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@xxxxxxxxxx>
---
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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