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…FFFF Since the refactor in owasp-modsecurity#3284 (2.9.9) the output pointer always advanced by six bytes after sprintf("%%u%04x"), so a code point that needs five hex digits (anything above U+FFFF) lost its last digit to the next write or to the terminating NUL: U+1F600 came out as "%u1f60". Advance by the number of bytes sprintf actually wrote. While there, fix two adjacent checks in the same function: bytes_left was never decremented, so the "enough bytes left" guards compared the total length instead of the remaining length and a truncated sequence at the end of the value was examined past input_len; and an 0xF4 lead byte with a second byte >= 0x90 (U+110000 and above, outside Unicode) was accepted as a valid four-byte sequence. Add four-byte, above-U+10FFFF and truncated-sequence cases to the utf8toUnicode unit tests, which had no four-byte input at all. Fixes owasp-modsecurity#3684 Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Cq9GqRpB4wzTFnEUvQaUJg
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Sonar flagged the sprintf call added by the previous commit. The output buffer is sized for the worst case, so this only makes the bound explicit. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Mhspv9mxtMSiWC1U8mVH1H
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…e_ex The two-, three- and four-byte branches repeated the same pattern: check the byte count, check each continuation byte for binary 10, shift in six bits. Move that into utf8_decode_sequence(), which derives the sequence length from the lead byte and loops over the continuation bytes. The NUL special case and the surrogate, range and overlong checks stay in the caller, so the output is unchanged. SonarCloud reported a cognitive complexity of 51 for the function on PR owasp-modsecurity#3685 (accepted there); it is now 17, with 10 for the helper. Verified output-identical to the previous version with a standalone harness under ASan and UBSan: every input of 1 to 3 bytes, every 4-byte input with a high lead byte and a third of the fourth-byte values, and 20 million random 4 to 15 byte inputs biased to high bytes and NUL: 758,263,296 cases, 0 mismatches. tests/tfn/utf8toUnicode.t passes 11/11. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Tz1sULBvqAwnRreKh5eC9h
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Proposed changes
Fixes #3684. Related to #1211 (the 4-vs-6 digit output ambiguity, which this PR does not change).
Since the refactor in #3284 (first released in 2.9.9)
utf8_unicode_inplace_ex()always advanced the output pointer by six bytes aftersprintf("%%u%04x"), so any code point above U+FFFF (five hex digits) lost its last digit to the next write or to the terminating NUL: U+1F600 came out as%u1f60. The pointer now advances by whatsprintf()actually wrote.Two adjacent checks in the same function are fixed as well:
bytes_leftwas never decremented, so the "enough bytes left" guards compared against the total input length instead of the remaining length, and a truncated sequence at the end of the value was examined pastinput_len(bounded in practice by the NUL that terminates variable values, but wrong).0xF4lead byte with a second byte>= 0x90(U+110000 and above, outside Unicode) was accepted as a valid four-byte sequence; it is now passed through like any other invalid sequence.Output is otherwise unchanged, including the pre-existing handling of a NUL byte (
%u00xxfrom #3284) and of the BMP.Tests
tests/tfn/utf8toUnicode.thad no four-byte input at all. Four cases are added: supplementary-plane characters, a four-byte character followed by ASCII, a sequence above U+10FFFF, and a truncated sequence at the end of the input. Against the unmodifiedv2/mastersource the first three fail (Passed: 8; Failed: 3); with this patch all 11 pass andmake testis green (macOS, Apache 2.4 from Homebrew, PCRE2 10.49). The function was also exercised standalone under AddressSanitizer with the same inputs.🤖 Generated with Claude Code