Messages in this thread Patch in this message | | | Subject | [PATCH v3 5/5] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}_REPORT | From | Dan Williams <> | Date | Wed, 30 Aug 2023 12:33:42 -0700 |
| |
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 blobs that the SNP_{GET,GET_EXT}_REPORT ioctls produce. An example flow follows for retrieving the SNP_GET_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 rmdir $report
...while the SNP_GET_EXT_REPORT flow needs to additionally set the format to "extended":
report=/sys/kernel/config/tsm/report/report1 mkdir $report echo extended > $report/format dd if=/dev/urandom bs=64 count=1 > $report/inblob hexdump -C $report/outblob rmdir $report
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.
Note, only compile-tested.
Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1] Cc: Borislav Petkov <bp@alien8.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Dionna Glaze <dionnaglaze@google.com> Cc: Brijesh Singh <brijesh.singh@amd.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- drivers/virt/coco/sev-guest/Kconfig | 1 drivers/virt/coco/sev-guest/sev-guest.c | 83 +++++++++++++++++++++++++++++++ 2 files changed, 84 insertions(+)
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 c3c9e9ea691f..c7bbb8f372a3 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -16,10 +16,12 @@ #include <linux/miscdevice.h> #include <linux/set_memory.h> #include <linux/fs.h> +#include <linux/tsm.h> #include <crypto/aead.h> #include <linux/scatterlist.h> #include <linux/psp-sev.h> #include <linux/sockptr.h> +#include <linux/cleanup.h> #include <uapi/linux/sev-guest.h> #include <uapi/linux/psp-sev.h> @@ -759,6 +761,79 @@ static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno return key; } +static u8 *sev_report_new(const struct tsm_desc *desc, void *data, size_t *outblob_len) +{ + struct snp_guest_dev *snp_dev = data; + const int report_size = SZ_4K; + const int ext_size = SZ_16K; + int ret, size; + + if (desc->inblob_len != 64) + return ERR_PTR(-EINVAL); + + if (desc->outblob_format == TSM_FORMAT_EXTENDED) + size = report_size + ext_size; + else + size = report_size; + + u8 *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL); + + guard(mutex)(&snp_cmd_mutex); + if (desc->outblob_format == TSM_FORMAT_EXTENDED) { + struct snp_ext_report_req ext_req = { + .data = { .vmpl = desc->privlevel }, + .certs_address = (__u64)buf + report_size, + .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, + }; + struct snp_req_resp io = { + .req_data = KERNEL_SOCKPTR(&ext_req), + .resp_data = KERNEL_SOCKPTR(buf), + }; + + ret = get_ext_report(snp_dev, &input, &io); + } else { + struct snp_report_req req = { + .vmpl = desc->privlevel, + }; + memcpy(&req.user_data, desc->inblob, desc->inblob_len); + + struct snp_guest_request_ioctl input = { + .msg_version = 1, + .req_data = (__u64)&req, + .resp_data = (__u64)buf, + }; + struct snp_req_resp io = { + .req_data = KERNEL_SOCKPTR(&req), + .resp_data = KERNEL_SOCKPTR(buf), + }; + + ret = get_report(snp_dev, &input, &io); + } + + if (ret) + return ERR_PTR(ret); + + *outblob_len = size; + return_ptr(buf); +} + +static const struct tsm_ops sev_tsm_ops = { + .name = KBUILD_MODNAME, + .report_new = sev_report_new, +}; + +static void unregister_sev_tsm(void *data) +{ + unregister_tsm(&sev_tsm_ops); +} + static int __init sev_guest_probe(struct platform_device *pdev) { struct snp_secrets_page_layout *layout; @@ -832,6 +907,14 @@ 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 = register_tsm(&sev_tsm_ops, snp_dev, &tsm_report_ext_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;
| |