From 70e6f7e2b98575621019aa40ac616be58ff984e0 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 25 Sep 2023 20:13:29 -0700 Subject: configfs-tsm: Introduce a shared ABI for attestation reports One of the common operations of a TSM (Trusted Security Module) is to provide a way for a TVM (confidential computing guest execution environment) to take a measurement of its launch state, sign it and submit it to a verifying party. Upon successful attestation that verifies the integrity of the TVM additional secrets may be deployed. The concept is common across TSMs, but the implementations are unfortunately vendor specific. While the industry grapples with a common definition of this attestation format [1], Linux need not make this problem worse by defining a new ABI per TSM that wants to perform a similar operation. The current momentum has been to invent new ioctl-ABI per TSM per function which at best is an abdication of the kernel's responsibility to make common infrastructure concepts share common ABI. The proposal, targeted to conceptually work with TDX, SEV-SNP, COVE if not more, is to define a configfs interface to retrieve the TSM-specific blob. report=/sys/kernel/config/tsm/report/report0 mkdir $report dd if=binary_userdata_plus_nonce > $report/inblob hexdump $report/outblob This approach later allows for the standardization of the attestation blob format without needing to invent a new ABI. Once standardization happens the standard format can be emitted by $report/outblob and indicated by $report/provider, or a new attribute like "$report/tcg_coco_report" can emit the standard format alongside the vendor format. Review of previous iterations of this interface identified that there is a need to scale report generation for multiple container environments [2]. Configfs enables a model where each container can bind mount one or more report generation item instances. Still, within a container only a single thread can be manipulating a given configuration instance at a time. A 'generation' count is provided to detect conflicts between multiple threads racing to configure a report instance. The SEV-SNP concepts of "extended reports" and "privilege levels" are optionally enabled by selecting 'tsm_report_ext_type' at register_tsm() time. The expectation is that those concepts are generic enough that they may be adopted by other TSM implementations. In other words, configfs-tsm aims to address a superset of TSM specific functionality with a common ABI where attributes may appear, or not appear, based on the set of concepts the implementation supports. Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1] Link: http://lore.kernel.org/r/57f3a05e-8fcd-4656-beea-56bb8365ae64@linux.microsoft.com [2] Cc: Kuppuswamy Sathyanarayanan Cc: Dionna Amalie Glaze Cc: James Bottomley Cc: Peter Gonda Cc: Greg Kroah-Hartman Cc: Samuel Ortiz Acked-by: Greg Kroah-Hartman Acked-by: Thomas Gleixner Reviewed-by: Kuppuswamy Sathyanarayanan Tested-by: Kuppuswamy Sathyanarayanan Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams --- include/linux/tsm.h | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) create mode 100644 include/linux/tsm.h (limited to 'include') 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 */ -- cgit v1.2.3 From a67d74a4b163878a3c0537033ed1b20db92ebfc5 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Wed, 19 Jul 2023 18:14:13 -0700 Subject: mm/slab: Add __free() support for kvfree Allow for the declaration of variables that trigger kvfree() when they go out of scope. The check for NULL and call to kvfree() can be elided by the compiler in most cases, otherwise without the NULL check an unnecessary call to kvfree() may be emitted. Peter proposed a comment for this detail [1]. Link: http://lore.kernel.org/r/20230816103102.GF980931@hirez.programming.kicks-ass.net [1] Cc: Andrew Morton Cc: Peter Zijlstra Cc: Greg Kroah-Hartman Acked-by: Pankaj Gupta Acked-by: Greg Kroah-Hartman Reviewed-by: Kuppuswamy Sathyanarayanan Tested-by: Kuppuswamy Sathyanarayanan Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams --- include/linux/slab.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/slab.h b/include/linux/slab.h index 8228d1276a2f..df4c2d45bb86 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -763,6 +763,8 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags) __realloc_size(3); extern void kvfree(const void *addr); +DEFINE_FREE(kvfree, void *, if (_T) kvfree(_T)) + extern void kvfree_sensitive(const void *addr, size_t len); unsigned int kmem_cache_size(struct kmem_cache *s); -- cgit v1.2.3 From f47906782c76294b3468f7584f666bc114927aa1 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Tue, 10 Oct 2023 20:03:19 -0700 Subject: virt: sevguest: Add TSM_REPORTS support for SNP_GET_EXT_REPORT The sevguest driver was a first mover in the confidential computing space. As a first mover that afforded some leeway to build the driver without concern for common infrastructure. Now that sevguest is no longer a singleton [1] the common operation of building and transmitting attestation report blobs can / should be made common. In this model the so called "TSM-provider" implementations can share a common envelope ABI even if the contents of that envelope remain vendor-specific. When / if the industry agrees on an attestation record format, that definition can also fit in the same ABI. In the meantime the kernel's maintenance burden is reduced and collaboration on the commons is increased. Convert sevguest to use CONFIG_TSM_REPORTS to retrieve the data that the SNP_GET_EXT_REPORT ioctl produces. An example flow follows for retrieving the report blob via the TSM interface utility, assuming no nonce and VMPL==2: report=/sys/kernel/config/tsm/report/report0 mkdir $report echo 2 > $report/privlevel dd if=/dev/urandom bs=64 count=1 > $report/inblob hexdump -C $report/outblob # SNP report hexdump -C $report/auxblob # cert_table rmdir $report Given that the platform implementation is free to return empty certificate data if none is available it lets configfs-tsm be simplified as it only needs to worry about wrapping SNP_GET_EXT_REPORT, and leave SNP_GET_REPORT alone. The old ioctls can be lazily deprecated, the main motivation of this effort is to stop the proliferation of new ioctls, and to increase cross-vendor collaboration. Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1] Cc: Borislav Petkov Cc: Tom Lendacky Cc: Dionna Glaze Cc: Jeremi Piotrowski Tested-by: Kuppuswamy Sathyanarayanan Tested-by: Alexey Kardashevskiy Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams --- drivers/virt/coco/sev-guest/Kconfig | 1 + drivers/virt/coco/sev-guest/sev-guest.c | 135 ++++++++++++++++++++++++++++++++ include/uapi/linux/psp-sev.h | 1 + include/uapi/linux/sev-guest.h | 4 +- 4 files changed, 140 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/drivers/virt/coco/sev-guest/Kconfig b/drivers/virt/coco/sev-guest/Kconfig index da2d7ca531f0..1cffc72c41cb 100644 --- a/drivers/virt/coco/sev-guest/Kconfig +++ b/drivers/virt/coco/sev-guest/Kconfig @@ -5,6 +5,7 @@ config SEV_GUEST select CRYPTO select CRYPTO_AEAD2 select CRYPTO_GCM + select TSM_REPORTS help SEV-SNP firmware provides the guest a mechanism to communicate with the PSP without risk from a malicious hypervisor who wishes to read, diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c index e5f8f115f4af..bc564adcf499 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -16,10 +16,13 @@ #include #include #include +#include #include #include #include #include +#include +#include #include #include @@ -768,6 +771,130 @@ static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno return key; } +struct snp_msg_report_resp_hdr { + u32 status; + u32 report_size; + u8 rsvd[24]; +}; + +struct snp_msg_cert_entry { + guid_t guid; + u32 offset; + u32 length; +}; + +static int sev_report_new(struct tsm_report *report, void *data) +{ + struct snp_msg_cert_entry *cert_table; + struct tsm_desc *desc = &report->desc; + struct snp_guest_dev *snp_dev = data; + struct snp_msg_report_resp_hdr hdr; + const u32 report_size = SZ_4K; + const u32 ext_size = SEV_FW_BLOB_MAX_SIZE; + u32 certs_size, i, size = report_size + ext_size; + int ret; + + if (desc->inblob_len != SNP_REPORT_USER_DATA_SIZE) + return -EINVAL; + + void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + guard(mutex)(&snp_cmd_mutex); + + /* Check if the VMPCK is not empty */ + if (is_vmpck_empty(snp_dev)) { + dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n"); + return -ENOTTY; + } + + cert_table = buf + report_size; + struct snp_ext_report_req ext_req = { + .data = { .vmpl = desc->privlevel }, + .certs_address = (__u64)cert_table, + .certs_len = ext_size, + }; + memcpy(&ext_req.data.user_data, desc->inblob, desc->inblob_len); + + struct snp_guest_request_ioctl input = { + .msg_version = 1, + .req_data = (__u64)&ext_req, + .resp_data = (__u64)buf, + .exitinfo2 = 0xff, + }; + struct snp_req_resp io = { + .req_data = KERNEL_SOCKPTR(&ext_req), + .resp_data = KERNEL_SOCKPTR(buf), + }; + + ret = get_ext_report(snp_dev, &input, &io); + if (ret) + return ret; + + memcpy(&hdr, buf, sizeof(hdr)); + if (hdr.status == SEV_RET_INVALID_PARAM) + return -EINVAL; + if (hdr.status == SEV_RET_INVALID_KEY) + return -EINVAL; + if (hdr.status) + return -ENXIO; + if ((hdr.report_size + sizeof(hdr)) > report_size) + return -ENOMEM; + + void *rbuf __free(kvfree) = kvzalloc(hdr.report_size, GFP_KERNEL); + if (!rbuf) + return -ENOMEM; + + memcpy(rbuf, buf + sizeof(hdr), hdr.report_size); + report->outblob = no_free_ptr(rbuf); + report->outblob_len = hdr.report_size; + + certs_size = 0; + for (i = 0; i < ext_size / sizeof(struct snp_msg_cert_entry); i++) { + struct snp_msg_cert_entry *ent = &cert_table[i]; + + if (guid_is_null(&ent->guid) && !ent->offset && !ent->length) + break; + certs_size = max(certs_size, ent->offset + ent->length); + } + + /* Suspicious that the response populated entries without populating size */ + if (!certs_size && i) + dev_warn_ratelimited(snp_dev->dev, "certificate slots conveyed without size\n"); + + /* No certs to report */ + if (!certs_size) + return 0; + + /* Suspicious that the certificate blob size contract was violated + */ + if (certs_size > ext_size) { + dev_warn_ratelimited(snp_dev->dev, "certificate data truncated\n"); + certs_size = ext_size; + } + + void *cbuf __free(kvfree) = kvzalloc(certs_size, GFP_KERNEL); + if (!cbuf) + return -ENOMEM; + + memcpy(cbuf, cert_table, certs_size); + report->auxblob = no_free_ptr(cbuf); + report->auxblob_len = certs_size; + + return 0; +} + +static const struct tsm_ops sev_tsm_ops = { + .name = KBUILD_MODNAME, + .report_new = sev_report_new, +}; + +static void unregister_sev_tsm(void *data) +{ + tsm_unregister(&sev_tsm_ops); +} + static int __init sev_guest_probe(struct platform_device *pdev) { struct snp_secrets_page_layout *layout; @@ -841,6 +968,14 @@ static int __init sev_guest_probe(struct platform_device *pdev) snp_dev->input.resp_gpa = __pa(snp_dev->response); snp_dev->input.data_gpa = __pa(snp_dev->certs_data); + ret = tsm_register(&sev_tsm_ops, snp_dev, &tsm_report_extra_type); + if (ret) + goto e_free_cert_data; + + ret = devm_add_action_or_reset(&pdev->dev, unregister_sev_tsm, NULL); + if (ret) + goto e_free_cert_data; + ret = misc_register(misc); if (ret) goto e_free_cert_data; diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h index 1c9da485318f..b44ba7dcdefc 100644 --- a/include/uapi/linux/psp-sev.h +++ b/include/uapi/linux/psp-sev.h @@ -68,6 +68,7 @@ typedef enum { SEV_RET_INVALID_PARAM, SEV_RET_RESOURCE_LIMIT, SEV_RET_SECURE_DATA_INVALID, + SEV_RET_INVALID_KEY = 0x27, SEV_RET_MAX, } sev_ret_code; diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h index 2aa39112cf8d..154a87a1eca9 100644 --- a/include/uapi/linux/sev-guest.h +++ b/include/uapi/linux/sev-guest.h @@ -14,9 +14,11 @@ #include +#define SNP_REPORT_USER_DATA_SIZE 64 + struct snp_report_req { /* user data that should be included in the report */ - __u8 user_data[64]; + __u8 user_data[SNP_REPORT_USER_DATA_SIZE]; /* The vmpl level to be included in the report */ __u32 vmpl; -- cgit v1.2.3