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Message-ID: <f2186f22-5bcd-d962-7e49-c816fc5fbd07@canonical.com>
Date: Mon, 25 Apr 2022 20:37:54 -0700
From: John Johansen <john.johansen@...onical.com>
To: Casey Schaufler <casey@...aufler-ca.com>,
casey.schaufler@...el.com, jmorris@...ei.org,
linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Cc: linux-audit@...hat.com, keescook@...omium.org,
penguin-kernel@...ove.sakura.ne.jp, paul@...l-moore.com,
stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v35 27/29] Audit: Add record for multiple object contexts
On 4/18/22 07:59, Casey Schaufler wrote:
> Create a new audit record AUDIT_MAC_OBJ_CONTEXTS.
> An example of the MAC_OBJ_CONTEXTS (1421) record is:
>
> type=MAC_OBJ_CONTEXTS[1421]
> msg=audit(1601152467.009:1050):
> obj_selinux=unconfined_u:object_r:user_home_t:s0
>
> When an audit event includes a AUDIT_MAC_OBJ_CONTEXTS record
> the "obj=" field in other records in the event will be "obj=?".
> An AUDIT_MAC_OBJ_CONTEXTS record is supplied when the system has
> multiple security modules that may make access decisions based
> on an object security context.
>
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> ---
> include/linux/audit.h | 5 +++
> include/uapi/linux/audit.h | 1 +
> kernel/audit.c | 47 +++++++++++++++++++++++
> kernel/auditsc.c | 79 ++++++++++++--------------------------
> 4 files changed, 77 insertions(+), 55 deletions(-)
>
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 14849d5f84b4..1b05eb2dbe77 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -191,6 +191,8 @@ extern void audit_log_path_denied(int type,
> const char *operation);
> extern void audit_log_lost(const char *message);
>
> +extern void audit_log_object_context(struct audit_buffer *ab,
> + struct lsmblob *blob);
> extern int audit_log_task_context(struct audit_buffer *ab);
> extern void audit_log_task_info(struct audit_buffer *ab);
>
> @@ -251,6 +253,9 @@ static inline void audit_log_key(struct audit_buffer *ab, char *key)
> { }
> static inline void audit_log_path_denied(int type, const char *operation)
> { }
> +static inline void audit_log_object_context(struct audit_buffer *ab,
> + struct lsmblob *blob)
> +{ }
> static inline int audit_log_task_context(struct audit_buffer *ab)
> {
> return 0;
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index af0aaccfaf57..d25d76b29e3c 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -144,6 +144,7 @@
> #define AUDIT_MAC_CALIPSO_ADD 1418 /* NetLabel: add CALIPSO DOI entry */
> #define AUDIT_MAC_CALIPSO_DEL 1419 /* NetLabel: del CALIPSO DOI entry */
> #define AUDIT_MAC_TASK_CONTEXTS 1420 /* Multiple LSM task contexts */
> +#define AUDIT_MAC_OBJ_CONTEXTS 1421 /* Multiple LSM objext contexts */
>
> #define AUDIT_FIRST_KERN_ANOM_MSG 1700
> #define AUDIT_LAST_KERN_ANOM_MSG 1799
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 8ed2d717c217..a8c3ec6ba60b 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -2226,6 +2226,53 @@ static void audit_buffer_aux_end(struct audit_buffer *ab)
> ab->skb = skb_peek(&ab->skb_list);
> }
>
> +void audit_log_object_context(struct audit_buffer *ab, struct lsmblob *blob)
> +{
> + int i;
> + int error;
> + struct lsmcontext context;
> +
> + if (!lsm_multiple_contexts()) {
> + error = security_secid_to_secctx(blob, &context, LSMBLOB_FIRST);
> + if (error) {
> + if (error != -EINVAL)
> + goto error_path;
> + return;
> + }
> + audit_log_format(ab, " obj=%s", context.context);
> + security_release_secctx(&context);
> + } else {
> + audit_log_format(ab, " obj=?");
> + error = audit_buffer_aux_new(ab, AUDIT_MAC_OBJ_CONTEXTS);
> + if (error)
> + goto error_path;
> +
> + for (i = 0; i < LSMBLOB_ENTRIES; i++) {
> + if (blob->secid[i] == 0)
> + continue;
> + error = security_secid_to_secctx(blob, &context, i);
> + if (error) {
> + audit_log_format(ab, "%sobj_%s=?",
> + i ? " " : "",
> + lsm_slot_to_name(i));
> + if (error != -EINVAL)
> + audit_panic("error in audit_log_object_context");
> + } else {
> + audit_log_format(ab, "%sobj_%s=%s",
> + i ? " " : "",
> + lsm_slot_to_name(i),
> + context.context);
> + security_release_secctx(&context);
> + }
> + }
> +
> + audit_buffer_aux_end(ab);
> + }
> + return;
> +
> +error_path:
> + audit_panic("error in audit_log_object_context");
This moves the audit_panic around, so certain operations are not
done before the call. I am currently not sure of the implications.
Paul?
> +}
>
> int audit_log_task_context(struct audit_buffer *ab)
> {
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 557713954a69..04bf3c04ef3d 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -1114,36 +1114,25 @@ static inline void audit_free_context(struct audit_context *context)
> kfree(context);
> }
>
> -static int audit_log_pid_context(struct audit_context *context, pid_t pid,
> - kuid_t auid, kuid_t uid,
> - unsigned int sessionid,
> - struct lsmblob *blob, char *comm)
> +static void audit_log_pid_context(struct audit_context *context, pid_t pid,
> + kuid_t auid, kuid_t uid,
> + unsigned int sessionid,
> + struct lsmblob *blob, char *comm)
> {
> struct audit_buffer *ab;
> - struct lsmcontext lsmctx;
> - int rc = 0;
>
> ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
> if (!ab)
> - return rc;
> + return;
>
> audit_log_format(ab, "opid=%d oauid=%d ouid=%d oses=%d", pid,
> from_kuid(&init_user_ns, auid),
> from_kuid(&init_user_ns, uid), sessionid);
> - if (lsmblob_is_set(blob)) {
> - if (security_secid_to_secctx(blob, &lsmctx, LSMBLOB_FIRST)) {
> - audit_log_format(ab, " obj=(none)");
> - rc = 1;
> - } else {
> - audit_log_format(ab, " obj=%s", lsmctx.context);
> - security_release_secctx(&lsmctx);
> - }
> - }
> + if (lsmblob_is_set(blob))
> + audit_log_object_context(ab, blob);
> audit_log_format(ab, " ocomm=");
> audit_log_untrustedstring(ab, comm);
> audit_log_end(ab);
> -
> - return rc;
> }
>
> static void audit_log_execve_info(struct audit_context *context,
> @@ -1420,18 +1409,10 @@ static void show_special(struct audit_context *context, int *call_panic)
If pushing audit_panic into audit_log_object_context() is acceptable then this call_panic arg is
no longer needed. The same goes for the call_panic arg in audit_log_name(). And call_panic can
be dropped from audit_log_exit()
> from_kgid(&init_user_ns, context->ipc.gid),
> context->ipc.mode);
> if (osid) {
> - struct lsmcontext lsmcxt;
> struct lsmblob blob;
>
> lsmblob_init(&blob, osid);
> - if (security_secid_to_secctx(&blob, &lsmcxt,
> - LSMBLOB_FIRST)) {
> - audit_log_format(ab, " osid=%u", osid);
> - *call_panic = 1;
> - } else {
> - audit_log_format(ab, " obj=%s", lsmcxt.context);
> - security_release_secctx(&lsmcxt);
> - }
> + audit_log_object_context(ab, &blob);
> }
> if (context->ipc.has_perm) {
> audit_log_end(ab);
> @@ -1588,19 +1569,8 @@ static void audit_log_name(struct audit_context *context, struct audit_names *n,
> from_kgid(&init_user_ns, n->gid),
> MAJOR(n->rdev),
> MINOR(n->rdev));
> - if (lsmblob_is_set(&n->lsmblob)) {
> - struct lsmcontext lsmctx;
> -
> - if (security_secid_to_secctx(&n->lsmblob, &lsmctx,
> - LSMBLOB_FIRST)) {
> - audit_log_format(ab, " osid=?");
> - if (call_panic)
> - *call_panic = 2;
> - } else {
> - audit_log_format(ab, " obj=%s", lsmctx.context);
> - security_release_secctx(&lsmctx);
> - }
> - }
> + if (lsmblob_is_set(&n->lsmblob))
> + audit_log_object_context(ab, &n->lsmblob);
>
> /* log the audit_names record type */
> switch (n->type) {
> @@ -1805,21 +1775,20 @@ static void audit_log_exit(void)
> struct audit_aux_data_pids *axs = (void *)aux;
>
> for (i = 0; i < axs->pid_count; i++)
> - if (audit_log_pid_context(context, axs->target_pid[i],
> - axs->target_auid[i],
> - axs->target_uid[i],
> - axs->target_sessionid[i],
> - &axs->target_lsm[i],
> - axs->target_comm[i]))
> - call_panic = 1;
> - }
> -
> - if (context->target_pid &&
> - audit_log_pid_context(context, context->target_pid,
> - context->target_auid, context->target_uid,
> - context->target_sessionid,
> - &context->target_lsm, context->target_comm))
> - call_panic = 1;
> + audit_log_pid_context(context, axs->target_pid[i],
> + axs->target_auid[i],
> + axs->target_uid[i],
> + axs->target_sessionid[i],
> + &axs->target_lsm[i],
> + axs->target_comm[i]);
> + }
> +
> + if (context->target_pid)
> + audit_log_pid_context(context, context->target_pid,
> + context->target_auid, context->target_uid,
> + context->target_sessionid,
> + &context->target_lsm,
> + context->target_comm);
>
> if (context->pwd.dentry && context->pwd.mnt) {
> ab = audit_log_start(context, GFP_KERNEL, AUDIT_CWD);
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