feat: Add support for the new dehydrated device format

Changelog: Added support for [MSC3814](matrix-org/matrix-spec-proposals#3814),
    allowing users to export an Olm Account in a serialized format. The
    serialized account can be uploaded to a server for safekeeping until
    needed.

Cargo.toml

@@ -49,7 +49,7 @@ arrayvec = { version = "0.7.6", features = ["serde"] }
 base64 = "0.22.1"
 base64ct = { version = "1.6.0", features = ["std", "alloc"] }
 cbc = { version = "0.1.2", features = ["std"] }
-chacha20poly1305 = "0.10.1"
+chacha20poly1305 = { version = "0.10.1", features = ["std"] }
 curve25519-dalek = { version = "4.1.3", default-features = false, features = ["zeroize"] }
 ed25519-dalek = { version = "2.1.1", default-features = false, features = ["rand_core", "std", "serde", "hazmat", "zeroize"] }
 getrandom = "0.2.15"

afl/rehydrate-device/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "rehydrate-device"
+version = "0.1.0"
+publish = false
+edition = "2021"
+
+[dependencies]
+afl = "*"
+
+[dependencies.vodozemac]
+path = "../.."
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]

afl/rehydrate-device/rust-toolchain.toml

@@ -0,0 +1,2 @@
+[toolchain]
+channel = "nightly"

afl/rehydrate-device/src/main.rs

@@ -0,0 +1,8 @@
+use afl::fuzz;
+use vodozemac::olm::Account;
+
+fn main() {
+    fuzz!(|data: &[u8]| {
+        let _ = Account::from_decrypted_dehydrated_device(data);
+    });
+}

src/lib.rs

@@ -232,7 +232,6 @@ pub enum PickleError {
 
 /// Error type describing the various ways libolm pickles can fail to be
 /// decoded.
-#[cfg(feature = "libolm-compat")]
 #[derive(Debug, thiserror::Error)]
 pub enum LibolmPickleError {
     /// The pickle is missing a valid version.
@@ -262,6 +261,30 @@ pub enum LibolmPickleError {
     Encode(#[from] matrix_pickle::EncodeError),
 }
 
+/// Error type describing the various ways dehydrated devices can fail to be
+/// decoded.
+#[derive(Debug, thiserror::Error)]
+pub enum DehydratedDeviceError {
+    /// The pickle is missing a valid version.
+    #[error("The pickle doesn't contain a version")]
+    MissingVersion,
+    /// The pickle has a unsupported version.
+    #[error("The pickle uses an unsupported version, expected {0}, got {1}")]
+    Version(u32, u32),
+    /// Invalid nonce.
+    #[error("The nonce was invalid")]
+    InvalidNonce,
+    /// The pickle wasn't valid base64.
+    #[error("The pickle wasn't valid base64: {0}")]
+    Base64(#[from] Base64DecodeError),
+    /// The pickle could not have been decrypted.
+    #[error("The pickle couldn't be decrypted: {0}")]
+    Decryption(#[from] chacha20poly1305::aead::Error),
+    /// There was an error with the libolm pickle format
+    #[error(transparent)]
+    LibolmPickle(#[from] LibolmPickleError),
+}
+
 /// Error type describing the different ways message decoding can fail.
 #[derive(Debug, thiserror::Error)]
 pub enum DecodeError {