[PATHC,v2,5/9] ima: on soft reboot, save the measurement list
diff mbox

Message ID 1472596811-9596-6-git-send-email-zohar@linux.vnet.ibm.com
State New
Headers show

Commit Message

Mimi Zohar Aug. 30, 2016, 10:40 p.m. UTC
From: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>

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

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@linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 include/linux/ima.h                | 12 ++++++
 kernel/kexec_file.c                |  4 ++
 security/integrity/ima/ima_kexec.c | 88 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+)

Comments

Dave Young Sept. 1, 2016, 1:57 a.m. UTC | #1
Hi, Mimi

On 08/30/16 at 06:40pm, Mimi Zohar wrote:
> From: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> 
> This patch uses the kexec buffer passing mechanism to pass the
> serialized IMA binary_runtime_measurements to the next kernel.
> 
> 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@linux.vnet.ibm.com>
> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> ---
>  include/linux/ima.h                | 12 ++++++
>  kernel/kexec_file.c                |  4 ++
>  security/integrity/ima/ima_kexec.c | 88 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 104 insertions(+)
> 
> 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 0e90d14..9585861 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>
> @@ -200,6 +201,9 @@ 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_kexec.c b/security/integrity/ima/ima_kexec.c
> index e77ca9d..0e4d0db 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -23,6 +23,11 @@
>  
>  #include "ima.h"
>  
> +#ifdef CONFIG_IMA_KEXEC
> +/* Physical address of the measurement buffer in the next kernel. */
> +static unsigned long kexec_buffer_load_addr;
> +static size_t kexec_segment_size;
> +
>  static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
>  				     unsigned long segment_size)
>  {
> @@ -75,6 +80,89 @@ out:
>  }
>  
>  /*
> + * Called during kexec execute so that IMA can save the measurement list.
> + */
> +static int ima_update_kexec_buffer(struct notifier_block *self,
> +				   unsigned long action, void *data)
> +{
> +	void *kexec_buffer = NULL;
> +	size_t kexec_buffer_size;
> +	int ret;
> +
> +	if (!kexec_in_progress)
> +		return NOTIFY_OK;
> +
> +	kexec_buffer_size = ima_get_binary_runtime_size();
> +	if (kexec_buffer_size >
> +	    (kexec_segment_size - sizeof(struct ima_kexec_hdr))) {
> +		pr_err("Binary measurement list grew too large.\n");
> +		goto out;
> +	}
> +
> +	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");
> +		goto out;
> +	}
> +	ret = kexec_update_segment(kexec_buffer, kexec_buffer_size,
> +				   kexec_buffer_load_addr, kexec_segment_size);
> +	if (ret)
> +		pr_err("Error updating kexec buffer: %d\n", ret);
> +out:
> +	return NOTIFY_OK;
> +}
> +
> +struct notifier_block update_buffer_nb = {
> +	.notifier_call = ima_update_kexec_buffer,
> +};
> +
> +/*
> + * Called during kexec_file_load so that IMA can add a segment to the kexec
> + * image for the measurement list for the next kernel.
> + */
> +void ima_add_kexec_buffer(struct kimage *image)
> +{
> +	static int registered = 0;
> +	struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
> +				  .buf_min = 0, .buf_max = ULONG_MAX,
> +				  .top_down = true, .skip_checksum = true };
> +	int ret;
> +
> +	if (!kexec_can_hand_over_buffer())
> +		return;
> +
> +	kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + PAGE_SIZE,
> +				   PAGE_SIZE);
> +
> +	if (kexec_segment_size >= (ULONG_MAX - sizeof(long))) {
> +		pr_err("Binary measurement list too large.\n");
> +		return;
> +	}

Now we added a limitation that total segment size can not be larger than
half of totalram. see kernel/kexec_core.c sanity_check_segment_list()

So can it fail early here if kexec_segment_size is over half of total
ram?

> +
> +	/* Ask not to checksum the segment, we will update it later. */
> +	kbuf.buffer = NULL;
> +	kbuf.bufsz = 0;
> +	kbuf.memsz = kexec_segment_size;
> +	ret = kexec_add_handover_buffer(&kbuf);
> +	if (ret) {
> +		pr_err("Error passing over kexec measurement buffer.\n");
> +		return;
> +	}
> +	kexec_buffer_load_addr = kbuf.mem;
> +
> +	pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
> +		 kexec_buffer_load_addr);
> +
> +	if (registered)
> +		return;
> +
> +	register_reboot_notifier(&update_buffer_nb);
> +	registered = 1;
> +}
> +#endif /* IMA_KEXEC */
> +
> +/*
>   * Restore the measurement list from the previous kernel.
>   */
>  void ima_load_kexec_buffer(void)
> -- 
> 2.1.0
> 


Thanks
Dave
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Mimi Zohar Sept. 2, 2016, 1:22 p.m. UTC | #2
Hi Dave,

On Thu, 2016-09-01 at 09:57 +0800, Dave Young wrote:
> On 08/30/16 at 06:40pm, Mimi Zohar wrote:

> > + * Called during kexec_file_load so that IMA can add a segment to the kexec
> > + * image for the measurement list for the next kernel.
> > + */
> > +void ima_add_kexec_buffer(struct kimage *image)
> > +{
> > +	static int registered = 0;
> > +	struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
> > +				  .buf_min = 0, .buf_max = ULONG_MAX,
> > +				  .top_down = true, .skip_checksum = true };
> > +	int ret;
> > +
> > +	if (!kexec_can_hand_over_buffer())
> > +		return;
> > +
> > +	kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + PAGE_SIZE,
> > +				   PAGE_SIZE);
> > +
> > +	if (kexec_segment_size >= (ULONG_MAX - sizeof(long))) {
> > +		pr_err("Binary measurement list too large.\n");
> > +		return;
> > +	}
> 
> Now we added a limitation that total segment size can not be larger than
> half of totalram. see kernel/kexec_core.c sanity_check_segment_list()
> 
> So can it fail early here if kexec_segment_size is over half of total
> ram?

Sure, I'll include this change in the next post.

Mimi

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Patch
diff mbox

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 0e90d14..9585861 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>
@@ -200,6 +201,9 @@  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_kexec.c b/security/integrity/ima/ima_kexec.c
index e77ca9d..0e4d0db 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -23,6 +23,11 @@ 
 
 #include "ima.h"
 
+#ifdef CONFIG_IMA_KEXEC
+/* Physical address of the measurement buffer in the next kernel. */
+static unsigned long kexec_buffer_load_addr;
+static size_t kexec_segment_size;
+
 static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
 				     unsigned long segment_size)
 {
@@ -75,6 +80,89 @@  out:
 }
 
 /*
+ * Called during kexec execute so that IMA can save the measurement list.
+ */
+static int ima_update_kexec_buffer(struct notifier_block *self,
+				   unsigned long action, void *data)
+{
+	void *kexec_buffer = NULL;
+	size_t kexec_buffer_size;
+	int ret;
+
+	if (!kexec_in_progress)
+		return NOTIFY_OK;
+
+	kexec_buffer_size = ima_get_binary_runtime_size();
+	if (kexec_buffer_size >
+	    (kexec_segment_size - sizeof(struct ima_kexec_hdr))) {
+		pr_err("Binary measurement list grew too large.\n");
+		goto out;
+	}
+
+	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");
+		goto out;
+	}
+	ret = kexec_update_segment(kexec_buffer, kexec_buffer_size,
+				   kexec_buffer_load_addr, kexec_segment_size);
+	if (ret)
+		pr_err("Error updating kexec buffer: %d\n", ret);
+out:
+	return NOTIFY_OK;
+}
+
+struct notifier_block update_buffer_nb = {
+	.notifier_call = ima_update_kexec_buffer,
+};
+
+/*
+ * Called during kexec_file_load so that IMA can add a segment to the kexec
+ * image for the measurement list for the next kernel.
+ */
+void ima_add_kexec_buffer(struct kimage *image)
+{
+	static int registered = 0;
+	struct kexec_buf kbuf = { .image = image, .buf_align = PAGE_SIZE,
+				  .buf_min = 0, .buf_max = ULONG_MAX,
+				  .top_down = true, .skip_checksum = true };
+	int ret;
+
+	if (!kexec_can_hand_over_buffer())
+		return;
+
+	kexec_segment_size = ALIGN(ima_get_binary_runtime_size() + PAGE_SIZE,
+				   PAGE_SIZE);
+
+	if (kexec_segment_size >= (ULONG_MAX - sizeof(long))) {
+		pr_err("Binary measurement list too large.\n");
+		return;
+	}
+
+	/* Ask not to checksum the segment, we will update it later. */
+	kbuf.buffer = NULL;
+	kbuf.bufsz = 0;
+	kbuf.memsz = kexec_segment_size;
+	ret = kexec_add_handover_buffer(&kbuf);
+	if (ret) {
+		pr_err("Error passing over kexec measurement buffer.\n");
+		return;
+	}
+	kexec_buffer_load_addr = kbuf.mem;
+
+	pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
+		 kexec_buffer_load_addr);
+
+	if (registered)
+		return;
+
+	register_reboot_notifier(&update_buffer_nb);
+	registered = 1;
+}
+#endif /* IMA_KEXEC */
+
+/*
  * Restore the measurement list from the previous kernel.
  */
 void ima_load_kexec_buffer(void)