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authorBrijesh Singh <brijesh.singh@amd.com>2022-02-24 10:56:23 -0600
committerBorislav Petkov <bp@suse.de>2022-04-07 16:47:12 +0200
commit68de0b2f938642079c0c853b219bdb88c4dc4d13 (patch)
tree47b4e86cd61144bd5fcba09a040c7e958828a31c /drivers/virt
parentfce96cf0443083e37455eff8f78fd240c621dae3 (diff)
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virt: sevguest: Add support to derive key
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. [ bp: No need to memset "req" - it will get overwritten. ] Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Liam Merwick <liam.merwick@oracle.com> Link: https://lore.kernel.org/r/20220307213356.2797205-45-brijesh.singh@amd.com
Diffstat (limited to 'drivers/virt')
-rw-r--r--drivers/virt/coco/sevguest/sevguest.c45
1 files changed, 45 insertions, 0 deletions
diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c
index beda93cdeb4f..393777b72e5e 100644
--- a/drivers/virt/coco/sevguest/sevguest.c
+++ b/drivers/virt/coco/sevguest/sevguest.c
@@ -391,6 +391,48 @@ e_free:
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;
+ /* 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;
}