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David Alan Gilbert" , , , , Brijesh Singh Subject: [PATCH v8 39/40] virt: sevguest: Add support to derive key Date: Fri, 10 Dec 2021 09:43:31 -0600 Message-ID: <20211210154332.11526-40-brijesh.singh@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211210154332.11526-1-brijesh.singh@amd.com> References: <20211210154332.11526-1-brijesh.singh@amd.com> MIME-Version: 1.0 X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB03.amd.com (10.181.40.144) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 15792482-61f5-4ef1-1d69-08d9bbf4019f X-MS-TrafficTypeDiagnostic: BYAPR12MB3317:EE_ X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:2582; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17; CTRY:US; LANG:en; SCL:1; SRV:; IPV:CAL; SFV:NSPM; H:SATLEXMB03.amd.com; PTR:InfoDomainNonexistent; CAT:NONE; SFS:(4636009)(46966006)(36840700001)(40470700001)(40460700001)(8676002)(36756003)(36860700001)(8936002)(86362001)(70206006)(70586007)(186003)(2616005)(83380400001)(356005)(508600001)(82310400004)(47076005)(81166007)(26005)(16526019)(2906002)(5660300002)(44832011)(4326008)(7406005)(1076003)(7416002)(6666004)(54906003)(336012)(316002)(426003)(110136005)(7696005)(2101003)(36900700001); DIR:OUT; SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Dec 2021 15:44:52.2830 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 15792482-61f5-4ef1-1d69-08d9bbf4019f X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d; Ip=[165.204.84.17]; Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT055.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB3317 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org The SNP_GET_DERIVED_KEY ioctl interface can be used by the SNP guest to ask the firmware to provide a key derived from a root key. The derived key may be used by the guest for any purposes it choose, such as a sealing key or communicating with the external entities. See SEV-SNP firmware spec for more information. Signed-off-by: Brijesh Singh Reviewed-by: Liam Merwick --- Documentation/virt/coco/sevguest.rst | 17 ++++++++++ drivers/virt/coco/sevguest/sevguest.c | 45 +++++++++++++++++++++++++++ include/uapi/linux/sev-guest.h | 17 ++++++++++ 3 files changed, 79 insertions(+) diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst index 47ef3b0821d5..8c22d514d44f 100644 --- a/Documentation/virt/coco/sevguest.rst +++ b/Documentation/virt/coco/sevguest.rst @@ -72,6 +72,23 @@ On success, the snp_report_resp.data will contains the report. The report contain the format described in the SEV-SNP specification. See the SEV-SNP specification for further details. +2.2 SNP_GET_DERIVED_KEY +----------------------- +:Technology: sev-snp +:Type: guest ioctl +:Parameters (in): struct snp_derived_key_req +:Returns (out): struct snp_derived_key_req on success, -negative on error + +The SNP_GET_DERIVED_KEY ioctl can be used to get a key derive from a root key. +The derived key can be used by the guest for any purpose, such as sealing keys +or communicating with external entities. + +The ioctl uses the SNP_GUEST_REQUEST (MSG_KEY_REQ) command provided by the +SEV-SNP firmware to derive the key. See SEV-SNP specification for further details +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. Reference --------- diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c index b3b080c9b2d6..d8dcafc32e11 100644 --- a/drivers/virt/coco/sevguest/sevguest.c +++ b/drivers/virt/coco/sevguest/sevguest.c @@ -391,6 +391,48 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io return rc; } +static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg) +{ + struct snp_guest_crypto *crypto = snp_dev->crypto; + struct snp_derived_key_resp resp = {0}; + struct snp_derived_key_req req; + int rc, resp_len; + u8 buf[64+16]; /* Response data is 64 bytes and max authsize for GCM is 16 bytes */ + + if (!arg->req_data || !arg->resp_data) + return -EINVAL; + + /* Copy the request payload from userspace */ + if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req))) + return -EFAULT; + + /* + * 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; + if (sizeof(buf) < resp_len) + return -ENOMEM; + + /* Issue the command to get the attestation report */ + rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version, + SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len, + &arg->fw_err); + if (rc) + goto e_free; + + /* Copy the response payload to userspace */ + memcpy(resp.data, buf, sizeof(resp.data)); + if (copy_to_user((void __user *)arg->resp_data, &resp, sizeof(resp))) + rc = -EFAULT; + +e_free: + memzero_explicit(buf, sizeof(buf)); + memzero_explicit(&resp, sizeof(resp)); + return rc; +} + static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) { struct snp_guest_dev *snp_dev = to_snp_dev(file); @@ -420,6 +462,9 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long case SNP_GET_REPORT: ret = get_report(snp_dev, &input); break; + case SNP_GET_DERIVED_KEY: + ret = get_derived_key(snp_dev, &input); + break; default: break; } diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h index 0bfc162da465..ce595539e00c 100644 --- a/include/uapi/linux/sev-guest.h +++ b/include/uapi/linux/sev-guest.h @@ -27,6 +27,20 @@ struct snp_report_resp { __u8 data[4000]; }; +struct snp_derived_key_req { + __u32 root_key_select; + __u32 rsvd; + __u64 guest_field_select; + __u32 vmpl; + __u32 guest_svn; + __u64 tcb_version; +}; + +struct snp_derived_key_resp { + /* response data, see SEV-SNP spec for the format */ + __u8 data[64]; +}; + struct snp_guest_request_ioctl { /* message version number (must be non-zero) */ __u8 msg_version; @@ -44,4 +58,7 @@ struct snp_guest_request_ioctl { /* Get SNP attestation report */ #define SNP_GET_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x0, 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) + #endif /* __UAPI_LINUX_SEV_GUEST_H_ */