2 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
5 * Reiner Sailer <sailer@watson.ibm.com>
6 * Serge Hallyn <serue@us.ibm.com>
7 * Kylene Hall <kylene@us.ibm.com>
8 * Mimi Zohar <zohar@us.ibm.com>
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License as
12 * published by the Free Software Foundation, version 2 of the
16 * implements the IMA hooks: ima_bprm_check, ima_file_mmap,
19 #include <linux/module.h>
20 #include <linux/file.h>
21 #include <linux/binfmts.h>
22 #include <linux/mount.h>
23 #include <linux/mman.h>
29 char *ima_hash = "sha1";
30 static int __init hash_setup(char *str)
32 if (strncmp(str, "md5", 3) == 0)
36 __setup("ima_hash=", hash_setup);
38 struct ima_imbalance {
39 struct hlist_node node;
40 unsigned long fsmagic;
44 * ima_limit_imbalance - emit one imbalance message per filesystem type
46 * Maintain list of filesystem types that do not measure files properly.
47 * Return false if unknown, true if known.
49 static bool ima_limit_imbalance(struct file *file)
51 static DEFINE_SPINLOCK(ima_imbalance_lock);
52 static HLIST_HEAD(ima_imbalance_list);
54 struct super_block *sb = file->f_dentry->d_sb;
55 struct ima_imbalance *entry;
56 struct hlist_node *node;
60 hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) {
61 if (entry->fsmagic == sb->s_magic) {
70 entry = kmalloc(sizeof(*entry), GFP_NOFS);
73 entry->fsmagic = sb->s_magic;
74 spin_lock(&ima_imbalance_lock);
76 * we could have raced and something else might have added this fs
77 * to the list, but we don't really care
79 hlist_add_head_rcu(&entry->node, &ima_imbalance_list);
80 spin_unlock(&ima_imbalance_lock);
81 printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n",
87 /* ima_read_write_check - reflect possible reading/writing errors in the PCR.
89 * When opening a file for read, if the file is already open for write,
90 * the file could change, resulting in a file measurement error.
92 * Opening a file for write, if the file is already open for read, results
93 * in a time of measure, time of use (ToMToU) error.
95 * In either case invalidate the PCR.
97 enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
98 static void ima_read_write_check(enum iint_pcr_error error,
99 struct ima_iint_cache *iint,
101 const unsigned char *filename)
105 if (iint->readcount > 0)
106 ima_add_violation(inode, filename, "invalid_pcr",
110 if (iint->writecount > 0)
111 ima_add_violation(inode, filename, "invalid_pcr",
118 * Update the counts given an fmode_t
120 static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
122 BUG_ON(!mutex_is_locked(&iint->mutex));
125 if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
127 if (mode & FMODE_WRITE)
132 * ima_counts_get - increment file counts
134 * Maintain read/write counters for all files, but only
135 * invalidate the PCR for measured files:
136 * - Opening a file for write when already open for read,
137 * results in a time of measure, time of use (ToMToU) error.
138 * - Opening a file for read when already open for write,
139 * could result in a file measurement error.
142 void ima_counts_get(struct file *file)
144 struct dentry *dentry = file->f_path.dentry;
145 struct inode *inode = dentry->d_inode;
146 fmode_t mode = file->f_mode;
147 struct ima_iint_cache *iint;
150 if (!ima_initialized || !S_ISREG(inode->i_mode))
152 iint = ima_iint_find_get(inode);
155 mutex_lock(&iint->mutex);
156 rc = ima_must_measure(iint, inode, MAY_READ, FILE_CHECK);
160 if (mode & FMODE_WRITE) {
161 ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name);
164 ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name);
166 ima_inc_counts(iint, file->f_mode);
167 mutex_unlock(&iint->mutex);
169 kref_put(&iint->refcount, iint_free);
173 * Decrement ima counts
175 static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
178 mode_t mode = file->f_mode;
179 BUG_ON(!mutex_is_locked(&iint->mutex));
182 if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
184 if (mode & FMODE_WRITE) {
186 if (iint->writecount == 0) {
187 if (iint->version != inode->i_version)
188 iint->flags &= ~IMA_MEASURED;
192 if (((iint->opencount < 0) ||
193 (iint->readcount < 0) ||
194 (iint->writecount < 0)) &&
195 !ima_limit_imbalance(file)) {
196 printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld o:%ld)\n",
197 __FUNCTION__, iint->readcount, iint->writecount,
204 * ima_file_free - called on __fput()
205 * @file: pointer to file structure being freed
207 * Flag files that changed, based on i_version;
208 * and decrement the iint readcount/writecount.
210 void ima_file_free(struct file *file)
212 struct inode *inode = file->f_dentry->d_inode;
213 struct ima_iint_cache *iint;
215 if (!ima_initialized || !S_ISREG(inode->i_mode))
217 iint = ima_iint_find_get(inode);
221 mutex_lock(&iint->mutex);
222 ima_dec_counts(iint, inode, file);
223 mutex_unlock(&iint->mutex);
224 kref_put(&iint->refcount, iint_free);
227 static int process_measurement(struct file *file, const unsigned char *filename,
228 int mask, int function)
230 struct inode *inode = file->f_dentry->d_inode;
231 struct ima_iint_cache *iint;
234 if (!ima_initialized || !S_ISREG(inode->i_mode))
236 iint = ima_iint_find_get(inode);
240 mutex_lock(&iint->mutex);
241 rc = ima_must_measure(iint, inode, mask, function);
245 rc = ima_collect_measurement(iint, file);
247 ima_store_measurement(iint, file, filename);
249 mutex_unlock(&iint->mutex);
250 kref_put(&iint->refcount, iint_free);
255 * ima_file_mmap - based on policy, collect/store measurement.
256 * @file: pointer to the file to be measured (May be NULL)
257 * @prot: contains the protection that will be applied by the kernel.
259 * Measure files being mmapped executable based on the ima_must_measure()
262 * Return 0 on success, an error code on failure.
263 * (Based on the results of appraise_measurement().)
265 int ima_file_mmap(struct file *file, unsigned long prot)
271 if (prot & PROT_EXEC)
272 rc = process_measurement(file, file->f_dentry->d_name.name,
273 MAY_EXEC, FILE_MMAP);
278 * ima_bprm_check - based on policy, collect/store measurement.
279 * @bprm: contains the linux_binprm structure
281 * The OS protects against an executable file, already open for write,
282 * from being executed in deny_write_access() and an executable file,
283 * already open for execute, from being modified in get_write_access().
284 * So we can be certain that what we verify and measure here is actually
285 * what is being executed.
287 * Return 0 on success, an error code on failure.
288 * (Based on the results of appraise_measurement().)
290 int ima_bprm_check(struct linux_binprm *bprm)
294 rc = process_measurement(bprm->file, bprm->filename,
295 MAY_EXEC, BPRM_CHECK);
300 * ima_path_check - based on policy, collect/store measurement.
301 * @file: pointer to the file to be measured
302 * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
304 * Measure files based on the ima_must_measure() policy decision.
306 * Always return 0 and audit dentry_open failures.
307 * (Return code will be based upon measurement appraisal.)
309 int ima_file_check(struct file *file, int mask)
313 rc = process_measurement(file, file->f_dentry->d_name.name,
314 mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
318 EXPORT_SYMBOL_GPL(ima_file_check);
320 static int __init init_ima(void)
329 static void __exit cleanup_ima(void)
334 late_initcall(init_ima); /* Start IMA after the TPM is available */
336 MODULE_DESCRIPTION("Integrity Measurement Architecture");
337 MODULE_LICENSE("GPL");