Implement variable policies (Edk2VariablePolicyProtocol). This EFI protocol allows to define restrictions for variables. It also allows to lock down variables (disallow write access).
Signed-off-by: Gerd Hoffmann <kra...@redhat.com> --- hw/uefi/var-service-policy.c | 370 +++++++++++++++++++++++++++++++++++ 1 file changed, 370 insertions(+) create mode 100644 hw/uefi/var-service-policy.c diff --git a/hw/uefi/var-service-policy.c b/hw/uefi/var-service-policy.c new file mode 100644 index 000000000000..3b1155fe4ea1 --- /dev/null +++ b/hw/uefi/var-service-policy.c @@ -0,0 +1,370 @@ +/* + * SPDX-License-Identifier: GPL-2.0-or-later + * + * uefi vars device - VarCheckPolicyLibMmiHandler implementation + * + * variable policy specs: + * https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Library/VariablePolicyLib/ReadMe.md + */ +#include "qemu/osdep.h" +#include "system/dma.h" +#include "migration/vmstate.h" + +#include "hw/uefi/var-service.h" +#include "hw/uefi/var-service-api.h" +#include "hw/uefi/var-service-edk2.h" + +#include "trace/trace-hw_uefi.h" + +static void calc_policy(uefi_var_policy *pol); + +static int uefi_var_policy_post_load(void *opaque, int version_id) +{ + uefi_var_policy *pol = opaque; + + calc_policy(pol); + return 0; +} + +const VMStateDescription vmstate_uefi_var_policy = { + .name = "uefi-var-policy", + .post_load = uefi_var_policy_post_load, + .fields = (VMStateField[]) { + VMSTATE_UINT32(entry_size, uefi_var_policy), + VMSTATE_VBUFFER_ALLOC_UINT32(entry, uefi_var_policy, + 0, NULL, entry_size), + VMSTATE_END_OF_LIST() + }, +}; + +static void print_policy_entry(variable_policy_entry *pe) +{ + uint16_t *name = (void *)pe + pe->offset_to_name; + + fprintf(stderr, "%s:\n", __func__); + + fprintf(stderr, " name ยด"); + while (*name) { + fprintf(stderr, "%c", *name); + name++; + } + fprintf(stderr, "', version=%d.%d, size=%d\n", + pe->version >> 16, pe->version & 0xffff, pe->size); + + if (pe->min_size) { + fprintf(stderr, " size min=%d\n", pe->min_size); + } + if (pe->max_size != UINT32_MAX) { + fprintf(stderr, " size max=%u\n", pe->max_size); + } + if (pe->attributes_must_have) { + fprintf(stderr, " attr must=0x%x\n", pe->attributes_must_have); + } + if (pe->attributes_cant_have) { + fprintf(stderr, " attr cant=0x%x\n", pe->attributes_cant_have); + } + if (pe->lock_policy_type) { + fprintf(stderr, " lock policy type %d\n", pe->lock_policy_type); + } +} + +static gboolean wildcard_str_equal(uefi_var_policy *pol, + uefi_variable *var) +{ + return uefi_str_equal_ex(pol->name, pol->name_size, + var->name, var->name_size, + true); +} + +static uefi_var_policy *find_policy(uefi_vars_state *uv, QemuUUID guid, + uint16_t *name, uint64_t name_size) +{ + uefi_var_policy *pol; + + QTAILQ_FOREACH(pol, &uv->var_policies, next) { + if (!qemu_uuid_is_equal(&pol->entry->namespace, &guid)) { + continue; + } + if (!uefi_str_equal(pol->name, pol->name_size, + name, name_size)) { + continue; + } + return pol; + } + return NULL; +} + +static uefi_var_policy *wildcard_find_policy(uefi_vars_state *uv, + uefi_variable *var) +{ + uefi_var_policy *pol; + + QTAILQ_FOREACH(pol, &uv->var_policies, next) { + if (!qemu_uuid_is_equal(&pol->entry->namespace, &var->guid)) { + continue; + } + if (!wildcard_str_equal(pol, var)) { + continue; + } + return pol; + } + return NULL; +} + +static void calc_policy(uefi_var_policy *pol) +{ + variable_policy_entry *pe = pol->entry; + unsigned int i; + + pol->name = (void *)pol->entry + pe->offset_to_name; + pol->name_size = pe->size - pe->offset_to_name; + + for (i = 0; i < pol->name_size / 2; i++) { + if (pol->name[i] == '#') { + pol->hashmarks++; + } + } +} + +uefi_var_policy *uefi_vars_add_policy(uefi_vars_state *uv, + variable_policy_entry *pe) +{ + uefi_var_policy *pol, *p; + + pol = g_new0(uefi_var_policy, 1); + pol->entry = g_malloc(pe->size); + memcpy(pol->entry, pe, pe->size); + pol->entry_size = pe->size; + + calc_policy(pol); + + /* keep list sorted by priority, add to tail of priority group */ + QTAILQ_FOREACH(p, &uv->var_policies, next) { + if ((p->hashmarks > pol->hashmarks) || + (!p->name_size && pol->name_size)) { + QTAILQ_INSERT_BEFORE(p, pol, next); + return pol; + } + } + + QTAILQ_INSERT_TAIL(&uv->var_policies, pol, next); + return pol; +} + +efi_status uefi_vars_policy_check(uefi_vars_state *uv, + uefi_variable *var, + gboolean is_newvar) +{ + uefi_var_policy *pol; + variable_policy_entry *pe; + variable_lock_on_var_state *lvarstate; + uint16_t *lvarname; + size_t lvarnamesize; + uefi_variable *lvar; + + if (!uv->end_of_dxe) { + return EFI_SUCCESS; + } + + pol = wildcard_find_policy(uv, var); + if (!pol) { + return EFI_SUCCESS; + } + pe = pol->entry; + + uefi_trace_variable(__func__, var->guid, var->name, var->name_size); + print_policy_entry(pe); + + if ((var->attributes & pe->attributes_must_have) != pe->attributes_must_have) { + trace_uefi_vars_policy_deny("must-have-attr"); + return EFI_INVALID_PARAMETER; + } + if ((var->attributes & pe->attributes_cant_have) != 0) { + trace_uefi_vars_policy_deny("cant-have-attr"); + return EFI_INVALID_PARAMETER; + } + + if (var->data_size < pe->min_size) { + trace_uefi_vars_policy_deny("min-size"); + return EFI_INVALID_PARAMETER; + } + if (var->data_size > pe->max_size) { + trace_uefi_vars_policy_deny("max-size"); + return EFI_INVALID_PARAMETER; + } + + switch (pe->lock_policy_type) { + case VARIABLE_POLICY_TYPE_NO_LOCK: + break; + + case VARIABLE_POLICY_TYPE_LOCK_NOW: + trace_uefi_vars_policy_deny("lock-now"); + return EFI_WRITE_PROTECTED; + + case VARIABLE_POLICY_TYPE_LOCK_ON_CREATE: + if (!is_newvar) { + trace_uefi_vars_policy_deny("lock-on-create"); + return EFI_WRITE_PROTECTED; + } + break; + + case VARIABLE_POLICY_TYPE_LOCK_ON_VAR_STATE: + lvarstate = (void *)pol->entry + sizeof(*pe); + lvarname = (void *)pol->entry + sizeof(*pe) + sizeof(*lvarstate); + lvarnamesize = pe->offset_to_name - sizeof(*pe) - sizeof(*lvarstate); + + uefi_trace_variable(__func__, lvarstate->namespace, + lvarname, lvarnamesize); + lvar = uefi_vars_find_variable(uv, lvarstate->namespace, + lvarname, lvarnamesize); + if (lvar && lvar->data_size == 1) { + uint8_t *value = lvar->data; + if (lvarstate->value == *value) { + return EFI_WRITE_PROTECTED; + } + } + break; + } + + return EFI_SUCCESS; +} + +void uefi_vars_policies_clear(uefi_vars_state *uv) +{ + uefi_var_policy *pol; + + while (!QTAILQ_EMPTY(&uv->var_policies)) { + pol = QTAILQ_FIRST(&uv->var_policies); + QTAILQ_REMOVE(&uv->var_policies, pol, next); + g_free(pol->entry); + g_free(pol); + } +} + +static size_t uefi_vars_mm_policy_error(mm_header *mhdr, + mm_check_policy *mchk, + uint64_t status) +{ + mchk->result = status; + return sizeof(*mchk); +} + +static uint32_t uefi_vars_mm_check_policy_is_enabled(uefi_vars_state *uv, + mm_header *mhdr, + mm_check_policy *mchk, + void *func) +{ + mm_check_policy_is_enabled *mpar = func; + size_t length; + + length = sizeof(*mchk) + sizeof(*mpar); + if (mhdr->length < length) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_BAD_BUFFER_SIZE); + } + + mpar->state = TRUE; + mchk->result = EFI_SUCCESS; + return sizeof(*mchk); +} + +static uint32_t uefi_vars_mm_check_policy_register(uefi_vars_state *uv, + mm_header *mhdr, + mm_check_policy *mchk, + void *func) +{ + variable_policy_entry *pe = func; + uefi_var_policy *pol; + uint64_t length; + + if (uadd64_overflow(sizeof(*mchk), pe->size, &length)) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_BAD_BUFFER_SIZE); + } + if (mhdr->length < length) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_BAD_BUFFER_SIZE); + } + if (pe->size < sizeof(*pe)) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_BAD_BUFFER_SIZE); + } + if (pe->offset_to_name < sizeof(*pe)) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_BAD_BUFFER_SIZE); + } + + if (pe->lock_policy_type == VARIABLE_POLICY_TYPE_LOCK_ON_VAR_STATE && + pe->offset_to_name < sizeof(*pe) + sizeof(variable_lock_on_var_state)) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_BAD_BUFFER_SIZE); + } + + /* check space for minimum string length */ + if (pe->size < (size_t)pe->offset_to_name) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_BAD_BUFFER_SIZE); + } + + if (!uefi_str_is_valid((void *)pe + pe->offset_to_name, + pe->size - pe->offset_to_name, + false)) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_INVALID_PARAMETER); + } + + pol = find_policy(uv, pe->namespace, + (void *)pe + pe->offset_to_name, + pe->size - pe->offset_to_name); + if (pol) { + return uefi_vars_mm_policy_error(mhdr, mchk, EFI_ALREADY_STARTED); + } + + uefi_vars_add_policy(uv, pe); + + mchk->result = EFI_SUCCESS; + return sizeof(*mchk); +} + +uint32_t uefi_vars_mm_check_policy_proto(uefi_vars_state *uv) +{ + static const char *fnames[] = { + "zero", + "disable", + "is-enabled", + "register", + "dump", + "lock", + }; + const char *fname; + mm_header *mhdr = (mm_header *) uv->buffer; + mm_check_policy *mchk = (mm_check_policy *) (uv->buffer + sizeof(*mhdr)); + void *func = (uv->buffer + sizeof(*mhdr) + sizeof(*mchk)); + + if (mhdr->length < sizeof(*mchk)) { + return UEFI_VARS_STS_ERR_BAD_BUFFER_SIZE; + } + + fname = mchk->command < ARRAY_SIZE(fnames) + ? fnames[mchk->command] + : "unknown"; + trace_uefi_vars_policy_cmd(fname); + + switch (mchk->command) { + case VAR_CHECK_POLICY_COMMAND_DISABLE: + mchk->result = EFI_UNSUPPORTED; + break; + case VAR_CHECK_POLICY_COMMAND_IS_ENABLED: + uefi_vars_mm_check_policy_is_enabled(uv, mhdr, mchk, func); + break; + case VAR_CHECK_POLICY_COMMAND_REGISTER: + if (uv->policy_locked) { + mchk->result = EFI_WRITE_PROTECTED; + } else { + uefi_vars_mm_check_policy_register(uv, mhdr, mchk, func); + } + break; + case VAR_CHECK_POLICY_COMMAND_LOCK: + uv->policy_locked = true; + mchk->result = EFI_SUCCESS; + break; + default: + mchk->result = EFI_UNSUPPORTED; + break; + } + + uefi_trace_status(__func__, mchk->result); + return UEFI_VARS_STS_SUCCESS; +} -- 2.48.1
