security(twdata): Zeroize every TWData instance in TWDataDelete, and other TWData improvements

[sergei-boiko-trustwallet]

This pull request refactors the TWData interface and related code for improved safety, clarity, and memory handling. The most significant changes include removing the TWDataGet function, updating the semantics and error handling for TWDataCopyBytes and TWDataReplaceBytes, and ensuring sensitive data is securely erased before deletion. Test cases have also been updated to reflect these changes and improve error coverage.

API changes and safety improvements

• Removed the TWDataGet function from both the header and implementation, encouraging direct use of TWDataBytes for accessing data and simplifying the API.
• Updated TWDataCopyBytes and TWDataReplaceBytes to return an integer status code (0 for success, -1 for failure) and added bounds checking to prevent invalid memory access. The header documentation and implementation were both updated accordingly.
• Adjusted usage of these functions throughout the codebase to check return values and handle errors gracefully, including in TWPrivateKeyCreateWithData and TWPrivateKeyIsValid.

Memory handling and security

• Enhanced deletion functions for TWData and TWString to securely erase memory using memzero before freeing, reducing the risk of sensitive data leakage.
• Included memzero.h for secure memory erasure.

Test updates and improvements

• Removed or replaced test cases that used the deprecated TWDataGet function, switching to direct buffer access via TWDataBytes.
• Updated tests for error handling in TWDataCopyBytes and TWDataReplaceBytes, adding new cases to verify correct behavior for out-of-bounds and zero-size operations.
• Simplified and clarified tests for various decode functions, removing unnecessary wrappers and directly checking for nullptr results.
  These changes collectively improve the safety, maintainability, and correctness of the codebase, especially around memory management and error handling.

[Copilot]

Pull request overview

This PR hardens TWData lifecycle handling in the Trust Wallet Core C interface by attempting to securely wipe TWData contents in TWDataDelete before deallocation.

Changes:

• Add <TrezorCrypto/memzero.h> include to src/interface/TWData.cpp.
• Call memzero on the underlying Data buffer in TWDataDelete prior to delete.

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Binary size comparison

➡️ aarch64-apple-ios: 14.34 MB

➡️ aarch64-apple-ios-sim: 14.34 MB

➡️ aarch64-linux-android: 18.77 MB

➡️ armv7-linux-androideabi: 16.20 MB

➡️ wasm32-unknown-emscripten: 13.68 MB

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Pull request overview

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Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

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Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

tests/interface/TWDataTests.cpp:86

• Test coverage: since TWDataSet now guards against out-of-range indices, add a unit test that calls TWDataSet(data, TWDataSize(data), ...) (and/or a larger index) and asserts the data remains unchanged. This would lock in the new safety behavior and prevent regressions back to OOB writes.

TEST(TWData, Set) {
    const auto data = WRAPD(TWDataCreateWithHexString(STRING("deadbeef").get()));
    assertHexEqual(data, "deadbeef");
    TWDataSet(data.get(), 1, 0xff);
    assertHexEqual(data, "deffbeef");
}

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Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 7 comments.

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