From c28d32f946f0d1c0780a02ab49dc2c1835370501 Mon Sep 17 00:00:00 2001 From: Ilias Apalodimas Date: Thu, 18 Apr 2024 15:54:50 +0300 Subject: efi_loader: conditionally enable SetvariableRT When we store EFI variables on file we don't allow SetVariable at runtime, since the OS doesn't know how to access or write that file. At the same time keeping the U-Boot drivers alive in runtime sections and performing writes from the firmware is dangerous -- if at all possible. For GetVariable at runtime we copy runtime variables in RAM and expose them to the OS. Add a Kconfig option and provide SetVariable at runtime using the same memory backend. The OS will be responsible for syncing the RAM contents to the file, otherwise any changes made during runtime won't persist reboots. It's worth noting that the variable store format is defined in EBBR [0] and authenticated variables are explicitly prohibited, since they have to be stored on a medium that's tamper and rollback protected. - pre-patch $~ mount | grep efiva efivarfs on /sys/firmware/efi/efivars type efivarfs (ro,nosuid,nodev,noexec,relatime) $~ efibootmgr -n 0001 Could not set BootNext: Read-only file system - post-patch $~ mount | grep efiva efivarfs on /sys/firmware/efi/efivars type efivarfs (rw,nosuid,nodev,noexec,relatime) $~ efibootmgr -n 0001 BootNext: 0001 BootCurrent: 0000 BootOrder: 0000,0001 Boot0000* debian HD(1,GPT,bdae5610-3331-4e4d-9466-acb5caf0b4a6,0x800,0x100000)/File(EFI\debian\grubaa64.efi) Boot0001* virtio 0 VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b,0000000000000000)/VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b,850000001f000000)/VenHw(e61d73b9-a384-4acc-aeab-82e828f3628b,1600850000000000){auto_created_boot_option} $~ efivar -p -n 8be4df61-93ca-11d2-aa0d-00e098032b8c-BootNext GUID: 8be4df61-93ca-11d2-aa0d-00e098032b8c Name: "BootNext" Attributes: Non-Volatile Boot Service Access Runtime Service Access Value: 00000000 01 00 FWTS runtime results Skipped tests are for SetVariable which is now supported 'Passed' test is for QueryVariableInfo which is not yet supported Test: UEFI miscellaneous runtime service interface tests. Test for UEFI miscellaneous runtime service interfaces 6 skipped Stress test for UEFI miscellaneous runtime service i.. 1 skipped Test GetNextHighMonotonicCount with invalid NULL par.. 1 skipped Test UEFI miscellaneous runtime services unsupported.. 1 passed Test: UEFI Runtime service variable interface tests. Test UEFI RT service get variable interface. 1 passed Test UEFI RT service get next variable name interface. 4 passed Test UEFI RT service set variable interface. 8 passed Test UEFI RT service query variable info interface. 1 skipped Test UEFI RT service variable interface stress test. 2 passed Test UEFI RT service set variable interface stress t.. 4 passed Test UEFI RT service query variable info interface s.. 1 skipped Test UEFI RT service get variable interface, invalid.. 5 passed Test UEFI RT variable services unsupported status. 1 passed, 3 skipped [0] https://arm-software.github.io/ebbr/index.html#document-chapter5-variable-storage Reviewed-by: Heinrich Schuchardt Signed-off-by: Ilias Apalodimas --- lib/efi_loader/efi_variable.c | 116 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 105 insertions(+), 11 deletions(-) (limited to 'lib/efi_loader/efi_variable.c') diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c index e6c1219a11c..47bb7992057 100644 --- a/lib/efi_loader/efi_variable.c +++ b/lib/efi_loader/efi_variable.c @@ -219,17 +219,20 @@ efi_get_next_variable_name_int(efi_uintn_t *variable_name_size, return efi_get_next_variable_name_mem(variable_name_size, variable_name, vendor); } -efi_status_t efi_set_variable_int(const u16 *variable_name, - const efi_guid_t *vendor, - u32 attributes, efi_uintn_t data_size, - const void *data, bool ro_check) +/** + * setvariable_allowed() - checks defined by the UEFI spec for setvariable + * + * @variable_name: name of the variable + * @vendor: vendor GUID + * @attributes: attributes of the variable + * @data_size: size of the buffer with the variable value + * @data: buffer with the variable value + * Return: status code + */ +static efi_status_t __efi_runtime +setvariable_allowed(const u16 *variable_name, const efi_guid_t *vendor, + u32 attributes, efi_uintn_t data_size, const void *data) { - struct efi_var_entry *var; - efi_uintn_t ret; - bool append, delete; - u64 time = 0; - enum efi_auth_var_type var_type; - if (!variable_name || !*variable_name || !vendor) return EFI_INVALID_PARAMETER; @@ -261,6 +264,25 @@ efi_status_t efi_set_variable_int(const u16 *variable_name, !(attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS))) return EFI_INVALID_PARAMETER; + return EFI_SUCCESS; +} + +efi_status_t efi_set_variable_int(const u16 *variable_name, + const efi_guid_t *vendor, + u32 attributes, efi_uintn_t data_size, + const void *data, bool ro_check) +{ + struct efi_var_entry *var; + efi_uintn_t ret; + bool append, delete; + u64 time = 0; + enum efi_auth_var_type var_type; + + ret = setvariable_allowed(variable_name, vendor, attributes, data_size, + data); + if (ret != EFI_SUCCESS) + return ret; + /* check if a variable exists */ var = efi_var_mem_find(vendor, variable_name, NULL); append = !!(attributes & EFI_VARIABLE_APPEND_WRITE); @@ -454,7 +476,79 @@ efi_set_variable_runtime(u16 *variable_name, const efi_guid_t *vendor, u32 attributes, efi_uintn_t data_size, const void *data) { - return EFI_UNSUPPORTED; + struct efi_var_entry *var; + efi_uintn_t ret; + bool append, delete; + u64 time = 0; + + if (!IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE)) + return EFI_UNSUPPORTED; + + /* + * Authenticated variables are not supported. The EFI spec + * in ยง32.3.6 requires keys to be stored in non-volatile storage which + * is tamper and delete resistant. + * The rest of the checks are in setvariable_allowed() + */ + if (attributes & EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS) + return EFI_INVALID_PARAMETER; + + ret = setvariable_allowed(variable_name, vendor, attributes, data_size, + data); + if (ret != EFI_SUCCESS) + return ret; + + /* check if a variable exists */ + var = efi_var_mem_find(vendor, variable_name, NULL); + append = !!(attributes & EFI_VARIABLE_APPEND_WRITE); + attributes &= ~EFI_VARIABLE_APPEND_WRITE; + delete = !append && (!data_size || !attributes); + + /* BS only variables are hidden deny writing them */ + if (!delete && !(attributes & EFI_VARIABLE_RUNTIME_ACCESS)) + return EFI_INVALID_PARAMETER; + + if (var) { + if (var->attr & EFI_VARIABLE_READ_ONLY || + !(var->attr & EFI_VARIABLE_NON_VOLATILE)) + return EFI_WRITE_PROTECTED; + + /* attributes won't be changed */ + if (!delete && (((var->attr & ~EFI_VARIABLE_READ_ONLY) != + (attributes & ~EFI_VARIABLE_READ_ONLY)))) + return EFI_INVALID_PARAMETER; + time = var->time; + } else { + if (!(attributes & EFI_VARIABLE_NON_VOLATILE)) + return EFI_INVALID_PARAMETER; + if (append && !data_size) + return EFI_SUCCESS; + if (delete) + return EFI_NOT_FOUND; + } + + if (delete) { + /* EFI_NOT_FOUND has been handled before */ + attributes = var->attr; + ret = EFI_SUCCESS; + } else if (append && var) { + u16 *old_data = (void *)((uintptr_t)var->name + + sizeof(u16) * (u16_strlen(var->name) + 1)); + + ret = efi_var_mem_ins(variable_name, vendor, attributes, + var->length, old_data, data_size, data, + time); + } else { + ret = efi_var_mem_ins(variable_name, vendor, attributes, + data_size, data, 0, NULL, time); + } + + if (ret != EFI_SUCCESS) + return ret; + /* We are always inserting new variables, get rid of the old copy */ + efi_var_mem_del(var); + + return EFI_SUCCESS; } /** -- cgit v1.2.3 From 00da8d65a3baea8c3745367bea99b1d76f8f129c Mon Sep 17 00:00:00 2001 From: Ilias Apalodimas Date: Thu, 18 Apr 2024 15:54:52 +0300 Subject: efi_loader: add an EFI variable with the file contents Previous patches enabled SetVariableRT using a RAM backend. Although EBBR [0] defines a variable format we can teach userspace tools and write the altered variables, it's better if we skip the ABI requirements completely. So let's add a new variable, in its own namespace called "VarToFile" which contains a binary dump of the updated RT, BS and, NV variables and will be updated when GetVariable is called. Some adjustments are needed to do that. Currently we discard BS-only variables in EBS(). We need to preserve those on the RAM backend that exposes the variables. Since BS-only variables can't appear at runtime we need to move the memory masking checks from efi_var_collect() to efi_get_next_variable_name_mem()/ efi_get_variable_mem() and do the filtering at runtime. We also need an efi_var_collect() variant available at runtime, in order to construct the "VarToFile" buffer on the fly. All users and applications (for linux) have to do when updating a variable is dd that variable in the file described by "RTStorageVolatile". Linux efivarfs uses a first 4 bytes of the output to represent attributes in little-endian format. So, storing variables works like this: $~ efibootmgr -n 0001 $~ dd if=/sys/firmware/efi/efivars/VarToFile-b2ac5fc9-92b7-4acd-aeac-11e818c3130c of=/boot/efi/ubootefi.var skip=4 bs=1 [0] https://arm-software.github.io/ebbr/index.html#document-chapter5-variable-storage Suggested-by: Ard Biesheuvel # dumping all variables to a variable Co-developed-by: Heinrich Schuchardt # contributed on efi_var_collect_mem() Signed-off-by: Heinrich Schuchardt Signed-off-by: Ilias Apalodimas --- lib/efi_loader/efi_variable.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'lib/efi_loader/efi_variable.c') diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c index 47bb7992057..0cbed53d1db 100644 --- a/lib/efi_loader/efi_variable.c +++ b/lib/efi_loader/efi_variable.c @@ -209,14 +209,16 @@ efi_get_variable_int(const u16 *variable_name, const efi_guid_t *vendor, u32 *attributes, efi_uintn_t *data_size, void *data, u64 *timep) { - return efi_get_variable_mem(variable_name, vendor, attributes, data_size, data, timep); + return efi_get_variable_mem(variable_name, vendor, attributes, data_size, + data, timep, 0); } efi_status_t __efi_runtime efi_get_next_variable_name_int(efi_uintn_t *variable_name_size, u16 *variable_name, efi_guid_t *vendor) { - return efi_get_next_variable_name_mem(variable_name_size, variable_name, vendor); + return efi_get_next_variable_name_mem(variable_name_size, variable_name, + vendor, 0); } /** -- cgit v1.2.3