On 12/14/2023 9:08 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> As for IMA, move hardcoded EVM function calls from various places in the
> kernel to the LSM infrastructure, by introducing a new LSM named 'evm'
> (last and always enabled like 'ima'). The order in the Makefile ensures
> that 'evm' hooks are executed after 'ima' ones.
>
> Make EVM functions as static (except for evm_inode_init_security(), which
> is exported), and register them as hook implementations in init_evm_lsm().
>
> Unlike before (see commit to move IMA to the LSM infrastructure),
> evm_inode_post_setattr(), evm_inode_post_set_acl(),
> evm_inode_post_remove_acl(), and evm_inode_post_removexattr() are not
> executed for private inodes.
>
> Finally, add the LSM_ID_EVM case in lsm_list_modules_test.c
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
Reviewed-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> ---
> fs/attr.c | 2 -
> fs/posix_acl.c | 3 -
> fs/xattr.c | 2 -
> include/linux/evm.h | 107 ----------------
> include/uapi/linux/lsm.h | 1 +
> security/integrity/evm/evm_main.c | 115 +++++++++++++++---
> security/security.c | 41 ++-----
> .../selftests/lsm/lsm_list_modules_test.c | 3 +
> 8 files changed, 113 insertions(+), 161 deletions(-)
>
> diff --git a/fs/attr.c b/fs/attr.c
> index 38841f3ebbcb..b51bd7c9b4a7 100644
> --- a/fs/attr.c
> +++ b/fs/attr.c
> @@ -16,7 +16,6 @@
> #include <linux/fcntl.h>
> #include <linux/filelock.h>
> #include <linux/security.h>
> -#include <linux/evm.h>
>
> #include "internal.h"
>
> @@ -502,7 +501,6 @@ int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
> if (!error) {
> fsnotify_change(dentry, ia_valid);
> security_inode_post_setattr(idmap, dentry, ia_valid);
> - evm_inode_post_setattr(idmap, dentry, ia_valid);
> }
>
> return error;
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index e3fbe1a9f3f5..ae67479cd2b6 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -26,7 +26,6 @@
> #include <linux/mnt_idmapping.h>
> #include <linux/iversion.h>
> #include <linux/security.h>
> -#include <linux/evm.h>
> #include <linux/fsnotify.h>
> #include <linux/filelock.h>
>
> @@ -1138,7 +1137,6 @@ int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> if (!error) {
> fsnotify_xattr(dentry);
> security_inode_post_set_acl(dentry, acl_name, kacl);
> - evm_inode_post_set_acl(dentry, acl_name, kacl);
> }
>
> out_inode_unlock:
> @@ -1247,7 +1245,6 @@ int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> if (!error) {
> fsnotify_xattr(dentry);
> security_inode_post_remove_acl(idmap, dentry, acl_name);
> - evm_inode_post_remove_acl(idmap, dentry, acl_name);
> }
>
> out_inode_unlock:
> diff --git a/fs/xattr.c b/fs/xattr.c
> index f891c260a971..f8b643f91a98 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -16,7 +16,6 @@
> #include <linux/mount.h>
> #include <linux/namei.h>
> #include <linux/security.h>
> -#include <linux/evm.h>
> #include <linux/syscalls.h>
> #include <linux/export.h>
> #include <linux/fsnotify.h>
> @@ -557,7 +556,6 @@ __vfs_removexattr_locked(struct mnt_idmap *idmap,
>
> fsnotify_xattr(dentry);
> security_inode_post_removexattr(dentry, name);
> - evm_inode_post_removexattr(dentry, name);
>
> out:
> return error;
> diff --git a/include/linux/evm.h b/include/linux/evm.h
> index 437d4076a3b3..cb481eccc967 100644
> --- a/include/linux/evm.h
> +++ b/include/linux/evm.h
> @@ -21,44 +21,6 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry,
> void *xattr_value,
> size_t xattr_value_len,
> struct integrity_iint_cache *iint);
> -extern int evm_inode_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, struct iattr *attr);
> -extern void evm_inode_post_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, int ia_valid);
> -extern int evm_inode_setxattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *name,
> - const void *value, size_t size, int flags);
> -extern void evm_inode_post_setxattr(struct dentry *dentry,
> - const char *xattr_name,
> - const void *xattr_value,
> - size_t xattr_value_len,
> - int flags);
> -extern int evm_inode_removexattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *xattr_name);
> -extern void evm_inode_post_removexattr(struct dentry *dentry,
> - const char *xattr_name);
> -static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - evm_inode_post_removexattr(dentry, acl_name);
> -}
> -extern int evm_inode_set_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *acl_name,
> - struct posix_acl *kacl);
> -static inline int evm_inode_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - return evm_inode_set_acl(idmap, dentry, acl_name, NULL);
> -}
> -static inline void evm_inode_post_set_acl(struct dentry *dentry,
> - const char *acl_name,
> - struct posix_acl *kacl)
> -{
> - return evm_inode_post_setxattr(dentry, acl_name, NULL, 0, 0);
> -}
> -
> int evm_inode_init_security(struct inode *inode, struct inode *dir,
> const struct qstr *qstr, struct xattr *xattrs,
> int *xattr_count);
> @@ -93,75 +55,6 @@ static inline enum integrity_status evm_verifyxattr(struct dentry *dentry,
> }
> #endif
>
> -static inline int evm_inode_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, struct iattr *attr)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_setattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, int ia_valid)
> -{
> - return;
> -}
> -
> -static inline int evm_inode_setxattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *name,
> - const void *value, size_t size, int flags)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_setxattr(struct dentry *dentry,
> - const char *xattr_name,
> - const void *xattr_value,
> - size_t xattr_value_len,
> - int flags)
> -{
> - return;
> -}
> -
> -static inline int evm_inode_removexattr(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *xattr_name)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_removexattr(struct dentry *dentry,
> - const char *xattr_name)
> -{
> - return;
> -}
> -
> -static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - return;
> -}
> -
> -static inline int evm_inode_set_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *acl_name,
> - struct posix_acl *kacl)
> -{
> - return 0;
> -}
> -
> -static inline int evm_inode_remove_acl(struct mnt_idmap *idmap,
> - struct dentry *dentry,
> - const char *acl_name)
> -{
> - return 0;
> -}
> -
> -static inline void evm_inode_post_set_acl(struct dentry *dentry,
> - const char *acl_name,
> - struct posix_acl *kacl)
> -{
> - return;
> -}
> -
> static inline int evm_inode_init_security(struct inode *inode, struct inode *dir,
> const struct qstr *qstr,
> struct xattr *xattrs,
> diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
> index ee7d034255a9..825339bcd580 100644
> --- a/include/uapi/linux/lsm.h
> +++ b/include/uapi/linux/lsm.h
> @@ -62,6 +62,7 @@ struct lsm_ctx {
> #define LSM_ID_BPF 109
> #define LSM_ID_LANDLOCK 110
> #define LSM_ID_IMA 111
> +#define LSM_ID_EVM 112
>
> /*
> * LSM_ATTR_XXX definitions identify different LSM attributes
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index ea84a6f835ff..0cd014bfc093 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -566,9 +566,9 @@ static int evm_protect_xattr(struct mnt_idmap *idmap,
> * userspace from writing HMAC value. Writing 'security.evm' requires
> * requires CAP_SYS_ADMIN privileges.
> */
> -int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> - const char *xattr_name, const void *xattr_value,
> - size_t xattr_value_len, int flags)
> +static int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *xattr_name, const void *xattr_value,
> + size_t xattr_value_len, int flags)
> {
> const struct evm_ima_xattr_data *xattr_data = xattr_value;
>
> @@ -598,8 +598,8 @@ int evm_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
> * the current value is valid.
> */
> -int evm_inode_removexattr(struct mnt_idmap *idmap,
> - struct dentry *dentry, const char *xattr_name)
> +static int evm_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *xattr_name)
> {
> /* Policy permits modification of the protected xattrs even though
> * there's no HMAC key loaded
> @@ -649,9 +649,11 @@ static inline int evm_inode_set_acl_change(struct mnt_idmap *idmap,
> * Prevent modifying posix acls causing the EVM HMAC to be re-calculated
> * and 'security.evm' xattr updated, unless the existing 'security.evm' is
> * valid.
> + *
> + * Return: zero on success, -EPERM on failure.
> */
> -int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> - const char *acl_name, struct posix_acl *kacl)
> +static int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *acl_name, struct posix_acl *kacl)
> {
> enum integrity_status evm_status;
>
> @@ -690,6 +692,24 @@ int evm_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> return -EPERM;
> }
>
> +/**
> + * evm_inode_remove_acl - Protect the EVM extended attribute from posix acls
> + * @idmap: idmap of the mount
> + * @dentry: pointer to the affected dentry
> + * @acl_name: name of the posix acl
> + *
> + * Prevent removing posix acls causing the EVM HMAC to be re-calculated
> + * and 'security.evm' xattr updated, unless the existing 'security.evm' is
> + * valid.
> + *
> + * Return: zero on success, -EPERM on failure.
> + */
> +static int evm_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> + const char *acl_name)
> +{
> + return evm_inode_set_acl(idmap, dentry, acl_name, NULL);
> +}
> +
> static void evm_reset_status(struct inode *inode)
> {
> struct integrity_iint_cache *iint;
> @@ -738,9 +758,11 @@ bool evm_revalidate_status(const char *xattr_name)
> * __vfs_setxattr_noperm(). The caller of which has taken the inode's
> * i_mutex lock.
> */
> -void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
> - const void *xattr_value, size_t xattr_value_len,
> - int flags)
> +static void evm_inode_post_setxattr(struct dentry *dentry,
> + const char *xattr_name,
> + const void *xattr_value,
> + size_t xattr_value_len,
> + int flags)
> {
> if (!evm_revalidate_status(xattr_name))
> return;
> @@ -756,6 +778,21 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
> evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
> }
>
> +/**
> + * evm_inode_post_set_acl - Update the EVM extended attribute from posix acls
> + * @dentry: pointer to the affected dentry
> + * @acl_name: name of the posix acl
> + * @kacl: pointer to the posix acls
> + *
> + * Update the 'security.evm' xattr with the EVM HMAC re-calculated after setting
> + * posix acls.
> + */
> +static void evm_inode_post_set_acl(struct dentry *dentry, const char *acl_name,
> + struct posix_acl *kacl)
> +{
> + return evm_inode_post_setxattr(dentry, acl_name, NULL, 0, 0);
> +}
> +
> /**
> * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
> * @dentry: pointer to the affected dentry
> @@ -766,7 +803,8 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
> * No need to take the i_mutex lock here, as this function is called from
> * vfs_removexattr() which takes the i_mutex.
> */
> -void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
> +static void evm_inode_post_removexattr(struct dentry *dentry,
> + const char *xattr_name)
> {
> if (!evm_revalidate_status(xattr_name))
> return;
> @@ -782,6 +820,22 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
> evm_update_evmxattr(dentry, xattr_name, NULL, 0);
> }
>
> +/**
> + * evm_inode_post_remove_acl - Update the EVM extended attribute from posix acls
> + * @idmap: idmap of the mount
> + * @dentry: pointer to the affected dentry
> + * @acl_name: name of the posix acl
> + *
> + * Update the 'security.evm' xattr with the EVM HMAC re-calculated after
> + * removing posix acls.
> + */
> +static inline void evm_inode_post_remove_acl(struct mnt_idmap *idmap,
> + struct dentry *dentry,
> + const char *acl_name)
> +{
> + evm_inode_post_removexattr(dentry, acl_name);
> +}
> +
> static int evm_attr_change(struct mnt_idmap *idmap,
> struct dentry *dentry, struct iattr *attr)
> {
> @@ -805,8 +859,8 @@ static int evm_attr_change(struct mnt_idmap *idmap,
> * Permit update of file attributes when files have a valid EVM signature,
> * except in the case of them having an immutable portable signature.
> */
> -int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> - struct iattr *attr)
> +static int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> + struct iattr *attr)
> {
> unsigned int ia_valid = attr->ia_valid;
> enum integrity_status evm_status;
> @@ -853,8 +907,8 @@ int evm_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> * This function is called from notify_change(), which expects the caller
> * to lock the inode's i_mutex.
> */
> -void evm_inode_post_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> - int ia_valid)
> +static void evm_inode_post_setattr(struct mnt_idmap *idmap,
> + struct dentry *dentry, int ia_valid)
> {
> if (!evm_revalidate_status(NULL))
> return;
> @@ -964,4 +1018,35 @@ static int __init init_evm(void)
> return error;
> }
>
> +static struct security_hook_list evm_hooks[] __ro_after_init = {
> + LSM_HOOK_INIT(inode_setattr, evm_inode_setattr),
> + LSM_HOOK_INIT(inode_post_setattr, evm_inode_post_setattr),
> + LSM_HOOK_INIT(inode_setxattr, evm_inode_setxattr),
> + LSM_HOOK_INIT(inode_set_acl, evm_inode_set_acl),
> + LSM_HOOK_INIT(inode_post_set_acl, evm_inode_post_set_acl),
> + LSM_HOOK_INIT(inode_remove_acl, evm_inode_remove_acl),
> + LSM_HOOK_INIT(inode_post_remove_acl, evm_inode_post_remove_acl),
> + LSM_HOOK_INIT(inode_post_setxattr, evm_inode_post_setxattr),
> + LSM_HOOK_INIT(inode_removexattr, evm_inode_removexattr),
> + LSM_HOOK_INIT(inode_post_removexattr, evm_inode_post_removexattr),
> + LSM_HOOK_INIT(inode_init_security, evm_inode_init_security),
> +};
> +
> +static const struct lsm_id evm_lsmid = {
> + .name = "evm",
> + .id = LSM_ID_EVM,
> +};
> +
> +static int __init init_evm_lsm(void)
> +{
> + security_add_hooks(evm_hooks, ARRAY_SIZE(evm_hooks), &evm_lsmid);
> + return 0;
> +}
> +
> +DEFINE_LSM(evm) = {
> + .name = "evm",
> + .init = init_evm_lsm,
> + .order = LSM_ORDER_LAST,
> +};
> +
> late_initcall(init_evm);
> diff --git a/security/security.c b/security/security.c
> index d4ead59fb91f..18a70aa707ad 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -20,13 +20,13 @@
> #include <linux/kernel_read_file.h>
> #include <linux/lsm_hooks.h>
> #include <linux/integrity.h>
> -#include <linux/evm.h>
> #include <linux/fsnotify.h>
> #include <linux/mman.h>
> #include <linux/mount.h>
> #include <linux/personality.h>
> #include <linux/backing-dev.h>
> #include <linux/string.h>
> +#include <linux/xattr.h>
> #include <linux/msg.h>
> #include <net/flow.h>
>
> @@ -50,7 +50,8 @@
> (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_IMA) ? 1 : 0))
> + (IS_ENABLED(CONFIG_IMA) ? 1 : 0) + \
> + (IS_ENABLED(CONFIG_EVM) ? 1 : 0))
>
> /*
> * These are descriptions of the reasons that can be passed to the
> @@ -1740,10 +1741,6 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
> if (!xattr_count)
> goto out;
>
> - ret = evm_inode_init_security(inode, dir, qstr, new_xattrs,
> - &xattr_count);
> - if (ret)
> - goto out;
> ret = initxattrs(inode, new_xattrs, fs_data);
> out:
> for (; xattr_count > 0; xattr_count--)
> @@ -2235,14 +2232,9 @@ int security_inode_permission(struct inode *inode, int mask)
> int security_inode_setattr(struct mnt_idmap *idmap,
> struct dentry *dentry, struct iattr *attr)
> {
> - int ret;
> -
> if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> return 0;
> - ret = call_int_hook(inode_setattr, 0, idmap, dentry, attr);
> - if (ret)
> - return ret;
> - return evm_inode_setattr(idmap, dentry, attr);
> + return call_int_hook(inode_setattr, 0, idmap, dentry, attr);
> }
> EXPORT_SYMBOL_GPL(security_inode_setattr);
>
> @@ -2307,9 +2299,7 @@ int security_inode_setxattr(struct mnt_idmap *idmap,
>
> if (ret == 1)
> ret = cap_inode_setxattr(dentry, name, value, size, flags);
> - if (ret)
> - return ret;
> - return evm_inode_setxattr(idmap, dentry, name, value, size, flags);
> + return ret;
> }
>
> /**
> @@ -2328,15 +2318,10 @@ int security_inode_set_acl(struct mnt_idmap *idmap,
> struct dentry *dentry, const char *acl_name,
> struct posix_acl *kacl)
> {
> - int ret;
> -
> if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> return 0;
> - ret = call_int_hook(inode_set_acl, 0, idmap, dentry, acl_name,
> - kacl);
> - if (ret)
> - return ret;
> - return evm_inode_set_acl(idmap, dentry, acl_name, kacl);
> + return call_int_hook(inode_set_acl, 0, idmap, dentry, acl_name,
> + kacl);
> }
>
> /**
> @@ -2389,14 +2374,9 @@ int security_inode_get_acl(struct mnt_idmap *idmap,
> int security_inode_remove_acl(struct mnt_idmap *idmap,
> struct dentry *dentry, const char *acl_name)
> {
> - int ret;
> -
> if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> return 0;
> - ret = call_int_hook(inode_remove_acl, 0, idmap, dentry, acl_name);
> - if (ret)
> - return ret;
> - return evm_inode_remove_acl(idmap, dentry, acl_name);
> + return call_int_hook(inode_remove_acl, 0, idmap, dentry, acl_name);
> }
>
> /**
> @@ -2432,7 +2412,6 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name,
> if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
> return;
> call_void_hook(inode_post_setxattr, dentry, name, value, size, flags);
> - evm_inode_post_setxattr(dentry, name, value, size, flags);
> }
>
> /**
> @@ -2493,9 +2472,7 @@ int security_inode_removexattr(struct mnt_idmap *idmap,
> ret = call_int_hook(inode_removexattr, 1, idmap, dentry, name);
> if (ret == 1)
> ret = cap_inode_removexattr(idmap, dentry, name);
> - if (ret)
> - return ret;
> - return evm_inode_removexattr(idmap, dentry, name);
> + return ret;
> }
>
> /**
> diff --git a/tools/testing/selftests/lsm/lsm_list_modules_test.c b/tools/testing/selftests/lsm/lsm_list_modules_test.c
> index 17333787cb2f..4d5d4cee2586 100644
> --- a/tools/testing/selftests/lsm/lsm_list_modules_test.c
> +++ b/tools/testing/selftests/lsm/lsm_list_modules_test.c
> @@ -125,6 +125,9 @@ TEST(correct_lsm_list_modules)
> case LSM_ID_IMA:
> name = "ima";
> break;
> + case LSM_ID_EVM:
> + name = "evm";
> + break;
> default:
> name = "INVALID";
> break;
