[PATCH v12 10/13] HP BIOSCFG driver - spmobj-attributes

Jorge Lopez
2023-05-05T22:01:54Z

HP BIOS Configuration driver purpose is to provide a driver supporting
the latest sysfs class firmware attributes framework allowing the user
to change BIOS settings and security solutions on HP Inc.’s commercial
notebooks.

Many features of HP Commercial notebooks can be managed using Windows
Management Instrumentation (WMI). WMI is an implementation of Web-Based
Enterprise Management (WBEM) that provides a standards-based interface
for changing and monitoring system settings. HP BIOSCFG driver provides
a native Linux solution and the exposed features facilitates the
migration to Linux environments.

The Linux security features to be provided in hp-bioscfg driver enables
managing the BIOS settings and security solutions via sysfs, a virtual
filesystem that can be used by user-mode applications. The new
documentation cover HP-specific firmware sysfs attributes such Secure
Platform Management and Sure Start. Each section provides security
feature description and identifies sysfs directories and files exposed
by the driver.

Many HP Commercial notebooks include a feature called Secure Platform
Management (SPM), which replaces older password-based BIOS settings
management with public key cryptography. PC secure product management
begins when a target system is provisioned with cryptographic keys
that are used to ensure the integrity of communications between system
management utilities and the BIOS.

HP Commercial notebooks have several BIOS settings that control its
behaviour and capabilities, many of which are related to security.
To prevent unauthorized changes to these settings, the system can
be configured to use a cryptographic signature-based authorization
string that the BIOS will use to verify authorization to modify the
setting.

Linux Security components are under development and not published yet.
The only linux component is the driver (hp bioscfg) at this time.
Other published security components are under Windows.

Signed-off-by: Jorge Lopez <jorge.lopez2@hp.com>

---
Based on the latest platform-drivers-x86.git/for-next
---
.../x86/hp/hp-bioscfg/spmobj-attributes.c | 381 ++++++++++++++++++
1 file changed, 381 insertions(+)
create mode 100644 drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c

diff --git a/drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c b/drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c
new file mode 100644
index 000000000000..f08f7aae9423
--- /dev/null
+++ b/drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c
@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Functions corresponding to secure platform management object type
+ * attributes under BIOS PASSWORD for use with hp-bioscfg driver
+ *
+ * Copyright (c) 2022 HP Development Company, L.P.
+ */
+
+#include "bioscfg.h"
+
+static const char * const spm_state_types[] = {
+ "not provisioned",
+ "provisioned",
+ "provisioning in progress",
+};
+
+static const char * const spm_mechanism_types[] = {
+ "not provisioned",
+ "signing-key",
+ "endorsement-key",
+};
+
+struct secureplatform_provisioning_data {
+ u8 state;
+ u8 version[2];
+ u8 reserved1;
+ u32 features;
+ u32 nonce;
+ u8 reserved2[28];
+ u8 sk_mod[MAX_KEY_MOD];
+ u8 kek_mod[MAX_KEY_MOD];
+};
+
+int check_spm_is_enabled(void)
+{
+ /* do we need to check the admin password is also configured */
+ return bioscfg_drv.spm_data.is_enabled;
+}
+
+/**
+ * calculate_security_buffer() - determines size of security buffer
+ * for authentication scheme
+ *
+ * @authentication: the authentication content
+ *
+ * Currently only supported type is Admin password
+ */
+size_t calculate_security_buffer(const char *authentication)
+{
+ int size;
+
+ if (authentication && strlen(authentication) > 0) {
+ size = sizeof(u16) + (strlen(authentication) * sizeof(u16));
+ if (!strstarts(authentication, BEAM_PREFIX))
+ size += strlen(UTF_PREFIX) * sizeof(u16);
+
+ return size;
+ }
+
+ size = sizeof(u16) * 2;
+ return size;
+}
+
+/**
+ * populate_security_buffer() - builds a security buffer for
+ * authentication scheme
+ *
+ * @buffer: the buffer to populate
+ * @authentication: the authentication content
+ *
+ * Currently only supported type is PLAIN TEXT
+ */
+int populate_security_buffer(u16 *buffer, const char *authentication)
+{
+ u16 *auth = buffer;
+ u16 *retbuffer;
+ char *strprefix = NULL;
+ int ret = 0;
+
+ if (strstarts(authentication, BEAM_PREFIX)) {
+ /*
+ * BEAM_PREFIX is append to buffer when a signature
+ * is provided and Sure Admin is enabled in BIOS
+ */
+ // BEAM_PREFIX found, convert part to unicode
+ retbuffer = hp_ascii_to_utf16_unicode(auth, authentication);
+ if (!retbuffer) {
+ ret = -EINVAL;
+ goto out_buffer;
+ }
+ auth = retbuffer;
+
+ } else {
+ /*
+ * UTF-16 prefix is append to the * buffer when a BIOS
+ * admin password is configured in BIOS
+ */
+
+ // append UTF_PREFIX to part and then convert it to unicode
+ strprefix = kasprintf(GFP_KERNEL, "%s%s", UTF_PREFIX,
+ authentication);
+ if (!strprefix)
+ goto out_buffer;
+
+ retbuffer = hp_ascii_to_utf16_unicode(auth, strprefix);
+ if (!retbuffer) {
+ ret = -EINVAL;
+ goto out_buffer;
+ }
+ auth = retbuffer;
+ }
+
+out_buffer:
+ kfree(strprefix);
+ return ret;
+}
+
+static ssize_t update_spm_state(void)
+{
+ int ret;
+ struct secureplatform_provisioning_data data;
+
+ ret = hp_wmi_perform_query(HPWMI_SECUREPLATFORM_GET_STATE,
+ HPWMI_SECUREPLATFORM, &data, 0,
+ sizeof(data));
+ if (ret < 0)
+ goto state_exit;
+
+ bioscfg_drv.spm_data.mechanism = data.state;
+ if (bioscfg_drv.spm_data.mechanism)
+ bioscfg_drv.spm_data.is_enabled = 1;
+
+state_exit:
+ return ret;
+}
+
+static ssize_t statusbin(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ struct secureplatform_provisioning_data *buf)
+{
+ int ret = hp_wmi_perform_query(HPWMI_SECUREPLATFORM_GET_STATE,
+ HPWMI_SECUREPLATFORM, buf, 0,
+ sizeof(struct secureplatform_provisioning_data));
+
+ return ret < 0 ? ret : sizeof(struct secureplatform_provisioning_data);
+}
+
+/*
+ * status_show - Reads SPM status
+ */
+static ssize_t status_show(struct kobject *kobj, struct kobj_attribute
+ *attr, char *buf)
+{
+ int ret, i;
+ struct secureplatform_provisioning_data data;
+
+ ret = statusbin(kobj, attr, &data);
+ if (ret < 0)
+ goto status_exit;
+
+ sysfs_emit(buf, "%s{\n", buf);
+ sysfs_emit(buf, "%s\t\"State\": \"%s\",\n", buf,
+ spm_state_types[data.state]);
+ sysfs_emit(buf, "%s\t\"Version\": \"%d.%d\",\n", buf, data.version[0],
+ data.version[1]);
+
+ /*
+ * state == 0 means secure platform management
+ * feature is not configured in BIOS.
+ */
+ if (data.state == 0)
+ goto status_exit;
+
+ sysfs_emit(buf, "%s\t\"Nonce\": %d,\n", buf, data.nonce);
+ sysfs_emit(buf, "%s\t\"FeaturesInUse\": %d,\n", buf, data.features);
+ sysfs_emit(buf, "%s\t\"EndorsementKeyMod\": \"", buf);
+
+ for (i = 255; i >= 0; i--)
+ sysfs_emit(buf, "%s %u", buf, data.kek_mod[i]);
+
+ sysfs_emit(buf, "%s \",\n", buf);
+ sysfs_emit(buf, "%s\t\"SigningKeyMod\": \"", buf);
+
+ for (i = 255; i >= 0; i--)
+ sysfs_emit(buf, "%s %u", buf, data.sk_mod[i]);
+
+ /* Return buf contents */
+
+ sysfs_emit(buf, "%s \"\n", buf);
+ sysfs_emit(buf, "%s}\n", buf);
+
+status_exit:
+ return strnlen(buf, PAGE_SIZE);
+}
+
+static struct kobj_attribute password_spm_status = __ATTR_RO(status);
+
+ATTRIBUTE_SPM_N_PROPERTY_SHOW(is_enabled, spm);
+static struct kobj_attribute password_spm_is_key_enabled = __ATTR_RO(is_enabled);
+
+static ssize_t key_mechanism_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ return sysfs_emit(buf, "%s\n",
+ spm_mechanism_types[bioscfg_drv.spm_data.mechanism]);
+}
+
+static struct kobj_attribute password_spm_key_mechanism = __ATTR_RO(key_mechanism);
+
+static ssize_t sk_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret;
+ int length;
+
+ length = count;
+ if (buf[length - 1] == '\n')
+ length--;
+
+ /* allocate space and copy current signing key */
+ bioscfg_drv.spm_data.signing_key = kmalloc(length, GFP_KERNEL);
+ if (!bioscfg_drv.spm_data.signing_key) {
+ ret = -ENOMEM;
+ goto exit_sk;
+ }
+
+ strscpy(bioscfg_drv.spm_data.signing_key, buf, length);
+ bioscfg_drv.spm_data.signing_key[length] = '\0';
+
+ /* submit signing key payload */
+ ret = hp_wmi_perform_query(HPWMI_SECUREPLATFORM_SET_SK,
+ HPWMI_SECUREPLATFORM,
+ (void *)bioscfg_drv.spm_data.signing_key,
+ length, 0);
+
+ if (!ret) {
+ bioscfg_drv.spm_data.mechanism = SIGNING_KEY;
+ set_reboot_and_signal_event();
+ }
+
+exit_sk:
+ kfree(bioscfg_drv.spm_data.signing_key);
+ bioscfg_drv.spm_data.signing_key = NULL;
+
+ return ret ? ret : count;
+}
+
+static struct kobj_attribute password_spm_signing_key = __ATTR_WO(sk);
+
+static ssize_t kek_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret;
+ int length;
+
+ length = count;
+ if (buf[length - 1] == '\n')
+ length--;
+
+ /* allocate space and copy current signing key */
+ bioscfg_drv.spm_data.endorsement_key = kmalloc(length, GFP_KERNEL);
+ if (!bioscfg_drv.spm_data.endorsement_key) {
+ ret = -ENOMEM;
+ goto exit_kek;
+ }
+
+ memcpy(bioscfg_drv.spm_data.endorsement_key, buf, length);
+ bioscfg_drv.spm_data.endorsement_key[length] = '\0';
+
+ ret = hp_wmi_perform_query(HPWMI_SECUREPLATFORM_SET_KEK,
+ HPWMI_SECUREPLATFORM,
+ (void *)bioscfg_drv.spm_data.endorsement_key,
+ count, 0);
+
+ if (!ret) {
+ bioscfg_drv.spm_data.mechanism = ENDORSEMENT_KEY;
+ set_reboot_and_signal_event();
+ }
+
+exit_kek:
+ kfree(bioscfg_drv.spm_data.endorsement_key);
+ bioscfg_drv.spm_data.endorsement_key = NULL;
+
+ return ret ? ret : count;
+}
+
+static struct kobj_attribute password_spm_endorsement_key = __ATTR_WO(kek);
+
+static ssize_t role_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ return sysfs_emit(buf, "%s\n", BIOS_SPM);
+}
+
+static struct kobj_attribute password_spm_role = __ATTR_RO(role);
+
+static ssize_t auth_token_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret = 0;
+ int length;
+
+ length = count;
+ if (buf[length - 1] == '\n')
+ length--;
+
+ /* allocate space and copy current auth token */
+ bioscfg_drv.spm_data.auth_token = kmalloc(count, GFP_KERNEL);
+ if (!bioscfg_drv.spm_data.auth_token) {
+ ret = -ENOMEM;
+ goto exit_token;
+ }
+
+ memcpy(bioscfg_drv.spm_data.auth_token, buf, count);
+ bioscfg_drv.spm_data.auth_token[length] = '\0';
+ return count;
+
+exit_token:
+ kfree(bioscfg_drv.spm_data.auth_token);
+ bioscfg_drv.spm_data.auth_token = NULL;
+
+ return ret;
+}
+
+static struct kobj_attribute password_spm_auth_token = __ATTR_WO(auth_token);
+
+static struct attribute *secure_platform_attrs[] = {
+ &password_spm_is_key_enabled.attr,
+ &password_spm_signing_key.attr,
+ &password_spm_endorsement_key.attr,
+ &password_spm_key_mechanism.attr,
+ &password_spm_status.attr,
+ &password_spm_role.attr,
+ &password_spm_auth_token.attr,
+ NULL,
+};
+
+static const struct attribute_group secure_platform_attr_group = {
+ .attrs = secure_platform_attrs,
+};
+
+void exit_secure_platform_attributes(void)
+{
+ /* remove secure platform sysfs entry and free key data*/
+
+ kfree(bioscfg_drv.spm_data.endorsement_key);
+ bioscfg_drv.spm_data.endorsement_key = NULL;
+
+ kfree(bioscfg_drv.spm_data.signing_key);
+ bioscfg_drv.spm_data.signing_key = NULL;
+
+ kfree(bioscfg_drv.spm_data.auth_token);
+ bioscfg_drv.spm_data.auth_token = NULL;
+
+ if (bioscfg_drv.spm_data.attr_name_kobj)
+ sysfs_remove_group(bioscfg_drv.spm_data.attr_name_kobj,
+ &secure_platform_attr_group);
+}
+
+int populate_secure_platform_data(struct kobject *attr_name_kobj)
+{
+ /* Populate data for Secure Platform Management */
+ bioscfg_drv.spm_data.attr_name_kobj = attr_name_kobj;
+
+ strscpy(bioscfg_drv.spm_data.attribute_name, SPM_STR,
+ sizeof(bioscfg_drv.spm_data.attribute_name));
+
+ bioscfg_drv.spm_data.is_enabled = 0;
+ bioscfg_drv.spm_data.mechanism = 0;
+ bioscfg_drv.pending_reboot = false;
+ update_spm_state();
+
+ bioscfg_drv.spm_data.endorsement_key = NULL;
+ bioscfg_drv.spm_data.signing_key = NULL;
+ bioscfg_drv.spm_data.auth_token = NULL;
+
+ return sysfs_create_group(attr_name_kobj, &secure_platform_attr_group);
+}
--
2.34.1