| Message ID | 20211210154332.11526-40-brijesh.singh@amd.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Add AMD Secure Nested Paging (SEV-SNP) Guest Support | expand |
On 10/12/2021 15:43, Brijesh Singh wrote: > 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 nit: choose -> chooses > sealing key or communicating with the external entities. > > See SEV-SNP firmware spec for more information. > > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > --- > 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 > + Does it return 'struct snp_derived_key_resp' on success? > +The SNP_GET_DERIVED_KEY ioctl can be used to get a key derive from a root key. nit: derive -> derived ? Otherwise Reviewed-by: Liam Merwick <liam.merwick@oracle.com> > +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_ */ >
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_ */
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 <brijesh.singh@amd.com> --- 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(+)