linux/security/integrity/ima/ima_api.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2008 IBM Corporation
 *
 * Author: Mimi Zohar <[email protected]>
 *
 * File: ima_api.c
 *	Implements must_appraise_or_measure, collect_measurement,
 *	appraise_measurement, store_measurement and store_template.
 */
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/evm.h>
#include <linux/fsverity.h>

#include "ima.h"

/*
 * ima_free_template_entry - free an existing template entry
 */
void ima_free_template_entry(struct ima_template_entry *entry)
{ … }

/*
 * ima_alloc_init_template - create and initialize a new template entry
 */
int ima_alloc_init_template(struct ima_event_data *event_data,
			    struct ima_template_entry **entry,
			    struct ima_template_desc *desc)
{ … }

/*
 * ima_store_template - store ima template measurements
 *
 * Calculate the hash of a template entry, add the template entry
 * to an ordered list of measurement entries maintained inside the kernel,
 * and also update the aggregate integrity value (maintained inside the
 * configured TPM PCR) over the hashes of the current list of measurement
 * entries.
 *
 * Applications retrieve the current kernel-held measurement list through
 * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
 * TPM PCR (called quote) can be retrieved using a TPM user space library
 * and is used to validate the measurement list.
 *
 * Returns 0 on success, error code otherwise
 */
int ima_store_template(struct ima_template_entry *entry,
		       int violation, struct inode *inode,
		       const unsigned char *filename, int pcr)
{ … }

/*
 * ima_add_violation - add violation to measurement list.
 *
 * Violations are flagged in the measurement list with zero hash values.
 * By extending the PCR with 0xFF's instead of with zeroes, the PCR
 * value is invalidated.
 */
void ima_add_violation(struct file *file, const unsigned char *filename,
		       struct ima_iint_cache *iint, const char *op,
		       const char *cause)
{ … }

/**
 * ima_get_action - appraise & measure decision based on policy.
 * @idmap: idmap of the mount the inode was found from
 * @inode: pointer to the inode associated with the object being validated
 * @cred: pointer to credentials structure to validate
 * @secid: secid of the task being validated
 * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
 *        MAY_APPEND)
 * @func: caller identifier
 * @pcr: pointer filled in if matched measure policy sets pcr=
 * @template_desc: pointer filled in if matched measure policy sets template=
 * @func_data: func specific data, may be NULL
 * @allowed_algos: allowlist of hash algorithms for the IMA xattr
 *
 * The policy is defined in terms of keypairs:
 *		subj=, obj=, type=, func=, mask=, fsmagic=
 *	subj,obj, and type: are LSM specific.
 *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
 *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA | SETXATTR_CHECK
 *	| MMAP_CHECK_REQPROT
 *	mask: contains the permission mask
 *	fsmagic: hex value
 *
 * Returns IMA_MEASURE, IMA_APPRAISE mask.
 *
 */
int ima_get_action(struct mnt_idmap *idmap, struct inode *inode,
		   const struct cred *cred, u32 secid, int mask,
		   enum ima_hooks func, int *pcr,
		   struct ima_template_desc **template_desc,
		   const char *func_data, unsigned int *allowed_algos)
{ … }

static bool ima_get_verity_digest(struct ima_iint_cache *iint,
				  struct inode *inode,
				  struct ima_max_digest_data *hash)
{ … }

/*
 * ima_collect_measurement - collect file measurement
 *
 * Calculate the file hash, if it doesn't already exist,
 * storing the measurement and i_version in the iint.
 *
 * Must be called with iint->mutex held.
 *
 * Return 0 on success, error code otherwise
 */
int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file,
			    void *buf, loff_t size, enum hash_algo algo,
			    struct modsig *modsig)
{ … }

/*
 * ima_store_measurement - store file measurement
 *
 * Create an "ima" template and then store the template by calling
 * ima_store_template.
 *
 * We only get here if the inode has not already been measured,
 * but the measurement could already exist:
 *	- multiple copies of the same file on either the same or
 *	  different filesystems.
 *	- the inode was previously flushed as well as the iint info,
 *	  containing the hashing info.
 *
 * Must be called with iint->mutex held.
 */
void ima_store_measurement(struct ima_iint_cache *iint, struct file *file,
			   const unsigned char *filename,
			   struct evm_ima_xattr_data *xattr_value,
			   int xattr_len, const struct modsig *modsig, int pcr,
			   struct ima_template_desc *template_desc)
{ … }

void ima_audit_measurement(struct ima_iint_cache *iint,
			   const unsigned char *filename)
{ … }

/*
 * ima_d_path - return a pointer to the full pathname
 *
 * Attempt to return a pointer to the full pathname for use in the
 * IMA measurement list, IMA audit records, and auditing logs.
 *
 * On failure, return a pointer to a copy of the filename, not dname.
 * Returning a pointer to dname, could result in using the pointer
 * after the memory has been freed.
 */
const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
{ … }