certs/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0
   2 menu "Certificates for signature checking"
   3
   4 config MODULE_SIG_KEY
   5         string "File name or PKCS#11 URI of module signing key"
   6         default "certs/signing_key.pem"
   7         depends on MODULE_SIG || (IMA_APPRAISE_MODSIG && MODULES)
   8         help
   9          Provide the file name of a private key/certificate in PEM format,
  10          or a PKCS#11 URI according to RFC7512. The file should contain, or
  11          the URI should identify, both the certificate and its corresponding
  12          private key.
  13
  14          If this option is unchanged from its default "certs/signing_key.pem",
  15          then the kernel will automatically generate the private key and
  16          certificate as described in Documentation/admin-guide/module-signing.rst
  17
  18 choice
  19         prompt "Type of module signing key to be generated"
  20         depends on MODULE_SIG || (IMA_APPRAISE_MODSIG && MODULES)
  21         help
  22          The type of module signing key type to generate. This option
  23          does not apply if a #PKCS11 URI is used.
  24
  25 config MODULE_SIG_KEY_TYPE_RSA
  26         bool "RSA"
  27         help
  28          Use an RSA key for module signing.
  29
  30 config MODULE_SIG_KEY_TYPE_ECDSA
  31         bool "ECDSA"
  32         select CRYPTO_ECDSA
  33         depends on !(MODULE_SIG_SHA256 || MODULE_SIG_SHA3_256)
  34         help
  35          Use an elliptic curve key (NIST P384) for module signing. Use
  36          a strong hash of same or higher bit length, i.e. sha384 or
  37          sha512 for hashing modules.
  38
  39          Note: Remove all ECDSA signing keys, e.g. certs/signing_key.pem,
  40          when falling back to building Linux 5.14 and older kernels.
  41
  42 endchoice
  43
  44 config SYSTEM_TRUSTED_KEYRING
  45         bool "Provide system-wide ring of trusted keys"
  46         depends on KEYS
  47         depends on ASYMMETRIC_KEY_TYPE
  48         depends on X509_CERTIFICATE_PARSER = y
  49         help
  50           Provide a system keyring to which trusted keys can be added.  Keys in
  51           the keyring are considered to be trusted.  Keys may be added at will
  52           by the kernel from compiled-in data and from hardware key stores, but
  53           userspace may only add extra keys if those keys can be verified by
  54           keys already in the keyring.
  55
  56           Keys in this keyring are used by module signature checking.
  57
  58 config SYSTEM_TRUSTED_KEYS
  59         string "Additional X.509 keys for default system keyring"
  60         depends on SYSTEM_TRUSTED_KEYRING
  61         help
  62           If set, this option should be the filename of a PEM-formatted file
  63           containing trusted X.509 certificates to be included in the default
  64           system keyring. Any certificate used for module signing is implicitly
  65           also trusted.
  66
  67           NOTE: If you previously provided keys for the system keyring in the
  68           form of DER-encoded *.x509 files in the top-level build directory,
  69           those are no longer used. You will need to set this option instead.
  70
  71 config SYSTEM_EXTRA_CERTIFICATE
  72         bool "Reserve area for inserting a certificate without recompiling"
  73         depends on SYSTEM_TRUSTED_KEYRING
  74         help
  75           If set, space for an extra certificate will be reserved in the kernel
  76           image. This allows introducing a trusted certificate to the default
  77           system keyring without recompiling the kernel.
  78
  79 config SYSTEM_EXTRA_CERTIFICATE_SIZE
  80         int "Number of bytes to reserve for the extra certificate"
  81         depends on SYSTEM_EXTRA_CERTIFICATE
  82         default 4096
  83         help
  84           This is the number of bytes reserved in the kernel image for a
  85           certificate to be inserted.
  86
  87 config SECONDARY_TRUSTED_KEYRING
  88         bool "Provide a keyring to which extra trustable keys may be added"
  89         depends on SYSTEM_TRUSTED_KEYRING
  90         help
  91           If set, provide a keyring to which extra keys may be added, provided
  92           those keys are not blacklisted and are vouched for by a key built
  93           into the kernel, machine keyring (if configured), or already in the
  94           secondary trusted keyring.
  95
  96 config SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN
  97         bool "Only allow additional certs signed by keys on the builtin trusted keyring"
  98         depends on SECONDARY_TRUSTED_KEYRING
  99         help
 100           If set, only certificates signed by keys on the builtin trusted
 101           keyring may be loaded onto the secondary trusted keyring.
 102
 103           Note: The machine keyring, if configured, will be linked to the
 104           secondary keyring.  When enabling this option, it is recommended
 105           to also configure INTEGRITY_CA_MACHINE_KEYRING_MAX to prevent
 106           linking code signing keys with imputed trust to the secondary
 107           trusted keyring.
 108
 109 config SYSTEM_BLACKLIST_KEYRING
 110         bool "Provide system-wide ring of blacklisted keys"
 111         depends on KEYS
 112         help
 113           Provide a system keyring to which blacklisted keys can be added.
 114           Keys in the keyring are considered entirely untrusted.  Keys in this
 115           keyring are used by the module signature checking to reject loading
 116           of modules signed with a blacklisted key.
 117
 118 config SYSTEM_BLACKLIST_HASH_LIST
 119         string "Hashes to be preloaded into the system blacklist keyring"
 120         depends on SYSTEM_BLACKLIST_KEYRING
 121         help
 122           If set, this option should be the filename of a list of hashes in the
 123           form "<hash>", "<hash>", ... .  This will be included into a C
 124           wrapper to incorporate the list into the kernel.  Each <hash> must be a
 125           string starting with a prefix ("tbs" or "bin"), then a colon (":"), and
 126           finally an even number of hexadecimal lowercase characters (up to 128).
 127           Certificate hashes can be generated with
 128           tools/certs/print-cert-tbs-hash.sh .
 129
 130 config SYSTEM_REVOCATION_LIST
 131         bool "Provide system-wide ring of revocation certificates"
 132         depends on SYSTEM_BLACKLIST_KEYRING
 133         depends on PKCS7_MESSAGE_PARSER=y
 134         help
 135           If set, this allows revocation certificates to be stored in the
 136           blacklist keyring and implements a hook whereby a PKCS#7 message can
 137           be checked to see if it matches such a certificate.
 138
 139 config SYSTEM_REVOCATION_KEYS
 140         string "X.509 certificates to be preloaded into the system blacklist keyring"
 141         depends on SYSTEM_REVOCATION_LIST
 142         help
 143           If set, this option should be the filename of a PEM-formatted file
 144           containing X.509 certificates to be included in the default blacklist
 145           keyring.
 146
 147 config SYSTEM_BLACKLIST_AUTH_UPDATE
 148         bool "Allow root to add signed blacklist keys"
 149         depends on SYSTEM_BLACKLIST_KEYRING
 150         depends on SYSTEM_DATA_VERIFICATION
 151         help
 152           If set, provide the ability to load new blacklist keys at run time if
 153           they are signed and vouched by a certificate from the builtin trusted
 154           keyring.  The PKCS#7 signature of the description is set in the key
 155           payload.  Blacklist keys cannot be removed.
 156
 157 endmenu