--- /dev/null
- guard(rwsem_write)(&tsm_rwsem);
+ // SPDX-License-Identifier: GPL-2.0-only
+ /* Copyright(c) 2023 Intel Corporation. All rights reserved. */
+
+ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+ #include <linux/tsm.h>
+ #include <linux/err.h>
+ #include <linux/slab.h>
+ #include <linux/rwsem.h>
+ #include <linux/string.h>
+ #include <linux/module.h>
+ #include <linux/cleanup.h>
+ #include <linux/configfs.h>
+
+ static struct tsm_provider {
+ const struct tsm_report_ops *ops;
+ void *data;
++ atomic_t count;
+ } provider;
+ static DECLARE_RWSEM(tsm_rwsem);
+
+ /**
+ * DOC: Trusted Security Module (TSM) Attestation Report Interface
+ *
+ * The TSM report interface is a common provider of blobs that facilitate
+ * attestation of a TVM (confidential computing guest) by an attestation
+ * service. A TSM report combines a user-defined blob (likely a public-key with
+ * a nonce for a key-exchange protocol) with a signed attestation report. That
+ * combined blob is then used to obtain secrets provided by an agent that can
+ * validate the attestation report. The expectation is that this interface is
+ * invoked infrequently, however configfs allows for multiple agents to
+ * own their own report generation instances to generate reports as
+ * often as needed.
+ *
+ * The attestation report format is TSM provider specific, when / if a standard
+ * materializes that can be published instead of the vendor layout. Until then
+ * the 'provider' attribute indicates the format of 'outblob', and optionally
+ * 'auxblob' and 'manifestblob'.
+ */
+
+ struct tsm_report_state {
+ struct tsm_report report;
+ unsigned long write_generation;
+ unsigned long read_generation;
+ struct config_item cfg;
+ };
+
+ enum tsm_data_select {
+ TSM_REPORT,
+ TSM_CERTS,
+ TSM_MANIFEST,
+ };
+
+ static struct tsm_report *to_tsm_report(struct config_item *cfg)
+ {
+ struct tsm_report_state *state =
+ container_of(cfg, struct tsm_report_state, cfg);
+
+ return &state->report;
+ }
+
+ static struct tsm_report_state *to_state(struct tsm_report *report)
+ {
+ return container_of(report, struct tsm_report_state, report);
+ }
+
+ static int try_advance_write_generation(struct tsm_report *report)
+ {
+ struct tsm_report_state *state = to_state(report);
+
+ lockdep_assert_held_write(&tsm_rwsem);
+
+ /*
+ * Malicious or broken userspace has written enough times for
+ * read_generation == write_generation by modular arithmetic without an
+ * interim read. Stop accepting updates until the current report
+ * configuration is read.
+ */
+ if (state->write_generation == state->read_generation - 1)
+ return -EBUSY;
+ state->write_generation++;
+ return 0;
+ }
+
+ static ssize_t tsm_report_privlevel_store(struct config_item *cfg,
+ const char *buf, size_t len)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+ unsigned int val;
+ int rc;
+
+ rc = kstrtouint(buf, 0, &val);
+ if (rc)
+ return rc;
+
++ guard(rwsem_write)(&tsm_rwsem);
++ if (!provider.ops)
++ return -ENXIO;
++
+ /*
+ * The valid privilege levels that a TSM might accept, if it accepts a
+ * privilege level setting at all, are a max of TSM_PRIVLEVEL_MAX (see
+ * SEV-SNP GHCB) and a minimum of a TSM selected floor value no less
+ * than 0.
+ */
+ if (provider.ops->privlevel_floor > val || val > TSM_REPORT_PRIVLEVEL_MAX)
+ return -EINVAL;
+
- return -ENOTTY;
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+ report->desc.privlevel = val;
+
+ return len;
+ }
+ CONFIGFS_ATTR_WO(tsm_report_, privlevel);
+
+ static ssize_t tsm_report_privlevel_floor_show(struct config_item *cfg,
+ char *buf)
+ {
+ guard(rwsem_read)(&tsm_rwsem);
++
++ if (!provider.ops)
++ return -ENXIO;
++
+ return sysfs_emit(buf, "%u\n", provider.ops->privlevel_floor);
+ }
+ CONFIGFS_ATTR_RO(tsm_report_, privlevel_floor);
+
+ static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
+ const char *buf, size_t len)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+ size_t sp_len;
+ char *sp;
+ int rc;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+
+ sp_len = (buf[len - 1] != '\n') ? len : len - 1;
+
+ sp = kstrndup(buf, sp_len, GFP_KERNEL);
+ if (!sp)
+ return -ENOMEM;
+ kfree(report->desc.service_provider);
+
+ report->desc.service_provider = sp;
+
+ return len;
+ }
+ CONFIGFS_ATTR_WO(tsm_report_, service_provider);
+
+ static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
+ const char *buf, size_t len)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+ int rc;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+
+ report->desc.service_guid = guid_null;
+
+ rc = guid_parse(buf, &report->desc.service_guid);
+ if (rc)
+ return rc;
+
+ return len;
+ }
+ CONFIGFS_ATTR_WO(tsm_report_, service_guid);
+
+ static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg,
+ const char *buf, size_t len)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+ unsigned int val;
+ int rc;
+
+ rc = kstrtouint(buf, 0, &val);
+ if (rc)
+ return rc;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+ report->desc.service_manifest_version = val;
+
+ return len;
+ }
+ CONFIGFS_ATTR_WO(tsm_report_, service_manifest_version);
+
+ static ssize_t tsm_report_inblob_write(struct config_item *cfg,
+ const void *buf, size_t count)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+ int rc;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+
+ report->desc.inblob_len = count;
+ memcpy(report->desc.inblob, buf, count);
+ return count;
+ }
+ CONFIGFS_BIN_ATTR_WO(tsm_report_, inblob, NULL, TSM_REPORT_INBLOB_MAX);
+
+ static ssize_t tsm_report_generation_show(struct config_item *cfg, char *buf)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+ struct tsm_report_state *state = to_state(report);
+
+ guard(rwsem_read)(&tsm_rwsem);
+ return sysfs_emit(buf, "%lu\n", state->write_generation);
+ }
+ CONFIGFS_ATTR_RO(tsm_report_, generation);
+
+ static ssize_t tsm_report_provider_show(struct config_item *cfg, char *buf)
+ {
+ guard(rwsem_read)(&tsm_rwsem);
++ if (!provider.ops)
++ return -ENXIO;
++
+ return sysfs_emit(buf, "%s\n", provider.ops->name);
+ }
+ CONFIGFS_ATTR_RO(tsm_report_, provider);
+
+ static ssize_t __read_report(struct tsm_report *report, void *buf, size_t count,
+ enum tsm_data_select select)
+ {
+ loff_t offset = 0;
+ ssize_t len;
+ u8 *out;
+
+ if (select == TSM_REPORT) {
+ out = report->outblob;
+ len = report->outblob_len;
+ } else if (select == TSM_MANIFEST) {
+ out = report->manifestblob;
+ len = report->manifestblob_len;
+ } else {
+ out = report->auxblob;
+ len = report->auxblob_len;
+ }
+
+ /*
+ * Recall that a NULL @buf is configfs requesting the size of
+ * the buffer.
+ */
+ if (!buf)
+ return len;
+ return memory_read_from_buffer(buf, count, &offset, out, len);
+ }
+
+ static ssize_t read_cached_report(struct tsm_report *report, void *buf,
+ size_t count, enum tsm_data_select select)
+ {
+ struct tsm_report_state *state = to_state(report);
+
+ guard(rwsem_read)(&tsm_rwsem);
+ if (!report->desc.inblob_len)
+ return -EINVAL;
+
+ /*
+ * A given TSM backend always fills in ->outblob regardless of
+ * whether the report includes an auxblob/manifestblob or not.
+ */
+ if (!report->outblob ||
+ state->read_generation != state->write_generation)
+ return -EWOULDBLOCK;
+
+ return __read_report(report, buf, count, select);
+ }
+
+ static ssize_t tsm_report_read(struct tsm_report *report, void *buf,
+ size_t count, enum tsm_data_select select)
+ {
+ struct tsm_report_state *state = to_state(report);
+ const struct tsm_report_ops *ops;
+ ssize_t rc;
+
+ /* try to read from the existing report if present and valid... */
+ rc = read_cached_report(report, buf, count, select);
+ if (rc >= 0 || rc != -EWOULDBLOCK)
+ return rc;
+
+ /* slow path, report may need to be regenerated... */
+ guard(rwsem_write)(&tsm_rwsem);
+ ops = provider.ops;
+ if (!ops)
++ return -ENXIO;
+ if (!report->desc.inblob_len)
+ return -EINVAL;
+
+ /* did another thread already generate this report? */
+ if (report->outblob &&
+ state->read_generation == state->write_generation)
+ goto out;
+
+ kvfree(report->outblob);
+ kvfree(report->auxblob);
+ kvfree(report->manifestblob);
+ report->outblob = NULL;
+ report->auxblob = NULL;
+ report->manifestblob = NULL;
+ rc = ops->report_new(report, provider.data);
+ if (rc < 0)
+ return rc;
+ state->read_generation = state->write_generation;
+ out:
+ return __read_report(report, buf, count, select);
+ }
+
+ static ssize_t tsm_report_outblob_read(struct config_item *cfg, void *buf,
+ size_t count)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+
+ return tsm_report_read(report, buf, count, TSM_REPORT);
+ }
+ CONFIGFS_BIN_ATTR_RO(tsm_report_, outblob, NULL, TSM_REPORT_OUTBLOB_MAX);
+
+ static ssize_t tsm_report_auxblob_read(struct config_item *cfg, void *buf,
+ size_t count)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+
+ return tsm_report_read(report, buf, count, TSM_CERTS);
+ }
+ CONFIGFS_BIN_ATTR_RO(tsm_report_, auxblob, NULL, TSM_REPORT_OUTBLOB_MAX);
+
+ static ssize_t tsm_report_manifestblob_read(struct config_item *cfg, void *buf,
+ size_t count)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+
+ return tsm_report_read(report, buf, count, TSM_MANIFEST);
+ }
+ CONFIGFS_BIN_ATTR_RO(tsm_report_, manifestblob, NULL, TSM_REPORT_OUTBLOB_MAX);
+
+ static struct configfs_attribute *tsm_report_attrs[] = {
+ [TSM_REPORT_GENERATION] = &tsm_report_attr_generation,
+ [TSM_REPORT_PROVIDER] = &tsm_report_attr_provider,
+ [TSM_REPORT_PRIVLEVEL] = &tsm_report_attr_privlevel,
+ [TSM_REPORT_PRIVLEVEL_FLOOR] = &tsm_report_attr_privlevel_floor,
+ [TSM_REPORT_SERVICE_PROVIDER] = &tsm_report_attr_service_provider,
+ [TSM_REPORT_SERVICE_GUID] = &tsm_report_attr_service_guid,
+ [TSM_REPORT_SERVICE_MANIFEST_VER] = &tsm_report_attr_service_manifest_version,
+ NULL,
+ };
+
+ static struct configfs_bin_attribute *tsm_report_bin_attrs[] = {
+ [TSM_REPORT_INBLOB] = &tsm_report_attr_inblob,
+ [TSM_REPORT_OUTBLOB] = &tsm_report_attr_outblob,
+ [TSM_REPORT_AUXBLOB] = &tsm_report_attr_auxblob,
+ [TSM_REPORT_MANIFESTBLOB] = &tsm_report_attr_manifestblob,
+ NULL,
+ };
+
+ static void tsm_report_item_release(struct config_item *cfg)
+ {
+ struct tsm_report *report = to_tsm_report(cfg);
+ struct tsm_report_state *state = to_state(report);
+
+ kvfree(report->manifestblob);
+ kvfree(report->auxblob);
+ kvfree(report->outblob);
+ kfree(report->desc.service_provider);
+ kfree(state);
+ }
+
+ static struct configfs_item_operations tsm_report_item_ops = {
+ .release = tsm_report_item_release,
+ };
+
+ static bool tsm_report_is_visible(struct config_item *item,
+ struct configfs_attribute *attr, int n)
+ {
+ guard(rwsem_read)(&tsm_rwsem);
+ if (!provider.ops)
+ return false;
+
+ if (!provider.ops->report_attr_visible)
+ return true;
+
+ return provider.ops->report_attr_visible(n);
+ }
+
+ static bool tsm_report_is_bin_visible(struct config_item *item,
+ struct configfs_bin_attribute *attr, int n)
+ {
+ guard(rwsem_read)(&tsm_rwsem);
+ if (!provider.ops)
+ return false;
+
+ if (!provider.ops->report_bin_attr_visible)
+ return true;
+
+ return provider.ops->report_bin_attr_visible(n);
+ }
+
+ static struct configfs_group_operations tsm_report_attr_group_ops = {
+ .is_visible = tsm_report_is_visible,
+ .is_bin_visible = tsm_report_is_bin_visible,
+ };
+
+ static const struct config_item_type tsm_report_type = {
+ .ct_owner = THIS_MODULE,
+ .ct_bin_attrs = tsm_report_bin_attrs,
+ .ct_attrs = tsm_report_attrs,
+ .ct_item_ops = &tsm_report_item_ops,
+ .ct_group_ops = &tsm_report_attr_group_ops,
+ };
+
+ static struct config_item *tsm_report_make_item(struct config_group *group,
+ const char *name)
+ {
+ struct tsm_report_state *state;
+
+ guard(rwsem_read)(&tsm_rwsem);
+ if (!provider.ops)
+ return ERR_PTR(-ENXIO);
+
+ state = kzalloc(sizeof(*state), GFP_KERNEL);
+ if (!state)
+ return ERR_PTR(-ENOMEM);
+
++ atomic_inc(&provider.count);
+ config_item_init_type_name(&state->cfg, name, &tsm_report_type);
+ return &state->cfg;
+ }
+
++static void tsm_report_drop_item(struct config_group *group, struct config_item *item)
++{
++ config_item_put(item);
++ atomic_dec(&provider.count);
++}
++
+ static struct configfs_group_operations tsm_report_group_ops = {
+ .make_item = tsm_report_make_item,
++ .drop_item = tsm_report_drop_item,
+ };
+
+ static const struct config_item_type tsm_reports_type = {
+ .ct_owner = THIS_MODULE,
+ .ct_group_ops = &tsm_report_group_ops,
+ };
+
+ static const struct config_item_type tsm_root_group_type = {
+ .ct_owner = THIS_MODULE,
+ };
+
+ static struct configfs_subsystem tsm_configfs = {
+ .su_group = {
+ .cg_item = {
+ .ci_namebuf = "tsm",
+ .ci_type = &tsm_root_group_type,
+ },
+ },
+ .su_mutex = __MUTEX_INITIALIZER(tsm_configfs.su_mutex),
+ };
+
+ int tsm_report_register(const struct tsm_report_ops *ops, void *priv)
+ {
+ const struct tsm_report_ops *conflict;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ conflict = provider.ops;
+ if (conflict) {
+ pr_err("\"%s\" ops already registered\n", conflict->name);
+ return -EBUSY;
+ }
+
++ if (atomic_read(&provider.count)) {
++ pr_err("configfs/tsm/report not empty\n");
++ return -EBUSY;
++ }
++
+ provider.ops = ops;
+ provider.data = priv;
+ return 0;
+ }
+ EXPORT_SYMBOL_GPL(tsm_report_register);
+
+ int tsm_report_unregister(const struct tsm_report_ops *ops)
+ {
+ guard(rwsem_write)(&tsm_rwsem);
+ if (ops != provider.ops)
+ return -EBUSY;
++ if (atomic_read(&provider.count))
++ pr_warn("\"%s\" unregistered with items present in configfs/tsm/report\n",
++ provider.ops->name);
+ provider.ops = NULL;
+ provider.data = NULL;
+ return 0;
+ }
+ EXPORT_SYMBOL_GPL(tsm_report_unregister);
+
+ static struct config_group *tsm_report_group;
+
+ static int __init tsm_report_init(void)
+ {
+ struct config_group *root = &tsm_configfs.su_group;
+ struct config_group *tsm;
+ int rc;
+
+ config_group_init(root);
+ rc = configfs_register_subsystem(&tsm_configfs);
+ if (rc)
+ return rc;
+
+ tsm = configfs_register_default_group(root, "report",
+ &tsm_reports_type);
+ if (IS_ERR(tsm)) {
+ configfs_unregister_subsystem(&tsm_configfs);
+ return PTR_ERR(tsm);
+ }
+ tsm_report_group = tsm;
+
+ return 0;
+ }
+ module_init(tsm_report_init);
+
+ static void __exit tsm_report_exit(void)
+ {
+ configfs_unregister_default_group(tsm_report_group);
+ configfs_unregister_subsystem(&tsm_configfs);
+ }
+ module_exit(tsm_report_exit);
+
+ MODULE_LICENSE("GPL");
+ MODULE_DESCRIPTION("Provide Trusted Security Module attestation reports via configfs");
projects / ceph-client.git / commitdiff