From: Nayna Jain nayna@linux.ibm.com
On secure boot enabled systems, a verified kernel may need to kexec additional kernels. For example, it may be used as a bootloader needing to kexec a target kernel or it may need to kexec a crashdump kernel. In such cases, it may want to verify the signature of the next kernel image.
It is further possible that the kernel image is signed with third party keys which are stored as platform or firmware keys in the 'db' variable. The kernel, however, can not directly verify these platform keys, and an administrator may therefore not want to trust them for arbitrary usage. In order to differentiate platform keys from other keys and provide the necessary separation of trust, the kernel needs an additional keyring to store platform keys.
This patch creates the new keyring called ".platform" to isolate keys provided by platform from keys by kernel. These keys are used to facilitate signature verification during kexec. Since the scope of this keyring is only the platform/firmware keys, it cannot be updated from userspace.
This keyring can be enabled by setting CONFIG_INTEGRITY_PLATFORM_KEYRING.
Signed-off-by: Nayna Jain nayna@linux.ibm.com Reviewed-by: Mimi Zohar zohar@linux.ibm.com Acked-by: Serge Hallyn serge@hallyn.com Reviewed-by: James Morris james.morris@microsoft.com Reviewed-by: Thiago Jung Bauermann bauerman@linux.ibm.com Signed-off-by: Mimi Zohar zohar@linux.ibm.com Signed-off-by: Zhang Tianxing zhangtianxing3@huawei.com --- security/integrity/Kconfig | 11 +++++ security/integrity/Makefile | 1 + security/integrity/digsig.c | 47 +++++++++++++------ security/integrity/integrity.h | 3 +- .../platform_certs/platform_keyring.c | 35 ++++++++++++++ 5 files changed, 81 insertions(+), 16 deletions(-) create mode 100644 security/integrity/platform_certs/platform_keyring.c
diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig index da9565891738..4b4d2aeef539 100644 --- a/security/integrity/Kconfig +++ b/security/integrity/Kconfig @@ -51,6 +51,17 @@ config INTEGRITY_TRUSTED_KEYRING .evm keyrings be signed by a key on the system trusted keyring.
+config INTEGRITY_PLATFORM_KEYRING + bool "Provide keyring for platform/firmware trusted keys" + depends on INTEGRITY_ASYMMETRIC_KEYS + depends on SYSTEM_BLACKLIST_KEYRING + depends on EFI + help + Provide a separate, distinct keyring for platform trusted keys, which + the kernel automatically populates during initialization from values + provided by the platform for verifying the kexec'ed kerned image + and, possibly, the initramfs signature. + config INTEGRITY_AUDIT bool "Enables integrity auditing support " depends on AUDIT diff --git a/security/integrity/Makefile b/security/integrity/Makefile index 04d6e462b079..046ffc1bb42d 100644 --- a/security/integrity/Makefile +++ b/security/integrity/Makefile @@ -9,6 +9,7 @@ integrity-y := iint.o integrity-$(CONFIG_INTEGRITY_AUDIT) += integrity_audit.o integrity-$(CONFIG_INTEGRITY_SIGNATURE) += digsig.o integrity-$(CONFIG_INTEGRITY_ASYMMETRIC_KEYS) += digsig_asymmetric.o +integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o
subdir-$(CONFIG_IMA) += ima obj-$(CONFIG_IMA) += ima/ diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c index 9bb0a7f2863e..9902fe1973ff 100644 --- a/security/integrity/digsig.c +++ b/security/integrity/digsig.c @@ -35,6 +35,7 @@ static const char *keyring_name[INTEGRITY_KEYRING_MAX] = { ".ima", #endif "_module", + ".platform", };
#ifdef CONFIG_INTEGRITY_TRUSTED_KEYRING @@ -79,26 +80,14 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen, return -EOPNOTSUPP; }
-int __init integrity_init_keyring(const unsigned int id) +static int __integrity_init_keyring(const unsigned int id, key_perm_t perm, + struct key_restriction *restriction) { const struct cred *cred = current_cred(); - struct key_restriction *restriction; int err = 0;
- if (!init_keyring) - return 0; - - restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL); - if (!restriction) - return -ENOMEM; - - restriction->check = restrict_link_to_ima; - keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0), - KGIDT_INIT(0), cred, - ((KEY_POS_ALL & ~KEY_POS_SETATTR) | - KEY_USR_VIEW | KEY_USR_READ | - KEY_USR_WRITE | KEY_USR_SEARCH), + KGIDT_INIT(0), cred, perm, KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL); if (IS_ERR(keyring[id])) { @@ -107,9 +96,37 @@ int __init integrity_init_keyring(const unsigned int id) keyring_name[id], err); keyring[id] = NULL; } + return err; }
+int __init integrity_init_keyring(const unsigned int id) +{ + struct key_restriction *restriction; + key_perm_t perm; + + perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW + | KEY_USR_READ | KEY_USR_SEARCH; + + if (id == INTEGRITY_KEYRING_PLATFORM) { + restriction = NULL; + goto out; + } + + if (!init_keyring) + return 0; + + restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL); + if (!restriction) + return -ENOMEM; + + restriction->check = restrict_link_to_ima; + perm |= KEY_USR_WRITE; + +out: + return __integrity_init_keyring(id, perm, restriction); +} + int __init integrity_load_x509(const unsigned int id, const char *path) { key_ref_t key; diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index 0ec55122363d..be5acd395d5f 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -142,7 +142,8 @@ int integrity_kernel_read(struct file *file, loff_t offset, #define INTEGRITY_KEYRING_EVM 0 #define INTEGRITY_KEYRING_IMA 1 #define INTEGRITY_KEYRING_MODULE 2 -#define INTEGRITY_KEYRING_MAX 3 +#define INTEGRITY_KEYRING_PLATFORM 3 +#define INTEGRITY_KEYRING_MAX 4
extern struct dentry *integrity_dir;
diff --git a/security/integrity/platform_certs/platform_keyring.c b/security/integrity/platform_certs/platform_keyring.c new file mode 100644 index 000000000000..79f80af5b470 --- /dev/null +++ b/security/integrity/platform_certs/platform_keyring.c @@ -0,0 +1,35 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Platform keyring for firmware/platform keys + * + * Copyright IBM Corporation, 2018 + * Author(s): Nayna Jain nayna@linux.ibm.com + */ + +#include <linux/export.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/cred.h> +#include <linux/err.h> +#include <linux/slab.h> +#include "../integrity.h" + +/* + * Create the trusted keyrings. + */ +static __init int platform_keyring_init(void) +{ + int rc; + + rc = integrity_init_keyring(INTEGRITY_KEYRING_PLATFORM); + if (rc) + return rc; + + pr_notice("Platform Keyring initialized\n"); + return 0; +} + +/* + * Must be initialised before we try and load the keys into the keyring. + */ +device_initcall(platform_keyring_init);