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ima: prevent kexec_load syscall based on runtime secureboot flag

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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.

[zohar@linux.ibm.com: add missing mesage on kexec_load failure]
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Nayna Jain 2018-10-09 23:00:34 +05:30 committed by Mimi Zohar
parent 0914ade209
commit b5ca117365
1 changed files with 13 additions and 6 deletions
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19
security/integrity/ima/ima_main.c
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@ -505,20 +505,26 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
*/ */
int ima_load_data(enum kernel_load_data_id id) 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) ima_enforce =
return 0; (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
switch (id) { switch (id) {
case LOADING_KEXEC_IMAGE: case LOADING_KEXEC_IMAGE:
if (ima_appraise & IMA_APPRAISE_KEXEC) { if (IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
&& arch_ima_get_secureboot()) {
pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
return -EACCES;
}
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"); pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
return -EACCES; /* INTEGRITY_UNKNOWN */ return -EACCES; /* INTEGRITY_UNKNOWN */
} }
break; break;
case LOADING_FIRMWARE: 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"); pr_err("Prevent firmware sysfs fallback loading.\n");
return -EACCES; /* INTEGRITY_UNKNOWN */ return -EACCES; /* INTEGRITY_UNKNOWN */
} }
@ -526,7 +532,8 @@ int ima_load_data(enum kernel_load_data_id id)
case LOADING_MODULE: case LOADING_MODULE:
sig_enforce = is_module_sig_enforced(); 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"); pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
return -EACCES; /* INTEGRITY_UNKNOWN */ return -EACCES; /* INTEGRITY_UNKNOWN */
} }