Re: [PATCH ghak90 V6 05/10] audit: add contid support for signalling the audit daemon

Ondrej Mosnacek
2019-04-09T12:57:50Z

On Tue, Apr 9, 2019 at 5:40 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> Add audit container identifier support to the action of signalling the
> audit daemon.
>
> Since this would need to add an element to the audit_sig_info struct,
> a new record type AUDIT_SIGNAL_INFO2 was created with a new
> audit_sig_info2 struct. Corresponding support is required in the
> userspace code to reflect the new record request and reply type.
> An older userspace won't break since it won't know to request this
> record type.
>
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>

This looks good to me.

Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>

Although I'm wondering if we shouldn't try to future-proof the
AUDIT_SIGNAL_INFO2 format somehow, so that we don't need to add
another AUDIT_SIGNAL_INFO3 when the need arises to add yet-another
identifier to it... The simplest solution I can come up with is to add
a "version" field at the beginning (set to 2 initially), then v<N>_len
at the beginning of data for version <N>. But maybe this is too
complicated for too little gain...

> ---
> include/linux/audit.h | 7 +++++++
> include/uapi/linux/audit.h | 1 +
> kernel/audit.c | 27 +++++++++++++++++++++++++++
> kernel/audit.h | 1 +
> kernel/auditsc.c | 1 +
> security/selinux/nlmsgtab.c | 1 +
> 6 files changed, 38 insertions(+)
>
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 43438192ca2a..c2dec9157463 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -37,6 +37,13 @@ struct audit_sig_info {
> char ctx[0];
> };
>
> +struct audit_sig_info2 {
> + uid_t uid;
> + pid_t pid;
> + u64 cid;
> + char ctx[0];
> +};
> +
> struct audit_buffer;
> struct audit_context;
> struct inode;
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 55fde9970762..10cc67926cf1 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -72,6 +72,7 @@
> #define AUDIT_SET_FEATURE 1018 /* Turn an audit feature on or off */
> #define AUDIT_GET_FEATURE 1019 /* Get which features are enabled */
> #define AUDIT_CONTAINER_OP 1020 /* Define the container id and info */
> +#define AUDIT_SIGNAL_INFO2 1021 /* Get info auditd signal sender */
>
> #define AUDIT_FIRST_USER_MSG 1100 /* Userspace messages mostly uninteresting to kernel */
> #define AUDIT_USER_AVC 1107 /* We filter this differently */
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 3e0af53f3c4d..87e1d367f98c 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -138,6 +138,7 @@ struct audit_net {
> kuid_t audit_sig_uid = INVALID_UID;
> pid_t audit_sig_pid = -1;
> u32 audit_sig_sid = 0;
> +u64 audit_sig_cid = AUDIT_CID_UNSET;
>
> /* Records can be lost in several ways:
> 0) [suppressed in audit_alloc]
> @@ -1097,6 +1098,7 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
> case AUDIT_ADD_RULE:
> case AUDIT_DEL_RULE:
> case AUDIT_SIGNAL_INFO:
> + case AUDIT_SIGNAL_INFO2:
> case AUDIT_TTY_GET:
> case AUDIT_TTY_SET:
> case AUDIT_TRIM:
> @@ -1260,6 +1262,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> struct audit_buffer *ab;
> u16 msg_type = nlh->nlmsg_type;
> struct audit_sig_info *sig_data;
> + struct audit_sig_info2 *sig_data2;
> char *ctx = NULL;
> u32 len;
>
> @@ -1519,6 +1522,30 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> sig_data, sizeof(*sig_data) + len);
> kfree(sig_data);
> break;
> + case AUDIT_SIGNAL_INFO2:
> + len = 0;
> + if (audit_sig_sid) {
> + err = security_secid_to_secctx(audit_sig_sid, &ctx, &len);
> + if (err)
> + return err;
> + }
> + sig_data2 = kmalloc(sizeof(*sig_data2) + len, GFP_KERNEL);
> + if (!sig_data2) {
> + if (audit_sig_sid)
> + security_release_secctx(ctx, len);
> + return -ENOMEM;
> + }
> + sig_data2->uid = from_kuid(&init_user_ns, audit_sig_uid);
> + sig_data2->pid = audit_sig_pid;
> + if (audit_sig_sid) {
> + memcpy(sig_data2->ctx, ctx, len);
> + security_release_secctx(ctx, len);
> + }
> + sig_data2->cid = audit_sig_cid;
> + audit_send_reply(skb, seq, AUDIT_SIGNAL_INFO2, 0, 0,
> + sig_data2, sizeof(*sig_data2) + len);
> + kfree(sig_data2);
> + break;
> case AUDIT_TTY_GET: {
> struct audit_tty_status s;
> unsigned int t;
> diff --git a/kernel/audit.h b/kernel/audit.h
> index e2912924af0d..c5ac6436317e 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -345,6 +345,7 @@ extern void audit_filter_inodes(struct task_struct *tsk,
> extern pid_t audit_sig_pid;
> extern kuid_t audit_sig_uid;
> extern u32 audit_sig_sid;
> +extern u64 audit_sig_cid;
>
> extern int audit_filter(int msgtype, unsigned int listtype);
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index eea445b7a181..0a29a00feaf1 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2405,6 +2405,7 @@ int audit_signal_info(int sig, struct task_struct *t)
> else
> audit_sig_uid = uid;
> security_task_getsecid(current, &audit_sig_sid);
> + audit_sig_cid = audit_get_contid(current);
> }
>
> if (!audit_signals || audit_dummy_context())
> diff --git a/security/selinux/nlmsgtab.c b/security/selinux/nlmsgtab.c
> index 9cec81209617..682fe7397762 100644
> --- a/security/selinux/nlmsgtab.c
> +++ b/security/selinux/nlmsgtab.c
> @@ -132,6 +132,7 @@ struct nlmsg_perm {
> { AUDIT_DEL_RULE, NETLINK_AUDIT_SOCKET__NLMSG_WRITE },
> { AUDIT_USER, NETLINK_AUDIT_SOCKET__NLMSG_RELAY },
> { AUDIT_SIGNAL_INFO, NETLINK_AUDIT_SOCKET__NLMSG_READ },
> + { AUDIT_SIGNAL_INFO2, NETLINK_AUDIT_SOCKET__NLMSG_READ },
> { AUDIT_TRIM, NETLINK_AUDIT_SOCKET__NLMSG_WRITE },
> { AUDIT_MAKE_EQUIV, NETLINK_AUDIT_SOCKET__NLMSG_WRITE },
> { AUDIT_TTY_GET, NETLINK_AUDIT_SOCKET__NLMSG_READ },
> --
> 1.8.3.1
>

--
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.