On 12/26/2023 11:13 PM, Mimi Zohar wrote:
On Thu, 2023-12-14 at 18:08 +0100, Roberto Sassu wrote:
From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
As for IMA, move hardcoded EVM function calls from various places in the
kernel to the LSM infrastructure, by introducing a new LSM named 'evm'
(last and always enabled like 'ima'). The order in the Makefile ensures
that 'evm' hooks are executed after 'ima' ones.
Make EVM functions as static (except for evm_inode_init_security(), which
is exported), and register them as hook implementations in init_evm_lsm().
Unlike before (see commit to move IMA to the LSM infrastructure),
evm_inode_post_setattr(), evm_inode_post_set_acl(),
evm_inode_post_remove_acl(), and evm_inode_post_removexattr() are not
executed for private inodes.
Missing is a comment on moving the inline function definitions -
evm_inode_remove_acl(), evm_inode_post_remove_acl(), and
evm_inode_post_set_acl() - to evm_main.c.
Ok.
Finally, add the LSM_ID_EVM case in lsm_list_modules_test.c
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
[...]
@@ -2307,9 +2299,7 @@ int security_inode_setxattr(struct mnt_idmap *idmap,
if (ret == 1)
ret = cap_inode_setxattr(dentry, name, value, size, flags);
- if (ret)
- return ret;
- return evm_inode_setxattr(idmap, dentry, name, value, size, flags);
+ return ret;
}
Even though capability will be called after EVM, it doesn't make a
difference in this instance.
[...]
/**
@@ -2493,9 +2472,7 @@ int security_inode_removexattr(struct mnt_idmap *idmap,
ret = call_int_hook(inode_removexattr, 1, idmap, dentry, name);
if (ret == 1)
ret = cap_inode_removexattr(idmap, dentry, name);
- if (ret)
- return ret;
- return evm_inode_removexattr(idmap, dentry, name);
+ return ret;
}
'security.capability' is one of the EVM protected xattrs. As
capability isn't an LSM, it will now be called after EVM, which is a
problem.
Uhm, according to this comment in security_inode_removexattr() and
security_inode_setxattr():
/*
* SELinux and Smack integrate the cap call,
* so assume that all LSMs supplying this call do so.
*/
We can add the call to IMA and EVM as well, to be compliant.
However, I'm missing why the two cases are different. It seems
cap_inode_set/removexattr() are doing just checks.
Thanks
Roberto
