On Fri, 2024-02-09 at 11:12 +0100, Christian Brauner wrote:
On Mon, Jan 15, 2024 at 07:17:56PM +0100, Roberto Sassu wrote:
From: Roberto Sassu roberto.sassu@huawei.com
In preparation to move IMA and EVM to the LSM infrastructure, introduce the file_post_open hook. Also, export security_file_post_open() for NFS.
Based on policy, IMA calculates the digest of the file content and extends the TPM with the digest, verifies the file's integrity based on the digest, and/or includes the file digest in the audit log.
LSMs could similarly take action depending on the file content and the access mask requested with open().
The new hook returns a value and can cause the open to be aborted.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com Reviewed-by: Stefan Berger stefanb@linux.ibm.com Acked-by: Casey Schaufler casey@schaufler-ca.com Reviewed-by: Mimi Zohar zohar@linux.ibm.com
fs/namei.c | 2 ++ fs/nfsd/vfs.c | 6 ++++++ include/linux/lsm_hook_defs.h | 1 + include/linux/security.h | 6 ++++++ security/security.c | 17 +++++++++++++++++ 5 files changed, 32 insertions(+)
diff --git a/fs/namei.c b/fs/namei.c index 71c13b2990b4..fb93d3e13df6 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3620,6 +3620,8 @@ static int do_open(struct nameidata *nd, error = may_open(idmap, &nd->path, acc_mode, open_flag); if (!error && !(file->f_mode & FMODE_OPENED)) error = vfs_open(&nd->path, file);
- if (!error)
error = security_file_post_open(file, op->acc_mode);What does it do for O_CREAT? IOW, we managed to create that thing and we managed to open that thing. Can security_file_post_open() and ima_file_check() fail afterwards even for newly created files?
$ strace touch test-file ... openat(AT_FDCWD, "test-file", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666) = -1 EPERM (Operation not permitted)
The open fails, but the file is there. I didn't see warnings/errors in the kernel log.
Roberto