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To prevent verifying the kernel module appended signature
twice (finit_module), once by the module_sig_check() and again by IMA,
powerpc secure boot rules define an IMA architecture specific policy
rule only if CONFIG_MODULE_SIG_FORCE is not enabled. This,
unfortunately, does not take into account the ability of enabling
"sig_enforce" on the boot command line (module.sig_enforce=1).
Including the IMA module appraise rule results in failing the
finit_module syscall, unless the module signing public key is loaded
onto the IMA keyring.
This patch fixes secure boot policy rules to be based on
CONFIG_MODULE_SIG instead.
Fixes: 4238fad366 ("powerpc/ima: Add support to initialize ima policy rules")
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Link: https://lore.kernel.org/r/1588342612-14532-1-git-send-email-nayna@linux.ibm.com
79 lines
2.3 KiB
C
79 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2019 IBM Corporation
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* Author: Nayna Jain
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*/
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#include <linux/ima.h>
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#include <asm/secure_boot.h>
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bool arch_ima_get_secureboot(void)
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{
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return is_ppc_secureboot_enabled();
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}
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/*
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* The "secure_rules" are enabled only on "secureboot" enabled systems.
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* These rules verify the file signatures against known good values.
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* The "appraise_type=imasig|modsig" option allows the known good signature
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* to be stored as an xattr or as an appended signature.
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*
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* To avoid duplicate signature verification as much as possible, the IMA
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* policy rule for module appraisal is added only if CONFIG_MODULE_SIG
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* is not enabled.
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*/
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static const char *const secure_rules[] = {
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"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
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#ifndef CONFIG_MODULE_SIG
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"appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
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#endif
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NULL
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};
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/*
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* The "trusted_rules" are enabled only on "trustedboot" enabled systems.
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* These rules add the kexec kernel image and kernel modules file hashes to
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* the IMA measurement list.
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*/
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static const char *const trusted_rules[] = {
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"measure func=KEXEC_KERNEL_CHECK",
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"measure func=MODULE_CHECK",
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NULL
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};
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/*
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* The "secure_and_trusted_rules" contains rules for both the secure boot and
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* trusted boot. The "template=ima-modsig" option includes the appended
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* signature, when available, in the IMA measurement list.
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*/
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static const char *const secure_and_trusted_rules[] = {
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"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
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"measure func=MODULE_CHECK template=ima-modsig",
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"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
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#ifndef CONFIG_MODULE_SIG
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"appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
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#endif
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NULL
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};
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/*
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* Returns the relevant IMA arch-specific policies based on the system secure
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* boot state.
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*/
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const char *const *arch_get_ima_policy(void)
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{
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if (is_ppc_secureboot_enabled()) {
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if (IS_ENABLED(CONFIG_MODULE_SIG))
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set_module_sig_enforced();
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if (is_ppc_trustedboot_enabled())
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return secure_and_trusted_rules;
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else
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return secure_rules;
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} else if (is_ppc_trustedboot_enabled()) {
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return trusted_rules;
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}
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return NULL;
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}
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