ima: Move to LSM infrastructure

Move hardcoded IMA function calls (not appraisal-specific functions) from
various places in the kernel to the LSM infrastructure, by introducing a
new LSM named 'ima' (at the end of the LSM list and always enabled like
'integrity').

Having IMA before EVM in the Makefile is sufficient to preserve the
relative order of the new 'ima' LSM in respect to the upcoming 'evm' LSM,
and thus the order of IMA and EVM function calls as when they were
hardcoded.

Make moved functions as static (except ima_post_key_create_or_update(),
which is not in ima_main.c), and register them as implementation of the
respective hooks in the new function init_ima_lsm().

Select CONFIG_SECURITY_PATH, to ensure that the path-based LSM hook
path_post_mknod is always available and ima_post_path_mknod() is always
executed to mark files as new, as before the move.

A slight difference is that IMA and EVM functions registered for the
inode_post_setattr, inode_post_removexattr, path_post_mknod,
inode_post_create_tmpfile, inode_post_set_acl and inode_post_remove_acl
won't be executed for private inodes. Since those inodes are supposed to be
fs-internal, they should not be of interest to IMA or EVM. The S_PRIVATE
flag is used for anonymous inodes, hugetlbfs, reiserfs xattrs, XFS scrub
and kernel-internal tmpfs files.

Conditionally register ima_post_key_create_or_update() if
CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is enabled. Also, conditionally register
ima_kernel_module_request() if CONFIG_INTEGRITY_ASYMMETRIC_KEYS is enabled.

Finally, add the LSM_ID_IMA case in lsm_list_modules_test.c.

Signed-off-by: Roberto Sassu <[e-mail]>
Acked-by: Chuck Lever <[e-mail]>
Acked-by: Casey Schaufler <[e-mail]>
Acked-by: Christian Brauner <[e-mail]>
Reviewed-by: Stefan Berger <[e-mail]>
Reviewed-by: Mimi Zohar <[e-mail]>
Acked-by: Mimi Zohar <[e-mail]>
Signed-off-by: Paul Moore <[e-mail]>

fs/file_table.c

···
 #include <linux/percpu_counter.h>
 #include <linux/percpu.h>
 #include <linux/task_work.h>
-#include <linux/ima.h>
 #include <linux/swap.h>
 #include <linux/kmemleak.h>
 
···
 	locks_remove_file(file);
 
 	security_file_release(file);
-	ima_file_free(file);
 	if (unlikely(file->f_flags & FASYNC)) {
 		if (file->f_op->fasync)
 			file->f_op->fasync(-1, file, 0);

fs/namei.c

···
 #include <linux/fsnotify.h>
 #include <linux/personality.h>
 #include <linux/security.h>
-#include <linux/ima.h>
 #include <linux/syscalls.h>
 #include <linux/mount.h>
 #include <linux/audit.h>
···
 		error = vfs_open(&nd->path, file);
 	if (!error)
 		error = security_file_post_open(file, op->acc_mode);
-	if (!error)
-		error = ima_file_check(file, op->acc_mode);
 	if (!error && do_truncate)
 		error = handle_truncate(idmap, file);
 	if (unlikely(error > 0)) {
···
 		spin_unlock(&inode->i_lock);
 	}
 	security_inode_post_create_tmpfile(idmap, inode);
-	ima_post_create_tmpfile(idmap, inode);
 	return 0;
 }
 
···
 		case 0: case S_IFREG:
 			error = vfs_create(idmap, path.dentry->d_inode,
 					   dentry, mode, true);
-			if (!error)
-				ima_post_path_mknod(idmap, dentry);
 			break;
 		case S_IFCHR: case S_IFBLK:
 			error = vfs_mknod(idmap, path.dentry->d_inode,

fs/nfsd/vfs.c

···
 #include <linux/posix_acl_xattr.h>
 #include <linux/xattr.h>
 #include <linux/jhash.h>
-#include <linux/ima.h>
 #include <linux/pagemap.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
···
 	}
 
 	host_err = security_file_post_open(file, may_flags);
-	if (host_err) {
-		fput(file);
-		goto out;
-	}
-
-	host_err = ima_file_check(file, may_flags);
 	if (host_err) {
 		fput(file);
 		goto out;

fs/open.c

···
 #include <linux/audit.h>
 #include <linux/falloc.h>
 #include <linux/fs_struct.h>
-#include <linux/ima.h>
 #include <linux/dnotify.h>
 #include <linux/compat.h>
 #include <linux/mnt_idmapping.h>

include/linux/ima.h

···
 
 #ifdef CONFIG_IMA
 extern enum hash_algo ima_get_current_hash_algo(void);
-extern int ima_bprm_check(struct linux_binprm *bprm);
-extern int ima_file_check(struct file *file, int mask);
-extern void ima_post_create_tmpfile(struct mnt_idmap *idmap,
-				    struct inode *inode);
-extern void ima_file_free(struct file *file);
-extern int ima_file_mmap(struct file *file, unsigned long reqprot,
-			 unsigned long prot, unsigned long flags);
-extern int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
-			     unsigned long prot);
-extern int ima_load_data(enum kernel_load_data_id id, bool contents);
-extern int ima_post_load_data(char *buf, loff_t size,
-			      enum kernel_load_data_id id, char *description);
-extern int ima_read_file(struct file *file, enum kernel_read_file_id id,
-			 bool contents);
-extern int ima_post_read_file(struct file *file, char *buf, loff_t size,
-			      enum kernel_read_file_id id);
-extern void ima_post_path_mknod(struct mnt_idmap *idmap,
-				struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
 extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size);
 extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
···
 static inline enum hash_algo ima_get_current_hash_algo(void)
 {
 	return HASH_ALGO__LAST;
-}
-
-static inline int ima_bprm_check(struct linux_binprm *bprm)
-{
-	return 0;
-}
-
-static inline int ima_file_check(struct file *file, int mask)
-{
-	return 0;
-}
-
-static inline void ima_post_create_tmpfile(struct mnt_idmap *idmap,
-					   struct inode *inode)
-{
-}
-
-static inline void ima_file_free(struct file *file)
-{
-	return;
-}
-
-static inline int ima_file_mmap(struct file *file, unsigned long reqprot,
-				unsigned long prot, unsigned long flags)
-{
-	return 0;
-}
-
-static inline int ima_file_mprotect(struct vm_area_struct *vma,
-				    unsigned long reqprot, unsigned long prot)
-{
-	return 0;
-}
-
-static inline int ima_load_data(enum kernel_load_data_id id, bool contents)
-{
-	return 0;
-}
-
-static inline int ima_post_load_data(char *buf, loff_t size,
-				     enum kernel_load_data_id id,
-				     char *description)
-{
-	return 0;
-}
-
-static inline int ima_read_file(struct file *file, enum kernel_read_file_id id,
-				bool contents)
-{
-	return 0;
-}
-
-static inline int ima_post_read_file(struct file *file, char *buf, loff_t size,
-				     enum kernel_read_file_id id)
-{
-	return 0;
-}
-
-static inline void ima_post_path_mknod(struct mnt_idmap *idmap,
-				       struct dentry *dentry)
-{
-	return;
 }
 
 static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
···
 static inline void ima_add_kexec_buffer(struct kimage *image)
 {}
 #endif
-
-#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
-extern void ima_post_key_create_or_update(struct key *keyring,
-					  struct key *key,
-					  const void *payload, size_t plen,
-					  unsigned long flags, bool create);
-#else
-static inline void ima_post_key_create_or_update(struct key *keyring,
-						 struct key *key,
-						 const void *payload,
-						 size_t plen,
-						 unsigned long flags,
-						 bool create) {}
-#endif  /* CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS */
 
 #ifdef CONFIG_IMA_APPRAISE
 extern bool is_ima_appraise_enabled(void);
···
 	return false;
 }
 #endif /* CONFIG_IMA_APPRAISE && CONFIG_INTEGRITY_TRUSTED_KEYRING */
-
-#if defined(CONFIG_IMA) && defined(CONFIG_INTEGRITY_ASYMMETRIC_KEYS)
-extern int ima_kernel_module_request(char *kmod_name);
-#else
-static inline int ima_kernel_module_request(char *kmod_name)
-{
-	return 0;
-}
-
-#endif
 #endif /* _LINUX_IMA_H */

include/uapi/linux/lsm.h

···
 #define LSM_ID_LOCKDOWN		108
 #define LSM_ID_BPF		109
 #define LSM_ID_LANDLOCK		110
+#define LSM_ID_IMA		111
 
 /*
  * LSM_ATTR_XXX definitions identify different LSM attributes

security/integrity/Makefile

···
 integrity-$(CONFIG_LOAD_PPC_KEYS) += platform_certs/efi_parser.o \
                                      platform_certs/load_powerpc.o \
                                      platform_certs/keyring_handler.o
+# The relative order of the 'ima' and 'evm' LSMs depends on the order below.
 obj-$(CONFIG_IMA)			+= ima/
 obj-$(CONFIG_EVM)			+= evm/

security/integrity/ima/Kconfig

···
 	select CRYPTO_HMAC
 	select CRYPTO_SHA1
 	select CRYPTO_HASH_INFO
+	select SECURITY_PATH
 	select TCG_TPM if HAS_IOMEM
 	select TCG_TIS if TCG_TPM && X86
 	select TCG_CRB if TCG_TPM && ACPI

security/integrity/ima/ima.h

···
 static inline void ima_load_kexec_buffer(void) {}
 #endif /* CONFIG_HAVE_IMA_KEXEC */
 
+#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
+void ima_post_key_create_or_update(struct key *keyring, struct key *key,
+				   const void *payload, size_t plen,
+				   unsigned long flags, bool create);
+#endif
+
 /*
  * The default binary_runtime_measurements list format is defined as the
  * platform native format.  The canonical format is defined as little-endian.

security/integrity/ima/ima_main.c

···
  *
  * Flag files that changed, based on i_version
  */
-void ima_file_free(struct file *file)
+static void ima_file_free(struct file *file)
 {
 	struct inode *inode = file_inode(file);
 	struct integrity_iint_cache *iint;
···
  * On success return 0.  On integrity appraisal error, assuming the file
  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
  */
-int ima_file_mmap(struct file *file, unsigned long reqprot,
-		  unsigned long prot, unsigned long flags)
+static int ima_file_mmap(struct file *file, unsigned long reqprot,
+			 unsigned long prot, unsigned long flags)
 {
 	u32 secid;
 	int ret;
···
  *
  * On mprotect change success, return 0.  On failure, return -EACESS.
  */
-int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
-		      unsigned long prot)
+static int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
+			     unsigned long prot)
 {
 	struct ima_template_desc *template = NULL;
 	struct file *file;
···
  * On success return 0.  On integrity appraisal error, assuming the file
  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
  */
-int ima_bprm_check(struct linux_binprm *bprm)
+static int ima_bprm_check(struct linux_binprm *bprm)
 {
 	int ret;
 	u32 secid;
···
  * On success return 0.  On integrity appraisal error, assuming the file
  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
  */
-int ima_file_check(struct file *file, int mask)
+static int ima_file_check(struct file *file, int mask)
 {
 	u32 secid;
 
···
 				   mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
 					   MAY_APPEND), FILE_CHECK);
 }
-EXPORT_SYMBOL_GPL(ima_file_check);
 
 static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
 			    size_t buf_size)
···
  * Skip calling process_measurement(), but indicate which newly, created
  * tmpfiles are in policy.
  */
-void ima_post_create_tmpfile(struct mnt_idmap *idmap,
-			     struct inode *inode)
+static void ima_post_create_tmpfile(struct mnt_idmap *idmap,
+				    struct inode *inode)
+
 {
 	struct integrity_iint_cache *iint;
 	int must_appraise;
···
  * Mark files created via the mknodat syscall as new, so that the
  * file data can be written later.
  */
-void ima_post_path_mknod(struct mnt_idmap *idmap,
-			 struct dentry *dentry)
+static void ima_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry)
 {
 	struct integrity_iint_cache *iint;
 	struct inode *inode = dentry->d_inode;
···
  *
  * For permission return 0, otherwise return -EACCES.
  */
-int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
-		  bool contents)
+static int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
+			 bool contents)
 {
 	enum ima_hooks func;
 	u32 secid;
···
  * On success return 0.  On integrity appraisal error, assuming the file
  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
  */
-int ima_post_read_file(struct file *file, char *buf, loff_t size,
-		       enum kernel_read_file_id read_id)
+static int ima_post_read_file(struct file *file, char *buf, loff_t size,
+			      enum kernel_read_file_id read_id)
 {
 	enum ima_hooks func;
 	u32 secid;
···
  *
  * For permission return 0, otherwise return -EACCES.
  */
-int ima_load_data(enum kernel_load_data_id id, bool contents)
+static int ima_load_data(enum kernel_load_data_id id, bool contents)
 {
 	bool ima_enforce, sig_enforce;
 
···
  * On success return 0.  On integrity appraisal error, assuming the file
  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
  */
-int ima_post_load_data(char *buf, loff_t size,
-		       enum kernel_load_data_id load_id,
-		       char *description)
+static int ima_post_load_data(char *buf, loff_t size,
+			      enum kernel_load_data_id load_id,
+			      char *description)
 {
 	if (load_id == LOADING_FIRMWARE) {
 		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
···
  *
  * Return: Zero if it is safe to load the kernel module, -EINVAL otherwise.
  */
-int ima_kernel_module_request(char *kmod_name)
+static int ima_kernel_module_request(char *kmod_name)
 {
 	if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
 		return -EINVAL;
···
 
 	return error;
 }
+
+static struct security_hook_list ima_hooks[] __ro_after_init = {
+	LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
+	LSM_HOOK_INIT(file_post_open, ima_file_check),
+	LSM_HOOK_INIT(inode_post_create_tmpfile, ima_post_create_tmpfile),
+	LSM_HOOK_INIT(file_release, ima_file_free),
+	LSM_HOOK_INIT(mmap_file, ima_file_mmap),
+	LSM_HOOK_INIT(file_mprotect, ima_file_mprotect),
+	LSM_HOOK_INIT(kernel_load_data, ima_load_data),
+	LSM_HOOK_INIT(kernel_post_load_data, ima_post_load_data),
+	LSM_HOOK_INIT(kernel_read_file, ima_read_file),
+	LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file),
+	LSM_HOOK_INIT(path_post_mknod, ima_post_path_mknod),
+#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
+	LSM_HOOK_INIT(key_post_create_or_update, ima_post_key_create_or_update),
+#endif
+#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
+	LSM_HOOK_INIT(kernel_module_request, ima_kernel_module_request),
+#endif
+};
+
+static const struct lsm_id ima_lsmid = {
+	.name = "ima",
+	.id = LSM_ID_IMA,
+};
+
+static int __init init_ima_lsm(void)
+{
+	security_add_hooks(ima_hooks, ARRAY_SIZE(ima_hooks), &ima_lsmid);
+	return 0;
+}
+
+DEFINE_LSM(ima) = {
+	.name = "ima",
+	.init = init_ima_lsm,
+	.order = LSM_ORDER_LAST,
+};
 
 late_initcall(init_ima);	/* Start IMA after the TPM is available */

security/integrity/integrity.h

···
 #include <crypto/hash.h>
 #include <linux/key.h>
 #include <linux/audit.h>
+#include <linux/lsm_hooks.h>
 
 /* iint action cache flags */
 #define IMA_MEASURE		0x00000001

security/keys/key.c

···
 #include <linux/security.h>
 #include <linux/workqueue.h>
 #include <linux/random.h>
-#include <linux/ima.h>
 #include <linux/err.h>
 #include "internal.h"
 
···
 
 	security_key_post_create_or_update(keyring, key, payload, plen, flags,
 					   true);
-	ima_post_key_create_or_update(keyring, key, payload, plen,
-				      flags, true);
 
 	key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 
···
 
 	key_ref = __key_update(key_ref, &prep);
 
-	if (!IS_ERR(key_ref)) {
+	if (!IS_ERR(key_ref))
 		security_key_post_create_or_update(keyring, key, payload, plen,
 						   flags, false);
-		ima_post_key_create_or_update(keyring, key,
-					      payload, plen,
-					      flags, false);
-	}
 
 	goto error_free_prep;
 }

security/security.c

···
 	(IS_ENABLED(CONFIG_SECURITY_SAFESETID) ? 1 : 0) + \
 	(IS_ENABLED(CONFIG_SECURITY_LOCKDOWN_LSM) ? 1 : 0) + \
 	(IS_ENABLED(CONFIG_BPF_LSM) ? 1 : 0) + \
-	(IS_ENABLED(CONFIG_SECURITY_LANDLOCK) ? 1 : 0))
+	(IS_ENABLED(CONFIG_SECURITY_LANDLOCK) ? 1 : 0) + \
+	(IS_ENABLED(CONFIG_IMA) ? 1 : 0))
 
 /*
  * These are descriptions of the reasons that can be passed to the
···
  */
 int security_bprm_check(struct linux_binprm *bprm)
 {
-	int ret;
-
-	ret = call_int_hook(bprm_check_security, 0, bprm);
-	if (ret)
-		return ret;
-	return ima_bprm_check(bprm);
+	return call_int_hook(bprm_check_security, 0, bprm);
 }
 
 /**
···
 int security_mmap_file(struct file *file, unsigned long prot,
 		       unsigned long flags)
 {
-	unsigned long prot_adj = mmap_prot(file, prot);
-	int ret;
-
-	ret = call_int_hook(mmap_file, 0, file, prot, prot_adj, flags);
-	if (ret)
-		return ret;
-	return ima_file_mmap(file, prot, prot_adj, flags);
+	return call_int_hook(mmap_file, 0, file, prot, mmap_prot(file, prot),
+			     flags);
 }
 
 /**
···
 int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
 			   unsigned long prot)
 {
-	int ret;
-
-	ret = call_int_hook(file_mprotect, 0, vma, reqprot, prot);
-	if (ret)
-		return ret;
-	return ima_file_mprotect(vma, reqprot, prot);
+	return call_int_hook(file_mprotect, 0, vma, reqprot, prot);
 }
 
 /**
···
  */
 int security_kernel_module_request(char *kmod_name)
 {
-	int ret;
-
-	ret = call_int_hook(kernel_module_request, 0, kmod_name);
-	if (ret)
-		return ret;
-	return ima_kernel_module_request(kmod_name);
+	return call_int_hook(kernel_module_request, 0, kmod_name);
 }
 
 /**
···
 int security_kernel_read_file(struct file *file, enum kernel_read_file_id id,
 			      bool contents)
 {
-	int ret;
-
-	ret = call_int_hook(kernel_read_file, 0, file, id, contents);
-	if (ret)
-		return ret;
-	return ima_read_file(file, id, contents);
+	return call_int_hook(kernel_read_file, 0, file, id, contents);
 }
 EXPORT_SYMBOL_GPL(security_kernel_read_file);
 
···
 int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
 				   enum kernel_read_file_id id)
 {
-	int ret;
-
-	ret = call_int_hook(kernel_post_read_file, 0, file, buf, size, id);
-	if (ret)
-		return ret;
-	return ima_post_read_file(file, buf, size, id);
+	return call_int_hook(kernel_post_read_file, 0, file, buf, size, id);
 }
 EXPORT_SYMBOL_GPL(security_kernel_post_read_file);
 
···
  */
 int security_kernel_load_data(enum kernel_load_data_id id, bool contents)
 {
-	int ret;
-
-	ret = call_int_hook(kernel_load_data, 0, id, contents);
-	if (ret)
-		return ret;
-	return ima_load_data(id, contents);
+	return call_int_hook(kernel_load_data, 0, id, contents);
 }
 EXPORT_SYMBOL_GPL(security_kernel_load_data);
 
···
 				   enum kernel_load_data_id id,
 				   char *description)
 {
-	int ret;
-
-	ret = call_int_hook(kernel_post_load_data, 0, buf, size, id,
-			    description);
-	if (ret)
-		return ret;
-	return ima_post_load_data(buf, size, id, description);
+	return call_int_hook(kernel_post_load_data, 0, buf, size, id,
+			     description);
 }
 EXPORT_SYMBOL_GPL(security_kernel_post_load_data);
 

tools/testing/selftests/lsm/lsm_list_modules_test.c

···
 		case LSM_ID_LANDLOCK:
 			name = "landlock";
 			break;
+		case LSM_ID_IMA:
+			name = "ima";
+			break;
 		default:
 			name = "INVALID";
 			break;