refactor: unify SnapshotMeta and TimestampMeta

The `METAFILES` object contained by `snapshot.json` and by
`timestamp.json` is the same. This commit removes the duplicated
structures that were previously used to hold the same data.

`SnapshotMeta` and `TimestampMeta` are now replaced by `Metafiles`.

Signed-off-by: Flavio Castelli <fcastelli@suse.com>

tough/src/editor/mod.rs

@@ -17,8 +17,8 @@ use crate::key_source::KeySource;
 use crate::schema::decoded::{Decoded, Hex};
 use crate::schema::key::Key;
 use crate::schema::{
-    Hashes, KeyHolder, PathSet, Role, RoleType, Root, Signed, Snapshot, SnapshotMeta, Target,
-    Targets, Timestamp, TimestampMeta,
+    Hashes, KeyHolder, Metafiles, PathSet, Role, RoleType, Root, Signed, Snapshot, Target, Targets,
+    Timestamp,
 };
 use crate::transport::{IntoVec, Transport};
 use crate::{encode_filename, Limits};
@@ -700,13 +700,13 @@ impl RepositoryEditor {
         Ok(snapshot)
     }
 
-    /// Build a `SnapshotMeta` struct from a given `SignedRole<R>`. This metadata
+    /// Build a `Metafiles` struct from a given `SignedRole<R>`. This metadata
     /// includes the sha256 and length of the signed role.
-    fn snapshot_meta<R>(role: &SignedRole<R>) -> SnapshotMeta
+    fn snapshot_meta<R>(role: &SignedRole<R>) -> Metafiles
     where
         R: Role,
     {
-        SnapshotMeta {
+        Metafiles {
             hashes: Some(Hashes {
                 sha256: role.sha256.to_vec().into(),
                 _extra: HashMap::new(),
@@ -738,13 +738,13 @@ impl RepositoryEditor {
         Ok(timestamp)
     }
 
-    /// Build a `TimestampMeta` struct from a given `SignedRole<R>`. This metadata
+    /// Build a `Metafiles` struct from a given `SignedRole<R>`. This metadata
     /// includes the sha256 and length of the signed role.
-    fn timestamp_meta<R>(role: &SignedRole<R>) -> TimestampMeta
+    fn timestamp_meta<R>(role: &SignedRole<R>) -> Metafiles
     where
         R: Role,
     {
-        TimestampMeta {
+        Metafiles {
             hashes: Some(Hashes {
                 sha256: role.sha256.to_vec().into(),
                 _extra: HashMap::new(),

tough/src/schema/mod.rs

@@ -256,11 +256,11 @@ pub struct Snapshot {
     /// Determines when metadata should be considered expired and no longer trusted by clients.
     pub expires: DateTime<Utc>,
 
-    /// A list of what the TUF spec calls 'METAFILES' (`SnapshotMeta` objects). The TUF spec
+    /// A list of what the TUF spec calls 'METAFILES' (`Metafiles` objects). The TUF spec
     /// describes the hash key in 4.4: METAPATH is the file path of the metadata on the repository
     /// relative to the metadata base URL. For snapshot.json, these are top-level targets metadata
     /// and delegated targets metadata.
-    pub meta: HashMap<String, SnapshotMeta>,
+    pub meta: HashMap<String, Metafiles>,
 
     /// Extra arguments found during deserialization.
     ///
@@ -272,7 +272,7 @@ pub struct Snapshot {
     pub _extra: HashMap<String, Value>,
 }
 
-/// Represents a metadata file in a `snapshot.json` file.
+/// Represents a metadata file in a `snapshot.json` and in a `timestamp.json` file.
 /// TUF 4.4: METAFILES is an object whose format is the following:
 /// ```text
 ///  { METAPATH : {
@@ -292,7 +292,7 @@ pub struct Snapshot {
 ///    },
 /// ```
 #[derive(Debug, Clone, Deserialize, Serialize, Eq, PartialEq)]
-pub struct SnapshotMeta {
+pub struct Metafiles {
     /// LENGTH is the integer length in bytes of the metadata file at METAPATH. It is OPTIONAL and
     /// can be omitted to reduce the snapshot metadata file size. In that case the client MUST use a
     /// custom download limit for the listed metadata.
@@ -1112,7 +1112,7 @@ pub struct Timestamp {
 
     /// METAFILES is the same as described for the snapshot.json file. In the case of the
     /// timestamp.json file, this MUST only include a description of the snapshot.json file.
-    pub meta: HashMap<String, TimestampMeta>,
+    pub meta: HashMap<String, Metafiles>,
 
     /// Extra arguments found during deserialization.
     ///
@@ -1124,36 +1124,6 @@ pub struct Timestamp {
     pub _extra: HashMap<String, Value>,
 }
 
-/// METAFILES is the same as described for the snapshot.json file. In the case of the timestamp.json
-/// file, this MUST only include a description of the snapshot.json file.
-#[derive(Debug, Clone, Deserialize, Serialize, Eq, PartialEq)]
-pub struct TimestampMeta {
-    /// The integer length in bytes of the snapshot.json file. It is OPTIONAL and
-    /// can be omitted to reduce the snapshot metadata file size. In that case the client MUST use a
-    /// custom download limit for the listed metadata.
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub length: Option<u64>,
-
-    /// The hashes of the snapshot.json file. HASHES
-    /// is OPTIONAL and can be omitted to reduce the snapshot metadata file size. In that case the
-    /// repository MUST guarantee that VERSION alone unambiguously identifies the metadata at
-    /// METAPATH.
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub hashes: Option<Hashes>,
-
-    /// An integer that is greater than 0. Clients MUST NOT replace a metadata file with a version
-    /// number less than the one currently trusted.
-    pub version: NonZeroU64,
-
-    /// Extra arguments found during deserialization.
-    ///
-    /// We must store these to correctly verify signatures for this object.
-    ///
-    /// If you're instantiating this struct, you should make this `HashMap::empty()`.
-    #[serde(flatten)]
-    pub _extra: HashMap<String, Value>,
-}
-
 impl Timestamp {
     /// Creates a new `Timestamp` object.
     pub fn new(spec_version: String, version: NonZeroU64, expires: DateTime<Utc>) -> Self {