Quoting Mimi Zohar (zohar@xxxxxxxxxxxxxxxxxx): > 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. > > 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 v6: (based on Serge Hallyn's review) > - fix URL in patch description It's still wrong in Documentation/ABI/testing/evm... > - 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 The rest looks good, thanks Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx> -serge -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
