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sha256 hash returns incorrect result if input's `(byteLength & 63) == 63`

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript
Domain
cryptography, testing-qa

Research direction

Start by reproducing the failure with the 191-byte and 575-byte cases in test/unit/index.test.ts, then run yarn test and compare sha256.digest output with the expected SHA-256 values shown here. Done means both regression cases, including inputs where byteLength % 64 == 63, produce the expected hexadecimal digests.

Written by the indexing model from the issue text.

Description

meta-bug meta-investigate prio-medium

The hash function returns incorrect result for any inputs where byteLength % 64 == 63. To reproduce create a test case where byte length % 64 == 63 and compare it against another implementation of sha256.

example test one:

 it("hex bytes of 191 byte length", function () {
      const inputStr = "1".repeat(382);
      const input = Buffer.from(inputStr, "hex");
      expect(input.length).to.be.equal(191);

      const output = Buffer.from(sha256.digest(input)).toString("hex");
      expect(output).to.be.equal("b8ffd888fe6ffff63cb0193ad93b0fee6bda8ea913e4e75424af7914f55d3411");
    });

example one output running yarn test

AssertionError: expected 'de66d39d769de0b512fe724191d53339a3efc…' to equal 'b8ffd888fe6ffff63cb0193ad93b0fee6bda8…'
      + expected - actual

      -de66d39d769de0b512fe724191d53339a3efc491875c25795a2c20bb7c03ad32
      +b8ffd888fe6ffff63cb0193ad93b0fee6bda8ea913e4e75424af7914f55d3411

example two

it("hex bytes of 676 byte length", function () {
      const inputStr = "1".repeat(1150);
      const input = Buffer.from(inputStr, "hex");
      expect(input.length).to.be.equal(575);

      const output = Buffer.from(sha256.digest(input)).toString("hex");
      expect(output).to.be.equal("fc6b0073005a8ce2b4bf9a9c482bb2b1707bc1dab06c0185752104157edb62c6");
    });

example two output running yarn test

digest function
         hex bytes of 575 byte length:

      AssertionError: expected '758a6d0187dfd01483d6a7e742bdda25a2f47…' to equal 'fc6b0073005a8ce2b4bf9a9c482bb2b1707bc…'
      + expected - actual

      -758a6d0187dfd01483d6a7e742bdda25a2f47ef804fed45423484b27a6717243
      +fc6b0073005a8ce2b4bf9a9c482bb2b1707bc1dab06c0185752104157edb62c6

      at Context.<anonymous> (test/unit/index.test.ts:22:28)
      at processImmediate (node:internal/timers:478:21)

I am still working through why this behavior occurs - I believe this could be an edge case in the math that is not handled correctly, any assistance on this would be greatly appreciated.

Dominant language
TypeScript
Stars
62
Forks
27
Avg merge
19h 2m
Merged PRs (30d)
6

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