diff mbox series

[v35,26/29] Audit: Add record for multiple task security contexts

Message ID 20220418145945.38797-27-casey@schaufler-ca.com (mailing list archive)
State New
Headers show
Series [v35,01/29] integrity: disassociate ima_filter_rule from security_audit_rule | expand

Commit Message

Casey Schaufler April 18, 2022, 2:59 p.m. UTC
Create a new audit record AUDIT_MAC_TASK_CONTEXTS.
An example of the MAC_TASK_CONTEXTS (1420) record is:

    type=MAC_TASK_CONTEXTS[1420]
    msg=audit(1600880931.832:113)
    subj_apparmor=unconfined
    subj_smack=_

When an audit event includes a AUDIT_MAC_TASK_CONTEXTS record
the "subj=" field in other records in the event will be "subj=?".
An AUDIT_MAC_TASK_CONTEXTS record is supplied when the system has
multiple security modules that may make access decisions based
on a subject security context.

Functions are created to manage the skb list in the audit_buffer.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 include/uapi/linux/audit.h |  1 +
 kernel/audit.c             | 93 +++++++++++++++++++++++++++++++++++---
 2 files changed, 88 insertions(+), 6 deletions(-)

Comments

Paul Moore April 22, 2022, 4:28 p.m. UTC | #1
On Mon, Apr 18, 2022 at 11:12 AM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Create a new audit record AUDIT_MAC_TASK_CONTEXTS.
> An example of the MAC_TASK_CONTEXTS (1420) record is:
>
>     type=MAC_TASK_CONTEXTS[1420]
>     msg=audit(1600880931.832:113)
>     subj_apparmor=unconfined
>     subj_smack=_
>
> When an audit event includes a AUDIT_MAC_TASK_CONTEXTS record
> the "subj=" field in other records in the event will be "subj=?".
> An AUDIT_MAC_TASK_CONTEXTS record is supplied when the system has
> multiple security modules that may make access decisions based
> on a subject security context.
>
> Functions are created to manage the skb list in the audit_buffer.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  include/uapi/linux/audit.h |  1 +
>  kernel/audit.c             | 93 +++++++++++++++++++++++++++++++++++---
>  2 files changed, 88 insertions(+), 6 deletions(-)

The audit_buffer_aux_new() and audit_buffer_aux_end() belong in patch
25/29, but otherwise this looks okay.

Acked-by: Paul Moore <paul@paul-moore.com>
John Johansen April 26, 2022, 1:08 a.m. UTC | #2
On 4/18/22 07:59, Casey Schaufler wrote:
> Create a new audit record AUDIT_MAC_TASK_CONTEXTS.
> An example of the MAC_TASK_CONTEXTS (1420) record is:
> 
>     type=MAC_TASK_CONTEXTS[1420]
>     msg=audit(1600880931.832:113)
>     subj_apparmor=unconfined
>     subj_smack=_
> 
> When an audit event includes a AUDIT_MAC_TASK_CONTEXTS record
> the "subj=" field in other records in the event will be "subj=?".
> An AUDIT_MAC_TASK_CONTEXTS record is supplied when the system has
> multiple security modules that may make access decisions based
> on a subject security context.
> 
> Functions are created to manage the skb list in the audit_buffer.
> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

Besides moving the aux fns, and the whining below
Reviewed-by: John Johansen <john.johansen@canonical.com>

> ---
>  include/uapi/linux/audit.h |  1 +
>  kernel/audit.c             | 93 +++++++++++++++++++++++++++++++++++---
>  2 files changed, 88 insertions(+), 6 deletions(-)
> 
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 8eda133ca4c1..af0aaccfaf57 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -143,6 +143,7 @@
>  #define AUDIT_MAC_UNLBL_STCDEL	1417	/* NetLabel: del a static label */
>  #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_FIRST_KERN_ANOM_MSG   1700
>  #define AUDIT_LAST_KERN_ANOM_MSG    1799
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 4d44c05053b0..8ed2d717c217 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -2175,8 +2175,61 @@ void audit_log_key(struct audit_buffer *ab, char *key)
>  		audit_log_format(ab, "(null)");
>  }
>  
> +/**
> + * audit_buffer_aux_new - Add an aux record buffer to the skb list
> + * @ab: audit_buffer
> + * @type: message type
> + *
> + * Aux records are allocated and added to the skb list of
> + * the "main" record. The ab->skb is reset to point to the
> + * aux record on its creation. When the aux record in complete
> + * ab->skb has to be reset to point to the "main" record.
> + * This allows the audit_log_ functions to be ignorant of
> + * which kind of record it is logging to. It also avoids adding
> + * special data for aux records.
> + *
> + * On success ab->skb will point to the new aux record.
> + * Returns 0 on success, -ENOMEM should allocation fail.
> + */
> +static int audit_buffer_aux_new(struct audit_buffer *ab, int type)
> +{
> +	WARN_ON(ab->skb != skb_peek(&ab->skb_list));
> +
> +	ab->skb = nlmsg_new(AUDIT_BUFSIZ, ab->gfp_mask);
> +	if (!ab->skb)
> +		goto err;
> +	if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))
> +		goto err;
> +	skb_queue_tail(&ab->skb_list, ab->skb);
> +
> +	audit_log_format(ab, "audit(%llu.%03lu:%u): ",
> +			 (unsigned long long)ab->stamp.ctime.tv_sec,
> +			 ab->stamp.ctime.tv_nsec/1000000,
> +			 ab->stamp.serial);
> +
> +	return 0;
> +
> +err:
> +	kfree_skb(ab->skb);
> +	ab->skb = skb_peek(&ab->skb_list);
> +	return -ENOMEM;
> +}
> +
> +/**
> + * audit_buffer_aux_end - Switch back to the "main" record from an aux record
> + * @ab: audit_buffer
> + *
> + * Restores the "main" audit record to ab->skb.
> + */
> +static void audit_buffer_aux_end(struct audit_buffer *ab)
> +{
> +	ab->skb = skb_peek(&ab->skb_list);
> +}
> +
> +
>  int audit_log_task_context(struct audit_buffer *ab)
>  {
> +	int i;
>  	int error;
>  	struct lsmblob blob;
>  	struct lsmcontext context;
> @@ -2185,16 +2238,44 @@ int audit_log_task_context(struct audit_buffer *ab)
>  	if (!lsmblob_is_set(&blob))
>  		return 0;
>  
> -	error = security_secid_to_secctx(&blob, &context, LSMBLOB_FIRST);
> +	if (!lsm_multiple_contexts()) {
> +		error = security_secid_to_secctx(&blob, &context,
> +						 LSMBLOB_FIRST);
> +		if (error) {
> +			if (error != -EINVAL)
> +				goto error_path;
> +			return 0;
> +		}
>  
> -	if (error) {
> -		if (error != -EINVAL)
> +		audit_log_format(ab, " subj=%s", context.context);
> +		security_release_secctx(&context);
> +	} else {
> +		/* Multiple LSMs provide contexts. Include an aux record. */
> +		audit_log_format(ab, " subj=?");

just me whining, you sure we can't just drop subj= here

> +		error = audit_buffer_aux_new(ab, AUDIT_MAC_TASK_CONTEXTS);
> +		if (error)
>  			goto error_path;
> -		return 0;
> +		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, "%ssubj_%s=?",
> +						 i ? " " : "",
> +						 lsm_slot_to_name(i));
> +				if (error != -EINVAL)
> +					audit_panic("error in audit_log_task_context");
> +			} else {
> +				audit_log_format(ab, "%ssubj_%s=%s",
> +						 i ? " " : "",
> +						 lsm_slot_to_name(i),
> +						 context.context);
> +				security_release_secctx(&context);
> +			}
> +		}
> +		audit_buffer_aux_end(ab);
>  	}
>  
> -	audit_log_format(ab, " subj=%s", context.context);
> -	security_release_secctx(&context);
>  	return 0;
>  
>  error_path:
Paul Moore April 26, 2022, 6:15 p.m. UTC | #3
On Mon, Apr 25, 2022 at 9:08 PM John Johansen
<john.johansen@canonical.com> wrote:
> On 4/18/22 07:59, Casey Schaufler wrote:
> > Create a new audit record AUDIT_MAC_TASK_CONTEXTS.
> > An example of the MAC_TASK_CONTEXTS (1420) record is:
> >
> >     type=MAC_TASK_CONTEXTS[1420]
> >     msg=audit(1600880931.832:113)
> >     subj_apparmor=unconfined
> >     subj_smack=_
> >
> > When an audit event includes a AUDIT_MAC_TASK_CONTEXTS record
> > the "subj=" field in other records in the event will be "subj=?".
> > An AUDIT_MAC_TASK_CONTEXTS record is supplied when the system has
> > multiple security modules that may make access decisions based
> > on a subject security context.
> >
> > Functions are created to manage the skb list in the audit_buffer.
> >
> > Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>
> Besides moving the aux fns, and the whining below
> Reviewed-by: John Johansen <john.johansen@canonical.com>

...

> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 4d44c05053b0..8ed2d717c217 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -2185,16 +2238,44 @@ int audit_log_task_context(struct audit_buffer *ab)
> >       if (!lsmblob_is_set(&blob))
> >               return 0;
> >
> > -     error = security_secid_to_secctx(&blob, &context, LSMBLOB_FIRST);
> > +     if (!lsm_multiple_contexts()) {
> > +             error = security_secid_to_secctx(&blob, &context,
> > +                                              LSMBLOB_FIRST);
> > +             if (error) {
> > +                     if (error != -EINVAL)
> > +                             goto error_path;
> > +                     return 0;
> > +             }
> >
> > -     if (error) {
> > -             if (error != -EINVAL)
> > +             audit_log_format(ab, " subj=%s", context.context);
> > +             security_release_secctx(&context);
> > +     } else {
> > +             /* Multiple LSMs provide contexts. Include an aux record. */
> > +             audit_log_format(ab, " subj=?");
>
> just me whining, you sure we can't just drop subj= here

Have I recently given you my "the audit code is crap" speech? ;)

I more or less answered this with my comments on the earlier patch,
but we need to keep this around for compatibility.  It will get better
in the future.
John Johansen April 26, 2022, 7:07 p.m. UTC | #4
On 4/26/22 11:15, Paul Moore wrote:
> On Mon, Apr 25, 2022 at 9:08 PM John Johansen
> <john.johansen@canonical.com> wrote:
>> On 4/18/22 07:59, Casey Schaufler wrote:
>>> Create a new audit record AUDIT_MAC_TASK_CONTEXTS.
>>> An example of the MAC_TASK_CONTEXTS (1420) record is:
>>>
>>>     type=MAC_TASK_CONTEXTS[1420]
>>>     msg=audit(1600880931.832:113)
>>>     subj_apparmor=unconfined
>>>     subj_smack=_
>>>
>>> When an audit event includes a AUDIT_MAC_TASK_CONTEXTS record
>>> the "subj=" field in other records in the event will be "subj=?".
>>> An AUDIT_MAC_TASK_CONTEXTS record is supplied when the system has
>>> multiple security modules that may make access decisions based
>>> on a subject security context.
>>>
>>> Functions are created to manage the skb list in the audit_buffer.
>>>
>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
>>
>> Besides moving the aux fns, and the whining below
>> Reviewed-by: John Johansen <john.johansen@canonical.com>
> 
> ...
> 
>>> diff --git a/kernel/audit.c b/kernel/audit.c
>>> index 4d44c05053b0..8ed2d717c217 100644
>>> --- a/kernel/audit.c
>>> +++ b/kernel/audit.c
>>> @@ -2185,16 +2238,44 @@ int audit_log_task_context(struct audit_buffer *ab)
>>>       if (!lsmblob_is_set(&blob))
>>>               return 0;
>>>
>>> -     error = security_secid_to_secctx(&blob, &context, LSMBLOB_FIRST);
>>> +     if (!lsm_multiple_contexts()) {
>>> +             error = security_secid_to_secctx(&blob, &context,
>>> +                                              LSMBLOB_FIRST);
>>> +             if (error) {
>>> +                     if (error != -EINVAL)
>>> +                             goto error_path;
>>> +                     return 0;
>>> +             }
>>>
>>> -     if (error) {
>>> -             if (error != -EINVAL)
>>> +             audit_log_format(ab, " subj=%s", context.context);
>>> +             security_release_secctx(&context);
>>> +     } else {
>>> +             /* Multiple LSMs provide contexts. Include an aux record. */
>>> +             audit_log_format(ab, " subj=?");
>>
>> just me whining, you sure we can't just drop subj= here
> 
> Have I recently given you my "the audit code is crap" speech? ;)
> 
hehehe, I get it, something about glass houses and stones. the whole newline
mess in path 28/29 that I would dearly love to drop.

> I more or less answered this with my comments on the earlier patch,
> but we need to keep this around for compatibility.  It will get better
> in the future.
>
diff mbox series

Patch

diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 8eda133ca4c1..af0aaccfaf57 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -143,6 +143,7 @@ 
 #define AUDIT_MAC_UNLBL_STCDEL	1417	/* NetLabel: del a static label */
 #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_FIRST_KERN_ANOM_MSG   1700
 #define AUDIT_LAST_KERN_ANOM_MSG    1799
diff --git a/kernel/audit.c b/kernel/audit.c
index 4d44c05053b0..8ed2d717c217 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -2175,8 +2175,61 @@  void audit_log_key(struct audit_buffer *ab, char *key)
 		audit_log_format(ab, "(null)");
 }
 
+/**
+ * audit_buffer_aux_new - Add an aux record buffer to the skb list
+ * @ab: audit_buffer
+ * @type: message type
+ *
+ * Aux records are allocated and added to the skb list of
+ * the "main" record. The ab->skb is reset to point to the
+ * aux record on its creation. When the aux record in complete
+ * ab->skb has to be reset to point to the "main" record.
+ * This allows the audit_log_ functions to be ignorant of
+ * which kind of record it is logging to. It also avoids adding
+ * special data for aux records.
+ *
+ * On success ab->skb will point to the new aux record.
+ * Returns 0 on success, -ENOMEM should allocation fail.
+ */
+static int audit_buffer_aux_new(struct audit_buffer *ab, int type)
+{
+	WARN_ON(ab->skb != skb_peek(&ab->skb_list));
+
+	ab->skb = nlmsg_new(AUDIT_BUFSIZ, ab->gfp_mask);
+	if (!ab->skb)
+		goto err;
+	if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))
+		goto err;
+	skb_queue_tail(&ab->skb_list, ab->skb);
+
+	audit_log_format(ab, "audit(%llu.%03lu:%u): ",
+			 (unsigned long long)ab->stamp.ctime.tv_sec,
+			 ab->stamp.ctime.tv_nsec/1000000,
+			 ab->stamp.serial);
+
+	return 0;
+
+err:
+	kfree_skb(ab->skb);
+	ab->skb = skb_peek(&ab->skb_list);
+	return -ENOMEM;
+}
+
+/**
+ * audit_buffer_aux_end - Switch back to the "main" record from an aux record
+ * @ab: audit_buffer
+ *
+ * Restores the "main" audit record to ab->skb.
+ */
+static void audit_buffer_aux_end(struct audit_buffer *ab)
+{
+	ab->skb = skb_peek(&ab->skb_list);
+}
+
+
 int audit_log_task_context(struct audit_buffer *ab)
 {
+	int i;
 	int error;
 	struct lsmblob blob;
 	struct lsmcontext context;
@@ -2185,16 +2238,44 @@  int audit_log_task_context(struct audit_buffer *ab)
 	if (!lsmblob_is_set(&blob))
 		return 0;
 
-	error = security_secid_to_secctx(&blob, &context, LSMBLOB_FIRST);
+	if (!lsm_multiple_contexts()) {
+		error = security_secid_to_secctx(&blob, &context,
+						 LSMBLOB_FIRST);
+		if (error) {
+			if (error != -EINVAL)
+				goto error_path;
+			return 0;
+		}
 
-	if (error) {
-		if (error != -EINVAL)
+		audit_log_format(ab, " subj=%s", context.context);
+		security_release_secctx(&context);
+	} else {
+		/* Multiple LSMs provide contexts. Include an aux record. */
+		audit_log_format(ab, " subj=?");
+		error = audit_buffer_aux_new(ab, AUDIT_MAC_TASK_CONTEXTS);
+		if (error)
 			goto error_path;
-		return 0;
+		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, "%ssubj_%s=?",
+						 i ? " " : "",
+						 lsm_slot_to_name(i));
+				if (error != -EINVAL)
+					audit_panic("error in audit_log_task_context");
+			} else {
+				audit_log_format(ab, "%ssubj_%s=%s",
+						 i ? " " : "",
+						 lsm_slot_to_name(i),
+						 context.context);
+				security_release_secctx(&context);
+			}
+		}
+		audit_buffer_aux_end(ab);
 	}
 
-	audit_log_format(ab, " subj=%s", context.context);
-	security_release_secctx(&context);
 	return 0;
 
 error_path: