fix(random): Enhance security by replacing platform-specific randomizer code with Rust's bindings

[sergei-boiko-trustwallet]

This pull request refactors and unifies the implementation of cryptographically secure random number generation across the codebase. It removes platform-specific random number generator code (for JNI, Swift, and WASM), and replaces it with a single Rust-backed implementation that is exposed to C++ via FFI. The new approach improves code maintainability, error handling, and testability, and ensures consistent random byte generation across all platforms.

Key changes include:

Core random number generation refactor:

• Removed platform-specific random number generator implementations in jni/cpp/Random.cpp, swift/Sources/SecRandom.m, and wasm/src/Random.cpp, consolidating all random byte generation through a new Rust FFI function (crypto_random_buffer).
• Replaced the previous C++ random_buffer implementation with a wrapper that calls the Rust FFI function, and updated the API to return a status code (RandomResult).

Rust FFI and memory handling:

• Added crypto_random_buffer in Rust (rust/tw_crypto/src/ffi/crypto_random.rs), which uses rand::thread_rng() to fill buffers securely, and defined error codes for FFI.
• Introduced CByteArrayMut in Rust for safe FFI buffer handling.
• Registered the new Rust FFI module in the main FFI mod.

Error handling and usage updates:

• Updated all C++ code that generates random bytes (e.g., for IVs, salts, private keys) to use the new Random::random_buffer API and to handle errors more robustly (throwing exceptions or returning null on failure instead of aborting or terminating).
• Improved error propagation in Rust mnemonic generation to handle random generator failures explicitly.

Testing:

• Added comprehensive Rust FFI tests for the new crypto_random_buffer function, including edge cases for buffer validity and randomness.

These changes ensure a single, secure, and consistent random number generation mechanism across all supported platforms, simplify the codebase, and improve error handling for cryptographic operations.

[Copilot]

Pull request overview

This pull request replaces platform-specific random number generation implementations (JNI, Swift, WASM) with a unified Rust-based solution. The changes consolidate cryptographically secure random number generation into a single implementation using rand::thread_rng(), exposed to C++ via FFI. This simplifies the codebase, improves maintainability, and provides consistent error handling across all platforms.

Changes:

• Removed platform-specific random generators (JNI/Java, Swift/SecRandom, WASM/JavaScript) in favor of Rust's rand::thread_rng()
• Added Rust FFI function crypto_random_buffer with comprehensive error handling and tests
• Updated C++ random buffer API to return status codes and handle errors properly instead of aborting/terminating

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
wasm/src/Random.cpp	Removed WASM-specific JavaScript-based random implementation
swift/Sources/SecRandom.m	Removed Swift-specific SecRandom implementation
jni/cpp/Random.cpp	Removed JNI-specific Java SecureRandom implementation
src/rand.h	Updated to return status codes and use TW::Random namespace
src/rand.cpp	Replaced platform-specific code with Rust FFI wrapper
src/interface/TWPrivateKey.cpp	Updated to handle random generation errors gracefully
src/Keystore/ScryptParameters.cpp	Added error handling for salt generation
src/Keystore/PBKDF2Parameters.cpp	Added error handling for salt generation
src/Keystore/AESParameters.cpp	Added error handling for IV generation
src/FIO/Encryption.cpp	Added error handling for IV generation
rust/tw_memory/src/ffi/mod.rs	Registered new c_byte_array_mut module
rust/tw_memory/src/ffi/c_byte_array_mut.rs	Added mutable FFI byte array wrapper
rust/tw_crypto/src/ffi/mod.rs	Registered new crypto_random module
rust/tw_crypto/src/ffi/crypto_random.rs	Implemented crypto_random_buffer FFI function
rust/tw_crypto/src/crypto_mnemonic/mnemonic.rs	Updated to use try_fill_bytes with proper error handling
rust/tw_crypto/src/crypto_mnemonic/error.rs	Added RandGeneratorError variant
rust/tw_crypto/tests/crypto_random_ffi.rs	Added comprehensive FFI tests

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Binary size comparison

➡️ aarch64-apple-ios:

- 15.25 MB
+ 15.25 MB 	 +1 KB

➡️ aarch64-apple-ios-sim: 15.25 MB

➡️ aarch64-linux-android:

- 20.10 MB
+ 20.10 MB 	 +1 KB

➡️ armv7-linux-androideabi: 17.31 MB

➡️ wasm32-unknown-emscripten: 14.85 MB