integrity: IMA policy (4af4662f) · Commits · e / devices / android_kernel_fairphone_FP5

Documentation/ABI/testing/ima_policy

0 → 100644

+61 −0

Original line number	Diff line number	Diff line
		What: security/ima/policy
		Date: May 2008
		Contact: Mimi Zohar <zohar@us.ibm.com>
		Description:
		The Trusted Computing Group(TCG) runtime Integrity
		Measurement Architecture(IMA) maintains a list of hash
		values of executables and other sensitive system files
		loaded into the run-time of this system. At runtime,
		the policy can be constrained based on LSM specific data.
		Policies are loaded into the securityfs file ima/policy
		by opening the file, writing the rules one at a time and
		then closing the file. The new policy takes effect after
		the file ima/policy is closed.

		rule format: action [condition ...]

		action: measure \| dont_measure
		condition:= base \| lsm
		base: [[func=] [mask=] [fsmagic=] [uid=]]
		lsm: [[subj_user=] [subj_role=] [subj_type=]
		[obj_user=] [obj_role=] [obj_type=]]

		base: func:= [BPRM_CHECK][FILE_MMAP][INODE_PERMISSION]
		mask:= [MAY_READ] [MAY_WRITE] [MAY_APPEND] [MAY_EXEC]
		fsmagic:= hex value
		uid:= decimal value
		lsm: are LSM specific

		default policy:
		# PROC_SUPER_MAGIC
		dont_measure fsmagic=0x9fa0
		# SYSFS_MAGIC
		dont_measure fsmagic=0x62656572
		# DEBUGFS_MAGIC
		dont_measure fsmagic=0x64626720
		# TMPFS_MAGIC
		dont_measure fsmagic=0x01021994
		# SECURITYFS_MAGIC
		dont_measure fsmagic=0x73636673

		measure func=BPRM_CHECK
		measure func=FILE_MMAP mask=MAY_EXEC
		measure func=INODE_PERM mask=MAY_READ uid=0

		The default policy measures all executables in bprm_check,
		all files mmapped executable in file_mmap, and all files
		open for read by root in inode_permission.

		Examples of LSM specific definitions:

		SELinux:
		# SELINUX_MAGIC
		dont_measure fsmagic=0xF97CFF8C

		dont_measure obj_type=var_log_t
		dont_measure obj_type=auditd_log_t
		measure subj_user=system_u func=INODE_PERM mask=MAY_READ
		measure subj_role=system_r func=INODE_PERM mask=MAY_READ

		Smack:
		measure subj_user=_ func=INODE_PERM mask=MAY_READ

security/integrity/ima/Kconfig

+6 −0

Original line number	Diff line number	Diff line
		@@ -47,3 +47,9 @@ config IMA_AUDIT
		auditing messages can be enabled with 'ima_audit=1' on
		the kernel command line.

		config IMA_LSM_RULES
		bool
		depends on IMA && (SECURITY_SELINUX \|\| SECURITY_SMACK)
		default y
		help
		Disabling this option will disregard LSM based policy rules

security/integrity/ima/ima.h

+24 −0

Original line number	Diff line number	Diff line
		@@ -137,4 +137,28 @@ enum ima_hooks { PATH_CHECK = 1, FILE_MMAP, BPRM_CHECK };
		int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask);
		void ima_init_policy(void);
		void ima_update_policy(void);
		int ima_parse_add_rule(char *);
		void ima_delete_rules(void);

		/* LSM based policy rules require audit */
		#ifdef CONFIG_IMA_LSM_RULES

		#define security_filter_rule_init security_audit_rule_init
		#define security_filter_rule_match security_audit_rule_match

		#else

		static inline int security_filter_rule_init(u32 field, u32 op, char *rulestr,
		void **lsmrule)
		{
		return -EINVAL;
		}

		static inline int security_filter_rule_match(u32 secid, u32 field, u32 op,
		void *lsmrule,
		struct audit_context *actx)
		{
		return -EINVAL;
		}
		#endif /* CONFIG_IMA_LSM_RULES */
		#endif

security/integrity/ima/ima_fs.c

+66 −1

Original line number	Diff line number	Diff line
		@@ -19,9 +19,11 @@
		#include <linux/seq_file.h>
		#include <linux/rculist.h>
		#include <linux/rcupdate.h>
		#include <linux/parser.h>

		#include "ima.h"

		static int valid_policy = 1;
		#define TMPBUFLEN 12
		static ssize_t ima_show_htable_value(char __user *buf, size_t count,
		loff_t ppos, atomic_long_t val)
		@@ -237,11 +239,66 @@ static struct file_operations ima_ascii_measurements_ops = {
		.release = seq_release,
		};

		static ssize_t ima_write_policy(struct file file, const char __user buf,
		size_t datalen, loff_t *ppos)
		{
		char *data;
		int rc;

		if (datalen >= PAGE_SIZE)
		return -ENOMEM;
		if (*ppos != 0) {
		/* No partial writes. */
		return -EINVAL;
		}
		data = kmalloc(datalen + 1, GFP_KERNEL);
		if (!data)
		return -ENOMEM;

		if (copy_from_user(data, buf, datalen)) {
		kfree(data);
		return -EFAULT;
		}
		*(data + datalen) = '\0';
		rc = ima_parse_add_rule(data);
		if (rc < 0) {
		datalen = -EINVAL;
		valid_policy = 0;
		}

		kfree(data);
		return datalen;
		}

		static struct dentry *ima_dir;
		static struct dentry *binary_runtime_measurements;
		static struct dentry *ascii_runtime_measurements;
		static struct dentry *runtime_measurements_count;
		static struct dentry *violations;
		static struct dentry *ima_policy;

		/*
		* ima_release_policy - start using the new measure policy rules.
		*
		* Initially, ima_measure points to the default policy rules, now
		* point to the new policy rules, and remove the securityfs policy file.
		*/
		static int ima_release_policy(struct inode inode, struct file file)
		{
		if (!valid_policy) {
		ima_delete_rules();
		return 0;
		}
		ima_update_policy();
		securityfs_remove(ima_policy);
		ima_policy = NULL;
		return 0;
		}

		static struct file_operations ima_measure_policy_ops = {
		.write = ima_write_policy,
		.release = ima_release_policy
		};

		int ima_fs_init(void)
		{
		@@ -276,13 +333,20 @@ int ima_fs_init(void)
		if (IS_ERR(violations))
		goto out;

		return 0;
		ima_policy = securityfs_create_file("policy",
		S_IRUSR \| S_IRGRP \| S_IWUSR,
		ima_dir, NULL,
		&ima_measure_policy_ops);
		if (IS_ERR(ima_policy))
		goto out;

		return 0;
		out:
		securityfs_remove(runtime_measurements_count);
		securityfs_remove(ascii_runtime_measurements);
		securityfs_remove(binary_runtime_measurements);
		securityfs_remove(ima_dir);
		securityfs_remove(ima_policy);
		return -1;
		}

		@@ -293,4 +357,5 @@ void __exit ima_fs_cleanup(void)
		securityfs_remove(ascii_runtime_measurements);
		securityfs_remove(binary_runtime_measurements);
		securityfs_remove(ima_dir);
		securityfs_remove(ima_policy);
		}

security/integrity/ima/ima_policy.c

+290 −3

Original line number	Diff line number	Diff line
		@@ -15,6 +15,7 @@
		#include <linux/audit.h>
		#include <linux/security.h>
		#include <linux/magic.h>
		#include <linux/parser.h>

		#include "ima.h"

		@@ -24,7 +25,12 @@
		#define IMA_FSMAGIC 0x0004
		#define IMA_UID 0x0008

		enum ima_action { DONT_MEASURE, MEASURE };
		enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };

		#define MAX_LSM_RULES 6
		enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
		LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
		};

		struct ima_measure_rule_entry {
		struct list_head list;
		@@ -34,8 +40,15 @@ struct ima_measure_rule_entry {
		int mask;
		unsigned long fsmagic;
		uid_t uid;
		struct {
		void rule; / LSM file metadata specific */
		int type; /* audit type */
		} lsm[MAX_LSM_RULES];
		};

		/* Without LSM specific knowledge, the default policy can only be
		* written in terms of .action, .func, .mask, .fsmagic, and .uid
		*/
		static struct ima_measure_rule_entry default_rules[] = {
		{.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,
		.flags = IMA_FSMAGIC},
		@@ -54,8 +67,11 @@ static struct ima_measure_rule_entry default_rules[] = {
		};

		static LIST_HEAD(measure_default_rules);
		static LIST_HEAD(measure_policy_rules);
		static struct list_head *ima_measure;

		static DEFINE_MUTEX(ima_measure_mutex);

		/**
		* ima_match_rules - determine whether an inode matches the measure rule.
		* @rule: a pointer to a rule
		@@ -69,6 +85,7 @@ static bool ima_match_rules(struct ima_measure_rule_entry *rule,
		struct inode *inode, enum ima_hooks func, int mask)
		{
		struct task_struct *tsk = current;
		int i;

		if ((rule->flags & IMA_FUNC) && rule->func != func)
		return false;
		@@ -79,6 +96,39 @@ static bool ima_match_rules(struct ima_measure_rule_entry *rule,
		return false;
		if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
		return false;
		for (i = 0; i < MAX_LSM_RULES; i++) {
		int rc;
		u32 osid, sid;

		if (!rule->lsm[i].rule)
		continue;

		switch (i) {
		case LSM_OBJ_USER:
		case LSM_OBJ_ROLE:
		case LSM_OBJ_TYPE:
		security_inode_getsecid(inode, &osid);
		rc = security_filter_rule_match(osid,
		rule->lsm[i].type,
		AUDIT_EQUAL,
		rule->lsm[i].rule,
		NULL);
		break;
		case LSM_SUBJ_USER:
		case LSM_SUBJ_ROLE:
		case LSM_SUBJ_TYPE:
		security_task_getsecid(tsk, &sid);
		rc = security_filter_rule_match(sid,
		rule->lsm[i].type,
		AUDIT_EQUAL,
		rule->lsm[i].rule,
		NULL);
		default:
		break;
		}
		if (!rc)
		return false;
		}
		return true;
		}

		@@ -112,9 +162,8 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
		/**
		* ima_init_policy - initialize the default measure rules.
		*
		* (Could use the default_rules directly, but in policy patch
		* ima_measure points to either the measure_default_rules or the
		* the new measure_policy_rules.)
		* the new measure_policy_rules.
		*/
		void ima_init_policy(void)
		{
		@@ -124,3 +173,241 @@ void ima_init_policy(void)
		list_add_tail(&default_rules[i].list, &measure_default_rules);
		ima_measure = &measure_default_rules;
		}

		/**
		* ima_update_policy - update default_rules with new measure rules
		*
		* Called on file .release to update the default rules with a complete new
		* policy. Once updated, the policy is locked, no additional rules can be
		* added to the policy.
		*/
		void ima_update_policy(void)
		{
		const char *op = "policy_update";
		const char *cause = "already exists";
		int result = 1;
		int audit_info = 0;

		if (ima_measure == &measure_default_rules) {
		ima_measure = &measure_policy_rules;
		cause = "complete";
		result = 0;
		}
		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
		NULL, op, cause, result, audit_info);
		}

		enum {
		Opt_err = -1,
		Opt_measure = 1, Opt_dont_measure,
		Opt_obj_user, Opt_obj_role, Opt_obj_type,
		Opt_subj_user, Opt_subj_role, Opt_subj_type,
		Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
		};

		static match_table_t policy_tokens = {
		{Opt_measure, "measure"},
		{Opt_dont_measure, "dont_measure"},
		{Opt_obj_user, "obj_user=%s"},
		{Opt_obj_role, "obj_role=%s"},
		{Opt_obj_type, "obj_type=%s"},
		{Opt_subj_user, "subj_user=%s"},
		{Opt_subj_role, "subj_role=%s"},
		{Opt_subj_type, "subj_type=%s"},
		{Opt_func, "func=%s"},
		{Opt_mask, "mask=%s"},
		{Opt_fsmagic, "fsmagic=%s"},
		{Opt_uid, "uid=%s"},
		{Opt_err, NULL}
		};

		static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
		char *args, int lsm_rule, int audit_type)
		{
		int result;

		entry->lsm[lsm_rule].type = audit_type;
		result = security_filter_rule_init(entry->lsm[lsm_rule].type,
		AUDIT_EQUAL, args,
		&entry->lsm[lsm_rule].rule);
		return result;
		}

		static int ima_parse_rule(char rule, struct ima_measure_rule_entry entry)
		{
		struct audit_buffer *ab;
		char *p;
		int result = 0;

		ab = audit_log_start(current->audit_context, GFP_KERNEL,
		AUDIT_INTEGRITY_STATUS);

		entry->action = -1;
		while ((p = strsep(&rule, " \n")) != NULL) {
		substring_t args[MAX_OPT_ARGS];
		int token;
		unsigned long lnum;

		if (result < 0)
		break;
		if (!*p)
		continue;
		token = match_token(p, policy_tokens, args);
		switch (token) {
		case Opt_measure:
		audit_log_format(ab, "%s ", "measure");
		entry->action = MEASURE;
		break;
		case Opt_dont_measure:
		audit_log_format(ab, "%s ", "dont_measure");
		entry->action = DONT_MEASURE;
		break;
		case Opt_func:
		audit_log_format(ab, "func=%s ", args[0].from);
		if (strcmp(args[0].from, "PATH_CHECK") == 0)
		entry->func = PATH_CHECK;
		else if (strcmp(args[0].from, "FILE_MMAP") == 0)
		entry->func = FILE_MMAP;
		else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
		entry->func = BPRM_CHECK;
		else
		result = -EINVAL;
		if (!result)
		entry->flags \|= IMA_FUNC;
		break;
		case Opt_mask:
		audit_log_format(ab, "mask=%s ", args[0].from);
		if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
		entry->mask = MAY_EXEC;
		else if (strcmp(args[0].from, "MAY_WRITE") == 0)
		entry->mask = MAY_WRITE;
		else if (strcmp(args[0].from, "MAY_READ") == 0)
		entry->mask = MAY_READ;
		else if (strcmp(args[0].from, "MAY_APPEND") == 0)
		entry->mask = MAY_APPEND;
		else
		result = -EINVAL;
		if (!result)
		entry->flags \|= IMA_MASK;
		break;
		case Opt_fsmagic:
		audit_log_format(ab, "fsmagic=%s ", args[0].from);
		result = strict_strtoul(args[0].from, 16,
		&entry->fsmagic);
		if (!result)
		entry->flags \|= IMA_FSMAGIC;
		break;
		case Opt_uid:
		audit_log_format(ab, "uid=%s ", args[0].from);
		result = strict_strtoul(args[0].from, 10, &lnum);
		if (!result) {
		entry->uid = (uid_t) lnum;
		if (entry->uid != lnum)
		result = -EINVAL;
		else
		entry->flags \|= IMA_UID;
		}
		break;
		case Opt_obj_user:
		audit_log_format(ab, "obj_user=%s ", args[0].from);
		result = ima_lsm_rule_init(entry, args[0].from,
		LSM_OBJ_USER,
		AUDIT_OBJ_USER);
		break;
		case Opt_obj_role:
		audit_log_format(ab, "obj_role=%s ", args[0].from);
		result = ima_lsm_rule_init(entry, args[0].from,
		LSM_OBJ_ROLE,
		AUDIT_OBJ_ROLE);
		break;
		case Opt_obj_type:
		audit_log_format(ab, "obj_type=%s ", args[0].from);
		result = ima_lsm_rule_init(entry, args[0].from,
		LSM_OBJ_TYPE,
		AUDIT_OBJ_TYPE);
		break;
		case Opt_subj_user:
		audit_log_format(ab, "subj_user=%s ", args[0].from);
		result = ima_lsm_rule_init(entry, args[0].from,
		LSM_SUBJ_USER,
		AUDIT_SUBJ_USER);
		break;
		case Opt_subj_role:
		audit_log_format(ab, "subj_role=%s ", args[0].from);
		result = ima_lsm_rule_init(entry, args[0].from,
		LSM_SUBJ_ROLE,
		AUDIT_SUBJ_ROLE);
		break;
		case Opt_subj_type:
		audit_log_format(ab, "subj_type=%s ", args[0].from);
		result = ima_lsm_rule_init(entry, args[0].from,
		LSM_SUBJ_TYPE,
		AUDIT_SUBJ_TYPE);
		break;
		case Opt_err:
		printk(KERN_INFO "%s: unknown token: %s\n",
		__FUNCTION__, p);
		break;
		}
		}
		if (entry->action == UNKNOWN)
		result = -EINVAL;

		audit_log_format(ab, "res=%d", result);
		audit_log_end(ab);
		return result;
		}

		/**
		* ima_parse_add_rule - add a rule to measure_policy_rules
		* @rule - ima measurement policy rule
		*
		* Uses a mutex to protect the policy list from multiple concurrent writers.
		* Returns 0 on success, an error code on failure.
		*/
		int ima_parse_add_rule(char *rule)
		{
		const char *op = "add_rule";
		struct ima_measure_rule_entry *entry;
		int result = 0;
		int audit_info = 0;

		/* Prevent installed policy from changing */
		if (ima_measure != &measure_default_rules) {
		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
		NULL, op, "already exists",
		-EACCES, audit_info);
		return -EACCES;
		}

		entry = kzalloc(sizeof(*entry), GFP_KERNEL);
		if (!entry) {
		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
		NULL, op, "-ENOMEM", -ENOMEM, audit_info);
		return -ENOMEM;
		}

		INIT_LIST_HEAD(&entry->list);

		result = ima_parse_rule(rule, entry);
		if (!result) {
		mutex_lock(&ima_measure_mutex);
		list_add_tail(&entry->list, &measure_policy_rules);
		mutex_unlock(&ima_measure_mutex);
		} else
		kfree(entry);
		return result;
		}

		/* ima_delete_rules called to cleanup invalid policy */
		void ima_delete_rules()
		{
		struct ima_measure_rule_entry entry, tmp;

		mutex_lock(&ima_measure_mutex);
		list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
		list_del(&entry->list);
		kfree(entry);
		}
		mutex_unlock(&ima_measure_mutex);
		}