From 099f26f22f5834ad744aee093ed4d11de13cac15 Mon Sep 17 00:00:00 2001 From: Eric Snowberg Date: Thu, 2 Mar 2023 11:46:52 -0500 Subject: [PATCH] integrity: machine keyring CA configuration Add machine keyring CA restriction options to control the type of keys that may be added to it. The motivation is separation of certificate signing from code signing keys. Subsquent work will limit certificates being loaded into the IMA keyring to code signing keys used for signature verification. When no restrictions are selected, all Machine Owner Keys (MOK) are added to the machine keyring. When CONFIG_INTEGRITY_CA_MACHINE_KEYRING is selected, the CA bit must be true. Also the key usage must contain keyCertSign, any other usage field may be set as well. When CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX is selected, the CA bit must be true. Also the key usage must contain keyCertSign and the digitialSignature usage may not be set. Signed-off-by: Eric Snowberg Acked-by: Mimi Zohar Reviewed-by: Jarkko Sakkinen Tested-by: Mimi Zohar Signed-off-by: Jarkko Sakkinen --- crypto/asymmetric_keys/restrict.c | 2 ++ security/integrity/Kconfig | 23 ++++++++++++++++++++++- security/integrity/digsig.c | 8 ++++++-- 3 files changed, 30 insertions(+), 3 deletions(-) diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c index 48457c6f33f9..276bdb627498 100644 --- a/crypto/asymmetric_keys/restrict.c +++ b/crypto/asymmetric_keys/restrict.c @@ -140,6 +140,8 @@ int restrict_link_by_ca(struct key *dest_keyring, return -ENOKEY; if (!test_bit(KEY_EFLAG_KEYCERTSIGN, &pkey->key_eflags)) return -ENOKEY; + if (!IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX)) + return 0; if (test_bit(KEY_EFLAG_DIGITALSIG, &pkey->key_eflags)) return -ENOKEY; diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig index 599429f99f99..ec6e0d789da1 100644 --- a/security/integrity/Kconfig +++ b/security/integrity/Kconfig @@ -68,13 +68,34 @@ config INTEGRITY_MACHINE_KEYRING depends on INTEGRITY_ASYMMETRIC_KEYS depends on SYSTEM_BLACKLIST_KEYRING depends on LOAD_UEFI_KEYS - depends on !IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY help If set, provide a keyring to which Machine Owner Keys (MOK) may be added. This keyring shall contain just MOK keys. Unlike keys in the platform keyring, keys contained in the .machine keyring will be trusted within the kernel. +config INTEGRITY_CA_MACHINE_KEYRING + bool "Enforce Machine Keyring CA Restrictions" + depends on INTEGRITY_MACHINE_KEYRING + default n + help + The .machine keyring can be configured to enforce CA restriction + on any key added to it. By default no restrictions are in place + and all Machine Owner Keys (MOK) are added to the machine keyring. + If enabled only CA keys are added to the machine keyring, all + other MOK keys load into the platform keyring. + +config INTEGRITY_CA_MACHINE_KEYRING_MAX + bool "Only CA keys without DigitialSignature usage set" + depends on INTEGRITY_CA_MACHINE_KEYRING + default n + help + When selected, only load CA keys are loaded into the machine + keyring that contain the CA bit set along with the keyCertSign + Usage field. Keys containing the digitialSignature Usage field + will not be loaded. The remaining MOK keys are loaded into the + .platform keyring. + config LOAD_UEFI_KEYS depends on INTEGRITY_PLATFORM_KEYRING depends on EFI diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c index f2193c531f4a..6f31ffe23c48 100644 --- a/security/integrity/digsig.c +++ b/security/integrity/digsig.c @@ -132,7 +132,8 @@ int __init integrity_init_keyring(const unsigned int id) | KEY_USR_READ | KEY_USR_SEARCH; if (id == INTEGRITY_KEYRING_PLATFORM || - id == INTEGRITY_KEYRING_MACHINE) { + (id == INTEGRITY_KEYRING_MACHINE && + !IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) { restriction = NULL; goto out; } @@ -144,7 +145,10 @@ int __init integrity_init_keyring(const unsigned int id) if (!restriction) return -ENOMEM; - restriction->check = restrict_link_to_ima; + if (id == INTEGRITY_KEYRING_MACHINE) + restriction->check = restrict_link_by_ca; + else + restriction->check = restrict_link_to_ima; /* * MOK keys can only be added through a read-only runtime services