From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
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@xxxxxxxxxx>
Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
---
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);
if (!error)
error = ima_file_check(file, op->acc_mode);
if (!error && do_truncate)
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index fbbea7498f02..b0c3f07a8bba 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -877,6 +877,12 @@ __nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type,
goto out;
}
+ host_err = security_file_post_open(file, may_flags);
+ if (host_err) {
+ fput(file);
+ goto out;
+ }
+
host_err = ima_file_check(file, may_flags);
if (host_err) {
fput(file);
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 88452e45025c..4f6861fecacd 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -189,6 +189,7 @@ LSM_HOOK(int, 0, file_send_sigiotask, struct task_struct *tsk,
struct fown_struct *fown, int sig)
LSM_HOOK(int, 0, file_receive, struct file *file)
LSM_HOOK(int, 0, file_open, struct file *file)
+LSM_HOOK(int, 0, file_post_open, struct file *file, int mask)
LSM_HOOK(int, 0, file_truncate, struct file *file)
LSM_HOOK(int, 0, task_alloc, struct task_struct *task,
unsigned long clone_flags)
diff --git a/include/linux/security.h b/include/linux/security.h
index 922ea7709bae..c360458920b1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -409,6 +409,7 @@ int security_file_send_sigiotask(struct task_struct *tsk,
struct fown_struct *fown, int sig);
int security_file_receive(struct file *file);
int security_file_open(struct file *file);
+int security_file_post_open(struct file *file, int mask);
int security_file_truncate(struct file *file);
int security_task_alloc(struct task_struct *task, unsigned long clone_flags);
void security_task_free(struct task_struct *task);
@@ -1065,6 +1066,11 @@ static inline int security_file_open(struct file *file)
return 0;
}
+static inline int security_file_post_open(struct file *file, int mask)
+{
+ return 0;
+}
+
static inline int security_file_truncate(struct file *file)
{
return 0;
diff --git a/security/security.c b/security/security.c
index 8aa6e9f316dd..fe6a160afc35 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2954,6 +2954,23 @@ int security_file_open(struct file *file)
return fsnotify_perm(file, MAY_OPEN);
}
+/**
+ * security_file_post_open() - Evaluate a file after it has been opened
+ * @file: the file
+ * @mask: access mask
+ *
+ * Evaluate an opened file and the access mask requested with open(). The hook
+ * is useful for LSMs that require the file content to be available in order to
+ * make decisions.
+ *
+ * Return: Returns 0 if permission is granted.
+ */
+int security_file_post_open(struct file *file, int mask)
+{
+ return call_int_hook(file_post_open, 0, file, mask);
+}
+EXPORT_SYMBOL_GPL(security_file_post_open);
+
/**
* security_file_truncate() - Check if truncating a file is allowed
* @file: file
--
2.34.1
