| /* |
| * Copyright (C) 2005,2006,2007,2008 IBM Corporation |
| * |
| * Authors: |
| * Reiner Sailer <sailer@watson.ibm.com> |
| * Serge Hallyn <serue@us.ibm.com> |
| * Kylene Hall <kylene@us.ibm.com> |
| * Mimi Zohar <zohar@us.ibm.com> |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License as |
| * published by the Free Software Foundation, version 2 of the |
| * License. |
| * |
| * File: ima_main.c |
| * implements the IMA hooks: ima_bprm_check, ima_file_mmap, |
| * and ima_file_check. |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/module.h> |
| #include <linux/file.h> |
| #include <linux/binfmts.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 "ima.h" |
| |
| #ifdef CONFIG_IMA_APPRAISE |
| int ima_appraise = IMA_APPRAISE_ENFORCE; |
| #else |
| int ima_appraise; |
| #endif |
| |
| int ima_hash_algo = HASH_ALGO_SHA1; |
| static int hash_setup_done; |
| |
| 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 |
| return 1; |
| goto out; |
| } |
| |
| i = match_string(hash_algo_name, HASH_ALGO__LAST, str); |
| if (i < 0) |
| return 1; |
| |
| ima_hash_algo = i; |
| out: |
| hash_setup_done = 1; |
| return 1; |
| } |
| __setup("ima_hash=", hash_setup); |
| |
| /* |
| * 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 ((atomic_read(&inode->i_writecount) > 0) && 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 *inode = file_inode(file); |
| struct integrity_iint_cache *iint = NULL; |
| struct ima_template_desc *template_desc; |
| 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; |
| int xattr_len = 0; |
| bool violation_check; |
| enum hash_algo hash_algo; |
| |
| 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(inode, cred, secid, mask, func, &pcr); |
| 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_ACTION_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; |
| } |
| |
| /* 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 = ima_get_cache_status(iint, func); |
| goto out_locked; |
| } |
| |
| template_desc = ima_template_desc_current(); |
| 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); |
| |
| hash_algo = ima_get_hash_algo(xattr_value, xattr_len); |
| |
| rc = ima_collect_measurement(iint, file, buf, size, hash_algo); |
| 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, pcr); |
| if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) { |
| inode_lock(inode); |
| rc = ima_appraise_measurement(func, iint, file, pathname, |
| xattr_value, xattr_len); |
| inode_unlock(inode); |
| } |
| if (action & IMA_AUDIT) |
| ima_audit_measurement(iint, pathname); |
| |
| if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO)) |
| 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); |
| 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_task_getsecid(current, &secid); |
| return process_measurement(file, current_cred(), secid, NULL, |
| 0, MAY_EXEC, MMAP_CHECK); |
| } |
| |
| return 0; |
| } |
| |
| /** |
| * 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_task_getsecid(current, &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_path_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_task_getsecid(current, &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); |
| |
| /** |
| * ima_post_path_mknod - mark as a new inode |
| * @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 dentry *dentry) |
| { |
| struct integrity_iint_cache *iint; |
| struct inode *inode = dentry->d_inode; |
| int must_appraise; |
| |
| must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK); |
| if (!must_appraise) |
| return; |
| |
| iint = integrity_inode_get(inode); |
| if (iint) |
| 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 |
| * |
| * 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) |
| { |
| /* |
| * READING_FIRMWARE_PREALLOC_BUFFER |
| * |
| * 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? |
| */ |
| return 0; |
| } |
| |
| static int read_idmap[READING_MAX_ID] = { |
| [READING_FIRMWARE] = FIRMWARE_CHECK, |
| [READING_FIRMWARE_PREALLOC_BUFFER] = 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; |
| |
| if (!file && read_id == READING_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; |
| } |
| |
| /* 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_task_getsecid(current, &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 |
| * |
| * Callers of this LSM hook can not measure, appraise, or audit the |
| * data provided by userspace. Enforce policy rules requring 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 sig_enforce; |
| |
| if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE) |
| return 0; |
| |
| switch (id) { |
| case LOADING_KEXEC_IMAGE: |
| if (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_appraise & IMA_APPRAISE_FIRMWARE) { |
| pr_err("Prevent firmware sysfs fallback loading.\n"); |
| return -EACCES; /* INTEGRITY_UNKNOWN */ |
| } |
| break; |
| case LOADING_MODULE: |
| sig_enforce = is_module_sig_enforced(); |
| |
| if (!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 */ |
| } |
| default: |
| break; |
| } |
| return 0; |
| } |
| |
| static int __init init_ima(void) |
| { |
| int error; |
| |
| 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) |
| ima_update_policy_flag(); |
| |
| return error; |
| } |
| |
| late_initcall(init_ima); /* Start IMA after the TPM is available */ |
| |
| MODULE_DESCRIPTION("Integrity Measurement Architecture"); |
| MODULE_LICENSE("GPL"); |