[RFC PATCH v9 08/16] ipe: add permissive toggle
From: Fan Wu
Date: Mon Jan 30 2023 - 17:59:54 EST
From: Deven Bowers <deven.desai@xxxxxxxxxxxxxxxxxxx>
IPE, like SELinux, supports a permissive mode. This mode allows policy
authors to test and evaluate IPE policy without it effecting their
programs. When the mode is changed, a 1404 AUDIT_MAC_STATUS
be reported.
This patch adds the following audit records:
audit: MAC_STATUS permissive=1 auid=4294967295 ses=4294967295 lsm=ipe
res=1
audit: MAC_STATUS permissive=0 auid=4294967295 ses=4294967295 lsm=ipe
res=1
These records are emitted within the following events:
audit: MAC_STATUS permissive=1 auid=4294967295 ses=4294967295 lsm=ipe
res=1
audit[185]: SYSCALL arch=c000003e syscall=1 success=yes exit=2 a0=1
a1=56308bb3ecc0 a2=2 a3=7f290fdc53e0 items=0 ppid=183 pid=185
auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
tty=pts0 ses=4294967295 comm="bash" exe="/usr/bin/bash" key=(null)
audit: PROCTITLE proctitle="-bash"
audit: MAC_STATUS permissive=0 auid=4294967295 ses=4294967295 lsm=ipe
res=1
audit[185]: SYSCALL arch=c000003e syscall=1 success=yes exit=2 a0=1
a1=56308bb3ecc0 a2=2 a3=7f290fdc53e0 items=0 ppid=183 pid=185
auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
tty=pts0 ses=4294967295 comm="bash" exe="/usr/bin/bash" key=(null)
audit: PROCTITLE proctitle="-bash"
Implying user used bash to toggle the switch.
Signed-off-by: Deven Bowers <deven.desai@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Fan Wu <wufan@xxxxxxxxxxxxxxxxxxx>
---
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.
+ Propogating changes to support the new ipe_context structure in the
evaluation loop.
+ Split out permissive functionality into a separate patch for easier
review.
+ Remove permissive switch compile-time configuration option - this
is trivial to add later.
v8:
+ Remove "IPE" prefix from permissive audit record
+ align fields to the linux-audit field dictionary. This causes the
following fields to change:
enforce -> permissive
+ Remove duplicated information correlated with syscall record, that
will always be present in the audit event.
+ Change audit types:
+ AUDIT_TRUST_STATUS -> AUDIT_MAC_STATUS
+ There is no significant difference in meaning between
these types.
v9:
+ Clean up ipe_context related code
---
security/ipe/audit.c | 36 +++++++++++++++++++++++
security/ipe/audit.h | 1 +
security/ipe/eval.c | 9 ++++++
security/ipe/eval.h | 1 +
security/ipe/fs.c | 69 ++++++++++++++++++++++++++++++++++++++++++--
5 files changed, 114 insertions(+), 2 deletions(-)
diff --git a/security/ipe/audit.c b/security/ipe/audit.c
index 295e9f9f5146..ff74026a595f 100644
--- a/security/ipe/audit.c
+++ b/security/ipe/audit.c
@@ -194,3 +194,39 @@ void ipe_audit_policy_load(const struct ipe_policy *const p)
audit_log_end(ab);
}
+
+/**
+ * ipe_audit_enforce - Audit a change in IPE's enforcement state.
+ */
+void ipe_audit_enforce(void)
+{
+ struct audit_buffer *ab;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_MAC_STATUS);
+ if (!ab)
+ return;
+
+ audit_log_format(ab, "permissive=%d", !READ_ONCE(enforce));
+ audit_log_format(ab, " auid=%u ses=%u lsm=ipe res=1",
+ from_kuid(&init_user_ns, audit_get_loginuid(current)),
+ audit_get_sessionid(current));
+
+ audit_log_end(ab);
+}
+
+/**
+ * emit_enforcement - Emit the enforcement state of IPE started with.
+ *
+ * Return:
+ * 0 - Always
+ */
+static int emit_enforcement(void)
+{
+ if (!ipe_enabled)
+ return -EOPNOTSUPP;
+
+ ipe_audit_enforce();
+ return 0;
+}
+
+late_initcall(emit_enforcement);
diff --git a/security/ipe/audit.h b/security/ipe/audit.h
index 2e9b99737f97..4c676ed32846 100644
--- a/security/ipe/audit.h
+++ b/security/ipe/audit.h
@@ -14,5 +14,6 @@ void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
void ipe_audit_policy_load(const struct ipe_policy *const p);
void ipe_audit_policy_activation(const struct ipe_policy *const op,
const struct ipe_policy *const np);
+void ipe_audit_enforce(void);
#endif /* IPE_AUDIT_H */
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index d713808cad9c..499314554b1d 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -20,6 +20,7 @@
struct ipe_policy __rcu *ipe_active_policy;
bool success_audit;
+bool enforce = true;
static struct super_block *pinned_sb;
static DEFINE_SPINLOCK(pin_lock);
@@ -119,6 +120,7 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
{
int rc = 0;
bool match = false;
+ bool enforcing = true;
enum ipe_action_type action;
enum ipe_match match_type;
struct ipe_policy *pol = NULL;
@@ -133,6 +135,8 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
if (!pol)
goto out;
+ enforcing = READ_ONCE(enforce);
+
if (ctx->op == ipe_op_max) {
action = pol->parsed->global_default_action;
match_type = ipe_match_global;
@@ -168,6 +172,9 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
if (action == ipe_action_deny)
rc = -EACCES;
+ if (!enforcing)
+ rc = 0;
+
out:
return rc;
}
@@ -198,3 +205,5 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
module_param(success_audit, bool, 0400);
MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled");
+module_param(enforce, bool, 0400);
+MODULE_PARM_DESC(enforce, "Start IPE in enforce or permissive mode");
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index b83730d0b5ae..64369c3b8cf9 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -14,6 +14,7 @@
extern struct ipe_policy __rcu *ipe_active_policy;
extern bool success_audit;
+extern bool enforce;
struct ipe_eval_ctx {
enum ipe_op_type op;
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index c99616f36f32..bbee17b59b1b 100644
--- a/security/ipe/fs.c
+++ b/security/ipe/fs.c
@@ -15,6 +15,7 @@ static struct dentry *np __ro_after_init;
static struct dentry *root __ro_after_init;
struct dentry *policy_root __ro_after_init;
static struct dentry *audit_node __ro_after_init;
+static struct dentry *enforce_node __ro_after_init;
/**
* setaudit - Write handler for the securityfs node, "ipe/success_audit"
@@ -48,8 +49,8 @@ static ssize_t setaudit(struct file *f, const char __user *data,
/**
* getaudit - Read handler for the securityfs node, "ipe/success_audit"
* @f: Supplies a file structure representing the securityfs node.
- * @data: Supplies a buffer passed to the read syscall
- * @len: Supplies the length of @data
+ * @data: Supplies a buffer passed to the read syscall.
+ * @len: Supplies the length of @data.
* @offset: unused.
*
* Return:
@@ -66,6 +67,57 @@ static ssize_t getaudit(struct file *f, char __user *data,
return simple_read_from_buffer(data, len, offset, result, 1);
}
+/**
+ * setenforce - Write handler for the securityfs node, "ipe/enforce"
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the write syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t setenforce(struct file *f, const char __user *data,
+ size_t len, loff_t *offset)
+{
+ int rc = 0;
+ bool value;
+
+ if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
+ return -EPERM;
+
+ rc = kstrtobool_from_user(data, len, &value);
+ if (rc)
+ return rc;
+
+ WRITE_ONCE(enforce, value);
+ ipe_audit_enforce();
+
+ return len;
+}
+
+/**
+ * getenforce - Read handler for the securityfs node, "ipe/enforce"
+ * @f: Supplies a file structure representing the securityfs node.
+ * @data: Supplies a buffer passed to the read syscall.
+ * @len: Supplies the length of @data.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t getenforce(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ const char *result;
+
+ result = ((READ_ONCE(enforce)) ? "1" : "0");
+
+ return simple_read_from_buffer(data, len, offset, result, 1);
+}
+
/**
* new_policy - Write handler for the securityfs node, "ipe/new_policy".
* @f: Supplies a file structure representing the securityfs node.
@@ -118,6 +170,11 @@ static const struct file_operations audit_fops = {
.read = getaudit,
};
+static const struct file_operations enforce_fops = {
+ .write = setenforce,
+ .read = getenforce,
+};
+
/**
* ipe_init_securityfs - Initialize IPE's securityfs tree at fsinit.
*
@@ -151,6 +208,13 @@ static int __init ipe_init_securityfs(void)
goto err;
}
+ enforce_node = securityfs_create_file("enforce", 0600, root, NULL,
+ &enforce_fops);
+ if (IS_ERR(enforce_node)) {
+ rc = PTR_ERR(enforce_node);
+ goto err;
+ }
+
policy_root = securityfs_create_dir("policies", root);
if (IS_ERR(policy_root)) {
rc = PTR_ERR(policy_root);
@@ -162,6 +226,7 @@ static int __init ipe_init_securityfs(void)
securityfs_remove(np);
securityfs_remove(root);
securityfs_remove(audit_node);
+ securityfs_remove(enforce_node);
securityfs_remove(policy_root);
return rc;
}
--
2.39.0