crypto: fix unsigned conversion of 4-byte RSA publicExponent · nodejs/node@16e8c2b · GitHub

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crypto: fix unsigned conversion of 4-byte RSA publicExponent

`bigIntArrayToUnsignedInt` used the signed `<<` operator, so when the most significant byte of a 4-byte input had its top bit set (e.g. `[0x80, 0x00, 0x00, 0x01]`) the result was a negative Int32 instead of the intended unsigned 32-bit value. This caused any RSA `publicExponent` exactly 4 bytes long with the top bit set to be parsed incorrectly. Coerce the final value with `>>> 0` and add a unit test. Assisted-by: Claude <noreply@anthropic.com> Co-Authored-By: Claude <noreply@anthropic.com> Co-Authored-By: DeepView Autofix <276251120+deepview-autofix@users.noreply.github.com> Co-Authored-By: Nikita Skovoroda <chalkerx@gmail.com> Signed-off-by: Nikita Skovoroda <chalkerx@gmail.com> PR-URL: #62839 Reviewed-By: Filip Skokan <panva.ip@gmail.com>

1 parent c23db1c commit 16e8c2b
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+20-1Lines changed: 20 additions & 1 deletion

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• lib/internal/crypto
  • util.js
• test/parallel
  • test-webcrypto-util.js

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‎lib/internal/crypto/util.js‎

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+1-1Lines changed: 1 addition & 1 deletion

Original file line number	Diff line number	Diff line change
@@ -684,7 +684,7 @@ function bigIntArrayToUnsignedInt(input) {
684	684	result |= input[n] << 8 * n_reversed;
685	685	}
686	686
687		- return result;
	687	+ return result >>> 0;
688	688	}
689	689
690	690	function bigIntArrayToUnsignedBigInt(input) {

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‎test/parallel/test-webcrypto-util.js‎

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+19Lines changed: 19 additions & 0 deletions

Original file line number	Diff line number	Diff line change
@@ -8,10 +8,29 @@ if (!common.hasCrypto)
8	8	const assert = require('assert');
9	9
10	10	const {
	11	+ bigIntArrayToUnsignedInt,
11	12	normalizeAlgorithm,
12	13	validateKeyOps,
13	14	} = require('internal/crypto/util');
14	15
	16	+ // bigIntArrayToUnsignedInt must return an unsigned 32-bit value even when
	17	+ // the most significant byte has its top bit set. Otherwise the signed `<<`
	18	+ // operator yields a negative Int32 for inputs like [0x80, 0x00, 0x00, 0x01].
	19	+ {
	20	+ assert.strictEqual(
	21	+ bigIntArrayToUnsignedInt(new Uint8Array([0x80, 0x00, 0x00, 0x01])),
	22	+ 0x80000001);
	23	+ assert.strictEqual(
	24	+ bigIntArrayToUnsignedInt(new Uint8Array([0xff, 0xff, 0xff, 0xff])),
	25	+ 0xffffffff);
	26	+ assert.strictEqual(
	27	+ bigIntArrayToUnsignedInt(new Uint8Array([1, 0, 1])),
	28	+ 65537);
	29	+ assert.strictEqual(
	30	+ bigIntArrayToUnsignedInt(new Uint8Array([1, 0, 0, 0, 0])),
	31	+ undefined);
	32	+ }
	33	+
15	34	{
16	35	// Check that normalizeAlgorithm does not mutate object inputs.
17	36	const algorithm = { name: 'ECDSA', hash: 'SHA-256' };

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