Re: [PATCH RFC v15 16/21] security: add security_inode_setintegrity() hook

Paul Moore
2024-03-19T23:00:41Z

On Mar 15, 2024 Fan Wu <wufan@linux.microsoft.com> wrote:
>
> 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
>
> ---
> include/linux/lsm_hook_defs.h | 3 +++
> include/linux/security.h | 10 ++++++++++
> security/security.c | 28 ++++++++++++++++++++++++++++
> 3 files changed, 41 insertions(+)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 6808ae763913..c88587fc3691 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -177,6 +177,9 @@ 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_intgr_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 60b40b523d57..0885866b261e 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -405,6 +405,9 @@ 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_intgr_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);
> @@ -1021,6 +1024,13 @@ 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_intgr_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 8d88529ac904..c5d426d084ab 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2681,6 +2681,34 @@ 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 the LSM.
> + *
> + * Return: Returns 0 on success, negative values on failure.
> + */
> +int security_inode_setintegrity(struct inode *inode,
> + enum lsm_intgr_type type, const void *value,
> + size_t size)
> +{
> + int rc = 0;
> + struct security_hook_list *p;
> +
> + hlist_for_each_entry(p, &security_hook_heads.inode_setintegrity, list) {
> + rc = p->hook.inode_setintegrity(inode, type, value, size);
> + if (rc)
> + return rc;
> + }
> +
> + return LSM_RET_DEFAULT(inode_setintegrity);
> +}
> +EXPORT_SYMBOL(security_inode_setintegrity);

Same as the block device variant of this hook, we should convert this
to use the call_int_hook() macro unless there is a strong reason to
leave it open coded.

> /**
> * security_kernfs_init_security() - Init LSM context for a kernfs node
> * @kn_dir: parent kernfs node
> --
> 2.44.0

--
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