linux/certs/Kconfig

# SPDX-License-Identifier: GPL-2.0
menu "Certificates for signature checking"

config MODULE_SIG_KEY
	string "File name or PKCS#11 URI of module signing key"
	default "certs/signing_key.pem"
	depends on MODULE_SIG || (IMA_APPRAISE_MODSIG && MODULES)
	help
         Provide the file name of a private key/certificate in PEM format,
         or a PKCS#11 URI according to RFC7512. The file should contain, or
         the URI should identify, both the certificate and its corresponding
         private key.

         If this option is unchanged from its default "certs/signing_key.pem",
         then the kernel will automatically generate the private key and
         certificate as described in Documentation/admin-guide/module-signing.rst

choice
	prompt "Type of module signing key to be generated"
	depends on MODULE_SIG || (IMA_APPRAISE_MODSIG && MODULES)
	help
	 The type of module signing key type to generate. This option
	 does not apply if a #PKCS11 URI is used.

config MODULE_SIG_KEY_TYPE_RSA
	bool "RSA"
	help
	 Use an RSA key for module signing.

config MODULE_SIG_KEY_TYPE_ECDSA
	bool "ECDSA"
	select CRYPTO_ECDSA
	depends on !(MODULE_SIG_SHA256 || MODULE_SIG_SHA3_256)
	help
	 Use an elliptic curve key (NIST P384) for module signing. Use
	 a strong hash of same or higher bit length, i.e. sha384 or
	 sha512 for hashing modules.

	 Note: Remove all ECDSA signing keys, e.g. certs/signing_key.pem,
	 when falling back to building Linux 5.14 and older kernels.

config MODULE_SIG_KEY_TYPE_MLDSA_44
	bool "ML-DSA-44"
	select CRYPTO_MLDSA
	depends on OPENSSL_SUPPORTS_ML_DSA
	help
	  Use an ML-DSA-44 key (NIST FIPS 204) for module signing.  ML-DSA
	  support requires OpenSSL-3.5 minimum; preferably OpenSSL-4+.  With
	  the latter, the entire module body will be signed; with the former,
	  signedAttrs will be used as it lacks support for CMS_NOATTR with
	  ML-DSA.

config MODULE_SIG_KEY_TYPE_MLDSA_65
	bool "ML-DSA-65"
	select CRYPTO_MLDSA
	depends on OPENSSL_SUPPORTS_ML_DSA
	help
	  Use an ML-DSA-65 key (NIST FIPS 204) for module signing.  ML-DSA
	  support requires OpenSSL-3.5 minimum; preferably OpenSSL-4+.  With
	  the latter, the entire module body will be signed; with the former,
	  signedAttrs will be used as it lacks support for CMS_NOATTR with
	  ML-DSA.

config MODULE_SIG_KEY_TYPE_MLDSA_87
	bool "ML-DSA-87"
	select CRYPTO_MLDSA
	depends on OPENSSL_SUPPORTS_ML_DSA
	help
	  Use an ML-DSA-87 key (NIST FIPS 204) for module signing.  ML-DSA
	  support requires OpenSSL-3.5 minimum; preferably OpenSSL-4+.  With
	  the latter, the entire module body will be signed; with the former,
	  signedAttrs will be used as it lacks support for CMS_NOATTR with
	  ML-DSA.

endchoice

config SYSTEM_TRUSTED_KEYRING
	bool "Provide system-wide ring of trusted keys"
	depends on KEYS
	depends on ASYMMETRIC_KEY_TYPE
	depends on X509_CERTIFICATE_PARSER = y
	help
	  Provide a system keyring to which trusted keys can be added.  Keys in
	  the keyring are considered to be trusted.  Keys may be added at will
	  by the kernel from compiled-in data and from hardware key stores, but
	  userspace may only add extra keys if those keys can be verified by
	  keys already in the keyring.

	  Keys in this keyring are used by module signature checking.

config SYSTEM_TRUSTED_KEYS
	string "Additional X.509 keys for default system keyring"
	depends on SYSTEM_TRUSTED_KEYRING
	help
	  If set, this option should be the filename of a PEM-formatted file
	  containing trusted X.509 certificates to be included in the default
	  system keyring. Any certificate used for module signing is implicitly
	  also trusted.

	  NOTE: If you previously provided keys for the system keyring in the
	  form of DER-encoded *.x509 files in the top-level build directory,
	  those are no longer used. You will need to set this option instead.

config SYSTEM_EXTRA_CERTIFICATE
	bool "Reserve area for inserting a certificate without recompiling"
	depends on SYSTEM_TRUSTED_KEYRING
	help
	  If set, space for an extra certificate will be reserved in the kernel
	  image. This allows introducing a trusted certificate to the default
	  system keyring without recompiling the kernel.

config SYSTEM_EXTRA_CERTIFICATE_SIZE
	int "Number of bytes to reserve for the extra certificate"
	depends on SYSTEM_EXTRA_CERTIFICATE
	default 4096
	help
	  This is the number of bytes reserved in the kernel image for a
	  certificate to be inserted.

config SECONDARY_TRUSTED_KEYRING
	bool "Provide a keyring to which extra trustable keys may be added"
	depends on SYSTEM_TRUSTED_KEYRING
	help
	  If set, provide a keyring to which extra keys may be added, provided
	  those keys are not blacklisted and are vouched for by a key built
	  into the kernel, machine keyring (if configured), or already in the
	  secondary trusted keyring.

config SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN
	bool "Only allow additional certs signed by keys on the builtin trusted keyring"
	depends on SECONDARY_TRUSTED_KEYRING
	help
	  If set, only certificates signed by keys on the builtin trusted
	  keyring may be loaded onto the secondary trusted keyring.

	  Note: The machine keyring, if configured, will be linked to the
	  secondary keyring.  When enabling this option, it is recommended
	  to also configure INTEGRITY_CA_MACHINE_KEYRING_MAX to prevent
	  linking code signing keys with imputed trust to the secondary
	  trusted keyring.

config SYSTEM_BLACKLIST_KEYRING
	bool "Provide system-wide ring of blacklisted keys"
	depends on KEYS
	help
	  Provide a system keyring to which blacklisted keys can be added.
	  Keys in the keyring are considered entirely untrusted.  Keys in this
	  keyring are used by the module signature checking to reject loading
	  of modules signed with a blacklisted key.

config SYSTEM_BLACKLIST_HASH_LIST
	string "Hashes to be preloaded into the system blacklist keyring"
	depends on SYSTEM_BLACKLIST_KEYRING
	help
	  If set, this option should be the filename of a list of hashes in the
	  form "<hash>", "<hash>", ... .  This will be included into a C
	  wrapper to incorporate the list into the kernel.  Each <hash> must be a
	  string starting with a prefix ("tbs" or "bin"), then a colon (":"), and
	  finally an even number of hexadecimal lowercase characters (up to 128).
	  Certificate hashes can be generated with
	  tools/certs/print-cert-tbs-hash.sh .

config SYSTEM_REVOCATION_LIST
	bool "Provide system-wide ring of revocation certificates"
	depends on SYSTEM_BLACKLIST_KEYRING
	depends on PKCS7_MESSAGE_PARSER=y
	help
	  If set, this allows revocation certificates to be stored in the
	  blacklist keyring and implements a hook whereby a PKCS#7 message can
	  be checked to see if it matches such a certificate.

config SYSTEM_REVOCATION_KEYS
	string "X.509 certificates to be preloaded into the system blacklist keyring"
	depends on SYSTEM_REVOCATION_LIST
	help
	  If set, this option should be the filename of a PEM-formatted file
	  containing X.509 certificates to be included in the default blacklist
	  keyring.

config SYSTEM_BLACKLIST_AUTH_UPDATE
	bool "Allow root to add signed blacklist keys"
	depends on SYSTEM_BLACKLIST_KEYRING
	depends on SYSTEM_DATA_VERIFICATION
	help
	  If set, provide the ability to load new blacklist keys at run time if
	  they are signed and vouched by a certificate from the builtin trusted
	  keyring.  The PKCS#7 signature of the description is set in the key
	  payload.  Blacklist keys cannot be removed.

config OPENSSL_SUPPORTS_ML_DSA
	def_bool $(success, openssl list -key-managers | grep -q ML-DSA-87)
	help
	  Support for ML-DSA-44/65/87 was added in openssl-3.5, so as long
	  as older versions are supported, the key types may only be
	  set after testing the installed binary for support.

endmenu