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buffer: fix atob input validation #42539

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merged 3 commits into from Apr 2, 2022
Merged

buffer: fix atob input validation #42539

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ae80c08
buffer: fix `atob` input validation
aduh95 Mar 31, 2022
3be9788
fixup! buffer: fix `atob` input validation
aduh95 Mar 31, 2022
a63982f
fixup! buffer: fix `atob` input validation
aduh95 Mar 31, 2022
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26 changes: 23 additions & 3 deletions lib/buffer.js
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Expand Up @@ -23,8 +23,10 @@

const {
Array,
ArrayFrom,
ArrayIsArray,
ArrayPrototypeForEach,
ArrayPrototypeIncludes,
MathFloor,
MathMin,
MathTrunc,
Expand Down Expand Up @@ -1230,8 +1232,25 @@ function btoa(input) {
return buf.toString('base64');
}

const kBase64Digits =
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
// Refs: https://infra.spec.whatwg.org/#forgiving-base64-decode
const kForgivingBase64AllowedChars = [
// ASCII whitespace
// Refs: https://infra.spec.whatwg.org/#ascii-whitespace
0x09, 0x0A, 0x0C, 0x0D, 0x20,

// Uppercase letters
...ArrayFrom({ length: 26 }, (_, i) => StringPrototypeCharCodeAt('A') + i),

// Lowercase letters
...ArrayFrom({ length: 26 }, (_, i) => StringPrototypeCharCodeAt('a') + i),

// Decimal digits
...ArrayFrom({ length: 10 }, (_, i) => StringPrototypeCharCodeAt('0') + i),

0x2B, // +
0x2F, // /
0x3D, // =
];

function atob(input) {
// The implementation here has not been performance optimized in any way and
Expand All @@ -1242,7 +1261,8 @@ function atob(input) {
}
input = `${input}`;
for (let n = 0; n < input.length; n++) {
if (!kBase64Digits.includes(input[n]))
if (!ArrayPrototypeIncludes(kForgivingBase64AllowedChars,
StringPrototypeCharCodeAt(input, n)))
throw lazyDOMException('Invalid character', 'InvalidCharacterError');
}
return Buffer.from(input, 'base64').toString('latin1');
Expand Down
3 changes: 3 additions & 0 deletions test/parallel/test-btoa-atob.js
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Expand Up @@ -12,3 +12,6 @@ strictEqual(globalThis.btoa, buffer.btoa);
// Throws type error on no argument passed
throws(() => buffer.atob(), /TypeError/);
throws(() => buffer.btoa(), /TypeError/);

strictEqual(atob(' '), '');
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strictEqual(atob(' YW\tJ\njZA=\r= '), 'abcd');