On Mar 7, 2025 Jasjiv Singh <[email protected]> wrote:
>
> Users of IPE require a way to identify when and why an operation fails,
> allowing them to both respond to violations of policy and be notified
> of potentially malicious actions on their systems with respect to IPE.
>
> This patch introduces a new error field to the AUDIT_IPE_POLICY_LOAD event
> to log policy loading failures. Currently, IPE only logs successful policy
> loads, but not failures. Tracking failures is crucial to detect malicious
> attempts and ensure a complete audit trail for security events.
>
> The new error field will capture the following error codes:
>
> * -ENOKEY: Key used to sign the IPE policy not found in the keyring
> * -ESTALE: Attempting to update an IPE policy with an older version
> * -EKEYREJECTED: IPE signature verification failed
> * -ENOENT: Policy was deleted while updating
> * -EEXIST: Same name policy already deployed
> * -ERANGE: Policy version number overflow
> * -EINVAL: Policy version parsing error
> * -EPERM: Insufficient permission
> * -ENOMEM: Out of memory (OOM)
> * -EBADMSG: Policy is invalid
>
> Here are some examples of the updated audit record types:
>
> AUDIT_IPE_POLICY_LOAD(1422):
> audit: AUDIT1422 policy_name="Test_Policy" policy_version=0.0.1
> policy_digest=sha256:84EFBA8FA71E62AE0A537FAB962F8A2BD1053964C4299DCA
> 92BFFF4DB82E86D3 auid=1000 ses=3 lsm=ipe res=1 errno=0
>
> The above record shows a new policy has been successfully loaded into
> the kernel with the policy name, version, and hash with the errno=0.
>
> AUDIT_IPE_POLICY_LOAD(1422) with error:
>
> audit: AUDIT1422 policy_name=? policy_version=? policy_digest=?
> auid=1000 ses=3 lsm=ipe res=0 errno=-74
>
> The above record shows a policy load failure due to an invalid policy
> (-EBADMSG).
>
> Signed-off-by: Jasjiv Singh <[email protected]>
> ---
> Documentation/admin-guide/LSM/ipe.rst | 69 +++++++++++++++++++--------
> security/ipe/audit.c | 21 ++++++--
> security/ipe/fs.c | 19 ++++++--
> security/ipe/policy.c | 11 ++++-
> security/ipe/policy_fs.c | 29 ++++++++---
> 5 files changed, 111 insertions(+), 38 deletions(-)
...
> diff --git a/security/ipe/audit.c b/security/ipe/audit.c
> index f05f0caa4850..ac9d68b68b8b 100644
> --- a/security/ipe/audit.c
> +++ b/security/ipe/audit.c
> @@ -21,6 +21,8 @@
>
> #define AUDIT_POLICY_LOAD_FMT "policy_name=\"%s\" policy_version=%hu.%hu.%hu
> "\
> "policy_digest=" IPE_AUDIT_HASH_ALG ":"
> +#define AUDIT_POLICY_LOAD_FAIL_FMT "policy_name=? policy_version=? "\
> + "policy_digest=?"
This should probably be AUDIT_POLICY_LOAD_NULL_FMT to be consistent with
the other IPE audit format macros, e.g. AUDIT_OLD_ACTIVE_POLICY_NULL_FMT.
> diff --git a/security/ipe/fs.c b/security/ipe/fs.c
> index 5b6d19fb844a..db18636470bf 100644
> --- a/security/ipe/fs.c
> +++ b/security/ipe/fs.c
> @@ -133,6 +133,8 @@ static ssize_t getenforce(struct file *f, char __user
> *data,
> * * %-ERANGE - Policy version number overflow
> * * %-EINVAL - Policy version parsing error
> * * %-EEXIST - Same name policy already deployed
> + * * %-ENOKEY - Key used to sign the IPE policy not
> found in the keyring
> + * * %-EKEYREJECTED - IPE signature verification failed
> */
> static ssize_t new_policy(struct file *f, const char __user *data,
> size_t len, loff_t *offset)
> @@ -141,12 +143,17 @@ static ssize_t new_policy(struct file *f, const char
> __user *data,
> char *copy = NULL;
> int rc = 0;
>
> - if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
> - return -EPERM;
> + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) {
> + rc = -EPERM;
> + goto out;
> + }
>
> copy = memdup_user_nul(data, len);
> - if (IS_ERR(copy))
> - return PTR_ERR(copy);
> + if (IS_ERR(copy)) {
> + rc = PTR_ERR(copy);
> + copy = NULL;
> + goto out;
> + }
>
> p = ipe_new_policy(NULL, 0, copy, len);
> if (IS_ERR(p)) {
> @@ -161,8 +168,10 @@ static ssize_t new_policy(struct file *f, const char
> __user *data,
> ipe_audit_policy_load(p);
>
> out:
> - if (rc < 0)
> + if (rc < 0) {
> ipe_free_policy(p);
> + ipe_audit_policy_load(ERR_PTR(rc));
> + }
> kfree(copy);
> return (rc < 0) ? rc : len;
> }
I'm going to suggest putting the audit calls closer together to help
ease maintainence, e.g.:
out:
if (rc) {
ipe_audit_policy_load(ERR_PTR(rc));
ipe_free_policy(p);
} else
ipe_audit_policy_load(p);
> diff --git a/security/ipe/policy_fs.c b/security/ipe/policy_fs.c
> index 3bcd8cbd09df..b70d2518b182 100644
> --- a/security/ipe/policy_fs.c
> +++ b/security/ipe/policy_fs.c
> @@ -292,21 +299,29 @@ static ssize_t update_policy(struct file *f, const char
> __user *data,
> char *copy = NULL;
> int rc = 0;
>
> - if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
> - return -EPERM;
> + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) {
> + rc = -EPERM;
> + goto out;
> + }
>
> copy = memdup_user(data, len);
> - if (IS_ERR(copy))
> - return PTR_ERR(copy);
> + if (IS_ERR(copy)) {
> + rc = PTR_ERR(copy);
> + copy = NULL;
> + goto out;
> + }
>
> root = d_inode(f->f_path.dentry->d_parent);
> inode_lock(root);
> rc = ipe_update_policy(root, NULL, 0, copy, len);
> inode_unlock(root);
>
> +out:
> kfree(copy);
> - if (rc)
> + if (rc) {
> + ipe_audit_policy_load(ERR_PTR(rc));
> return rc;
> + }
>
> return len;
> }
I don't really like how your auditing failure in one function and
success in a different function, that looks fragile. Unfortunately,
I don't see a quick/easy fix for that right now so I guess this is
okay, but something to keep in mind for the future.
--
paul-moore.com
