[PATCH v15 11/26] ima: Define mac_admin_ns_capable() as a wrapper for ns_capable()
From: Stefan Berger <stefanb@linux.ibm.com>
Date: 2023-02-06 14:04:31
Also in:
linux-fsdevel, linux-integrity, lkml
Subsystem:
capabilities, extended verification module (evm), filesystems (vfs and infrastructure), integrity measurement architecture (ima), security subsystem, the rest · Maintainers:
Serge Hallyn, Mimi Zohar, Roberto Sassu, Alexander Viro, Christian Brauner, Dmitry Kasatkin, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
Define mac_admin_ns_capable() as a wrapper for the combined ns_capable()
checks on CAP_MAC_ADMIN and CAP_SYS_ADMIN in a user namespace. Return
true on the check if either capability or both are available.
Use mac_admin_ns_capable() in place of capable(SYS_ADMIN). This will allow
an IMA namespace to read the policy with only CAP_MAC_ADMIN, which has
less privileges than CAP_SYS_ADMIN.
Since CAP_MAC_ADMIN is an additional capability added to an existing gate
avoid auditing in case it is not set.
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Denis Semakin <redacted>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
v13:
- implemented file_sb_user_ns(const struct file *); const is needed so it
can be called with seq_file's 'const struct file *file'
v11:
- use ns_capable_noaudit for CAP_MAC_ADMIN to avoid auditing in this case
---
include/linux/capability.h | 6 ++++++
include/linux/fs.h | 5 +++++
security/integrity/ima/ima.h | 6 ++++++
security/integrity/ima/ima_fs.c | 5 ++++-
4 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/include/linux/capability.h b/include/linux/capability.h
index 65efb74c3585..dc3e1230b365 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h@@ -270,6 +270,12 @@ static inline bool checkpoint_restore_ns_capable(struct user_namespace *ns) ns_capable(ns, CAP_SYS_ADMIN); } +static inline bool mac_admin_ns_capable(struct user_namespace *ns) +{ + return ns_capable_noaudit(ns, CAP_MAC_ADMIN) || + ns_capable(ns, CAP_SYS_ADMIN); +} + /* audit system wants to get cap info from files as well */ int get_vfs_caps_from_disk(struct user_namespace *mnt_userns, const struct dentry *dentry,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c1769a2c5d70..4662efed3171 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h@@ -2730,6 +2730,11 @@ static inline struct user_namespace *file_mnt_user_ns(struct file *file) return mnt_user_ns(file->f_path.mnt); } +static inline struct user_namespace *file_sb_user_ns(const struct file *file) +{ + return i_user_ns(file_inode(file)); +} + static inline struct mnt_idmap *file_mnt_idmap(struct file *file) { return mnt_idmap(file->f_path.mnt);
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 4de8ec776611..69f95ed0b8c6 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h@@ -492,4 +492,10 @@ static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op, #define POLICY_FILE_FLAGS S_IWUSR #endif /* CONFIG_IMA_READ_POLICY */ +static inline +struct user_namespace *ima_user_ns_from_file(const struct file *filp) +{ + return file_sb_user_ns(filp); +} + #endif /* __LINUX_IMA_H */
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 89d3113ceda1..c41aa61b7393 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c@@ -377,6 +377,9 @@ static const struct seq_operations ima_policy_seqops = { */ static int ima_open_policy(struct inode *inode, struct file *filp) { +#ifdef CONFIG_IMA_READ_POLICY + struct user_namespace *user_ns = ima_user_ns_from_file(filp); +#endif struct ima_namespace *ns = &init_ima_ns; if (!(filp->f_flags & O_WRONLY)) {
@@ -385,7 +388,7 @@ static int ima_open_policy(struct inode *inode, struct file *filp) #else if ((filp->f_flags & O_ACCMODE) != O_RDONLY) return -EACCES; - if (!capable(CAP_SYS_ADMIN)) + if (!mac_admin_ns_capable(user_ns)) return -EPERM; return seq_open(filp, &ima_policy_seqops); #endif
--
2.37.3