			struct sock *sk;
> +			u16 family;
> +			__be16 dport;
> +			__be16 sport;
> +			union {
> +				struct {
> +					__be32 daddr;
> +					__be32 saddr;
> +				} v4;
> +				struct {
> +					struct in6_addr daddr;
> +					struct in6_addr saddr;
> +				} v6;
> +			} fam;
> +		} net;
> +		int cap;
> +		int ipc_id;
> +		struct task_struct *tsk;
> +#ifdef CONFIG_KEYS
> +		struct {
> +			key_serial_t key;
> +			char *key_desc;
> +		} key_struct;
> +#endif
> +	} u;
> +	const char *function;
> +	/* this union contains LSM specific data */
> +	union {
> +		/* SMACK data */
> +		struct smack_audit_data {
> +			char *subject;
> +			char *object;
> +			char *request;
> +			int result;
> +		} smack_audit_data;
> +		/* SELinux data */
> +		struct {
> +			u32 ssid;
> +			u32 tsid;
> +			u16 tclass;
> +			u32 requested;
> +			u32 audited;
> +			struct av_decision *avd;
> +			int result;
> +		} selinux_audit_data;
> +	} lsm_priv;
> +	/* these callback will be implemented by a specific LSM */
> +	void (*lsm_pre_audit)(struct audit_buffer *, void *);
> +	void (*lsm_post_audit)(struct audit_buffer *, void *);
> +};
> +
> +#define v4info fam.v4
> +#define v6info fam.v6
> +
> +int ipv4_skb_to_auditdata(struct sk_buff *skb,
> +		struct common_audit_data *ad, u8 *proto);
> +
> +int ipv6_skb_to_auditdata(struct sk_buff *skb,
> +		struct common_audit_data *ad, u8 *proto);
> +
> +/* Initialize an LSM audit data structure. */
> +#define COMMON_AUDIT_DATA_INIT(_d, _t) \
> +	{ memset((_d), 0, sizeof(struct common_audit_data)); \
> +	 (_d)->type = LSM_AUDIT_DATA_##_t; (_d)->function = __func__; }
> +
> +void common_lsm_audit(struct common_audit_data *a);
> +
> +#endif
> diff --git a/security/lsm_audit.c b/security/lsm_audit.c
> new file mode 100644
> index 0000000..b47a933
> --- /dev/null
> +++ b/security/lsm_audit.c
> @@ -0,0 +1,386 @@
> +/*
> + * common LSM auditing functions
> + *
> + * Based on code written for SELinux by :
> + *			Stephen Smalley, <sds@epoch.ncsc.mil>
> + * 			James Morris <jmorris@redhat.com>
> + * Author : Etienne Basset, <etienne.basset@ensta.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2,
> + * as published by the Free Software Foundation.
> + */
> +
> +#include <linux/types.h>
> +#include <linux/stddef.h>
> +#include <linux/kernel.h>
> +#include <linux/fs.h>
> +#include <linux/init.h>
> +#include <net/sock.h>
> +#include <linux/un.h>
> +#include <net/af_unix.h>
> +#include <linux/audit.h>
> +#include <linux/ipv6.h>
> +#include <linux/ip.h>
> +#include <net/ip.h>
> +#include <net/ipv6.h>
> +#include <linux/tcp.h>
> +#include <linux/udp.h>
> +#include <linux/dccp.h>
> +#include <linux/sctp.h>
> +#include <linux/lsm_audit.h>
> +
> +/**
> + * ipv4_skb_to_auditdata : fill auditdata from skb
> + * @skb : the skb
> + * @ad : the audit data to fill
> + * @proto : the layer 4 protocol
> + *
> + * return  0 on success
> + */
> +int ipv4_skb_to_auditdata(struct sk_buff *skb,
> +		struct common_audit_data *ad, u8 *proto)
> +{
> +	int ret = 0;
> +	struct iphdr *ih;
> +
> +	ih = ip_hdr(skb);
> +	if (ih == NULL)
> +		return -EINVAL;
> +
> +	ad->u.net.v4info.saddr = ih->saddr;
> +	ad->u.net.v4info.daddr = ih->daddr;
> +
> +	if (proto)
> +		*proto = ih->protocol;
> +	/* non initial fragment */
> +	if (ntohs(ih->frag_off) & IP_OFFSET)
> +		return 0;
> +
> +	switch (ih->protocol) {
> +	case IPPROTO_TCP: {
> +		struct tcphdr *th = tcp_hdr(skb);
> +		if (th == NULL)
> +			break;
> +
> +		ad->u.net.sport = th->source;
> +		ad->u.net.dport = th->dest;
> +		break;
> +	}
> +	case IPPROTO_UDP: {
> +		struct udphdr *uh = udp_hdr(skb);
> +		if (uh == NULL)
> +			break;
> +
> +		ad->u.net.sport = uh->source;
> +		ad->u.net.dport = uh->dest;
> +		break;
> +	}
> +	case IPPROTO_DCCP: {
> +		struct dccp_hdr *dh = dccp_hdr(skb);
> +		if (dh == NULL)
> +			break;
> +
> +		ad->u.net.sport = dh->dccph_sport;
> +		ad->u.net.dport = dh->dccph_dport;
> +		break;
> +	}
> +	case IPPROTO_SCTP: {
> +		struct sctphdr *sh = sctp_hdr(skb);
> +		if (sh == NULL)
> +			break;
> +		ad->u.net.sport = sh->source;
> +		ad->u.net.dport = sh->dest;
> +		break;
> +	}
> +	default:
> +		ret = -EINVAL;
> +	}
> +	return ret;
> +}
> +#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
> +/**
> + * ipv6_skb_to_auditdata : fill auditdata from skb
> + * @skb : the skb
> + * @ad : the audit data to fill
> + * @proto : the layer 4 protocol
> + *
> + * return  0 on success
> + */
> +int ipv6_skb_to_auditdata(struct sk_buff *skb,
> +		struct common_audit_data *ad, u8 *proto)
> +{
> +	int offset, ret = 0;
> +	struct ipv6hdr *ip6;
> +	u8 nexthdr;
> +
> +	ip6 = ipv6_hdr(skb);
> +	if (ip6 == NULL)
> +		return -EINVAL;
> +	ipv6_addr_copy(&ad->u.net.v6info.saddr, &ip6->saddr);
> +	ipv6_addr_copy(&ad->u.net.v6info.daddr, &ip6->daddr);
> +	ret = 0;
> +	/* IPv6 can have several extension header before the Transport header
> +	 * skip them */
> +	offset = skb_network_offset(skb);
> +	offset += sizeof(*ip6);
> +	nexthdr = ip6->nexthdr;
> +	offset = ipv6_skip_exthdr(skb, offset, &nexthdr);
> +	if (offset < 0)
> +		return 0;
> +	if (proto)
> +		*proto = nexthdr;
> +	switch (nexthdr) {
> +	case IPPROTO_TCP: {
> +		struct tcphdr _tcph, *th;
> +
> +		th = skb_header_pointer(skb, offset, sizeof(_tcph), &_tcph);
> +		if (th == NULL)
> +			break;
> +
> +		ad->u.net.sport = th->source;
> +		ad->u.net.dport = th->dest;
> +		break;
> +	}
> +	case IPPROTO_UDP: {
> +		struct udphdr _udph, *uh;
> +
> +		uh = skb_header_pointer(skb, offset, sizeof(_udph), &_udph);
> +		if (uh == NULL)
> +			break;
> +
> +		ad->u.net.sport = uh->source;
> +		ad->u.net.dport = uh->dest;
> +		break;
> +	}
> +	case IPPROTO_DCCP: {
> +		struct dccp_hdr _dccph, *dh;
> +
> +		dh = skb_header_pointer(skb, offset, sizeof(_dccph), &_dccph);
> +		if (dh == NULL)
> +			break;
> +
> +		ad->u.net.sport = dh->dccph_sport;
> +		ad->u.net.dport = dh->dccph_dport;
> +		break;
> +	}
> +	case IPPROTO_SCTP: {
> +		struct sctphdr _sctph, *sh;
> +
> +		sh = skb_header_pointer(skb, offset, sizeof(_sctph), &_sctph);
> +		if (sh == NULL)
> +			break;
> +		ad->u.net.sport = sh->source;
> +		ad->u.net.dport = sh->dest;
> +		break;
> +	}
> +	default:
> +		ret = -EINVAL;
> +	}
> +	return ret;
> +}
> +#endif
> +
> +
> +static inline void print_ipv6_addr(struct audit_buffer *ab,
> +				   struct in6_addr *addr, __be16 port,
> +				   char *name1, char *name2)
> +{
> +	if (!ipv6_addr_any(addr))
> +		audit_log_format(ab, " %s=%pI6", name1, addr);
> +	if (port)
> +		audit_log_format(ab, " %s=%d", name2, ntohs(port));
> +}
> +
> +static inline void print_ipv4_addr(struct audit_buffer *ab, __be32 addr,
> +				   __be16 port, char *name1, char *name2)
> +{
> +	if (addr)
> +		audit_log_format(ab, " %s=%pI4", name1, &addr);
> +	if (port)
> +		audit_log_format(ab, " %s=%d", name2, ntohs(port));
> +}
> +
> +/**
> + * dump_common_audit_data - helper to dump common audit data
> + * @a : common audit data
> + *
> + */
> +static void dump_common_audit_data(struct audit_buffer *ab,
> +				   struct common_audit_data *a)
> +{
> +	struct inode *inode = NULL;
> +	struct task_struct *tsk = current;
> +
> +	if (a->tsk)
> +		tsk = a->tsk;
> +	if (tsk && tsk->pid) {
> +		audit_log_format(ab, " pid=%d comm=", tsk->pid);
> +		audit_log_untrustedstring(ab, tsk->comm);
> +	}
> +	
> +	switch (a->type) {
> +	case LSM_AUDIT_DATA_IPC:
> +		audit_log_format(ab, " key=%d ", a->u.ipc_id);
> +		break;
> +	case LSM_AUDIT_DATA_CAP:
> +		audit_log_format(ab, " capability=%d ", a->u.cap);
> +		break;
> +	case LSM_AUDIT_DATA_FS:
> +		if (a->u.fs.path.dentry) {
> +			struct dentry *dentry = a->u.fs.path.dentry;
> +			if (a->u.fs.path.mnt) {
> +				audit_log_d_path(ab, "path=", &a->u.fs.path);
> +			} else {
> +				audit_log_format(ab, " name=");
> +				audit_log_untrustedstring(ab,
> +						 dentry->d_name.name);
> +			}
> +			inode = dentry->d_inode;
> +		} else if (a->u.fs.inode) {
> +			struct dentry *dentry;
> +			inode = a->u.fs.inode;
> +			dentry = d_find_alias(inode);
> +			if (dentry) {
> +				audit_log_format(ab, " name=");
> +				audit_log_untrustedstring(ab,
> +						 dentry->d_name.name);
> +				dput(dentry);
> +			}
> +		}
> +		if (inode)
> +			audit_log_format(ab, " dev=%s ino=%lu",
> +					inode->i_sb->s_id,
> +					inode->i_ino);
> +		break;
> +	case LSM_AUDIT_DATA_TASK:
> +		tsk = a->u.tsk;
> +		if (tsk && tsk->pid) {
> +			audit_log_format(ab, " pid=%d comm=", tsk->pid);
> +			audit_log_untrustedstring(ab, tsk->comm);
> +		}
> +		break;
> +	case LSM_AUDIT_DATA_NET:
> +		if (a->u.net.sk) {
> +			struct sock *sk = a->u.net.sk;
> +			struct unix_sock *u;
> +			int len = 0;
> +			char *p = NULL;
> +
> +			switch (sk->sk_family) {
> +			case AF_INET: {
> +				struct inet_sock *inet = inet_sk(sk);
> +
> +				print_ipv4_addr(ab, inet->rcv_saddr,
> +						inet->sport,
> +						"laddr", "lport");
> +				print_ipv4_addr(ab, inet->daddr,
> +						inet->dport,
> +						"faddr", "fport");
> +				break;
> +			}
> +			case AF_INET6: {
> +				struct inet_sock *inet = inet_sk(sk);
> +				struct ipv6_pinfo *inet6 = inet6_sk(sk);
> +
> +				print_ipv6_addr(ab, &inet6->rcv_saddr,
> +						inet->sport,
> +						"laddr", "lport");
> +				print_ipv6_addr(ab, &inet6->daddr,
> +						inet->dport,
> +						"faddr", "fport");
> +				break;
> +			}
> +			case AF_UNIX:
> +				u = unix_sk(sk);
> +				if (u->dentry) {
> +					struct path path = {
> +						.dentry = u->dentry,
> +						.mnt = u->mnt
> +					};
> +					audit_log_d_path(ab, "path=", &path);
> +					break;
> +				}
> +				if (!u->addr)
> +					break;
> +				len = u->addr->len-sizeof(short);
> +				p = &u->addr->name->sun_path[0];
> +				audit_log_format(ab, " path=");
> +				if (*p)
> +					audit_log_untrustedstring(ab, p);
> +				else
> +					audit_log_n_hex(ab, p, len);
> +				break;
> +			}
> +		}
> +
> +		switch (a->u.net.family) {
> +		case AF_INET:
> +			print_ipv4_addr(ab, a->u.net.v4info.saddr,
> +					a->u.net.sport,
> +					"saddr", "src");
> +			print_ipv4_addr(ab, a->u.net.v4info.daddr,
> +					a->u.net.dport,
> +					"daddr", "dest");
> +			break;
> +		case AF_INET6:
> +			print_ipv6_addr(ab, &a->u.net.v6info.saddr,
> +					a->u.net.sport,
> +					"saddr", "src");
> +			print_ipv6_addr(ab, &a->u.net.v6info.daddr,
> +					a->u.net.dport,
> +					"daddr", "dest");
> +			break;
> +		}
> +		if (a->u.net.netif > 0) {
> +			struct net_device *dev;
> +
> +			/* NOTE: we always use init's namespace */
> +			dev = dev_get_by_index(&init_net, a->u.net.netif);
> +			if (dev) {
> +				audit_log_format(ab, " netif=%s", dev->name);
> +				dev_put(dev);
> +			}
> +		}
> +		break;
> +#ifdef CONFIG_KEYS
> +	case LSM_AUDIT_DATA_KEY:
> +		audit_log_format(ab, " key_serial=%u", a->u.key_struct.key);
> +		if (a->u.key_struct.key_desc) {
> +			audit_log_format(ab, " key_desc=");
> +			audit_log_untrustedstring(ab, a->u.key_struct.key_desc);
> +		}
> +		break;
> +#endif
> +	} /* switch (a->type) */
> +}
> +
> +/**
> + * common_lsm_audit - generic LSM auditing function
> + * @a:  auxiliary audit data
> + *
> + * setup the audit buffer for common security information
> + * uses callback to print LSM specific information
> + */
> +void common_lsm_audit(struct common_audit_data *a)
> +{
> +	struct audit_buffer *ab;
> +
> +	if (a == NULL)
> +		return;
> +	/* we use GFP_ATOMIC so we won't sleep */
> +	ab = audit_log_start(current->audit_context, GFP_ATOMIC, AUDIT_AVC);
> +
> +	if (ab == NULL)
> +		return;
> +
> +	if (a->lsm_pre_audit)
> +		a->lsm_pre_audit(ab, a);
> +
> +	dump_common_audit_data(ab, a);
> +
> +	if (a->lsm_post_audit)
> +		a->lsm_post_audit(ab, a);
> +
> +	audit_log_end(ab);
> +}
>
>
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