Re: [PATCH v4a 8/8] module: replace the existing LSM hook in init_module

From: Paul Moore
Date: Fri Jun 01 2018 - 18:29:09 EST

On Thu, May 31, 2018 at 11:23 AM, Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> wrote:
> Both the init_module and finit_module syscalls call either directly
> or indirectly the security_kernel_read_file LSM hook. This patch
> replaces the direct call in init_module with a call to the new
> security_kernel_load_data hook and makes the corresponding changes
> in SELinux, LoadPin, and IMA.
>
> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
> Cc: Jeff Vander Stoep <jeffv@xxxxxxxxxx>
> Cc: Paul Moore <paul@xxxxxxxxxxxxxx>
> Cc: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
>
> ---
> Changelog:
> - For SELinux, have both the security_kernel_read_file and
> security_kernel_load_data LSM hooks call selinux_kernel_read_file().
> - LoadPin: replace existing init_module LSM hook support with
> new security_kernel_load_data hook.
>
> kernel/module.c | 2 +-
> security/integrity/ima/ima_main.c | 24 ++++++++++--------------
> security/loadpin/loadpin.c | 15 +++++++++++++++
> security/selinux/hooks.c | 15 +++++++++++++++
> 4 files changed, 41 insertions(+), 15 deletions(-)

As mentioned in the previous iteration, I have no strong opinion on
the question of the LSM hooks, but the SELinux bits look okay to me.

Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>

> diff --git a/kernel/module.c b/kernel/module.c
> index ce8066b88178..b97c642b5b4d 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2879,7 +2879,7 @@ static int copy_module_from_user(const void __user *umod, unsigned long len,
> if (info->len < sizeof(*(info->hdr)))
> return -ENOEXEC;
>
> - err = security_kernel_read_file(NULL, READING_MODULE);
> + err = security_kernel_load_data(LOADING_MODULE);
> if (err)
> return err;
>
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 5a7696152982..cd33a2eff496 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -438,17 +438,6 @@ static int read_idmap[READING_MAX_ID] = {
> */
> int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
> {
> - bool sig_enforce = is_module_sig_enforced();
> -
> - if (!file && read_id == READING_MODULE) {
> - if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
> - (ima_appraise & IMA_APPRAISE_ENFORCE)) {
> - pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
> - return -EACCES; /* INTEGRITY_UNKNOWN */
> - }
> - return 0; /* We rely on module signature checking */
> - }
> -
> if (read_id == READING_FIRMWARE_PREALLOC_BUFFER) {
> if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
> (ima_appraise & IMA_APPRAISE_ENFORCE)) {
> @@ -487,9 +476,6 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> return 0;
> }
>
> - if (!file && read_id == READING_MODULE) /* MODULE_SIG_FORCE enabled */
> - return 0;
> -
> /* permit signed certs */
> if (!file && read_id == READING_X509_CERTIFICATE)
> return 0;
> @@ -518,6 +504,8 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> */
> int ima_load_data(enum kernel_load_data_id id)
> {
> + bool sig_enforce;
> +
> if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE)
> return 0;
>
> @@ -533,6 +521,14 @@ int ima_load_data(enum kernel_load_data_id id)
> pr_err("Prevent firmware sysfs fallback loading.\n");
> return -EACCES; /* INTEGRITY_UNKNOWN */
> }
> + break;
> + case LOADING_MODULE:
> + sig_enforce = is_module_sig_enforced();
> +
> + if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES)) {
> + pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
> + return -EACCES; /* INTEGRITY_UNKNOWN */
> + }
> default:
> break;
> }
> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
> index 5fa191252c8f..a9c07bfbc338 100644
> --- a/security/loadpin/loadpin.c
> +++ b/security/loadpin/loadpin.c
> @@ -173,9 +173,24 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id)
> return 0;
> }
>
> +static int loadpin_load_data(enum kernel_load_data_id id)
> +{
> + int rc = 0;
> +
> + switch (id) {
> + case LOADING_MODULE:
> + rc = loadpin_read_file(NULL, READING_MODULE);
> + default:
> + break;
> + }
> +
> + return rc;
> +}
> +
> static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(sb_free_security, loadpin_sb_free_security),
> LSM_HOOK_INIT(kernel_read_file, loadpin_read_file),
> + LSM_HOOK_INIT(kernel_load_data, loadpin_load_data),
> };
>
> void __init loadpin_add_hooks(void)
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 02ebd1585eaf..475aed9ee2c7 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -4059,6 +4059,20 @@ static int selinux_kernel_read_file(struct file *file,
> return rc;
> }
>
> +static int selinux_kernel_load_data(enum kernel_load_data_id id)
> +{
> + int rc = 0;
> +
> + switch (id) {
> + case LOADING_MODULE:
> + rc = selinux_kernel_module_from_file(NULL);
> + default:
> + break;
> + }
> +
> + return rc;
> +}
> +
> static int selinux_task_setpgid(struct task_struct *p, pid_t pgid)
> {
> return avc_has_perm(&selinux_state,
> @@ -6950,6 +6964,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(kernel_act_as, selinux_kernel_act_as),
> LSM_HOOK_INIT(kernel_create_files_as, selinux_kernel_create_files_as),
> LSM_HOOK_INIT(kernel_module_request, selinux_kernel_module_request),
> + LSM_HOOK_INIT(kernel_load_data, selinux_kernel_load_data),
> LSM_HOOK_INIT(kernel_read_file, selinux_kernel_read_file),
> LSM_HOOK_INIT(task_setpgid, selinux_task_setpgid),
> LSM_HOOK_INIT(task_getpgid, selinux_task_getpgid),
> --
> 2.7.5
>



--
paul moore
www.paul-moore.com