The following commit has been merged into the x86/sev branch of tip: Commit-ID: d80b494f712317493d464a55652698c4d1b7bb0f Gitweb: https://git.kernel.org/tip/d80b494f712317493d464a55652698c4d1b7bb0f Author: Brijesh Singh <brijesh.singh@xxxxxxx> AuthorDate: Mon, 07 Mar 2022 15:33:55 -06:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Thu, 07 Apr 2022 16:47:12 +02:00 virt: sevguest: Add support to get extended report Version 2 of GHCB specification defines Non-Automatic-Exit (NAE) to get extended guest report which is similar to the SNP_GET_REPORT ioctl. The main difference is related to the additional data that will be returned. That additional data returned is a certificate blob that can be used by the SNP guest user. The certificate blob layout is defined in the GHCB specification. The driver simply treats the blob as a opaque data and copies it to userspace. [ bp: Massage commit message, cast 1st arg of access_ok() ] Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lore.kernel.org/r/20220307213356.2797205-46-brijesh.singh@xxxxxxx --- Documentation/virt/coco/sevguest.rst | 23 +++++++- drivers/virt/coco/sevguest/sevguest.c | 92 +++++++++++++++++++++++++- include/uapi/linux/sev-guest.h | 13 ++++- 3 files changed, 126 insertions(+), 2 deletions(-) diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst index 4135c14..625de22 100644 --- a/Documentation/virt/coco/sevguest.rst +++ b/Documentation/virt/coco/sevguest.rst @@ -95,6 +95,29 @@ on the various fields passed in the key derivation request. On success, the snp_derived_key_resp.data contains the derived key value. See the SEV-SNP specification for further details. + +2.3 SNP_GET_EXT_REPORT +---------------------- +:Technology: sev-snp +:Type: guest ioctl +:Parameters (in/out): struct snp_ext_report_req +:Returns (out): struct snp_report_resp on success, -negative on error + +The SNP_GET_EXT_REPORT ioctl is similar to the SNP_GET_REPORT. The difference is +related to the additional certificate data that is returned with the report. +The certificate data returned is being provided by the hypervisor through the +SNP_SET_EXT_CONFIG. + +The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command provided by the SEV-SNP +firmware to get the attestation report. + +On success, the snp_ext_report_resp.data will contain the attestation report +and snp_ext_report_req.certs_address will contain the certificate blob. If the +length of the blob is smaller than expected then snp_ext_report_req.certs_len will +be updated with the expected value. + +See GHCB specification for further detail on how to parse the certificate blob. + Reference --------- diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c index 393777b..15afb6c 100644 --- a/drivers/virt/coco/sevguest/sevguest.c +++ b/drivers/virt/coco/sevguest/sevguest.c @@ -43,6 +43,7 @@ struct snp_guest_dev { struct device *dev; struct miscdevice misc; + void *certs_data; struct snp_guest_crypto *crypto; struct snp_guest_msg *request, *response; struct snp_secrets_page_layout *layout; @@ -433,6 +434,82 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque return rc; } +static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg) +{ + struct snp_guest_crypto *crypto = snp_dev->crypto; + struct snp_ext_report_req req; + struct snp_report_resp *resp; + int ret, npages = 0, resp_len; + + lockdep_assert_held(&snp_cmd_mutex); + + if (!arg->req_data || !arg->resp_data) + return -EINVAL; + + if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req))) + return -EFAULT; + + /* userspace does not want certificate data */ + if (!req.certs_len || !req.certs_address) + goto cmd; + + if (req.certs_len > SEV_FW_BLOB_MAX_SIZE || + !IS_ALIGNED(req.certs_len, PAGE_SIZE)) + return -EINVAL; + + if (!access_ok((const void __user *)req.certs_address, req.certs_len)) + return -EFAULT; + + /* + * Initialize the intermediate buffer with all zeros. This buffer + * is used in the guest request message to get the certs blob from + * the host. If host does not supply any certs in it, then copy + * zeros to indicate that certificate data was not provided. + */ + memset(snp_dev->certs_data, 0, req.certs_len); + npages = req.certs_len >> PAGE_SHIFT; +cmd: + /* + * The intermediate response buffer is used while decrypting the + * response payload. Make sure that it has enough space to cover the + * authtag. + */ + resp_len = sizeof(resp->data) + crypto->a_len; + resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT); + if (!resp) + return -ENOMEM; + + snp_dev->input.data_npages = npages; + ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version, + SNP_MSG_REPORT_REQ, &req.data, + sizeof(req.data), resp->data, resp_len, &arg->fw_err); + + /* If certs length is invalid then copy the returned length */ + if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) { + req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT; + + if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req))) + ret = -EFAULT; + } + + if (ret) + goto e_free; + + if (npages && + copy_to_user((void __user *)req.certs_address, snp_dev->certs_data, + req.certs_len)) { + ret = -EFAULT; + goto e_free; + } + + if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp))) + ret = -EFAULT; + +e_free: + kfree(resp); + return ret; +} + static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) { struct snp_guest_dev *snp_dev = to_snp_dev(file); @@ -465,6 +542,9 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long case SNP_GET_DERIVED_KEY: ret = get_derived_key(snp_dev, &input); break; + case SNP_GET_EXT_REPORT: + ret = get_ext_report(snp_dev, &input); + break; default: break; } @@ -595,10 +675,14 @@ static int __init snp_guest_probe(struct platform_device *pdev) if (!snp_dev->response) goto e_free_request; + snp_dev->certs_data = alloc_shared_pages(SEV_FW_BLOB_MAX_SIZE); + if (!snp_dev->certs_data) + goto e_free_response; + ret = -EIO; snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN); if (!snp_dev->crypto) - goto e_free_response; + goto e_free_cert_data; misc = &snp_dev->misc; misc->minor = MISC_DYNAMIC_MINOR; @@ -608,14 +692,17 @@ static int __init snp_guest_probe(struct platform_device *pdev) /* initial the input address for guest request */ snp_dev->input.req_gpa = __pa(snp_dev->request); snp_dev->input.resp_gpa = __pa(snp_dev->response); + snp_dev->input.data_gpa = __pa(snp_dev->certs_data); ret = misc_register(misc); if (ret) - goto e_free_response; + goto e_free_cert_data; dev_info(dev, "Initialized SNP guest driver (using vmpck_id %d)\n", vmpck_id); return 0; +e_free_cert_data: + free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE); e_free_response: free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg)); e_free_request: @@ -629,6 +716,7 @@ static int __exit snp_guest_remove(struct platform_device *pdev) { struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev); + free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE); free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg)); free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg)); deinit_crypto(snp_dev->crypto); diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h index 598367f..256aaef 100644 --- a/include/uapi/linux/sev-guest.h +++ b/include/uapi/linux/sev-guest.h @@ -56,6 +56,16 @@ struct snp_guest_request_ioctl { __u64 fw_err; }; +struct snp_ext_report_req { + struct snp_report_req data; + + /* where to copy the certificate blob */ + __u64 certs_address; + + /* length of the certificate blob */ + __u32 certs_len; +}; + #define SNP_GUEST_REQ_IOC_TYPE 'S' /* Get SNP attestation report */ @@ -64,4 +74,7 @@ struct snp_guest_request_ioctl { /* Get a derived key from the root */ #define SNP_GET_DERIVED_KEY _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x1, struct snp_guest_request_ioctl) +/* Get SNP extended report as defined in the GHCB specification version 2. */ +#define SNP_GET_EXT_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x2, struct snp_guest_request_ioctl) + #endif /* __UAPI_LINUX_SEV_GUEST_H_ */
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