| /* |
| * 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. |
| */ |
| #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 "ima.h" |
| |
| int ima_initialized; |
| |
| char *ima_hash = "sha1"; |
| static int __init hash_setup(char *str) |
| { |
| if (strncmp(str, "md5", 3) == 0) |
| ima_hash = "md5"; |
| return 1; |
| } |
| __setup("ima_hash=", hash_setup); |
| |
| struct ima_imbalance { |
| struct hlist_node node; |
| unsigned long fsmagic; |
| }; |
| |
| /* |
| * ima_limit_imbalance - emit one imbalance message per filesystem type |
| * |
| * Maintain list of filesystem types that do not measure files properly. |
| * Return false if unknown, true if known. |
| */ |
| static bool ima_limit_imbalance(struct file *file) |
| { |
| static DEFINE_SPINLOCK(ima_imbalance_lock); |
| static HLIST_HEAD(ima_imbalance_list); |
| |
| struct super_block *sb = file->f_dentry->d_sb; |
| struct ima_imbalance *entry; |
| struct hlist_node *node; |
| bool found = false; |
| |
| rcu_read_lock(); |
| hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) { |
| if (entry->fsmagic == sb->s_magic) { |
| found = true; |
| break; |
| } |
| } |
| rcu_read_unlock(); |
| if (found) |
| goto out; |
| |
| entry = kmalloc(sizeof(*entry), GFP_NOFS); |
| if (!entry) |
| goto out; |
| entry->fsmagic = sb->s_magic; |
| spin_lock(&ima_imbalance_lock); |
| /* |
| * we could have raced and something else might have added this fs |
| * to the list, but we don't really care |
| */ |
| hlist_add_head_rcu(&entry->node, &ima_imbalance_list); |
| spin_unlock(&ima_imbalance_lock); |
| printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n", |
| entry->fsmagic); |
| out: |
| return found; |
| } |
| |
| /* ima_read_write_check - reflect possible reading/writing errors in the PCR. |
| * |
| * When opening a file for read, if the file is already open for write, |
| * the file could change, resulting in a file measurement error. |
| * |
| * Opening a file for write, if the file is already open for read, results |
| * in a time of measure, time of use (ToMToU) error. |
| * |
| * In either case invalidate the PCR. |
| */ |
| enum iint_pcr_error { TOMTOU, OPEN_WRITERS }; |
| static void ima_read_write_check(enum iint_pcr_error error, |
| struct ima_iint_cache *iint, |
| struct inode *inode, |
| const unsigned char *filename) |
| { |
| switch (error) { |
| case TOMTOU: |
| if (iint->readcount > 0) |
| ima_add_violation(inode, filename, "invalid_pcr", |
| "ToMToU"); |
| break; |
| case OPEN_WRITERS: |
| if (iint->writecount > 0) |
| ima_add_violation(inode, filename, "invalid_pcr", |
| "open_writers"); |
| break; |
| } |
| } |
| |
| /* |
| * Update the counts given an fmode_t |
| */ |
| static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode) |
| { |
| BUG_ON(!mutex_is_locked(&iint->mutex)); |
| |
| if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) |
| iint->readcount++; |
| if (mode & FMODE_WRITE) |
| iint->writecount++; |
| } |
| |
| /* |
| * ima_counts_get - increment file counts |
| * |
| * Maintain read/write counters for all files, but 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. |
| * |
| */ |
| void ima_counts_get(struct file *file) |
| { |
| struct dentry *dentry = file->f_path.dentry; |
| struct inode *inode = dentry->d_inode; |
| fmode_t mode = file->f_mode; |
| struct ima_iint_cache *iint; |
| int rc; |
| |
| if (!iint_initialized || !S_ISREG(inode->i_mode)) |
| return; |
| iint = ima_iint_find_get(inode); |
| if (!iint) |
| return; |
| mutex_lock(&iint->mutex); |
| if (!ima_initialized) |
| goto out; |
| rc = ima_must_measure(iint, inode, MAY_READ, FILE_CHECK); |
| if (rc < 0) |
| goto out; |
| |
| if (mode & FMODE_WRITE) { |
| ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name); |
| goto out; |
| } |
| ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name); |
| out: |
| ima_inc_counts(iint, file->f_mode); |
| mutex_unlock(&iint->mutex); |
| |
| kref_put(&iint->refcount, iint_free); |
| } |
| |
| /* |
| * Decrement ima counts |
| */ |
| static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode, |
| struct file *file) |
| { |
| mode_t mode = file->f_mode; |
| BUG_ON(!mutex_is_locked(&iint->mutex)); |
| |
| if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) |
| iint->readcount--; |
| if (mode & FMODE_WRITE) { |
| iint->writecount--; |
| if (iint->writecount == 0) { |
| if (iint->version != inode->i_version) |
| iint->flags &= ~IMA_MEASURED; |
| } |
| } |
| |
| if (((iint->readcount < 0) || |
| (iint->writecount < 0)) && |
| !ima_limit_imbalance(file)) { |
| printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld)\n", |
| __func__, iint->readcount, iint->writecount); |
| dump_stack(); |
| } |
| } |
| |
| /** |
| * ima_file_free - called on __fput() |
| * @file: pointer to file structure being freed |
| * |
| * Flag files that changed, based on i_version; |
| * and decrement the iint readcount/writecount. |
| */ |
| void ima_file_free(struct file *file) |
| { |
| struct inode *inode = file->f_dentry->d_inode; |
| struct ima_iint_cache *iint; |
| |
| if (!iint_initialized || !S_ISREG(inode->i_mode)) |
| return; |
| iint = ima_iint_find_get(inode); |
| if (!iint) |
| return; |
| |
| mutex_lock(&iint->mutex); |
| ima_dec_counts(iint, inode, file); |
| mutex_unlock(&iint->mutex); |
| kref_put(&iint->refcount, iint_free); |
| } |
| |
| static int process_measurement(struct file *file, const unsigned char *filename, |
| int mask, int function) |
| { |
| struct inode *inode = file->f_dentry->d_inode; |
| struct ima_iint_cache *iint; |
| int rc = 0; |
| |
| if (!ima_initialized || !S_ISREG(inode->i_mode)) |
| return 0; |
| iint = ima_iint_find_get(inode); |
| if (!iint) |
| return -ENOMEM; |
| |
| mutex_lock(&iint->mutex); |
| rc = ima_must_measure(iint, inode, mask, function); |
| if (rc != 0) |
| goto out; |
| |
| rc = ima_collect_measurement(iint, file); |
| if (!rc) |
| ima_store_measurement(iint, file, filename); |
| out: |
| mutex_unlock(&iint->mutex); |
| kref_put(&iint->refcount, iint_free); |
| return rc; |
| } |
| |
| /** |
| * ima_file_mmap - based on policy, collect/store measurement. |
| * @file: pointer to the file to be measured (May be NULL) |
| * @prot: contains the protection that will be applied by the kernel. |
| * |
| * Measure files being mmapped executable based on the ima_must_measure() |
| * policy decision. |
| * |
| * Return 0 on success, an error code on failure. |
| * (Based on the results of appraise_measurement().) |
| */ |
| int ima_file_mmap(struct file *file, unsigned long prot) |
| { |
| int rc; |
| |
| if (!file) |
| return 0; |
| if (prot & PROT_EXEC) |
| rc = process_measurement(file, file->f_dentry->d_name.name, |
| MAY_EXEC, FILE_MMAP); |
| 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. |
| * |
| * Return 0 on success, an error code on failure. |
| * (Based on the results of appraise_measurement().) |
| */ |
| int ima_bprm_check(struct linux_binprm *bprm) |
| { |
| int rc; |
| |
| rc = process_measurement(bprm->file, bprm->filename, |
| MAY_EXEC, BPRM_CHECK); |
| return 0; |
| } |
| |
| /** |
| * ima_path_check - based on policy, collect/store measurement. |
| * @file: pointer to the file to be measured |
| * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE |
| * |
| * Measure files based on the ima_must_measure() policy decision. |
| * |
| * Always return 0 and audit dentry_open failures. |
| * (Return code will be based upon measurement appraisal.) |
| */ |
| int ima_file_check(struct file *file, int mask) |
| { |
| int rc; |
| |
| rc = process_measurement(file, file->f_dentry->d_name.name, |
| mask & (MAY_READ | MAY_WRITE | MAY_EXEC), |
| FILE_CHECK); |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(ima_file_check); |
| |
| static int __init init_ima(void) |
| { |
| int error; |
| |
| error = ima_init(); |
| ima_initialized = 1; |
| return error; |
| } |
| |
| static void __exit cleanup_ima(void) |
| { |
| ima_cleanup(); |
| } |
| |
| late_initcall(init_ima); /* Start IMA after the TPM is available */ |
| |
| MODULE_DESCRIPTION("Integrity Measurement Architecture"); |
| MODULE_LICENSE("GPL"); |