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ima: on soft reboot, save the measurement list 

The TPM PCRs are only reset on a hard reboot.  In order to validate a
TPM's quote after a soft reboot (eg.  kexec -e), the IMA measurement
list of the running kernel must be saved and restored on boot.

This patch uses the kexec buffer passing mechanism to pass the
serialized IMA binary_runtime_measurements to the next kernel.

Link: http://lkml.kernel.org/r/1480554346-29071-7-git-send-email-zohar@linux.vnet.ibm.com
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Andreas Steffen <andreas.steffen@strongswan.org>
Cc: Josh Sklar <sklar@linux.vnet.ibm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mimi Zohar 2016-12-19 16:22:48 -08:00 committed by Linus Torvalds
parent ab6b1d1fc4
commit 7b8589cc29
5 changed files with 135 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
include/linux/ima.h
View File

@ -11,6 +11,7 @@
#define _LINUX_IMA_H
#include <linux/fs.h>
#include <linux/kexec.h>
struct linux_binprm;
#ifdef CONFIG_IMA
@ -23,6 +24,10 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
enum kernel_read_file_id id);
extern void ima_post_path_mknod(struct dentry *dentry);
#ifdef CONFIG_IMA_KEXEC
extern void ima_add_kexec_buffer(struct kimage *image);
#endif
#else
static inline int ima_bprm_check(struct linux_binprm *bprm)
{
@ -62,6 +67,13 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
#endif /* CONFIG_IMA */
#ifndef CONFIG_IMA_KEXEC
struct kimage;
static inline void ima_add_kexec_buffer(struct kimage *image)
{}
#endif
#ifdef CONFIG_IMA_APPRAISE
extern void ima_inode_post_setattr(struct dentry *dentry);
extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,

4
kernel/kexec_file.c
View File

@ -19,6 +19,7 @@
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/fs.h>
#include <linux/ima.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <linux/syscalls.h>
@ -132,6 +133,9 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
return ret;
image->kernel_buf_len = size;
/* IMA needs to pass the measurement list to the next kernel. */
ima_add_kexec_buffer(image);
/* Call arch image probe handlers */
ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
image->kernel_buf_len);

1
security/integrity/ima/ima.h
View File

@ -143,6 +143,7 @@ void ima_print_digest(struct seq_file *m, u8 *digest, u32 size);
struct ima_template_desc *ima_template_desc_current(void);
int ima_restore_measurement_entry(struct ima_template_entry *entry);
int ima_restore_measurement_list(loff_t bufsize, void *buf);
int ima_measurements_show(struct seq_file *m, void *v);
unsigned long ima_get_binary_runtime_size(void);
int ima_init_template(void);

2
security/integrity/ima/ima_fs.c
View File

@ -116,7 +116,7 @@ void ima_putc(struct seq_file *m, void *data, int datalen)
* [eventdata length]
* eventdata[n]=template specific data
*/
static int ima_measurements_show(struct seq_file *m, void *v)
int ima_measurements_show(struct seq_file *m, void *v)
{
/* the list never shrinks, so we don't need a lock here */
struct ima_queue_entry *qe = v;

117
security/integrity/ima/ima_kexec.c
View File

@ -10,8 +10,125 @@
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <linux/seq_file.h>
#include <linux/vmalloc.h>
#include <linux/kexec.h>
#include "ima.h"
#ifdef CONFIG_IMA_KEXEC
static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
unsigned long segment_size)
{
struct ima_queue_entry *qe;
struct seq_file file;
struct ima_kexec_hdr khdr = {
.version = 1, .buffer_size = 0, .count = 0};
int ret = 0;
/* segment size can't change between kexec load and execute */
file.buf = vmalloc(segment_size);
if (!file.buf) {
ret = -ENOMEM;
goto out;
}
file.size = segment_size;
file.read_pos = 0;
file.count = sizeof(khdr); /* reserved space */
list_for_each_entry_rcu(qe, &ima_measurements, later) {
if (file.count < file.size) {
khdr.count++;
ima_measurements_show(&file, qe);
} else {
ret = -EINVAL;
break;
}
}
if (ret < 0)
goto out;
/*
* fill in reserved space with some buffer details
* (eg. version, buffer size, number of measurements)
*/
khdr.buffer_size = file.count;
memcpy(file.buf, &khdr, sizeof(khdr));
print_hex_dump(KERN_DEBUG, "ima dump: ", DUMP_PREFIX_NONE,
16, 1, file.buf,
file.count < 100 ? file.count : 100, true);
*buffer_size = file.count;
*buffer = file.buf;
out:
if (ret == -EINVAL)
vfree(file.buf);
return ret;
}
/*
* Called during kexec_file_load so that IMA can add a segment to the kexec
* image for the measurement list for the next kernel.
*
* This function assumes that kexec_mutex is held.
*/
void ima_add_kexec_buffer(struct kimage *image)
{
struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
.buf_min = 0, .buf_max = ULONG_MAX,
.top_down = true };
unsigned long binary_runtime_size;
/* use more understandable variable names than defined in kbuf */
void *kexec_buffer = NULL;
size_t kexec_buffer_size;
size_t kexec_segment_size;
int ret;
/*
* Reserve an extra half page of memory for additional measurements
* added during the kexec load.
*/
binary_runtime_size = ima_get_binary_runtime_size();
if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE)
kexec_segment_size = ULONG_MAX;
else
kexec_segment_size = ALIGN(ima_get_binary_runtime_size() +
PAGE_SIZE / 2, PAGE_SIZE);
if ((kexec_segment_size == ULONG_MAX) ||
((kexec_segment_size >> PAGE_SHIFT) > totalram_pages / 2)) {
pr_err("Binary measurement list too large.\n");
return;
}
ima_dump_measurement_list(&kexec_buffer_size, &kexec_buffer,
kexec_segment_size);
if (!kexec_buffer) {
pr_err("Not enough memory for the kexec measurement buffer.\n");
return;
}
kbuf.buffer = kexec_buffer;
kbuf.bufsz = kexec_buffer_size;
kbuf.memsz = kexec_segment_size;
ret = kexec_add_buffer(&kbuf);
if (ret) {
pr_err("Error passing over kexec measurement buffer.\n");
return;
}
ret = arch_ima_add_kexec_buffer(image, kbuf.mem, kexec_segment_size);
if (ret) {
pr_err("Error passing over kexec measurement buffer.\n");
return;
}
pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
kbuf.mem);
}
#endif /* IMA_KEXEC */
/*
* Restore the measurement list from the previous kernel.
*/