On Wed, Sep 6, 2023 at 7:48 PM Casey Schaufler [off-list ref] wrote:
On 9/6/2023 4:22 PM, Paul Moore wrote:
quoted
On Aug 28, 2023 Casey Schaufler [off-list ref] wrote:
quoted
Create a system call lsm_get_self_attr() to provide the security
module maintained attributes of the current process.
Create a system call lsm_set_self_attr() to set a security
module maintained attribute of the current process.
Historically these attributes have been exposed to user space via
entries in procfs under /proc/self/attr.
The attribute value is provided in a lsm_ctx structure. The structure
identifies the size of the attribute, and the attribute value. The format
of the attribute value is defined by the security module. A flags field
is included for LSM specific information. It is currently unused and must
be 0. The total size of the data, including the lsm_ctx structure and any
padding, is maintained as well.
struct lsm_ctx {
__u64 id;
__u64 flags;
__u64 len;
__u64 ctx_len;
__u8 ctx[];
};
Two new LSM hooks are used to interface with the LSMs.
security_getselfattr() collects the lsm_ctx values from the
LSMs that support the hook, accounting for space requirements.
security_setselfattr() identifies which LSM the attribute is
intended for and passes it along.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <redacted>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
---
Documentation/userspace-api/lsm.rst | 70 +++++++++++++
include/linux/lsm_hook_defs.h | 4 +
include/linux/lsm_hooks.h | 1 +
include/linux/security.h | 19 ++++
include/linux/syscalls.h | 5 +
include/uapi/linux/lsm.h | 36 +++++++
kernel/sys_ni.c | 2 +
security/Makefile | 1 +
security/lsm_syscalls.c | 57 +++++++++++
security/security.c | 146 ++++++++++++++++++++++++++++
10 files changed, 341 insertions(+)
create mode 100644 Documentation/userspace-api/lsm.rst
create mode 100644 security/lsm_syscalls.c
..
quoted
diff --git a/security/security.c b/security/security.c
index 82253294069c..aa4ade1f71b9 100644
--- a/security/security.c
+++ b/security/security.c
@@ -3798,6 +3798,152 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
}
EXPORT_SYMBOL(security_d_instantiate);
+/**
+ * security_getselfattr - Read an LSM attribute of the current process.
+ * @attr: which attribute to return
+ * @uctx: the user-space destination for the information, or NULL
+ * @size: pointer to the size of space available to receive the data
+ * @flags: special handling options. LSM_FLAG_SINGLE indicates that only
+ * attributes associated with the LSM identified in the passed @ctx be
+ * reported.
+ *
+ * A NULL value for @uctx can be used to get both the number of attributes
+ * and the size of the data.
+ *
+ * Returns the number of attributes found on success, negative value
+ * on error. @size is reset to the total size of the data.
+ * If @size is insufficient to contain the data -E2BIG is returned.
+ */
+int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx,
+ size_t __user *size, u32 flags)
+{
+ struct security_hook_list *hp;
+ struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, };
+ u8 __user *base = (u8 __user *)uctx;
+ size_t total = 0;
+ size_t entrysize;
+ size_t left;
+ bool toobig = false;
+ bool single = false;
+ int count = 0;
+ int rc;
+
+ if (attr == LSM_ATTR_UNDEF)
+ return -EINVAL;
+ if (size == NULL)
+ return -EINVAL;
+ if (get_user(left, size))
+ return -EFAULT;
+
+ if (flags) {
+ /*
+ * Only flag supported is LSM_FLAG_SINGLE
+ */
+ if (flags & LSM_FLAG_SINGLE)
+ return -EINVAL;
Should this be something like the following?
if (flags & ~LSM_FLAG_SINGLE)
return -EINVAL;
Yes. I have a fix ready. There are a couple other touch-ups, too.
Great. Since you are doing another revision, can you double check all
of the patch subject lines to ensure you don't have any double spaces?
I see at least one, possibly two more.
--
paul-moore.com