linux/security/integrity/ima/ima_fs.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
   4 *
   5 * Authors:
   6 * Kylene Hall <kjhall@us.ibm.com>
   7 * Reiner Sailer <sailer@us.ibm.com>
   8 * Mimi Zohar <zohar@us.ibm.com>
   9 *
  10 * File: ima_fs.c
  11 *      implemenents security file system for reporting
  12 *      current measurement list and IMA statistics
  13 */
  14
  15#include <linux/fcntl.h>
  16#include <linux/kernel_read_file.h>
  17#include <linux/slab.h>
  18#include <linux/init.h>
  19#include <linux/seq_file.h>
  20#include <linux/rculist.h>
  21#include <linux/rcupdate.h>
  22#include <linux/parser.h>
  23#include <linux/vmalloc.h>
  24
  25#include "ima.h"
  26
  27static DEFINE_MUTEX(ima_write_mutex);
  28
  29bool ima_canonical_fmt;
  30static int __init default_canonical_fmt_setup(char *str)
  31{
  32#ifdef __BIG_ENDIAN
  33        ima_canonical_fmt = true;
  34#endif
  35        return 1;
  36}
  37__setup("ima_canonical_fmt", default_canonical_fmt_setup);
  38
  39static int valid_policy = 1;
  40
  41static ssize_t ima_show_htable_value(char __user *buf, size_t count,
  42                                     loff_t *ppos, atomic_long_t *val)
  43{
  44        char tmpbuf[32];        /* greater than largest 'long' string value */
  45        ssize_t len;
  46
  47        len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
  48        return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
  49}
  50
  51static ssize_t ima_show_htable_violations(struct file *filp,
  52                                          char __user *buf,
  53                                          size_t count, loff_t *ppos)
  54{
  55        return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
  56}
  57
  58static const struct file_operations ima_htable_violations_ops = {
  59        .read = ima_show_htable_violations,
  60        .llseek = generic_file_llseek,
  61};
  62
  63static ssize_t ima_show_measurements_count(struct file *filp,
  64                                           char __user *buf,
  65                                           size_t count, loff_t *ppos)
  66{
  67        return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
  68
  69}
  70
  71static const struct file_operations ima_measurements_count_ops = {
  72        .read = ima_show_measurements_count,
  73        .llseek = generic_file_llseek,
  74};
  75
  76/* returns pointer to hlist_node */
  77static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
  78{
  79        loff_t l = *pos;
  80        struct ima_queue_entry *qe;
  81
  82        /* we need a lock since pos could point beyond last element */
  83        rcu_read_lock();
  84        list_for_each_entry_rcu(qe, &ima_measurements, later) {
  85                if (!l--) {
  86                        rcu_read_unlock();
  87                        return qe;
  88                }
  89        }
  90        rcu_read_unlock();
  91        return NULL;
  92}
  93
  94static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
  95{
  96        struct ima_queue_entry *qe = v;
  97
  98        /* lock protects when reading beyond last element
  99         * against concurrent list-extension
 100         */
 101        rcu_read_lock();
 102        qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
 103        rcu_read_unlock();
 104        (*pos)++;
 105
 106        return (&qe->later == &ima_measurements) ? NULL : qe;
 107}
 108
 109static void ima_measurements_stop(struct seq_file *m, void *v)
 110{
 111}
 112
 113void ima_putc(struct seq_file *m, void *data, int datalen)
 114{
 115        while (datalen--)
 116                seq_putc(m, *(char *)data++);
 117}
 118
 119/* print format:
 120 *       32bit-le=pcr#
 121 *       char[20]=template digest
 122 *       32bit-le=template name size
 123 *       char[n]=template name
 124 *       [eventdata length]
 125 *       eventdata[n]=template specific data
 126 */
 127int ima_measurements_show(struct seq_file *m, void *v)
 128{
 129        /* the list never shrinks, so we don't need a lock here */
 130        struct ima_queue_entry *qe = v;
 131        struct ima_template_entry *e;
 132        char *template_name;
 133        u32 pcr, namelen, template_data_len; /* temporary fields */
 134        bool is_ima_template = false;
 135        int i;
 136
 137        /* get entry */
 138        e = qe->entry;
 139        if (e == NULL)
 140                return -1;
 141
 142        template_name = (e->template_desc->name[0] != '\0') ?
 143            e->template_desc->name : e->template_desc->fmt;
 144
 145        /*
 146         * 1st: PCRIndex
 147         * PCR used defaults to the same (config option) in
 148         * little-endian format, unless set in policy
 149         */
 150        pcr = !ima_canonical_fmt ? e->pcr : (__force u32)cpu_to_le32(e->pcr);
 151        ima_putc(m, &pcr, sizeof(e->pcr));
 152
 153        /* 2nd: template digest */
 154        ima_putc(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
 155
 156        /* 3rd: template name size */
 157        namelen = !ima_canonical_fmt ? strlen(template_name) :
 158                (__force u32)cpu_to_le32(strlen(template_name));
 159        ima_putc(m, &namelen, sizeof(namelen));
 160
 161        /* 4th:  template name */
 162        ima_putc(m, template_name, strlen(template_name));
 163
 164        /* 5th:  template length (except for 'ima' template) */
 165        if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
 166                is_ima_template = true;
 167
 168        if (!is_ima_template) {
 169                template_data_len = !ima_canonical_fmt ? e->template_data_len :
 170                        (__force u32)cpu_to_le32(e->template_data_len);
 171                ima_putc(m, &template_data_len, sizeof(e->template_data_len));
 172        }
 173
 174        /* 6th:  template specific data */
 175        for (i = 0; i < e->template_desc->num_fields; i++) {
 176                enum ima_show_type show = IMA_SHOW_BINARY;
 177                const struct ima_template_field *field =
 178                        e->template_desc->fields[i];
 179
 180                if (is_ima_template && strcmp(field->field_id, "d") == 0)
 181                        show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 182                if (is_ima_template && strcmp(field->field_id, "n") == 0)
 183                        show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 184                field->field_show(m, show, &e->template_data[i]);
 185        }
 186        return 0;
 187}
 188
 189static const struct seq_operations ima_measurments_seqops = {
 190        .start = ima_measurements_start,
 191        .next = ima_measurements_next,
 192        .stop = ima_measurements_stop,
 193        .show = ima_measurements_show
 194};
 195
 196static int ima_measurements_open(struct inode *inode, struct file *file)
 197{
 198        return seq_open(file, &ima_measurments_seqops);
 199}
 200
 201static const struct file_operations ima_measurements_ops = {
 202        .open = ima_measurements_open,
 203        .read = seq_read,
 204        .llseek = seq_lseek,
 205        .release = seq_release,
 206};
 207
 208void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
 209{
 210        u32 i;
 211
 212        for (i = 0; i < size; i++)
 213                seq_printf(m, "%02x", *(digest + i));
 214}
 215
 216/* print in ascii */
 217static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 218{
 219        /* the list never shrinks, so we don't need a lock here */
 220        struct ima_queue_entry *qe = v;
 221        struct ima_template_entry *e;
 222        char *template_name;
 223        int i;
 224
 225        /* get entry */
 226        e = qe->entry;
 227        if (e == NULL)
 228                return -1;
 229
 230        template_name = (e->template_desc->name[0] != '\0') ?
 231            e->template_desc->name : e->template_desc->fmt;
 232
 233        /* 1st: PCR used (config option) */
 234        seq_printf(m, "%2d ", e->pcr);
 235
 236        /* 2nd: SHA1 template hash */
 237        ima_print_digest(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
 238
 239        /* 3th:  template name */
 240        seq_printf(m, " %s", template_name);
 241
 242        /* 4th:  template specific data */
 243        for (i = 0; i < e->template_desc->num_fields; i++) {
 244                seq_puts(m, " ");
 245                if (e->template_data[i].len == 0)
 246                        continue;
 247
 248                e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 249                                                        &e->template_data[i]);
 250        }
 251        seq_puts(m, "\n");
 252        return 0;
 253}
 254
 255static const struct seq_operations ima_ascii_measurements_seqops = {
 256        .start = ima_measurements_start,
 257        .next = ima_measurements_next,
 258        .stop = ima_measurements_stop,
 259        .show = ima_ascii_measurements_show
 260};
 261
 262static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 263{
 264        return seq_open(file, &ima_ascii_measurements_seqops);
 265}
 266
 267static const struct file_operations ima_ascii_measurements_ops = {
 268        .open = ima_ascii_measurements_open,
 269        .read = seq_read,
 270        .llseek = seq_lseek,
 271        .release = seq_release,
 272};
 273
 274static ssize_t ima_read_policy(char *path)
 275{
 276        void *data = NULL;
 277        char *datap;
 278        size_t size;
 279        int rc, pathlen = strlen(path);
 280
 281        char *p;
 282
 283        /* remove \n */
 284        datap = path;
 285        strsep(&datap, "\n");
 286
 287        rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
 288                                        READING_POLICY);
 289        if (rc < 0) {
 290                pr_err("Unable to open file: %s (%d)", path, rc);
 291                return rc;
 292        }
 293        size = rc;
 294        rc = 0;
 295
 296        datap = data;
 297        while (size > 0 && (p = strsep(&datap, "\n"))) {
 298                pr_debug("rule: %s\n", p);
 299                rc = ima_parse_add_rule(p);
 300                if (rc < 0)
 301                        break;
 302                size -= rc;
 303        }
 304
 305        vfree(data);
 306        if (rc < 0)
 307                return rc;
 308        else if (size)
 309                return -EINVAL;
 310        else
 311                return pathlen;
 312}
 313
 314static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 315                                size_t datalen, loff_t *ppos)
 316{
 317        char *data;
 318        ssize_t result;
 319
 320        if (datalen >= PAGE_SIZE)
 321                datalen = PAGE_SIZE - 1;
 322
 323        /* No partial writes. */
 324        result = -EINVAL;
 325        if (*ppos != 0)
 326                goto out;
 327
 328        data = memdup_user_nul(buf, datalen);
 329        if (IS_ERR(data)) {
 330                result = PTR_ERR(data);
 331                goto out;
 332        }
 333
 334        result = mutex_lock_interruptible(&ima_write_mutex);
 335        if (result < 0)
 336                goto out_free;
 337
 338        if (data[0] == '/') {
 339                result = ima_read_policy(data);
 340        } else if (ima_appraise & IMA_APPRAISE_POLICY) {
 341                pr_err("signed policy file (specified as an absolute pathname) required\n");
 342                integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 343                                    "policy_update", "signed policy required",
 344                                    1, 0);
 345                result = -EACCES;
 346        } else {
 347                result = ima_parse_add_rule(data);
 348        }
 349        mutex_unlock(&ima_write_mutex);
 350out_free:
 351        kfree(data);
 352out:
 353        if (result < 0)
 354                valid_policy = 0;
 355
 356        return result;
 357}
 358
 359static struct dentry *ima_dir;
 360static struct dentry *ima_symlink;
 361static struct dentry *binary_runtime_measurements;
 362static struct dentry *ascii_runtime_measurements;
 363static struct dentry *runtime_measurements_count;
 364static struct dentry *violations;
 365static struct dentry *ima_policy;
 366
 367enum ima_fs_flags {
 368        IMA_FS_BUSY,
 369};
 370
 371static unsigned long ima_fs_flags;
 372
 373#ifdef  CONFIG_IMA_READ_POLICY
 374static const struct seq_operations ima_policy_seqops = {
 375                .start = ima_policy_start,
 376                .next = ima_policy_next,
 377                .stop = ima_policy_stop,
 378                .show = ima_policy_show,
 379};
 380#endif
 381
 382/*
 383 * ima_open_policy: sequentialize access to the policy file
 384 */
 385static int ima_open_policy(struct inode *inode, struct file *filp)
 386{
 387        if (!(filp->f_flags & O_WRONLY)) {
 388#ifndef CONFIG_IMA_READ_POLICY
 389                return -EACCES;
 390#else
 391                if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 392                        return -EACCES;
 393                if (!capable(CAP_SYS_ADMIN))
 394                        return -EPERM;
 395                return seq_open(filp, &ima_policy_seqops);
 396#endif
 397        }
 398        if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 399                return -EBUSY;
 400        return 0;
 401}
 402
 403/*
 404 * ima_release_policy - start using the new measure policy rules.
 405 *
 406 * Initially, ima_measure points to the default policy rules, now
 407 * point to the new policy rules, and remove the securityfs policy file,
 408 * assuming a valid policy.
 409 */
 410static int ima_release_policy(struct inode *inode, struct file *file)
 411{
 412        const char *cause = valid_policy ? "completed" : "failed";
 413
 414        if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 415                return seq_release(inode, file);
 416
 417        if (valid_policy && ima_check_policy() < 0) {
 418                cause = "failed";
 419                valid_policy = 0;
 420        }
 421
 422        pr_info("policy update %s\n", cause);
 423        integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 424                            "policy_update", cause, !valid_policy, 0);
 425
 426        if (!valid_policy) {
 427                ima_delete_rules();
 428                valid_policy = 1;
 429                clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 430                return 0;
 431        }
 432
 433        ima_update_policy();
 434#if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
 435        securityfs_remove(ima_policy);
 436        ima_policy = NULL;
 437#elif defined(CONFIG_IMA_WRITE_POLICY)
 438        clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 439#elif defined(CONFIG_IMA_READ_POLICY)
 440        inode->i_mode &= ~S_IWUSR;
 441#endif
 442        return 0;
 443}
 444
 445static const struct file_operations ima_measure_policy_ops = {
 446        .open = ima_open_policy,
 447        .write = ima_write_policy,
 448        .read = seq_read,
 449        .release = ima_release_policy,
 450        .llseek = generic_file_llseek,
 451};
 452
 453int __init ima_fs_init(void)
 454{
 455        ima_dir = securityfs_create_dir("ima", integrity_dir);
 456        if (IS_ERR(ima_dir))
 457                return -1;
 458
 459        ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
 460                                                NULL);
 461        if (IS_ERR(ima_symlink))
 462                goto out;
 463
 464        binary_runtime_measurements =
 465            securityfs_create_file("binary_runtime_measurements",
 466                                   S_IRUSR | S_IRGRP, ima_dir, NULL,
 467                                   &ima_measurements_ops);
 468        if (IS_ERR(binary_runtime_measurements))
 469                goto out;
 470
 471        ascii_runtime_measurements =
 472            securityfs_create_file("ascii_runtime_measurements",
 473                                   S_IRUSR | S_IRGRP, ima_dir, NULL,
 474                                   &ima_ascii_measurements_ops);
 475        if (IS_ERR(ascii_runtime_measurements))
 476                goto out;
 477
 478        runtime_measurements_count =
 479            securityfs_create_file("runtime_measurements_count",
 480                                   S_IRUSR | S_IRGRP, ima_dir, NULL,
 481                                   &ima_measurements_count_ops);
 482        if (IS_ERR(runtime_measurements_count))
 483                goto out;
 484
 485        violations =
 486            securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 487                                   ima_dir, NULL, &ima_htable_violations_ops);
 488        if (IS_ERR(violations))
 489                goto out;
 490
 491        ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
 492                                            ima_dir, NULL,
 493                                            &ima_measure_policy_ops);
 494        if (IS_ERR(ima_policy))
 495                goto out;
 496
 497        return 0;
 498out:
 499        securityfs_remove(ima_policy);
 500        securityfs_remove(violations);
 501        securityfs_remove(runtime_measurements_count);
 502        securityfs_remove(ascii_runtime_measurements);
 503        securityfs_remove(binary_runtime_measurements);
 504        securityfs_remove(ima_symlink);
 505        securityfs_remove(ima_dir);
 506        return -1;
 507}
 508