diff --git a/Documentation/ABI/testing/configfs-tsm b/Documentation/ABI/testing/configfs-tsm new file mode 100644 index 000000000000..dd24202b5ba5 --- /dev/null +++ b/Documentation/ABI/testing/configfs-tsm @@ -0,0 +1,82 @@ +What: /sys/kernel/config/tsm/report/$name/inblob +Date: September, 2023 +KernelVersion: v6.7 +Contact: linux-coco@lists.linux.dev +Description: + (WO) Up to 64 bytes of user specified binary data. For replay + protection this should include a nonce, but the kernel does not + place any restrictions on the content. + +What: /sys/kernel/config/tsm/report/$name/outblob +Date: September, 2023 +KernelVersion: v6.7 +Contact: linux-coco@lists.linux.dev +Description: + (RO) Binary attestation report generated from @inblob and other + options The format of the report is implementation specific + where the implementation is conveyed via the @provider + attribute. + +What: /sys/kernel/config/tsm/report/$name/auxblob +Date: October, 2023 +KernelVersion: v6.7 +Contact: linux-coco@lists.linux.dev +Description: + (RO) Optional supplemental data that a TSM may emit, visibility + of this attribute depends on TSM, and may be empty if no + auxiliary data is available. + + When @provider is "sev_guest" this file contains the + "cert_table" from SEV-ES Guest-Hypervisor Communication Block + Standardization v2.03 Section 4.1.8.1 MSG_REPORT_REQ. + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf + +What: /sys/kernel/config/tsm/report/$name/provider +Date: September, 2023 +KernelVersion: v6.7 +Contact: linux-coco@lists.linux.dev +Description: + (RO) A name for the format-specification of @outblob like + "sev_guest" [1] or "tdx_guest" [2] in the near term, or a + common standard format in the future. + + [1]: SEV Secure Nested Paging Firmware ABI Specification + Revision 1.55 Table 22 + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56860.pdf + + [2]: Intel® Trust Domain Extensions Data Center Attestation + Primitives : Quote Generation Library and Quote Verification + Library Revision 0.8 Appendix 4,5 + https://download.01.org/intel-sgx/latest/dcap-latest/linux/docs/Intel_TDX_DCAP_Quoting_Library_API.pdf + +What: /sys/kernel/config/tsm/report/$name/generation +Date: September, 2023 +KernelVersion: v6.7 +Contact: linux-coco@lists.linux.dev +Description: + (RO) The value in this attribute increments each time @inblob or + any option is written. Userspace can detect conflicts by + checking generation before writing to any attribute and making + sure the number of writes matches expectations after reading + @outblob, or it can prevent conflicts by creating a report + instance per requesting context. + +What: /sys/kernel/config/tsm/report/$name/privlevel +Date: September, 2023 +KernelVersion: v6.7 +Contact: linux-coco@lists.linux.dev +Description: + (WO) Attribute is visible if a TSM implementation provider + supports the concept of attestation reports for TVMs running at + different privilege levels, like SEV-SNP "VMPL", specify the + privilege level via this attribute. The minimum acceptable + value is conveyed via @privlevel_floor and the maximum + acceptable value is TSM_PRIVLEVEL_MAX (3). + +What: /sys/kernel/config/tsm/report/$name/privlevel_floor +Date: September, 2023 +KernelVersion: v6.7 +Contact: linux-coco@lists.linux.dev +Description: + (RO) Indicates the minimum permissible value that can be written + to @privlevel. diff --git a/MAINTAINERS b/MAINTAINERS index b19995690904..8acbeb029ba1 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -21889,6 +21889,14 @@ W: https://github.com/srcres258/linux-doc T: git git://github.com/srcres258/linux-doc.git doc-zh-tw F: Documentation/translations/zh_TW/ +TRUSTED SECURITY MODULE (TSM) ATTESTATION REPORTS +M: Dan Williams +L: linux-coco@lists.linux.dev +S: Maintained +F: Documentation/ABI/testing/configfs-tsm +F: drivers/virt/coco/tsm.c +F: include/linux/tsm.h + TTY LAYER AND SERIAL DRIVERS M: Greg Kroah-Hartman M: Jiri Slaby diff --git a/drivers/virt/coco/Kconfig b/drivers/virt/coco/Kconfig index fc5c64f04c4a..87d142c1f932 100644 --- a/drivers/virt/coco/Kconfig +++ b/drivers/virt/coco/Kconfig @@ -2,6 +2,11 @@ # # Confidential computing related collateral # + +config TSM_REPORTS + select CONFIGFS_FS + tristate + source "drivers/virt/coco/efi_secret/Kconfig" source "drivers/virt/coco/sev-guest/Kconfig" diff --git a/drivers/virt/coco/Makefile b/drivers/virt/coco/Makefile index 55302ef719ad..18c1aba5edb7 100644 --- a/drivers/virt/coco/Makefile +++ b/drivers/virt/coco/Makefile @@ -2,6 +2,7 @@ # # Confidential computing related collateral # +obj-$(CONFIG_TSM_REPORTS) += tsm.o obj-$(CONFIG_EFI_SECRET) += efi_secret/ obj-$(CONFIG_SEV_GUEST) += sev-guest/ obj-$(CONFIG_INTEL_TDX_GUEST) += tdx-guest/ diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c new file mode 100644 index 000000000000..d1c2db83a8ca --- /dev/null +++ b/drivers/virt/coco/tsm.c @@ -0,0 +1,425 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright(c) 2023 Intel Corporation. All rights reserved. */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include + +static struct tsm_provider { + const struct tsm_ops *ops; + const struct config_item_type *type; + void *data; +} 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'. + */ + +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, +}; + +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; + + /* + * 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_PRIVLEVEL_MAX) + return -EINVAL; + + guard(rwsem_write)(&tsm_rwsem); + 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); + return sysfs_emit(buf, "%u\n", provider.ops->privlevel_floor); +} +CONFIGFS_ATTR_RO(tsm_report_, privlevel_floor); + +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_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); + 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 { + 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 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_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 -ENOTTY; + 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); + report->outblob = NULL; + report->auxblob = 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_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_OUTBLOB_MAX); + +#define TSM_DEFAULT_ATTRS() \ + &tsm_report_attr_generation, \ + &tsm_report_attr_provider + +static struct configfs_attribute *tsm_report_attrs[] = { + TSM_DEFAULT_ATTRS(), + NULL, +}; + +static struct configfs_attribute *tsm_report_extra_attrs[] = { + TSM_DEFAULT_ATTRS(), + &tsm_report_attr_privlevel, + &tsm_report_attr_privlevel_floor, + NULL, +}; + +#define TSM_DEFAULT_BIN_ATTRS() \ + &tsm_report_attr_inblob, \ + &tsm_report_attr_outblob + +static struct configfs_bin_attribute *tsm_report_bin_attrs[] = { + TSM_DEFAULT_BIN_ATTRS(), + NULL, +}; + +static struct configfs_bin_attribute *tsm_report_bin_extra_attrs[] = { + TSM_DEFAULT_BIN_ATTRS(), + &tsm_report_attr_auxblob, + 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->auxblob); + kvfree(report->outblob); + kfree(state); +} + +static struct configfs_item_operations tsm_report_item_ops = { + .release = tsm_report_item_release, +}; + +const struct config_item_type tsm_report_default_type = { + .ct_owner = THIS_MODULE, + .ct_bin_attrs = tsm_report_bin_attrs, + .ct_attrs = tsm_report_attrs, + .ct_item_ops = &tsm_report_item_ops, +}; +EXPORT_SYMBOL_GPL(tsm_report_default_type); + +const struct config_item_type tsm_report_extra_type = { + .ct_owner = THIS_MODULE, + .ct_bin_attrs = tsm_report_bin_extra_attrs, + .ct_attrs = tsm_report_extra_attrs, + .ct_item_ops = &tsm_report_item_ops, +}; +EXPORT_SYMBOL_GPL(tsm_report_extra_type); + +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); + + config_item_init_type_name(&state->cfg, name, provider.type); + return &state->cfg; +} + +static struct configfs_group_operations tsm_report_group_ops = { + .make_item = tsm_report_make_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_register(const struct tsm_ops *ops, void *priv, + const struct config_item_type *type) +{ + const struct tsm_ops *conflict; + + if (!type) + type = &tsm_report_default_type; + if (!(type == &tsm_report_default_type || type == &tsm_report_extra_type)) + return -EINVAL; + + guard(rwsem_write)(&tsm_rwsem); + conflict = provider.ops; + if (conflict) { + pr_err("\"%s\" ops already registered\n", conflict->name); + return -EBUSY; + } + + provider.ops = ops; + provider.data = priv; + provider.type = type; + return 0; +} +EXPORT_SYMBOL_GPL(tsm_register); + +int tsm_unregister(const struct tsm_ops *ops) +{ + guard(rwsem_write)(&tsm_rwsem); + if (ops != provider.ops) + return -EBUSY; + provider.ops = NULL; + provider.data = NULL; + provider.type = NULL; + return 0; +} +EXPORT_SYMBOL_GPL(tsm_unregister); + +static struct config_group *tsm_report_group; + +static int __init tsm_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_init); + +static void __exit tsm_exit(void) +{ + configfs_unregister_default_group(tsm_report_group); + configfs_unregister_subsystem(&tsm_configfs); +} +module_exit(tsm_exit); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Provide Trusted Security Module attestation reports via configfs"); diff --git a/include/linux/tsm.h b/include/linux/tsm.h new file mode 100644 index 000000000000..de8324a2223c --- /dev/null +++ b/include/linux/tsm.h @@ -0,0 +1,69 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __TSM_H +#define __TSM_H + +#include +#include + +#define TSM_INBLOB_MAX 64 +#define TSM_OUTBLOB_MAX SZ_32K + +/* + * Privilege level is a nested permission concept to allow confidential + * guests to partition address space, 4-levels are supported. + */ +#define TSM_PRIVLEVEL_MAX 3 + +/** + * struct tsm_desc - option descriptor for generating tsm report blobs + * @privlevel: optional privilege level to associate with @outblob + * @inblob_len: sizeof @inblob + * @inblob: arbitrary input data + */ +struct tsm_desc { + unsigned int privlevel; + size_t inblob_len; + u8 inblob[TSM_INBLOB_MAX]; +}; + +/** + * struct tsm_report - track state of report generation relative to options + * @desc: input parameters to @report_new() + * @outblob_len: sizeof(@outblob) + * @outblob: generated evidence to provider to the attestation agent + * @auxblob_len: sizeof(@auxblob) + * @auxblob: (optional) auxiliary data to the report (e.g. certificate data) + */ +struct tsm_report { + struct tsm_desc desc; + size_t outblob_len; + u8 *outblob; + size_t auxblob_len; + u8 *auxblob; +}; + +/** + * struct tsm_ops - attributes and operations for tsm instances + * @name: tsm id reflected in /sys/kernel/config/tsm/report/$report/provider + * @privlevel_floor: convey base privlevel for nested scenarios + * @report_new: Populate @report with the report blob and auxblob + * (optional), return 0 on successful population, or -errno otherwise + * + * Implementation specific ops, only one is expected to be registered at + * a time i.e. only one of "sev-guest", "tdx-guest", etc. + */ +struct tsm_ops { + const char *name; + const unsigned int privlevel_floor; + int (*report_new)(struct tsm_report *report, void *data); +}; + +extern const struct config_item_type tsm_report_default_type; + +/* publish @privlevel, @privlevel_floor, and @auxblob attributes */ +extern const struct config_item_type tsm_report_extra_type; + +int tsm_register(const struct tsm_ops *ops, void *priv, + const struct config_item_type *type); +int tsm_unregister(const struct tsm_ops *ops); +#endif /* __TSM_H */