![Kees Cook](/assets/img/avatar_default.png)
To perform partial reads, callers of kernel_read_file*() must have a non-NULL file_size argument and a preallocated buffer. The new "offset" argument can then be used to seek to specific locations in the file to fill the buffer to, at most, "buf_size" per call. Where possible, the LSM hooks can report whether a full file has been read or not so that the contents can be reasoned about. Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20201002173828.2099543-14-keescook@chromium.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
508 lines
12 KiB
C
508 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2005,2006,2007,2008 IBM Corporation
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*
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* Authors:
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* Kylene Hall <kjhall@us.ibm.com>
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* Reiner Sailer <sailer@us.ibm.com>
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* Mimi Zohar <zohar@us.ibm.com>
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*
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* File: ima_fs.c
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* implemenents security file system for reporting
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* current measurement list and IMA statistics
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*/
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#include <linux/fcntl.h>
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#include <linux/kernel_read_file.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/seq_file.h>
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#include <linux/rculist.h>
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#include <linux/rcupdate.h>
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#include <linux/parser.h>
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#include <linux/vmalloc.h>
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#include "ima.h"
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static DEFINE_MUTEX(ima_write_mutex);
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bool ima_canonical_fmt;
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static int __init default_canonical_fmt_setup(char *str)
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{
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#ifdef __BIG_ENDIAN
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ima_canonical_fmt = true;
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#endif
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return 1;
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}
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__setup("ima_canonical_fmt", default_canonical_fmt_setup);
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static int valid_policy = 1;
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static ssize_t ima_show_htable_value(char __user *buf, size_t count,
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loff_t *ppos, atomic_long_t *val)
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{
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char tmpbuf[32]; /* greater than largest 'long' string value */
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ssize_t len;
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len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
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return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
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}
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static ssize_t ima_show_htable_violations(struct file *filp,
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char __user *buf,
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size_t count, loff_t *ppos)
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{
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return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
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}
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static const struct file_operations ima_htable_violations_ops = {
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.read = ima_show_htable_violations,
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.llseek = generic_file_llseek,
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};
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static ssize_t ima_show_measurements_count(struct file *filp,
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char __user *buf,
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size_t count, loff_t *ppos)
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{
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return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
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}
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static const struct file_operations ima_measurements_count_ops = {
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.read = ima_show_measurements_count,
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.llseek = generic_file_llseek,
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};
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/* returns pointer to hlist_node */
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static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
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{
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loff_t l = *pos;
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struct ima_queue_entry *qe;
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/* we need a lock since pos could point beyond last element */
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rcu_read_lock();
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list_for_each_entry_rcu(qe, &ima_measurements, later) {
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if (!l--) {
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rcu_read_unlock();
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return qe;
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}
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}
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rcu_read_unlock();
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return NULL;
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}
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static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
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{
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struct ima_queue_entry *qe = v;
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/* lock protects when reading beyond last element
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* against concurrent list-extension
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*/
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rcu_read_lock();
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qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
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rcu_read_unlock();
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(*pos)++;
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return (&qe->later == &ima_measurements) ? NULL : qe;
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}
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static void ima_measurements_stop(struct seq_file *m, void *v)
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{
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}
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void ima_putc(struct seq_file *m, void *data, int datalen)
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{
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while (datalen--)
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seq_putc(m, *(char *)data++);
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}
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/* print format:
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* 32bit-le=pcr#
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* char[20]=template digest
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* 32bit-le=template name size
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* char[n]=template name
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* [eventdata length]
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* eventdata[n]=template specific data
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*/
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int ima_measurements_show(struct seq_file *m, void *v)
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{
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/* the list never shrinks, so we don't need a lock here */
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struct ima_queue_entry *qe = v;
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struct ima_template_entry *e;
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char *template_name;
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u32 pcr, namelen, template_data_len; /* temporary fields */
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bool is_ima_template = false;
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int i;
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/* get entry */
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e = qe->entry;
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if (e == NULL)
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return -1;
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template_name = (e->template_desc->name[0] != '\0') ?
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e->template_desc->name : e->template_desc->fmt;
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/*
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* 1st: PCRIndex
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* PCR used defaults to the same (config option) in
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* little-endian format, unless set in policy
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*/
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pcr = !ima_canonical_fmt ? e->pcr : cpu_to_le32(e->pcr);
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ima_putc(m, &pcr, sizeof(e->pcr));
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/* 2nd: template digest */
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ima_putc(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
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/* 3rd: template name size */
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namelen = !ima_canonical_fmt ? strlen(template_name) :
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cpu_to_le32(strlen(template_name));
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ima_putc(m, &namelen, sizeof(namelen));
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/* 4th: template name */
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ima_putc(m, template_name, strlen(template_name));
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/* 5th: template length (except for 'ima' template) */
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if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
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is_ima_template = true;
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if (!is_ima_template) {
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template_data_len = !ima_canonical_fmt ? e->template_data_len :
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cpu_to_le32(e->template_data_len);
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ima_putc(m, &template_data_len, sizeof(e->template_data_len));
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}
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/* 6th: template specific data */
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for (i = 0; i < e->template_desc->num_fields; i++) {
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enum ima_show_type show = IMA_SHOW_BINARY;
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const struct ima_template_field *field =
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e->template_desc->fields[i];
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if (is_ima_template && strcmp(field->field_id, "d") == 0)
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show = IMA_SHOW_BINARY_NO_FIELD_LEN;
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if (is_ima_template && strcmp(field->field_id, "n") == 0)
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show = IMA_SHOW_BINARY_OLD_STRING_FMT;
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field->field_show(m, show, &e->template_data[i]);
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}
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return 0;
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}
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static const struct seq_operations ima_measurments_seqops = {
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.start = ima_measurements_start,
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.next = ima_measurements_next,
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.stop = ima_measurements_stop,
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.show = ima_measurements_show
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};
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static int ima_measurements_open(struct inode *inode, struct file *file)
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{
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return seq_open(file, &ima_measurments_seqops);
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}
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static const struct file_operations ima_measurements_ops = {
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.open = ima_measurements_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
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{
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u32 i;
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for (i = 0; i < size; i++)
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seq_printf(m, "%02x", *(digest + i));
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}
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/* print in ascii */
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static int ima_ascii_measurements_show(struct seq_file *m, void *v)
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{
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/* the list never shrinks, so we don't need a lock here */
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struct ima_queue_entry *qe = v;
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struct ima_template_entry *e;
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char *template_name;
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int i;
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/* get entry */
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e = qe->entry;
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if (e == NULL)
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return -1;
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template_name = (e->template_desc->name[0] != '\0') ?
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e->template_desc->name : e->template_desc->fmt;
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/* 1st: PCR used (config option) */
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seq_printf(m, "%2d ", e->pcr);
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/* 2nd: SHA1 template hash */
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ima_print_digest(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
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/* 3th: template name */
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seq_printf(m, " %s", template_name);
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/* 4th: template specific data */
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for (i = 0; i < e->template_desc->num_fields; i++) {
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seq_puts(m, " ");
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if (e->template_data[i].len == 0)
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continue;
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e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
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&e->template_data[i]);
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}
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seq_puts(m, "\n");
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return 0;
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}
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static const struct seq_operations ima_ascii_measurements_seqops = {
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.start = ima_measurements_start,
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.next = ima_measurements_next,
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.stop = ima_measurements_stop,
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.show = ima_ascii_measurements_show
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};
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static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
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{
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return seq_open(file, &ima_ascii_measurements_seqops);
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}
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static const struct file_operations ima_ascii_measurements_ops = {
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.open = ima_ascii_measurements_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = seq_release,
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};
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static ssize_t ima_read_policy(char *path)
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{
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void *data = NULL;
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char *datap;
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size_t size;
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int rc, pathlen = strlen(path);
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char *p;
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/* remove \n */
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datap = path;
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strsep(&datap, "\n");
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rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
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READING_POLICY);
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if (rc < 0) {
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pr_err("Unable to open file: %s (%d)", path, rc);
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return rc;
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}
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size = rc;
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rc = 0;
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datap = data;
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while (size > 0 && (p = strsep(&datap, "\n"))) {
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pr_debug("rule: %s\n", p);
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rc = ima_parse_add_rule(p);
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if (rc < 0)
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break;
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size -= rc;
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}
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vfree(data);
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if (rc < 0)
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return rc;
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else if (size)
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return -EINVAL;
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else
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return pathlen;
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}
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static ssize_t ima_write_policy(struct file *file, const char __user *buf,
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size_t datalen, loff_t *ppos)
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{
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char *data;
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ssize_t result;
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if (datalen >= PAGE_SIZE)
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datalen = PAGE_SIZE - 1;
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/* No partial writes. */
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result = -EINVAL;
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if (*ppos != 0)
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goto out;
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data = memdup_user_nul(buf, datalen);
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if (IS_ERR(data)) {
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result = PTR_ERR(data);
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goto out;
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}
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result = mutex_lock_interruptible(&ima_write_mutex);
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if (result < 0)
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goto out_free;
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if (data[0] == '/') {
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result = ima_read_policy(data);
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} else if (ima_appraise & IMA_APPRAISE_POLICY) {
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pr_err("signed policy file (specified as an absolute pathname) required\n");
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integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
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"policy_update", "signed policy required",
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1, 0);
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result = -EACCES;
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} else {
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result = ima_parse_add_rule(data);
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}
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mutex_unlock(&ima_write_mutex);
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out_free:
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kfree(data);
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out:
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if (result < 0)
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valid_policy = 0;
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return result;
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}
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static struct dentry *ima_dir;
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static struct dentry *ima_symlink;
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static struct dentry *binary_runtime_measurements;
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static struct dentry *ascii_runtime_measurements;
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static struct dentry *runtime_measurements_count;
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static struct dentry *violations;
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static struct dentry *ima_policy;
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enum ima_fs_flags {
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IMA_FS_BUSY,
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};
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static unsigned long ima_fs_flags;
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#ifdef CONFIG_IMA_READ_POLICY
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static const struct seq_operations ima_policy_seqops = {
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.start = ima_policy_start,
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.next = ima_policy_next,
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.stop = ima_policy_stop,
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.show = ima_policy_show,
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};
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#endif
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/*
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* ima_open_policy: sequentialize access to the policy file
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*/
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static int ima_open_policy(struct inode *inode, struct file *filp)
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{
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if (!(filp->f_flags & O_WRONLY)) {
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#ifndef CONFIG_IMA_READ_POLICY
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return -EACCES;
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#else
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if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
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return -EACCES;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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return seq_open(filp, &ima_policy_seqops);
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#endif
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}
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if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
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return -EBUSY;
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return 0;
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}
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/*
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* ima_release_policy - start using the new measure policy rules.
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*
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* Initially, ima_measure points to the default policy rules, now
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* point to the new policy rules, and remove the securityfs policy file,
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* assuming a valid policy.
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*/
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static int ima_release_policy(struct inode *inode, struct file *file)
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{
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const char *cause = valid_policy ? "completed" : "failed";
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if ((file->f_flags & O_ACCMODE) == O_RDONLY)
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return seq_release(inode, file);
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if (valid_policy && ima_check_policy() < 0) {
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cause = "failed";
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valid_policy = 0;
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}
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pr_info("policy update %s\n", cause);
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integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
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"policy_update", cause, !valid_policy, 0);
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if (!valid_policy) {
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ima_delete_rules();
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valid_policy = 1;
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clear_bit(IMA_FS_BUSY, &ima_fs_flags);
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return 0;
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}
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ima_update_policy();
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#if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
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securityfs_remove(ima_policy);
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ima_policy = NULL;
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#elif defined(CONFIG_IMA_WRITE_POLICY)
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clear_bit(IMA_FS_BUSY, &ima_fs_flags);
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#elif defined(CONFIG_IMA_READ_POLICY)
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inode->i_mode &= ~S_IWUSR;
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#endif
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return 0;
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}
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static const struct file_operations ima_measure_policy_ops = {
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.open = ima_open_policy,
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.write = ima_write_policy,
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.read = seq_read,
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.release = ima_release_policy,
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.llseek = generic_file_llseek,
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};
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int __init ima_fs_init(void)
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{
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ima_dir = securityfs_create_dir("ima", integrity_dir);
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if (IS_ERR(ima_dir))
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return -1;
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ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
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NULL);
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if (IS_ERR(ima_symlink))
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goto out;
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binary_runtime_measurements =
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securityfs_create_file("binary_runtime_measurements",
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S_IRUSR | S_IRGRP, ima_dir, NULL,
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&ima_measurements_ops);
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if (IS_ERR(binary_runtime_measurements))
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goto out;
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ascii_runtime_measurements =
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securityfs_create_file("ascii_runtime_measurements",
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S_IRUSR | S_IRGRP, ima_dir, NULL,
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&ima_ascii_measurements_ops);
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if (IS_ERR(ascii_runtime_measurements))
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goto out;
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runtime_measurements_count =
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securityfs_create_file("runtime_measurements_count",
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S_IRUSR | S_IRGRP, ima_dir, NULL,
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&ima_measurements_count_ops);
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if (IS_ERR(runtime_measurements_count))
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goto out;
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violations =
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securityfs_create_file("violations", S_IRUSR | S_IRGRP,
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ima_dir, NULL, &ima_htable_violations_ops);
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if (IS_ERR(violations))
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goto out;
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ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
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ima_dir, NULL,
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&ima_measure_policy_ops);
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if (IS_ERR(ima_policy))
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goto out;
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return 0;
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out:
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securityfs_remove(violations);
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securityfs_remove(runtime_measurements_count);
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securityfs_remove(ascii_runtime_measurements);
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securityfs_remove(binary_runtime_measurements);
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securityfs_remove(ima_symlink);
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securityfs_remove(ima_dir);
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securityfs_remove(ima_policy);
|
|
return -1;
|
|
}
|