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authorLinus Torvalds <torvalds@linux-foundation.org>2018-08-15 10:25:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-15 10:25:26 -0700
commit92d4a03674b8c399c2f547580fa509db78226170 (patch)
treee5492e0214e31a10a79dbad6135a047f37721fc9 /security/integrity/ima
parent1eb46908b35dfbac0ec1848d4b1e39667e0187e9 (diff)
parent87ea58433208d17295e200d56be5e2a4fe4ce7d6 (diff)
Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull security subsystem updates from James Morris: - kstrdup() return value fix from Eric Biggers - Add new security_load_data hook to differentiate security checking of kernel-loaded binaries in the case of there being no associated file descriptor, from Mimi Zohar. - Add ability to IMA to specify a policy at build-time, rather than just via command line params or by loading a custom policy, from Mimi. - Allow IMA and LSMs to prevent sysfs firmware load fallback (e.g. if using signed firmware), from Mimi. - Allow IMA to deny loading of kexec kernel images, as they cannot be measured by IMA, from Mimi. * 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: security: check for kstrdup() failure in lsm_append() security: export security_kernel_load_data function ima: based on policy warn about loading firmware (pre-allocated buffer) module: replace the existing LSM hook in init_module ima: add build time policy ima: based on policy require signed firmware (sysfs fallback) firmware: add call to LSM hook before firmware sysfs fallback ima: based on policy require signed kexec kernel images kexec: add call to LSM hook in original kexec_load syscall security: define new LSM hook named security_kernel_load_data MAINTAINERS: remove the outdated "LINUX SECURITY MODULE (LSM) FRAMEWORK" entry
Diffstat (limited to 'security/integrity/ima')
-rw-r--r--security/integrity/ima/Kconfig58
-rw-r--r--security/integrity/ima/ima.h1
-rw-r--r--security/integrity/ima/ima_main.c68
-rw-r--r--security/integrity/ima/ima_policy.c48
4 files changed, 158 insertions, 17 deletions
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 6a8f67714c83..004919d9bf09 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -156,6 +156,64 @@ config IMA_APPRAISE
<http://linux-ima.sourceforge.net>
If unsure, say N.
+config IMA_APPRAISE_BUILD_POLICY
+ bool "IMA build time configured policy rules"
+ depends on IMA_APPRAISE && INTEGRITY_ASYMMETRIC_KEYS
+ default n
+ help
+ This option defines an IMA appraisal policy at build time, which
+ is enforced at run time without having to specify a builtin
+ policy name on the boot command line. The build time appraisal
+ policy rules persist after loading a custom policy.
+
+ Depending on the rules configured, this policy may require kernel
+ modules, firmware, the kexec kernel image, and/or the IMA policy
+ to be signed. Unsigned files might prevent the system from
+ booting or applications from working properly.
+
+config IMA_APPRAISE_REQUIRE_FIRMWARE_SIGS
+ bool "Appraise firmware signatures"
+ depends on IMA_APPRAISE_BUILD_POLICY
+ default n
+ help
+ This option defines a policy requiring all firmware to be signed,
+ including the regulatory.db. If both this option and
+ CFG80211_REQUIRE_SIGNED_REGDB are enabled, then both signature
+ verification methods are necessary.
+
+config IMA_APPRAISE_REQUIRE_KEXEC_SIGS
+ bool "Appraise kexec kernel image signatures"
+ depends on IMA_APPRAISE_BUILD_POLICY
+ default n
+ help
+ Enabling this rule will require all kexec'ed kernel images to
+ be signed and verified by a public key on the trusted IMA
+ keyring.
+
+ Kernel image signatures can not be verified by the original
+ kexec_load syscall. Enabling this rule will prevent its
+ usage.
+
+config IMA_APPRAISE_REQUIRE_MODULE_SIGS
+ bool "Appraise kernel modules signatures"
+ depends on IMA_APPRAISE_BUILD_POLICY
+ default n
+ help
+ Enabling this rule will require all kernel modules to be signed
+ and verified by a public key on the trusted IMA keyring.
+
+ Kernel module signatures can only be verified by IMA-appraisal,
+ via the finit_module syscall. Enabling this rule will prevent
+ the usage of the init_module syscall.
+
+config IMA_APPRAISE_REQUIRE_POLICY_SIGS
+ bool "Appraise IMA policy signature"
+ depends on IMA_APPRAISE_BUILD_POLICY
+ default n
+ help
+ Enabling this rule will require the IMA policy to be signed and
+ and verified by a key on the trusted IMA keyring.
+
config IMA_APPRAISE_BOOTPARAM
bool "ima_appraise boot parameter"
depends on IMA_APPRAISE
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e4c1a236976c..a597b2795d2d 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -232,6 +232,7 @@ int ima_policy_show(struct seq_file *m, void *v);
#define IMA_APPRAISE_MODULES 0x08
#define IMA_APPRAISE_FIRMWARE 0x10
#define IMA_APPRAISE_POLICY 0x20
+#define IMA_APPRAISE_KEXEC 0x40
#ifdef CONFIG_IMA_APPRAISE
int ima_appraise_measurement(enum ima_hooks func,
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index b286f37712d5..2d31921fbda4 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -429,16 +429,14 @@ void ima_post_path_mknod(struct dentry *dentry)
*/
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 */
- }
+ /*
+ * READING_FIRMWARE_PREALLOC_BUFFER
+ *
+ * Do devices using pre-allocated memory run the risk of the
+ * firmware being accessible to the device prior to the completion
+ * of IMA's signature verification any more than when using two
+ * buffers?
+ */
return 0;
}
@@ -472,14 +470,13 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
if (!file && read_id == READING_FIRMWARE) {
if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
- (ima_appraise & IMA_APPRAISE_ENFORCE))
+ (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+ pr_err("Prevent firmware loading_store.\n");
return -EACCES; /* INTEGRITY_UNKNOWN */
+ }
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;
@@ -496,6 +493,49 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
MAY_READ, func);
}
+/**
+ * ima_load_data - appraise decision based on policy
+ * @id: kernel load data caller identifier
+ *
+ * Callers of this LSM hook can not measure, appraise, or audit the
+ * data provided by userspace. Enforce policy rules requring a file
+ * signature (eg. kexec'ed kernel image).
+ *
+ * For permission return 0, otherwise return -EACCES.
+ */
+int ima_load_data(enum kernel_load_data_id id)
+{
+ bool sig_enforce;
+
+ if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE)
+ return 0;
+
+ switch (id) {
+ case LOADING_KEXEC_IMAGE:
+ if (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) {
+ 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;
+ }
+ return 0;
+}
+
static int __init init_ima(void)
{
int error;
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index cdcc9a7b4e24..1659abb344f9 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -49,6 +49,7 @@
int ima_policy_flag;
static int temp_ima_appraise;
+static int build_ima_appraise __ro_after_init;
#define MAX_LSM_RULES 6
enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
@@ -162,6 +163,25 @@ static struct ima_rule_entry default_appraise_rules[] __ro_after_init = {
#endif
};
+static struct ima_rule_entry build_appraise_rules[] __ro_after_init = {
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_MODULE_SIGS
+ {.action = APPRAISE, .func = MODULE_CHECK,
+ .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_FIRMWARE_SIGS
+ {.action = APPRAISE, .func = FIRMWARE_CHECK,
+ .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_KEXEC_SIGS
+ {.action = APPRAISE, .func = KEXEC_KERNEL_CHECK,
+ .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_POLICY_SIGS
+ {.action = APPRAISE, .func = POLICY_CHECK,
+ .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+};
+
static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
{.action = APPRAISE, .func = MODULE_CHECK,
.flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
@@ -435,7 +455,7 @@ void ima_update_policy_flag(void)
ima_policy_flag |= entry->action;
}
- ima_appraise |= temp_ima_appraise;
+ ima_appraise |= (build_ima_appraise | temp_ima_appraise);
if (!ima_appraise)
ima_policy_flag &= ~IMA_APPRAISE;
}
@@ -448,6 +468,8 @@ static int ima_appraise_flag(enum ima_hooks func)
return IMA_APPRAISE_FIRMWARE;
else if (func == POLICY_CHECK)
return IMA_APPRAISE_POLICY;
+ else if (func == KEXEC_KERNEL_CHECK)
+ return IMA_APPRAISE_KEXEC;
return 0;
}
@@ -486,8 +508,8 @@ void __init ima_init_policy(void)
}
/*
- * Insert the appraise rules requiring file signatures, prior to
- * any other appraise rules.
+ * Insert the builtin "secure_boot" policy rules requiring file
+ * signatures, prior to any other appraise rules.
*/
for (i = 0; i < secure_boot_entries; i++) {
list_add_tail(&secure_boot_rules[i].list, &ima_default_rules);
@@ -495,6 +517,26 @@ void __init ima_init_policy(void)
ima_appraise_flag(secure_boot_rules[i].func);
}
+ /*
+ * Insert the build time appraise rules requiring file signatures
+ * for both the initial and custom policies, prior to other appraise
+ * rules.
+ */
+ for (i = 0; i < ARRAY_SIZE(build_appraise_rules); i++) {
+ struct ima_rule_entry *entry;
+
+ if (!secure_boot_entries)
+ list_add_tail(&build_appraise_rules[i].list,
+ &ima_default_rules);
+
+ entry = kmemdup(&build_appraise_rules[i], sizeof(*entry),
+ GFP_KERNEL);
+ if (entry)
+ list_add_tail(&entry->list, &ima_policy_rules);
+ build_ima_appraise |=
+ ima_appraise_flag(build_appraise_rules[i].func);
+ }
+
for (i = 0; i < appraise_entries; i++) {
list_add_tail(&default_appraise_rules[i].list,
&ima_default_rules);