New metadata format (#539)

* new metadata format is used

* Update bootloader/src/main.rs

Co-authored-by: ztoked <zhalvorsen@google.com>

* splits the metadata signed and unsigned parts evenly

* fixes pylint

Co-authored-by: ztoked <zhalvorsen@google.com>

bootloader/src/main.rs

@@ -34,6 +34,7 @@ use rtt_target::{rprintln, rtt_init_print};
 
 /// Size of a flash page in bytes.
 const PAGE_SIZE: usize = 0x1000;
+const METADATA_SIGN_OFFSET: usize = 0x800;
 
 /// A flash page.
 type Page = [u8; PAGE_SIZE];
@@ -48,21 +49,19 @@ unsafe fn read_page(address: usize) -> Page {
 /// Parsed metadata for a firmware partition.
 struct Metadata {
     checksum: [u8; 32],
-    timestamp: u32,
+    _signature: [u8; 64],
+    version: u64,
     address: u32,
 }
 
-impl Metadata {
-    pub const DATA_LEN: usize = 40;
-}
-
 /// Reads the metadata from a flash page.
 impl From<Page> for Metadata {
     fn from(page: Page) -> Self {
         Metadata {
             checksum: page[0..32].try_into().unwrap(),
-            timestamp: LittleEndian::read_u32(&page[32..36]),
+            _signature: page[32..96].try_into().unwrap(),
-            address: LittleEndian::read_u32(&page[36..Metadata::DATA_LEN]),
+            version: LittleEndian::read_u64(&page[METADATA_SIGN_OFFSET..][..8]),
+            address: LittleEndian::read_u32(&page[METADATA_SIGN_OFFSET + 8..][..4]),
         }
     }
 }
@@ -76,15 +75,15 @@ struct BootPartition {
 impl BootPartition {
     const FIRMWARE_LENGTH: usize = 0x00040000;
 
-    /// Reads the metadata, returns the timestamp if all checks pass.
+    /// Reads the metadata, returns the firmware version if all checks pass.
-    pub fn read_timestamp(&self) -> Result<u32, ()> {
+    pub fn read_version(&self) -> Result<u64, ()> {
         let metadata_page = unsafe { read_page(self.metadata_address) };
         let hash_value = self.compute_upgrade_hash(&metadata_page);
         let metadata = Metadata::from(metadata_page);
         if self.firmware_address != metadata.address as usize {
             #[cfg(debug_assertions)]
             rprintln!(
-                "Firmware address mismatch: expected 0x{:08X}, metadata 0x{:08X}",
+                "Partition address mismatch: expected 0x{:08X}, metadata 0x{:08X}",
                 self.firmware_address,
                 metadata.address as usize
             );
@@ -95,7 +94,7 @@ impl BootPartition {
             rprintln!("Hash mismatch");
             return Err(());
         }
-        Ok(metadata.timestamp)
+        Ok(metadata.version)
     }
 
     /// Computes the SHA256 of metadata information and partition data.
@@ -107,11 +106,14 @@ impl BootPartition {
         debug_assert!(self.firmware_address % PAGE_SIZE == 0);
         debug_assert!(BootPartition::FIRMWARE_LENGTH % PAGE_SIZE == 0);
         let cc310 = crypto_cell::CryptoCell310::new();
+        cc310.update(&metadata_page[METADATA_SIGN_OFFSET..], false);
         for page_offset in (0..BootPartition::FIRMWARE_LENGTH).step_by(PAGE_SIZE) {
             let page = unsafe { read_page(self.firmware_address + page_offset) };
-            cc310.update(&page, false);
+            cc310.update(
+                &page,
+                page_offset + PAGE_SIZE == BootPartition::FIRMWARE_LENGTH,
+            );
         }
-        cc310.update(&metadata_page[32..Metadata::DATA_LEN], true);
         cc310.finalize_and_clear()
     }
 
@@ -156,12 +158,12 @@ fn main() -> ! {
     };
     #[cfg(debug_assertions)]
     rprintln!("Reading partition A");
-    let timestamp_a = partition_a.read_timestamp();
+    let version_a = partition_a.read_version();
     #[cfg(debug_assertions)]
     rprintln!("Reading partition B");
-    let timestamp_b = partition_b.read_timestamp();
+    let version_b = partition_b.read_version();
 
-    match (timestamp_a, timestamp_b) {
+    match (version_a, version_b) {
         (Ok(t1), Ok(t2)) => {
             if t1 >= t2 {
                 partition_a.boot()

deploy.py

@@ -38,7 +38,7 @@ from tockloader import tockloader as loader
 from tockloader.exceptions import TockLoaderException
 
 import tools.configure
-from tools.deploy_partition import create_metadata, pad_to
+from tools.deploy_partition import create_metadata, load_priv_key, pad_to
 
 PROGRAMMERS = frozenset(("jlink", "openocd", "pyocd", "nordicdfu", "none"))
 
@@ -622,7 +622,9 @@ class OpenSKInstaller:
     # The kernel is already padded when read.
     firmware_image = kernel + pad_to(app, app_size)
 
-    metadata = create_metadata(firmware_image, board_props.kernel_address)
+    priv_key = load_priv_key(self.args.upgrade_priv_key)
+    metadata = create_metadata(firmware_image, board_props.kernel_address,
+                               self.args.version, priv_key)
     if self.args.verbose_build:
       info(f"Metadata bytes: {metadata}")
 
@@ -1131,6 +1133,22 @@ if __name__ == "__main__":
       help=("Don't check that patches are in sync with their submodules."),
   )
 
+  main_parser.add_argument(
+      "--private-key",
+      type=str,
+      default="crypto_data/opensk_upgrade.key",
+      dest="upgrade_priv_key",
+      help=("PEM file for signing the firmware."),
+  )
+
+  main_parser.add_argument(
+      "--version",
+      type=int,
+      default=-1,
+      dest="version",
+      help=("Firmware version that is built."),
+  )
+
   main_parser.set_defaults(features=["with_ctap1"])
 
   # Start parsing to know if we're going to list things or not.

docs/boards/nrf52840dk.md

@@ -55,15 +55,15 @@ There are variants of the board that introduce A/B partitions for upgrading the
 firmware. You can bootstrap an upgradable board using one of the two commands:
 
 ```shell
-./deploy.py --board=nrf52840dk_opensk_a --opensk
+./deploy.py --board=nrf52840dk_opensk_a --opensk --version=0
-./deploy.py --board=nrf52840dk_opensk_b --opensk
+./deploy.py --board=nrf52840dk_opensk_b --opensk --version=0
 ```
 
 Afterwards, you can upgrade the other partition with
 
 ```shell
-./tools/perform_upgrade.sh nrf52840dk_opensk_b
+./tools/perform_upgrade.sh nrf52840dk_opensk_b --version=1
-./tools/perform_upgrade.sh nrf52840dk_opensk_a
+./tools/perform_upgrade.sh nrf52840dk_opensk_a --version=1
 ```
 
 respectively. You can only upgrade the partition that is not currently running,
@@ -75,6 +75,6 @@ If you deploy with `--vendor-hid`, also add this flag to `perform_upgrade.sh`,
 for example:
 
 ```shell
-./deploy.py --board=nrf52840dk_opensk_a --opensk --vendor-hid
+./deploy.py --board=nrf52840dk_opensk_a --opensk --version=0 --vendor-hid
-./tools/perform_upgrade.sh nrf52840dk_opensk_b --vendor-hid
+./tools/perform_upgrade.sh nrf52840dk_opensk_b --version=1 --vendor-hid
 ```

src/ctap/command.rs

@@ -15,11 +15,10 @@
 use super::data_formats::{
     extract_array, extract_bool, extract_byte_string, extract_map, extract_text_string,
     extract_unsigned, ok_or_missing, ClientPinSubCommand, ConfigSubCommand, ConfigSubCommandParams,
-    CoseKey, CoseSignature, CredentialManagementSubCommand,
+    CoseKey, CredentialManagementSubCommand, CredentialManagementSubCommandParameters,
-    CredentialManagementSubCommandParameters, GetAssertionExtensions, GetAssertionOptions,
+    GetAssertionExtensions, GetAssertionOptions, MakeCredentialExtensions, MakeCredentialOptions,
-    MakeCredentialExtensions, MakeCredentialOptions, PinUvAuthProtocol,
+    PinUvAuthProtocol, PublicKeyCredentialDescriptor, PublicKeyCredentialParameter,
-    PublicKeyCredentialDescriptor, PublicKeyCredentialParameter, PublicKeyCredentialRpEntity,
+    PublicKeyCredentialRpEntity, PublicKeyCredentialUserEntity, SetMinPinLengthParams,
-    PublicKeyCredentialUserEntity, SetMinPinLengthParams,
 };
 use super::status_code::Ctap2StatusCode;
 use super::{cbor_read, key_material};
@@ -596,7 +595,6 @@ pub struct AuthenticatorVendorUpgradeParameters {
     pub address: Option<usize>,
     pub data: Vec<u8>,
     pub hash: Vec<u8>,
-    pub signature: Option<CoseSignature>,
 }
 
 impl TryFrom<cbor::Value> for AuthenticatorVendorUpgradeParameters {
@@ -608,7 +606,6 @@ impl TryFrom<cbor::Value> for AuthenticatorVendorUpgradeParameters {
                 0x01 => address,
                 0x02 => data,
                 0x03 => hash,
-                0x04 => signature,
             } = extract_map(cbor_value)?;
         }
         let address = address
@@ -617,12 +614,10 @@ impl TryFrom<cbor::Value> for AuthenticatorVendorUpgradeParameters {
             .map(|u| u as usize);
         let data = extract_byte_string(ok_or_missing(data)?)?;
         let hash = extract_byte_string(ok_or_missing(hash)?)?;
-        let signature = signature.map(CoseSignature::try_from).transpose()?;
         Ok(AuthenticatorVendorUpgradeParameters {
             address,
             data,
             hash,
-            signature,
         })
     }
 }
@@ -631,7 +626,7 @@ impl TryFrom<cbor::Value> for AuthenticatorVendorUpgradeParameters {
 mod test {
     use super::super::data_formats::{
         AuthenticatorTransport, PublicKeyCredentialRpEntity, PublicKeyCredentialType,
-        PublicKeyCredentialUserEntity, SignatureAlgorithm,
+        PublicKeyCredentialUserEntity,
     };
     use super::super::ES256_CRED_PARAM;
     use super::*;
@@ -1096,10 +1091,6 @@ mod test {
         let cbor_value = cbor_map! {
             0x02 => [0xFF; 0x100],
             0x03 => [0x44; 32],
-            0x04 => cbor_map! {
-                "alg" => -7,
-                "signature" => [0x55; 64],
-            },
         };
         assert_eq!(
             AuthenticatorVendorUpgradeParameters::try_from(cbor_value),
@@ -1107,14 +1098,10 @@ mod test {
                 address: None,
                 data: vec![0xFF; 0x100],
                 hash: vec![0x44; 32],
-                signature: Some(CoseSignature {
-                    algorithm: SignatureAlgorithm::Es256,
-                    bytes: [0x55; 64],
-                }),
             })
         );
 
-        // Valid without signature
+        // Valid with address
         let cbor_value = cbor_map! {
             0x01 => 0x1000,
             0x02 => [0xFF; 0x100],
@@ -1126,7 +1113,6 @@ mod test {
                 address: Some(0x1000),
                 data: vec![0xFF; 0x100],
                 hash: vec![0x44; 32],
-                signature: None,
             })
         );
     }

src/ctap/data_formats.rs

@@ -912,53 +912,6 @@ impl TryFrom<CoseKey> for ecdsa::PubKey {
     }
 }
 
-/// Data structure for receiving a signature.
-///
-/// See https://datatracker.ietf.org/doc/html/rfc8152#appendix-C.1.1 for reference.
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct CoseSignature {
-    pub algorithm: SignatureAlgorithm,
-    pub bytes: [u8; ecdsa::Signature::BYTES_LENGTH],
-}
-
-impl TryFrom<cbor::Value> for CoseSignature {
-    type Error = Ctap2StatusCode;
-
-    fn try_from(cbor_value: cbor::Value) -> Result<Self, Ctap2StatusCode> {
-        destructure_cbor_map! {
-            let {
-                "alg" => algorithm,
-                "signature" => bytes,
-            } = extract_map(cbor_value)?;
-        }
-
-        let algorithm = SignatureAlgorithm::try_from(ok_or_missing(algorithm)?)?;
-        let bytes = extract_byte_string(ok_or_missing(bytes)?)?;
-        if bytes.len() != ecdsa::Signature::BYTES_LENGTH {
-            return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);
-        }
-
-        Ok(CoseSignature {
-            algorithm,
-            bytes: *array_ref![bytes.as_slice(), 0, ecdsa::Signature::BYTES_LENGTH],
-        })
-    }
-}
-
-impl TryFrom<CoseSignature> for ecdsa::Signature {
-    type Error = Ctap2StatusCode;
-
-    fn try_from(cose_signature: CoseSignature) -> Result<Self, Ctap2StatusCode> {
-        match cose_signature.algorithm {
-            SignatureAlgorithm::Es256 => ecdsa::Signature::from_bytes(&cose_signature.bytes)
-                .ok_or(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER),
-            #[cfg(feature = "ed25519")]
-            SignatureAlgorithm::Eddsa => Err(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_ALGORITHM),
-            SignatureAlgorithm::Unknown => Err(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_ALGORITHM),
-        }
-    }
-}
-
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "fuzz", derive(Arbitrary))]
 pub enum PinUvAuthProtocol {
@@ -1292,7 +1245,6 @@ mod test {
         cbor_array, cbor_bool, cbor_bytes, cbor_bytes_lit, cbor_false, cbor_int, cbor_null,
         cbor_text, cbor_unsigned,
     };
-    use crypto::sha256::Sha256;
     use rng256::Rng256;
 
     #[test]
@@ -2003,64 +1955,6 @@ mod test {
         assert_eq!(cose_key.algorithm, ES256_ALGORITHM);
     }
 
-    #[test]
-    fn test_from_into_cose_signature() {
-        let mut env = TestEnv::new();
-        let sk = crypto::ecdsa::SecKey::gensk(env.rng());
-        let dummy_signature = sk.sign_rfc6979::<Sha256>(&[]);
-        let mut bytes = [0; ecdsa::Signature::BYTES_LENGTH];
-        dummy_signature.to_bytes(&mut bytes);
-        let cbor_value = cbor_map! {
-            "alg" => ES256_ALGORITHM,
-            "signature" => bytes,
-        };
-        let cose_signature = CoseSignature::try_from(cbor_value).unwrap();
-        let created_signature = crypto::ecdsa::Signature::try_from(cose_signature).unwrap();
-        let mut created_bytes = [0; ecdsa::Signature::BYTES_LENGTH];
-        created_signature.to_bytes(&mut created_bytes);
-        assert_eq!(bytes[..], created_bytes[..]);
-    }
-
-    #[test]
-    fn test_cose_signature_wrong_algorithm() {
-        let mut env = TestEnv::new();
-        let sk = crypto::ecdsa::SecKey::gensk(env.rng());
-        let dummy_signature = sk.sign_rfc6979::<Sha256>(&[]);
-        let mut bytes = [0; ecdsa::Signature::BYTES_LENGTH];
-        dummy_signature.to_bytes(&mut bytes);
-        let cbor_value = cbor_map! {
-            "alg" => -1, // unused algorithm
-            "signature" => bytes,
-        };
-        let cose_signature = CoseSignature::try_from(cbor_value).unwrap();
-        let created_signature = crypto::ecdsa::Signature::try_from(cose_signature);
-        // Can not compare directly, since ecdsa::Signature does not implement Debug.
-        assert_eq!(
-            created_signature.err(),
-            Some(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_ALGORITHM)
-        );
-    }
-
-    #[test]
-    fn test_cose_signature_wrong_signature_length() {
-        let cbor_value = cbor_map! {
-            "alg" => ES256_ALGORITHM,
-            "signature" => [0; ecdsa::Signature::BYTES_LENGTH - 1],
-        };
-        assert_eq!(
-            CoseSignature::try_from(cbor_value),
-            Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER)
-        );
-        let cbor_value = cbor_map! {
-            "alg" => ES256_ALGORITHM,
-            "signature" => [0; ecdsa::Signature::BYTES_LENGTH + 1],
-        };
-        assert_eq!(
-            CoseSignature::try_from(cbor_value),
-            Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER)
-        );
-    }
-
     #[test]
     fn test_from_pin_uv_auth_protocol() {
         let cbor_protocol: cbor::Value = cbor_int!(0x01);

src/ctap/mod.rs

@@ -47,11 +47,10 @@ use self::credential_id::{
 use self::credential_management::process_credential_management;
 use self::crypto_wrapper::PrivateKey;
 use self::data_formats::{
-    AuthenticatorTransport, CoseKey, CoseSignature, CredentialProtectionPolicy,
+    AuthenticatorTransport, CoseKey, CredentialProtectionPolicy, EnterpriseAttestationMode,
-    EnterpriseAttestationMode, GetAssertionExtensions, PackedAttestationStatement,
+    GetAssertionExtensions, PackedAttestationStatement, PinUvAuthProtocol,
-    PinUvAuthProtocol, PublicKeyCredentialDescriptor, PublicKeyCredentialParameter,
+    PublicKeyCredentialDescriptor, PublicKeyCredentialParameter, PublicKeyCredentialSource,
-    PublicKeyCredentialSource, PublicKeyCredentialType, PublicKeyCredentialUserEntity,
+    PublicKeyCredentialType, PublicKeyCredentialUserEntity, SignatureAlgorithm,
-    SignatureAlgorithm,
 };
 use self::hid::{ChannelID, CtapHid, CtapHidCommand, KeepaliveStatus, ProcessedPacket};
 use self::large_blobs::LargeBlobs;
@@ -77,7 +76,7 @@ use alloc::string::{String, ToString};
 use alloc::vec;
 use alloc::vec::Vec;
 use arrayref::array_ref;
-use byteorder::{BigEndian, ByteOrder};
+use byteorder::{BigEndian, ByteOrder, LittleEndian};
 use core::convert::TryFrom;
 use crypto::hmac::hmac_256;
 use crypto::sha256::Sha256;
@@ -212,45 +211,61 @@ fn truncate_to_char_boundary(s: &str, mut max: usize) -> &str {
 
 /// Parses the metadata of an upgrade, and checks its correctness.
 ///
-/// Returns the hash over the upgrade, including partition and some metadata.
+/// The metadata is a page starting with:
-/// The metadata consists of:
+/// - 32 B upgrade hash (SHA256)
-/// - 32B upgrade hash (SHA256)
+/// - 64 B signature,
-/// -  4B timestamp (little endian encoding)
+/// that are not signed over. The second part is included in the signature with
-/// -  4B partition address (little endian encoding)
+/// -  8 B version and
-/// The upgrade hash is computed over the firmware image and all metadata,
+/// -  4 B partition address in little endian encoding
-/// except the hash itself.
+/// written at METADATA_SIGN_OFFSET.
+///
+/// Checks hash and signature correctness, and whether the partition offset matches.
 fn parse_metadata(
     upgrade_locations: &impl UpgradeStorage,
+    public_key_bytes: &[u8],
     metadata: &[u8],
-) -> Result<[u8; 32], Ctap2StatusCode> {
+) -> Result<(), Ctap2StatusCode> {
-    const METADATA_LEN: usize = 40;
+    const METADATA_LEN: usize = 0x1000;
+    const METADATA_SIGN_OFFSET: usize = 0x800;
     if metadata.len() != METADATA_LEN {
         return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);
     }
+
+    let metadata_address = LittleEndian::read_u32(&metadata[METADATA_SIGN_OFFSET + 8..][..4]);
+    if metadata_address as usize != upgrade_locations.partition_address() {
+        return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);
+    }
+
     // The hash implementation handles this in chunks, so no memory issues.
     let partition_slice = upgrade_locations
         .read_partition(0, upgrade_locations.partition_length())
         .map_err(|_| Ctap2StatusCode::CTAP2_ERR_VENDOR_INTERNAL_ERROR)?;
     let mut hasher = Sha256::new();
+    hasher.update(&metadata[METADATA_SIGN_OFFSET..]);
     hasher.update(partition_slice);
-    hasher.update(&metadata[32..METADATA_LEN]);
     let computed_hash = hasher.finalize();
     if &computed_hash != array_ref!(metadata, 0, 32) {
         return Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE);
     }
-    Ok(computed_hash)
+
+    verify_signature(
+        array_ref!(metadata, 32, 64),
+        public_key_bytes,
+        &computed_hash,
+    )?;
+    Ok(())
 }
 
 /// Verifies the signature over the given hash.
 ///
 /// The public key is COSE encoded, and the hash is a SHA256.
 fn verify_signature(
-    signature: Option<CoseSignature>,
+    signature_bytes: &[u8; 64],
     public_key_bytes: &[u8],
     signed_hash: &[u8; 32],
 ) -> Result<(), Ctap2StatusCode> {
-    let signature =
+    let signature = ecdsa::Signature::from_bytes(signature_bytes)
-        ecdsa::Signature::try_from(signature.ok_or(Ctap2StatusCode::CTAP2_ERR_MISSING_PARAMETER)?)?;
+        .ok_or(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER)?;
     let cbor_public_key = cbor_read(public_key_bytes)?;
     let cose_key = CoseKey::try_from(cbor_public_key)?;
     let public_key = ecdsa::PubKey::try_from(cose_key)?;
@@ -1454,7 +1469,6 @@ impl CtapState {
             address,
             data,
             hash,
-            signature,
         } = params;
         let upgrade_locations = env
             .upgrade_storage()
@@ -1468,9 +1482,7 @@ impl CtapState {
                 .map_err(|_| Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER)?
         } else {
             // Compares the hash inside the metadata to the actual hash.
-            let upgrade_hash = parse_metadata(upgrade_locations, &data)?;
+            parse_metadata(upgrade_locations, key_material::UPGRADE_PUBLIC_KEY, &data)?;
-            // Only signed firmware images may be fully written.
-            verify_signature(signature, key_material::UPGRADE_PUBLIC_KEY, &upgrade_hash)?;
             // Write the metadata page after verifying that its hash is signed.
             upgrade_locations
                 .write_metadata(&data)
@@ -3456,37 +3468,64 @@ mod test {
     #[test]
     fn test_parse_metadata() {
         let mut env = TestEnv::new();
-        // The test buffer starts fully erased with 0xFF bytes.
+        let private_key = crypto::ecdsa::SecKey::gensk(env.rng());
-        // The compiler issues an incorrect warning.
+        let upgrade_locations = env.upgrade_storage().unwrap();
-        #[allow(unused_mut)]
+
-        let mut upgrade_locations = env.upgrade_storage().unwrap();
+        const METADATA_LEN: usize = 0x1000;
+        const METADATA_SIGN_OFFSET: usize = 0x800;
+        let mut metadata = vec![0xFF; METADATA_LEN];
+        LittleEndian::write_u32(&mut metadata[METADATA_SIGN_OFFSET + 8..][..4], 0x60000);
+
+        let partition_length = upgrade_locations.partition_length();
+        let mut signed_over_data = metadata[METADATA_SIGN_OFFSET..].to_vec();
+        signed_over_data.extend(
+            upgrade_locations
+                .read_partition(0, partition_length)
+                .unwrap(),
+        );
+        let signed_hash = Sha256::hash(&signed_over_data);
+
+        metadata[..32].copy_from_slice(&signed_hash);
+        let signature = private_key.sign_rfc6979::<Sha256>(&signed_over_data);
+        let mut signature_bytes = [0; ecdsa::Signature::BYTES_LENGTH];
+        signature.to_bytes(&mut signature_bytes);
+        metadata[32..96].copy_from_slice(&signature_bytes);
+
+        let public_key = private_key.genpk();
+        let mut public_key_bytes = vec![];
+        cbor_write(
+            cbor::Value::from(CoseKey::from(public_key)),
+            &mut public_key_bytes,
+        )
+        .unwrap();
 
-        // Partition of 0x40000 bytes and 8 bytes metadata are hashed.
-        let hashed_data = vec![0xFF; 0x40000 + 8];
-        let expected_hash = Sha256::hash(&hashed_data);
-        let mut metadata = vec![0xFF; 40];
-        metadata[..32].copy_from_slice(&expected_hash);
         assert_eq!(
-            parse_metadata(upgrade_locations, &metadata),
+            parse_metadata(upgrade_locations, &public_key_bytes, &metadata),
-            Ok(expected_hash)
+            Ok(())
         );
 
         // Any manipulation of data fails.
-        metadata[32] = 0x88;
+        metadata[METADATA_SIGN_OFFSET] = 0x88;
         assert_eq!(
-            parse_metadata(upgrade_locations, &metadata),
+            parse_metadata(upgrade_locations, &public_key_bytes, &metadata),
             Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE)
         );
-        metadata[32] = 0xFF;
+        metadata[METADATA_SIGN_OFFSET] = 0xFF;
         metadata[0] ^= 0x01;
         assert_eq!(
-            parse_metadata(upgrade_locations, &metadata),
+            parse_metadata(upgrade_locations, &public_key_bytes, &metadata),
             Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE)
         );
         metadata[0] ^= 0x01;
+        metadata[32] ^= 0x01;
+        assert_eq!(
+            parse_metadata(upgrade_locations, &public_key_bytes, &metadata),
+            Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE)
+        );
+        metadata[32] ^= 0x01;
         upgrade_locations.write_partition(0, &[0x88; 1]).unwrap();
         assert_eq!(
-            parse_metadata(upgrade_locations, &metadata),
+            parse_metadata(upgrade_locations, &public_key_bytes, &metadata),
             Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE)
         );
     }
@@ -3501,10 +3540,6 @@ mod test {
 
         let mut signature_bytes = [0; ecdsa::Signature::BYTES_LENGTH];
         signature.to_bytes(&mut signature_bytes);
-        let cose_signature = CoseSignature {
-            algorithm: SignatureAlgorithm::Es256,
-            bytes: signature_bytes,
-        };
 
         let public_key = private_key.genpk();
         let mut public_key_bytes = vec![];
@@ -3515,34 +3550,22 @@ mod test {
         .unwrap();
 
         assert_eq!(
-            verify_signature(
+            verify_signature(&signature_bytes, &public_key_bytes, &signed_hash),
-                Some(cose_signature.clone()),
-                &public_key_bytes,
-                &signed_hash
-            ),
             Ok(())
         );
         assert_eq!(
-            verify_signature(Some(cose_signature.clone()), &public_key_bytes, &[0x55; 32]),
+            verify_signature(&signature_bytes, &public_key_bytes, &[0x55; 32]),
             Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE)
         );
         public_key_bytes[0] ^= 0x01;
         assert_eq!(
-            verify_signature(Some(cose_signature), &public_key_bytes, &signed_hash),
+            verify_signature(&signature_bytes, &public_key_bytes, &signed_hash),
             Err(Ctap2StatusCode::CTAP2_ERR_INVALID_CBOR)
         );
         public_key_bytes[0] ^= 0x01;
-        assert_eq!(
-            verify_signature(None, &public_key_bytes, &signed_hash),
-            Err(Ctap2StatusCode::CTAP2_ERR_MISSING_PARAMETER)
-        );
         signature_bytes[0] ^= 0x01;
-        let cose_signature = CoseSignature {
-            algorithm: SignatureAlgorithm::Es256,
-            bytes: signature_bytes,
-        };
         assert_eq!(
-            verify_signature(Some(cose_signature), &public_key_bytes, &signed_hash),
+            verify_signature(&signature_bytes, &public_key_bytes, &signed_hash),
             Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE)
         );
     }
@@ -3555,38 +3578,37 @@ mod test {
         let mut env = TestEnv::new();
         let private_key = crypto::ecdsa::SecKey::gensk(env.rng());
         let mut ctap_state = CtapState::new(&mut env, CtapInstant::new(0));
-        const METADATA_LEN: usize = 40;
+        const METADATA_LEN: usize = 0x1000;
+        const METADATA_SIGN_OFFSET: usize = 0x800;
+        let mut metadata = vec![0xFF; METADATA_LEN];
+        LittleEndian::write_u32(&mut metadata[METADATA_SIGN_OFFSET + 8..][..4], 0x60000);
 
         let data = vec![0xFF; 0x1000];
         let hash = Sha256::hash(&data).to_vec();
         let upgrade_locations = env.upgrade_storage().unwrap();
         let partition_length = upgrade_locations.partition_length();
-        let mut signed_over_data = upgrade_locations
+        let mut signed_over_data = metadata[METADATA_SIGN_OFFSET..].to_vec();
+        signed_over_data.extend(
+            upgrade_locations
                 .read_partition(0, partition_length)
-            .unwrap()
+                .unwrap(),
-            .to_vec();
+        );
-        signed_over_data.extend(&[0xFF; METADATA_LEN - 32]);
         let signed_hash = Sha256::hash(&signed_over_data);
-        let mut metadata = vec![0xFF; METADATA_LEN];
-        metadata[..32].copy_from_slice(&signed_hash);
-        let metadata_hash = Sha256::hash(&metadata).to_vec();
 
+        metadata[..32].copy_from_slice(&signed_hash);
         let signature = private_key.sign_rfc6979::<Sha256>(&signed_over_data);
         let mut signature_bytes = [0; ecdsa::Signature::BYTES_LENGTH];
         signature.to_bytes(&mut signature_bytes);
-        let cose_signature = CoseSignature {
+        metadata[32..96].copy_from_slice(&signature_bytes);
-            algorithm: SignatureAlgorithm::Es256,
+        let metadata_hash = Sha256::hash(&metadata).to_vec();
-            bytes: signature_bytes,
-        };
 
-        // Write to partition and metadata.
+        // Write to partition.
         let response = ctap_state.process_vendor_upgrade(
             &mut env,
             AuthenticatorVendorUpgradeParameters {
                 address: Some(0x20000),
                 data: data.clone(),
                 hash: hash.clone(),
-                signature: None,
             },
         );
         assert_eq!(response, Ok(ResponseData::AuthenticatorVendorUpgrade));
@@ -3599,7 +3621,6 @@ mod test {
                 address: None,
                 data: metadata.clone(),
                 hash: metadata_hash.clone(),
-                signature: Some(cose_signature.clone()),
             },
         );
         assert_eq!(response, Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE));
@@ -3611,7 +3632,6 @@ mod test {
                 address: None,
                 data: metadata[..METADATA_LEN - 1].to_vec(),
                 hash: metadata_hash,
-                signature: Some(cose_signature),
             },
         );
         assert_eq!(response, Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER));
@@ -3623,7 +3643,6 @@ mod test {
                 address: Some(0x40000),
                 data: data.clone(),
                 hash,
-                signature: None,
             },
         );
         assert_eq!(response, Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER));
@@ -3635,7 +3654,6 @@ mod test {
                 address: Some(0x20000),
                 data,
                 hash: [0xEE; 32].to_vec(),
-                signature: None,
             },
         );
         assert_eq!(response, Err(Ctap2StatusCode::CTAP2_ERR_INTEGRITY_FAILURE));
@@ -3655,7 +3673,6 @@ mod test {
                 address: Some(0),
                 data,
                 hash,
-                signature: None,
             },
         );
         assert_eq!(response, Err(Ctap2StatusCode::CTAP1_ERR_INVALID_COMMAND));

tools/deploy_partition.py

@@ -20,7 +20,6 @@ from __future__ import division
 from __future__ import print_function
 
 import argparse
-import datetime
 import hashlib
 import os
 import struct
@@ -44,6 +43,7 @@ OPENSK_VID_PID = (0x1915, 0x521F)
 OPENSK_VENDOR_UPGRADE = 0x42
 OPENSK_VENDOR_UPGRADE_INFO = 0x43
 PAGE_SIZE = 0x1000
+METADATA_SIGN_OFFSET = 0x800
 KERNEL_SIZE = 0x20000
 APP_SIZE = 0x20000
 PARTITION_ADDRESS = {
@@ -54,7 +54,15 @@ ES256_ALGORITHM = -7
 ARCH = "thumbv7em-none-eabi"
 
 
-def create_metadata(firmware_image: bytes, partition_address: int) -> bytes:
+def hash_message(message: bytes) -> bytes:
+  """Uses SHA256 to hash a message."""
+  sha256_hash = hashlib.sha256()
+  sha256_hash.update(message)
+  return sha256_hash.digest()
+
+
+def create_metadata(firmware_image: bytes, partition_address: int, version: int,
+                    priv_key: Any) -> bytes:
   """Creates the matching metadata for the given firmware.
 
   The metadata consists of a timestamp, the expected address and a hash of
@@ -65,25 +73,26 @@ def create_metadata(firmware_image: bytes, partition_address: int) -> bytes:
     partition_address: The address to be written as a metadata property.
 
   Returns:
-    A byte array consisting of 32B hash, 4B timestamp and 4B partition address
+    A byte array of page size, consisting of
-    in little endian encoding.
+    - 32 B hash,
+    - 64 B signature,
+    at the beginning and
+    -  8 B version and
+    -  4 B partition address in little endian encoding
+    after METADATA_SIGN_OFFSET. All other bytes are 0xFF.
   """
-  t = datetime.datetime.utcnow().timestamp()
+  if version < 0 or version >= 2**63:
-  timestamp = struct.pack("<I", int(t))
+    fatal("The version must fit into an unsigned integer with 63 bit.\n"
+          "Please pass it using --version")
+  version_bytes = struct.pack("<Q", version)
   partition_start = struct.pack("<I", partition_address)
-  sha256_hash = hashlib.sha256()
+  # Prefix sizes that are a multiple of 64 suit our bootloader's SHA.
-  sha256_hash.update(firmware_image)
+  signed_metadata = pad_to(version_bytes + partition_start,
-  sha256_hash.update(timestamp)
+                           PAGE_SIZE - METADATA_SIGN_OFFSET)
-  sha256_hash.update(partition_start)
+  signed_data = signed_metadata + firmware_image
-  checksum = sha256_hash.digest()
+  checksum = hash_message(signed_data)
-  return checksum + timestamp + partition_start
+  signature = sign_firmware(signed_data, priv_key)
-
+  return pad_to(checksum + signature, METADATA_SIGN_OFFSET) + signed_metadata
-
-def hash_message(message: bytes) -> bytes:
-  """Uses SHA256 to hash a message."""
-  sha256_hash = hashlib.sha256()
-  sha256_hash.update(message)
-  return sha256_hash.digest()
 
 
 def check_info(partition_address: int, authenticator: Any):
@@ -95,7 +104,8 @@ def check_info(partition_address: int, authenticator: Any):
         data={},
     )
     if result[0x01] != partition_address:
-      fatal("Identifiers do not match.")
+      fatal(f"Identifiers do not match, received 0x{result[0x01]:0x}, "
+            f"expected 0x{partition_address:0x}.")
   except ctap.CtapError as ex:
     fatal(f"Failed to read OpenSK upgrade info (error: {ex})")
 
@@ -163,19 +173,14 @@ def sign_firmware(data: bytes, priv_key: Any) -> bytes:
 
 def main(args):
   colorama.init()
+  if not args.priv_key:
+    fatal("Please pass in a private key file using --private-key.")
 
   firmware_image = generate_firmware_image(args.board)
   partition_address = PARTITION_ADDRESS[args.board]
-  metadata = create_metadata(firmware_image, partition_address)
-
-  if not args.priv_key:
-    fatal("Please pass in a private key file using --private-key.")
   priv_key = load_priv_key(args.priv_key)
-  signed_data = firmware_image + metadata[32:40]
+  metadata = create_metadata(firmware_image, partition_address, args.version,
-  signature = {
+                             priv_key)
-      "alg": ES256_ALGORITHM,
-      "signature": sign_firmware(signed_data, priv_key)
-  }
 
   if args.use_vendor_hid:
     patcher = patch.object(hid.base, "FIDO_USAGE_PAGE", 0xFF00)
@@ -206,11 +211,13 @@ def main(args):
         )
 
       info("Writing metadata...")
-      cbor_data = {2: metadata, 3: hash_message(metadata), 4: signature}
+      # TODO Write the correct address when the metadata is transparent.
+      cbor_data = {2: metadata, 3: hash_message(metadata)}
       authenticator.send_cbor(
           OPENSK_VENDOR_UPGRADE,
           data=cbor_data,
       )
+
     except ctap.CtapError as ex:
       message = "Failed to upgrade OpenSK"
       if ex.code.value == ctap.CtapError.ERR.INVALID_COMMAND:
@@ -263,4 +270,10 @@ if __name__ == "__main__":
       dest="use_vendor_hid",
       help=("Whether to upgrade the device using the Vendor HID interface."),
   )
+  parser.add_argument(
+      "--version",
+      type=int,
+      dest="version",
+      help=("Firmware version that is built."),
+  )
   main(parser.parse_args())