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- // 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/iversion.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)
- {
- int i;
- for (i = 0; i < entry->template_desc->num_fields; i++)
- kfree(entry->template_data[i].data);
- kfree(entry->digests);
- kfree(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)
- {
- struct ima_template_desc *template_desc;
- struct tpm_digest *digests;
- int i, result = 0;
- if (desc)
- template_desc = desc;
- else
- template_desc = ima_template_desc_current();
- *entry = kzalloc(struct_size(*entry, template_data,
- template_desc->num_fields), GFP_NOFS);
- if (!*entry)
- return -ENOMEM;
- digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
- sizeof(*digests), GFP_NOFS);
- if (!digests) {
- kfree(*entry);
- *entry = NULL;
- return -ENOMEM;
- }
- (*entry)->digests = digests;
- (*entry)->template_desc = template_desc;
- for (i = 0; i < template_desc->num_fields; i++) {
- const struct ima_template_field *field =
- template_desc->fields[i];
- u32 len;
- result = field->field_init(event_data,
- &((*entry)->template_data[i]));
- if (result != 0)
- goto out;
- len = (*entry)->template_data[i].len;
- (*entry)->template_data_len += sizeof(len);
- (*entry)->template_data_len += len;
- }
- return 0;
- out:
- ima_free_template_entry(*entry);
- *entry = NULL;
- return result;
- }
- /*
- * 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)
- {
- static const char op[] = "add_template_measure";
- static const char audit_cause[] = "hashing_error";
- char *template_name = entry->template_desc->name;
- int result;
- if (!violation) {
- result = ima_calc_field_array_hash(&entry->template_data[0],
- entry);
- if (result < 0) {
- integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
- template_name, op,
- audit_cause, result, 0);
- return result;
- }
- }
- entry->pcr = pcr;
- result = ima_add_template_entry(entry, violation, op, inode, filename);
- return result;
- }
- /*
- * 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 integrity_iint_cache *iint,
- const char *op, const char *cause)
- {
- struct ima_template_entry *entry;
- struct inode *inode = file_inode(file);
- struct ima_event_data event_data = { .iint = iint,
- .file = file,
- .filename = filename,
- .violation = cause };
- int violation = 1;
- int result;
- /* can overflow, only indicator */
- atomic_long_inc(&ima_htable.violations);
- result = ima_alloc_init_template(&event_data, &entry, NULL);
- if (result < 0) {
- result = -ENOMEM;
- goto err_out;
- }
- result = ima_store_template(entry, violation, inode,
- filename, CONFIG_IMA_MEASURE_PCR_IDX);
- if (result < 0)
- ima_free_template_entry(entry);
- err_out:
- integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
- op, cause, result, 0);
- }
- /**
- * ima_get_action - appraise & measure decision based on policy.
- * @mnt_userns: user namespace 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
- * mask: contains the permission mask
- * fsmagic: hex value
- *
- * Returns IMA_MEASURE, IMA_APPRAISE mask.
- *
- */
- int ima_get_action(struct user_namespace *mnt_userns, 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)
- {
- int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
- flags &= ima_policy_flag;
- return ima_match_policy(mnt_userns, inode, cred, secid, func, mask,
- flags, pcr, template_desc, func_data,
- allowed_algos);
- }
- static int ima_get_verity_digest(struct integrity_iint_cache *iint,
- struct ima_max_digest_data *hash)
- {
- enum hash_algo verity_alg;
- int ret;
- /*
- * On failure, 'measure' policy rules will result in a file data
- * hash containing 0's.
- */
- ret = fsverity_get_digest(iint->inode, hash->digest, &verity_alg);
- if (ret)
- return ret;
- /*
- * Unlike in the case of actually calculating the file hash, in
- * the fsverity case regardless of the hash algorithm, return
- * the verity digest to be included in the measurement list. A
- * mismatch between the verity algorithm and the xattr signature
- * algorithm, if one exists, will be detected later.
- */
- hash->hdr.algo = verity_alg;
- hash->hdr.length = hash_digest_size[verity_alg];
- return 0;
- }
- /*
- * 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 integrity_iint_cache *iint,
- struct file *file, void *buf, loff_t size,
- enum hash_algo algo, struct modsig *modsig)
- {
- const char *audit_cause = "failed";
- struct inode *inode = file_inode(file);
- struct inode *real_inode = d_real_inode(file_dentry(file));
- const char *filename = file->f_path.dentry->d_name.name;
- struct ima_max_digest_data hash;
- int result = 0;
- int length;
- void *tmpbuf;
- u64 i_version;
- /*
- * Always collect the modsig, because IMA might have already collected
- * the file digest without collecting the modsig in a previous
- * measurement rule.
- */
- if (modsig)
- ima_collect_modsig(modsig, buf, size);
- if (iint->flags & IMA_COLLECTED)
- goto out;
- /*
- * Detecting file change is based on i_version. On filesystems
- * which do not support i_version, support was originally limited
- * to an initial measurement/appraisal/audit, but was modified to
- * assume the file changed.
- */
- i_version = inode_query_iversion(inode);
- hash.hdr.algo = algo;
- hash.hdr.length = hash_digest_size[algo];
- /* Initialize hash digest to 0's in case of failure */
- memset(&hash.digest, 0, sizeof(hash.digest));
- if (iint->flags & IMA_VERITY_REQUIRED) {
- result = ima_get_verity_digest(iint, &hash);
- switch (result) {
- case 0:
- break;
- case -ENODATA:
- audit_cause = "no-verity-digest";
- break;
- default:
- audit_cause = "invalid-verity-digest";
- break;
- }
- } else if (buf) {
- result = ima_calc_buffer_hash(buf, size, &hash.hdr);
- } else {
- result = ima_calc_file_hash(file, &hash.hdr);
- }
- if (result && result != -EBADF && result != -EINVAL)
- goto out;
- length = sizeof(hash.hdr) + hash.hdr.length;
- tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
- if (!tmpbuf) {
- result = -ENOMEM;
- goto out;
- }
- iint->ima_hash = tmpbuf;
- memcpy(iint->ima_hash, &hash, length);
- iint->version = i_version;
- if (real_inode != inode) {
- iint->real_ino = real_inode->i_ino;
- iint->real_dev = real_inode->i_sb->s_dev;
- }
- /* Possibly temporary failure due to type of read (eg. O_DIRECT) */
- if (!result)
- iint->flags |= IMA_COLLECTED;
- out:
- if (result) {
- if (file->f_flags & O_DIRECT)
- audit_cause = "failed(directio)";
- integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
- filename, "collect_data", audit_cause,
- result, 0);
- }
- return result;
- }
- /*
- * 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 integrity_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)
- {
- static const char op[] = "add_template_measure";
- static const char audit_cause[] = "ENOMEM";
- int result = -ENOMEM;
- struct inode *inode = file_inode(file);
- struct ima_template_entry *entry;
- struct ima_event_data event_data = { .iint = iint,
- .file = file,
- .filename = filename,
- .xattr_value = xattr_value,
- .xattr_len = xattr_len,
- .modsig = modsig };
- int violation = 0;
- /*
- * We still need to store the measurement in the case of MODSIG because
- * we only have its contents to put in the list at the time of
- * appraisal, but a file measurement from earlier might already exist in
- * the measurement list.
- */
- if (iint->measured_pcrs & (0x1 << pcr) && !modsig)
- return;
- result = ima_alloc_init_template(&event_data, &entry, template_desc);
- if (result < 0) {
- integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
- op, audit_cause, result, 0);
- return;
- }
- result = ima_store_template(entry, violation, inode, filename, pcr);
- if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
- iint->flags |= IMA_MEASURED;
- iint->measured_pcrs |= (0x1 << pcr);
- }
- if (result < 0)
- ima_free_template_entry(entry);
- }
- void ima_audit_measurement(struct integrity_iint_cache *iint,
- const unsigned char *filename)
- {
- struct audit_buffer *ab;
- char *hash;
- const char *algo_name = hash_algo_name[iint->ima_hash->algo];
- int i;
- if (iint->flags & IMA_AUDITED)
- return;
- hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
- if (!hash)
- return;
- for (i = 0; i < iint->ima_hash->length; i++)
- hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
- hash[i * 2] = '\0';
- ab = audit_log_start(audit_context(), GFP_KERNEL,
- AUDIT_INTEGRITY_RULE);
- if (!ab)
- goto out;
- audit_log_format(ab, "file=");
- audit_log_untrustedstring(ab, filename);
- audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);
- audit_log_task_info(ab);
- audit_log_end(ab);
- iint->flags |= IMA_AUDITED;
- out:
- kfree(hash);
- return;
- }
- /*
- * 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)
- {
- char *pathname = NULL;
- *pathbuf = __getname();
- if (*pathbuf) {
- pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
- if (IS_ERR(pathname)) {
- __putname(*pathbuf);
- *pathbuf = NULL;
- pathname = NULL;
- }
- }
- if (!pathname) {
- strscpy(namebuf, path->dentry->d_name.name, NAME_MAX);
- pathname = namebuf;
- }
- return pathname;
- }
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