identifiers: Differentiate signing keys from device keys

Use OwnedCrossSigningKeyId, OwnedDeviceSigningKeyId and
OwnedCrossSigningOrDeviceSigningKeyId instead of OwnedDeviceKeyId
to identify signing keys.

crates/ruma-client-api/CHANGELOG.md

@@ -21,6 +21,9 @@ Breaking changes:
 - Use `OwnedOneTimeKeyId` and `OneTimeKeyAlgorithm` instead of
   `OwnedDeviceKeyId` and `DeviceKeyAlgorithm` respectively to identify one-time
   and fallback keys and their algorithm.
+- Use `OwnedCrossSigningOrDeviceSigningKeyId` instead of `OwnedDeviceKeyId` to
+  identify signing keys in `BackupAlgorithm::MegolmBackupV1Curve25519AesSha2`'s
+  `signatures`.
 
 Improvements:
 

crates/ruma-client-api/src/backup.rs

@@ -20,7 +20,7 @@ use std::collections::BTreeMap;
 use js_int::UInt;
 use ruma_common::{
     serde::{Base64, Raw},
-    OwnedDeviceKeyId, OwnedUserId,
+    OwnedCrossSigningOrDeviceSigningKeyId, OwnedUserId,
 };
 use serde::{Deserialize, Serialize};
 
@@ -51,7 +51,7 @@ pub enum BackupAlgorithm {
         public_key: Base64,
 
         /// Signatures of the auth_data as Signed JSON.
-        signatures: BTreeMap<OwnedUserId, BTreeMap<OwnedDeviceKeyId, String>>,
+        signatures: BTreeMap<OwnedUserId, BTreeMap<OwnedCrossSigningOrDeviceSigningKeyId, String>>,
     },
 }
 

crates/ruma-common/CHANGELOG.md

@@ -29,6 +29,13 @@ Breaking changes:
   `Signatures::insert` is now dereferenced to `BTreeMap::insert`.
 - Move the `DeviceKeyAlgorithm::SignedCurve25519` into the new
   `OneTimeKeyAlgorithm` type.
+- Add `(Owned)CrossSigningKeyId` and use it instead of `OwnedDeviceKeyId` to
+  identify `CrossSigningKey`'s `keys`.
+- Add `(Owned)CrossSigningOrDeviceSigningKeyId` and use it instead of
+  `OwnedDeviceKeyId` to identify signing keys in `DeviceKeys`'s and
+  `CrossSigningKey`'s `signatures`.
+- Use `OwnedDeviceSigningKeyId` instead of `OwnedDeviceKeyId` to identify
+  signing keys in `SignedKey`'s `signatures`.
 
 Improvements:
 
@@ -49,6 +56,10 @@ Improvements:
   `(entity, key_identifier, value)` tuples.
 - Add `(Owned)OneTimeKeyId` and `(Owned)OneTimeKeyName` to identify one-time and
   fallback keys instead of using `(Owned)DeviceKeyId`.
+- Add `(Owned)Base64PublicKey` and `(Owned)Base64PublicKeyOrDeviceId` to
+  identify cross-signing keys.
+  - Add `(owned_)base_64_public_key` to construct a compile-time validated
+    `(Owned)Base64PublicKey`.
 
 # 0.13.0
 

crates/ruma-common/src/encryption.rs

@@ -8,7 +8,8 @@ use serde::{Deserialize, Serialize};
 
 use crate::{
     serde::{Base64, StringEnum},
-    EventEncryptionAlgorithm, OwnedDeviceId, OwnedDeviceKeyId, OwnedUserId, PrivOwnedStr,
+    EventEncryptionAlgorithm, OwnedCrossSigningKeyId, OwnedCrossSigningOrDeviceSigningKeyId,
+    OwnedDeviceId, OwnedDeviceKeyId, OwnedDeviceSigningKeyId, OwnedUserId, PrivOwnedStr,
 };
 
 /// Identity keys for a device.
@@ -32,7 +33,7 @@ pub struct DeviceKeys {
     pub keys: BTreeMap<OwnedDeviceKeyId, String>,
 
     /// Signatures for the device key object.
-    pub signatures: BTreeMap<OwnedUserId, BTreeMap<OwnedDeviceKeyId, String>>,
+    pub signatures: BTreeMap<OwnedUserId, BTreeMap<OwnedCrossSigningOrDeviceSigningKeyId, String>>,
 
     /// Additional data added to the device key information by intermediate servers, and
     /// not covered by the signatures.
@@ -48,7 +49,7 @@ impl DeviceKeys {
         device_id: OwnedDeviceId,
         algorithms: Vec<EventEncryptionAlgorithm>,
         keys: BTreeMap<OwnedDeviceKeyId, String>,
-        signatures: BTreeMap<OwnedUserId, BTreeMap<OwnedDeviceKeyId, String>>,
+        signatures: BTreeMap<OwnedUserId, BTreeMap<OwnedCrossSigningOrDeviceSigningKeyId, String>>,
     ) -> Self {
         Self { user_id, device_id, algorithms, keys, signatures, unsigned: Default::default() }
     }
@@ -76,7 +77,7 @@ impl UnsignedDeviceInfo {
 }
 
 /// Signatures for a `SignedKey` object.
-pub type SignedKeySignatures = BTreeMap<OwnedUserId, BTreeMap<OwnedDeviceKeyId, String>>;
+pub type SignedKeySignatures = BTreeMap<OwnedUserId, BTreeMap<OwnedDeviceSigningKeyId, String>>;
 
 /// A key for the SignedCurve25519 algorithm
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -118,9 +119,12 @@ pub enum OneTimeKey {
 }
 
 /// Signatures for a `CrossSigningKey` object.
-pub type CrossSigningKeySignatures = BTreeMap<OwnedUserId, BTreeMap<OwnedDeviceKeyId, String>>;
+pub type CrossSigningKeySignatures =
+    BTreeMap<OwnedUserId, BTreeMap<OwnedCrossSigningOrDeviceSigningKeyId, String>>;
 
-/// A cross signing key.
+/// A [cross-signing] key.
+///
+/// [cross-signing]: https://spec.matrix.org/latest/client-server-api/#cross-signing
 #[derive(Clone, Debug, Deserialize, Serialize)]
 #[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
 pub struct CrossSigningKey {
@@ -133,11 +137,15 @@ pub struct CrossSigningKey {
     /// The public key.
     ///
     /// The object must have exactly one property.
-    pub keys: BTreeMap<OwnedDeviceKeyId, String>,
+    pub keys: BTreeMap<OwnedCrossSigningKeyId, String>,
 
     /// Signatures of the key.
     ///
-    /// Only optional for master key.
+    /// The master key should be signed by the device key and can be signed by other users'
+    /// user-signing key. The user-signing and self-signing keys must be signed by the master
+    /// key.
+    ///
+    /// Only optional for the master key.
     #[serde(default, skip_serializing_if = "BTreeMap::is_empty")]
     pub signatures: CrossSigningKeySignatures,
 }
@@ -147,7 +155,7 @@ impl CrossSigningKey {
     pub fn new(
         user_id: OwnedUserId,
         usage: Vec<KeyUsage>,
-        keys: BTreeMap<OwnedDeviceKeyId, String>,
+        keys: BTreeMap<OwnedCrossSigningKeyId, String>,
         signatures: CrossSigningKeySignatures,
     ) -> Self {
         Self { user_id, usage, keys, signatures }

crates/ruma-common/src/identifiers.rs

@@ -16,6 +16,8 @@ use serde::de::{self, Deserializer, Unexpected};
 
 #[doc(inline)]
 pub use self::{
+    base64_public_key::{Base64PublicKey, OwnedBase64PublicKey},
+    base64_public_key_or_device_id::{Base64PublicKeyOrDeviceId, OwnedBase64PublicKeyOrDeviceId},
     client_secret::{ClientSecret, OwnedClientSecret},
     crypto_algorithms::{
         DeviceKeyAlgorithm, EventEncryptionAlgorithm, KeyDerivationAlgorithm, OneTimeKeyAlgorithm,
@@ -25,9 +27,10 @@ pub use self::{
     device_key_id::{DeviceKeyId, OwnedDeviceKeyId},
     event_id::{EventId, OwnedEventId},
     key_id::{
-        DeviceSigningKeyId, KeyAlgorithm, KeyId, OneTimeKeyId, OwnedDeviceSigningKeyId, OwnedKeyId,
-        OwnedOneTimeKeyId, OwnedServerSigningKeyId, OwnedSigningKeyId, ServerSigningKeyId,
-        SigningKeyId,
+        CrossSigningKeyId, CrossSigningOrDeviceSigningKeyId, DeviceSigningKeyId, KeyAlgorithm,
+        KeyId, OneTimeKeyId, OwnedCrossSigningKeyId, OwnedCrossSigningOrDeviceSigningKeyId,
+        OwnedDeviceSigningKeyId, OwnedKeyId, OwnedOneTimeKeyId, OwnedServerSigningKeyId,
+        OwnedSigningKeyId, ServerSigningKeyId, SigningKeyId,
     },
     matrix_uri::{MatrixToUri, MatrixUri},
     mxc_uri::{Mxc, MxcUri, OwnedMxcUri},
@@ -49,6 +52,8 @@ pub use self::{
 pub mod matrix_uri;
 pub mod user_id;
 
+mod base64_public_key;
+mod base64_public_key_or_device_id;
 mod client_secret;
 mod crypto_algorithms;
 mod device_id;
@@ -113,8 +118,8 @@ macro_rules! owned_device_id {
 #[doc(hidden)]
 pub mod __private_macros {
     pub use ruma_macros::{
-        device_key_id, event_id, mxc_uri, room_alias_id, room_id, room_version_id, server_name,
-        server_signing_key_version, user_id,
+        base64_public_key, device_key_id, event_id, mxc_uri, room_alias_id, room_id,
+        room_version_id, server_name, server_signing_key_version, user_id,
     };
 }
 
@@ -274,3 +279,19 @@ macro_rules! owned_user_id {
         $crate::user_id!($s).to_owned()
     };
 }
+
+/// Compile-time checked [`Base64PublicKey`] construction.
+#[macro_export]
+macro_rules! base64_public_key {
+    ($s:literal) => {
+        $crate::__private_macros::base64_public_key!($crate, $s)
+    };
+}
+
+/// Compile-time checked [`OwnedBase64PublicKey`] construction.
+#[macro_export]
+macro_rules! owned_base64_public_key {
+    ($s:literal) => {
+        $crate::base64_public_key!($s).to_owned()
+    };
+}

crates/ruma-common/src/identifiers/base64_public_key.rs

@@ -0,0 +1,84 @@
+use ruma_macros::IdZst;
+
+use super::{IdParseError, KeyName};
+use crate::serde::{base64::Standard, Base64, Base64DecodeError};
+
+/// A public key encoded using unpadded base64, used as an identifier for [cross-signing] keys.
+///
+/// This string is validated using the set `[a-zA-Z0-9+/=]`, but it is not validated to be decodable
+/// as base64. This type is provided simply for its semantic value.
+///
+/// [cross-signing]: https://spec.matrix.org/latest/client-server-api/#cross-signing
+#[repr(transparent)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, IdZst)]
+#[ruma_id(validate = ruma_identifiers_validation::base64_public_key::validate)]
+pub struct Base64PublicKey(str);
+
+impl OwnedBase64PublicKey {
+    /// Construct a new `OwnedBase64PublicKey` by encoding the given bytes using unpadded base64.
+    pub fn with_bytes<B: AsRef<[u8]>>(bytes: B) -> OwnedBase64PublicKey {
+        Base64::<Standard, B>::new(bytes).into()
+    }
+}
+
+impl KeyName for Base64PublicKey {
+    fn validate(s: &str) -> Result<(), IdParseError> {
+        ruma_identifiers_validation::base64_public_key::validate(s)
+    }
+}
+
+impl KeyName for OwnedBase64PublicKey {
+    fn validate(s: &str) -> Result<(), IdParseError> {
+        ruma_identifiers_validation::base64_public_key::validate(s)
+    }
+}
+
+impl<B: AsRef<[u8]>> From<Base64<Standard, B>> for OwnedBase64PublicKey {
+    fn from(value: Base64<Standard, B>) -> Self {
+        value.to_string().try_into().unwrap_or_else(|_| unreachable!())
+    }
+}
+
+impl TryFrom<&Base64PublicKey> for Base64<Standard, Vec<u8>> {
+    type Error = Base64DecodeError;
+
+    fn try_from(value: &Base64PublicKey) -> Result<Self, Self::Error> {
+        Base64::parse(value)
+    }
+}
+
+impl TryFrom<&OwnedBase64PublicKey> for Base64<Standard, Vec<u8>> {
+    type Error = Base64DecodeError;
+
+    fn try_from(value: &OwnedBase64PublicKey) -> Result<Self, Self::Error> {
+        Base64::parse(value)
+    }
+}
+
+impl TryFrom<OwnedBase64PublicKey> for Base64<Standard, Vec<u8>> {
+    type Error = Base64DecodeError;
+
+    fn try_from(value: OwnedBase64PublicKey) -> Result<Self, Self::Error> {
+        Base64::parse(value)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Base64PublicKey, OwnedBase64PublicKey};
+
+    #[test]
+    fn valid_string() {
+        <&Base64PublicKey>::try_from("base64+master+public+key").unwrap();
+    }
+
+    #[test]
+    fn invalid_string() {
+        <&Base64PublicKey>::try_from("not@base@64").unwrap_err();
+    }
+
+    #[test]
+    fn constructor() {
+        _ = OwnedBase64PublicKey::with_bytes(b"self-signing master public key");
+    }
+}

crates/ruma-common/src/identifiers/base64_public_key_or_device_id.rs

@@ -0,0 +1,65 @@
+use ruma_macros::IdZst;
+
+use super::{
+    Base64PublicKey, DeviceId, IdParseError, KeyName, OwnedBase64PublicKey, OwnedDeviceId,
+};
+
+/// A Matrix ID that can be either a [`DeviceId`] or a [`Base64PublicKey`].
+///
+/// Device identifiers in Matrix are completely opaque character sequences and cross-signing keys
+/// are identified by their base64-encoded public key. This type is provided simply for its semantic
+/// value.
+///
+/// It is not recommended to construct this type directly, it should instead be converted from a
+/// [`DeviceId`] or a [`Base64PublicKey`].
+///
+/// # Example
+///
+/// ```
+/// use ruma_common::{Base64PublicKeyOrDeviceId, OwnedBase64PublicKeyOrDeviceId};
+///
+/// let ref_id: &Base64PublicKeyOrDeviceId = "abcdefghi".into();
+/// assert_eq!(ref_id.as_str(), "abcdefghi");
+///
+/// let owned_id: OwnedBase64PublicKeyOrDeviceId = "ijklmnop".into();
+/// assert_eq!(owned_id.as_str(), "ijklmnop");
+/// ```
+#[repr(transparent)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, IdZst)]
+pub struct Base64PublicKeyOrDeviceId(str);
+
+impl KeyName for Base64PublicKeyOrDeviceId {
+    fn validate(_s: &str) -> Result<(), IdParseError> {
+        Ok(())
+    }
+}
+
+impl KeyName for OwnedBase64PublicKeyOrDeviceId {
+    fn validate(_s: &str) -> Result<(), IdParseError> {
+        Ok(())
+    }
+}
+
+impl<'a> From<&'a DeviceId> for &'a Base64PublicKeyOrDeviceId {
+    fn from(value: &'a DeviceId) -> Self {
+        Self::from(value.as_str())
+    }
+}
+
+impl From<OwnedDeviceId> for OwnedBase64PublicKeyOrDeviceId {
+    fn from(value: OwnedDeviceId) -> Self {
+        Self::from(value.as_str())
+    }
+}
+
+impl<'a> From<&'a Base64PublicKey> for &'a Base64PublicKeyOrDeviceId {
+    fn from(value: &'a Base64PublicKey) -> Self {
+        Self::from(value.as_str())
+    }
+}
+
+impl From<OwnedBase64PublicKey> for OwnedBase64PublicKeyOrDeviceId {
+    fn from(value: OwnedBase64PublicKey) -> Self {
+        Self::from(value.as_str())
+    }
+}

crates/ruma-common/src/identifiers/key_id.rs

@@ -7,8 +7,8 @@ use std::{
 use ruma_macros::IdZst;
 
 use super::{
-    crypto_algorithms::SigningKeyAlgorithm, DeviceId, KeyName, OneTimeKeyAlgorithm, OneTimeKeyName,
-    ServerSigningKeyVersion,
+    crypto_algorithms::SigningKeyAlgorithm, Base64PublicKey, Base64PublicKeyOrDeviceId, DeviceId,
+    KeyName, OneTimeKeyAlgorithm, OneTimeKeyName, ServerSigningKeyVersion,
 };
 
 /// A key algorithm and key name delimited by a colon.
@@ -63,12 +63,38 @@ pub type ServerSigningKeyId = SigningKeyId<ServerSigningKeyVersion>;
 /// Algorithm + key name for homeserver signing keys.
 pub type OwnedServerSigningKeyId = OwnedSigningKeyId<ServerSigningKeyVersion>;
 
-/// Algorithm + key name for device keys.
+/// Algorithm + key name for [device signing keys].
+///
+/// [device signing keys]: https://spec.matrix.org/latest/client-server-api/#device-keys
 pub type DeviceSigningKeyId = SigningKeyId<DeviceId>;
 
-/// Algorithm + key name for device keys.
+/// Algorithm + key name for [device signing] keys.
+///
+/// [device signing keys]: https://spec.matrix.org/latest/client-server-api/#device-keys
 pub type OwnedDeviceSigningKeyId = OwnedSigningKeyId<DeviceId>;
 
+/// Algorithm + key name for [cross-signing] keys.
+///
+/// [cross-signing]: https://spec.matrix.org/latest/client-server-api/#cross-signing
+pub type CrossSigningKeyId = SigningKeyId<Base64PublicKey>;
+
+/// Algorithm + key name for [cross-signing] keys.
+///
+/// [cross-signing]: https://spec.matrix.org/latest/client-server-api/#cross-signing
+pub type OwnedCrossSigningKeyId = OwnedSigningKeyId<Base64PublicKey>;
+
+/// Algorithm + key name for [cross-signing] or [device signing] keys.
+///
+/// [cross-signing]: https://spec.matrix.org/latest/client-server-api/#cross-signing
+/// [device signing]: https://spec.matrix.org/latest/client-server-api/#device-keys
+pub type CrossSigningOrDeviceSigningKeyId = SigningKeyId<Base64PublicKeyOrDeviceId>;
+
+/// Algorithm + key name for [cross-signing] or [device signing] keys.
+///
+/// [cross-signing]: https://spec.matrix.org/latest/client-server-api/#cross-signing
+/// [device signing]: https://spec.matrix.org/latest/client-server-api/#device-keys
+pub type OwnedCrossSigningOrDeviceSigningKeyId = OwnedSigningKeyId<Base64PublicKeyOrDeviceId>;
+
 /// Algorithm + key name for [one-time and fallback keys].
 ///
 /// [one-time and fallback keys]: https://spec.matrix.org/latest/client-server-api/#one-time-and-fallback-keys

crates/ruma-identifiers-validation/CHANGELOG.md

@@ -11,6 +11,7 @@ Breaking changes:
 Improvements:
 
 - Add `server_signing_key_version::validate`.
+- Add `base64_public_key::validate`.
 
 # 0.9.5
 

crates/ruma-identifiers-validation/src/base64_public_key.rs

@@ -0,0 +1,10 @@
+use crate::Error;
+
+pub fn validate(s: &str) -> Result<(), Error> {
+    if s.is_empty() {
+        return Err(Error::Empty);
+    } else if !s.chars().all(|c| c.is_alphanumeric() || matches!(c, '+' | '/' | '=')) {
+        return Err(Error::InvalidCharacters);
+    }
+    Ok(())
+}

crates/ruma-identifiers-validation/src/lib.rs

@@ -1,6 +1,7 @@
 #![doc(html_favicon_url = "https://ruma.dev/favicon.ico")]
 #![doc(html_logo_url = "https://ruma.dev/images/logo.png")]
 
+pub mod base64_public_key;
 pub mod client_secret;
 pub mod device_key_id;
 pub mod error;

crates/ruma-macros/src/lib.rs

@@ -15,8 +15,8 @@ use proc_macro::TokenStream;
 use proc_macro2 as pm2;
 use quote::quote;
 use ruma_identifiers_validation::{
-    device_key_id, event_id, mxc_uri, room_alias_id, room_id, room_version_id, server_name,
-    server_signing_key_version, user_id,
+    base64_public_key, device_key_id, event_id, mxc_uri, room_alias_id, room_id, room_version_id,
+    server_name, server_signing_key_version, user_id,
 };
 use syn::{parse_macro_input, DeriveInput, ItemEnum, ItemStruct};
 
@@ -266,6 +266,19 @@ pub fn user_id(input: TokenStream) -> TokenStream {
     output.into()
 }
 
+/// Compile-time checked `Base64PublicKey` construction.
+#[proc_macro]
+pub fn base64_public_key(input: TokenStream) -> TokenStream {
+    let IdentifierInput { dollar_crate, id } = parse_macro_input!(input as IdentifierInput);
+    assert!(base64_public_key::validate(&id.value()).is_ok(), "Invalid base64 public key");
+
+    let output = quote! {
+        <&#dollar_crate::DeviceKeyId as ::std::convert::TryFrom<&str>>::try_from(#id).unwrap()
+    };
+
+    output.into()
+}
+
 /// Derive the `AsRef<str>` trait for an enum.
 #[proc_macro_derive(AsRefStr, attributes(ruma_enum))]
 pub fn derive_enum_as_ref_str(input: TokenStream) -> TokenStream {