target/i386/sev: add support to query the attestation report

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@linux.ibm.com>
Cc: Tom Lendacky <Thomas.Lendacky@amd.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Reviewed-by: James Bottomley <jejb@linux.ibm.com>
Tested-by: James Bottomley <jejb@linux.ibm.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Connor Kuehl <ckuehl@redhat.com>
Message-Id: <20210429170728.24322-1-brijesh.singh@amd.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

linux-headers/linux/kvm.h

@@ -1591,6 +1591,8 @@ 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,
 };
@@ -1643,6 +1645,12 @@ 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)

qapi/misc-target.json

@@ -285,3 +285,41 @@
 ##
 { '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: 6.1
+##
+{ '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 value encoded in base64 (it will be included in report)
+#
+# Returns: SevAttestationReport objects.
+#
+# Since: 6.1
+#
+# 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)' }

target/i386/monitor.c

@@ -757,3 +757,9 @@ void qmp_sev_inject_launch_secret(const char *packet_hdr,
 
     sev_inject_launch_secret(packet_hdr, secret, gpa, errp);
 }
+
+SevAttestationReport *
+qmp_query_sev_attestation_report(const char *mnonce, Error **errp)
+{
+    return sev_get_attestation_report(mnonce, errp);
+}

target/i386/sev-stub.c

@@ -74,3 +74,10 @@ int sev_es_save_reset_vector(void *flash_ptr, uint64_t flash_size)
 {
     abort();
 }
+
+SevAttestationReport *
+sev_get_attestation_report(const char *mnonce, Error **errp)
+{
+    error_setg(errp, "SEV is not available in this QEMU");
+    return NULL;
+}

target/i386/sev.c

@@ -492,6 +492,73 @@ sev_get_capabilities(Error **errp)
     return cap;
 }
 
+SevAttestationReport *
+sev_get_attestation_report(const char *mnonce, Error **errp)
+{
+    struct kvm_sev_attestation_report input = {};
+    SevAttestationReport *report = NULL;
+    SevGuestState *sev = sev_guest;
+    guchar *data;
+    guchar *buf;
+    gsize len;
+    int err = 0, ret;
+
+    if (!sev_enabled()) {
+        error_setg(errp, "SEV is not enabled");
+        return NULL;
+    }
+
+    /* lets decode the mnonce string */
+    buf = g_base64_decode(mnonce, &len);
+    if (!buf) {
+        error_setg(errp, "SEV: failed to decode mnonce input");
+        return NULL;
+    }
+
+    /* verify the input mnonce length */
+    if (len != sizeof(input.mnonce)) {
+        error_setg(errp, "SEV: mnonce must be %zu bytes (got %" G_GSIZE_FORMAT ")",
+                sizeof(input.mnonce), len);
+        g_free(buf);
+        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));
+            g_free(buf);
+            return NULL;
+        }
+    }
+
+    data = g_malloc(input.len);
+    input.uaddr = (unsigned long)data;
+    memcpy(input.mnonce, buf, 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;
+    }
+
+    report = g_new0(SevAttestationReport, 1);
+    report->data = g_base64_encode(data, input.len);
+
+    trace_kvm_sev_attestation_report(mnonce, report->data);
+
+e_free_data:
+    g_free(data);
+    g_free(buf);
+    return report;
+}
+
 static int
 sev_read_file_base64(const char *filename, guchar **data, gsize *len)
 {

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

target/i386/trace-events

@@ -10,3 +10,4 @@ kvm_sev_launch_update_data(void *addr, uint64_t len) "addr %p len 0x%" PRIx64
 kvm_sev_launch_measurement(const char *value) "data %s"
 kvm_sev_launch_finish(void) ""
 kvm_sev_launch_secret(uint64_t hpa, uint64_t hva, uint64_t secret, int len) "hpa 0x%" PRIx64 " hva 0x%" PRIx64 " data 0x%" PRIx64 " len %d"
+kvm_sev_attestation_report(const char *mnonce, const char *data) "mnonce %s data %s"