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David Alan Gilbert" , , , , , Brijesh Singh , Liam Merwick Subject: [PATCH v12 44/46] virt: sevguest: Add support to derive key Date: Mon, 7 Mar 2022 15:33:54 -0600 Message-ID: <20220307213356.2797205-45-brijesh.singh@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220307213356.2797205-1-brijesh.singh@amd.com> References: <20220307213356.2797205-1-brijesh.singh@amd.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: d0a51855-269d-4f3e-0139-08da00826b82 X-MS-TrafficTypeDiagnostic: MWHPR12MB1693:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: JpHOIPNhUqJfenDoAFghIkOAW2OEI2F5wvC4CJKWmnwbUHPdgHSy/HqVAR/rT7FEbl66HK+ge/qbrr/lPYvDGZ/+SDRtkvJh3TVj6izbijU358UPUw7UDvEkpa9LOqG2gGwui0jSbgDWIC84OqpT86clKc5zG3owmLOo+uH5gjzGFFIXC/dkxg/F/qI0j4bp8UwgXNSCEkorD+FssO+dWiBx2KNMgIBIUFHZDQ7V73uzrNmKRD7NAfb9sLDxy5KKC788uiFg6wv+Q/kHfyB3+2speoIfIefoahRhpEpIXG4rBSBwi0K1PFpFF9RpHcuZ1/xDRoWPvNLq9rSysNsXXrO0FZTv8RLGH+FTTqUPfR9K1eIsbajs+AEvd6gBqzjMny7yQdccoMqhnYEcCvGx0VQZBq2QHohZ/MU8YWZ7ZhqiP+qjkoTuHhokhCFCbYOwLs3/Vgu8j0+zkKNNnouvEbXGzrUv066E+of0J+ffLJNLaqm13gRIyRiz3CNYgC4kyviTsFSIEgPeut5DKAx7fTtrAuOaLgzIpOnE19SEQCUHWhRYm2Eux8W7eiunVKM8PKv3tvqKNNQBXZ85olV3ehe2O37ddDzS+/qijb/ZdoPZTHOyvIrIii8NnzqzOXjl9k03NJt3iLax1heUG1X0rou//LB8Y/9jqrafsvtW2Y9uT5Vr+fbHPJSMINNtX0Xqs5C0gbznfxEsNAxCVL0hKTa4a0aQWjtdOHpFB6Zaai8= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230001)(4636009)(46966006)(36840700001)(40470700004)(316002)(26005)(5660300002)(16526019)(7416002)(2616005)(1076003)(7406005)(83380400001)(186003)(426003)(336012)(82310400004)(508600001)(86362001)(54906003)(110136005)(8676002)(4326008)(70586007)(70206006)(7696005)(6666004)(8936002)(36860700001)(36756003)(44832011)(47076005)(40460700003)(2906002)(356005)(81166007)(2101003)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Mar 2022 21:35:37.4683 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d0a51855-269d-4f3e-0139-08da00826b82 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT009.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR12MB1693 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 chooses, such as a sealing key or communicating with the external entities. See SEV-SNP firmware spec for more information. Reviewed-by: Liam Merwick Signed-off-by: Brijesh Singh --- 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 34feff6d5940..ae2e76f59435 100644 --- a/Documentation/virt/coco/sevguest.rst +++ b/Documentation/virt/coco/sevguest.rst @@ -77,6 +77,23 @@ 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_resp 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 97b98a3f5f89..9057e8a661f6 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; + struct snp_derived_key_req req; + int rc, resp_len; + /* Response data is 64 bytes and max authsize for GCM is 16 bytes. */ + u8 buf[64 + 16]; + + lockdep_assert_held(&snp_cmd_mutex); + + if (!arg->req_data || !arg->resp_data) + return -EINVAL; + + /* + * 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; + + if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req))) + return -EFAULT; + + 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) + return rc; + + memcpy(resp.data, buf, sizeof(resp.data)); + if (copy_to_user((void __user *)arg->resp_data, &resp, sizeof(resp))) + rc = -EFAULT; + + /* The response buffer contains the sensitive data, explicitly clear it. */ + 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 38f11d723c68..598367f12064 100644 --- a/include/uapi/linux/sev-guest.h +++ b/include/uapi/linux/sev-guest.h @@ -30,6 +30,20 @@ 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; @@ -47,4 +61,7 @@ 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_ */ -- 2.25.1