fix(crypto): Serialize sender data msk in base64 instead of numbers

crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data.rs

@@ -12,13 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::cmp::Ordering;
+use std::{cmp::Ordering, fmt};
 
 use ruma::{DeviceId, OwnedDeviceId, OwnedUserId, UserId};
-use serde::{Deserialize, Serialize};
+use serde::{de, de::Visitor, Deserialize, Deserializer, Serialize};
 use vodozemac::Ed25519PublicKey;
 
-use crate::types::DeviceKeys;
+use crate::types::{serialize_ed25519_key, DeviceKeys};
 
 /// Information about the sender of a megolm session where we know the
 /// cross-signing identity of the sender.
@@ -33,9 +33,55 @@ pub struct KnownSenderData {
     pub device_id: Option<OwnedDeviceId>,
 
     /// The cross-signing key of the user who established this session.
+    #[serde(
+        serialize_with = "serialize_ed25519_key",
+        deserialize_with = "deserialize_sender_msk_base64_or_array"
+    )]
     pub master_key: Box<Ed25519PublicKey>,
 }
 
+/// In an initial version the master key was serialized as an array of number,
+/// it is now exported in base64. This code adds backward compatibility.
+pub(crate) fn deserialize_sender_msk_base64_or_array<'de, D>(
+    de: D,
+) -> Result<Box<Ed25519PublicKey>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    struct KeyVisitor;
+
+    impl<'de> Visitor<'de> for KeyVisitor {
+        type Value = Box<Ed25519PublicKey>;
+
+        fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+            write!(formatter, "a base64 string or an array of 32 bytes")
+        }
+
+        fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            let decoded = Ed25519PublicKey::from_base64(v)
+                .map_err(|_| de::Error::custom("Base64 decoding error"))?;
+            Ok(Box::new(decoded))
+        }
+
+        fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+        where
+            A: de::SeqAccess<'de>,
+        {
+            let mut buf = [0u8; 32];
+            for (i, item) in buf.iter_mut().enumerate() {
+                *item = seq.next_element()?.ok_or_else(|| de::Error::invalid_length(i, &self))?;
+            }
+            let key = Ed25519PublicKey::from_slice(&buf).map_err(|e| de::Error::custom(&e))?;
+            Ok(Box::new(key))
+        }
+    }
+
+    de.deserialize_any(KeyVisitor)
+}
+
 /// Information on the device and user that sent the megolm session data to us
 ///
 /// Sessions start off in `UnknownDevice` state, and progress into `DeviceInfo`
@@ -287,6 +333,7 @@ mod tests {
     use ruma::{
         device_id, owned_device_id, owned_user_id, user_id, DeviceKeyAlgorithm, DeviceKeyId,
     };
+    use serde_json::json;
     use vodozemac::{Curve25519PublicKey, Ed25519PublicKey};
 
     use super::SenderData;
@@ -530,4 +577,25 @@ mod tests {
             master_key: Box::new(Ed25519PublicKey::from_slice(&[1u8; 32]).unwrap()),
         }));
     }
+
+    #[test]
+    fn test_sender_known_data_migration() {
+        let old_format = json!(
+        {
+            "SenderVerified": {
+                "user_id": "@foo:bar.baz",
+                "device_id": null,
+                "master_key": [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+            }
+        });
+
+        let migrated: SenderData = serde_json::from_value(old_format).unwrap();
+
+        assert_let!(SenderData::SenderVerified(KnownSenderData { master_key, .. }) = migrated);
+
+        assert_eq!(
+            master_key.to_base64(),
+            Ed25519PublicKey::from_slice(&[0u8; 32]).unwrap().to_base64()
+        );
+    }
 }

crates/matrix-sdk-crypto/src/olm/group_sessions/snapshots/matrix_sdk_crypto__olm__group_sessions__sender_data__tests__snapshot_sender_data-4.snap

@@ -6,39 +6,6 @@ expression: "SenderData::VerificationViolation(KnownSenderData\n{\n    user_id:
   "VerificationViolation": {
     "user_id": "@foo:bar.baz",
     "device_id": "DEV",
-    "master_key": [
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0,
-      0
-    ]
+    "master_key": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
   }
 }

crates/matrix-sdk-crypto/src/olm/group_sessions/snapshots/matrix_sdk_crypto__olm__group_sessions__sender_data__tests__snapshot_sender_data-5.snap

@@ -6,39 +6,6 @@ expression: "SenderData::SenderUnverified(KnownSenderData\n{\n    user_id: owned
   "SenderUnverified": {
     "user_id": "@foo:bar.baz",
     "device_id": null,
-    "master_key": [
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1
-    ]
+    "master_key": "AQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQE"
   }
 }

crates/matrix-sdk-crypto/src/olm/group_sessions/snapshots/matrix_sdk_crypto__olm__group_sessions__sender_data__tests__snapshot_sender_data-6.snap

@@ -6,39 +6,6 @@ expression: "SenderData::SenderVerified(KnownSenderData\n{\n    user_id: owned_u
   "SenderVerified": {
     "user_id": "@foo:bar.baz",
     "device_id": null,
-    "master_key": [
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1,
-      1
-    ]
+    "master_key": "AQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQE"
   }
 }