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e61b135f7b
The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. So far posix acls were passed as a void blob to the security and integrity modules. Some of them like evm then proceed to interpret the void pointer and convert it into the kernel internal struct posix acl representation to perform their integrity checking magic. This is obviously pretty problematic as that requires knowledge that only the vfs is guaranteed to have and has lead to various bugs. Add a proper security hook for setting posix acls and pass down the posix acls in their appropriate vfs format instead of hacking it through a void pointer stored in the uapi format. I spent considerate time in the security module and integrity infrastructure and audited all codepaths. EVM is the only part that really has restrictions based on the actual posix acl values passed through it (e.g., i_mode). Before this dedicated hook EVM used to translate from the uapi posix acl format sent to it in the form of a void pointer into the vfs format. This is not a good thing. Instead of hacking around in the uapi struct give EVM the posix acls in the appropriate vfs format and perform sane permissions checks that mirror what it used to to in the generic xattr hook. IMA doesn't have any restrictions on posix acls. When posix acls are changed it just wants to update its appraisal status to trigger an EVM revalidation. The removal of posix acls is equivalent to passing NULL to the posix set acl hooks. This is the same as before through the generic xattr api. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Acked-by: Paul Moore <paul@paul-moore.com> (LSM) Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
250 lines
6.5 KiB
C
250 lines
6.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2008 IBM Corporation
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* Author: Mimi Zohar <zohar@us.ibm.com>
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*/
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#ifndef _LINUX_IMA_H
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#define _LINUX_IMA_H
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#include <linux/kernel_read_file.h>
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#include <linux/fs.h>
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#include <linux/security.h>
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#include <linux/kexec.h>
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#include <crypto/hash_info.h>
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struct linux_binprm;
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#ifdef CONFIG_IMA
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extern enum hash_algo ima_get_current_hash_algo(void);
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extern int ima_bprm_check(struct linux_binprm *bprm);
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extern int ima_file_check(struct file *file, int mask);
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extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
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struct inode *inode);
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extern void ima_file_free(struct file *file);
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extern int ima_file_mmap(struct file *file, unsigned long prot);
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extern int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot);
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extern int ima_load_data(enum kernel_load_data_id id, bool contents);
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extern int ima_post_load_data(char *buf, loff_t size,
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enum kernel_load_data_id id, char *description);
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extern int ima_read_file(struct file *file, enum kernel_read_file_id id,
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bool contents);
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extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
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enum kernel_read_file_id id);
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extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
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struct dentry *dentry);
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extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
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extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size);
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extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
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extern int ima_measure_critical_data(const char *event_label,
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const char *event_name,
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const void *buf, size_t buf_len,
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bool hash, u8 *digest, size_t digest_len);
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#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
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extern void ima_appraise_parse_cmdline(void);
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#else
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static inline void ima_appraise_parse_cmdline(void) {}
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#endif
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#ifdef CONFIG_IMA_KEXEC
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extern void ima_add_kexec_buffer(struct kimage *image);
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#endif
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#else
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static inline enum hash_algo ima_get_current_hash_algo(void)
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{
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return HASH_ALGO__LAST;
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}
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static inline int ima_bprm_check(struct linux_binprm *bprm)
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{
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return 0;
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}
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static inline int ima_file_check(struct file *file, int mask)
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{
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return 0;
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}
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static inline void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
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struct inode *inode)
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{
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}
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static inline void ima_file_free(struct file *file)
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{
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return;
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}
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static inline int ima_file_mmap(struct file *file, unsigned long prot)
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{
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return 0;
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}
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static inline int ima_file_mprotect(struct vm_area_struct *vma,
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unsigned long prot)
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{
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return 0;
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}
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static inline int ima_load_data(enum kernel_load_data_id id, bool contents)
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{
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return 0;
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}
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static inline int ima_post_load_data(char *buf, loff_t size,
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enum kernel_load_data_id id,
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char *description)
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{
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return 0;
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}
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static inline int ima_read_file(struct file *file, enum kernel_read_file_id id,
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bool contents)
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{
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return 0;
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}
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static inline int ima_post_read_file(struct file *file, void *buf, loff_t size,
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enum kernel_read_file_id id)
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{
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return 0;
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}
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static inline void ima_post_path_mknod(struct user_namespace *mnt_userns,
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struct dentry *dentry)
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{
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return;
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}
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static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
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{
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return -EOPNOTSUPP;
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}
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static inline int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
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{
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return -EOPNOTSUPP;
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}
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static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
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static inline int ima_measure_critical_data(const char *event_label,
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const char *event_name,
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const void *buf, size_t buf_len,
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bool hash, u8 *digest,
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size_t digest_len)
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{
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return -ENOENT;
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}
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#endif /* CONFIG_IMA */
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#ifdef CONFIG_HAVE_IMA_KEXEC
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int __init ima_free_kexec_buffer(void);
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int __init ima_get_kexec_buffer(void **addr, size_t *size);
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#endif
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#ifdef CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT
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extern bool arch_ima_get_secureboot(void);
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extern const char * const *arch_get_ima_policy(void);
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#else
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static inline bool arch_ima_get_secureboot(void)
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{
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return false;
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}
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static inline const char * const *arch_get_ima_policy(void)
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{
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return NULL;
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}
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#endif
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#ifndef CONFIG_IMA_KEXEC
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struct kimage;
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static inline void ima_add_kexec_buffer(struct kimage *image)
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{}
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#endif
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#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
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extern void ima_post_key_create_or_update(struct key *keyring,
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struct key *key,
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const void *payload, size_t plen,
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unsigned long flags, bool create);
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#else
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static inline void ima_post_key_create_or_update(struct key *keyring,
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struct key *key,
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const void *payload,
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size_t plen,
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unsigned long flags,
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bool create) {}
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#endif /* CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS */
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#ifdef CONFIG_IMA_APPRAISE
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extern bool is_ima_appraise_enabled(void);
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extern void ima_inode_post_setattr(struct user_namespace *mnt_userns,
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struct dentry *dentry);
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extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len);
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extern int ima_inode_set_acl(struct user_namespace *mnt_userns,
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struct dentry *dentry, const char *acl_name,
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struct posix_acl *kacl);
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static inline int ima_inode_remove_acl(struct user_namespace *mnt_userns,
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struct dentry *dentry,
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const char *acl_name)
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{
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return ima_inode_set_acl(mnt_userns, dentry, acl_name, NULL);
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}
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extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
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#else
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static inline bool is_ima_appraise_enabled(void)
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{
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return 0;
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}
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static inline void ima_inode_post_setattr(struct user_namespace *mnt_userns,
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struct dentry *dentry)
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{
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return;
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}
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static inline int ima_inode_setxattr(struct dentry *dentry,
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const char *xattr_name,
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const void *xattr_value,
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size_t xattr_value_len)
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{
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return 0;
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}
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static inline int ima_inode_set_acl(struct user_namespace *mnt_userns,
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struct dentry *dentry, const char *acl_name,
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struct posix_acl *kacl)
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{
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return 0;
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}
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static inline int ima_inode_removexattr(struct dentry *dentry,
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const char *xattr_name)
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{
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return 0;
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}
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static inline int ima_inode_remove_acl(struct user_namespace *mnt_userns,
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struct dentry *dentry,
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const char *acl_name)
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{
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return 0;
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}
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#endif /* CONFIG_IMA_APPRAISE */
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#if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)
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extern bool ima_appraise_signature(enum kernel_read_file_id func);
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#else
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static inline bool ima_appraise_signature(enum kernel_read_file_id func)
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{
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return false;
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}
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#endif /* CONFIG_IMA_APPRAISE && CONFIG_INTEGRITY_TRUSTED_KEYRING */
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#endif /* _LINUX_IMA_H */
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