ima: Implement ima_inode_hash
This is in preparation to add a helper for BPF LSM programs to use IMA hashes when attached to LSM hooks. There are LSM hooks like inode_unlink which do not have a struct file * argument and cannot use the existing ima_file_hash API. An inode based API is, therefore, useful in LSM based detections like an executable trying to delete itself which rely on the inode_unlink LSM hook. Moreover, the ima_file_hash function does nothing with the struct file pointer apart from calling file_inode on it and converting it to an inode. Signed-off-by: KP Singh <kpsingh@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yhs@fb.com> Acked-by: Mimi Zohar <zohar@linux.ibm.com> Link: https://lore.kernel.org/bpf/20201124151210.1081188-2-kpsingh@chromium.org
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@ -29,6 +29,7 @@ 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 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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#ifdef CONFIG_IMA_KEXEC
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@ -115,6 +116,11 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
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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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#endif /* CONFIG_IMA */
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@ -501,37 +501,14 @@ int ima_file_check(struct file *file, int mask)
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}
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EXPORT_SYMBOL_GPL(ima_file_check);
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/**
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* ima_file_hash - return the stored measurement if a file has been hashed and
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* is in the iint cache.
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* @file: pointer to the file
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* @buf: buffer in which to store the hash
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* @buf_size: length of the buffer
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*
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* On success, return the hash algorithm (as defined in the enum hash_algo).
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* If buf is not NULL, this function also outputs the hash into buf.
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* If the hash is larger than buf_size, then only buf_size bytes will be copied.
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* It generally just makes sense to pass a buffer capable of holding the largest
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* possible hash: IMA_MAX_DIGEST_SIZE.
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* The file hash returned is based on the entire file, including the appended
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* signature.
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*
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* If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
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* If the parameters are incorrect, return -EINVAL.
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*/
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int ima_file_hash(struct file *file, char *buf, size_t buf_size)
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static int __ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
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{
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struct inode *inode;
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struct integrity_iint_cache *iint;
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int hash_algo;
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if (!file)
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return -EINVAL;
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if (!ima_policy_flag)
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return -EOPNOTSUPP;
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inode = file_inode(file);
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iint = integrity_iint_find(inode);
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if (!iint)
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return -EOPNOTSUPP;
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@ -558,8 +535,61 @@ int ima_file_hash(struct file *file, char *buf, size_t buf_size)
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return hash_algo;
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}
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/**
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* ima_file_hash - return the stored measurement if a file has been hashed and
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* is in the iint cache.
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* @file: pointer to the file
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* @buf: buffer in which to store the hash
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* @buf_size: length of the buffer
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*
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* On success, return the hash algorithm (as defined in the enum hash_algo).
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* If buf is not NULL, this function also outputs the hash into buf.
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* If the hash is larger than buf_size, then only buf_size bytes will be copied.
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* It generally just makes sense to pass a buffer capable of holding the largest
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* possible hash: IMA_MAX_DIGEST_SIZE.
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* The file hash returned is based on the entire file, including the appended
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* signature.
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*
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* If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
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* If the parameters are incorrect, return -EINVAL.
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*/
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int ima_file_hash(struct file *file, char *buf, size_t buf_size)
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{
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if (!file)
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return -EINVAL;
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return __ima_inode_hash(file_inode(file), buf, buf_size);
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}
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EXPORT_SYMBOL_GPL(ima_file_hash);
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/**
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* ima_inode_hash - return the stored measurement if the inode has been hashed
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* and is in the iint cache.
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* @inode: pointer to the inode
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* @buf: buffer in which to store the hash
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* @buf_size: length of the buffer
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*
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* On success, return the hash algorithm (as defined in the enum hash_algo).
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* If buf is not NULL, this function also outputs the hash into buf.
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* If the hash is larger than buf_size, then only buf_size bytes will be copied.
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* It generally just makes sense to pass a buffer capable of holding the largest
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* possible hash: IMA_MAX_DIGEST_SIZE.
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* The hash returned is based on the entire contents, including the appended
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* signature.
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*
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* If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
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* If the parameters are incorrect, return -EINVAL.
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*/
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int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
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{
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if (!inode)
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return -EINVAL;
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return __ima_inode_hash(inode, buf, buf_size);
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}
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EXPORT_SYMBOL_GPL(ima_inode_hash);
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/**
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* ima_post_create_tmpfile - mark newly created tmpfile as new
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* @file : newly created tmpfile
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