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Asymmetric keys were introduced in linux-3.7 to verify the signature on signed kernel modules. The asymmetric keys infrastructure abstracts the signature verification from the crypto details. This patch adds IMA/EVM signature verification using asymmetric keys. Support for additional signature verification methods can now be delegated to the asymmetric key infrastructure. Although the module signature header and the IMA/EVM signature header could use the same format, to minimize the signature length and save space in the extended attribute, this patch defines a new IMA/EVM header format. The main difference is that the key identifier is a sha1[12 - 19] hash of the key modulus and exponent, similar to the current implementation. The only purpose of the key identifier is to identify the corresponding key in the kernel keyring. ima-evm-utils was updated to support the new signature format. While asymmetric signature verification functionality supports many different hash algorithms, the hash used in this patch is calculated during the IMA collection phase, based on the configured algorithm. The default algorithm is sha1, but for backwards compatibility md5 is supported. Due to this current limitation, signatures should be generated using a sha1 hash algorithm. Changes in this patch: - Functionality has been moved to separate source file in order to get rid of in source #ifdefs. - keyid is derived according to the RFC 3280. It does not require to assign IMA/EVM specific "description" when loading X509 certificate. Kernel asymmetric key subsystem automatically generate the description. Also loading a certificate does not require using of ima-evm-utils and can be done using keyctl only. - keyid size is reduced to 32 bits to save xattr space. Key search is done using partial match functionality of asymmetric_key_match(). - Kconfig option title was changed Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com> Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
34 lines
1.0 KiB
Plaintext
34 lines
1.0 KiB
Plaintext
#
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config INTEGRITY
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def_bool y
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depends on IMA || EVM
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config INTEGRITY_SIGNATURE
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boolean "Digital signature verification using multiple keyrings"
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depends on INTEGRITY && KEYS
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default n
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select SIGNATURE
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help
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This option enables digital signature verification support
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using multiple keyrings. It defines separate keyrings for each
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of the different use cases - evm, ima, and modules.
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Different keyrings improves search performance, but also allow
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to "lock" certain keyring to prevent adding new keys.
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This is useful for evm and module keyrings, when keys are
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usually only added from initramfs.
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config INTEGRITY_ASYMMETRIC_KEYS
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boolean "Enable asymmetric keys support"
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depends on INTEGRITY_SIGNATURE
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default n
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select ASYMMETRIC_KEY_TYPE
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select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
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select PUBLIC_KEY_ALGO_RSA
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select X509_CERTIFICATE_PARSER
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help
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This option enables digital signature verification using
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asymmetric keys.
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source security/integrity/ima/Kconfig
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source security/integrity/evm/Kconfig
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