On 04/12/2020 23:31, Brijesh Singh wrote:
The SEV FW >= 0.23 added a new command that can be used to query the
attestation report containing the SHA-256 digest of the guest memory
and VMSA encrypted with the LAUNCH_UPDATE and sign it with the PEK.
Note, we already have a command (LAUNCH_MEASURE) that can be used to
query the SHA-256 digest of the guest memory encrypted through the
LAUNCH_UPDATE. The main difference between previous and this command
is that the report is signed with the PEK and unlike the LAUNCH_MEASURE
command the ATTESATION_REPORT command can be called while the guest
is running.
Add a QMP interface "query-sev-attestation-report" that can be used
to get the report encoded in base64.
Cc: James Bottomley <jejb@xxxxxxxxxxxxx>
Cc: Tom Lendacky <Thomas.Lendacky@xxxxxxx>
Cc: Eric Blake <eblake@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
linux-headers/linux/kvm.h | 8 ++++++
qapi/misc-target.json | 38 +++++++++++++++++++++++++++
target/i386/monitor.c | 6 +++++
target/i386/sev-stub.c | 7 +++++
target/i386/sev.c | 54 +++++++++++++++++++++++++++++++++++++++
target/i386/sev_i386.h | 2 ++
6 files changed, 115 insertions(+)
diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index 56ce14ad20..6d0f8101ba 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -1585,6 +1585,8 @@ enum sev_cmd_id {
KVM_SEV_DBG_ENCRYPT,
/* Guest certificates commands */
KVM_SEV_CERT_EXPORT,
+ /* Attestation report */
+ KVM_SEV_GET_ATTESTATION_REPORT,
KVM_SEV_NR_MAX,
};
@@ -1637,6 +1639,12 @@ struct kvm_sev_dbg {
__u32 len;
};
+struct kvm_sev_attestation_report {
+ __u8 mnonce[16];
+ __u64 uaddr;
+ __u32 len;
+};
+
#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
#define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
#define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
diff --git a/qapi/misc-target.json b/qapi/misc-target.json
index 1e561fa97b..ec6565e6ef 100644
--- a/qapi/misc-target.json
+++ b/qapi/misc-target.json
@@ -267,3 +267,41 @@
##
{ 'command': 'query-gic-capabilities', 'returns': ['GICCapability'],
'if': 'defined(TARGET_ARM)' }
+
+
+##
+# @SevAttestationReport:
+#
+# The struct describes attestation report for a Secure Encrypted Virtualization
+# feature.
+#
+# @data: guest attestation report (base64 encoded)
+#
+#
+# Since: 5.2
+##
+{ 'struct': 'SevAttestationReport',
+ 'data': { 'data': 'str'},
+ 'if': 'defined(TARGET_I386)' }
+
+##
+# @query-sev-attestation-report:
+#
+# This command is used to get the SEV attestation report, and is supported on AMD
+# X86 platforms only.
+#
+# @mnonce: a random 16 bytes of data (it will be included in report)
+#
+# Returns: SevAttestationReport objects.
+#
+# Since: 5.2
+#
+# Example:
+#
+# -> { "execute" : "query-sev-attestation-report", "arguments": { "mnonce": "aaaaaaa" } }
+# <- { "return" : { "data": "aaaaaaaabbbddddd"} }
+#
+##
+{ 'command': 'query-sev-attestation-report', 'data': { 'mnonce': 'str' },
+ 'returns': 'SevAttestationReport',
+ 'if': 'defined(TARGET_I386)' }
diff --git a/target/i386/monitor.c b/target/i386/monitor.c
index 9f9e1c42f4..a4b65f330c 100644
--- a/target/i386/monitor.c
+++ b/target/i386/monitor.c
@@ -729,3 +729,9 @@ SevCapability *qmp_query_sev_capabilities(Error **errp)
{
return sev_get_capabilities(errp);
}
+
+SevAttestationReport *
+qmp_query_sev_attestation_report(const char *mnonce, Error **errp)
+{
+ return sev_get_attestation_report(mnonce, errp);
+}
diff --git a/target/i386/sev-stub.c b/target/i386/sev-stub.c
index 88e3f39a1e..66d16f53d8 100644
--- a/target/i386/sev-stub.c
+++ b/target/i386/sev-stub.c
@@ -49,3 +49,10 @@ SevCapability *sev_get_capabilities(Error **errp)
error_setg(errp, "SEV is not available in this QEMU");
return NULL;
}
+
+SevAttestationReport *
+sev_get_attestation_report(const char *mnonce, Error **errp)
+{
+ error_setg(errp, "SEV is not available in this QEMU");
+ return NULL;
+}
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 93c4d60b82..28958fb71b 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -68,6 +68,7 @@ struct SevGuestState {
#define DEFAULT_GUEST_POLICY 0x1 /* disable debug */
#define DEFAULT_SEV_DEVICE "/dev/sev"
+#define DEFAULT_ATTESATION_REPORT_BUF_SIZE 4096
This is unused.
static SevGuestState *sev_guest;
static Error *sev_mig_blocker;
@@ -490,6 +491,59 @@ out:
return cap;
}
+SevAttestationReport *
+sev_get_attestation_report(const char *mnonce, Error **errp)
+{
+ struct kvm_sev_attestation_report input = {};
+ SevGuestState *sev = sev_guest;
+ SevAttestationReport *report;
+ guchar *data;
+ int err = 0, ret;
+
+ if (!sev_enabled()) {
+ error_setg(errp, "SEV is not enabled");
+ return NULL;
+ }
+
+ /* Verify that user provided random data length */
+ if (strlen(mnonce) != sizeof(input.mnonce)) {
+ error_setg(errp, "Expected mnonce data len %ld got %ld",
+ sizeof(input.mnonce), strlen(mnonce));
+ return NULL;
+ }
+
+ /* Query the report length */
+ ret = sev_ioctl(sev->sev_fd, KVM_SEV_GET_ATTESTATION_REPORT,
+ &input, &err);
+ if (ret < 0) {
+ if (err != SEV_RET_INVALID_LEN) {
+ error_setg(errp, "failed to query the attestation report length "
+ "ret=%d fw_err=%d (%s)", ret, err, fw_error_to_str(err));
+ return NULL;
+ }
+ }
+
+ data = g_malloc(input.len);
+ input.uaddr = (unsigned long)data;
+ memcpy(input.mnonce, mnonce, sizeof(input.mnonce));
+
+ /* Query the report */
+ ret = sev_ioctl(sev->sev_fd, KVM_SEV_GET_ATTESTATION_REPORT,
+ &input, &err);
+ if (ret) {
+ error_setg_errno(errp, errno, "Failed to get attestation report"
+ " ret=%d fw_err=%d (%s)", ret, err, fw_error_to_str(err));
+ goto e_free_data;
James already noted the missing `report = NULL` here. Another option is
to avoid the goto entirely and use qemu's g_autofree attribute for
'report'; then you can simply `return NULL` here. I guess it's a matter
of style (elsewhere in sev.c there are `goto err`, so maybe it's best to
keep the same style).
+ }
+
+ report = g_new0(SevAttestationReport, 1);
+ report->data = g_base64_encode(data, input.len);
In most other SEV commands in sev.c there's a trace-event with the
details of the command (for example, in sev_launch_get_measure it just
prints the result). I think adding such a trace here with the nonce and
the report->data would be helpful for debugging.
-Dov
+
+e_free_data:
+ g_free(data);
+ return report;
+}
+
static int
sev_read_file_base64(const char *filename, guchar **data, gsize *len)
{
diff --git a/target/i386/sev_i386.h b/target/i386/sev_i386.h
index 4db6960f60..e2d0774708 100644
--- a/target/i386/sev_i386.h
+++ b/target/i386/sev_i386.h
@@ -35,5 +35,7 @@ extern uint32_t sev_get_cbit_position(void);
extern uint32_t sev_get_reduced_phys_bits(void);
extern char *sev_get_launch_measurement(void);
extern SevCapability *sev_get_capabilities(Error **errp);
+extern SevAttestationReport *
+sev_get_attestation_report(const char *mnonce, Error **errp);
#endif
