[Cc'ing the kexec mailing list, and Seth]
On Wed, 2018-09-26 at 17:52 +0530, Nayna Jain wrote:
> When CONFIG_KEXEC_VERIFY_SIG is enabled, the kexec_file_load syscall
> requires the kexec'd kernel image to be signed. Distros are concerned
> about totally disabling the kexec_load syscall. As a compromise, the
> kexec_load syscall will only be disabled when CONFIG_KEXEC_VERIFY_SIG
> is configured and the system is booted with secureboot enabled.
>
> This patch disables the kexec_load syscall only for systems booted with
> secureboot enabled.
>
> Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
Nice!
Mimi
> ---
> security/integrity/ima/ima_main.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index dce0a8a217bb..bdb6e5563d05 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -505,20 +505,24 @@ 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;
> + bool ima_enforce, sig_enforce;
>
> - if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE)
> - return 0;
> + ima_enforce =
> + (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
>
> switch (id) {
> case LOADING_KEXEC_IMAGE:
> - if (ima_appraise & IMA_APPRAISE_KEXEC) {
> +#ifdef CONFIG_KEXEC_VERIFY_SIG
> + if (arch_ima_get_secureboot())
> + return -EACCES;
> +#endif
> + if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
> pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
> return -EACCES; /* INTEGRITY_UNKNOWN */
> }
> break;
> case LOADING_FIRMWARE:
> - if (ima_appraise & IMA_APPRAISE_FIRMWARE) {
> + if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE)) {
> pr_err("Prevent firmware sysfs fallback loading.\n");
> return -EACCES; /* INTEGRITY_UNKNOWN */
> }
> @@ -526,7 +530,8 @@ int ima_load_data(enum kernel_load_data_id id)
> case LOADING_MODULE:
> sig_enforce = is_module_sig_enforced();
>
> - if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES)) {
> + if (ima_enforce && (!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 */
> }
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