From: Deven Bowers <[email protected]>
Users of IPE require a way to identify when and why an operation fails,
allowing them to both respond to violations of policy and be notified
of potentially malicious actions on their systems with respect to IPE
itself.
This patch introduces 3 new audit events.
AUDIT_IPE_ACCESS(1420) indicates the result of an IPE policy evaluation
of a resource.
AUDIT_IPE_CONFIG_CHANGE(1421) indicates the current active IPE policy
has been changed to another loaded policy.
AUDIT_IPE_POLICY_LOAD(1422) indicates a new IPE policy has been loaded
into the kernel.
This patch also adds support for success auditing, allowing users to
identify why an allow decision was made for a resource. However, it is
recommended to use this option with caution, as it is quite noisy.
Here are some examples of the new audit record types:
AUDIT_IPE_ACCESS(1420):
audit: AUDIT1420 path="/root/vol/bin/hello" dev="sda"
ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW"
audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
ino=2 rule="DEFAULT action=DENY"
audit: AUDIT1420 path="/tmp/tmpdp2h1lub/deny/bin/hello" dev="tmpfs"
ino=131 rule="DEFAULT action=DENY"
The above three records were generated when the active IPE policy only
allows binaries from the initial booted drive(sda) to run. The three
identical `hello` binary were placed at different locations, only the
first hello from sda was allowed.
Field path followed by the file's path name.
Field dev followed by the device name as found in /dev where the file is
from.
Note that for device mappers it will use the name `dm-X` instead of
the name in /dev/mapper.
For a file in a temp file system, which is not from a device, it will use
`tmpfs` for the field.
The implementation of this part is following another existing use case
LSM_AUDIT_DATA_INODE in security/lsm_audit.c
Field ino followed by the file's inode number.
Field rule followed by the IPE rule made the access decision. The whole
rule must be audited because the decision is based on the combination of
all property conditions in the rule.
Along with the syscall audit event, user can know why a blocked
happened. For example:
audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
ino=2 rule="DEFAULT action=DENY"
audit[1956]: SYSCALL arch=c000003e syscall=59
success=no exit=-13 a0=556790138df0 a1=556790135390 a2=5567901338b0
a3=ab2a41a67f4f1f4e items=1 ppid=147 pid=1956 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)
The above two records showed bash used execve to run "hello" and got
blocked by IPE. Note that the IPE records are always prior to a SYSCALL
record.
AUDIT_IPE_CONFIG_CHANGE(1421):
audit: AUDIT1421
old_active_pol_name="Allow_All" old_active_pol_version=0.0.0
old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855
new_active_pol_name="boot_verified" new_active_pol_version=0.0.0
new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD8EED7B8F4DB
auid=4294967295 ses=4294967295 lsm=ipe res=1
The above record showed the current IPE active policy switch from
`Allow_All` to `boot_verified` along with the version and the hash
digest of the two policies. Note IPE can only have one policy active
at a time, all access decision evaluation is based on the current active
policy.
The normal procedure to deploy a policy is loading the policy to deploy
into the kernel first, then switch the active policy to it.
AUDIT_IPE_POLICY_LOAD(1422):
audit: AUDIT1422 policy_name="boot_verified" policy_version=0.0.0
policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD8EED7B8F4DB
auid=4294967295 ses=4294967295 lsm=ipe res=1
The above record showed a new policy has been loaded into the kernel
with the policy name, policy version and policy hash.
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, the audit system, the evaluation loop,
and access control hooks into separate patches.
+ Further split audit system patch into two separate patches; one
for include/uapi, and the usage of the new defines.
+ Split out the permissive functionality into another separate patch,
for easier review.
+ Correct misuse of audit_log_n_untrusted string to audit_log_format
+ Use get_task_comm instead of comm directly.
+ Quote certain audit values
+ Remove unnecessary help text on choice options - these were
previously
idented at the wrong level
+ Correct a stale string constant (ctx_ns_enforce to ctx_enforce)
v8:
+ Change dependency for CONFIG_AUDIT to CONFIG_AUDITSYSCALL
+ Drop ctx_* prefix
+ Reuse, where appropriate, the audit fields from the field
dictionary. This transforms:
ctx_pathname -> path
ctx_ino -> ino
ctx_dev -> dev
+ Add audit records and event examples to commit description.
+ Remove new_audit_ctx, replace with audit_log_start. All data that
would provided by new_audit_ctx is already present in the syscall
audit record, that is always emitted on these actions. The audit
records should be correlated as such.
+ Change audit types:
+ AUDIT_TRUST_RESULT -> AUDIT_IPE_ACCESS
+ This prevents overloading of the AVC type.
+ AUDIT_TRUST_POLICY_ACTIVATE -> AUDIT_MAC_CONFIG_CHANGE
+ AUDIT_TRUST_POLICY_LOAD -> AUDIT_MAC_POLICY_LOAD
+ There were no significant difference in meaning between
these types.
+ Remove enforcing parameter passed from the context structure
for AUDIT_IPE_ACCESS.
+ This field can be inferred from the SYSCALL audit event,
based on the success field.
+ Remove all fields already captured in the syscall record. "hook",
an IPE specific field, can be determined via the syscall field in
the syscall record itself, so it has been removed.
+ ino, path, and dev in IPE's record refer to the subject of the
syscall, while the syscall record refers to the calling process.
+ remove IPE prefix from policy load/policy activation events
+ fix a bug wherein a policy change audit record was not fired when
updating a policy
v9:
+ Merge the AUDIT_IPE_ACCESS definition with the audit support commit
+ Change the audit format of policy load and switch
+ Remove the ipe audit kernel switch
v10:
+ Create AUDIT_IPE_CONFIG_CHANGE and AUDIT_IPE_POLICY_LOAD
+ Change field names per upstream feedback
---
include/uapi/linux/audit.h | 3 +
security/ipe/Kconfig | 2 +-
security/ipe/Makefile | 1 +
security/ipe/audit.c | 197 +++++++++++++++++++++++++++++++++++++
security/ipe/audit.h | 18 ++++
security/ipe/eval.c | 26 ++++-
security/ipe/eval.h | 8 ++
security/ipe/fs.c | 71 +++++++++++++
security/ipe/policy.c | 5 +
9 files changed, 327 insertions(+), 4 deletions(-)
create mode 100644 security/ipe/audit.c
create mode 100644 security/ipe/audit.h
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index d676ed2b246e..75e21a135483 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -143,6 +143,9 @@
#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_IPE_ACCESS 1420 /* IPE denial or grant */
+#define AUDIT_IPE_CONFIG_CHANGE 1421 /* IPE config change */
+#define AUDIT_IPE_POLICY_LOAD 1422 /* IPE policy load */
#define AUDIT_FIRST_KERN_ANOM_MSG 1700
#define AUDIT_LAST_KERN_ANOM_MSG 1799
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index e4875fb04883..ac4d558e69d5 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -5,7 +5,7 @@
menuconfig SECURITY_IPE
bool "Integrity Policy Enforcement (IPE)"
- depends on SECURITY && SECURITYFS
+ depends on SECURITY && SECURITYFS && AUDIT && AUDITSYSCALL
select PKCS7_MESSAGE_PARSER
select SYSTEM_DATA_VERIFICATION
help
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 8602d71250b4..89a76ad72301 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_SECURITY_IPE) += \
policy.o \
policy_fs.o \
policy_parser.o \
+ audit.o \
diff --git a/security/ipe/audit.c b/security/ipe/audit.c
new file mode 100644
index 000000000000..d3f78a7fc93f
--- /dev/null
+++ b/security/ipe/audit.c
@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/slab.h>
+#include <linux/audit.h>
+#include <linux/types.h>
+#include <crypto/hash.h>
+
+#include "ipe.h"
+#include "eval.h"
+#include "hooks.h"
+#include "policy.h"
+#include "audit.h"
+
+#define ACTSTR(x) ((x) == __IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
+
+#define IPE_AUDIT_HASH_ALG "sha256"
+
+#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\
+ "policy_digest=" IPE_AUDIT_HASH_ALG ":"
+#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\
+ "old_active_pol_version=%hu.%hu.%hu "\
+ "old_policy_digest=" IPE_AUDIT_HASH_ALG ":"
+#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\
+ "new_active_pol_version=%hu.%hu.%hu "\
+ "new_policy_digest=" IPE_AUDIT_HASH_ALG ":"
+
+static const char *const audit_op_names[__IPE_OP_MAX] = {
+ "EXECUTE",
+ "FIRMWARE",
+ "KMODULE",
+ "KEXEC_IMAGE",
+ "KEXEC_INITRAMFS",
+ "IMA_POLICY",
+ "IMA_X509_CERT",
+};
+
+static const char *const audit_prop_names[__IPE_PROP_MAX] = {
+ "boot_verified=FALSE",
+ "boot_verified=TRUE",
+};
+
+/**
+ * audit_rule - audit an IPE policy rule approximation.
+ * @ab: Supplies a pointer to the audit_buffer to append to.
+ * @r: Supplies a pointer to the ipe_rule to approximate a string form for.
+ */
+static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
+{
+ const struct ipe_prop *ptr;
+
+ audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
+
+ list_for_each_entry(ptr, &r->props, next) {
+ audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
+ audit_log_format(ab, " ");
+ }
+
+ audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
+}
+
+/**
+ * ipe_audit_match - audit a match for IPE policy.
+ * @ctx: Supplies a pointer to the evaluation context that was used in the
+ * evaluation.
+ * @match_type: Supplies the scope of the match: rule, operation default,
+ * global default.
+ * @act: Supplies the IPE's evaluation decision, deny or allow.
+ * @r: Supplies a pointer to the rule that was matched, if possible.
+ * @enforce: Supplies the enforcement/permissive state at the point
+ * the enforcement decision was made.
+ */
+void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
+ enum ipe_match match_type,
+ enum ipe_action_type act, const struct ipe_rule *const r)
+{
+ struct inode *inode;
+ struct audit_buffer *ab;
+ const char *op = audit_op_names[ctx->op];
+
+ if (act != __IPE_ACTION_DENY && !READ_ONCE(success_audit))
+ return;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS);
+ if (!ab)
+ return;
+
+ if (ctx->file) {
+ audit_log_d_path(ab, "path=", &ctx->file->f_path);
+ inode = file_inode(ctx->file);
+ if (inode) {
+ audit_log_format(ab, " dev=");
+ audit_log_untrustedstring(ab, inode->i_sb->s_id);
+ audit_log_format(ab, " ino=%lu ", inode->i_ino);
+ }
+ }
+
+ if (match_type == __IPE_MATCH_RULE)
+ audit_rule(ab, r);
+ else if (match_type == __IPE_MATCH_TABLE)
+ audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op,
+ ACTSTR(act));
+ else
+ audit_log_format(ab, "rule=\"DEFAULT action=%s\"",
+ ACTSTR(act));
+
+ audit_log_end(ab);
+}
+
+/**
+ * audit_policy - Audit a policy's name, version and thumbprint to @ab.
+ * @ab: Supplies a pointer to the audit buffer to append to.
+ * @p: Supplies a pointer to the policy to audit.
+ */
+static void audit_policy(struct audit_buffer *ab,
+ const char *audit_format,
+ const struct ipe_policy *const p)
+{
+ u8 *digest = NULL;
+ struct crypto_shash *tfm;
+ SHASH_DESC_ON_STACK(desc, tfm);
+
+ tfm = crypto_alloc_shash(IPE_AUDIT_HASH_ALG, 0, 0);
+ if (IS_ERR(tfm))
+ return;
+
+ desc->tfm = tfm;
+
+ digest = kzalloc(crypto_shash_digestsize(tfm), GFP_KERNEL);
+ if (!digest)
+ goto out;
+
+ if (crypto_shash_init(desc))
+ goto out;
+
+ if (crypto_shash_update(desc, p->pkcs7, p->pkcs7len))
+ goto out;
+
+ if (crypto_shash_final(desc, digest))
+ goto out;
+
+ audit_log_format(ab, audit_format, p->parsed->name,
+ p->parsed->version.major, p->parsed->version.minor,
+ p->parsed->version.rev);
+ audit_log_n_hex(ab, digest, crypto_shash_digestsize(tfm));
+
+out:
+ kfree(digest);
+ crypto_free_shash(tfm);
+}
+
+/**
+ * ipe_audit_policy_activation - Audit a policy being made the active policy.
+ * @p: Supplies a pointer to the policy to audit.
+ */
+void ipe_audit_policy_activation(const struct ipe_policy *const op,
+ const struct ipe_policy *const np)
+{
+ struct audit_buffer *ab;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL,
+ AUDIT_IPE_CONFIG_CHANGE);
+ if (!ab)
+ return;
+
+ audit_policy(ab, AUDIT_OLD_ACTIVE_POLICY_FMT, op);
+ audit_log_format(ab, " ");
+ audit_policy(ab, AUDIT_NEW_ACTIVE_POLICY_FMT, np);
+ 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);
+}
+
+/**
+ * ipe_audit_policy_load - Audit a policy being loaded into the kernel.
+ * @p: Supplies a pointer to the policy to audit.
+ */
+void ipe_audit_policy_load(const struct ipe_policy *const p)
+{
+ struct audit_buffer *ab;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL,
+ AUDIT_IPE_POLICY_LOAD);
+ if (!ab)
+ return;
+
+ audit_policy(ab, AUDIT_POLICY_LOAD_FMT, p);
+ 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);
+}
diff --git a/security/ipe/audit.h b/security/ipe/audit.h
new file mode 100644
index 000000000000..0ff5a06808de
--- /dev/null
+++ b/security/ipe/audit.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#ifndef _IPE_AUDIT_H
+#define _IPE_AUDIT_H
+
+#include "policy.h"
+
+void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
+ enum ipe_match match_type,
+ enum ipe_action_type act, const struct ipe_rule *const r);
+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);
+
+#endif /* _IPE_AUDIT_H */
diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index f19a641535c4..2cb43ad92a65 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -10,13 +10,16 @@
#include <linux/sched.h>
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
+#include <linux/moduleparam.h>
#include "ipe.h"
#include "eval.h"
#include "hooks.h"
#include "policy.h"
+#include "audit.h"
struct ipe_policy __rcu *ipe_active_policy;
+bool success_audit;
static const struct super_block *pinned_sb;
static DEFINE_SPINLOCK(pin_lock);
@@ -114,6 +117,7 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
int rc = 0;
bool match = false;
enum ipe_action_type action;
+ enum ipe_match match_type;
struct ipe_policy *pol = NULL;
const struct ipe_rule *rule = NULL;
const struct ipe_op_table *rules = NULL;
@@ -129,6 +133,7 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
if (ctx->op == __IPE_OP_INVALID) {
action = pol->parsed->global_default_action;
+ match_type = __IPE_MATCH_GLOBAL;
goto eval;
}
@@ -144,15 +149,21 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
break;
}
- if (match)
+ if (match) {
action = rule->action;
- else if (rules->default_action != __IPE_ACTION_INVALID)
+ match_type = __IPE_MATCH_RULE;
+ } else if (rules->default_action != __IPE_ACTION_INVALID) {
action = rules->default_action;
- else
+ match_type = __IPE_MATCH_TABLE;
+ } else {
action = pol->parsed->global_default_action;
+ match_type = __IPE_MATCH_GLOBAL;
+ }
rcu_read_unlock();
eval:
+ ipe_audit_match(ctx, match_type, action, rule);
+
if (action == __IPE_ACTION_DENY)
rc = -EACCES;
@@ -176,3 +187,12 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
spin_unlock(&pin_lock);
}
+
+/* Set the right module name */
+#ifdef KBUILD_MODNAME
+#undef KBUILD_MODNAME
+#define KBUILD_MODNAME "ipe"
+#endif
+
+module_param(success_audit, bool, 0400);
+MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled");
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index 88c625d6af97..8fcdb2ea19f4 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -13,6 +13,7 @@
#include "policy.h"
extern struct ipe_policy __rcu *ipe_active_policy;
+extern bool success_audit;
struct ipe_eval_ctx {
enum ipe_op_type op;
@@ -21,6 +22,13 @@ struct ipe_eval_ctx {
bool from_init_sb;
};
+enum ipe_match {
+ __IPE_MATCH_RULE = 0,
+ __IPE_MATCH_TABLE,
+ __IPE_MATCH_GLOBAL,
+ __IPE_MATCH_MAX
+};
+
void build_eval_ctx(struct ipe_eval_ctx *ctx, const struct file *file, enum ipe_op_type op);
int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx);
void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb);
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index 522162af741a..6bd2aa84831b 100644
--- a/security/ipe/fs.c
+++ b/security/ipe/fs.c
@@ -8,11 +8,65 @@
#include "ipe.h"
#include "fs.h"
+#include "eval.h"
#include "policy.h"
+#include "audit.h"
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;
+
+/**
+ * setaudit - Write handler for the securityfs node, "ipe/success_audit"
+ * @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 setaudit(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;
+
+ value = READ_ONCE(success_audit);
+ rc = kstrtobool_from_user(data, len, &value);
+ if (rc)
+ return rc;
+
+ WRITE_ONCE(success_audit, value);
+
+ return len;
+}
+
+/**
+ * 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.
+ * @offset: unused.
+ *
+ * Return:
+ * * >0 - Success, Length of buffer written
+ * * <0 - Error
+ */
+static ssize_t getaudit(struct file *f, char __user *data,
+ size_t len, loff_t *offset)
+{
+ const char *result;
+
+ result = ((READ_ONCE(success_audit)) ? "1" : "0");
+
+ return simple_read_from_buffer(data, len, offset, result, 1);
+}
/**
* new_policy - Write handler for the securityfs node, "ipe/new_policy".
@@ -46,6 +100,10 @@ static ssize_t new_policy(struct file *f, const char __user *data,
}
rc = ipe_new_policyfs_node(p);
+ if (rc)
+ goto out;
+
+ ipe_audit_policy_load(p);
out:
if (rc < 0 && !IS_ERR(p))
@@ -58,6 +116,11 @@ static const struct file_operations np_fops = {
.write = new_policy,
};
+static const struct file_operations audit_fops = {
+ .write = setaudit,
+ .read = getaudit,
+};
+
/**
* ipe_init_securityfs - Initialize IPE's securityfs tree at fsinit.
*
@@ -78,6 +141,13 @@ static int __init ipe_init_securityfs(void)
goto err;
}
+ audit_node = securityfs_create_file("success_audit", 0600, root,
+ NULL, &audit_fops);
+ if (IS_ERR(audit_node)) {
+ rc = PTR_ERR(audit_node);
+ goto err;
+ }
+
policy_root = securityfs_create_dir("policies", root);
if (IS_ERR(policy_root)) {
rc = PTR_ERR(policy_root);
@@ -94,6 +164,7 @@ static int __init ipe_init_securityfs(void)
err:
securityfs_remove(np);
securityfs_remove(policy_root);
+ securityfs_remove(audit_node);
securityfs_remove(root);
return rc;
}
diff --git a/security/ipe/policy.c b/security/ipe/policy.c
index 3e8e4a06a044..23fa2680d8d7 100644
--- a/security/ipe/policy.c
+++ b/security/ipe/policy.c
@@ -11,6 +11,7 @@
#include "fs.h"
#include "policy.h"
#include "policy_parser.h"
+#include "audit.h"
/* lock for synchronizing writers across ipe policy */
DEFINE_MUTEX(ipe_policy_lock);
@@ -119,6 +120,8 @@ struct ipe_policy *ipe_update_policy(struct inode *root,
swap(new->policyfs, old->policyfs);
+ ipe_audit_policy_load(new);
+
out:
return (rc < 0) ? ERR_PTR(rc) : old;
err:
@@ -204,5 +207,7 @@ int ipe_set_active_pol(const struct ipe_policy *p)
rcu_assign_pointer(ipe_active_policy, p);
+ ipe_audit_policy_activation(ap, p);
+
return 0;
}
--
2.25.1
On Jun 28, 2023 Fan Wu <[email protected]> wrote:
>
> Users of IPE require a way to identify when and why an operation fails,
> allowing them to both respond to violations of policy and be notified
> of potentially malicious actions on their systems with respect to IPE
> itself.
>
> This patch introduces 3 new audit events.
>
> AUDIT_IPE_ACCESS(1420) indicates the result of an IPE policy evaluation
> of a resource.
> AUDIT_IPE_CONFIG_CHANGE(1421) indicates the current active IPE policy
> has been changed to another loaded policy.
> AUDIT_IPE_POLICY_LOAD(1422) indicates a new IPE policy has been loaded
> into the kernel.
>
> This patch also adds support for success auditing, allowing users to
> identify why an allow decision was made for a resource. However, it is
> recommended to use this option with caution, as it is quite noisy.
>
> Here are some examples of the new audit record types:
>
> AUDIT_IPE_ACCESS(1420):
>
> audit: AUDIT1420 path="/root/vol/bin/hello" dev="sda"
> ino=3897 rule="op=EXECUTE boot_verified=TRUE action=ALLOW"
The 'dev' field is already in use by audit, and is used to log the
device major and minor numbers, see audit_log_name() for an example.
I would suggest adopting the existing 'dev' field format, but if you
really want to log the device name as a string you will need to find
another audit field name.
> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
> ino=2 rule="DEFAULT action=DENY"
>
> audit: AUDIT1420 path="/tmp/tmpdp2h1lub/deny/bin/hello" dev="tmpfs"
> ino=131 rule="DEFAULT action=DENY"
>
> The above three records were generated when the active IPE policy only
> allows binaries from the initial booted drive(sda) to run. The three
> identical `hello` binary were placed at different locations, only the
> first hello from sda was allowed.
>
> Field path followed by the file's path name.
>
> Field dev followed by the device name as found in /dev where the file is
> from.
> Note that for device mappers it will use the name `dm-X` instead of
> the name in /dev/mapper.
> For a file in a temp file system, which is not from a device, it will use
> `tmpfs` for the field.
> The implementation of this part is following another existing use case
> LSM_AUDIT_DATA_INODE in security/lsm_audit.c
>
> Field ino followed by the file's inode number.
>
> Field rule followed by the IPE rule made the access decision. The whole
> rule must be audited because the decision is based on the combination of
> all property conditions in the rule.
>
> Along with the syscall audit event, user can know why a blocked
> happened. For example:
>
> audit: AUDIT1420 path="/mnt/ipe/bin/hello" dev="dm-0"
> ino=2 rule="DEFAULT action=DENY"
> audit[1956]: SYSCALL arch=c000003e syscall=59
> success=no exit=-13 a0=556790138df0 a1=556790135390 a2=5567901338b0
> a3=ab2a41a67f4f1f4e items=1 ppid=147 pid=1956 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)
>
> The above two records showed bash used execve to run "hello" and got
> blocked by IPE. Note that the IPE records are always prior to a SYSCALL
> record.
>
> AUDIT_IPE_CONFIG_CHANGE(1421):
>
> audit: AUDIT1421
> old_active_pol_name="Allow_All" old_active_pol_version=0.0.0
> old_policy_digest=sha256:E3B0C44298FC1C149AFBF4C8996FB92427AE41E4649B934CA495991B7852B855
> new_active_pol_name="boot_verified" new_active_pol_version=0.0.0
> new_policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD8EED7B8F4DB
> auid=4294967295 ses=4294967295 lsm=ipe res=1
You can trim hash digest strings so they better fit in terminals, for
example:
old_policy_digest=sha256:E3B0C44....
> The above record showed the current IPE active policy switch from
> `Allow_All` to `boot_verified` along with the version and the hash
> digest of the two policies. Note IPE can only have one policy active
> at a time, all access decision evaluation is based on the current active
> policy.
> The normal procedure to deploy a policy is loading the policy to deploy
> into the kernel first, then switch the active policy to it.
>
> AUDIT_IPE_POLICY_LOAD(1422):
>
> audit: AUDIT1422 policy_name="boot_verified" policy_version=0.0.0
> policy_digest=sha256:820EEA5B40CA42B51F68962354BA083122A20BB846F26765076DD8EED7B8F4DB
> auid=4294967295 ses=4294967295 lsm=ipe res=1
>
> The above record showed a new policy has been loaded into the kernel
> with the policy name, policy version and policy hash.
>
> Signed-off-by: Deven Bowers <[email protected]>
> Signed-off-by: Fan Wu <[email protected]>
> ---
> include/uapi/linux/audit.h | 3 +
> security/ipe/Kconfig | 2 +-
> security/ipe/Makefile | 1 +
> security/ipe/audit.c | 197 +++++++++++++++++++++++++++++++++++++
> security/ipe/audit.h | 18 ++++
> security/ipe/eval.c | 26 ++++-
> security/ipe/eval.h | 8 ++
> security/ipe/fs.c | 71 +++++++++++++
> security/ipe/policy.c | 5 +
> 9 files changed, 327 insertions(+), 4 deletions(-)
> create mode 100644 security/ipe/audit.c
> create mode 100644 security/ipe/audit.h
...
> diff --git a/security/ipe/audit.c b/security/ipe/audit.c
> new file mode 100644
> index 000000000000..d3f78a7fc93f
> --- /dev/null
> +++ b/security/ipe/audit.c
> @@ -0,0 +1,197 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +
> +#include <linux/slab.h>
> +#include <linux/audit.h>
> +#include <linux/types.h>
> +#include <crypto/hash.h>
> +
> +#include "ipe.h"
> +#include "eval.h"
> +#include "hooks.h"
> +#include "policy.h"
> +#include "audit.h"
> +
> +#define ACTSTR(x) ((x) == __IPE_ACTION_ALLOW ? "ALLOW" : "DENY")
> +
> +#define IPE_AUDIT_HASH_ALG "sha256"
> +
> +#define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu "\
> + "policy_digest=" IPE_AUDIT_HASH_ALG ":"
> +#define AUDIT_OLD_ACTIVE_POLICY_FMT "old_active_pol_name=\"%s\" "\
> + "old_active_pol_version=%hu.%hu.%hu "\
> + "old_policy_digest=" IPE_AUDIT_HASH_ALG ":"
> +#define AUDIT_NEW_ACTIVE_POLICY_FMT "new_active_pol_name=\"%s\" "\
> + "new_active_pol_version=%hu.%hu.%hu "\
> + "new_policy_digest=" IPE_AUDIT_HASH_ALG ":"
> +
> +static const char *const audit_op_names[__IPE_OP_MAX] = {
> + "EXECUTE",
> + "FIRMWARE",
> + "KMODULE",
> + "KEXEC_IMAGE",
> + "KEXEC_INITRAMFS",
> + "IMA_POLICY",
> + "IMA_X509_CERT",
> +};
> +
> +static const char *const audit_prop_names[__IPE_PROP_MAX] = {
> + "boot_verified=FALSE",
> + "boot_verified=TRUE",
> +};
> +
> +/**
> + * audit_rule - audit an IPE policy rule approximation.
> + * @ab: Supplies a pointer to the audit_buffer to append to.
> + * @r: Supplies a pointer to the ipe_rule to approximate a string form for.
> + */
> +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r)
> +{
> + const struct ipe_prop *ptr;
> +
> + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]);
> +
> + list_for_each_entry(ptr, &r->props, next) {
> + audit_log_format(ab, "%s", audit_prop_names[ptr->type]);
> + audit_log_format(ab, " ");
Why make two calls to audit_log_format()? You can just use "%s " as
the format string.
> + }
> +
> + audit_log_format(ab, "action=%s\"", ACTSTR(r->action));
> +}
> +
> +/**
> + * ipe_audit_match - audit a match for IPE policy.
> + * @ctx: Supplies a pointer to the evaluation context that was used in the
> + * evaluation.
> + * @match_type: Supplies the scope of the match: rule, operation default,
> + * global default.
> + * @act: Supplies the IPE's evaluation decision, deny or allow.
> + * @r: Supplies a pointer to the rule that was matched, if possible.
> + * @enforce: Supplies the enforcement/permissive state at the point
> + * the enforcement decision was made.
> + */
> +void ipe_audit_match(const struct ipe_eval_ctx *const ctx,
> + enum ipe_match match_type,
> + enum ipe_action_type act, const struct ipe_rule *const r)
> +{
> + struct inode *inode;
> + struct audit_buffer *ab;
> + const char *op = audit_op_names[ctx->op];
> +
> + if (act != __IPE_ACTION_DENY && !READ_ONCE(success_audit))
> + return;
> +
> + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_IPE_ACCESS);
> + if (!ab)
> + return;
> +
> + if (ctx->file) {
> + audit_log_d_path(ab, "path=", &ctx->file->f_path);
> + inode = file_inode(ctx->file);
> + if (inode) {
> + audit_log_format(ab, " dev=");
> + audit_log_untrustedstring(ab, inode->i_sb->s_id);
See my comments above about using the 'dev' field name, however, you
shouldn't need to log the device name as an untrusted string as the
string is coming from a trusted source within the kernel (the driver).
> + audit_log_format(ab, " ino=%lu ", inode->i_ino);
> + }
> + }
> +
> + if (match_type == __IPE_MATCH_RULE)
> + audit_rule(ab, r);
> + else if (match_type == __IPE_MATCH_TABLE)
> + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", op,
> + ACTSTR(act));
> + else
> + audit_log_format(ab, "rule=\"DEFAULT action=%s\"",
> + ACTSTR(act));
> +
> + audit_log_end(ab);
> +}
...
> diff --git a/security/ipe/eval.h b/security/ipe/eval.h
> index 88c625d6af97..8fcdb2ea19f4 100644
> --- a/security/ipe/eval.h
> +++ b/security/ipe/eval.h
> @@ -13,6 +13,7 @@
> #include "policy.h"
>
> extern struct ipe_policy __rcu *ipe_active_policy;
> +extern bool success_audit;
>
> struct ipe_eval_ctx {
> enum ipe_op_type op;
> @@ -21,6 +22,13 @@ struct ipe_eval_ctx {
> bool from_init_sb;
> };
>
> +enum ipe_match {
> + __IPE_MATCH_RULE = 0,
> + __IPE_MATCH_TABLE,
> + __IPE_MATCH_GLOBAL,
> + __IPE_MATCH_MAX
> +};
> +
> void build_eval_ctx(struct ipe_eval_ctx *ctx, const struct file *file, enum ipe_op_type op);
> int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx);
> void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb);
> diff --git a/security/ipe/fs.c b/security/ipe/fs.c
> index 522162af741a..6bd2aa84831b 100644
> --- a/security/ipe/fs.c
> +++ b/security/ipe/fs.c
> @@ -8,11 +8,65 @@
>
> #include "ipe.h"
> #include "fs.h"
> +#include "eval.h"
> #include "policy.h"
> +#include "audit.h"
>
> 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;
> +
> +/**
> + * setaudit - Write handler for the securityfs node, "ipe/success_audit"
> + * @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 setaudit(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;
> +
> + value = READ_ONCE(success_audit);
I don't understand why you are setting @value here only to change its
value in the line below ... ?
> + rc = kstrtobool_from_user(data, len, &value);
> + if (rc)
> + return rc;
> +
> + WRITE_ONCE(success_audit, value);
> +
> + return len;
> +}
--
paul-moore.com