fix(redaction): redact credentials split by control bytes - #1075
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Recreated from Twigpine#1013 (approved but unmerged). Original: euxaristia/zero:fix/969-redact-nul-esc-split
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Included review availability: Your plan provides up to 4 included reviews per hour; 2 remain after this review. WalkthroughRedactString now detects credential-shaped strings split by C0 or C1 control bytes. It collects and merges redaction spans on the original input, while preserving control bytes outside matched credentials. ChangesControl-Split Secret Redaction
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~50 minutes Change: Bug fix · Severity of issue fixed: Medium Suggested reviewers: Merge Risk: ⚪ Minimal · up to No actionable issue remains from the supplied evidence; the change is ready to merge after normal checks. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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Inline comments:
In `@internal/redaction/redaction.go`:
- Around line 639-647: Update both slash-handling early returns to return only
for digit-free OpenAI kebab candidates, using isOpenAI, runningDigits,
hasInteriorHyphen, and knownOpenAIKeyPrefix; otherwise continue candidate
processing so credential suffixes are redacted. Add regression coverage for the
AKIA inputs, split Anthropic key, and valid-prefix suffix case, asserting no
credential fragment remains visible.
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internal/redaction/redaction.gointernal/redaction/redaction_test.gointernal/redaction/split_harness_test.go
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Vasanthdev2004
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Up front, so it can be weighed: I have the other open PR for #969, #1067, so this is a review of a competitor. I ran every measurement below identically against main, this head and mine, and I've said where this one is better than mine. The two findings I'm requesting changes on hold against main and this head alone, without mine.
This is careful work. Of the boundary cases jatmn used to break my first version, all but the text-after-a-key one (below) come out right here: a key after a NUL, two JWTs split by NUL, ESC or ZWSP, a GitHub key before a JWT, a split key after a space, inside JSON, and glued to a word. In isolation, every shape I tried (AWS, GitLab, Google, GitHub, Anthropic, OpenAI, Slack) split by NUL, ESC, DEL, C1 CSI or C1 NEL, at the start, middle or end, behind nothing, a space or a bracket, redacts: 0 of 315 leak. On the ordinary path it allocates less than half what main does, 64.6 MB against 146.3 MB for 4 MiB, where mine costs slightly more than main. And it fixes a leak on main that mine leaves alone: two AWS keys glued together (AKIA…AKIA…) redact both here, where main emits the second in full.
1. A new leak on input with no control characters
A JWT immediately after an AWS key:
input AKIAIOSFODNN7EXAMPLE + <jwt>
main [REDACTED][REDACTED]
here [REDACTED]eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIn0.dBjftJeZ...
The whole token comes out, header, payload and signature. The same happens with ASIA and with id= in front. The cause is the span collection in RedactString:
for _, shape := range secretShapes {
allSpans = append(allSpans, findSpansForShape(redacted, shape, false)...)
}
redacted = applySpans(redacted, allSpans, replacement)Every shape is matched against the same unmodified string. main applied the shapes one at a time, so the AWS replacement left a ] in front of eyJ, and that ] is the word boundary the JWT pattern's leading \b needed. Matched up front, the JWT follows an E, there is no boundary, and it never matches. This is outside #969's scope and would reach every user. The fix probably wants a span already claimed by an earlier shape to count as a boundary for the shapes after it.
I found it with a differential rather than by reading: 6,000 seeded inputs with no control or format characters, run through both trees. Three outputs differ from main. Two are the glued-AWS-key improvement above, and this is the third.
2. A / after the key, in the same run, defeats the split handling, including for ESC
This one is inside the PR's own scope:
AKIAIOSF<DEL>ODNN7EXAMPLE redacted
AKIAIOSF<DEL>ODNN7EXAMPLE/ survives
AKIAIOSF<DEL>ODNN7EXAMPLE. redacted
ASIAIOSFODNN<CSI>7EXAMPLE.path redacted
ASIAIOSFODNN<CSI>7EXAMPLE.path/to/x survives
glpat-abcdef<ESC>ghij0123456789/ survives
A slash later in the same whitespace-free run is enough, and ESC is one of the two bytes #969 reports. A slash before the key does not do it (path/AKIAIOSF<DEL>ODNN7EXAMPLE redacts), so it's specific to what follows. startsIndependentCredential cuts its token at / and \ alongside control bytes and space, which looks like the place to start, but I haven't traced it through, so take that as a pointer rather than a diagnosis. A key next to a slash is not an edge case, since it describes URLs, paths and anything written as key/….
3. Zero-width space and BOM are not treated as gaps
Gaps are classified with unicode.IsControl, which is the Cc category only. U+200B, U+FEFF, U+00AD and U+2060 are Cf, so a key split by one is never rejoined:
token/ASIAIO<U+200B>SFODNN7EXAMPLE unchanged; the full key is back once the ZWSP is dropped
Over a second 6,000 inputs with invisible characters mixed in, the outputs that still contain a known credential after dropping them:
main 2112
this head 915
#1067 158
Of the 765 that leak here and not in #1067, 743 have a U+200B or U+FEFF left in them, and 18 of the remaining 22 have a slash after the key in the same run, which is item 2. I haven't separated the last four; one of them leaks on main too and #1067 only catches it incidentally, so it isn't a mark against this PR. Whether Cf is in scope for #969 is for the maintainers to decide, since the issue names NUL and ESC. But a zero-width space is the split most likely to reach a real key, because chat clients and rich-text editors insert them and copy-paste keeps them, so it's worth deciding on purpose rather than by what IsControl happens to cover.
Two smaller behaviour changes
- Text after a key is eaten.
sk-proj-abcdefghijklmnopqrstuvwxyz+ NUL +ordinary prose herebecomes[REDACTED] prose here, wheremainkeeps\x00ordinary. jatmn required that exact case fixed on #1067 ("preserve original bytes outside each redaction"). - Raw bytes 0x80 to 0x9F are treated as gaps before decoding. At a rune boundary those are invalid UTF-8, not C1 characters; real C1 is two bytes,
0xC2 0x80onwards, and theunicode.IsControlbranch already handles it. So malformed input now joins across a stray byte. That may be intended, but it's a scope change worth stating, since the #1067 review asked to keep malformed bytes out.
All nine checks are green at 90c44366, and the package's own tests pass here on windows/amd64. The regression in 1 and the leak in 2 are what I'm requesting changes on. The maintainers will need to pick between two PRs for one issue either way.
- A span claimed by an earlier shape now acts as a word boundary for later shapes: each shape retries matches starting exactly where an earlier span ended (via start-anchored pattern variants), so a JWT immediately after an AWS key is redacted instead of leaking in full. - A slash or backslash after a control-byte gap no longer abandons a candidate that has not validated yet; the early return now applies only to digit-free OpenAI kebab fragments, so split credentials before a slash or path are still redacted. - Add regression tests for both findings in split_harness_test.go.
Vasanthdev2004
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Same disclosure as last time: #1067 is mine, and every number below was measured the same way on main, on both heads of this PR and on #1067.
Both findings are fixed. An AWS key followed by a JWT redacts both again, with or without id= in front, and the three slash cases that survived now redact. The two new tests fail on 90c44366 with the messages they claim and pass here. On the 6,000 control-free inputs, five outputs now differ from main, and each one is a second credential glued to the first that main leaves visible and this head redacts.
Two new problems below. The leak in 1 and the first loop in 2 were already on 90c44366, and I should have caught them in the first round. The second loop in 2 is new in 8ca128bd.
1. A split token after a complete one of the same kind leaks
A complete credential, one bare control character, then a second credential of the same kind with a split in it:
in ghp_zyxwvutsrqponmlkjihgfedcba9876543210 <NUL> ghp_abcdefghijklmnop <NUL> qrstuvwxyz0123456789
out [REDACTED]_abcdefghijklmnop\x00qrstuvwxyz0123456789
Everything after ghp comes out, so the second token is back once you put ghp in front of it. gho_ and ghs_ do the same, and so do ESC, DEL and NEL as the separator. JWTs too: the second token's header is swallowed and its payload and signature are emitted, and since the header is nearly always one of a few standard values, that token can be rebuilt as well. With a space as the separator, or with the second token unsplit, both redact.
As far as I can tell: the gh[pousr]_ body class is [A-Za-z0-9], so the first match carries on across the gap, takes ghp, and stops at _. A JWT signature does the same with the next header and stops at the .. startsIndependentCredential only ends a candidate that is already valid when the next token is complete before its own first control byte, so a split second token never ends the first match. Pairs of different kinds get away with it because the second shape runs its own search and the spans are merged. A same-kind pair can't, because the first match has already eaten the start the second one needs.
To size it I ran every pair of the nine shapes, with NUL, ESC or a space between them and the second key split at five points (1,134 inputs), and counted the inputs where everything after the second key's fixed prefix (for a JWT, its header) is visible while the unsplit input hides it. Here: 14, all of them ghp then ghp or JWT then JWT. main: 756, since it has no split handling. #1067: none, though it shows the tail of a key whose front part was complete by itself in 108 of them, which is the limit its description names.
2. Two loops go quadratic, and neither input needs a control character
1 MiB 2 MiB 4 MiB 8 MiB
AWS keys glued end to end
main 0.30s 0.61s 1.31s 2.34s
this head 0.77s 2.18s 7.47s 29.2s
glpat key, space, AWS key, space, ...
main 0.28s 0.58s 1.10s
90c44366 0.36s 0.72s 1.34s
this head 0.53s 1.41s 4.21s
The first is the abuts check in findSpansForShape, which scans every span found so far for each match that follows a word byte. Comparing against the most recent span instead brings it back to linear (2.31s at 8 MiB). The second is the retry pass from 8ca128bd: it checks every claimed end from the earlier shapes against every span of the current shape, so a log with many keys of two kinds pays for the product. Walking the sorted ends alongside the shape's spans in position order, instead of each end against all of them, would keep it linear.
Unchanged from the first round, not blocking
- Zero-width characters (Cf) still aren't gaps. Of the 871 corpus inputs (of 6,000) that still show a credential here, down from 915, 794 have one left in the output. That's the maintainers' call, as before.
- Text after a key is still eaten:
sk-proj-…<NUL>ordinary prose heregives[REDACTED] prose here, andglpat-…<NUL>12345gives[REDACTED].
CI is 9/9 green on 8ca128bd, and internal/redaction passes here with and without -race. The leak in 1 and the two loops in 2 are what I'm requesting changes on.
2 participants
Fixes #969
Summary
Redact credentials split by C0/C1 control bytes while preserving surrounding original text and separators. Inputs without secrets remain byte-for-byte unchanged.
Changes
gitleaks:allowcomments and construct synthetic Slack fixtures at runtime to avoid committing token-shaped literals.Test plan
Completed with Go 1.26.6:
make fmt-check,go vet ./..., and full Linuxgo test ./....go run ./cmd/zero-release buildandgo run ./cmd/zero-release smoke.internal/redactionandgit diff HEAD --check.The incomplete-prefix regression failed on the previous head with
incomplete prefix ... leaked. It covers five credential prefixes across NUL, ESC, raw C1, UTF-8 C1, and mixed controls, plus complete neighbors and non-secret prose. Full validation and race tests passed with the final fix.Prior reviewer feedback addressed
Addresses the applicable feedback from #978 and this PR: preserve original bytes outside redacted spans, bound gap-processing costs, annotate synthetic secrets, remove flaky wall-clock assertions, and close the unequal-length neighboring-JWT leak, and prevent incomplete known prefixes from exposing a valid candidate's suffix. Matching retains the agreed control-character scope, leaving tab, LF, CR, and Unicode format characters outside the gap-removal rules.
Summary by CodeRabbit
Recreated from closed PR #1013 by @euxaristia (approved but unmerged, rebased onto current main). Original branch: euxaristia/zero:fix/969-redact-nul-esc-split