From: Deven Bowers <[email protected]>
IPE must have a centralized function to evaluate incoming callers
against IPE's policy. This iteration of the policy for against the rules
for that specific caller is known as the evaluation loop.
Signed-off-by: Deven Bowers <[email protected]>
Signed-off-by: Fan Wu <[email protected]>
---
v2:
+ Split evaluation loop, access control hooks, and evaluation loop from policy parser and userspace interface to pass mailing list character limit
v3:
+ Move ipe_load_properties to patch 04.
+ Remove useless 0-initializations Prefix extern variables with ipe_
+ Remove kernel module parameters, as these are exposed through sysctls.
+ Add more prose to the IPE base config option help text.
+ Use GFP_KERNEL for audit_log_start.
+ Remove unnecessary caching system.
+ Remove comments from headers
+ Use rcu_access_pointer for rcu-pointer null check
+ Remove usage of reqprot; use prot only.
+Move policy load and activation audit event to 03/12
v4:
+ Remove sysctls in favor of securityfs nodes
+ Re-add kernel module parameters, as these are now exposed through securityfs.
+ Refactor property audit loop to a separate function.
v5:
+ fix minor grammatical errors
+ do not group rule by curly-brace in audit record,
+ reconstruct the exact rule.
v6:
+ No changes
v7:
+ Further split lsm creation into a separate commit from the evaluation loop and audit system, for easier review.
+ Propagating changes to support the new ipe_context structure in the evaluation loop.
v8:
+ Remove ipe_hook enumeration; hooks can be correlated via syscall record.
v9:
+ Remove ipe_context related code and simplify the evaluation loop.
v10:
+ Split eval part and boot_verified part
---
security/ipe/Makefile | 1 +
security/ipe/eval.c | 94 +++++++++++++++++++++++++++++++++++++++++++
security/ipe/eval.h | 25 ++++++++++++
3 files changed, 120 insertions(+)
create mode 100644 security/ipe/eval.c
create mode 100644 security/ipe/eval.h
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 16bbe80991f1..d7f2870d7c09 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -6,6 +6,7 @@
#
obj-$(CONFIG_SECURITY_IPE) += \
+ eval.o \
hooks.o \
ipe.o \
policy.o \
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
new file mode 100644
index 000000000000..59144b2ecdda
--- /dev/null
+++ b/security/ipe/eval.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/sched.h>
+#include <linux/rcupdate.h>
+
+#include "ipe.h"
+#include "eval.h"
+#include "hooks.h"
+#include "policy.h"
+
+struct ipe_policy __rcu *ipe_active_policy;
+
+/**
+ * evaluate_property - Analyze @ctx against a property.
+ * @ctx: Supplies a pointer to the context to be evaluated.
+ * @p: Supplies a pointer to the property to be evaluated.
+ *
+ * Return:
+ * * true - The current @ctx match the @p
+ * * false - The current @ctx doesn't match the @p
+ */
+static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
+ struct ipe_prop *p)
+{
+ return false;
+}
+
+/**
+ * ipe_evaluate_event - Analyze @ctx against the current active policy.
+ * @ctx: Supplies a pointer to the context to be evaluated.
+ *
+ * This is the loop where all policy evaluation happens against IPE policy.
+ *
+ * Return:
+ * * 0 - OK
+ * * -EACCES - @ctx did not pass evaluation.
+ * * !0 - Error
+ */
+int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
+{
+ int rc = 0;
+ bool match = false;
+ enum ipe_action_type action;
+ struct ipe_policy *pol = NULL;
+ const struct ipe_rule *rule = NULL;
+ const struct ipe_op_table *rules = NULL;
+ struct ipe_prop *prop = NULL;
+
+ rcu_read_lock();
+
+ pol = rcu_dereference(ipe_active_policy);
+ if (!pol) {
+ rcu_read_unlock();
+ return 0;
+ }
+
+ if (ctx->op == __IPE_OP_INVALID) {
+ action = pol->parsed->global_default_action;
+ goto eval;
+ }
+
+ rules = &pol->parsed->rules[ctx->op];
+
+ list_for_each_entry(rule, &rules->rules, next) {
+ match = true;
+
+ list_for_each_entry(prop, &rule->props, next)
+ match = match && evaluate_property(ctx, prop);
+
+ if (match)
+ break;
+ }
+
+ if (match)
+ action = rule->action;
+ else if (rules->default_action != __IPE_ACTION_INVALID)
+ action = rules->default_action;
+ else
+ action = pol->parsed->global_default_action;
+
+ rcu_read_unlock();
+eval:
+ if (action == __IPE_ACTION_DENY)
+ rc = -EACCES;
+
+ return rc;
+}
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
new file mode 100644
index 000000000000..972580dfec15
--- /dev/null
+++ b/security/ipe/eval.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#ifndef _IPE_EVAL_H
+#define _IPE_EVAL_H
+
+#include <linux/file.h>
+#include <linux/types.h>
+
+#include "hooks.h"
+#include "policy.h"
+
+extern struct ipe_policy __rcu *ipe_active_policy;
+
+struct ipe_eval_ctx {
+ enum ipe_op_type op;
+
+ const struct file *file;
+};
+
+int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx);
+
+#endif /* _IPE_EVAL_H */
--
2.25.1
On Jun 28, 2023 Fan Wu <[email protected]> wrote:
>
> IPE must have a centralized function to evaluate incoming callers
> against IPE's policy. This iteration of the policy for against the rules
> for that specific caller is known as the evaluation loop.
Can you rewrite that second sentence, it reads a bit awkward and I'm
unclear as to the meaning.
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> security/ipe/Makefile | 1 +
> security/ipe/eval.c | 94 +++++++++++++++++++++++++++++++++++++++++++
> security/ipe/eval.h | 25 ++++++++++++
> 3 files changed, 120 insertions(+)
> create mode 100644 security/ipe/eval.c
> create mode 100644 security/ipe/eval.h
...
> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
> new file mode 100644
> index 000000000000..59144b2ecdda
> --- /dev/null
> +++ b/security/ipe/eval.c
> @@ -0,0 +1,94 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +
> +#include <linux/fs.h>
> +#include <linux/types.h>
> +#include <linux/slab.h>
> +#include <linux/file.h>
> +#include <linux/sched.h>
> +#include <linux/rcupdate.h>
> +
> +#include "ipe.h"
> +#include "eval.h"
> +#include "hooks.h"
There is no "hooks.h" at this point in the patchset.
In order for 'git bisect' to remain useful (and it can be a very handy
tool), we need to ensure that each point in the patchset compiles
cleanly.
> +#include "policy.h"
> +
> +struct ipe_policy __rcu *ipe_active_policy;
> +
> +/**
> + * evaluate_property - Analyze @ctx against a property.
> + * @ctx: Supplies a pointer to the context to be evaluated.
> + * @p: Supplies a pointer to the property to be evaluated.
> + *
> + * Return:
> + * * true - The current @ctx match the @p
> + * * false - The current @ctx doesn't match the @p
> + */
> +static bool evaluate_property(const struct ipe_eval_ctx *const ctx,
> + struct ipe_prop *p)
> +{
> + return false;
> +}
> +
> +/**
> + * ipe_evaluate_event - Analyze @ctx against the current active policy.
> + * @ctx: Supplies a pointer to the context to be evaluated.
> + *
> + * This is the loop where all policy evaluation happens against IPE policy.
> + *
> + * Return:
> + * * 0 - OK
> + * * -EACCES - @ctx did not pass evaluation.
> + * * !0 - Error
> + */
> +int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
> +{
> + int rc = 0;
> + bool match = false;
> + enum ipe_action_type action;
> + struct ipe_policy *pol = NULL;
> + const struct ipe_rule *rule = NULL;
> + const struct ipe_op_table *rules = NULL;
> + struct ipe_prop *prop = NULL;
> +
> + rcu_read_lock();
> +
> + pol = rcu_dereference(ipe_active_policy);
> + if (!pol) {
> + rcu_read_unlock();
> + return 0;
> + }
> +
> + if (ctx->op == __IPE_OP_INVALID) {
> + action = pol->parsed->global_default_action;
> + goto eval;
It looks like you are missing a rcu_read_unlock() in this case.
Also, given how simplistic the evaluation is in this case, why not
just do it here, saving the assignment, jump, etc.?
if (ctx->op == INVALID) {
rcu_read_unlock()
if (global_action == DENY)
return -EACCES;
return 0;
}
> + }
> +
> + rules = &pol->parsed->rules[ctx->op];
> +
> + list_for_each_entry(rule, &rules->rules, next) {
> + match = true;
> +
> + list_for_each_entry(prop, &rule->props, next)
> + match = match && evaluate_property(ctx, prop);
Why not break from this loop once evaluate_property() returns false?
> +
> + if (match)
> + break;
> + }
> +
> + if (match)
> + action = rule->action;
> + else if (rules->default_action != __IPE_ACTION_INVALID)
> + action = rules->default_action;
> + else
> + action = pol->parsed->global_default_action;
> +
> + rcu_read_unlock();
> +eval:
> + if (action == __IPE_ACTION_DENY)
> + rc = -EACCES;
> +
> + return rc;
This can just be 'return 0;' right?
> +}
--
paul-moore.com