* [dm-devel] [PATCH 1/5] kexec_file: allow to place kexec_buf randomly
2023-06-01 7:24 [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Coiby Xu
@ 2023-06-01 7:24 ` Coiby Xu
2023-06-01 7:24 ` [dm-devel] [PATCH 2/5] crash_dump: save the LUKS volume key temporarily Coiby Xu
` (4 subsequent siblings)
5 siblings, 0 replies; 15+ messages in thread
From: Coiby Xu @ 2023-06-01 7:24 UTC (permalink / raw)
To: kexec
Cc: Baoquan He, x86, dm-devel, Pingfan Liu, linux-kernel, Dave Hansen,
Kairui Song, Eric Biederman, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young, Milan Broz
Currently, kexec_buf is placed in order which means for the same
machine, the info in the kexec_buf is always located at the same
position each time the machine is booted. This may cause a risk for
sensitive information like LUKS volume key. Now struct kexec_buf has a
new field random which indicates it's supposed to be placed in a random
position.
Suggested-by: Jan Pazdziora <jpazdziora@redhat.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
include/linux/kexec.h | 2 ++
kernel/kexec_file.c | 15 +++++++++++++++
2 files changed, 17 insertions(+)
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 22b5cd24f581..5b2440444112 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -172,6 +172,7 @@ int kexec_image_post_load_cleanup_default(struct kimage *image);
* @buf_min: The buffer can't be placed below this address.
* @buf_max: The buffer can't be placed above this address.
* @top_down: Allocate from top of memory.
+ * @random: Place the buffer at a random position.
*/
struct kexec_buf {
struct kimage *image;
@@ -183,6 +184,7 @@ struct kexec_buf {
unsigned long buf_min;
unsigned long buf_max;
bool top_down;
+ bool random;
};
int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf);
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f989f5f1933b..5dbfc119eb6a 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -25,6 +25,7 @@
#include <linux/elfcore.h>
#include <linux/kernel.h>
#include <linux/kernel_read_file.h>
+#include <linux/prandom.h>
#include <linux/syscalls.h>
#include <linux/vmalloc.h>
#include "kexec_internal.h"
@@ -419,6 +420,16 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
return ret;
}
+static unsigned long kexec_random_start(unsigned long start, unsigned long end)
+{
+ unsigned long temp_start;
+ unsigned short i;
+
+ get_random_bytes(&i, sizeof(unsigned short));
+ temp_start = start + (end - start) / USHRT_MAX * i;
+ return temp_start;
+}
+
static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
struct kexec_buf *kbuf)
{
@@ -427,6 +438,8 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
temp_end = min(end, kbuf->buf_max);
temp_start = temp_end - kbuf->memsz;
+ if (kbuf->random)
+ temp_start = kexec_random_start(temp_start, temp_end);
do {
/* align down start */
@@ -464,6 +477,8 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
unsigned long temp_start, temp_end;
temp_start = max(start, kbuf->buf_min);
+ if (kbuf->random)
+ temp_start = kexec_random_start(temp_start, end);
do {
temp_start = ALIGN(temp_start, kbuf->buf_align);
--
2.40.1
--
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https://listman.redhat.com/mailman/listinfo/dm-devel
^ permalink raw reply related [flat|nested] 15+ messages in thread* [dm-devel] [PATCH 2/5] crash_dump: save the LUKS volume key temporarily
2023-06-01 7:24 [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Coiby Xu
2023-06-01 7:24 ` [dm-devel] [PATCH 1/5] kexec_file: allow to place kexec_buf randomly Coiby Xu
@ 2023-06-01 7:24 ` Coiby Xu
2023-06-01 7:24 ` [dm-devel] [PATCH 3/5] crash_dump: retrieve LUKS volume key in kdump kernel Coiby Xu
` (3 subsequent siblings)
5 siblings, 0 replies; 15+ messages in thread
From: Coiby Xu @ 2023-06-01 7:24 UTC (permalink / raw)
To: kexec
Cc: Baoquan He, x86, dm-devel, Pingfan Liu, linux-kernel, Dave Hansen,
Kairui Song, Jan Pazdziora, Thomas Staudt, Vitaly Kuznetsov,
Dave Young, Milan Broz, Vivek Goyal
After having the volume key, crytpsetup/systemd-cryptsetup saves the
volume key as a logon key to its thread keyring and this key is
destroyed immediately with the terminated thread. So a temporary copy of
the volume key is needed in order to later save it to kdump reserved
memory when the crash kernel is loaded later.
crytpsetup/systemd-cryptsetup will write the key description to
/sys/kernel/crash_luks_volume_key so the kernel will read the logon key
and save a temporary copy for later user. kdump has 1 hour at maximum to
get the temporary copy before the key gets wiped. And after kdump
retrieves the key, the key will be wiped immediately.
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
include/linux/crash_core.h | 2 +
kernel/Makefile | 2 +-
kernel/crash_dump_luks.c | 90 ++++++++++++++++++++++++++++++++++++++
kernel/ksysfs.c | 19 ++++++++
4 files changed, 112 insertions(+), 1 deletion(-)
create mode 100644 kernel/crash_dump_luks.c
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index de62a722431e..596d83b8f362 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -83,5 +83,7 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram,
unsigned long long *crash_size, unsigned long long *crash_base);
int parse_crashkernel_low(char *cmdline, unsigned long long system_ram,
unsigned long long *crash_size, unsigned long long *crash_base);
+int crash_sysfs_luks_volume_key_write(const char *key_des, size_t count);
+int crash_pass_temp_luks_volume_key(void **addr, unsigned long *sz);
#endif /* LINUX_CRASH_CORE_H */
diff --git a/kernel/Makefile b/kernel/Makefile
index b69c95315480..8412afa4a9f0 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -118,7 +118,7 @@ obj-$(CONFIG_PERF_EVENTS) += events/
obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
obj-$(CONFIG_PADATA) += padata.o
-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
+obj-$(CONFIG_CRASH_DUMP) += crash_dump.o crash_dump_luks.o
obj-$(CONFIG_JUMP_LABEL) += jump_label.o
obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
obj-$(CONFIG_TORTURE_TEST) += torture.o
diff --git a/kernel/crash_dump_luks.c b/kernel/crash_dump_luks.c
new file mode 100644
index 000000000000..2d88b77a93f8
--- /dev/null
+++ b/kernel/crash_dump_luks.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <keys/user-type.h>
+#include <linux/crash_dump.h>
+
+static u8 *luks_volume_key;
+static unsigned int luks_volume_key_size;
+
+void wipe_luks_volume_key(void)
+{
+ if (luks_volume_key) {
+ memset(luks_volume_key, 0, luks_volume_key_size * sizeof(u8));
+ kfree(luks_volume_key);
+ luks_volume_key = NULL;
+ }
+}
+
+static void _wipe_luks_volume_key(struct work_struct *dummy)
+{
+ wipe_luks_volume_key();
+}
+
+static DECLARE_DELAYED_WORK(wipe_luks_volume_key_work, _wipe_luks_volume_key);
+
+static unsigned __read_mostly wipe_key_delay = 3600; /* 1 hour */
+
+static int crash_save_temp_luks_volume_key(const char *key_desc, size_t count)
+{
+ const struct user_key_payload *ukp;
+ struct key *key;
+
+
+ if (luks_volume_key) {
+ memset(luks_volume_key, 0, luks_volume_key_size * sizeof(u8));
+ kfree(luks_volume_key);
+ }
+
+ pr_debug("Requesting key %s", key_desc);
+ key = request_key(&key_type_logon, key_desc, NULL);
+
+ if (IS_ERR(key)) {
+ pr_debug("No such key %s", key_desc);
+ return PTR_ERR(key);
+ }
+
+ ukp = user_key_payload_locked(key);
+ if (!ukp)
+ return -EKEYREVOKED;
+
+ luks_volume_key = kmalloc(ukp->datalen, GFP_KERNEL);
+ if (!luks_volume_key)
+ return -ENOMEM;
+ memcpy(luks_volume_key, ukp->data, ukp->datalen);
+ luks_volume_key_size = ukp->datalen;
+ pr_debug("LUKS master key (size=%u): %8ph\n", luks_volume_key_size, luks_volume_key);
+ schedule_delayed_work(&wipe_luks_volume_key_work,
+ round_jiffies_relative(wipe_key_delay * HZ));
+ return 0;
+}
+
+int crash_sysfs_luks_volume_key_write(const char *key_desc, size_t count)
+{
+ if (!is_kdump_kernel())
+ return crash_save_temp_luks_volume_key(key_desc, count);
+ return -EINVAL;
+}
+EXPORT_SYMBOL(crash_sysfs_luks_volume_key_write);
+
+int crash_pass_temp_luks_volume_key(void **addr, unsigned long *sz)
+{
+ unsigned long luks_key_sz;
+ unsigned char *buf;
+ unsigned int *size_ptr;
+
+ if (!luks_volume_key)
+ return -EINVAL;
+
+ luks_key_sz = sizeof(unsigned int) + luks_volume_key_size * sizeof(u8);
+
+ buf = vzalloc(luks_key_sz);
+ if (!buf)
+ return -ENOMEM;
+
+ size_ptr = (unsigned int *)buf;
+ memcpy(size_ptr, &luks_volume_key_size, sizeof(unsigned int));
+ memcpy(size_ptr + 1, luks_volume_key, luks_volume_key_size * sizeof(u8));
+ *addr = buf;
+ *sz = luks_key_sz;
+ wipe_luks_volume_key();
+ return 0;
+}
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index aad7a3bfd846..cc64a895c334 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -165,6 +165,24 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
}
KERNEL_ATTR_RO(vmcoreinfo);
+static ssize_t crash_luks_volume_key_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ return 0;
+}
+
+static ssize_t crash_luks_volume_key_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret;
+
+ ret = crash_sysfs_luks_volume_key_write(buf, count);
+ return ret < 0 ? ret : count;
+}
+KERNEL_ATTR_RW(crash_luks_volume_key);
+
#endif /* CONFIG_CRASH_CORE */
/* whether file capabilities are enabled */
@@ -255,6 +273,7 @@ static struct attribute * kernel_attrs[] = {
#endif
#ifdef CONFIG_CRASH_CORE
&vmcoreinfo_attr.attr,
+ &crash_luks_volume_key_attr.attr,
#endif
#ifndef CONFIG_TINY_RCU
&rcu_expedited_attr.attr,
--
2.40.1
--
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https://listman.redhat.com/mailman/listinfo/dm-devel
^ permalink raw reply related [flat|nested] 15+ messages in thread* [dm-devel] [PATCH 3/5] crash_dump: retrieve LUKS volume key in kdump kernel
2023-06-01 7:24 [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Coiby Xu
2023-06-01 7:24 ` [dm-devel] [PATCH 1/5] kexec_file: allow to place kexec_buf randomly Coiby Xu
2023-06-01 7:24 ` [dm-devel] [PATCH 2/5] crash_dump: save the LUKS volume key temporarily Coiby Xu
@ 2023-06-01 7:24 ` Coiby Xu
2023-06-01 7:24 ` [dm-devel] [PATCH 4/5] x86/crash: pass the LUKS volume key to " Coiby Xu
` (2 subsequent siblings)
5 siblings, 0 replies; 15+ messages in thread
From: Coiby Xu @ 2023-06-01 7:24 UTC (permalink / raw)
To: kexec
Cc: Baoquan He, x86, dm-devel, Pingfan Liu, linux-kernel, Dave Hansen,
Kairui Song, Jan Pazdziora, Thomas Staudt, Vitaly Kuznetsov,
Dave Young, Milan Broz, Vivek Goyal
Crash kernel will retrieve the LUKS volume key based on the
luksvolumekey command line parameter. When libcryptsetup writes the key
description to /sys/kernel/crash_luks_volume_key, crash kernel will
create a thread keyring and add a logon key.
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
include/linux/crash_dump.h | 2 +
kernel/crash_dump_luks.c | 116 ++++++++++++++++++++++++++++++++++++-
2 files changed, 116 insertions(+), 2 deletions(-)
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 0f3a656293b0..bc848e058c64 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -15,6 +15,8 @@
extern unsigned long long elfcorehdr_addr;
extern unsigned long long elfcorehdr_size;
+extern unsigned long long luks_volume_key_addr;
+
#ifdef CONFIG_CRASH_DUMP
extern int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size);
extern void elfcorehdr_free(unsigned long long addr);
diff --git a/kernel/crash_dump_luks.c b/kernel/crash_dump_luks.c
index 2d88b77a93f8..63718db318c3 100644
--- a/kernel/crash_dump_luks.c
+++ b/kernel/crash_dump_luks.c
@@ -1,7 +1,82 @@
// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/key.h>
+#include <linux/keyctl.h>
#include <keys/user-type.h>
#include <linux/crash_dump.h>
+unsigned long long luks_volume_key_addr;
+EXPORT_SYMBOL_GPL(luks_volume_key_addr);
+
+static int __init setup_luksvolumekey(char *arg)
+{
+ char *end;
+
+ if (!arg)
+ return -EINVAL;
+ luks_volume_key_addr = memparse(arg, &end);
+ if (end > arg)
+ return 0;
+
+ luks_volume_key_addr = 0;
+ return -EINVAL;
+}
+
+early_param("luksvolumekey", setup_luksvolumekey);
+
+/*
+ * Architectures may override this function to read LUKS master key
+ */
+ssize_t __weak luks_key_read(char *buf, size_t count, u64 *ppos)
+{
+ struct kvec kvec = { .iov_base = buf, .iov_len = count };
+ struct iov_iter iter;
+
+ iov_iter_kvec(&iter, READ, &kvec, 1, count);
+ return read_from_oldmem(&iter, count, ppos, false);
+}
+
+static int retrive_kdump_luks_volume_key(u8 *buffer, unsigned int *sz)
+{
+ unsigned int key_size;
+ size_t lukskeybuf_sz;
+ unsigned int *size_ptr;
+ char *lukskeybuf;
+ u64 addr;
+ int r;
+
+ if (luks_volume_key_addr == 0) {
+ pr_debug("LUKS master key memory address inaccessible");
+ return -EINVAL;
+ }
+
+ addr = luks_volume_key_addr;
+
+ /* Read LUKS master key size */
+ r = luks_key_read((char *)&key_size, sizeof(unsigned int), &addr);
+
+ if (r < 0)
+ return r;
+
+ pr_debug("Retrieve LUKS master key: size=%u\n", key_size);
+ /* Read in LUKS maste rkey */
+ lukskeybuf_sz = sizeof(unsigned int) + key_size * sizeof(u8);
+ lukskeybuf = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
+ get_order(lukskeybuf_sz));
+ if (!lukskeybuf)
+ return -ENOMEM;
+
+ addr = luks_volume_key_addr;
+ r = luks_key_read((char *)lukskeybuf, lukskeybuf_sz, &addr);
+
+ if (r < 0)
+ return r;
+ size_ptr = (unsigned int *)lukskeybuf;
+ memcpy(buffer, size_ptr + 1, key_size * sizeof(u8));
+ pr_debug("Retrieve LUKS master key (size=%u): %48ph...\n", key_size, buffer);
+ *sz = key_size;
+ return 0;
+}
+
static u8 *luks_volume_key;
static unsigned int luks_volume_key_size;
@@ -23,12 +98,48 @@ static DECLARE_DELAYED_WORK(wipe_luks_volume_key_work, _wipe_luks_volume_key);
static unsigned __read_mostly wipe_key_delay = 3600; /* 1 hour */
+static int retore_luks_volume_key_to_thread_keyring(const char *key_desc)
+{
+ key_ref_t keyring_ref, key_ref;
+ int ret;
+
+ /* find the target keyring (which must be writable) */
+ keyring_ref = lookup_user_key(KEY_SPEC_THREAD_KEYRING, 0x01, KEY_NEED_WRITE);
+ if (IS_ERR(keyring_ref)) {
+ pr_alert("Failed to get keyring");
+ return PTR_ERR(keyring_ref);
+ }
+
+ luks_volume_key = kmalloc(128, GFP_KERNEL);
+ ret = retrive_kdump_luks_volume_key(luks_volume_key, &luks_volume_key_size);
+ if (ret) {
+ kfree(luks_volume_key);
+ return ret;
+ }
+
+ /* create or update the requested key and add it to the target keyring */
+ key_ref = key_create_or_update(keyring_ref, "logon", key_desc,
+ luks_volume_key, luks_volume_key_size,
+ KEY_PERM_UNDEF, KEY_ALLOC_IN_QUOTA);
+
+ if (!IS_ERR(key_ref)) {
+ ret = key_ref_to_ptr(key_ref)->serial;
+ key_ref_put(key_ref);
+ pr_alert("Success adding key %s", key_desc);
+ } else {
+ ret = PTR_ERR(key_ref);
+ pr_alert("Error when adding key");
+ }
+
+ key_ref_put(keyring_ref);
+ return ret;
+}
+
static int crash_save_temp_luks_volume_key(const char *key_desc, size_t count)
{
const struct user_key_payload *ukp;
struct key *key;
-
if (luks_volume_key) {
memset(luks_volume_key, 0, luks_volume_key_size * sizeof(u8));
kfree(luks_volume_key);
@@ -61,7 +172,8 @@ int crash_sysfs_luks_volume_key_write(const char *key_desc, size_t count)
{
if (!is_kdump_kernel())
return crash_save_temp_luks_volume_key(key_desc, count);
- return -EINVAL;
+ else
+ return retore_luks_volume_key_to_thread_keyring(key_desc);
}
EXPORT_SYMBOL(crash_sysfs_luks_volume_key_write);
--
2.40.1
--
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^ permalink raw reply related [flat|nested] 15+ messages in thread* [dm-devel] [PATCH 4/5] x86/crash: pass the LUKS volume key to kdump kernel
2023-06-01 7:24 [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Coiby Xu
` (2 preceding siblings ...)
2023-06-01 7:24 ` [dm-devel] [PATCH 3/5] crash_dump: retrieve LUKS volume key in kdump kernel Coiby Xu
@ 2023-06-01 7:24 ` Coiby Xu
2023-06-01 7:24 ` [dm-devel] [PATCH 5/5] x86/crash: make the page that stores the LUKS volume key inaccessible Coiby Xu
2023-06-02 21:34 ` [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Eric Biggers
5 siblings, 0 replies; 15+ messages in thread
From: Coiby Xu @ 2023-06-01 7:24 UTC (permalink / raw)
To: kexec
Cc: Dave Hansen, H. Peter Anvin, Baoquan He, x86, dm-devel,
Pingfan Liu, linux-kernel, Dave Hansen, Kairui Song, Ingo Molnar,
Thomas Gleixner, Eric Biederman, Jan Pazdziora, Thomas Staudt,
Borislav Petkov, Vitaly Kuznetsov, Dave Young, Milan Broz
1st kernel will build up the kernel command parameter luksvolumekey as
similar to elfcorehdr to pass the memory address of the stored info of
LUKS volume key to kdump kernel.
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
arch/x86/include/asm/crash.h | 1 +
arch/x86/kernel/crash.c | 47 ++++++++++++++++++++++++++++++-
arch/x86/kernel/kexec-bzimage64.c | 7 +++++
include/linux/kexec.h | 4 +++
4 files changed, 58 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/crash.h b/arch/x86/include/asm/crash.h
index 8b6bd63530dc..485f75dce2ca 100644
--- a/arch/x86/include/asm/crash.h
+++ b/arch/x86/include/asm/crash.h
@@ -4,6 +4,7 @@
struct kimage;
+int crash_load_luks_volume_key(struct kimage *image);
int crash_load_segments(struct kimage *image);
int crash_setup_memmap_entries(struct kimage *image,
struct boot_params *params);
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index cdd92ab43cda..32d4a9e3badf 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -289,6 +289,7 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
unsigned long long mend)
{
unsigned long start, end;
+ int r;
cmem->ranges[0].start = mstart;
cmem->ranges[0].end = mend;
@@ -297,7 +298,19 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
/* Exclude elf header region */
start = image->elf_load_addr;
end = start + image->elf_headers_sz - 1;
- return crash_exclude_mem_range(cmem, start, end);
+ r = crash_exclude_mem_range(cmem, start, end);
+
+ if (r)
+ return r;
+
+ /* Exclude LUKS volume key region */
+ if (image->luks_volume_key_addr) {
+ start = image->luks_volume_key_addr;
+ end = start + image->luks_volume_key_sz - 1;
+ return crash_exclude_mem_range(cmem, start, end);
+ }
+
+ return r;
}
/* Prepare memory map for crash dump kernel */
@@ -368,6 +381,38 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
return ret;
}
+int crash_load_luks_volume_key(struct kimage *image)
+{
+ int ret;
+ struct kexec_buf kbuf = {
+ .image = image,
+ .buf_min = 0,
+ .buf_max = ULONG_MAX,
+ .top_down = false,
+ .random = true,
+ };
+
+ image->luks_volume_key_addr = 0;
+ ret = crash_pass_temp_luks_volume_key(&kbuf.buffer, &kbuf.bufsz);
+ if (ret)
+ return ret;
+
+ kbuf.memsz = kbuf.bufsz;
+ kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
+ kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+ ret = kexec_add_buffer(&kbuf);
+ if (ret) {
+ vfree((void *)kbuf.buffer);
+ return ret;
+ }
+ image->luks_volume_key_addr = kbuf.mem;
+ image->luks_volume_key_sz = kbuf.bufsz;
+ pr_debug("Loaded LUKS volume key at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+ image->luks_volume_key_addr, kbuf.bufsz, kbuf.bufsz);
+
+ return ret;
+}
+
int crash_load_segments(struct kimage *image)
{
int ret;
diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index a61c12c01270..a859e9e5c876 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -76,6 +76,10 @@ static int setup_cmdline(struct kimage *image, struct boot_params *params,
if (image->type == KEXEC_TYPE_CRASH) {
len = sprintf(cmdline_ptr,
"elfcorehdr=0x%lx ", image->elf_load_addr);
+
+ if (image->luks_volume_key_addr != 0)
+ len += sprintf(cmdline_ptr + len,
+ "luksvolumekey=0x%lx ", image->luks_volume_key_addr);
}
memcpy(cmdline_ptr + len, cmdline, cmdline_len);
cmdline_len += len;
@@ -433,6 +437,9 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
ret = crash_load_segments(image);
if (ret)
return ERR_PTR(ret);
+ ret = crash_load_luks_volume_key(image);
+ if (ret)
+ pr_debug("Either no LUKS volume key or error to retrieve the LUKS volume key\n");
}
/*
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 5b2440444112..20d213076e46 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -374,6 +374,10 @@ struct kimage {
void *elf_headers;
unsigned long elf_headers_sz;
unsigned long elf_load_addr;
+
+ /* LUKS volume key buffer */
+ unsigned long luks_volume_key_addr;
+ unsigned long luks_volume_key_sz;
};
/* kexec interface functions */
--
2.40.1
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^ permalink raw reply related [flat|nested] 15+ messages in thread* [dm-devel] [PATCH 5/5] x86/crash: make the page that stores the LUKS volume key inaccessible
2023-06-01 7:24 [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Coiby Xu
` (3 preceding siblings ...)
2023-06-01 7:24 ` [dm-devel] [PATCH 4/5] x86/crash: pass the LUKS volume key to " Coiby Xu
@ 2023-06-01 7:24 ` Coiby Xu
2023-06-02 21:34 ` [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Eric Biggers
5 siblings, 0 replies; 15+ messages in thread
From: Coiby Xu @ 2023-06-01 7:24 UTC (permalink / raw)
To: kexec
Cc: Dave Hansen, H. Peter Anvin, Baoquan He, x86, dm-devel,
Pingfan Liu, linux-kernel, Dave Hansen, Kairui Song, Ingo Molnar,
Thomas Gleixner, Jan Pazdziora, Thomas Staudt, Borislav Petkov,
Vitaly Kuznetsov, Dave Young, Milan Broz
This adds an addition layer of protection for the saved copy of LUKS
volume key. Trying to access the saved copy will cause page fault.
Suggested-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
arch/x86/kernel/machine_kexec_64.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 1a3e2c05a8a5..82d1ecb35827 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -546,9 +546,23 @@ static void kexec_mark_crashkres(bool protect)
kexec_mark_range(control, crashk_res.end, protect);
}
+static void kexec_mark_luks_volume_key_inaccessible(void)
+{
+ unsigned long start_paddr, end_paddr;
+ unsigned int nr_pages;
+
+ if (kexec_crash_image->luks_volume_key_addr) {
+ start_paddr = kexec_crash_image->luks_volume_key_addr;
+ end_paddr = start_paddr + kexec_crash_image->luks_volume_key_sz - 1;
+ nr_pages = (PAGE_ALIGN(end_paddr) - PAGE_ALIGN_DOWN(start_paddr))/PAGE_SIZE;
+ set_memory_np((unsigned long)phys_to_virt(start_paddr), nr_pages);
+ }
+}
+
void arch_kexec_protect_crashkres(void)
{
kexec_mark_crashkres(true);
+ kexec_mark_luks_volume_key_inaccessible();
}
void arch_kexec_unprotect_crashkres(void)
--
2.40.1
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^ permalink raw reply related [flat|nested] 15+ messages in thread* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-01 7:24 [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Coiby Xu
` (4 preceding siblings ...)
2023-06-01 7:24 ` [dm-devel] [PATCH 5/5] x86/crash: make the page that stores the LUKS volume key inaccessible Coiby Xu
@ 2023-06-02 21:34 ` Eric Biggers
2023-06-03 9:22 ` Milan Broz
5 siblings, 1 reply; 15+ messages in thread
From: Eric Biggers @ 2023-06-02 21:34 UTC (permalink / raw)
To: Coiby Xu
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young, Milan Broz
On Thu, Jun 01, 2023 at 03:24:39PM +0800, Coiby Xu wrote:
> [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
The kernel has no concept of LUKS at all. It provides dm-crypt, which LUKS
happens to use. But LUKS is a userspace concept.
This is a kernel patchset, so why does it make sense for it to be talking about
LUKS at all? Perhaps you mean dm-crypt?
- Eric
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^ permalink raw reply [flat|nested] 15+ messages in thread* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-02 21:34 ` [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key Eric Biggers
@ 2023-06-03 9:22 ` Milan Broz
2023-06-05 2:31 ` Coiby Xu
0 siblings, 1 reply; 15+ messages in thread
From: Milan Broz @ 2023-06-03 9:22 UTC (permalink / raw)
To: Eric Biggers, Coiby Xu
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young
On 6/2/23 23:34, Eric Biggers wrote:
> On Thu, Jun 01, 2023 at 03:24:39PM +0800, Coiby Xu wrote:
>> [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
>
> The kernel has no concept of LUKS at all. It provides dm-crypt, which LUKS
> happens to use. But LUKS is a userspace concept.
>
> This is a kernel patchset, so why does it make sense for it to be talking about
> LUKS at all? Perhaps you mean dm-crypt?
Exactly.
I had the same comment almost a year ago... and it still applies:
https://lore.kernel.org/all/c857dcf8-024e-ab8a-fd26-295ce2e0ae41@gmail.com/
Anyway, please fix the naming before this patchset can be read or reviewed!
LUKS is user-space key management only (on-disk metadata); the kernel has
no idea how the key is derived or what LUKS is - dm-crypt only knows the key
(either through keyring or directly in the mapping table).
Polluting kernel namespace with "luks" names variables is wrong - dm-crypt
is used in many other mappings (plain, bitlocker, veracrypt, ...)
Just use the dm-crypt key, do not reference LUKS at all.
Milan
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^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-03 9:22 ` Milan Broz
@ 2023-06-05 2:31 ` Coiby Xu
2023-06-05 7:09 ` Milan Broz
0 siblings, 1 reply; 15+ messages in thread
From: Coiby Xu @ 2023-06-05 2:31 UTC (permalink / raw)
To: Eric Biggers, Milan Broz
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young
Hi Eric and Milan,
On Sat, Jun 03, 2023 at 11:22:52AM +0200, Milan Broz wrote:
>On 6/2/23 23:34, Eric Biggers wrote:
>>On Thu, Jun 01, 2023 at 03:24:39PM +0800, Coiby Xu wrote:
>>>[PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
>>
>>The kernel has no concept of LUKS at all. It provides dm-crypt, which LUKS
>>happens to use. But LUKS is a userspace concept.
>>
>>This is a kernel patchset, so why does it make sense for it to be talking about
>>LUKS at all? Perhaps you mean dm-crypt?
>
>Exactly.
Thanks for raising the above concern! The use cases like CoreOS and
Confidential VMs explicitly want kdump to work for LUKS. And correct me
if I'm wrong, I think the two problems addressed by this patch set only
apply to LUKS so the kdump part of the kernel only cares about the LUKS
case. If there are use cases where similar approach is needed, I'll be
happy to make the solution more generic.
>
>I had the same comment almost a year ago... and it still applies:
>https://lore.kernel.org/all/c857dcf8-024e-ab8a-fd26-295ce2e0ae41@gmail.com/
>
> Anyway, please fix the naming before this patchset can be read or reviewed!
>
> LUKS is user-space key management only (on-disk metadata); the kernel has
> no idea how the key is derived or what LUKS is - dm-crypt only knows the key
> (either through keyring or directly in the mapping table).
>
> Polluting kernel namespace with "luks" names variables is wrong - dm-crypt
> is used in many other mappings (plain, bitlocker, veracrypt, ...)
> Just use the dm-crypt key, do not reference LUKS at all.
Thanks for the reminding! That comment was on the first RFC version. But
starting with "RFC v2", there is no longer any interaction with dm-crypt
(to save a copy of the LUKS volume key for the kdump kernel) and now I
make cryptsetup talks to the kdump part of the kernel via the sysfs to
reuse the volume key. So only the kdump part of the kernel needs to know
LUKS which is what it cares. Thus I don't think there is any kernel
namespace pollution now.
>
>Milan
>
--
Best regards,
Coiby
--
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^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-05 2:31 ` Coiby Xu
@ 2023-06-05 7:09 ` Milan Broz
2023-06-06 11:02 ` Coiby Xu
0 siblings, 1 reply; 15+ messages in thread
From: Milan Broz @ 2023-06-05 7:09 UTC (permalink / raw)
To: Coiby Xu, Eric Biggers
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young
On 6/5/23 04:31, Coiby Xu wrote:
> Hi Eric and Milan,
>
> On Sat, Jun 03, 2023 at 11:22:52AM +0200, Milan Broz wrote:
>> On 6/2/23 23:34, Eric Biggers wrote:
>>> On Thu, Jun 01, 2023 at 03:24:39PM +0800, Coiby Xu wrote:
>>>> [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
>>>
>>> The kernel has no concept of LUKS at all. It provides dm-crypt, which LUKS
>>> happens to use. But LUKS is a userspace concept.
>>>
>>> This is a kernel patchset, so why does it make sense for it to be talking about
>>> LUKS at all? Perhaps you mean dm-crypt?
>>
>> Exactly.
>
> Thanks for raising the above concern! The use cases like CoreOS and
> Confidential VMs explicitly want kdump to work for LUKS. And correct me
> if I'm wrong, I think the two problems addressed by this patch set only
> apply to LUKS so the kdump part of the kernel only cares about the LUKS
> case. If there are use cases where similar approach is needed, I'll be
> happy to make the solution more generic.
>
>>
>> I had the same comment almost a year ago... and it still applies:
>> https://lore.kernel.org/all/c857dcf8-024e-ab8a-fd26-295ce2e0ae41@gmail.com/
>>
>> Anyway, please fix the naming before this patchset can be read or reviewed!
>>
>> LUKS is user-space key management only (on-disk metadata); the kernel has
>> no idea how the key is derived or what LUKS is - dm-crypt only knows the key
>> (either through keyring or directly in the mapping table).
>>
>> Polluting kernel namespace with "luks" names variables is wrong - dm-crypt
>> is used in many other mappings (plain, bitlocker, veracrypt, ...)
>> Just use the dm-crypt key, do not reference LUKS at all.
>
> Thanks for the reminding! That comment was on the first RFC version. But
> starting with "RFC v2", there is no longer any interaction with dm-crypt
> (to save a copy of the LUKS volume key for the kdump kernel) and now I
> make cryptsetup talks to the kdump part of the kernel via the sysfs to
> reuse the volume key. So only the kdump part of the kernel needs to know
> LUKS which is what it cares. Thus I don't think there is any kernel
> namespace pollution now.
Hi,
I am sorry if I did understand correctly, but I thought that kdump is part
of the kernel.
I am trying to say that kernel generally has no concept of LUKS;
this is a userspace abstraction for key management.
Even the cryptsetup dm-crypt configuration mapping table generated from LUKS
has nothing LUKS special in it (only in DM-UUID as a name prefix).
So I do not understand why you need to mention LUKS even in kdump part.
Perhaps it is still only a naming problem, nothing more.
All you need is to preserve key and configuration parameters (for dm-crypt).
If it is set by cryptsetup, dmsetup, or any other way is not important - on this
kernel layer, it has nothing to do with LUKS key management metadata.
No problem if you support only LUKS in userspace, but really, all this machinery
should work for any dm-crypt devices. Perhaps your patch even works for it already.
Milan
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^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-05 7:09 ` Milan Broz
@ 2023-06-06 11:02 ` Coiby Xu
2023-06-07 6:14 ` Milan Broz
0 siblings, 1 reply; 15+ messages in thread
From: Coiby Xu @ 2023-06-06 11:02 UTC (permalink / raw)
To: Milan Broz
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Eric Biggers, Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young
On Mon, Jun 05, 2023 at 09:09:49AM +0200, Milan Broz wrote:
>On 6/5/23 04:31, Coiby Xu wrote:
>>Hi Eric and Milan,
>>
>>On Sat, Jun 03, 2023 at 11:22:52AM +0200, Milan Broz wrote:
>>>On 6/2/23 23:34, Eric Biggers wrote:
>>>>On Thu, Jun 01, 2023 at 03:24:39PM +0800, Coiby Xu wrote:
>>>>>[PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
>>>>
>>>>The kernel has no concept of LUKS at all. It provides dm-crypt, which LUKS
>>>>happens to use. But LUKS is a userspace concept.
>>>>
>>>>This is a kernel patchset, so why does it make sense for it to be talking about
>>>>LUKS at all? Perhaps you mean dm-crypt?
>>>
>>>Exactly.
>>
>>Thanks for raising the above concern! The use cases like CoreOS and
>>Confidential VMs explicitly want kdump to work for LUKS. And correct me
>>if I'm wrong, I think the two problems addressed by this patch set only
>>apply to LUKS so the kdump part of the kernel only cares about the LUKS
>>case. If there are use cases where similar approach is needed, I'll be
>>happy to make the solution more generic.
>>
>>>
>>>I had the same comment almost a year ago... and it still applies:
>>>https://lore.kernel.org/all/c857dcf8-024e-ab8a-fd26-295ce2e0ae41@gmail.com/
>>>
>>>Anyway, please fix the naming before this patchset can be read or reviewed!
>>>
>>>LUKS is user-space key management only (on-disk metadata); the kernel has
>>>no idea how the key is derived or what LUKS is - dm-crypt only knows the key
>>>(either through keyring or directly in the mapping table).
>>>
>>>Polluting kernel namespace with "luks" names variables is wrong - dm-crypt
>>>is used in many other mappings (plain, bitlocker, veracrypt, ...)
>>>Just use the dm-crypt key, do not reference LUKS at all.
>>
>>Thanks for the reminding! That comment was on the first RFC version. But
>>starting with "RFC v2", there is no longer any interaction with dm-crypt
>>(to save a copy of the LUKS volume key for the kdump kernel) and now I
>>make cryptsetup talks to the kdump part of the kernel via the sysfs to
>>reuse the volume key. So only the kdump part of the kernel needs to know
>>LUKS which is what it cares. Thus I don't think there is any kernel
>>namespace pollution now.
>
>Hi,
>
>I am sorry if I did understand correctly, but I thought that kdump is part
>of the kernel.
Yes, there is the kernel part of the kdump although there is also the
userspace part to make the feature complete:)
>
>I am trying to say that kernel generally has no concept of LUKS;
>this is a userspace abstraction for key management.
>
>Even the cryptsetup dm-crypt configuration mapping table generated from LUKS
>has nothing LUKS special in it (only in DM-UUID as a name prefix).
>
>So I do not understand why you need to mention LUKS even in kdump part.
>Perhaps it is still only a naming problem, nothing more.
>
>All you need is to preserve key and configuration parameters (for dm-crypt).
>If it is set by cryptsetup, dmsetup, or any other way is not important - on this
>kernel layer, it has nothing to do with LUKS key management metadata.
>
>No problem if you support only LUKS in userspace, but really, all this machinery
>should work for any dm-crypt devices. Perhaps your patch even works for it already.
Thanks for the explanation! After reflecting on your words for some
time, I realize I had an implicit assumption. I assumed is if I use a
name like dm_crypt_key instead of luks_volume_key, I need to support all
mappings like plain, bitlocker, veracrypt as mentioned by you and this
could mean much more efforts. So I'm not motivated to do that as
currently users only request kdump to work for LUKS.
But maybe I can divide the efforts into the kernel part and userspace
part. For the kernel part, almost no effort is needed since only
renaming is needed as pointed out by you. For the userpace part, maybe
it's OK to support preserving key only for LUKS2 in cryptsetup as hinted
by your last paragraph? Does it look good to you from the viewpoint of
the maintainer of cryptsetup?
>
>Milan
>
--
Best regards,
Coiby
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^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-06 11:02 ` Coiby Xu
@ 2023-06-07 6:14 ` Milan Broz
2023-06-07 12:39 ` Coiby Xu
0 siblings, 1 reply; 15+ messages in thread
From: Milan Broz @ 2023-06-07 6:14 UTC (permalink / raw)
To: Coiby Xu
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Eric Biggers, Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young
On 6/6/23 13:02, Coiby Xu wrote:
> On Mon, Jun 05, 2023 at 09:09:49AM +0200, Milan Broz wrote:
>> On 6/5/23 04:31, Coiby Xu wrote:
>>> Hi Eric and Milan,
>>>
>>> On Sat, Jun 03, 2023 at 11:22:52AM +0200, Milan Broz wrote:
>>>> On 6/2/23 23:34, Eric Biggers wrote:
>>>>> On Thu, Jun 01, 2023 at 03:24:39PM +0800, Coiby Xu wrote:
>>>>>> [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
>>>>>
>>>>> The kernel has no concept of LUKS at all. It provides dm-crypt, which LUKS
>>>>> happens to use. But LUKS is a userspace concept.
>>>>>
>>>>> This is a kernel patchset, so why does it make sense for it to be talking about
>>>>> LUKS at all? Perhaps you mean dm-crypt?
>>>>
>>>> Exactly.
>>>
>>> Thanks for raising the above concern! The use cases like CoreOS and
>>> Confidential VMs explicitly want kdump to work for LUKS. And correct me
>>> if I'm wrong, I think the two problems addressed by this patch set only
>>> apply to LUKS so the kdump part of the kernel only cares about the LUKS
>>> case. If there are use cases where similar approach is needed, I'll be
>>> happy to make the solution more generic.
>>>
>>>>
>>>> I had the same comment almost a year ago... and it still applies:
>>>> https://lore.kernel.org/all/c857dcf8-024e-ab8a-fd26-295ce2e0ae41@gmail.com/
>>>>
>>>> Anyway, please fix the naming before this patchset can be read or reviewed!
>>>>
>>>> LUKS is user-space key management only (on-disk metadata); the kernel has
>>>> no idea how the key is derived or what LUKS is - dm-crypt only knows the key
>>>> (either through keyring or directly in the mapping table).
>>>>
>>>> Polluting kernel namespace with "luks" names variables is wrong - dm-crypt
>>>> is used in many other mappings (plain, bitlocker, veracrypt, ...)
>>>> Just use the dm-crypt key, do not reference LUKS at all.
>>>
>>> Thanks for the reminding! That comment was on the first RFC version. But
>>> starting with "RFC v2", there is no longer any interaction with dm-crypt
>>> (to save a copy of the LUKS volume key for the kdump kernel) and now I
>>> make cryptsetup talks to the kdump part of the kernel via the sysfs to
>>> reuse the volume key. So only the kdump part of the kernel needs to know
>>> LUKS which is what it cares. Thus I don't think there is any kernel
>>> namespace pollution now.
>>
>> Hi,
>>
>> I am sorry if I did understand correctly, but I thought that kdump is part
>> of the kernel.
>
> Yes, there is the kernel part of the kdump although there is also the
> userspace part to make the feature complete:)
>
>>
>> I am trying to say that kernel generally has no concept of LUKS;
>> this is a userspace abstraction for key management.
>>
>> Even the cryptsetup dm-crypt configuration mapping table generated from LUKS
>> has nothing LUKS special in it (only in DM-UUID as a name prefix).
>>
>> So I do not understand why you need to mention LUKS even in kdump part.
>> Perhaps it is still only a naming problem, nothing more.
>>
>> All you need is to preserve key and configuration parameters (for dm-crypt).
>> If it is set by cryptsetup, dmsetup, or any other way is not important - on this
>> kernel layer, it has nothing to do with LUKS key management metadata.
>>
>> No problem if you support only LUKS in userspace, but really, all this machinery
>> should work for any dm-crypt devices. Perhaps your patch even works for it already.
>
> Thanks for the explanation! After reflecting on your words for some
> time, I realize I had an implicit assumption. I assumed is if I use a
> name like dm_crypt_key instead of luks_volume_key, I need to support all
> mappings like plain, bitlocker, veracrypt as mentioned by you and this
> could mean much more efforts. So I'm not motivated to do that as
> currently users only request kdump to work for LUKS.
Thanks, I think it is perfectly fine to implement just subset here.
> But maybe I can divide the efforts into the kernel part and userspace
> part. For the kernel part, almost no effort is needed since only
> renaming is needed as pointed out by you. For the userpace part, maybe
> it's OK to support preserving key only for LUKS2 in cryptsetup as hinted
> by your last paragraph? Does it look good to you from the viewpoint of
> the maintainer of cryptsetup?
My comment was just about proper naming in kernel, it is of course up to you
what you want to support in userspace (and even in kernel, extensions can
be added later).
Only LUKS2 uses keyring for volume key in dm-crypt as default option anyway.
I do not think you need any cryptsetup patches, all you need is to write
decrypted volume key from LUKS metadata with
cryptsetup luksDump ---dump-volume-key -volume-key-file <out> <device>
(or any code equivalent with libcryptsetup), am I correct?
Milan
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^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-07 6:14 ` Milan Broz
@ 2023-06-07 12:39 ` Coiby Xu
2023-06-08 10:39 ` Milan Broz
0 siblings, 1 reply; 15+ messages in thread
From: Coiby Xu @ 2023-06-07 12:39 UTC (permalink / raw)
To: Milan Broz
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Eric Biggers, Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Vitaly Kuznetsov, Dave Young
On Wed, Jun 07, 2023 at 08:14:44AM +0200, Milan Broz wrote:
>On 6/6/23 13:02, Coiby Xu wrote:
>>On Mon, Jun 05, 2023 at 09:09:49AM +0200, Milan Broz wrote:
>>>On 6/5/23 04:31, Coiby Xu wrote:
>>>>Hi Eric and Milan,
>>>>
>>>>On Sat, Jun 03, 2023 at 11:22:52AM +0200, Milan Broz wrote:
>>>>>On 6/2/23 23:34, Eric Biggers wrote:
>>>>>>On Thu, Jun 01, 2023 at 03:24:39PM +0800, Coiby Xu wrote:
>>>>>>>[PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
>>>>>>
>>>>>>The kernel has no concept of LUKS at all. It provides dm-crypt, which LUKS
>>>>>>happens to use. But LUKS is a userspace concept.
>>>>>>
>>>>>>This is a kernel patchset, so why does it make sense for it to be talking about
>>>>>>LUKS at all? Perhaps you mean dm-crypt?
>>>>>
>>>>>Exactly.
>>>>
>>>>Thanks for raising the above concern! The use cases like CoreOS and
>>>>Confidential VMs explicitly want kdump to work for LUKS. And correct me
>>>>if I'm wrong, I think the two problems addressed by this patch set only
>>>>apply to LUKS so the kdump part of the kernel only cares about the LUKS
>>>>case. If there are use cases where similar approach is needed, I'll be
>>>>happy to make the solution more generic.
>>>>
>>>>>
>>>>>I had the same comment almost a year ago... and it still applies:
>>>>>https://lore.kernel.org/all/c857dcf8-024e-ab8a-fd26-295ce2e0ae41@gmail.com/
>>>>>
>>>>>Anyway, please fix the naming before this patchset can be read or reviewed!
>>>>>
>>>>>LUKS is user-space key management only (on-disk metadata); the kernel has
>>>>>no idea how the key is derived or what LUKS is - dm-crypt only knows the key
>>>>>(either through keyring or directly in the mapping table).
>>>>>
>>>>>Polluting kernel namespace with "luks" names variables is wrong - dm-crypt
>>>>>is used in many other mappings (plain, bitlocker, veracrypt, ...)
>>>>>Just use the dm-crypt key, do not reference LUKS at all.
>>>>
>>>>Thanks for the reminding! That comment was on the first RFC version. But
>>>>starting with "RFC v2", there is no longer any interaction with dm-crypt
>>>>(to save a copy of the LUKS volume key for the kdump kernel) and now I
>>>>make cryptsetup talks to the kdump part of the kernel via the sysfs to
>>>>reuse the volume key. So only the kdump part of the kernel needs to know
>>>>LUKS which is what it cares. Thus I don't think there is any kernel
>>>>namespace pollution now.
>>>
>>>Hi,
>>>
>>>I am sorry if I did understand correctly, but I thought that kdump is part
>>>of the kernel.
>>
>>Yes, there is the kernel part of the kdump although there is also the
>>userspace part to make the feature complete:)
>>
>>>
>>>I am trying to say that kernel generally has no concept of LUKS;
>>>this is a userspace abstraction for key management.
>>>
>>>Even the cryptsetup dm-crypt configuration mapping table generated from LUKS
>>>has nothing LUKS special in it (only in DM-UUID as a name prefix).
>>>
>>>So I do not understand why you need to mention LUKS even in kdump part.
>>>Perhaps it is still only a naming problem, nothing more.
>>>
>>>All you need is to preserve key and configuration parameters (for dm-crypt).
>>>If it is set by cryptsetup, dmsetup, or any other way is not important - on this
>>>kernel layer, it has nothing to do with LUKS key management metadata.
>>>
>>>No problem if you support only LUKS in userspace, but really, all this machinery
>>>should work for any dm-crypt devices. Perhaps your patch even works for it already.
>>
>>Thanks for the explanation! After reflecting on your words for some
>>time, I realize I had an implicit assumption. I assumed is if I use a
>>name like dm_crypt_key instead of luks_volume_key, I need to support all
>>mappings like plain, bitlocker, veracrypt as mentioned by you and this
>>could mean much more efforts. So I'm not motivated to do that as
>>currently users only request kdump to work for LUKS.
>
>Thanks, I think it is perfectly fine to implement just subset here.
>
[...]
>
>My comment was just about proper naming in kernel, it is of course up to you
>what you want to support in userspace (and even in kernel, extensions can
>be added later).
Thanks for the confirmation!
>
>Only LUKS2 uses keyring for volume key in dm-crypt as default option anyway.
Thanks for the info!
>I do not think you need any cryptsetup patches, all you need is to write
>decrypted volume key from LUKS metadata with
> cryptsetup luksDump ---dump-volume-key -volume-key-file <out> <device>
>(or any code equivalent with libcryptsetup), am I correct?
Correct me if I'm wrong, but I don't think there will be a safer way to
preserve key without patching cryptsetup. Actually the --dump-volume-key
approach has been proposed before and I agree with your conclusion [1]
on that approach i.e. "passing volume key this way is quite insecure".
Without patching cryptsetup, even if I save the volume key in the memory
reserved for the kdump kernel, I need to retrieve this key in the
userspace to unlock the LUKS device which may lead to quite a security
vulnerability.
I respect the efforts from you and the cryptsetup community to make LUKS
as secure as possible. And kdump is used in product environment. Kdump
is to a server as a black box is to an aircraft. So by no means I want
to reverse the used security measures and patching cryptsetup can allow
to keep the security measures. One concern raised by you against "FRC
v1" was a copy of the LUKS volume key for the kdump kernel creates an
attack vector. I took this feedback seriously and have sought advice
from my colleagues to implement the countermeasures ([PATCH 1/5] and
[Patch 4/5]).
[1] https://yhbt.net/lore/all/e5abd089-3398-fdb4-7991-0019be434b79@gmail.com/
>
>Milan
>
--
Best regards,
Coiby
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^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-07 12:39 ` Coiby Xu
@ 2023-06-08 10:39 ` Milan Broz
2023-06-09 9:58 ` Coiby Xu
0 siblings, 1 reply; 15+ messages in thread
From: Milan Broz @ 2023-06-08 10:39 UTC (permalink / raw)
To: Coiby Xu
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Eric Biggers, Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Ondrej Kozina, Vitaly Kuznetsov, Dave Young
On 6/7/23 14:39, Coiby Xu wrote:
...
>> I do not think you need any cryptsetup patches, all you need is to write
>> decrypted volume key from LUKS metadata with
>> cryptsetup luksDump ---dump-volume-key -volume-key-file <out> <device>
>> (or any code equivalent with libcryptsetup), am I correct?
>
> Correct me if I'm wrong, but I don't think there will be a safer way to
> preserve key without patching cryptsetup. Actually the --dump-volume-key
> approach has been proposed before and I agree with your conclusion [1]
> on that approach i.e. "passing volume key this way is quite insecure".
> Without patching cryptsetup, even if I save the volume key in the memory
> reserved for the kdump kernel, I need to retrieve this key in the
> userspace to unlock the LUKS device which may lead to quite a security
> vulnerability.
Hm, where are the patches for cryptsetup, then? I am afraid we do not want
to add such specific things there.
But we are just going to merge a patchset that changes how we use keyring
where you can tell cryptsetup to store/link key under some specific name
and to specific keyring
(see https://gitlab.com/cryptsetup/cryptsetup/-/merge_requests/492)
(Please talk to Red Hat cryptsetup maintainers for more info,
I just mentioned this mail to them today.)
> I respect the efforts from you and the cryptsetup community to make LUKS
> as secure as possible. And kdump is used in product environment. Kdump
> is to a server as a black box is to an aircraft. So by no means I want
> to reverse the used security measures and patching cryptsetup can allow
> to keep the security measures. One concern raised by you against "FRC
> v1" was a copy of the LUKS volume key for the kdump kernel creates an
> attack vector. I took this feedback seriously and have sought advice
> from my colleagues to implement the countermeasures ([PATCH 1/5] and
> [Patch 4/5]).
>
> [1] https://yhbt.net/lore/all/e5abd089-3398-fdb4-7991-0019be434b79@gmail.com/
Yes, I appreciate that. And it is perfectly ok if your customers accept
the trade-off and security risk of handling the key this way.
Anyway, I feel we are going in circles here, and as it seems to be my fault,
I do not want to sound grumpy as I am perhaps missing some context.
Could you please talk to internal RH cryptsetup maintainers first and discuss
your solution? They know what we can do here can help to find an acceptable
solution. (I added cc to Ondra.)
Thanks,
Milan
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^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [dm-devel] [PATCH 0/5] Support kdump with LUKS encryption by reusing LUKS volume key
2023-06-08 10:39 ` Milan Broz
@ 2023-06-09 9:58 ` Coiby Xu
0 siblings, 0 replies; 15+ messages in thread
From: Coiby Xu @ 2023-06-09 9:58 UTC (permalink / raw)
To: Milan Broz
Cc: Baoquan He, Kairui Song, x86, kexec, linux-kernel, Pingfan Liu,
Eric Biggers, Dave Hansen, dm-devel, Jan Pazdziora, Thomas Staudt,
Ondrej Kozina, Vitaly Kuznetsov, Dave Young
On Thu, Jun 08, 2023 at 12:39:26PM +0200, Milan Broz wrote:
>On 6/7/23 14:39, Coiby Xu wrote:
>...
>>>I do not think you need any cryptsetup patches, all you need is to write
>>>decrypted volume key from LUKS metadata with
>>> cryptsetup luksDump ---dump-volume-key -volume-key-file <out> <device>
>>>(or any code equivalent with libcryptsetup), am I correct?
>>
>>Correct me if I'm wrong, but I don't think there will be a safer way to
>>preserve key without patching cryptsetup. Actually the --dump-volume-key
>>approach has been proposed before and I agree with your conclusion [1]
>>on that approach i.e. "passing volume key this way is quite insecure".
>>Without patching cryptsetup, even if I save the volume key in the memory
>>reserved for the kdump kernel, I need to retrieve this key in the
>>userspace to unlock the LUKS device which may lead to quite a security
>>vulnerability.
>
>Hm, where are the patches for cryptsetup, then? I am afraid we do not want
>to add such specific things there.
Thanks for cleaning up the text to make the discussion easier! Sorry I
only mentioned it [3] in the cover letter and didn't provide one in
previous reply. [3] was done in a quick-and-dirty way (I plan to send a
formal merge request after finishing the kernel part) and there is no need
to read it. Let's me explain what [3] does here instead,
1) After unlocking the LUKS-encrypted device, if cryptsetup finds
/sys/kernel/crash_luks_volume_key exists, it will write the key
description of the volume key to it to notify the kernel to save a copy
of this logon key linked to its thread keyring for the kdump kernel
2) After the 1st kernel crashes, if crytpsetup finds it's in the kdump
kernel, instead of deriving the volume key from a passphrase, it
will write the key description to /sys/kernel/crash_luks_volume_key
to ask the kdump kernel to link the saved key to its thread keyring.
[3] https://gitlab.com/coxu/cryptsetup/-/commit/750a46d933fac82e0c994b5c41de40a0b8cac647
>
>But we are just going to merge a patchset that changes how we use keyring
>where you can tell cryptsetup to store/link key under some specific name
>and to specific keyring
>(see https://gitlab.com/cryptsetup/cryptsetup/-/merge_requests/492)
>(Please talk to Red Hat cryptsetup maintainers for more info,
>I just mentioned this mail to them today.)
Thanks for pointing me to the above MR which looks promising! Unlike
treating the kdump use case as a special case [3], it just provides a
generic way with the implemented options --link-vk-to-keyring and
--volume-key-keyring.
>
>>I respect the efforts from you and the cryptsetup community to make LUKS
>>as secure as possible. And kdump is used in product environment. Kdump
>>is to a server as a black box is to an aircraft. So by no means I want
>>to reverse the used security measures and patching cryptsetup can allow
>>to keep the security measures. One concern raised by you against "FRC
>>v1" was a copy of the LUKS volume key for the kdump kernel creates an
>>attack vector. I took this feedback seriously and have sought advice
>>from my colleagues to implement the countermeasures ([PATCH 1/5] and
>>[Patch 4/5]).
>>
>>[1] https://yhbt.net/lore/all/e5abd089-3398-fdb4-7991-0019be434b79@gmail.com/
>
>Yes, I appreciate that. And it is perfectly ok if your customers accept
>the trade-off and security risk of handling the key this way.
>
>Anyway, I feel we are going in circles here, and as it seems to be my fault,
>I do not want to sound grumpy as I am perhaps missing some context.
Actually I should thank you for your patience! You have been always
offering your feedback on this work kindly and promptly starting with
the first proposed solution [1].
>
>Could you please talk to internal RH cryptsetup maintainers first and discuss
>your solution? They know what we can do here can help to find an acceptable
>solution. (I added cc to Ondra.)
Sure, I'll talk to them first. Thanks for letting Ondra know!
>
>Thanks,
>Milan
>
--
Best regards,
Coiby
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^ permalink raw reply [flat|nested] 15+ messages in thread