[PATCH v5 06/10] ima: on soft reboot, save the measurement list
Mimi Zohar
zohar at linux.vnet.ibm.com
Mon Sep 26 10:30:25 PDT 2016
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.
Changelog v5:
- move writing the IMA measurement list to kexec load and remove
from kexec execute.
- remove registering notifier to call update on kexec execute
- add includes needed by code in this patch to ima_kexec.c (Thiago)
- fold patch "ima: serialize the binary_runtime_measurements"
into this patch.
Changelog v4:
- Revert the skip_checksum change. Instead calculate the checksum
with the measurement list segment, on update validate the existing
checksum before re-calulating a new checksum with the updated
measurement list.
Changelog v3:
- Request a kexec segment for storing the measurement list a half page,
not a full page, more than needed for additional measurements.
- Added binary_runtime_size overflow test
- Limit maximum number of pages needed for kexec_segment_size to half
of totalram_pages. (Dave Young)
Changelog v2:
- Fix build issue by defining a stub ima_add_kexec_buffer and stub
struct kimage when CONFIG_IMA=n and CONFIG_IMA_KEXEC=n. (Fenguang Wu)
- removed kexec_add_handover_buffer() checksum argument.
- added skip_checksum member to kexec_buf
- only register reboot notifier once
Changelog v1:
- updated to call IMA functions (Mimi)
- move code from ima_template.c to ima_kexec.c (Mimi)
Signed-off-by: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
---
include/linux/ima.h | 12 ++++
kernel/kexec_file.c | 4 ++
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_fs.c | 2 +-
security/integrity/ima/ima_kexec.c | 117 +++++++++++++++++++++++++++++++++++++
5 files changed, 135 insertions(+), 1 deletion(-)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 0eb7c2e..7f6952f 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -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,
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 0c2df7f..b56a558 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -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);
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index ea1dcc4..139dec6 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -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);
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index c07a384..66e5dd5 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -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;
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 36afd0f..2c4824a 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -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.
*/
--
2.1.0
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