[PATCH v17 15/21] security: add security_inode_setintegrity() hook

[Fan Wu <wufan@linux.microsoft.com>]

This patch introduces a new hook to save inode's integrity
data. For example, for fsverity enabled files, LSMs can use this hook to
save the verified fsverity builtin signature into the inode's security
blob, and LSMs can make access decisions based on the data inside
the signature, like the signer certificate.

Signed-off-by: Fan Wu <wufan@linux.microsoft.com>

--
v1-v14:
  + Not present

v15:
  + Introduced

v16:
  + Switch to call_int_hook()

v17:
  + Fix a typo
---
 include/linux/lsm_hook_defs.h |  2 ++
 include/linux/security.h      | 10 ++++++++++
 security/security.c           | 20 ++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index b391a7f13053..6f746dfdb28b 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -177,6 +177,8 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
 LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid)
 LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)
 LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name)
+LSM_HOOK(int, 0, inode_setintegrity, struct inode *inode,
+	 enum lsm_integrity_type type, const void *value, size_t size)
 LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir,
 	 struct kernfs_node *kn)
 LSM_HOOK(int, 0, file_permission, struct file *file, int mask)
diff --git a/include/linux/security.h b/include/linux/security.h
index 9e46b13a356c..703762b0c4ad 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -404,6 +404,9 @@ int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer
 void security_inode_getsecid(struct inode *inode, u32 *secid);
 int security_inode_copy_up(struct dentry *src, struct cred **new);
 int security_inode_copy_up_xattr(const char *name);
+int security_inode_setintegrity(struct inode *inode,
+				enum lsm_integrity_type type, const void *value,
+				size_t size);
 int security_kernfs_init_security(struct kernfs_node *kn_dir,
 				  struct kernfs_node *kn);
 int security_file_permission(struct file *file, int mask);
@@ -1020,6 +1023,13 @@ static inline int security_inode_copy_up(struct dentry *src, struct cred **new)
 	return 0;
 }
 
+static inline int security_inode_setintegrity(struct inode *inode,
+					      enum lsm_integrity_type type,
+					      const void *value, size_t size)
+{
+	return 0;
+}
+
 static inline int security_kernfs_init_security(struct kernfs_node *kn_dir,
 						struct kernfs_node *kn)
 {
diff --git a/security/security.c b/security/security.c
index 3a7724c3dd76..2c20635a589b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2681,6 +2681,26 @@ int security_inode_copy_up_xattr(const char *name)
 }
 EXPORT_SYMBOL(security_inode_copy_up_xattr);
 
+/**
+ * security_inode_setintegrity() - Set the inode's integrity data
+ * @inode: inode
+ * @type: type of integrity, e.g. hash digest, signature, etc
+ * @value: the integrity value
+ * @size: size of the integrity value
+ *
+ * Register a verified integrity measurement of a inode with LSMs.
+ * LSMs should free the previously saved data if @value is NULL.
+ *
+ * Return: Returns 0 on success, negative values on failure.
+ */
+int security_inode_setintegrity(struct inode *inode,
+				enum lsm_integrity_type type, const void *value,
+				size_t size)
+{
+	return call_int_hook(inode_setintegrity, inode, type, value, size);
+}
+EXPORT_SYMBOL(security_inode_setintegrity);
+
 /**
  * security_kernfs_init_security() - Init LSM context for a kernfs node
  * @kn_dir: parent kernfs node
-- 
2.44.0