[PATCH v4 08/24] hw/uefi: add var-service-auth.c

[Gerd Hoffmann <kraxel@redhat.com>]

This implements authenticated variable handling (see AuthVariableLib in
edk2).

The by far most common use case for auth variables is secure boot.  The
secure boot certificate databases ('PK', 'KEK', 'db' and 'dbx') are
authenticated variables, with update rules being specified in the UEFI
specification.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/uefi/var-service-auth.c | 361 +++++++++++++++++++++++++++++++++++++
 1 file changed, 361 insertions(+)
 create mode 100644 hw/uefi/var-service-auth.c

diff --git a/hw/uefi/var-service-auth.c b/hw/uefi/var-service-auth.c
new file mode 100644
index 000000000000..fba5a0956a57
--- /dev/null
+++ b/hw/uefi/var-service-auth.c
@@ -0,0 +1,361 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * uefi vars device - AuthVariableLib
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "system/dma.h"
+
+#include "hw/uefi/var-service.h"
+
+static const uint16_t name_pk[]           = u"PK";
+static const uint16_t name_kek[]          = u"KEK";
+static const uint16_t name_db[]           = u"db";
+static const uint16_t name_dbx[]          = u"dbx";
+static const uint16_t name_setup_mode[]   = u"SetupMode";
+static const uint16_t name_sigs_support[] = u"SignatureSupport";
+static const uint16_t name_sb[]           = u"SecureBoot";
+static const uint16_t name_sb_enable[]    = u"SecureBootEnable";
+static const uint16_t name_custom_mode[]  = u"CustomMode";
+static const uint16_t name_vk[]           = u"VendorKeys";
+static const uint16_t name_vk_nv[]        = u"VendorKeysNv";
+
+static const uint32_t sigdb_attrs =
+    EFI_VARIABLE_NON_VOLATILE |
+    EFI_VARIABLE_BOOTSERVICE_ACCESS |
+    EFI_VARIABLE_RUNTIME_ACCESS |
+    EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS;
+
+static void set_secure_boot(uefi_vars_state *uv, uint8_t sb)
+{
+    uefi_vars_set_variable(uv, EfiGlobalVariable,
+                           name_sb, sizeof(name_sb),
+                           EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                           EFI_VARIABLE_RUNTIME_ACCESS,
+                           &sb, sizeof(sb));
+}
+
+static void set_secure_boot_enable(uefi_vars_state *uv, uint8_t sbe)
+{
+    uefi_vars_set_variable(uv, EfiSecureBootEnableDisable,
+                           name_sb_enable, sizeof(name_sb_enable),
+                           EFI_VARIABLE_NON_VOLATILE |
+                           EFI_VARIABLE_BOOTSERVICE_ACCESS,
+                           &sbe, sizeof(sbe));
+}
+
+static void set_setup_mode(uefi_vars_state *uv, uint8_t sm)
+{
+    uefi_vars_set_variable(uv, EfiGlobalVariable,
+                           name_setup_mode, sizeof(name_setup_mode),
+                           EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                           EFI_VARIABLE_RUNTIME_ACCESS,
+                           &sm, sizeof(sm));
+}
+
+static void set_custom_mode(uefi_vars_state *uv, uint8_t cm)
+{
+    uefi_vars_set_variable(uv, EfiCustomModeEnable,
+                           name_custom_mode, sizeof(name_custom_mode),
+                           EFI_VARIABLE_NON_VOLATILE |
+                           EFI_VARIABLE_BOOTSERVICE_ACCESS,
+                           &cm, sizeof(cm));
+}
+
+static void set_signature_support(uefi_vars_state *uv)
+{
+    QemuUUID sigs_support[5];
+
+    sigs_support[0] = EfiCertSha256Guid;
+    sigs_support[1] = EfiCertSha384Guid;
+    sigs_support[2] = EfiCertSha512Guid;
+    sigs_support[3] = EfiCertRsa2048Guid;
+    sigs_support[4] = EfiCertX509Guid;
+
+    uefi_vars_set_variable(uv, EfiGlobalVariable,
+                           name_sigs_support, sizeof(name_sigs_support),
+                           EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                           EFI_VARIABLE_RUNTIME_ACCESS,
+                           sigs_support, sizeof(sigs_support));
+}
+
+static bool setup_mode_is_active(uefi_vars_state *uv)
+{
+    uefi_variable *var;
+    uint8_t *value;
+
+    var = uefi_vars_find_variable(uv, EfiGlobalVariable,
+                                  name_setup_mode, sizeof(name_setup_mode));
+    if (var) {
+        value = var->data;
+        if (value[0] == SETUP_MODE) {
+            return true;
+        }
+    }
+    return false;
+}
+
+static bool custom_mode_is_active(uefi_vars_state *uv)
+{
+    uefi_variable *var;
+    uint8_t *value;
+
+    var = uefi_vars_find_variable(uv, EfiCustomModeEnable,
+                                  name_custom_mode, sizeof(name_custom_mode));
+    if (var) {
+        value = var->data;
+        if (value[0] == CUSTOM_SECURE_BOOT_MODE) {
+            return true;
+        }
+    }
+    return false;
+}
+
+bool uefi_vars_is_sb_pk(uefi_variable *var)
+{
+    if (qemu_uuid_is_equal(&var->guid, &EfiGlobalVariable) &&
+        uefi_str_equal(var->name, var->name_size, name_pk, sizeof(name_pk))) {
+        return true;
+    }
+    return false;
+}
+
+static bool uefi_vars_is_sb_kek(uefi_variable *var)
+{
+    if (qemu_uuid_is_equal(&var->guid, &EfiGlobalVariable) &&
+        uefi_str_equal(var->name, var->name_size, name_kek, sizeof(name_kek))) {
+        return true;
+    }
+    return false;
+}
+
+static bool uefi_vars_is_sb_db(uefi_variable *var)
+{
+    if (!qemu_uuid_is_equal(&var->guid, &EfiImageSecurityDatabase)) {
+        return false;
+    }
+    if (uefi_str_equal(var->name, var->name_size, name_db, sizeof(name_db))) {
+        return true;
+    }
+    if (uefi_str_equal(var->name, var->name_size, name_dbx, sizeof(name_dbx))) {
+        return true;
+    }
+    return false;
+}
+
+bool uefi_vars_is_sb_any(uefi_variable *var)
+{
+    if (uefi_vars_is_sb_pk(var) ||
+        uefi_vars_is_sb_kek(var) ||
+        uefi_vars_is_sb_db(var)) {
+        return true;
+    }
+    return false;
+}
+
+static uefi_variable *uefi_vars_find_siglist(uefi_vars_state *uv,
+                                             uefi_variable *var)
+{
+    if (uefi_vars_is_sb_pk(var)) {
+        return uefi_vars_find_variable(uv, EfiGlobalVariable,
+                                       name_pk, sizeof(name_pk));
+    }
+    if (uefi_vars_is_sb_kek(var)) {
+        return uefi_vars_find_variable(uv, EfiGlobalVariable,
+                                       name_pk, sizeof(name_pk));
+    }
+    if (uefi_vars_is_sb_db(var)) {
+        return uefi_vars_find_variable(uv, EfiGlobalVariable,
+                                       name_kek, sizeof(name_kek));
+    }
+
+    return NULL;
+}
+
+static efi_status uefi_vars_check_auth_2_sb(uefi_vars_state *uv,
+                                            uefi_variable *var,
+                                            mm_variable_access *va,
+                                            void *data,
+                                            uint64_t data_offset)
+{
+    variable_auth_2 *auth = data;
+    uefi_variable *siglist;
+
+    if (custom_mode_is_active(uv)) {
+        /* no authentication in custom mode */
+        return EFI_SUCCESS;
+    }
+
+    if (setup_mode_is_active(uv) && !uefi_vars_is_sb_pk(var)) {
+        /* no authentication in setup mode (except PK) */
+        return EFI_SUCCESS;
+    }
+
+    if (auth->hdr_length == 24) {
+        /* no signature (auth->cert_data is empty) */
+        return EFI_SECURITY_VIOLATION;
+    }
+
+    siglist = uefi_vars_find_siglist(uv, var);
+    if (!siglist && setup_mode_is_active(uv) && uefi_vars_is_sb_pk(var)) {
+        /* check PK is self-signed */
+        uefi_variable tmp = {
+            .guid       = EfiGlobalVariable,
+            .name       = (uint16_t *)name_pk,
+            .name_size  = sizeof(name_pk),
+            .attributes = sigdb_attrs,
+            .data       = data + data_offset,
+            .data_size  = va->data_size - data_offset,
+        };
+        return uefi_vars_check_pkcs7_2(&tmp, NULL, NULL, va, data);
+    }
+
+    return uefi_vars_check_pkcs7_2(siglist, NULL, NULL, va, data);
+}
+
+efi_status uefi_vars_check_auth_2(uefi_vars_state *uv, uefi_variable *var,
+                                  mm_variable_access *va, void *data)
+{
+    variable_auth_2 *auth = data;
+    uint64_t data_offset;
+    efi_status status;
+
+    if (va->data_size < sizeof(*auth)) {
+        return EFI_SECURITY_VIOLATION;
+    }
+    if (uadd64_overflow(sizeof(efi_time), auth->hdr_length, &data_offset)) {
+        return EFI_SECURITY_VIOLATION;
+    }
+    if (va->data_size < data_offset) {
+        return EFI_SECURITY_VIOLATION;
+    }
+
+    if (auth->hdr_revision != 0x0200 ||
+        auth->hdr_cert_type != WIN_CERT_TYPE_EFI_GUID ||
+        !qemu_uuid_is_equal(&auth->guid_cert_type, &EfiCertTypePkcs7Guid)) {
+        return EFI_UNSUPPORTED;
+    }
+
+    if (uefi_vars_is_sb_any(var)) {
+        /* secure boot variables */
+        status = uefi_vars_check_auth_2_sb(uv, var, va, data, data_offset);
+        if (status != EFI_SUCCESS) {
+            return status;
+        }
+    } else {
+        /* other authenticated variables */
+        status = uefi_vars_check_pkcs7_2(NULL,
+                                         &var->digest, &var->digest_size,
+                                         va, data);
+        if (status != EFI_SUCCESS) {
+            return status;
+        }
+    }
+
+    /* checks passed, set variable data */
+    var->time = auth->timestamp;
+    if (va->data_size - data_offset > 0) {
+        var->data = g_malloc(va->data_size - data_offset);
+        memcpy(var->data, data + data_offset, va->data_size - data_offset);
+        var->data_size = va->data_size - data_offset;
+    }
+
+    return EFI_SUCCESS;
+}
+
+efi_status uefi_vars_check_secure_boot(uefi_vars_state *uv, uefi_variable *var)
+{
+    uint8_t *value = var->data;
+
+    if (uefi_vars_is_sb_any(var)) {
+        if (var->attributes != sigdb_attrs) {
+            return EFI_INVALID_PARAMETER;
+        }
+    }
+
+    /* reject SecureBootEnable updates if force_secure_boot is set */
+    if (qemu_uuid_is_equal(&var->guid, &EfiSecureBootEnableDisable) &&
+        uefi_str_equal(var->name, var->name_size,
+                       name_sb_enable, sizeof(name_sb_enable)) &&
+        uv->force_secure_boot &&
+        value[0] != SECURE_BOOT_ENABLE) {
+        return EFI_WRITE_PROTECTED;
+    }
+
+    /* reject CustomMode updates if disable_custom_mode is set */
+    if (qemu_uuid_is_equal(&var->guid, &EfiCustomModeEnable) &&
+        uefi_str_equal(var->name, var->name_size,
+                       name_custom_mode, sizeof(name_custom_mode)) &&
+        uv->disable_custom_mode) {
+        return EFI_WRITE_PROTECTED;
+    }
+
+    return EFI_SUCCESS;
+}
+
+/* AuthVariableLibInitialize */
+void uefi_vars_auth_init(uefi_vars_state *uv)
+{
+    uefi_variable *pk_var, *sbe_var;
+    uint8_t platform_mode, sb, sbe, vk;
+
+    /* SetupMode */
+    pk_var = uefi_vars_find_variable(uv, EfiGlobalVariable,
+                                     name_pk, sizeof(name_pk));
+    if (!pk_var) {
+        platform_mode = SETUP_MODE;
+    } else {
+        platform_mode = USER_MODE;
+    }
+    set_setup_mode(uv, platform_mode);
+
+    /* SignatureSupport */
+    set_signature_support(uv);
+
+    /* SecureBootEnable */
+    sbe = SECURE_BOOT_DISABLE;
+    sbe_var = uefi_vars_find_variable(uv, EfiSecureBootEnableDisable,
+                                      name_sb_enable, sizeof(name_sb_enable));
+    if (sbe_var) {
+        if (platform_mode == USER_MODE) {
+            sbe = ((uint8_t *)sbe_var->data)[0];
+        }
+    } else if (platform_mode == USER_MODE) {
+        sbe = SECURE_BOOT_ENABLE;
+        set_secure_boot_enable(uv, sbe);
+    }
+
+    if (uv->force_secure_boot && sbe != SECURE_BOOT_ENABLE) {
+        sbe = SECURE_BOOT_ENABLE;
+        set_secure_boot_enable(uv, sbe);
+    }
+
+    /* SecureBoot */
+    if ((sbe == SECURE_BOOT_ENABLE) && (platform_mode == USER_MODE)) {
+        sb = SECURE_BOOT_MODE_ENABLE;
+    } else {
+        sb = SECURE_BOOT_MODE_DISABLE;
+    }
+    set_secure_boot(uv, sb);
+
+    /* CustomMode */
+    set_custom_mode(uv, STANDARD_SECURE_BOOT_MODE);
+
+    vk = 0;
+    uefi_vars_set_variable(uv, EfiGlobalVariable,
+                           name_vk_nv, sizeof(name_vk_nv),
+                           EFI_VARIABLE_NON_VOLATILE |
+                           EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                           EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS,
+                           &vk, sizeof(vk));
+    uefi_vars_set_variable(uv, EfiGlobalVariable,
+                           name_vk, sizeof(name_vk),
+                           EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                           EFI_VARIABLE_RUNTIME_ACCESS,
+                           &vk, sizeof(vk));
+
+    /* flush to disk */
+    uefi_vars_json_save(uv);
+}
-- 
2.48.1