[notorious-d-e-v]

Summary

MetaMask can change binary Solana messages while converting them to text, then return the original message with a signature that does not match it. This fix signs the original bytes so applications can verify the returned signature correctly.

Explanation

The shared signing helper currently converts Base64 input to UTF-8 text before signing. The text decoder removes NUL bytes, replaces invalid UTF-8 sequences, and strips a leading byte order mark. The response nevertheless returns the unchanged Base64 input as signedMessage.

Decode Base64 directly to a byte array and pass those bytes to createSignableMessage. Both signMessage and signMessages use this helper. Existing text-message and Sign-In With Solana fixtures remain valid.

Regression tests cover NUL bytes, invalid UTF-8, a byte order mark, all 256 byte values, Unicode text, and batch signing. A separate test checks that moving a NUL byte changes the signature and prevents verification against the other message. No dependencies change.

Wallet confirmation rendering still converts messages to text; improving binary-message display is separate from this signature correctness fix.

Validation

• Before the fix: six new regression cases fail against the existing implementation; the Unicode control passes.
• After the fix: all 120 WalletService tests pass.
• Full Solana package suite: 89 suites pass; 1,055 tests pass, 5 are skipped, and 1 is marked todo. Coverage thresholds pass.
• Solana Snap build and package TypeScript check pass.
• Repository type checks, ESLint, formatting, Yarn constraints, dependency checks, and README checks pass.
• Solana package changelog validation passes.

Tested with Node.js 24.12.0 and Yarn 4.17.1 using local mock endpoints. No wallet approval or funded transaction was performed for these tests.

References

Fixes #506. The issue includes the supplied browser capture and independent verification of its actual wallet-returned signature.

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating the package changelog
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them (not applicable)