diff options
Diffstat (limited to 'security/integrity')
| -rw-r--r-- | security/integrity/ima/Kconfig | 58 | ||||
| -rw-r--r-- | security/integrity/ima/ima.h | 1 | ||||
| -rw-r--r-- | security/integrity/ima/ima_main.c | 68 | ||||
| -rw-r--r-- | security/integrity/ima/ima_policy.c | 48 |
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); |