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Linux/security/integrity/ima/ima_api.c

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  1 /*
  2  * Copyright (C) 2008 IBM Corporation
  3  *
  4  * Author: Mimi Zohar <zohar@us.ibm.com>
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public License as
  8  * published by the Free Software Foundation, version 2 of the
  9  * License.
 10  *
 11  * File: ima_api.c
 12  *      Implements must_appraise_or_measure, collect_measurement,
 13  *      appraise_measurement, store_measurement and store_template.
 14  */
 15 #include <linux/module.h>
 16 #include <linux/slab.h>
 17 #include <linux/file.h>
 18 #include <linux/fs.h>
 19 #include <linux/xattr.h>
 20 #include <linux/evm.h>
 21 #include <linux/iversion.h>
 22 
 23 #include "ima.h"
 24 
 25 /*
 26  * ima_free_template_entry - free an existing template entry
 27  */
 28 void ima_free_template_entry(struct ima_template_entry *entry)
 29 {
 30         int i;
 31 
 32         for (i = 0; i < entry->template_desc->num_fields; i++)
 33                 kfree(entry->template_data[i].data);
 34 
 35         kfree(entry);
 36 }
 37 
 38 /*
 39  * ima_alloc_init_template - create and initialize a new template entry
 40  */
 41 int ima_alloc_init_template(struct ima_event_data *event_data,
 42                             struct ima_template_entry **entry)
 43 {
 44         struct ima_template_desc *template_desc = ima_template_desc_current();
 45         int i, result = 0;
 46 
 47         *entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
 48                          sizeof(struct ima_field_data), GFP_NOFS);
 49         if (!*entry)
 50                 return -ENOMEM;
 51 
 52         (*entry)->template_desc = template_desc;
 53         for (i = 0; i < template_desc->num_fields; i++) {
 54                 struct ima_template_field *field = template_desc->fields[i];
 55                 u32 len;
 56 
 57                 result = field->field_init(event_data,
 58                                            &((*entry)->template_data[i]));
 59                 if (result != 0)
 60                         goto out;
 61 
 62                 len = (*entry)->template_data[i].len;
 63                 (*entry)->template_data_len += sizeof(len);
 64                 (*entry)->template_data_len += len;
 65         }
 66         return 0;
 67 out:
 68         ima_free_template_entry(*entry);
 69         *entry = NULL;
 70         return result;
 71 }
 72 
 73 /*
 74  * ima_store_template - store ima template measurements
 75  *
 76  * Calculate the hash of a template entry, add the template entry
 77  * to an ordered list of measurement entries maintained inside the kernel,
 78  * and also update the aggregate integrity value (maintained inside the
 79  * configured TPM PCR) over the hashes of the current list of measurement
 80  * entries.
 81  *
 82  * Applications retrieve the current kernel-held measurement list through
 83  * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
 84  * TPM PCR (called quote) can be retrieved using a TPM user space library
 85  * and is used to validate the measurement list.
 86  *
 87  * Returns 0 on success, error code otherwise
 88  */
 89 int ima_store_template(struct ima_template_entry *entry,
 90                        int violation, struct inode *inode,
 91                        const unsigned char *filename, int pcr)
 92 {
 93         static const char op[] = "add_template_measure";
 94         static const char audit_cause[] = "hashing_error";
 95         char *template_name = entry->template_desc->name;
 96         int result;
 97         struct {
 98                 struct ima_digest_data hdr;
 99                 char digest[TPM_DIGEST_SIZE];
100         } hash;
101 
102         if (!violation) {
103                 int num_fields = entry->template_desc->num_fields;
104 
105                 /* this function uses default algo */
106                 hash.hdr.algo = HASH_ALGO_SHA1;
107                 result = ima_calc_field_array_hash(&entry->template_data[0],
108                                                    entry->template_desc,
109                                                    num_fields, &hash.hdr);
110                 if (result < 0) {
111                         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
112                                             template_name, op,
113                                             audit_cause, result, 0);
114                         return result;
115                 }
116                 memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
117         }
118         entry->pcr = pcr;
119         result = ima_add_template_entry(entry, violation, op, inode, filename);
120         return result;
121 }
122 
123 /*
124  * ima_add_violation - add violation to measurement list.
125  *
126  * Violations are flagged in the measurement list with zero hash values.
127  * By extending the PCR with 0xFF's instead of with zeroes, the PCR
128  * value is invalidated.
129  */
130 void ima_add_violation(struct file *file, const unsigned char *filename,
131                        struct integrity_iint_cache *iint,
132                        const char *op, const char *cause)
133 {
134         struct ima_template_entry *entry;
135         struct inode *inode = file_inode(file);
136         struct ima_event_data event_data = {iint, file, filename, NULL, 0,
137                                             cause};
138         int violation = 1;
139         int result;
140 
141         /* can overflow, only indicator */
142         atomic_long_inc(&ima_htable.violations);
143 
144         result = ima_alloc_init_template(&event_data, &entry);
145         if (result < 0) {
146                 result = -ENOMEM;
147                 goto err_out;
148         }
149         result = ima_store_template(entry, violation, inode,
150                                     filename, CONFIG_IMA_MEASURE_PCR_IDX);
151         if (result < 0)
152                 ima_free_template_entry(entry);
153 err_out:
154         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
155                             op, cause, result, 0);
156 }
157 
158 /**
159  * ima_get_action - appraise & measure decision based on policy.
160  * @inode: pointer to inode to measure
161  * @cred: pointer to credentials structure to validate
162  * @secid: secid of the task being validated
163  * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
164  *        MAY_APPEND)
165  * @func: caller identifier
166  * @pcr: pointer filled in if matched measure policy sets pcr=
167  *
168  * The policy is defined in terms of keypairs:
169  *              subj=, obj=, type=, func=, mask=, fsmagic=
170  *      subj,obj, and type: are LSM specific.
171  *      func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
172  *      mask: contains the permission mask
173  *      fsmagic: hex value
174  *
175  * Returns IMA_MEASURE, IMA_APPRAISE mask.
176  *
177  */
178 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
179                    int mask, enum ima_hooks func, int *pcr)
180 {
181         int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
182 
183         flags &= ima_policy_flag;
184 
185         return ima_match_policy(inode, cred, secid, func, mask, flags, pcr);
186 }
187 
188 /*
189  * ima_collect_measurement - collect file measurement
190  *
191  * Calculate the file hash, if it doesn't already exist,
192  * storing the measurement and i_version in the iint.
193  *
194  * Must be called with iint->mutex held.
195  *
196  * Return 0 on success, error code otherwise
197  */
198 int ima_collect_measurement(struct integrity_iint_cache *iint,
199                             struct file *file, void *buf, loff_t size,
200                             enum hash_algo algo)
201 {
202         const char *audit_cause = "failed";
203         struct inode *inode = file_inode(file);
204         const char *filename = file->f_path.dentry->d_name.name;
205         int result = 0;
206         int length;
207         void *tmpbuf;
208         u64 i_version;
209         struct {
210                 struct ima_digest_data hdr;
211                 char digest[IMA_MAX_DIGEST_SIZE];
212         } hash;
213 
214         if (iint->flags & IMA_COLLECTED)
215                 goto out;
216 
217         /*
218          * Dectecting file change is based on i_version. On filesystems
219          * which do not support i_version, support is limited to an initial
220          * measurement/appraisal/audit.
221          */
222         i_version = inode_query_iversion(inode);
223         hash.hdr.algo = algo;
224 
225         /* Initialize hash digest to 0's in case of failure */
226         memset(&hash.digest, 0, sizeof(hash.digest));
227 
228         if (buf)
229                 result = ima_calc_buffer_hash(buf, size, &hash.hdr);
230         else
231                 result = ima_calc_file_hash(file, &hash.hdr);
232 
233         if (result && result != -EBADF && result != -EINVAL)
234                 goto out;
235 
236         length = sizeof(hash.hdr) + hash.hdr.length;
237         tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
238         if (!tmpbuf) {
239                 result = -ENOMEM;
240                 goto out;
241         }
242 
243         iint->ima_hash = tmpbuf;
244         memcpy(iint->ima_hash, &hash, length);
245         iint->version = i_version;
246 
247         /* Possibly temporary failure due to type of read (eg. O_DIRECT) */
248         if (!result)
249                 iint->flags |= IMA_COLLECTED;
250 out:
251         if (result) {
252                 if (file->f_flags & O_DIRECT)
253                         audit_cause = "failed(directio)";
254 
255                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
256                                     filename, "collect_data", audit_cause,
257                                     result, 0);
258         }
259         return result;
260 }
261 
262 /*
263  * ima_store_measurement - store file measurement
264  *
265  * Create an "ima" template and then store the template by calling
266  * ima_store_template.
267  *
268  * We only get here if the inode has not already been measured,
269  * but the measurement could already exist:
270  *      - multiple copies of the same file on either the same or
271  *        different filesystems.
272  *      - the inode was previously flushed as well as the iint info,
273  *        containing the hashing info.
274  *
275  * Must be called with iint->mutex held.
276  */
277 void ima_store_measurement(struct integrity_iint_cache *iint,
278                            struct file *file, const unsigned char *filename,
279                            struct evm_ima_xattr_data *xattr_value,
280                            int xattr_len, int pcr)
281 {
282         static const char op[] = "add_template_measure";
283         static const char audit_cause[] = "ENOMEM";
284         int result = -ENOMEM;
285         struct inode *inode = file_inode(file);
286         struct ima_template_entry *entry;
287         struct ima_event_data event_data = {iint, file, filename, xattr_value,
288                                             xattr_len, NULL};
289         int violation = 0;
290 
291         if (iint->measured_pcrs & (0x1 << pcr))
292                 return;
293 
294         result = ima_alloc_init_template(&event_data, &entry);
295         if (result < 0) {
296                 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
297                                     op, audit_cause, result, 0);
298                 return;
299         }
300 
301         result = ima_store_template(entry, violation, inode, filename, pcr);
302         if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
303                 iint->flags |= IMA_MEASURED;
304                 iint->measured_pcrs |= (0x1 << pcr);
305         }
306         if (result < 0)
307                 ima_free_template_entry(entry);
308 }
309 
310 void ima_audit_measurement(struct integrity_iint_cache *iint,
311                            const unsigned char *filename)
312 {
313         struct audit_buffer *ab;
314         char *hash;
315         const char *algo_name = hash_algo_name[iint->ima_hash->algo];
316         int i;
317 
318         if (iint->flags & IMA_AUDITED)
319                 return;
320 
321         hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
322         if (!hash)
323                 return;
324 
325         for (i = 0; i < iint->ima_hash->length; i++)
326                 hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
327         hash[i * 2] = '\0';
328 
329         ab = audit_log_start(audit_context(), GFP_KERNEL,
330                              AUDIT_INTEGRITY_RULE);
331         if (!ab)
332                 goto out;
333 
334         audit_log_format(ab, "file=");
335         audit_log_untrustedstring(ab, filename);
336         audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);
337 
338         audit_log_task_info(ab, current);
339         audit_log_end(ab);
340 
341         iint->flags |= IMA_AUDITED;
342 out:
343         kfree(hash);
344         return;
345 }
346 
347 /*
348  * ima_d_path - return a pointer to the full pathname
349  *
350  * Attempt to return a pointer to the full pathname for use in the
351  * IMA measurement list, IMA audit records, and auditing logs.
352  *
353  * On failure, return a pointer to a copy of the filename, not dname.
354  * Returning a pointer to dname, could result in using the pointer
355  * after the memory has been freed.
356  */
357 const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
358 {
359         char *pathname = NULL;
360 
361         *pathbuf = __getname();
362         if (*pathbuf) {
363                 pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
364                 if (IS_ERR(pathname)) {
365                         __putname(*pathbuf);
366                         *pathbuf = NULL;
367                         pathname = NULL;
368                 }
369         }
370 
371         if (!pathname) {
372                 strlcpy(namebuf, path->dentry->d_name.name, NAME_MAX);
373                 pathname = namebuf;
374         }
375 
376         return pathname;
377 }
378 

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