[PATCH 7/9] ima: Move ima_file_check() into LSM
From: Kees Cook <hidden>
Date: 2022-10-13 22:37:55
Also in:
linux-hardening, linux-integrity, lkml
Subsystem:
extended verification module (evm), filesystems (vfs and infrastructure), integrity measurement architecture (ima), kernel nfsd, sunrpc, and lockd servers, security subsystem, the rest · Maintainers:
Mimi Zohar, Roberto Sassu, Alexander Viro, Christian Brauner, Dmitry Kasatkin, Chuck Lever, Jeff Layton, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
The "file_open" hook in the LSM is the correct place to add the
ima_file_check() callback. Rename it to ima_file_open(), and use the
newly created helper to construct the permissions mask from the file
flags and fmode.
For reference, the LSM hooks across an open are:
do_filp_open(dfd, filename, open_flags)
path_openat(nameidata, open_flags, flags)
file = alloc_empty_file(open_flags, current_cred());
do_open(nameidata, file, open_flags)
may_open(path, acc_mode, open_flag)
inode_permission(inode, MAY_OPEN | acc_mode)
----> security_inode_permission(inode, acc_mode)
vfs_open(path, file)
do_dentry_open(file, path->dentry->d_inode, open)
----> security_file_open(f)
open()
The open-coded hook in the VFS and NFS are removed, as they are fully
covered by the security_file_open() hook.
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Jonathan McDowell <redacted>
Cc: linux-integrity@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <redacted>
---
fs/namei.c | 2 --
fs/nfsd/vfs.c | 6 ------
include/linux/ima.h | 6 ------
security/integrity/ima/ima_main.c | 14 +++++++-------
4 files changed, 7 insertions(+), 21 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 53b4bc094db2..d9bd3887e823 100644
--- a/fs/namei.c
+++ b/fs/namei.c@@ -3555,8 +3555,6 @@ static int do_open(struct nameidata *nd, error = may_open(mnt_userns, &nd->path, acc_mode, open_flag); if (!error && !(file->f_mode & FMODE_OPENED)) error = vfs_open(&nd->path, file); - if (!error) - error = ima_file_check(file, op->acc_mode); if (!error && do_truncate) error = handle_truncate(mnt_userns, file); if (unlikely(error > 0)) {
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 9f486b788ed0..33fe326272df 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c@@ -762,12 +762,6 @@ __nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type, goto out_nfserr; } - host_err = ima_file_check(file, may_flags); - if (host_err) { - fput(file); - goto out_nfserr; - } - if (may_flags & NFSD_MAY_64BIT_COOKIE) file->f_mode |= FMODE_64BITHASH; else
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 70180b9bd974..cf1e48a2d97d 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h@@ -16,7 +16,6 @@ struct linux_binprm; #ifdef CONFIG_IMA extern enum hash_algo ima_get_current_hash_algo(void); -extern int ima_file_check(struct file *file, int mask); extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns, struct inode *inode); extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
@@ -45,11 +44,6 @@ static inline enum hash_algo ima_get_current_hash_algo(void) return HASH_ALGO__LAST; } -static inline int ima_file_check(struct file *file, int mask) -{ - return 0; -} - static inline void ima_post_create_tmpfile(struct user_namespace *mnt_userns, struct inode *inode) {
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index ffebd3236f24..823d660b53ec 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c@@ -12,7 +12,7 @@ * * File: ima_main.c * implements the IMA hooks: ima_bprm_check, ima_file_mmap, - * and ima_file_check. + * and ima_file_open. */ #include <linux/module.h>
@@ -504,25 +504,24 @@ static int ima_bprm_check(struct linux_binprm *bprm) } /** - * ima_file_check - based on policy, collect/store measurement. + * ima_file_open - based on policy, collect/store measurement. * @file: pointer to the file to be measured - * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND * * Measure files based on the ima_must_measure() policy decision. * * On success return 0. On integrity appraisal error, assuming the file * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. */ -int ima_file_check(struct file *file, int mask) +static int ima_file_open(struct file *file) { + u32 perms = file_to_perms(file); u32 secid; security_current_getsecid_subj(&secid); + return process_measurement(file, current_cred(), secid, NULL, 0, - mask & (MAY_READ | MAY_WRITE | MAY_EXEC | - MAY_APPEND), FILE_CHECK); + perms, FILE_CHECK); } -EXPORT_SYMBOL_GPL(ima_file_check); static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf, size_t buf_size)
@@ -1085,6 +1084,7 @@ static struct security_hook_list ima_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(bprm_check_security, ima_bprm_check), LSM_HOOK_INIT(mmap_file, ima_file_mmap), LSM_HOOK_INIT(file_mprotect, ima_file_mprotect), + LSM_HOOK_INIT(file_open, ima_file_open), LSM_HOOK_INIT(file_free_security, ima_file_free), LSM_HOOK_INIT(kernel_read_file, ima_read_file), LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file),
--
2.34.1