@@ -78,6 +78,21 @@ config SNAPSHOT_VERIFICATION
dependent on UEFI environment. EFI bootloader should generate the
key-pair.
+config SNAPSHOT_REGEN_KEYS
+ bool "Regenerate key-pair for each snapshot verification"
+ depends on SNAPSHOT_VERIFICATION
+ help
+ Enabled this option let kernel notify booloader (e.g. shim) to
+ regenerate key-pair of snapshot verification for each hibernate.
+ Linux kernel write an non-volatile runtime EFI variable, the name
+ is GenS4Key-fe141863-c070-478e-b8a3-878a5dc9ef21, to notify EFI
+ bootloader regenerate key-pair for next hibernate cycle.
+
+ Userland hibernate tool can write GenS4Key at runtime then kernel
+ will respect the value but not overwrite it when S4. This mechanism
+ let userland tool can also notify bootloader to regenerate key-pair
+ through GenS4Key flag.
+
choice
prompt "Which hash algorithm should snapshot be signed with?"
depends on SNAPSHOT_VERIFICATION
@@ -7,6 +7,8 @@
#include "power.h"
+static efi_char16_t efi_gens4key_name[9] = { 'G', 'e', 'n', 'S', '4', 'K', 'e', 'y', 0 };
+
static void *skey_data;
static void *skey_data_buf;
static unsigned long skey_dsize;
@@ -273,6 +275,42 @@ size_t get_key_length(const struct key *key)
return len;
}
+void set_key_regen_flag(void)
+{
+#ifdef CONFIG_SNAPSHOT_REGEN_KEYS
+ unsigned long datasize;
+ u8 gens4key;
+ efi_status_t status;
+
+ /* existing flag may set by userland, respect but not overwrite it */
+ datasize = 0;
+ status = efi.get_variable(efi_gens4key_name, &EFI_HIBERNATE_GUID,
+ NULL, &datasize, NULL);
+ if (status == EFI_BUFFER_TOO_SMALL)
+ return;
+
+ /* set flag of key-pair regeneration */
+ gens4key = 1;
+ status = efi.set_variable(efi_gens4key_name, &EFI_HIBERNATE_GUID,
+ EFI_VARIABLE_NON_VOLATILE |
+ EFI_VARIABLE_BOOTSERVICE_ACCESS |
+ EFI_VARIABLE_RUNTIME_ACCESS,
+ 1, (void *)&gens4key);
+ if (status)
+ pr_err("PM: Set GenS4Key flag fail: 0x%lx\n", status);
+#endif
+}
+
+static void clean_key_regen_flag(void)
+{
+ /* clean flag of key-pair regeneration */
+ efi.set_variable(efi_gens4key_name, &EFI_HIBERNATE_GUID,
+ EFI_VARIABLE_NON_VOLATILE |
+ EFI_VARIABLE_BOOTSERVICE_ACCESS |
+ EFI_VARIABLE_RUNTIME_ACCESS,
+ 0, NULL);
+}
+
static int __init init_sign_key_data(void)
{
skey_data = (void *)get_zeroed_page(GFP_KERNEL);
@@ -283,6 +321,7 @@ static int __init init_sign_key_data(void)
efi_erase_s4_skey_data();
pr_info("PM: Load s4 sign key from EFI\n");
}
+ clean_key_regen_flag();
return 0;
}
@@ -181,6 +181,7 @@ extern void restore_sign_key_data(void);
extern bool swsusp_page_is_sign_key(struct page *page);
extern unsigned long get_skey_data_buf_pfn(void);
extern void clone_skey_data(void *page_addr);
+extern void set_key_regen_flag(void);
#else /* !CONFIG_SUSPEND */
static inline void restore_sign_key_data(void) {}
static inline bool swsusp_page_is_sign_key(struct page *page)
@@ -191,6 +192,7 @@ static inline unsigned long get_skey_data_buf_pfn(void)
{
return 0;
}
+static inline void set_key_regen_flag(void) {}
#endif /* !CONFIG_SNAPSHOT_VERIFICATION */
/* kernel/power/block_io.c */
@@ -1769,6 +1769,9 @@ asmlinkage int swsusp_save(void)
printk(KERN_INFO "PM: Hibernation image created (%d pages copied)\n",
nr_pages);
+ /* set regenerate key flag */
+ set_key_regen_flag();
+
return 0;
}
This patch introduced SNAPSHOT_REGEN_KEYS kernel config, enable this option let kernel notify booloader (e.g. shim) to regenerate key-pair of snapshot verification for each hibernate. Kernel loaded S4 sign key in efi stub, so the private key forward from efi bootloader to kernel in UEFI secure environment. Regenerate key-pair for each hibernate will gain more security but it hurt the lifetime of EFI flash memory. Kernel write an non-volatile runtime efi variable, the name is GenS4Key-fe141863-c070-478e-b8a3-878a5dc9ef21, to notify efi bootloader regenerate key-pair for next hibernate cycle. Userland hibernate tool can write GenS4Key at runtime, kernel will respect the value but not overwrite it when S4. This mechanism let userland tool can also notify bootloader to regenerate key-pair through GenS4Key flag. Cc: Matthew Garrett <mjg59@srcf.ucam.org> Signed-off-by: Lee, Chun-Yi <jlee@suse.com> --- kernel/power/Kconfig | 15 +++++++++++++++ kernel/power/hibernate_keys.c | 39 +++++++++++++++++++++++++++++++++++++++ kernel/power/power.h | 2 ++ kernel/power/snapshot.c | 3 +++ 4 files changed, 59 insertions(+), 0 deletions(-)