fix(redaction): redact credentials split by an invisible character - #1067
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Every shape matcher in RedactString describes a contiguous run of body characters, and none of their classes admits a control or format character. One NUL or ESC dropped into the body of a key therefore ended the match and both fragments were emitted untouched. Whoever read that output next saw the original key back, because nothing about those characters was ever displayed: a terminal eats the escape, a log viewer or JSON consumer strips the control byte, and a copy-paste drops both. The matchers now also run over a copy with those characters removed, and the spans they find are mapped back so the replacement covers the original bytes, separators included. Emitting the compacted copy would hand the caller a different string than the one they passed in, and leaving a separator behind would read as two secrets where there was one. Written against the character classes rather than the two bytes in the report, because every other Cc and Cf character behaves the same way: BEL, backspace, DEL, the C1 controls, zero-width space and joiner, word joiner, BOM and soft hyphen all split a key on main. Tab, newline and carriage return are deliberately excluded and a test says so: they are real text structure, a credential broken across a line is visible to whoever reads it rather than hidden from them, and stripping them would let one match span a line break and replace unrelated lines. Text with no such character takes exactly the path it took before, decided by a byte scan that allocates nothing, so the common case is unchanged at 51 allocations. Text that carries control characters and no credential pays for one compacted copy and a second pattern pass. Fixes #969
The malformed-UTF8 legs only asked whether the key was gone, so a decoder that measured an invalid byte as the three bytes of U+FFFD still passed: the replacement covered the secret and moved its edges onto the bytes beside it. They now assert the whole string. One leg also records that an invalid byte is not one of the invisible separators, on the same ground as tab and newline: it decodes to U+FFFD and is drawn.
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ChangesControl-split credential redaction
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix · Severity of issue fixed: Medium Suggested reviewers: Merge Risk: 🟡 Moderate · up to A specially structured value can leave part of a split AWS credential visible. Fix the candidate selection while retaining the performance bound before merging. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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In `@internal/redaction/control_split.go`:
- Around line 101-102: Update splitSeparatorIndex so starts and ends are not
allocated with source-byte capacity; sort and deduplicate matched compact-text
endpoints, then scan value once to translate only those endpoints into original
byte offsets while preserving multibyte and invalid UTF-8 accuracy.
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I found issues that need to be addressed before this is ready. The change targets the approved redaction bug in #969, but the new matching path can miss credentials and adds substantial memory pressure on large output.
Merge readiness
- GitHub reports the PR as mergeable without conflicts against current
main(99721c7), which is also this PR's merge base. All reported CI, smoke, race, quality, security, and CodeQL checks pass. The merge state is BLOCKED with CodeRabbit's changes-requested review; its source-sized index concern is covered by the memory finding below.
Findings
-
[P1] Preserve credential boundaries while matching across invisible characters
internal/redaction/control_split.go:151-167(called frominternal/redaction/redaction.go:230)
Attribution: incomplete claimed fix and PR-worsened behavior. Issue #969 says, “The split form is redacted the same as the unsplit form.” The repository also requires secrets to be redacted from success and error output. At the merge base and livemain, two JWTs separated by NUL become[REDACTED]\x00[REDACTED]; this head emits[REDACTED].<second payload>.<second signature>. A split AWS key preceded byprefix\x00remains visible on this head even though its unsplit counterpart redacts, leaving the accepted issue incomplete for that input.
Root cause:compactSplitSeparatorsremoves every Cc/Cf character before matching, including delimiters outside a credential. Removing a delimiter before the split key destroys the regex's leading\b; removing one between credentials lets the first unbounded match consume the next JWT's header. The later contiguous passes cannot recover the missing split match or the exposed JWT suffix.
What fails:prefix\x00AKIAIOSF\x1bODNN7EXAMPLEsurvives verbatim and rejoins into the AWS key when the controls are hidden. With a NUL between tokens, JWT, GitHub, Anthropic, OpenAI, Slack, and Google shapes placed before a JWT expose its payload and signature; the JWT/JWT case also reproduces with ESC and Cf. The same boundary loss consumes unrelated prose aftersk-proj-abcdefghijklmnopqrstuvwxyz\x00ordinary, whereasmainpreserves\x00ordinary.
In this PR (close together):control_split.go's global compaction,shapeSecretSpansboundary decisions, and source-span replacement;redaction.go's new call;control_split_test.goneeds cases for a delimiter before a split key, neighboring JWTs after the supported unbounded shapes, and text immediately after a key. Existing tests cover a lone split key and two separated keys of other shapes, but none of these boundaries.
Unchanged on main: the supported regex shapes and their leading-boundary rule; the old split-key leak is the accepted issue, while the neighboring-JWT leak and prose loss are new on this head.
Required correction: make the new split-matching path distinguish invisible characters inside a credential from delimiters between credentials or ordinary text. Redact complete neighboring credentials independently and preserve original bytes outside each redaction. Retain the existing line-break and malformed-byte scope; do not change shared regex thresholds or unrelated callers.
Author fix: close this boundary rule across every listed in-diff code and test row in one pass. Do not patch only the AWS example or only the JWT example, and do not rebuild the existing redaction framework. -
[P2] Map matched endpoints without source-sized offset arrays
internal/redaction/control_split.go:100-115
Attribution: PR-introduced. The new call atredaction.go:230builds two[]intarrays with capacitylen(value)whenever the compacted text has any recognizable key, even if the separator is unrelated to that key. The merge base/live target allocate no such tables. The notification sink's contract says delivery “can never disrupt the run,” yetRedactStringaccepts unbounded notification text and verification stdout/stderr, and tool-result redaction runs before the output budget.
Root cause:splitSeparatorIndexindexes every source byte although the caller reads only the start and end of actual matches. On 64-bit Go the two arrays alone reserve at least 16 bytes per source byte. In a local 4 MiB probe, the split path allocated about 227 MiB versus 151 MiB for the comparable plain input; a 16 MiB base/head probe measured 544 MiB versus 832 MiB. Larger unbounded output can exhaust process memory before redaction/truncation completes. CodeRabbit's changes-requested inline comment identifies this same site.
In this PR (close together): index construction and endpoint lookup incontrol_split.go, plus a large-input allocation/scaling regression incontrol_split_test.gothat exercises a separator with a match. The existing small-string tests do not cover this cost.
Unchanged on main: caller output capture and output-budget policy; they are not the costly new arrays.
Required correction: translate only matched compact-text endpoints, or use another mapping whose memory scales with matches rather than source bytes. Preserve multibyte and malformed UTF-8 source offsets.
Author fix: close the allocation root cause in the new index path and pin it with a meaningful test; do not change unrelated callers or rebuild output budgeting.
…sible characters The split-credential pass compacted every Cc and Cf character out of the whole string before matching, which removed delimiters as well as filler. Two things followed. A whole credential written after a NUL lost the word boundary the shape matchers open with, so "prefix<NUL>AKIA...<ESC>..." stopped redacting even though the unsplit "prefix<NUL>AKIA..." has always redacted. And with the delimiter between two credentials gone, the unbounded JWT shapes ran out of the first key and through the header of the next, replacing both with one marker and exposing the second token's payload and signature. The same reach consumed ordinary prose written after a key. Three changes, one rule: a separator is filler inside a credential and a delimiter outside one, and the difference comes from the source rather than from the compacted copy. The pass now runs after the contiguous matchers instead of before them, over what they left, and never across a replacement. A whole credential is claimed by its own strict match, so neighbours stay separate and the delimiter between them survives. The shape matchers used here drop their leading word boundary, and the byte before the match's original start is what has to be a non-word byte, so a key after a NUL redacts and a key glued to the end of a word still does not. The offset table is gone with them. It carried a start and an end for every source byte, which is sixteen bytes per byte of input on a 64-bit build, and RedactString is handed whole command output and notification bodies with no bound in front of it. Only the endpoints of actual matches are resolved now, in one walk. On a 4 MiB input with a split key, the split path allocated 223.6 MB before this change and 154.9 MB after, against 146.3 MB for the same text with no separator in it. Tests cover a delimiter in front of a split key against its unsplit verdict at every kind of leading byte, each supported shape placed in front of a JWT with each class of separator, text immediately behind a key, a caller-supplied replacement made of word characters, and the allocation ceiling.
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Inline comments:
In `@internal/redaction/control_split.go`:
- Around line 282-297: Update redactSplitRegion’s scan to check boundaries
before accepting each match; when a match fails, resume at start+1, using
recorded removed-separator offsets so matches beginning at a removed separator
pass the boundary check. Apply the OpenAI filter to each accepted match and
remove the post-mapping wordByte filter. Add regression tests for both split and
unsplit inputs.
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Both right, and the boundary one I had reasoned my way into on purpose, which made it worse. I had decided A NUL in front of a key is already a boundary today. So removing it must not turn the key into the tail of the word in front of it, and my compaction did exactly that. Both of the regressions you name reproduce too, including the prose loss. What changedThree things, one rule: a separator is filler inside a credential and a delimiter outside one, and the difference comes from the source rather than from the compacted copy. Order. The split pass now runs after the contiguous matchers instead of before them, over what they left. A whole credential is claimed by its own strict match, so two of them with a separator between stay two replacements with the separator still between, and nothing reaches out of the first and into the second. It also stops at every replacement already on the page, because a caller can supply one spelled out of word characters, and then the marker itself would read as the middle of a key. Leading boundary. The shape matchers used on the compacted text drop their leading The index is gone. Only the endpoints of actual matches are resolved now, in one walk over the source, so the memory is two ints per match endpoint rather than two per source byte. MeasuredSame probe on main, on 5dbf5e4, and on this head. Every row is
Bytes allocated by one call, smallest of three, against the same text with no separator in it:
So the overhead over the plain path goes from about 18 times the input to about 2, which is the compaction copy this path actually makes. TestsFive new ones in
Falsification, six mutations, each detected by the test that claims the behavior: the source boundary check dropped, the split pass moved back in front of the contiguous matchers, the trailing split pass removed, the split matchers keeping their Scope unchanged: tab, newline and carriage return are still not separators, malformed bytes are still measured as the one byte they occupy, and no shared threshold or other caller moved. gofmt, |
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I found issues that need to be addressed before this is ready.
Merge readiness
GitHub reports this head mergeable without conflicts against current main (99721c7), which is also the merge base. All reported CI, smoke, race, quality, security, and CodeQL checks pass. The merge state is BLOCKED by changes-requested reviews. The earlier #978 and #1013 efforts on issue #969 were closed without merge; #945 is a separate open redaction-performance PR, not a current-main replacement for this fix.
Findings
🟠 P1 — Retry split-key matching after a rejected earlier candidate
📍 Where: internal/redaction/control_split.go:155-166,282-297; called from internal/redaction/redaction.go:241.
💥 What fails: RedactString("xAKIA\x00AKIAIOSFODNN7E\x01XAMPLE", Options{}) returns the input unchanged. The AWS key after the NUL becomes readable when invisible bytes are removed; the same key without the internal \x01 redacts. OpenAI and GitHub-shaped earlier candidates can shadow later split keys the same way.
🔎 Root cause: FindAllStringIndex selects non-overlapping relaxed matches before the original-source leading boundary and OpenAI false-positive filter are checked. When an earlier match is rejected, it has already consumed the start of a later valid key. The scan never retries inside that rejected span.
📜 Stated contract:
Issue #969: “The split form is redacted the same as the unsplit form.”
🏷️ Attribution: Incomplete claimed fix. This exact split input leaks on merge base and live main as well as on this head; its unsplit counterpart redacts on all three. The PR adds a split-matching path to fix that accepted behavior but leaves this boundary case unhandled. The current-head CodeRabbit inline request identifies the same path.
📌 In this PR:
control_split.gorelaxed shape selection and source-boundary/filter acceptance — rejected matches can hide later split matches.redaction.gonew call into that path — exposes the incomplete result to every existingRedactStringcaller.control_split_test.go— leading-boundary cases test one key but omit a rejected earlier candidate followed by a valid split key. Cover both boundary and OpenAI-filter rejection.
🔒 Unchanged on main: The existing strict regexes, thresholds, and callers; none need a rewrite.
🔧 Required correction: Make the new scan reconsider later candidate starts after a boundary or filter rejection, using the source boundary for each accepted span. Preserve the existing filters and byte mapping.
🛠️ Author fix: Close the rejected-match rule across the changed matcher, call, and tests. Do not patch only the AWS example; cover the same failure after another rejected shape. Keep the strict patterns and unrelated callers intact.
🚫 Out of scope: Adding credential formats or changing line-break and malformed-byte scope.
🟠 P1 — Keep two split JWTs from consuming each other
📍 Where: internal/redaction/control_split.go:99-109,155-166,282-297; exercised through internal/redaction/redaction.go:241.
💥 What fails: Two individually split JWTs separated by NUL produce one [REDACTED] marker followed by the second JWT's payload and signature. The new neighboring-key test covers a whole JWT next to another whole key, but neither strict matcher can claim a JWT that is itself split.
🔎 Root cause: Compaction removes the delimiter between the two split tokens. The first greedy JWT match then takes the second token's header as part of its own suffix. Splicing that one span leaves the second token's remaining segments in output.
📜 Stated contract:
Issue #969: “The split form is redacted the same as the unsplit form.”
The new regression test says, “A MATCH MUST NOT REACH OUT OF ONE CREDENTIAL AND INTO THE NEXT.”
🏷️ Attribution: Incomplete claimed fix. Both split JWTs remain visible on the merge base and live target; this head redacts part of their combined text but leaves the second token's material. The PR's strict-first ordering fixes whole neighbors, not two split neighbors.
📌 In this PR:
control_split.gocompaction, shape selection, and source-span splicing — a source delimiter between two split JWTs is lost.redaction.gonew split pass — returns the exposed second segments to existing callers.control_split_test.goneighboring-credential test — extend it to two split JWTs and assert independent complete replacements.
🔒 Unchanged on main: Existing JWT shape definitions and ordinary strict matching.
🔧 Required correction: Select and replace complete, independent source spans for both split JWTs while retaining their outside delimiter. Keep the already-covered whole-neighbor behavior.
🛠️ Author fix: Close the source-delimiter rule across the changed matching and test rows in one pass. Do not patch only the first token's span or rebuild the shared regex framework.
🚫 Out of scope: New JWT formats or unrelated token parsing.
…he original text CodeRabbit found a bypass in the compaction approach: "xAKIA<NUL>AKIAIOSF<SOH>ODNN7EXAMPLE" leaked while its unsplit counterpart redacts. With the separators removed first, the leftmost AWS match began at the decoy AKIA, was then rejected for the "x" in front of it, and had already consumed the start of the real key, so the real key was never considered. The ordinary-prose version is any word ending in "sk" followed by a hyphen, "ask-" or "task-", ahead of a split OpenAI key. Resuming the scan one byte after each rejection would close that but is quadratic for the greedy shapes on text like "ask-ask-ask-..." with one NUL in it. So the boundary goes back inside the pattern instead. Each shape is rewritten through regexp/syntax so a run of separators may sit between any two characters it consumes, but never before the first, and matched against the ORIGINAL text with its leading \b intact. RE2 then judges the word boundary against the real neighbour in one linear pass, and there is no compaction and no offset mapping. The separator class is generated from the same Unicode tables as splitSecretSeparator. Two further cases came out of rerunning the seeded differential against main: - The shapes are matched independently and the union of their spans replaced. Applied one after another, a split key's unbounded body ran on across a separator into a following JWT, stopped at its first dot, and left the JWT shape nothing to match, exposing its payload and signature. - A second pass, ungated, catches a credential glued onto a split one, which gains its word boundary only once the first is replaced. It is often whole itself, so its region can hold no separator by then. On 6,000 control-free inputs the output is byte-for-byte main's. On 6,000 with invisible characters, 147 outputs still hold a known credential once those are removed, against 2112 on main; 140 of the 147 leak on main too when the input is unsplit, and the remaining 7 are the one limit now written into the header comment: a split key whose first fragment is a complete credential on its own, with another credential glued onto its tail.
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On the "retry the split scan after a rejected leading boundary" thread: it's a real bypass, and the fix I've pushed is not the one suggested, for a reason worth spelling out. Reproduced, plus an ordinary-prose version of it: Any word ending in "sk" followed by a hyphen (ask-, task-, disk-) in front of a split OpenAI key shadowed it the same way. Resuming at What's there now, at 3d6f899, removes the compaction step entirely. Each shape is rewritten through Rerunning the seeded differential against
On 6,000 control-free inputs the output is byte-for-byte Eight mutations, each caught by the test for it: no gaps, no leading The cost, measured against It's linear everywhere, including on the inputs that would make a retry quadratic. The doubling in the first row is the second pass rescanning the whole text once the first has changed something. Anchoring that pass at the new replacements would take it close to one pass. I left it out to keep this change reviewable, but I'm happy to add it if it's worth it to you. |
Matches of one pattern never overlap, so when a split credential's body ran on through the separator after it, a following credential of the same shape could not start a match of its own. A JWT body stops at the next token's first dot and a classic GitHub body at its underscore, so two split JWTs side by side left the second one's payload and signature in the clear. A match the OpenAI filter rejects spans what it ran into as well, so a split key after kebab-case prose was rejected with the prose and printed. When a match runs through a separator run into a position where the same shape matches again and reaches at least as far, that credential is taken on its own, and the first is cut at the separators when it is a complete match by itself. Each piece is filtered on its own. Candidates are tried latest first and only where the shape's literal prefix follows the separators, at most eight per match, so the pass stays linear. The header comment now says plainly that the rest of a key whose front part is complete alone stays visible, and drops a stale sentence from before the shapes were matched independently.
…t too The run-on search looked for a shape's literal prefix contiguously after the separators, so a token split inside its first few characters was never seen as a new start and its payload leaked again. The prefix is now matched with gaps allowed between its characters, the way the shapes are. The new test splits the second token's header at every character, which also pins that the bounded search is spent only where a credential can begin.
Following a run-on from the second credential into a third, and on to the end of the chain, did that walk again from every match inside the chain, which is quadratic: a megabyte of split JWTs back to back allocated about seventeen gigabytes and ran for ten minutes. Each match now separates only the credential it ran into. The scan's own next match starts inside that credential and takes the following step, so a chain is still covered, and in chains of three or more the markers after the first pair can join. A test bounds the allocation on a chain of split JWTs; the linear pass uses about forty times the input and the walk used far more.
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Inline comments:
In `@internal/redaction/control_split.go`:
- Around line 220-349: Update `leadingLiteral` to derive the common literal
prefix across alternation branches, including through capture and concatenation
nodes, so the AWS `AKIA|ASIA` shape yields `A`. Keep `maxRunOnCandidates`
bounded; ensure unrelated separator runs do not consume the candidate limit
before a later split AWS credential is found.
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@jatmn both of your reviews are on older heads ( 22 Sep, P1, boundaries across invisible characters. Fixed by the redesign at 22 Sep, P2, source-sized offset arrays. Gone with the compaction; nothing is indexed per byte now. 23 Sep, P1, a rejected earlier candidate. Fixed at 23 Sep, P1, two split JWTs. This one was still open on Two more cases have the same root cause, and both are covered now. A classic GitHub body stops at the next token's underscore the way a JWT stops at a dot, so a second split I got two things wrong on the way; both were caught before this push. The first version looked for the next token's prefix contiguously, so a token split inside its first three characters slipped past. The test that splits the second header at every character pins that. It also followed a chain of split JWTs to the end from every match inside the chain, which is quadratic: a megabyte of them took ten minutes and about 17 GB. Each match now takes one step, and the scan's next match takes the one after. An allocation bound on a chain would catch that version (it fails in 8s), and 1 MiB against 2 MiB of chain doubles in time and memory. On the seeded differential, whole credentials still visible once the invisible characters are dropped go from 2112 on One decision for you, if you want it changed. The header's limit is bigger than my earlier wording made it sound. When the part of a split key before the separator is complete on its own, the strict pass replaces it and the rest of the key stays visible. It's a fragment, never the whole key, but it isn't rare. Counting "any 16 or more characters of a credential still visible", the corpus has 468 such outputs here against 2333 on |
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The split-redaction pass is done carefully: the invisible-character class is generated from the same Unicode tables as the predicate so gate and class cannot drift, tab/newline/CR are deliberately excluded as visible structure (documented), matching runs on the ORIGINAL text so the reassembler trap is avoided, and the cheap gate only skips the new pass while the contiguous matchers always run. The differential evidence (147 residual vs 2112 on main across 6,000 inputs) and the documented seven-shape residue are exactly the honest framing this kind of change needs.
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Fixes #969
The problem
Every credential-shape matcher in
RedactStringdescribes a contiguous run of body characters, and none of their classes admits a control or format character. One invisible character inside a key ends the match, and both fragments are emitted untouched. Whoever reads that output next sees the key back, because nothing about those characters was ever displayed: a terminal eats the escape, a log viewer or JSON consumer strips the control byte, a copy-paste drops both.On
main, taking the reported case plus every neighbour of it, inserting the character into the body and then dropping it again:So the report names two bytes and the behaviour belongs to two whole character classes, Cc and Cf. This is written against the classes.
The fix
Each shape matcher is rewritten through
regexp/syntaxso a run of separators may sit between any two characters it consumes, though never before the first or after the last, and matched against the ORIGINAL text with its leading\buntouched. RE2 then judges the word boundary against the real neighbour in one linear pass. So a key written after a NUL starts at a boundary, just as the unsplit key does, and a key glued onto a word does not. The separator class is generated from the same Unicode tables assplitSecretSeparator, and a test walks every code point to keep them identical.Four rules keep the neighbours right:
An earlier version of this PR removed the separators and matched the compacted copy. That lost the difference between a separator inside a credential and one beside it. Checking the boundary afterwards left a bypass that CodeRabbit found: in
xAKIA<NUL>AKIAIOSF<SOH>ODNN7EXAMPLEthe leftmost compacted match began at the decoy, was rejected, and had already consumed the start of the real key. The prose version is any word ending in "sk" followed by a hyphen ahead of a split OpenAI key. Resuming the scan after each rejection would have been quadratic onask-ask-ask-..., which is why the boundary now lives inside the pattern.What is deliberately not covered
Tab, newline and carriage return are not separators, and
TestLineStructureIsNotTreatedAsAnInvisibleSeparatorfails if that changes, so it has to be a decision rather than a drift. They are real text structure: a credential broken across a line is visible to whoever reads it rather than hidden from them, and treating them as gaps would let one match span a line break and replace unrelated lines. An invalid UTF-8 byte is out for the same reason, since the engine reads it as U+FFFD and it is drawn.One known limit comes from running the contiguous matchers first. When the part of a split key before its first separator is already a complete credential by itself, the contiguous matcher replaces that part and stops at the separator, and the rest of the key stays visible: a fragment of the key, never the whole of it. A credential glued straight onto that rest is left too, where the unsplit key would have swallowed it. Nothing at the character level tells the rest of a key from a word written after a whole one, so carrying the match across the separator would eat that word again (
sk-proj-…<NUL>ordinary), which is exactly what running first prevents. The numbers below say how often this happens.Key-based redaction (
apiKey: …,Authorization: …, query parameters) already replaces the whole value and was never affected.Measured
A seeded differential against
main, 6,000 inputs each way:Control-free text: output is byte-for-byte
main's.With invisible characters mixed in: outputs that still contain a whole known credential, or a JWT's payload or signature, once those are dropped:
139 of the 146 leak the same way when the input is unsplit (a key glued to a word, which the contiguous matchers have never redacted). The other 7 are the limit above.
Counted by any visible run of 16 or more characters of a credential instead, it is 2333 on
mainand 468 here. 218 of the 468 show one on the unsplit input too. The other 250 are the rest of a key whose front part was complete alone: the same limit, measured by what stays visible rather than by whole keys.Cost, one
RedactStringcall.maindoes no split work at all on the last four inputs, which is why its output there is its input:Text with no invisible character takes exactly the path it took before, decided by a byte scan that allocates nothing. Everything is linear, including the inputs that would make a scan-and-retry or a chain walk quadratic; the two chain rows double with the input. The doubling in the first row comes from the second pass rescanning the whole text once the first has changed something.
Verification
go build ./...,go vet ./...,gofmt,go test -race ./internal/redaction/,go run ./cmd/zero-release buildandsmokeon windows/amd64.Twenty mutations, each requiring a named test to fail, all caught at fb6a1b8:
\b, a gap allowed before the first character, sequential instead of union, no second pass, a gated second pass, replacements no longer barriers, and the kebab-case filter dropped on this path.go test ./...is 85 packages clean with two failures,internal/configTestResolveReportsExplicitMaxTurnsandinternal/tuiTestAltScreenTranscriptScrollKeepsFooterFixed. Both fail the same way on unmodifiedmain, both are what #1072 fixes, and neither touches redaction.Summary by CodeRabbit
Bug Fixes
Tests