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@m2c/core

v0.1.0

Published

Shared protocol primitives (HMAC signing, error taxonomy, money) for the M2C SDKs.

Vulnerabilities

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  • 0Medium
  • 0Low

Links

Maintainers

m2cmarketsm2cmarkets

Keywords

m2cpaymentshmacsdk

Readme

@m2c/core

Shared protocol primitives for the M2C SDKs. You normally do not depend on this directly - use @m2c/server (merchant backend) or @m2c/vendor (payment vendor), which build on it.

It exists so the security-sensitive parts of the protocol have exactly one implementation:

  • sign(secret, body, { timestampSeconds? }) - produce the X-M2C-Signature / X-M2C-Timestamp pair (HMAC-SHA256 over timestamp + "\n" + body).
  • verify(secret, body, signature, timestamp, { maxSkewSeconds?, nowSeconds? })
    • constant-time verification with the full failure taxonomy.
  • M2CError / M2CSignatureError (with a reason: missing | incomplete | malformed | timestamp_skew | mismatch | empty_secret).
  • getHeader, the header-name constants, and the skew default.
  • MIN_MONETARY_VALUE / MAX_MONETARY_VALUE + assertMonetaryAmount for the major-units-at-the-wire boundary check.

Zero runtime dependencies (built on node:crypto). Requires Node 18+.

The malformed-vs-missing distinction is load-bearing: a malformed-but-present signature is a tampering signal and must always be rejected, even where a rollout flag tolerates a fully-absent one. Both SDKs and the Go server (server/vendor/hmac.go) share this behavior, anchored by a known-answer test vector asserted in every suite.