linux/security/integrity
Roberto Sassu 7aa5783d95 ima: Allow imasig requirement to be satisfied by EVM portable signatures
System administrators can require that all accessed files have a signature
by specifying appraise_type=imasig in a policy rule.

Currently, IMA signatures satisfy this requirement. Appended signatures may
also satisfy this requirement, but are not applicable as IMA signatures.
IMA/appended signatures ensure data source authentication for file content
and prevent any change. EVM signatures instead ensure data source
authentication for file metadata. Given that the digest or signature of the
file content must be included in the metadata, EVM signatures provide the
same file data guarantees of IMA signatures, as well as providing file
metadata guarantees.

This patch lets systems protected with EVM signatures pass appraisal
verification if the appraise_type=imasig requirement is specified in the
policy. This facilitates deployment in the scenarios where only EVM
signatures are available.

The patch makes the following changes:

file xattr types:
security.ima: IMA_XATTR_DIGEST/IMA_XATTR_DIGEST_NG
security.evm: EVM_XATTR_PORTABLE_DIGSIG

execve(), mmap(), open() behavior (with appraise_type=imasig):
before: denied (file without IMA signature, imasig requirement not met)
after: allowed (file with EVM portable signature, imasig requirement met)

open(O_WRONLY) behavior (without appraise_type=imasig):
before: allowed (file without IMA signature, not immutable)
after: denied (file with EVM portable signature, immutable)

In addition, similarly to IMA signatures, this patch temporarily allows
new files without or with incomplete metadata to be opened so that content
can be written.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
2021-06-01 12:30:51 -04:00
..
evm evm: Allow setxattr() and setattr() for unmodified metadata 2021-06-01 12:28:34 -04:00
ima ima: Allow imasig requirement to be satisfied by EVM portable signatures 2021-06-01 12:30:51 -04:00
platform_certs integrity: Load mokx variables into the blacklist keyring 2021-03-11 16:34:48 +00:00
digsig_asymmetric.c ima: Support EC keys for signature verification 2021-03-26 19:41:59 +11:00
digsig.c ima: enable loading of build time generated key on .ima keyring 2021-04-09 10:40:20 -04:00
iint.c evm: Load EVM key in ima_load_x509() to avoid appraisal 2021-05-21 12:47:04 -04:00
integrity_audit.c integrity: Use current_uid() in integrity_audit_message() 2020-08-31 17:46:50 -04:00
integrity.h crypto: sha - split sha.h into sha1.h and sha2.h 2020-11-20 14:45:33 +11:00
Kconfig powerpc: Load firmware trusted keys/hashes into kernel keyring 2019-11-13 00:33:23 +11:00
Makefile powerpc: Load firmware trusted keys/hashes into kernel keyring 2019-11-13 00:33:23 +11:00