isBase64: reject strings whose length is 1 mod 4 when padding is off#2816
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HrachShah wants to merge 1 commit into
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isBase64: reject strings whose length is 1 mod 4 when padding is off#2816HrachShah wants to merge 1 commit into
HrachShah wants to merge 1 commit into
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…(4k+1 lengths cannot be produced by any base64 encoding of any byte string, so isBase64 used to spuriously accept 'A', 'AAAAA', etc. as valid when padding was disabled)
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Bug: With padding: false, isBase64() accepted any string of valid base64 characters regardless of length, including impossible ones like 'A' (1 char), 'AAAAA' (5 chars), or 'AAAAAAAAA' (9 chars).
Why: A base64 string's length is always 0, 2, 3, 4, 6, 7, 8, 10, 11, 12, 14, ..., i.e. (length % 4) in {0, 2, 3}. A length of the form 4k+1 cannot be produced by any base64 encoding of any byte string. The padding-enabled path already enforced length % 4 == 0; the padding-disabled path was missing the analogous check.
Fix: After the character-class regex matches, also require length % 4 != 1 when padding is off.
Tests: New it() with both standard and urlSafe variants asserts that 1-mod-4 strings are rejected and 0/2/3-mod-4 strings (taken from real base64 encodings) are still accepted. Full suite: 319 passing (was 318).