events: Add support for encrypted stickers

crates/ruma-events/CHANGELOG.md

@@ -1,5 +1,13 @@
 # [unreleased]
 
+Improvements:
+
+ - Add support for encrypted stickers as sent by several bridges under the flag `compat-encrypted-stickers`
+
+Breaking changes:
+
+ - `StickerEventContent::url` was replaced by `StickerEventContent::source` which is a `StickerMediaSource`
+
 # 0.28.1
 
 Improvements:

crates/ruma-events/Cargo.toml

@@ -56,6 +56,10 @@ compat-optional = []
 # Allow TagInfo to contain a stringified floating-point value for the `order` field.
 compat-tag-info = []
 
+# Support encrypted stickers, as sent by several bridges.
+# https://github.com/matrix-org/matrix-spec/issues/1667
+compat-encrypted-stickers = []
+
 [dependencies]
 as_variant = { workspace = true }
 indexmap = { version = "2.0.0", features = ["serde"] }

crates/ruma-events/src/sticker.rs

@@ -4,9 +4,77 @@
 
 use ruma_common::OwnedMxcUri;
 use ruma_macros::EventContent;
-use serde::{Deserialize, Serialize};
+use serde::{de, Deserialize, Serialize};
 
-use crate::room::ImageInfo;
+#[cfg(feature = "compat-encrypted-stickers")]
+use crate::room::EncryptedFile;
+use crate::room::{ImageInfo, MediaSource};
+
+/// The source of a sticker media file.
+#[derive(Clone, Debug, Serialize)]
+#[non_exhaustive]
+pub enum StickerMediaSource {
+    /// The MXC URI to the unencrypted media file.
+    #[serde(rename = "url")]
+    Plain(OwnedMxcUri),
+
+    /// The encryption info of the encrypted media file.
+    #[cfg(feature = "compat-encrypted-stickers")]
+    #[serde(rename = "file")]
+    Encrypted(Box<EncryptedFile>),
+}
+
+// Custom implementation of `Deserialize`, because serde doesn't guarantee what variant will be
+// deserialized for "externally tagged"¹ enums where multiple "tag" fields exist.
+//
+// ¹ https://serde.rs/enum-representations.html
+impl<'de> Deserialize<'de> for StickerMediaSource {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct StickerMediaSourceJsonRepr {
+            url: Option<OwnedMxcUri>,
+            #[cfg(feature = "compat-encrypted-stickers")]
+            file: Option<Box<EncryptedFile>>,
+        }
+
+        match StickerMediaSourceJsonRepr::deserialize(deserializer)? {
+            StickerMediaSourceJsonRepr {
+                url: None,
+                #[cfg(feature = "compat-encrypted-stickers")]
+                    file: None,
+            } => Err(de::Error::missing_field("url")),
+            // Prefer file if it is set
+            #[cfg(feature = "compat-encrypted-stickers")]
+            StickerMediaSourceJsonRepr { file: Some(file), .. } => {
+                Ok(StickerMediaSource::Encrypted(file))
+            }
+            StickerMediaSourceJsonRepr { url: Some(url), .. } => Ok(StickerMediaSource::Plain(url)),
+        }
+    }
+}
+
+impl From<StickerMediaSource> for MediaSource {
+    fn from(value: StickerMediaSource) -> Self {
+        match value {
+            StickerMediaSource::Plain(url) => MediaSource::Plain(url),
+            #[cfg(feature = "compat-encrypted-stickers")]
+            StickerMediaSource::Encrypted(file) => MediaSource::Encrypted(file),
+        }
+    }
+}
+
+#[cfg(feature = "compat-encrypted-stickers")]
+impl From<MediaSource> for StickerMediaSource {
+    fn from(value: MediaSource) -> Self {
+        match value {
+            MediaSource::Plain(url) => StickerMediaSource::Plain(url),
+            MediaSource::Encrypted(file) => StickerMediaSource::Encrypted(file),
+        }
+    }
+}
 
 /// The content of an `m.sticker` event.
 ///
@@ -24,13 +92,19 @@ pub struct StickerEventContent {
     /// Metadata about the image referred to in `url` including a thumbnail representation.
     pub info: ImageInfo,
 
-    /// The URL to the sticker image.
-    pub url: OwnedMxcUri,
+    /// The media source of the sticker image.
+    #[serde(flatten)]
+    pub source: StickerMediaSource,
 }
 
 impl StickerEventContent {
     /// Creates a new `StickerEventContent` with the given body, image info and URL.
     pub fn new(body: String, info: ImageInfo, url: OwnedMxcUri) -> Self {
-        Self { body, info, url }
+        Self { body, info, source: StickerMediaSource::Plain(url.clone()) }
+    }
+
+    /// Creates a new `StickerEventContent` with the given body, image info, URL, and media source.
+    pub fn with_source(body: String, info: ImageInfo, source: StickerMediaSource) -> Self {
+        Self { body, info, source }
     }
 }

crates/ruma-events/tests/it/sticker.rs

@@ -4,7 +4,7 @@ use js_int::{uint, UInt};
 use ruma_common::{mxc_uri, serde::CanBeEmpty, MilliSecondsSinceUnixEpoch};
 use ruma_events::{
     room::{ImageInfo, MediaSource, ThumbnailInfo},
-    sticker::StickerEventContent,
+    sticker::{StickerEventContent, StickerMediaSource},
     AnyMessageLikeEvent, MessageLikeEvent,
 };
 use serde_json::{from_value as from_json_value, json, to_value as to_json_value};
@@ -79,7 +79,44 @@ fn content_deserialization() {
 
     let content = from_json_value::<StickerEventContent>(json_data).unwrap();
     assert_eq!(content.body, "Upload: my_image.jpg");
-    assert_eq!(content.url, "mxc://notareal.hs/file");
+    assert_matches!(content.source, StickerMediaSource::Plain(sticker_url));
+    assert_eq!(sticker_url, "mxc://notareal.hs/file");
+
+    let encrypted_json_data = json!({
+        "body": "Upload: my_image.jpg",
+        "file": {
+            "url": "mxc://notareal.hs/file",
+            "key": {
+                "kty": "oct",
+                "key_ops": ["encrypt", "decrypt"],
+                "alg": "A256CTR",
+                "k": "TLlG_OpX807zzQuuwv4QZGJ21_u7weemFGYJFszMn9A",
+                "ext": true
+            },
+            "iv": "S22dq3NAX8wAAAAAAAAAAA",
+            "hashes": {
+                "sha256": "aWOHudBnDkJ9IwaR1Nd8XKoI7DOrqDTwt6xDPfVGN6Q"
+            },
+            "v": "v2",
+        },
+        "info": {},
+    });
+
+    #[cfg(not(feature = "compat-encrypted-stickers"))]
+    {
+        from_json_value::<StickerEventContent>(encrypted_json_data).unwrap_err();
+    }
+    #[cfg(feature = "compat-encrypted-stickers")]
+    {
+        let encrypted_content =
+            from_json_value::<StickerEventContent>(encrypted_json_data).unwrap();
+        assert_eq!(encrypted_content.body, "Upload: my_image.jpg");
+        assert_matches!(
+            encrypted_content.source,
+            StickerMediaSource::Encrypted(encrypted_sticker_url)
+        );
+        assert_eq!(encrypted_sticker_url.url, "mxc://notareal.hs/file");
+    }
 }
 
 #[test]
@@ -126,7 +163,8 @@ fn event_deserialization() {
     assert_eq!(content.info.width, Some(uint!(1011)));
     assert_eq!(content.info.mimetype.as_deref(), Some("image/png"));
     assert_eq!(content.info.size, Some(uint!(84242)));
-    assert_eq!(content.url, "mxc://matrix.org/jxPXTKpyydzdHJkdFNZjTZrD");
+    assert_matches!(content.source, StickerMediaSource::Plain(sticker_url));
+    assert_eq!(sticker_url, "mxc://matrix.org/jxPXTKpyydzdHJkdFNZjTZrD");
 
     assert_matches!(content.info.thumbnail_source, Some(MediaSource::Plain(thumbnail_url)));
     assert_eq!(thumbnail_url, "mxc://matrix.org/irnsNRS2879");

crates/ruma/Cargo.toml

@@ -153,6 +153,10 @@ compat-signature-id = ["ruma-signatures?/compat-signature-id"]
 # Allow TagInfo to contain a stringified floating-point value for the `order` field.
 compat-tag-info = ["ruma-events?/compat-tag-info"]
 
+# Support encrypted stickers, as sent by several bridges.
+# https://github.com/matrix-org/matrix-spec/issues/1667
+compat-encrypted-stickers = ["ruma-events?/compat-encrypted-stickers"]
+
 # Specific compatibility for past ring public/private key documents.
 ring-compat = ["dep:ruma-signatures", "ruma-signatures?/ring-compat"]