[PATCH 0/2] SELinux: Measure state and hash of policy using IMA

[PATCH 0/2] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

Critical data structures of security modules are currently not measured.
Therefore an attestation service, for instance, would not be able to
attest whether the security modules are always operating with the policies
and configuration that the system administrator had setup. The policies
and configuration for the security modules could be tampered with by
malware by exploiting kernel vulnerabilities or modified through some
inadvertent actions on the system. Measuring such critical data would
enable an attestation service to better assess the state of the system.

IMA subsystem measures system files, command line arguments passed to
kexec, boot aggregate, keys, etc. It can be used to measure critical
data structures of security modules as well.

This change aims to address measuring critical data structures of
SELinux when they are initialized and when they are updated at runtime.

This series is based on commit 3db0d0c276a7 ("integrity: remove
redundant initialization of variable ret") in next-integrity

This series also has a dependency on the following patch series and
should be applied in the following order:
 https://patchwork.kernel.org/patch/11709527/
 https://patchwork.kernel.org/patch/11711249/


Lakshmi Ramasubramanian (2):
  IMA: Handle early boot data measurement
  SELinux: Measure state and hash of policy using IMA

 security/integrity/ima/Kconfig               |   5 +-
 security/integrity/ima/Makefile              |   2 +-
 security/integrity/ima/ima.h                 |  37 ++--
 security/integrity/ima/ima_asymmetric_keys.c |   6 +-
 security/integrity/ima/ima_init.c            |   2 +-
 security/integrity/ima/ima_main.c            |   9 +
 security/integrity/ima/ima_policy.c          |   2 +-
 security/integrity/ima/ima_queue_data.c      | 190 +++++++++++++++++
 security/integrity/ima/ima_queue_keys.c      | 174 ----------------
 security/selinux/Makefile                    |   2 +
 security/selinux/hooks.c                     |   1 +
 security/selinux/include/security.h          |  15 ++
 security/selinux/measure.c                   | 204 +++++++++++++++++++
 security/selinux/selinuxfs.c                 |   3 +
 security/selinux/ss/services.c               |  71 ++++++-
 15 files changed, 516 insertions(+), 207 deletions(-)
 create mode 100644 security/integrity/ima/ima_queue_data.c
 delete mode 100644 security/integrity/ima/ima_queue_keys.c
 create mode 100644 security/selinux/measure.c

-- 
2.28.0

[PATCH 1/2] IMA: Handle early boot data measurement

[Lakshmi Ramasubramanian]

The current implementation of early boot measurement in
the IMA subsystem is very specific to asymmetric keys. It does not
handle measurement of other data such as Linux Security Module (LSM)
data. Since most security modules are initialized very early in
the boot cycle, data provided by those modules are not measured
by IMA. Any other subsystem that initializes early in the boot cycle
and needs IMA to measure their data would suffer from the same issue.

Update the early boot key measurement to handle any early boot data.
Change the kernel configuration CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS to
CONFIG_IMA_QUEUE_EARLY_BOOT_DATA so it can be used for enabling
early boot data measurement. Change this new configuration to support
SECURITY_SELINUX subsystem in addition to KEYS subsystem, which is
currently supported. This can be extended to include more subsystems
in the future by updating this kernel configuration.

Update the IMA hook namely ima_measure_critical_data() to utilize
early boot measurement support.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
 security/integrity/ima/Kconfig               |   5 +-
 security/integrity/ima/Makefile              |   2 +-
 security/integrity/ima/ima.h                 |  37 ++--
 security/integrity/ima/ima_asymmetric_keys.c |   6 +-
 security/integrity/ima/ima_init.c            |   2 +-
 security/integrity/ima/ima_main.c            |   9 +
 security/integrity/ima/ima_policy.c          |   2 +-
 security/integrity/ima/ima_queue_data.c      | 190 +++++++++++++++++++
 security/integrity/ima/ima_queue_keys.c      | 174 -----------------
 9 files changed, 229 insertions(+), 198 deletions(-)
 create mode 100644 security/integrity/ima/ima_queue_data.c
 delete mode 100644 security/integrity/ima/ima_queue_keys.c

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 080c53545ff0..e4fb1761d64a 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -322,10 +322,9 @@ config IMA_MEASURE_ASYMMETRIC_KEYS
 	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y
 	default y
 
-config IMA_QUEUE_EARLY_BOOT_KEYS
+config IMA_QUEUE_EARLY_BOOT_DATA
 	bool
-	depends on IMA_MEASURE_ASYMMETRIC_KEYS
-	depends on SYSTEM_TRUSTED_KEYRING
+	depends on SECURITY_SELINUX || (IMA_MEASURE_ASYMMETRIC_KEYS && SYSTEM_TRUSTED_KEYRING)
 	default y
 
 config IMA_SECURE_AND_OR_TRUSTED_BOOT
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 67dabca670e2..cbbbc9848d2f 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -13,4 +13,4 @@ ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
 ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
 ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
-ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
+ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_DATA) += ima_queue_data.o
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e65ab067e700..8822ad1ef4eb 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -228,29 +228,34 @@ extern const char *const func_tokens[];
 
 struct modsig;
 
-#ifdef CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS
+#ifdef CONFIG_IMA_QUEUE_EARLY_BOOT_DATA
 /*
- * To track keys that need to be measured.
+ * To track data that needs to be measured.
  */
-struct ima_key_entry {
+struct ima_data_entry {
 	struct list_head list;
 	void *payload;
 	size_t payload_len;
-	char *keyring_name;
+	const char *event_name;
+	const char *event_data;
+	enum ima_hooks func;
 };
-void ima_init_key_queue(void);
-bool ima_should_queue_key(void);
-bool ima_queue_key(struct key *keyring, const void *payload,
-		   size_t payload_len);
-void ima_process_queued_keys(void);
+void ima_init_data_queue(void);
+bool ima_should_queue_data(void);
+bool ima_queue_data(const char *event_name, const void *payload,
+		    size_t payload_len, const char *event_data,
+		    enum ima_hooks func);
+void ima_process_queued_data(void);
 #else
-static inline void ima_init_key_queue(void) {}
-static inline bool ima_should_queue_key(void) { return false; }
-static inline bool ima_queue_key(struct key *keyring,
-				 const void *payload,
-				 size_t payload_len) { return false; }
-static inline void ima_process_queued_keys(void) {}
-#endif /* CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS */
+static inline void ima_init_data_queue(void) {}
+static inline bool ima_should_queue_data(void) { return false; }
+static inline bool ima_queue_data(const char *event_name,
+				  const void *payload,
+				  size_t payload_len,
+				  const char *event_data,
+				  enum ima_hooks func) { return false; }
+static inline void ima_process_queued_data(void) {}
+#endif /* CONFIG_IMA_QUEUE_EARLY_BOOT_DATA */
 
 /* LIM API function definitions */
 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index 1c68c500c26f..8f8431f8b096 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -37,8 +37,10 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
 	if (!payload || (payload_len == 0))
 		return;
 
-	if (ima_should_queue_key())
-		queued = ima_queue_key(keyring, payload, payload_len);
+	if (ima_should_queue_data())
+		queued = ima_queue_data(keyring->description, payload,
+					payload_len, keyring->description,
+					KEY_CHECK);
 
 	if (queued)
 		return;
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 4902fe7bd570..892894bf4af3 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -145,7 +145,7 @@ int __init ima_init(void)
 	if (rc != 0)
 		return rc;
 
-	ima_init_key_queue();
+	ima_init_data_queue();
 
 	return rc;
 }
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 129bcaaf13e2..8b27d9dafd6b 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -861,9 +861,18 @@ int ima_measure_critical_data(const char *event_name,
 			      const char *event_data_source,
 			      const void *buf, int buf_len)
 {
+	bool queued = false;
+
 	if (!event_name || !event_data_source || !buf || !buf_len)
 		return -EINVAL;
 
+	if (ima_should_queue_data())
+		queued = ima_queue_data(event_name, buf, buf_len,
+					event_data_source, CRITICAL_DATA);
+
+	if (queued)
+		return 0;
+
 	return process_buffer_measurement(NULL, buf, buf_len, event_name,
 					  CRITICAL_DATA, 0, event_data_source);
 }
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 8451ccb2a775..8f1155a99e89 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -906,7 +906,7 @@ void ima_update_policy(void)
 	ima_update_policy_flag();
 
 	/* Custom IMA policy has been loaded */
-	ima_process_queued_keys();
+	ima_process_queued_data();
 }
 
 /* Keep the enumeration in sync with the policy_tokens! */
diff --git a/security/integrity/ima/ima_queue_data.c b/security/integrity/ima/ima_queue_data.c
new file mode 100644
index 000000000000..93420e7670b9
--- /dev/null
+++ b/security/integrity/ima/ima_queue_data.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Microsoft Corporation
+ *
+ * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
+ *
+ * File: ima_queue_data.c
+ *       Enables deferred processing of data to be measured
+ */
+
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+#include "ima.h"
+
+/*
+ * Flag to indicate whether data can be processed
+ * right away or should be queued for processing later.
+ */
+static bool ima_process_data;
+
+/*
+ * To synchronize access to the list of data that need to be measured
+ */
+static DEFINE_MUTEX(ima_data_lock);
+static LIST_HEAD(ima_queued_data);
+
+/*
+ * If custom IMA policy is not loaded then data queued up
+ * for measurement should be freed. This worker is used
+ * for handling this scenario.
+ */
+static long ima_data_queue_timeout = 300000; /* 5 Minutes */
+static void ima_data_handler(struct work_struct *work);
+static DECLARE_DELAYED_WORK(ima_data_delayed_work, ima_data_handler);
+static bool timer_expired;
+
+/*
+ * This worker function frees data that may still be
+ * queued up in case custom IMA policy was not loaded.
+ */
+static void ima_data_handler(struct work_struct *work)
+{
+	timer_expired = true;
+	ima_process_queued_data();
+}
+
+/*
+ * This function sets up a worker to free queued data in case
+ * custom IMA policy was never loaded.
+ */
+void ima_init_data_queue(void)
+{
+	schedule_delayed_work(&ima_data_delayed_work,
+			      msecs_to_jiffies(ima_data_queue_timeout));
+}
+
+static void ima_free_data_entry(struct ima_data_entry *entry)
+{
+	if (!entry)
+		return;
+
+	kvfree(entry->payload);
+	kfree(entry->event_name);
+	kfree(entry->event_data);
+	kfree(entry);
+}
+
+static void *ima_kvmemdup(const void *src, size_t len)
+{
+	void *p = kvmalloc(len, GFP_KERNEL);
+
+	if (p)
+		memcpy(p, src, len);
+	return p;
+}
+
+static struct ima_data_entry *ima_alloc_data_entry(const char *event_name,
+						   const void *payload,
+						   size_t payload_len,
+						   const char *event_data,
+						   enum ima_hooks func)
+{
+	struct ima_data_entry *entry;
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		goto out;
+
+	/*
+	 * Payload size may exceed the limit supported by kmalloc.
+	 * So use kvmalloc instead.
+	 */
+	entry->payload = ima_kvmemdup(payload, payload_len);
+	entry->event_name = kstrdup(event_name, GFP_KERNEL);
+	if (event_data)
+		entry->event_data = kstrdup(event_data, GFP_KERNEL);
+
+	entry->payload_len = payload_len;
+	entry->func = func;
+
+	if (!entry->payload || !entry->event_name ||
+		(event_data && !entry->event_data))
+		goto out;
+
+	INIT_LIST_HEAD(&entry->list);
+	return entry;
+
+out:
+	integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL,
+				event_name, func_measure_str(func),
+				"ENOMEM", -ENOMEM, 0, -ENOMEM);
+	ima_free_data_entry(entry);
+	return NULL;
+}
+
+bool ima_queue_data(const char *event_name, const void *payload,
+		    size_t payload_len, const char *event_data,
+		    enum ima_hooks func)
+{
+	bool queued = false;
+	struct ima_data_entry *entry;
+
+	entry = ima_alloc_data_entry(event_name, payload, payload_len,
+				     event_data, func);
+	if (!entry)
+		return false;
+
+	mutex_lock(&ima_data_lock);
+	if (!ima_process_data) {
+		list_add_tail(&entry->list, &ima_queued_data);
+		queued = true;
+	}
+	mutex_unlock(&ima_data_lock);
+
+	if (!queued)
+		ima_free_data_entry(entry);
+
+	return queued;
+}
+
+/*
+ * ima_process_queued_data() - process data queued for measurement
+ *
+ * This function sets ima_process_data to true and processes queued data.
+ * From here on data will be processed right away (not queued).
+ */
+void ima_process_queued_data(void)
+{
+	struct ima_data_entry *entry, *tmp;
+	bool process = false;
+
+	if (ima_process_data)
+		return;
+
+	/*
+	 * Since ima_process_data is set to true, any new data will be
+	 * processed immediately and not be queued to ima_queued_data list.
+	 * First one setting the ima_process_data flag to true will
+	 * process the queued data.
+	 */
+	mutex_lock(&ima_data_lock);
+	if (!ima_process_data) {
+		ima_process_data = true;
+		process = true;
+	}
+	mutex_unlock(&ima_data_lock);
+
+	if (!process)
+		return;
+
+	if (!timer_expired)
+		cancel_delayed_work_sync(&ima_data_delayed_work);
+
+	list_for_each_entry_safe(entry, tmp, &ima_queued_data, list) {
+		if (!timer_expired)
+			process_buffer_measurement(NULL, entry->payload,
+						   entry->payload_len,
+						   entry->event_name,
+						   entry->func, 0,
+						   entry->event_data);
+		list_del(&entry->list);
+		ima_free_data_entry(entry);
+	}
+}
+
+inline bool ima_should_queue_data(void)
+{
+	return !ima_process_data;
+}
diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
deleted file mode 100644
index 69a8626a35c0..000000000000
--- a/security/integrity/ima/ima_queue_keys.c
+++ /dev/null
@@ -1,174 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0+
-/*
- * Copyright (C) 2019 Microsoft Corporation
- *
- * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
- *
- * File: ima_queue_keys.c
- *       Enables deferred processing of keys
- */
-
-#include <linux/workqueue.h>
-#include <keys/asymmetric-type.h>
-#include "ima.h"
-
-/*
- * Flag to indicate whether a key can be processed
- * right away or should be queued for processing later.
- */
-static bool ima_process_keys;
-
-/*
- * To synchronize access to the list of keys that need to be measured
- */
-static DEFINE_MUTEX(ima_keys_lock);
-static LIST_HEAD(ima_keys);
-
-/*
- * If custom IMA policy is not loaded then keys queued up
- * for measurement should be freed. This worker is used
- * for handling this scenario.
- */
-static long ima_key_queue_timeout = 300000; /* 5 Minutes */
-static void ima_keys_handler(struct work_struct *work);
-static DECLARE_DELAYED_WORK(ima_keys_delayed_work, ima_keys_handler);
-static bool timer_expired;
-
-/*
- * This worker function frees keys that may still be
- * queued up in case custom IMA policy was not loaded.
- */
-static void ima_keys_handler(struct work_struct *work)
-{
-	timer_expired = true;
-	ima_process_queued_keys();
-}
-
-/*
- * This function sets up a worker to free queued keys in case
- * custom IMA policy was never loaded.
- */
-void ima_init_key_queue(void)
-{
-	schedule_delayed_work(&ima_keys_delayed_work,
-			      msecs_to_jiffies(ima_key_queue_timeout));
-}
-
-static void ima_free_key_entry(struct ima_key_entry *entry)
-{
-	if (entry) {
-		kfree(entry->payload);
-		kfree(entry->keyring_name);
-		kfree(entry);
-	}
-}
-
-static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
-						 const void *payload,
-						 size_t payload_len)
-{
-	int rc = 0;
-	const char *audit_cause = "ENOMEM";
-	struct ima_key_entry *entry;
-
-	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
-	if (entry) {
-		entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
-		entry->keyring_name = kstrdup(keyring->description,
-					      GFP_KERNEL);
-		entry->payload_len = payload_len;
-	}
-
-	if ((entry == NULL) || (entry->payload == NULL) ||
-	    (entry->keyring_name == NULL)) {
-		rc = -ENOMEM;
-		goto out;
-	}
-
-	INIT_LIST_HEAD(&entry->list);
-
-out:
-	if (rc) {
-		integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL,
-					keyring->description,
-					func_measure_str(KEY_CHECK),
-					audit_cause, rc, 0, rc);
-		ima_free_key_entry(entry);
-		entry = NULL;
-	}
-
-	return entry;
-}
-
-bool ima_queue_key(struct key *keyring, const void *payload,
-		   size_t payload_len)
-{
-	bool queued = false;
-	struct ima_key_entry *entry;
-
-	entry = ima_alloc_key_entry(keyring, payload, payload_len);
-	if (!entry)
-		return false;
-
-	mutex_lock(&ima_keys_lock);
-	if (!ima_process_keys) {
-		list_add_tail(&entry->list, &ima_keys);
-		queued = true;
-	}
-	mutex_unlock(&ima_keys_lock);
-
-	if (!queued)
-		ima_free_key_entry(entry);
-
-	return queued;
-}
-
-/*
- * ima_process_queued_keys() - process keys queued for measurement
- *
- * This function sets ima_process_keys to true and processes queued keys.
- * From here on keys will be processed right away (not queued).
- */
-void ima_process_queued_keys(void)
-{
-	struct ima_key_entry *entry, *tmp;
-	bool process = false;
-
-	if (ima_process_keys)
-		return;
-
-	/*
-	 * Since ima_process_keys is set to true, any new key will be
-	 * processed immediately and not be queued to ima_keys list.
-	 * First one setting the ima_process_keys flag to true will
-	 * process the queued keys.
-	 */
-	mutex_lock(&ima_keys_lock);
-	if (!ima_process_keys) {
-		ima_process_keys = true;
-		process = true;
-	}
-	mutex_unlock(&ima_keys_lock);
-
-	if (!process)
-		return;
-
-	if (!timer_expired)
-		cancel_delayed_work_sync(&ima_keys_delayed_work);
-
-	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
-		if (!timer_expired)
-			process_buffer_measurement(NULL, entry->payload,
-						   entry->payload_len,
-						   entry->keyring_name,
-						   KEY_CHECK, 0,
-						   entry->keyring_name);
-		list_del(&entry->list);
-		ima_free_key_entry(entry);
-	}
-}
-
-inline bool ima_should_queue_key(void)
-{
-	return !ima_process_keys;
-}
-- 
2.28.0

[PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

SELinux configuration and policy are some of the critical data for this
security module that needs to be measured. This measurement can be used
by an attestation service, for instance, to verify if the configuration
and policies have been setup correctly and that they haven't been tampered
with at runtime.

Measure SELinux configuration, policy capabilities settings, and the hash
of the loaded policy by calling the IMA hook ima_measure_critical_data().

Sample measurement of SELinux state and hash of the policy:

10 e32e...5ac3 ima-buf sha256:86e8...4594 selinux-state-1595389364:287899386 696e697469616c697a65643d313b656e61626c65643d313b656e666f7263696e673d303b636865636b72657170726f743d313b6e6574776f726b5f706565725f636f6e74726f6c733d313b6f70656e5f7065726d733d313b657874656e6465645f736f636b65745f636c6173733d313b616c776179735f636865636b5f6e6574776f726b3d303b6367726f75705f7365636c6162656c3d313b6e6e705f6e6f737569645f7472616e736974696f6e3d313b67656e66735f7365636c6162656c5f73796d6c696e6b733d303
10 9e81...0857 ima-buf sha256:4941...68fc selinux-policy-hash-1597335667:462051628 8d1d...1834

To verify the measurement check the following:

Execute the following command to extract the measured data
from the IMA log for SELinux configuration (selinux-state).

  grep -m 1 "selinux-state" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | cut -d' ' -f 6 | xxd -r -p

The output should be the list of key-value pairs. For example,
 initialized=1;enabled=1;enforcing=0;checkreqprot=1;network_peer_controls=1;open_perms=1;extended_socket_class=1;always_check_network=0;cgroup_seclabel=1;nnp_nosuid_transition=1;genfs_seclabel_symlinks=0;

To verify the measured data with the current SELinux state:

 => enabled should be set to 1 if /sys/fs/selinux folder exists,
    0 otherwise

For other entries, compare the integer value in the files
 => /sys/fs/selinux/enforce
 => /sys/fs/selinux/checkreqprot
And, each of the policy capabilities files under
 => /sys/fs/selinux/policy_capabilities

For selinux-policy-hash, the hash of SELinux policy is included
in the IMA log entry.

To verify the measured data with the current SELinux policy run
the following commands and verify the output hash values match.

  sha256sum /sys/fs/selinux/policy | cut -d' ' -f 1

  grep -m 1 "selinux-policy-hash" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | cut -d' ' -f 6

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Reported-by: kernel test robot <lkp@intel.com> # error: implicit declaration of function 'vfree'
Reported-by: kernel test robot <lkp@intel.com> # error: implicit declaration of function 'crypto_alloc_shash'
Reported-by: kernel test robot <lkp@intel.com> # sparse: symbol 'security_read_selinux_policy' was not declared. Should it be static?
---
 security/selinux/Makefile           |   2 +
 security/selinux/hooks.c            |   1 +
 security/selinux/include/security.h |  15 ++
 security/selinux/measure.c          | 204 ++++++++++++++++++++++++++++
 security/selinux/selinuxfs.c        |   3 +
 security/selinux/ss/services.c      |  71 ++++++++--
 6 files changed, 287 insertions(+), 9 deletions(-)
 create mode 100644 security/selinux/measure.c

diff --git a/security/selinux/Makefile b/security/selinux/Makefile
index 4d8e0e8adf0b..83d512116341 100644
--- a/security/selinux/Makefile
+++ b/security/selinux/Makefile
@@ -16,6 +16,8 @@ selinux-$(CONFIG_NETLABEL) += netlabel.o
 
 selinux-$(CONFIG_SECURITY_INFINIBAND) += ibpkey.o
 
+selinux-$(CONFIG_IMA) += measure.o
+
 ccflags-y := -I$(srctree)/security/selinux -I$(srctree)/security/selinux/include
 
 $(addprefix $(obj)/,$(selinux-y)): $(obj)/flask.h
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index efa6108b1ce9..5521dfc1900b 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -7394,6 +7394,7 @@ int selinux_disable(struct selinux_state *state)
 	}
 
 	selinux_mark_disabled(state);
+	selinux_measure_state(state);
 
 	pr_info("SELinux:  Disabled at runtime.\n");
 
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index b0e02cfe3ce1..77f42d9b544b 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -222,16 +222,31 @@ static inline bool selinux_policycap_genfs_seclabel_symlinks(void)
 	return state->policycap[POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS];
 }
 
+static inline bool selinux_checkreqprot(const struct selinux_state *state)
+{
+	return READ_ONCE(state->checkreqprot);
+}
+
 int security_mls_enabled(struct selinux_state *state);
 int security_load_policy(struct selinux_state *state,
 			 void *data, size_t len);
 int security_read_policy(struct selinux_state *state,
 			 void **data, size_t *len);
+int security_read_policy_kernel(struct selinux_state *state,
+				void **data, size_t *len);
 size_t security_policydb_len(struct selinux_state *state);
 
 int security_policycap_supported(struct selinux_state *state,
 				 unsigned int req_cap);
 
+#ifdef CONFIG_IMA
+extern void selinux_measure_state(struct selinux_state *selinux_state);
+#else
+static inline void selinux_measure_state(struct selinux_state *selinux_state)
+{
+}
+#endif
+
 #define SEL_VEC_MAX 32
 struct av_decision {
 	u32 allowed;
diff --git a/security/selinux/measure.c b/security/selinux/measure.c
new file mode 100644
index 000000000000..f21b7de4e2ae
--- /dev/null
+++ b/security/selinux/measure.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Measure SELinux state using IMA subsystem.
+ */
+#include <linux/vmalloc.h>
+#include <linux/ktime.h>
+#include <linux/crypto.h>
+#include <crypto/hash.h>
+#include <crypto/hash_info.h>
+#include <linux/ima.h>
+#include "security.h"
+
+/*
+ * This function creates an unique name by appending the timestamp to
+ * the given string. This string is passed as "event name" to the IMA
+ * hook to measure the given SELinux data.
+ *
+ * The data provided by SELinux to the IMA subsystem for measuring may have
+ * already been measured (for instance the same state existed earlier).
+ * But for SELinux the current data represents a state change and hence
+ * needs to be measured again. To enable this, pass an unique "Event Name"
+ * to the IMA hook so that IMA subsystem will always measure the given data.
+ *
+ * For example,
+ * At time T0 SELinux data to be measured is "foo". IMA measures it.
+ * At time T1 the data is changed to "bar". IMA measures it.
+ * At time T2 the data is changed to "foo" again. IMA will not measure it
+ * (since it was already measured) unless the event name, for instance,
+ * is different in this call.
+ */
+static char *selinux_event_name(const char *name_prefix)
+{
+	char *event_name = NULL;
+	struct timespec64 curr_time;
+
+	ktime_get_real_ts64(&curr_time);
+	event_name = kasprintf(GFP_KERNEL, "%s-%lld:%09ld", name_prefix,
+			       curr_time.tv_sec, curr_time.tv_nsec);
+	if (!event_name) {
+		pr_warn("%s: event name not allocated.\n", __func__);
+		return NULL;
+	}
+
+	return event_name;
+}
+
+static int read_selinux_state(char **state_str, int *state_str_len,
+			      struct selinux_state *state)
+{
+	char *buf, *str_fmt = "%s=%d;";
+	int i, buf_len, curr;
+
+	buf_len = snprintf(NULL, 0, str_fmt, "initialized", 0);
+	buf_len += snprintf(NULL, 0, str_fmt, "enabled", 0);
+	buf_len += snprintf(NULL, 0, str_fmt, "enforcing", 0);
+	buf_len += snprintf(NULL, 0, str_fmt, "checkreqprot", 0);
+
+	for (i = 0; i < __POLICYDB_CAPABILITY_MAX; i++) {
+		buf_len += snprintf(NULL, 0, str_fmt,
+				    selinux_policycap_names[i], 0);
+	}
+	++buf_len;
+
+	buf = kzalloc(buf_len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	curr = snprintf(buf, buf_len, str_fmt,
+			"initialized", selinux_initialized(state));
+	curr += snprintf((buf + curr), (buf_len - curr), str_fmt,
+			 "enabled", !selinux_disabled(state));
+	curr += snprintf((buf + curr), (buf_len - curr), str_fmt,
+			 "enforcing", enforcing_enabled(state));
+	curr += snprintf((buf + curr), (buf_len - curr), str_fmt,
+			 "checkreqprot", selinux_checkreqprot(state));
+
+	for (i = 0; i < __POLICYDB_CAPABILITY_MAX; i++) {
+		curr += snprintf((buf + curr), (buf_len - curr), str_fmt,
+				 selinux_policycap_names[i],
+				 state->policycap[i]);
+	}
+
+	*state_str = buf;
+	*state_str_len = curr;
+
+	return 0;
+}
+
+static int selinux_hash_buffer(void *buf, size_t buf_len,
+			       void **buf_hash, int *buf_hash_len)
+{
+	struct crypto_shash *tfm;
+	struct shash_desc *desc = NULL;
+	void *digest = NULL;
+	int desc_size;
+	int digest_size;
+	int ret = 0;
+
+	tfm = crypto_alloc_shash("sha256", 0, 0);
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
+	digest_size = crypto_shash_digestsize(tfm);
+
+	digest = kmalloc(digest_size, GFP_KERNEL);
+	if (!digest) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	desc = kzalloc(desc_size, GFP_KERNEL);
+	if (!desc) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	desc->tfm = tfm;
+
+	ret = crypto_shash_digest(desc, buf, buf_len, digest);
+	if (ret < 0)
+		goto error;
+
+	*buf_hash_len = digest_size;
+	*buf_hash = digest;
+	digest = NULL;
+
+error:
+	kfree(desc);
+	kfree(digest);
+
+	crypto_free_shash(tfm);
+
+	return ret;
+}
+
+void selinux_measure_state(struct selinux_state *state)
+{
+	void *policy = NULL;
+	void *policy_hash = NULL;
+	char *event_name = NULL;
+	char *state_str = NULL;
+	size_t policy_len;
+	int state_str_len, policy_hash_len, rc = 0;
+	bool initialized = selinux_initialized(state);
+
+	rc = read_selinux_state(&state_str, &state_str_len, state);
+	if (rc) {
+		pr_warn("%s: Failed to read selinux state.\n", __func__);
+		return;
+	}
+
+	/*
+	 * Get an unique string for measuring the current SELinux state.
+	 */
+	event_name = selinux_event_name("selinux-state");
+	if (!event_name) {
+		pr_warn("%s: Event name for state not allocated.\n",
+			__func__);
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	rc = ima_measure_critical_data(event_name, "selinux",
+				       state_str, state_str_len);
+
+	kfree(event_name);
+	event_name = NULL;
+
+	if (rc)
+		goto out;
+
+	/*
+	 * Measure SELinux policy only after initialization is completed.
+	 */
+	if (!initialized)
+		goto out;
+
+	rc = security_read_policy_kernel(state, &policy, &policy_len);
+	if (rc)
+		goto out;
+
+	rc = selinux_hash_buffer(policy, policy_len,
+				 &policy_hash, &policy_hash_len);
+	if (rc)
+		goto out;
+
+	event_name = selinux_event_name("selinux-policy-hash");
+	if (!event_name) {
+		pr_warn("%s: Event name for policy not allocated.\n",
+			__func__);
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	rc = ima_measure_critical_data(event_name, "selinux",
+				       policy_hash, policy_hash_len);
+
+out:
+	kfree(event_name);
+	kfree(state_str);
+	kfree(policy_hash);
+	vfree(policy);
+}
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 4781314c2510..6d46eaef5c92 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -173,6 +173,7 @@ static ssize_t sel_write_enforce(struct file *file, const char __user *buf,
 			from_kuid(&init_user_ns, audit_get_loginuid(current)),
 			audit_get_sessionid(current));
 		enforcing_set(state, new_value);
+		selinux_measure_state(state);
 		if (new_value)
 			avc_ss_reset(state->avc, 0);
 		selnl_notify_setenforce(new_value);
@@ -678,6 +679,8 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf,
 
 	fsi->state->checkreqprot = new_value ? 1 : 0;
 	length = count;
+
+	selinux_measure_state(fsi->state);
 out:
 	kfree(page);
 	return length;
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index ef0afd878bfc..3978c804c361 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2182,6 +2182,7 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
 		selinux_status_update_policyload(state, seqno);
 		selinux_netlbl_cache_invalidate();
 		selinux_xfrm_notify_policyload();
+		selinux_measure_state(state);
 		return 0;
 	}
 
@@ -2270,6 +2271,7 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
 	selinux_status_update_policyload(state, seqno);
 	selinux_netlbl_cache_invalidate();
 	selinux_xfrm_notify_policyload();
+	selinux_measure_state(state);
 
 	rc = 0;
 	goto out;
@@ -2941,6 +2943,7 @@ int security_set_bools(struct selinux_state *state, u32 len, int *values)
 		selnl_notify_policyload(seqno);
 		selinux_status_update_policyload(state, seqno);
 		selinux_xfrm_notify_policyload();
+		selinux_measure_state(state);
 	}
 	return rc;
 }
@@ -3720,14 +3723,23 @@ int security_netlbl_sid_to_secattr(struct selinux_state *state,
 }
 #endif /* CONFIG_NETLABEL */
 
+static int security_read_policy_len(struct selinux_state *state, size_t *len)
+{
+	if (!selinux_initialized(state))
+		return -EINVAL;
+
+	*len = security_policydb_len(state);
+	return 0;
+}
+
 /**
- * security_read_policy - read the policy.
+ * security_read_selinux_policy - read the policy.
  * @data: binary policy data
  * @len: length of data in bytes
  *
  */
-int security_read_policy(struct selinux_state *state,
-			 void **data, size_t *len)
+static int security_read_selinux_policy(struct selinux_state *state,
+					void **data, size_t *len)
 {
 	struct policydb *policydb = &state->ss->policydb;
 	int rc;
@@ -3736,12 +3748,6 @@ int security_read_policy(struct selinux_state *state,
 	if (!selinux_initialized(state))
 		return -EINVAL;
 
-	*len = security_policydb_len(state);
-
-	*data = vmalloc_user(*len);
-	if (!*data)
-		return -ENOMEM;
-
 	fp.data = *data;
 	fp.len = *len;
 
@@ -3754,5 +3760,52 @@ int security_read_policy(struct selinux_state *state,
 
 	*len = (unsigned long)fp.data - (unsigned long)*data;
 	return 0;
+}
+
+/**
+ * security_read_policy - read the policy.
+ * @data: binary policy data
+ * @len: length of data in bytes
+ *
+ */
+int security_read_policy(struct selinux_state *state,
+			 void **data, size_t *len)
+{
+	int rc;
+
+	rc = security_read_policy_len(state, len);
+	if (rc)
+		return rc;
+
+	*data = vmalloc_user(*len);
+	if (!*data)
+		return -ENOMEM;
+
+	return security_read_selinux_policy(state, data, len);
+}
+
+/**
+ * security_read_policy_kernel - read the policy.
+ * @data: binary policy data
+ * @len: length of data in bytes
+ *
+ * Allocates kernel memory for reading SELinux policy.
+ * This function is for internal use only and should not
+ * be used for returning data to user space
+ *
+ */
+int security_read_policy_kernel(struct selinux_state *state,
+				void **data, size_t *len)
+{
+	int rc;
+
+	rc = security_read_policy_len(state, len);
+	if (rc)
+		return rc;
+
+	*data = vmalloc(*len);
+	if (!*data)
+		return -ENOMEM;
 
+	return security_read_selinux_policy(state, data, len);
 }
-- 
2.28.0

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Stephen Smalley]

On 8/13/20 1:07 PM, Lakshmi Ramasubramanian wrote:

> SELinux configuration and policy are some of the critical data for this
> security module that needs to be measured. This measurement can be used
> by an attestation service, for instance, to verify if the configuration
> and policies have been setup correctly and that they haven't been tampered
> with at runtime.
>
> Measure SELinux configuration, policy capabilities settings, and the hash
> of the loaded policy by calling the IMA hook ima_measure_critical_data().
>
> Sample measurement of SELinux state and hash of the policy:
>
> 10 e32e...5ac3 ima-buf sha256:86e8...4594 selinux-state-1595389364:287899386 696e697469616c697a65643d313b656e61626c65643d313b656e666f7263696e673d303b636865636b72657170726f743d313b6e6574776f726b5f706565725f636f6e74726f6c733d313b6f70656e5f7065726d733d313b657874656e6465645f736f636b65745f636c6173733d313b616c776179735f636865636b5f6e6574776f726b3d303b6367726f75705f7365636c6162656c3d313b6e6e705f6e6f737569645f7472616e736974696f6e3d313b67656e66735f7365636c6162656c5f73796d6c696e6b733d303
> 10 9e81...0857 ima-buf sha256:4941...68fc selinux-policy-hash-1597335667:462051628 8d1d...1834
>
> To verify the measurement check the following:
>
> Execute the following command to extract the measured data
> from the IMA log for SELinux configuration (selinux-state).
>
>    grep -m 1 "selinux-state" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | cut -d' ' -f 6 | xxd -r -p
>
> The output should be the list of key-value pairs. For example,
>   initialized=1;enabled=1;enforcing=0;checkreqprot=1;network_peer_controls=1;open_perms=1;extended_socket_class=1;always_check_network=0;cgroup_seclabel=1;nnp_nosuid_transition=1;genfs_seclabel_symlinks=0;
>
> To verify the measured data with the current SELinux state:
>
>   => enabled should be set to 1 if /sys/fs/selinux folder exists,
>      0 otherwise
>
> For other entries, compare the integer value in the files
>   => /sys/fs/selinux/enforce
>   => /sys/fs/selinux/checkreqprot
> And, each of the policy capabilities files under
>   => /sys/fs/selinux/policy_capabilities
>
> For selinux-policy-hash, the hash of SELinux policy is included
> in the IMA log entry.
>
> To verify the measured data with the current SELinux policy run
> the following commands and verify the output hash values match.
>
>    sha256sum /sys/fs/selinux/policy | cut -d' ' -f 1
>
>    grep -m 1 "selinux-policy-hash" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | cut -d' ' -f 6
>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
> Reported-by: kernel test robot <lkp@intel.com> # error: implicit declaration of function 'vfree'
> Reported-by: kernel test robot <lkp@intel.com> # error: implicit declaration of function 'crypto_alloc_shash'
> Reported-by: kernel test robot <lkp@intel.com> # sparse: symbol 'security_read_selinux_policy' was not declared. Should it be static?
> ---
>   
> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
> new file mode 100644
> index 000000000000..f21b7de4e2ae
> --- /dev/null
> +++ b/security/selinux/measure.c
> @@ -0,0 +1,204 @@
> +static int selinux_hash_buffer(void *buf, size_t buf_len,
> +			       void **buf_hash, int *buf_hash_len)
> +{
> +	struct crypto_shash *tfm;
> +	struct shash_desc *desc = NULL;
> +	void *digest = NULL;
> +	int desc_size;
> +	int digest_size;
> +	int ret = 0;
> +
> +	tfm = crypto_alloc_shash("sha256", 0, 0);
> +	if (IS_ERR(tfm))
> +		return PTR_ERR(tfm);
Can we make the algorithm selectable via kernel parameter and/or writing 
to a new selinuxfs node?

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

On 8/13/20 10:42 AM, Stephen Smalley wrote:

>> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
>> new file mode 100644
>> index 000000000000..f21b7de4e2ae
>> --- /dev/null
>> +++ b/security/selinux/measure.c
>> @@ -0,0 +1,204 @@
>> +static int selinux_hash_buffer(void *buf, size_t buf_len,
>> +                   void **buf_hash, int *buf_hash_len)
>> +{
>> +    struct crypto_shash *tfm;
>> +    struct shash_desc *desc = NULL;
>> +    void *digest = NULL;
>> +    int desc_size;
>> +    int digest_size;
>> +    int ret = 0;
>> +
>> +    tfm = crypto_alloc_shash("sha256", 0, 0);
>> +    if (IS_ERR(tfm))
>> +        return PTR_ERR(tfm);
> Can we make the algorithm selectable via kernel parameter and/or writing 
> to a new selinuxfs node?

I can add a kernel parameter to select this hash algorithm.

  -lakshmi

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Stephen Smalley]

On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
<nramas@linux.microsoft.com> wrote:
>
> On 8/13/20 10:42 AM, Stephen Smalley wrote:
>
> >> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
> >> new file mode 100644
> >> index 000000000000..f21b7de4e2ae
> >> --- /dev/null
> >> +++ b/security/selinux/measure.c
> >> @@ -0,0 +1,204 @@
> >> +static int selinux_hash_buffer(void *buf, size_t buf_len,
> >> +                   void **buf_hash, int *buf_hash_len)
> >> +{
> >> +    struct crypto_shash *tfm;
> >> +    struct shash_desc *desc = NULL;
> >> +    void *digest = NULL;
> >> +    int desc_size;
> >> +    int digest_size;
> >> +    int ret = 0;
> >> +
> >> +    tfm = crypto_alloc_shash("sha256", 0, 0);
> >> +    if (IS_ERR(tfm))
> >> +        return PTR_ERR(tfm);
> > Can we make the algorithm selectable via kernel parameter and/or writing
> > to a new selinuxfs node?
>
> I can add a kernel parameter to select this hash algorithm.

Also can we provide a Kconfig option for the default value like IMA does?

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

On 8/13/20 10:58 AM, Stephen Smalley wrote:
> On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
> <nramas@linux.microsoft.com> wrote:
>>
>> On 8/13/20 10:42 AM, Stephen Smalley wrote:
>>
>>>> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
>>>> new file mode 100644
>>>> index 000000000000..f21b7de4e2ae
>>>> --- /dev/null
>>>> +++ b/security/selinux/measure.c
>>>> @@ -0,0 +1,204 @@
>>>> +static int selinux_hash_buffer(void *buf, size_t buf_len,
>>>> +                   void **buf_hash, int *buf_hash_len)
>>>> +{
>>>> +    struct crypto_shash *tfm;
>>>> +    struct shash_desc *desc = NULL;
>>>> +    void *digest = NULL;
>>>> +    int desc_size;
>>>> +    int digest_size;
>>>> +    int ret = 0;
>>>> +
>>>> +    tfm = crypto_alloc_shash("sha256", 0, 0);
>>>> +    if (IS_ERR(tfm))
>>>> +        return PTR_ERR(tfm);
>>> Can we make the algorithm selectable via kernel parameter and/or writing
>>> to a new selinuxfs node?
>>
>> I can add a kernel parameter to select this hash algorithm.
> 
> Also can we provide a Kconfig option for the default value like IMA does?
> 

Would we need both - Kconfig and kernel param?

The other option is to provide an IMA function to return the current 
hash algorithm used for measurement. That way a consistent hash 
algorithm can be employed by both IMA and the callers. Would that be better?

  -lakshmi

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Stephen Smalley]

On Thu, Aug 13, 2020 at 2:03 PM Lakshmi Ramasubramanian
<nramas@linux.microsoft.com> wrote:
>
> On 8/13/20 10:58 AM, Stephen Smalley wrote:
> > On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
> > <nramas@linux.microsoft.com> wrote:
> >>
> >> On 8/13/20 10:42 AM, Stephen Smalley wrote:
> >>
> >>>> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
> >>>> new file mode 100644
> >>>> index 000000000000..f21b7de4e2ae
> >>>> --- /dev/null
> >>>> +++ b/security/selinux/measure.c
> >>>> @@ -0,0 +1,204 @@
> >>>> +static int selinux_hash_buffer(void *buf, size_t buf_len,
> >>>> +                   void **buf_hash, int *buf_hash_len)
> >>>> +{
> >>>> +    struct crypto_shash *tfm;
> >>>> +    struct shash_desc *desc = NULL;
> >>>> +    void *digest = NULL;
> >>>> +    int desc_size;
> >>>> +    int digest_size;
> >>>> +    int ret = 0;
> >>>> +
> >>>> +    tfm = crypto_alloc_shash("sha256", 0, 0);
> >>>> +    if (IS_ERR(tfm))
> >>>> +        return PTR_ERR(tfm);
> >>> Can we make the algorithm selectable via kernel parameter and/or writing
> >>> to a new selinuxfs node?
> >>
> >> I can add a kernel parameter to select this hash algorithm.
> >
> > Also can we provide a Kconfig option for the default value like IMA does?
> >
>
> Would we need both - Kconfig and kernel param?
>
> The other option is to provide an IMA function to return the current
> hash algorithm used for measurement. That way a consistent hash
> algorithm can be employed by both IMA and the callers. Would that be better?

This is why I preferred just passing the serialized policy buffer to
IMA and letting it handle the hashing.  But apparently that approach
wouldn't fly.  IMA appears to support both a Kconfig option for
selecting a default algorithm and a kernel parameter for overriding
it.  I assume the idea is that the distros can pick a reasonable
default and then the end users can override that if they have specific
requirements.  I'd want the same for SELinux.  If IMA is willing to
export its hash algorithm to external components, then I'm willing to
reuse that but not sure if that's a layering violation.

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Mimi Zohar]

On Thu, 2020-08-13 at 14:13 -0400, Stephen Smalley wrote:
> On Thu, Aug 13, 2020 at 2:03 PM Lakshmi Ramasubramanian
> <nramas@linux.microsoft.com> wrote:
> > On 8/13/20 10:58 AM, Stephen Smalley wrote:
> > > On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
> > > <nramas@linux.microsoft.com> wrote:
> > > > On 8/13/20 10:42 AM, Stephen Smalley wrote:
> > > > 
> > > > > > diff --git a/security/selinux/measure.c b/security/selinux/measure.c
> > > > > > new file mode 100644
> > > > > > index 000000000000..f21b7de4e2ae
> > > > > > --- /dev/null
> > > > > > +++ b/security/selinux/measure.c
> > > > > > @@ -0,0 +1,204 @@
> > > > > > +static int selinux_hash_buffer(void *buf, size_t buf_len,
> > > > > > +                   void **buf_hash, int *buf_hash_len)
> > > > > > +{
> > > > > > +    struct crypto_shash *tfm;
> > > > > > +    struct shash_desc *desc = NULL;
> > > > > > +    void *digest = NULL;
> > > > > > +    int desc_size;
> > > > > > +    int digest_size;
> > > > > > +    int ret = 0;
> > > > > > +
> > > > > > +    tfm = crypto_alloc_shash("sha256", 0, 0);
> > > > > > +    if (IS_ERR(tfm))
> > > > > > +        return PTR_ERR(tfm);
> > > > > Can we make the algorithm selectable via kernel parameter and/or writing
> > > > > to a new selinuxfs node?
> > > > 
> > > > I can add a kernel parameter to select this hash algorithm.
> > > 
> > > Also can we provide a Kconfig option for the default value like IMA does?
> > > 
> > 
> > Would we need both - Kconfig and kernel param?
> > 
> > The other option is to provide an IMA function to return the current
> > hash algorithm used for measurement. That way a consistent hash
> > algorithm can be employed by both IMA and the callers. Would that be better?
> 
> This is why I preferred just passing the serialized policy buffer to
> IMA and letting it handle the hashing.  But apparently that approach
> wouldn't fly.  IMA appears to support both a Kconfig option for
> selecting a default algorithm and a kernel parameter for overriding
> it.  I assume the idea is that the distros can pick a reasonable
> default and then the end users can override that if they have specific
> requirements.  I'd want the same for SELinux.  If IMA is willing to
> export its hash algorithm to external components, then I'm willing to
> reuse that but not sure if that's a layering violation.

With the new ima_measure_critical_data() hook, I agree with you and
Casey it doesn't make sense for each caller to have to write their own
function.  Casey suggested exporting IMA's hash function or defining a
new common hash function.   There's nothing specific to IMA.  Should
the common hash function be prefixed with "security_"?

Like when we add a new security hook call, the new LSM call is separate
from any other change.   Please break up this patch with the SELinux
specific pieces separated from the ima_measure_critical_data() call as
much as possible.

thanks,

Mimi

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Casey Schaufler]

On 8/17/2020 2:31 PM, Mimi Zohar wrote:
> On Thu, 2020-08-13 at 14:13 -0400, Stephen Smalley wrote:
>> On Thu, Aug 13, 2020 at 2:03 PM Lakshmi Ramasubramanian
>> <nramas@linux.microsoft.com> wrote:
>>> On 8/13/20 10:58 AM, Stephen Smalley wrote:
>>>> On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
>>>> <nramas@linux.microsoft.com> wrote:
>>>>> On 8/13/20 10:42 AM, Stephen Smalley wrote:
>>>>>
>>>>>>> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
>>>>>>> new file mode 100644
>>>>>>> index 000000000000..f21b7de4e2ae
>>>>>>> --- /dev/null
>>>>>>> +++ b/security/selinux/measure.c
>>>>>>> @@ -0,0 +1,204 @@
>>>>>>> +static int selinux_hash_buffer(void *buf, size_t buf_len,
>>>>>>> +                   void **buf_hash, int *buf_hash_len)
>>>>>>> +{
>>>>>>> +    struct crypto_shash *tfm;
>>>>>>> +    struct shash_desc *desc = NULL;
>>>>>>> +    void *digest = NULL;
>>>>>>> +    int desc_size;
>>>>>>> +    int digest_size;
>>>>>>> +    int ret = 0;
>>>>>>> +
>>>>>>> +    tfm = crypto_alloc_shash("sha256", 0, 0);
>>>>>>> +    if (IS_ERR(tfm))
>>>>>>> +        return PTR_ERR(tfm);
>>>>>> Can we make the algorithm selectable via kernel parameter and/or writing
>>>>>> to a new selinuxfs node?
>>>>> I can add a kernel parameter to select this hash algorithm.
>>>> Also can we provide a Kconfig option for the default value like IMA does?
>>>>
>>> Would we need both - Kconfig and kernel param?
>>>
>>> The other option is to provide an IMA function to return the current
>>> hash algorithm used for measurement. That way a consistent hash
>>> algorithm can be employed by both IMA and the callers. Would that be better?
>> This is why I preferred just passing the serialized policy buffer to
>> IMA and letting it handle the hashing.  But apparently that approach
>> wouldn't fly.  IMA appears to support both a Kconfig option for
>> selecting a default algorithm and a kernel parameter for overriding
>> it.  I assume the idea is that the distros can pick a reasonable
>> default and then the end users can override that if they have specific
>> requirements.  I'd want the same for SELinux.  If IMA is willing to
>> export its hash algorithm to external components, then I'm willing to
>> reuse that but not sure if that's a layering violation.
> With the new ima_measure_critical_data() hook, I agree with you and
> Casey it doesn't make sense for each caller to have to write their own
> function.  Casey suggested exporting IMA's hash function or defining a
> new common hash function.   There's nothing specific to IMA.

Except that no one is going to use the function unless they're
doing an IMA operation. 

>   Should
> the common hash function be prefixed with "security_"?

Yuck. That prefix is for interfaces that are exported outside the
security sub-system. We're talking about a function that is provided
for use within the security sub-system, but not for any one particular
security module or non-module feature. We're currently using the lsm_
prefix for interfaces used within the security subsystem, so I suggest
lsm_hash_brown_potatoes() might be the way to go.

>
> Like when we add a new security hook call, the new LSM call is separate
> from any other change.   Please break up this patch with the SELinux
> specific pieces separated from the ima_measure_critical_data() call as
> much as possible.
>
> thanks,
>
> Mimi
>

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

On 8/17/20 3:00 PM, Casey Schaufler wrote:
> On 8/17/2020 2:31 PM, Mimi Zohar wrote:
>> On Thu, 2020-08-13 at 14:13 -0400, Stephen Smalley wrote:
>>> On Thu, Aug 13, 2020 at 2:03 PM Lakshmi Ramasubramanian
>>> <nramas@linux.microsoft.com> wrote:
>>>> On 8/13/20 10:58 AM, Stephen Smalley wrote:
>>>>> On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
>>>>> <nramas@linux.microsoft.com> wrote:
>>>>>> On 8/13/20 10:42 AM, Stephen Smalley wrote:
>>>>>>
>>>>>>>> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
>>>>>>>> new file mode 100644
>>>>>>>> index 000000000000..f21b7de4e2ae
>>>>>>>> --- /dev/null
>>>>>>>> +++ b/security/selinux/measure.c
>>>>>>>> @@ -0,0 +1,204 @@
>>>>>>>> +static int selinux_hash_buffer(void *buf, size_t buf_len,
>>>>>>>> +                   void **buf_hash, int *buf_hash_len)
>>>>>>>> +{
>>>>>>>> +    struct crypto_shash *tfm;
>>>>>>>> +    struct shash_desc *desc = NULL;
>>>>>>>> +    void *digest = NULL;
>>>>>>>> +    int desc_size;
>>>>>>>> +    int digest_size;
>>>>>>>> +    int ret = 0;
>>>>>>>> +
>>>>>>>> +    tfm = crypto_alloc_shash("sha256", 0, 0);
>>>>>>>> +    if (IS_ERR(tfm))
>>>>>>>> +        return PTR_ERR(tfm);
>>>>>>> Can we make the algorithm selectable via kernel parameter and/or writing
>>>>>>> to a new selinuxfs node?
>>>>>> I can add a kernel parameter to select this hash algorithm.
>>>>> Also can we provide a Kconfig option for the default value like IMA does?
>>>>>
>>>> Would we need both - Kconfig and kernel param?
>>>>
>>>> The other option is to provide an IMA function to return the current
>>>> hash algorithm used for measurement. That way a consistent hash
>>>> algorithm can be employed by both IMA and the callers. Would that be better?
>>> This is why I preferred just passing the serialized policy buffer to
>>> IMA and letting it handle the hashing.  But apparently that approach
>>> wouldn't fly.  IMA appears to support both a Kconfig option for
>>> selecting a default algorithm and a kernel parameter for overriding
>>> it.  I assume the idea is that the distros can pick a reasonable
>>> default and then the end users can override that if they have specific
>>> requirements.  I'd want the same for SELinux.  If IMA is willing to
>>> export its hash algorithm to external components, then I'm willing to
>>> reuse that but not sure if that's a layering violation.
>> With the new ima_measure_critical_data() hook, I agree with you and
>> Casey it doesn't make sense for each caller to have to write their own
>> function.  Casey suggested exporting IMA's hash function or defining a
>> new common hash function.   There's nothing specific to IMA.
> 
> Except that no one is going to use the function unless they're
> doing an IMA operation.

Can we do the following instead:

In ima_measure_critical_data() IMA hook, we can add another param for 
the caller to indicate whether

  => The contents of "buf" needs to be measured
     OR
  => Hash of the contents of "buf" needs to be measured.

This way IMA doesn't need to export any new function to meet the hashing 
requirement.

  -lakshmi

> 
>>    Should
>> the common hash function be prefixed with "security_"?
> 
> Yuck. That prefix is for interfaces that are exported outside the
> security sub-system. We're talking about a function that is provided
> for use within the security sub-system, but not for any one particular
> security module or non-module feature. We're currently using the lsm_
> prefix for interfaces used within the security subsystem, so I suggest
> lsm_hash_brown_potatoes() might be the way to go.


> 
>>
>> Like when we add a new security hook call, the new LSM call is separate
>> from any other change.   Please break up this patch with the SELinux
>> specific pieces separated from the ima_measure_critical_data() call as
>> much as possible.
>>

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Mimi Zohar]

On Mon, 2020-08-17 at 15:33 -0700, Lakshmi Ramasubramanian wrote:
> On 8/17/20 3:00 PM, Casey Schaufler wrote:
> > On 8/17/2020 2:31 PM, Mimi Zohar wrote:
> > > On Thu, 2020-08-13 at 14:13 -0400, Stephen Smalley wrote:
> > > > On Thu, Aug 13, 2020 at 2:03 PM Lakshmi Ramasubramanian
> > > > <nramas@linux.microsoft.com> wrote:
> > > > > On 8/13/20 10:58 AM, Stephen Smalley wrote:
> > > > > > On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
> > > > > > <nramas@linux.microsoft.com> wrote:
> > > > > > > On 8/13/20 10:42 AM, Stephen Smalley wrote:
> > > > > > > 
> > > > > > > > > diff --git a/security/selinux/measure.c b/security/selinux/measure.c
> > > > > > > > > new file mode 100644
> > > > > > > > > index 000000000000..f21b7de4e2ae
> > > > > > > > > --- /dev/null
> > > > > > > > > +++ b/security/selinux/measure.c
> > > > > > > > > @@ -0,0 +1,204 @@
> > > > > > > > > +static int selinux_hash_buffer(void *buf, size_t buf_len,
> > > > > > > > > +                   void **buf_hash, int *buf_hash_len)
> > > > > > > > > +{
> > > > > > > > > +    struct crypto_shash *tfm;
> > > > > > > > > +    struct shash_desc *desc = NULL;
> > > > > > > > > +    void *digest = NULL;
> > > > > > > > > +    int desc_size;
> > > > > > > > > +    int digest_size;
> > > > > > > > > +    int ret = 0;
> > > > > > > > > +
> > > > > > > > > +    tfm = crypto_alloc_shash("sha256", 0, 0);
> > > > > > > > > +    if (IS_ERR(tfm))
> > > > > > > > > +        return PTR_ERR(tfm);
> > > > > > > > Can we make the algorithm selectable via kernel parameter and/or writing
> > > > > > > > to a new selinuxfs node?
> > > > > > > I can add a kernel parameter to select this hash algorithm.
> > > > > > Also can we provide a Kconfig option for the default value like IMA does?
> > > > > > 
> > > > > Would we need both - Kconfig and kernel param?
> > > > > 
> > > > > The other option is to provide an IMA function to return the current
> > > > > hash algorithm used for measurement. That way a consistent hash
> > > > > algorithm can be employed by both IMA and the callers. Would that be better?
> > > > This is why I preferred just passing the serialized policy buffer to
> > > > IMA and letting it handle the hashing.  But apparently that approach
> > > > wouldn't fly.  IMA appears to support both a Kconfig option for
> > > > selecting a default algorithm and a kernel parameter for overriding
> > > > it.  I assume the idea is that the distros can pick a reasonable
> > > > default and then the end users can override that if they have specific
> > > > requirements.  I'd want the same for SELinux.  If IMA is willing to
> > > > export its hash algorithm to external components, then I'm willing to
> > > > reuse that but not sure if that's a layering violation.
> > > With the new ima_measure_critical_data() hook, I agree with you and
> > > Casey it doesn't make sense for each caller to have to write their own
> > > function.  Casey suggested exporting IMA's hash function or defining a
> > > new common hash function.   There's nothing specific to IMA.
> > 
> > Except that no one is going to use the function unless they're
> > doing an IMA operation.
> 
> Can we do the following instead:
> 
> In ima_measure_critical_data() IMA hook, we can add another param for 
> the caller to indicate whether
> 
>   => The contents of "buf" needs to be measured
>      OR
>   => Hash of the contents of "buf" needs to be measured.
> 
> This way IMA doesn't need to export any new function to meet the hashing 
> requirement.

I'm not sure overloading the parameters is a good idea, but extending
ima_measure_critical_data() to calculate a simple buffer hash should be
fine.

Mimi

Re: [PATCH 2/2] SELinux: Measure state and hash of policy using IMA

[Lakshmi Ramasubramanian]

On 8/17/20 4:11 PM, Mimi Zohar wrote:
> On Mon, 2020-08-17 at 15:33 -0700, Lakshmi Ramasubramanian wrote:
>> On 8/17/20 3:00 PM, Casey Schaufler wrote:
>>> On 8/17/2020 2:31 PM, Mimi Zohar wrote:
>>>> On Thu, 2020-08-13 at 14:13 -0400, Stephen Smalley wrote:
>>>>> On Thu, Aug 13, 2020 at 2:03 PM Lakshmi Ramasubramanian
>>>>> <nramas@linux.microsoft.com> wrote:
>>>>>> On 8/13/20 10:58 AM, Stephen Smalley wrote:
>>>>>>> On Thu, Aug 13, 2020 at 1:52 PM Lakshmi Ramasubramanian
>>>>>>> <nramas@linux.microsoft.com> wrote:
>>>>>>>> On 8/13/20 10:42 AM, Stephen Smalley wrote:
>>>>>>>>
>>>>>>>>>> diff --git a/security/selinux/measure.c b/security/selinux/measure.c
>>>>>>>>>> new file mode 100644
>>>>>>>>>> index 000000000000..f21b7de4e2ae
>>>>>>>>>> --- /dev/null
>>>>>>>>>> +++ b/security/selinux/measure.c
>>>>>>>>>> @@ -0,0 +1,204 @@
>>>>>>>>>> +static int selinux_hash_buffer(void *buf, size_t buf_len,
>>>>>>>>>> +                   void **buf_hash, int *buf_hash_len)
>>>>>>>>>> +{
>>>>>>>>>> +    struct crypto_shash *tfm;
>>>>>>>>>> +    struct shash_desc *desc = NULL;
>>>>>>>>>> +    void *digest = NULL;
>>>>>>>>>> +    int desc_size;
>>>>>>>>>> +    int digest_size;
>>>>>>>>>> +    int ret = 0;
>>>>>>>>>> +
>>>>>>>>>> +    tfm = crypto_alloc_shash("sha256", 0, 0);
>>>>>>>>>> +    if (IS_ERR(tfm))
>>>>>>>>>> +        return PTR_ERR(tfm);
>>>>>>>>> Can we make the algorithm selectable via kernel parameter and/or writing
>>>>>>>>> to a new selinuxfs node?
>>>>>>>> I can add a kernel parameter to select this hash algorithm.
>>>>>>> Also can we provide a Kconfig option for the default value like IMA does?
>>>>>>>
>>>>>> Would we need both - Kconfig and kernel param?
>>>>>>
>>>>>> The other option is to provide an IMA function to return the current
>>>>>> hash algorithm used for measurement. That way a consistent hash
>>>>>> algorithm can be employed by both IMA and the callers. Would that be better?
>>>>> This is why I preferred just passing the serialized policy buffer to
>>>>> IMA and letting it handle the hashing.  But apparently that approach
>>>>> wouldn't fly.  IMA appears to support both a Kconfig option for
>>>>> selecting a default algorithm and a kernel parameter for overriding
>>>>> it.  I assume the idea is that the distros can pick a reasonable
>>>>> default and then the end users can override that if they have specific
>>>>> requirements.  I'd want the same for SELinux.  If IMA is willing to
>>>>> export its hash algorithm to external components, then I'm willing to
>>>>> reuse that but not sure if that's a layering violation.
>>>> With the new ima_measure_critical_data() hook, I agree with you and
>>>> Casey it doesn't make sense for each caller to have to write their own
>>>> function.  Casey suggested exporting IMA's hash function or defining a
>>>> new common hash function.   There's nothing specific to IMA.
>>>
>>> Except that no one is going to use the function unless they're
>>> doing an IMA operation.
>>
>> Can we do the following instead:
>>
>> In ima_measure_critical_data() IMA hook, we can add another param for
>> the caller to indicate whether
>>
>>    => The contents of "buf" needs to be measured
>>       OR
>>    => Hash of the contents of "buf" needs to be measured.
>>
>> This way IMA doesn't need to export any new function to meet the hashing
>> requirement.
> 
> I'm not sure overloading the parameters is a good idea, but extending
> ima_measure_critical_data() to calculate a simple buffer hash should be
> fine.
> 

Sorry I wasn't clear - I didn't mean to say overload existing 
parameters, but extending the IMA hook to calculate the hash of the 
buffer - like the following:

int ima_measure_critical_data(const char *event_name,
                               const char *event_data_source,
                               const void *buf, int buf_len,
                               bool measure_buf_hash);

If measure_buf_hash is true, IMA will calculate the hash of contents of 
"buf" and measure the hash.
Else, IMA will measure the contents of "buf".

  -lakshmi