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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * Integrity Measurement Architecture
- *
- * Copyright (C) 2005,2006,2007,2008 IBM Corporation
- *
- * Authors:
- * Reiner Sailer <[email protected]>
- * Serge Hallyn <[email protected]>
- * Kylene Hall <[email protected]>
- * Mimi Zohar <[email protected]>
- *
- * File: ima_main.c
- * implements the IMA hooks: ima_bprm_check, ima_file_mmap,
- * and ima_file_check.
- */
- #include <linux/module.h>
- #include <linux/file.h>
- #include <linux/binfmts.h>
- #include <linux/kernel_read_file.h>
- #include <linux/mount.h>
- #include <linux/mman.h>
- #include <linux/slab.h>
- #include <linux/xattr.h>
- #include <linux/ima.h>
- #include <linux/iversion.h>
- #include <linux/fs.h>
- #include <linux/iversion.h>
- #include "ima.h"
- #ifdef CONFIG_IMA_APPRAISE
- int ima_appraise = IMA_APPRAISE_ENFORCE;
- #else
- int ima_appraise;
- #endif
- int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1;
- static int hash_setup_done;
- static struct notifier_block ima_lsm_policy_notifier = {
- .notifier_call = ima_lsm_policy_change,
- };
- static int __init hash_setup(char *str)
- {
- struct ima_template_desc *template_desc = ima_template_desc_current();
- int i;
- if (hash_setup_done)
- return 1;
- if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
- if (strncmp(str, "sha1", 4) == 0) {
- ima_hash_algo = HASH_ALGO_SHA1;
- } else if (strncmp(str, "md5", 3) == 0) {
- ima_hash_algo = HASH_ALGO_MD5;
- } else {
- pr_err("invalid hash algorithm \"%s\" for template \"%s\"",
- str, IMA_TEMPLATE_IMA_NAME);
- return 1;
- }
- goto out;
- }
- i = match_string(hash_algo_name, HASH_ALGO__LAST, str);
- if (i < 0) {
- pr_err("invalid hash algorithm \"%s\"", str);
- return 1;
- }
- ima_hash_algo = i;
- out:
- hash_setup_done = 1;
- return 1;
- }
- __setup("ima_hash=", hash_setup);
- enum hash_algo ima_get_current_hash_algo(void)
- {
- return ima_hash_algo;
- }
- /* Prevent mmap'ing a file execute that is already mmap'ed write */
- static int mmap_violation_check(enum ima_hooks func, struct file *file,
- char **pathbuf, const char **pathname,
- char *filename)
- {
- struct inode *inode;
- int rc = 0;
- if ((func == MMAP_CHECK) && mapping_writably_mapped(file->f_mapping)) {
- rc = -ETXTBSY;
- inode = file_inode(file);
- if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */
- *pathname = ima_d_path(&file->f_path, pathbuf,
- filename);
- integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname,
- "mmap_file", "mmapped_writers", rc, 0);
- }
- return rc;
- }
- /*
- * ima_rdwr_violation_check
- *
- * Only invalidate the PCR for measured files:
- * - Opening a file for write when already open for read,
- * results in a time of measure, time of use (ToMToU) error.
- * - Opening a file for read when already open for write,
- * could result in a file measurement error.
- *
- */
- static void ima_rdwr_violation_check(struct file *file,
- struct integrity_iint_cache *iint,
- int must_measure,
- char **pathbuf,
- const char **pathname,
- char *filename)
- {
- struct inode *inode = file_inode(file);
- fmode_t mode = file->f_mode;
- bool send_tomtou = false, send_writers = false;
- if (mode & FMODE_WRITE) {
- if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
- if (!iint)
- iint = integrity_iint_find(inode);
- /* IMA_MEASURE is set from reader side */
- if (iint && test_bit(IMA_MUST_MEASURE,
- &iint->atomic_flags))
- send_tomtou = true;
- }
- } else {
- if (must_measure)
- set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
- if (inode_is_open_for_write(inode) && must_measure)
- send_writers = true;
- }
- if (!send_tomtou && !send_writers)
- return;
- *pathname = ima_d_path(&file->f_path, pathbuf, filename);
- if (send_tomtou)
- ima_add_violation(file, *pathname, iint,
- "invalid_pcr", "ToMToU");
- if (send_writers)
- ima_add_violation(file, *pathname, iint,
- "invalid_pcr", "open_writers");
- }
- static void ima_check_last_writer(struct integrity_iint_cache *iint,
- struct inode *inode, struct file *file)
- {
- fmode_t mode = file->f_mode;
- bool update;
- if (!(mode & FMODE_WRITE))
- return;
- mutex_lock(&iint->mutex);
- if (atomic_read(&inode->i_writecount) == 1) {
- update = test_and_clear_bit(IMA_UPDATE_XATTR,
- &iint->atomic_flags);
- if (!IS_I_VERSION(inode) ||
- !inode_eq_iversion(inode, iint->version) ||
- (iint->flags & IMA_NEW_FILE)) {
- iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
- iint->measured_pcrs = 0;
- if (update)
- ima_update_xattr(iint, file);
- }
- }
- mutex_unlock(&iint->mutex);
- }
- /**
- * ima_file_free - called on __fput()
- * @file: pointer to file structure being freed
- *
- * Flag files that changed, based on i_version
- */
- void ima_file_free(struct file *file)
- {
- struct inode *inode = file_inode(file);
- struct integrity_iint_cache *iint;
- if (!ima_policy_flag || !S_ISREG(inode->i_mode))
- return;
- iint = integrity_iint_find(inode);
- if (!iint)
- return;
- ima_check_last_writer(iint, inode, file);
- }
- static int process_measurement(struct file *file, const struct cred *cred,
- u32 secid, char *buf, loff_t size, int mask,
- enum ima_hooks func)
- {
- struct inode *backing_inode, *inode = file_inode(file);
- struct integrity_iint_cache *iint = NULL;
- struct ima_template_desc *template_desc = NULL;
- char *pathbuf = NULL;
- char filename[NAME_MAX];
- const char *pathname = NULL;
- int rc = 0, action, must_appraise = 0;
- int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
- struct evm_ima_xattr_data *xattr_value = NULL;
- struct modsig *modsig = NULL;
- int xattr_len = 0;
- bool violation_check;
- enum hash_algo hash_algo;
- unsigned int allowed_algos = 0;
- if (!ima_policy_flag || !S_ISREG(inode->i_mode))
- return 0;
- /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
- * bitmask based on the appraise/audit/measurement policy.
- * Included is the appraise submask.
- */
- action = ima_get_action(file_mnt_user_ns(file), inode, cred, secid,
- mask, func, &pcr, &template_desc, NULL,
- &allowed_algos);
- violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
- (ima_policy_flag & IMA_MEASURE));
- if (!action && !violation_check)
- return 0;
- must_appraise = action & IMA_APPRAISE;
- /* Is the appraise rule hook specific? */
- if (action & IMA_FILE_APPRAISE)
- func = FILE_CHECK;
- inode_lock(inode);
- if (action) {
- iint = integrity_inode_get(inode);
- if (!iint)
- rc = -ENOMEM;
- }
- if (!rc && violation_check)
- ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
- &pathbuf, &pathname, filename);
- inode_unlock(inode);
- if (rc)
- goto out;
- if (!action)
- goto out;
- mutex_lock(&iint->mutex);
- if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
- /* reset appraisal flags if ima_inode_post_setattr was called */
- iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
- IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
- IMA_NONACTION_FLAGS);
- /*
- * Re-evaulate the file if either the xattr has changed or the
- * kernel has no way of detecting file change on the filesystem.
- * (Limited to privileged mounted filesystems.)
- */
- if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) ||
- ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
- !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
- !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
- iint->flags &= ~IMA_DONE_MASK;
- iint->measured_pcrs = 0;
- }
- /* Detect and re-evaluate changes made to the backing file. */
- backing_inode = d_real_inode(file_dentry(file));
- if (backing_inode != inode &&
- (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) {
- if (!IS_I_VERSION(backing_inode) ||
- backing_inode->i_sb->s_dev != iint->real_dev ||
- backing_inode->i_ino != iint->real_ino ||
- !inode_eq_iversion(backing_inode, iint->version)) {
- iint->flags &= ~IMA_DONE_MASK;
- iint->measured_pcrs = 0;
- }
- }
- /* Determine if already appraised/measured based on bitmask
- * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
- * IMA_AUDIT, IMA_AUDITED)
- */
- iint->flags |= action;
- action &= IMA_DO_MASK;
- action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
- /* If target pcr is already measured, unset IMA_MEASURE action */
- if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
- action ^= IMA_MEASURE;
- /* HASH sets the digital signature and update flags, nothing else */
- if ((action & IMA_HASH) &&
- !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) {
- xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
- if ((xattr_value && xattr_len > 2) &&
- (xattr_value->type == EVM_IMA_XATTR_DIGSIG))
- set_bit(IMA_DIGSIG, &iint->atomic_flags);
- iint->flags |= IMA_HASHED;
- action ^= IMA_HASH;
- set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
- }
- /* Nothing to do, just return existing appraised status */
- if (!action) {
- if (must_appraise) {
- rc = mmap_violation_check(func, file, &pathbuf,
- &pathname, filename);
- if (!rc)
- rc = ima_get_cache_status(iint, func);
- }
- goto out_locked;
- }
- if ((action & IMA_APPRAISE_SUBMASK) ||
- strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) {
- /* read 'security.ima' */
- xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
- /*
- * Read the appended modsig if allowed by the policy, and allow
- * an additional measurement list entry, if needed, based on the
- * template format and whether the file was already measured.
- */
- if (iint->flags & IMA_MODSIG_ALLOWED) {
- rc = ima_read_modsig(func, buf, size, &modsig);
- if (!rc && ima_template_has_modsig(template_desc) &&
- iint->flags & IMA_MEASURED)
- action |= IMA_MEASURE;
- }
- }
- hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
- rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig);
- if (rc != 0 && rc != -EBADF && rc != -EINVAL)
- goto out_locked;
- if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
- pathname = ima_d_path(&file->f_path, &pathbuf, filename);
- if (action & IMA_MEASURE)
- ima_store_measurement(iint, file, pathname,
- xattr_value, xattr_len, modsig, pcr,
- template_desc);
- if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
- rc = ima_check_blacklist(iint, modsig, pcr);
- if (rc != -EPERM) {
- inode_lock(inode);
- rc = ima_appraise_measurement(func, iint, file,
- pathname, xattr_value,
- xattr_len, modsig);
- inode_unlock(inode);
- }
- if (!rc)
- rc = mmap_violation_check(func, file, &pathbuf,
- &pathname, filename);
- }
- if (action & IMA_AUDIT)
- ima_audit_measurement(iint, pathname);
- if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
- rc = 0;
- /* Ensure the digest was generated using an allowed algorithm */
- if (rc == 0 && must_appraise && allowed_algos != 0 &&
- (allowed_algos & (1U << hash_algo)) == 0) {
- rc = -EACCES;
- integrity_audit_msg(AUDIT_INTEGRITY_DATA, file_inode(file),
- pathname, "collect_data",
- "denied-hash-algorithm", rc, 0);
- }
- out_locked:
- if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
- !(iint->flags & IMA_NEW_FILE))
- rc = -EACCES;
- mutex_unlock(&iint->mutex);
- kfree(xattr_value);
- ima_free_modsig(modsig);
- out:
- if (pathbuf)
- __putname(pathbuf);
- if (must_appraise) {
- if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
- return -EACCES;
- if (file->f_mode & FMODE_WRITE)
- set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
- }
- return 0;
- }
- /**
- * ima_file_mmap - based on policy, collect/store measurement.
- * @file: pointer to the file to be measured (May be NULL)
- * @reqprot: protection requested by the application
- * @prot: protection that will be applied by the kernel
- * @flags: operational flags
- *
- * Measure files being mmapped executable 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_mmap(struct file *file, unsigned long reqprot,
- unsigned long prot, unsigned long flags)
- {
- u32 secid;
- if (file && (prot & PROT_EXEC)) {
- security_current_getsecid_subj(&secid);
- return process_measurement(file, current_cred(), secid, NULL,
- 0, MAY_EXEC, MMAP_CHECK);
- }
- return 0;
- }
- /**
- * ima_file_mprotect - based on policy, limit mprotect change
- * @vma: vm_area_struct protection is set to
- * @prot: contains the protection that will be applied by the kernel.
- *
- * Files can be mmap'ed read/write and later changed to execute to circumvent
- * IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore
- * would be taken before i_mutex), files can not be measured or appraised at
- * this point. Eliminate this integrity gap by denying the mprotect
- * PROT_EXECUTE change, if an mmap appraise policy rule exists.
- *
- * On mprotect change success, return 0. On failure, return -EACESS.
- */
- int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
- {
- struct ima_template_desc *template = NULL;
- struct file *file;
- char filename[NAME_MAX];
- char *pathbuf = NULL;
- const char *pathname = NULL;
- struct inode *inode;
- int result = 0;
- int action;
- u32 secid;
- int pcr;
- /* Is mprotect making an mmap'ed file executable? */
- if (!(ima_policy_flag & IMA_APPRAISE) || !vma->vm_file ||
- !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC))
- return 0;
- security_current_getsecid_subj(&secid);
- inode = file_inode(vma->vm_file);
- action = ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
- current_cred(), secid, MAY_EXEC, MMAP_CHECK,
- &pcr, &template, NULL, NULL);
- /* Is the mmap'ed file in policy? */
- if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))
- return 0;
- if (action & IMA_APPRAISE_SUBMASK)
- result = -EPERM;
- file = vma->vm_file;
- pathname = ima_d_path(&file->f_path, &pathbuf, filename);
- integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, pathname,
- "collect_data", "failed-mprotect", result, 0);
- if (pathbuf)
- __putname(pathbuf);
- return result;
- }
- /**
- * ima_bprm_check - based on policy, collect/store measurement.
- * @bprm: contains the linux_binprm structure
- *
- * The OS protects against an executable file, already open for write,
- * from being executed in deny_write_access() and an executable file,
- * already open for execute, from being modified in get_write_access().
- * So we can be certain that what we verify and measure here is actually
- * what is being executed.
- *
- * 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_bprm_check(struct linux_binprm *bprm)
- {
- int ret;
- u32 secid;
- security_current_getsecid_subj(&secid);
- ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
- MAY_EXEC, BPRM_CHECK);
- if (ret)
- return ret;
- security_cred_getsecid(bprm->cred, &secid);
- return process_measurement(bprm->file, bprm->cred, secid, NULL, 0,
- MAY_EXEC, CREDS_CHECK);
- }
- /**
- * ima_file_check - 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)
- {
- 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);
- }
- EXPORT_SYMBOL_GPL(ima_file_check);
- static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
- size_t buf_size)
- {
- struct integrity_iint_cache *iint = NULL, tmp_iint;
- int rc, hash_algo;
- if (ima_policy_flag) {
- iint = integrity_iint_find(inode);
- if (iint)
- mutex_lock(&iint->mutex);
- }
- if ((!iint || !(iint->flags & IMA_COLLECTED)) && file) {
- if (iint)
- mutex_unlock(&iint->mutex);
- memset(&tmp_iint, 0, sizeof(tmp_iint));
- tmp_iint.inode = inode;
- mutex_init(&tmp_iint.mutex);
- rc = ima_collect_measurement(&tmp_iint, file, NULL, 0,
- ima_hash_algo, NULL);
- if (rc < 0) {
- /* ima_hash could be allocated in case of failure. */
- if (rc != -ENOMEM)
- kfree(tmp_iint.ima_hash);
- return -EOPNOTSUPP;
- }
- iint = &tmp_iint;
- mutex_lock(&iint->mutex);
- }
- if (!iint)
- return -EOPNOTSUPP;
- /*
- * ima_file_hash can be called when ima_collect_measurement has still
- * not been called, we might not always have a hash.
- */
- if (!iint->ima_hash) {
- mutex_unlock(&iint->mutex);
- return -EOPNOTSUPP;
- }
- if (buf) {
- size_t copied_size;
- copied_size = min_t(size_t, iint->ima_hash->length, buf_size);
- memcpy(buf, iint->ima_hash->digest, copied_size);
- }
- hash_algo = iint->ima_hash->algo;
- mutex_unlock(&iint->mutex);
- if (iint == &tmp_iint)
- kfree(iint->ima_hash);
- return hash_algo;
- }
- /**
- * ima_file_hash - return a measurement of the file
- * @file: pointer to the file
- * @buf: buffer in which to store the hash
- * @buf_size: length of the buffer
- *
- * On success, return the hash algorithm (as defined in the enum hash_algo).
- * If buf is not NULL, this function also outputs the hash into buf.
- * If the hash is larger than buf_size, then only buf_size bytes will be copied.
- * It generally just makes sense to pass a buffer capable of holding the largest
- * possible hash: IMA_MAX_DIGEST_SIZE.
- * The file hash returned is based on the entire file, including the appended
- * signature.
- *
- * If the measurement cannot be performed, return -EOPNOTSUPP.
- * If the parameters are incorrect, return -EINVAL.
- */
- int ima_file_hash(struct file *file, char *buf, size_t buf_size)
- {
- if (!file)
- return -EINVAL;
- return __ima_inode_hash(file_inode(file), file, buf, buf_size);
- }
- EXPORT_SYMBOL_GPL(ima_file_hash);
- /**
- * ima_inode_hash - return the stored measurement if the inode has been hashed
- * and is in the iint cache.
- * @inode: pointer to the inode
- * @buf: buffer in which to store the hash
- * @buf_size: length of the buffer
- *
- * On success, return the hash algorithm (as defined in the enum hash_algo).
- * If buf is not NULL, this function also outputs the hash into buf.
- * If the hash is larger than buf_size, then only buf_size bytes will be copied.
- * It generally just makes sense to pass a buffer capable of holding the largest
- * possible hash: IMA_MAX_DIGEST_SIZE.
- * The hash returned is based on the entire contents, including the appended
- * signature.
- *
- * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
- * If the parameters are incorrect, return -EINVAL.
- */
- int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
- {
- if (!inode)
- return -EINVAL;
- return __ima_inode_hash(inode, NULL, buf, buf_size);
- }
- EXPORT_SYMBOL_GPL(ima_inode_hash);
- /**
- * ima_post_create_tmpfile - mark newly created tmpfile as new
- * @mnt_userns: user namespace of the mount the inode was found from
- * @inode: inode of the newly created tmpfile
- *
- * No measuring, appraising or auditing of newly created tmpfiles is needed.
- * Skip calling process_measurement(), but indicate which newly, created
- * tmpfiles are in policy.
- */
- void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
- struct inode *inode)
- {
- struct integrity_iint_cache *iint;
- int must_appraise;
- if (!ima_policy_flag || !S_ISREG(inode->i_mode))
- return;
- must_appraise = ima_must_appraise(mnt_userns, inode, MAY_ACCESS,
- FILE_CHECK);
- if (!must_appraise)
- return;
- /* Nothing to do if we can't allocate memory */
- iint = integrity_inode_get(inode);
- if (!iint)
- return;
- /* needed for writing the security xattrs */
- set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
- iint->ima_file_status = INTEGRITY_PASS;
- }
- /**
- * ima_post_path_mknod - mark as a new inode
- * @mnt_userns: user namespace of the mount the inode was found from
- * @dentry: newly created dentry
- *
- * Mark files created via the mknodat syscall as new, so that the
- * file data can be written later.
- */
- void ima_post_path_mknod(struct user_namespace *mnt_userns,
- struct dentry *dentry)
- {
- struct integrity_iint_cache *iint;
- struct inode *inode = dentry->d_inode;
- int must_appraise;
- if (!ima_policy_flag || !S_ISREG(inode->i_mode))
- return;
- must_appraise = ima_must_appraise(mnt_userns, inode, MAY_ACCESS,
- FILE_CHECK);
- if (!must_appraise)
- return;
- /* Nothing to do if we can't allocate memory */
- iint = integrity_inode_get(inode);
- if (!iint)
- return;
- /* needed for re-opening empty files */
- iint->flags |= IMA_NEW_FILE;
- }
- /**
- * ima_read_file - pre-measure/appraise hook decision based on policy
- * @file: pointer to the file to be measured/appraised/audit
- * @read_id: caller identifier
- * @contents: whether a subsequent call will be made to ima_post_read_file()
- *
- * Permit reading a file based on policy. The policy rules are written
- * in terms of the policy identifier. Appraising the integrity of
- * a file requires a file descriptor.
- *
- * For permission return 0, otherwise return -EACCES.
- */
- int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
- bool contents)
- {
- enum ima_hooks func;
- u32 secid;
- /*
- * Do devices using pre-allocated memory run the risk of the
- * firmware being accessible to the device prior to the completion
- * of IMA's signature verification any more than when using two
- * buffers? It may be desirable to include the buffer address
- * in this API and walk all the dma_map_single() mappings to check.
- */
- /*
- * There will be a call made to ima_post_read_file() with
- * a filled buffer, so we don't need to perform an extra
- * read early here.
- */
- if (contents)
- return 0;
- /* Read entire file for all partial reads. */
- func = read_idmap[read_id] ?: FILE_CHECK;
- security_current_getsecid_subj(&secid);
- return process_measurement(file, current_cred(), secid, NULL,
- 0, MAY_READ, func);
- }
- const int read_idmap[READING_MAX_ID] = {
- [READING_FIRMWARE] = FIRMWARE_CHECK,
- [READING_MODULE] = MODULE_CHECK,
- [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
- [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
- [READING_POLICY] = POLICY_CHECK
- };
- /**
- * ima_post_read_file - in memory collect/appraise/audit measurement
- * @file: pointer to the file to be measured/appraised/audit
- * @buf: pointer to in memory file contents
- * @size: size of in memory file contents
- * @read_id: caller identifier
- *
- * Measure/appraise/audit in memory file based on policy. Policy rules
- * are written in terms of a policy identifier.
- *
- * 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_post_read_file(struct file *file, void *buf, loff_t size,
- enum kernel_read_file_id read_id)
- {
- enum ima_hooks func;
- u32 secid;
- /* permit signed certs */
- if (!file && read_id == READING_X509_CERTIFICATE)
- return 0;
- if (!file || !buf || size == 0) { /* should never happen */
- if (ima_appraise & IMA_APPRAISE_ENFORCE)
- return -EACCES;
- return 0;
- }
- func = read_idmap[read_id] ?: FILE_CHECK;
- security_current_getsecid_subj(&secid);
- return process_measurement(file, current_cred(), secid, buf, size,
- MAY_READ, func);
- }
- /**
- * ima_load_data - appraise decision based on policy
- * @id: kernel load data caller identifier
- * @contents: whether the full contents will be available in a later
- * call to ima_post_load_data().
- *
- * Callers of this LSM hook can not measure, appraise, or audit the
- * data provided by userspace. Enforce policy rules requiring a file
- * signature (eg. kexec'ed kernel image).
- *
- * For permission return 0, otherwise return -EACCES.
- */
- int ima_load_data(enum kernel_load_data_id id, bool contents)
- {
- bool ima_enforce, sig_enforce;
- ima_enforce =
- (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
- switch (id) {
- case LOADING_KEXEC_IMAGE:
- if (IS_ENABLED(CONFIG_KEXEC_SIG)
- && arch_ima_get_secureboot()) {
- pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
- return -EACCES;
- }
- if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
- pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
- return -EACCES; /* INTEGRITY_UNKNOWN */
- }
- break;
- case LOADING_FIRMWARE:
- if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE) && !contents) {
- pr_err("Prevent firmware sysfs fallback loading.\n");
- return -EACCES; /* INTEGRITY_UNKNOWN */
- }
- break;
- case LOADING_MODULE:
- sig_enforce = is_module_sig_enforced();
- if (ima_enforce && (!sig_enforce
- && (ima_appraise & IMA_APPRAISE_MODULES))) {
- pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
- return -EACCES; /* INTEGRITY_UNKNOWN */
- }
- break;
- default:
- break;
- }
- return 0;
- }
- /**
- * ima_post_load_data - appraise decision based on policy
- * @buf: pointer to in memory file contents
- * @size: size of in memory file contents
- * @load_id: kernel load data caller identifier
- * @description: @load_id-specific description of contents
- *
- * Measure/appraise/audit in memory buffer based on policy. Policy rules
- * are written in terms of a policy identifier.
- *
- * 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_post_load_data(char *buf, loff_t size,
- enum kernel_load_data_id load_id,
- char *description)
- {
- if (load_id == LOADING_FIRMWARE) {
- if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
- (ima_appraise & IMA_APPRAISE_ENFORCE)) {
- pr_err("Prevent firmware loading_store.\n");
- return -EACCES; /* INTEGRITY_UNKNOWN */
- }
- return 0;
- }
- return 0;
- }
- /**
- * process_buffer_measurement - Measure the buffer or the buffer data hash
- * @mnt_userns: user namespace of the mount the inode was found from
- * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
- * @buf: pointer to the buffer that needs to be added to the log.
- * @size: size of buffer(in bytes).
- * @eventname: event name to be used for the buffer entry.
- * @func: IMA hook
- * @pcr: pcr to extend the measurement
- * @func_data: func specific data, may be NULL
- * @buf_hash: measure buffer data hash
- * @digest: buffer digest will be written to
- * @digest_len: buffer length
- *
- * Based on policy, either the buffer data or buffer data hash is measured
- *
- * Return: 0 if the buffer has been successfully measured, 1 if the digest
- * has been written to the passed location but not added to a measurement entry,
- * a negative value otherwise.
- */
- int process_buffer_measurement(struct user_namespace *mnt_userns,
- struct inode *inode, const void *buf, int size,
- const char *eventname, enum ima_hooks func,
- int pcr, const char *func_data,
- bool buf_hash, u8 *digest, size_t digest_len)
- {
- int ret = 0;
- const char *audit_cause = "ENOMEM";
- struct ima_template_entry *entry = NULL;
- struct integrity_iint_cache iint = {};
- struct ima_event_data event_data = {.iint = &iint,
- .filename = eventname,
- .buf = buf,
- .buf_len = size};
- struct ima_template_desc *template;
- struct ima_max_digest_data hash;
- char digest_hash[IMA_MAX_DIGEST_SIZE];
- int digest_hash_len = hash_digest_size[ima_hash_algo];
- int violation = 0;
- int action = 0;
- u32 secid;
- if (digest && digest_len < digest_hash_len)
- return -EINVAL;
- if (!ima_policy_flag && !digest)
- return -ENOENT;
- template = ima_template_desc_buf();
- if (!template) {
- ret = -EINVAL;
- audit_cause = "ima_template_desc_buf";
- goto out;
- }
- /*
- * Both LSM hooks and auxilary based buffer measurements are
- * based on policy. To avoid code duplication, differentiate
- * between the LSM hooks and auxilary buffer measurements,
- * retrieving the policy rule information only for the LSM hook
- * buffer measurements.
- */
- if (func) {
- security_current_getsecid_subj(&secid);
- action = ima_get_action(mnt_userns, inode, current_cred(),
- secid, 0, func, &pcr, &template,
- func_data, NULL);
- if (!(action & IMA_MEASURE) && !digest)
- return -ENOENT;
- }
- if (!pcr)
- pcr = CONFIG_IMA_MEASURE_PCR_IDX;
- iint.ima_hash = &hash.hdr;
- iint.ima_hash->algo = ima_hash_algo;
- iint.ima_hash->length = hash_digest_size[ima_hash_algo];
- ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
- if (ret < 0) {
- audit_cause = "hashing_error";
- goto out;
- }
- if (buf_hash) {
- memcpy(digest_hash, hash.hdr.digest, digest_hash_len);
- ret = ima_calc_buffer_hash(digest_hash, digest_hash_len,
- iint.ima_hash);
- if (ret < 0) {
- audit_cause = "hashing_error";
- goto out;
- }
- event_data.buf = digest_hash;
- event_data.buf_len = digest_hash_len;
- }
- if (digest)
- memcpy(digest, iint.ima_hash->digest, digest_hash_len);
- if (!ima_policy_flag || (func && !(action & IMA_MEASURE)))
- return 1;
- ret = ima_alloc_init_template(&event_data, &entry, template);
- if (ret < 0) {
- audit_cause = "alloc_entry";
- goto out;
- }
- ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr);
- if (ret < 0) {
- audit_cause = "store_entry";
- ima_free_template_entry(entry);
- }
- out:
- if (ret < 0)
- integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL, eventname,
- func_measure_str(func),
- audit_cause, ret, 0, ret);
- return ret;
- }
- /**
- * ima_kexec_cmdline - measure kexec cmdline boot args
- * @kernel_fd: file descriptor of the kexec kernel being loaded
- * @buf: pointer to buffer
- * @size: size of buffer
- *
- * Buffers can only be measured, not appraised.
- */
- void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
- {
- struct fd f;
- if (!buf || !size)
- return;
- f = fdget(kernel_fd);
- if (!f.file)
- return;
- process_buffer_measurement(file_mnt_user_ns(f.file), file_inode(f.file),
- buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
- NULL, false, NULL, 0);
- fdput(f);
- }
- /**
- * ima_measure_critical_data - measure kernel integrity critical data
- * @event_label: unique event label for grouping and limiting critical data
- * @event_name: event name for the record in the IMA measurement list
- * @buf: pointer to buffer data
- * @buf_len: length of buffer data (in bytes)
- * @hash: measure buffer data hash
- * @digest: buffer digest will be written to
- * @digest_len: buffer length
- *
- * Measure data critical to the integrity of the kernel into the IMA log
- * and extend the pcr. Examples of critical data could be various data
- * structures, policies, and states stored in kernel memory that can
- * impact the integrity of the system.
- *
- * Return: 0 if the buffer has been successfully measured, 1 if the digest
- * has been written to the passed location but not added to a measurement entry,
- * a negative value otherwise.
- */
- int ima_measure_critical_data(const char *event_label,
- const char *event_name,
- const void *buf, size_t buf_len,
- bool hash, u8 *digest, size_t digest_len)
- {
- if (!event_name || !event_label || !buf || !buf_len)
- return -ENOPARAM;
- return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len,
- event_name, CRITICAL_DATA, 0,
- event_label, hash, digest,
- digest_len);
- }
- EXPORT_SYMBOL_GPL(ima_measure_critical_data);
- static int __init init_ima(void)
- {
- int error;
- ima_appraise_parse_cmdline();
- ima_init_template_list();
- hash_setup(CONFIG_IMA_DEFAULT_HASH);
- error = ima_init();
- if (error && strcmp(hash_algo_name[ima_hash_algo],
- CONFIG_IMA_DEFAULT_HASH) != 0) {
- pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
- hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
- hash_setup_done = 0;
- hash_setup(CONFIG_IMA_DEFAULT_HASH);
- error = ima_init();
- }
- if (error)
- return error;
- error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier);
- if (error)
- pr_warn("Couldn't register LSM notifier, error %d\n", error);
- if (!error)
- ima_update_policy_flags();
- return error;
- }
- late_initcall(init_ima); /* Start IMA after the TPM is available */
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