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#
config INTEGRITY
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bool "Integrity subsystem"
depends on SECURITY
default y
help
This option enables the integrity subsystem, which is comprised
of a number of different components including the Integrity
Measurement Architecture (IMA), Extended Verification Module
(EVM), IMA-appraisal extension, digital signature verification
extension and audit measurement log support.
Each of these components can be enabled/disabled separately.
Refer to the individual components for additional details.
if INTEGRITY
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config INTEGRITY_SIGNATURE
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boolean "Digital signature verification using multiple keyrings"
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depends on KEYS
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default n
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select SIGNATURE
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help
This option enables digital signature verification support
using multiple keyrings. It defines separate keyrings for each
of the different use cases - evm, ima, and modules.
Different keyrings improves search performance, but also allow
to "lock" certain keyring to prevent adding new keys.
This is useful for evm and module keyrings, when keys are
usually only added from initramfs.
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config INTEGRITY_ASYMMETRIC_KEYS
boolean "Enable asymmetric keys support"
depends on INTEGRITY_SIGNATURE
default n
select ASYMMETRIC_KEY_TYPE
select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
select PUBLIC_KEY_ALGO_RSA
select X509_CERTIFICATE_PARSER
help
This option enables digital signature verification using
asymmetric keys.
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config INTEGRITY_AUDIT
bool "Enables integrity auditing support "
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depends on AUDIT
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default y
help
In addition to enabling integrity auditing support, this
option adds a kernel parameter 'integrity_audit', which
controls the level of integrity auditing messages.
0 - basic integrity auditing messages (default)
1 - additional integrity auditing messages
Additional informational integrity auditing messages would
be enabled by specifying 'integrity_audit=1' on the kernel
command line.
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source security/integrity/ima/Kconfig
evm: re-release
EVM protects a file's security extended attributes(xattrs) against integrity
attacks. This patchset provides the framework and an initial method. The
initial method maintains an HMAC-sha1 value across the security extended
attributes, storing the HMAC value as the extended attribute 'security.evm'.
Other methods of validating the integrity of a file's metadata will be posted
separately (eg. EVM-digital-signatures).
While this patchset does authenticate the security xattrs, and
cryptographically binds them to the inode, coming extensions will bind other
directory and inode metadata for more complete protection. To help simplify
the review and upstreaming process, each extension will be posted separately
(eg. IMA-appraisal, IMA-appraisal-directory). For a general overview of the
proposed Linux integrity subsystem, refer to Dave Safford's whitepaper:
http://downloads.sf.net/project/linux-ima/linux-ima/Integrity_overview.pdf.
EVM depends on the Kernel Key Retention System to provide it with a
trusted/encrypted key for the HMAC-sha1 operation. The key is loaded onto the
root's keyring using keyctl. Until EVM receives notification that the key has
been successfully loaded onto the keyring (echo 1 > <securityfs>/evm), EVM can
not create or validate the 'security.evm' xattr, but returns INTEGRITY_UNKNOWN.
Loading the key and signaling EVM should be done as early as possible. Normally
this is done in the initramfs, which has already been measured as part of the
trusted boot. For more information on creating and loading existing
trusted/encrypted keys, refer to Documentation/keys-trusted-encrypted.txt. A
sample dracut patch, which loads the trusted/encrypted key and enables EVM, is
available from http://linux-ima.sourceforge.net/#EVM.
Based on the LSMs enabled, the set of EVM protected security xattrs is defined
at compile. EVM adds the following three calls to the existing security hooks:
evm_inode_setxattr(), evm_inode_post_setxattr(), and evm_inode_removexattr. To
initialize and update the 'security.evm' extended attribute, EVM defines three
calls: evm_inode_post_init(), evm_inode_post_setattr() and
evm_inode_post_removexattr() hooks. To verify the integrity of a security
xattr, EVM exports evm_verifyxattr().
Changelog v7:
- Fixed URL in EVM ABI documentation
Changelog v6: (based on Serge Hallyn's review)
- fix URL in patch description
- remove evm_hmac_size definition
- use SHA1_DIGEST_SIZE (removed both MAX_DIGEST_SIZE and evm_hmac_size)
- moved linux include before other includes
- test for crypto_hash_setkey failure
- fail earlier for invalid key
- clear entire encrypted key, even on failure
- check xattr name length before comparing xattr names
Changelog:
- locking based on i_mutex, remove evm_mutex
- using trusted/encrypted keys for storing the EVM key used in the HMAC-sha1
operation.
- replaced crypto hash with shash (Dmitry Kasatkin)
- support for additional methods of verifying the security xattrs
(Dmitry Kasatkin)
- iint not allocated for all regular files, but only for those appraised
- Use cap_sys_admin in lieu of cap_mac_admin
- Use __vfs_setxattr_noperm(), without permission checks, from EVM
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
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source security/integrity/evm/Kconfig
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endif # if INTEGRITY
