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>

1 files changed, 67 insertions, 0 deletions

diff --git a/target/i386/sev.c b/target/i386/sev.c
index 41f7800b5f..1a88f12703 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -492,6 +492,73 @@ out:
     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)
 {