Adding the KeyInfo field into the attestation report

Since version 2 of the attestation report, instead of having just the
AUTHOR_KEY_EN fIELD in the attestation report, the report now offers
more data around the signature and the key being used in the attestation
report. This PR extends that field and makes it accessible in the
attestation report.

Signed-off-by: DGonzalezVillal <[email protected]>

src/firmware/guest/types/snp.rs

@@ -143,9 +143,8 @@ pub struct AttestationReport {
     pub current_tcb: TcbVersion,
     /// Information about the platform. See PlatformInfo
     pub plat_info: PlatformInfo,
-    /// Private variable as only the first bit is important.
-    /// See [author_key_en()](self::AttestationReport::author_key_en).
-    _author_key_en: u32,
+    /// Information related to signing keys in the report. See KeyInfo
+    pub key_info: KeyInfo,
     _reserved_0: u32,
     #[serde(with = "BigArray")]
     /// Guest-provided 512 Bits of Data
@@ -199,12 +198,6 @@ pub struct AttestationReport {
     pub signature: Signature,
 }
 
-impl AttestationReport {
-    fn author_key_en(&self) -> bool {
-        self._author_key_en == 1
-    }
-}
-
 impl Default for AttestationReport {
     fn default() -> Self {
         Self {
@@ -217,7 +210,7 @@ impl Default for AttestationReport {
             sig_algo: Default::default(),
             current_tcb: Default::default(),
             plat_info: Default::default(),
-            _author_key_en: Default::default(),
+            key_info: Default::default(),
             _reserved_0: Default::default(),
             report_data: [0; 64],
             measurement: [0; 48],
@@ -261,7 +254,7 @@ Signature Algorithm:          {}
 Current TCB:
 {}
 {}
-Author Key Encryption:        {}
+{}
 Report Data:                  {}
 Measurement:                  {}
 Host Data:                    {}
@@ -293,7 +286,7 @@ Launch TCB:
             self.sig_algo,
             self.current_tcb,
             self.plat_info,
-            self.author_key_en(),
+            self.key_info,
             hexdump(&self.report_data),
             hexdump(&self.measurement),
             hexdump(&self.host_data),
@@ -520,3 +513,57 @@ Platform Info ({}):
         )
     }
 }
+
+bitfield! {
+    /// When an attestation report is requested, the user can request to have the report to not be signed, or sign with different keys. The user may also
+    /// pass in the author key when launching the guest. This field provides that information and will be present in the attestation report.
+    ///
+    /// | Bit(s) | Name              | Description                                                                                                        >
+    /// |--------|-------------------|-------------------------------------------------------------------------------------------------------------------->
+    /// | 0      | AUTHOR_KEY_EN     | Indicates that the digest of the author key is present in AUTHOR_KEY_DIGEST. Set to the value of GCTX.AuthorKeyEn. >
+    /// | 1      | MASK_CHIP_KEY     | The value of MaskChipKey.                                                                                          >
+    /// | 4:2    | SIGNING_KEY       | Encodes the key used to sign this report.                                                                          >
+    /// | 5:31   | -                 | Reserved. Must be zero.                                                                                            >
+    #[repr(C)]
+    #[derive(Default, Deserialize, Clone, Copy, Eq, PartialEq, Serialize)]
+    pub struct KeyInfo(u32);
+    impl Debug;
+    /// AUTHOR_KEY_EN field: Indicates that the digest of the author key is present in AUTHOR_KEY_DIGEST
+    pub author_key_en, _: 0;
+    /// MASK_CHIP_KEY field: The value of MaskChipKey
+    /// (0) Firmware signs the attestation report with either the VCEK OR VLEK.
+    /// (1) The firmware writes 0s into the SIGNATURE field instead of signing the report.
+    pub mask_chip_key, _: 1,1;
+    /// SIGNING_KEY field: Encodes the key used to sign this report.
+    /// (0) VCEK
+    /// (1) VLEK
+    /// (2-6) RESERVED
+    /// (7) NONE
+    pub signing_key, _: 4,2;
+    /// reserved
+    reserved, _: 5, 31;
+}
+
+impl Display for KeyInfo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let signing_key = match self.signing_key() {
+            0 => "vcek",
+            1 => "vlek",
+            7 => "none",
+            _ => "unkown",
+        };
+
+        write!(
+            f,
+            r#"
+Key Information:
+    author key enabled: {}
+    mask chip key:      {}
+    signing key:        {}
+"#,
+            self.author_key_en(),
+            self.mask_chip_key(),
+            signing_key
+        )
+    }
+}