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Fix/redaction literal leaks - #61
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Redact honored only the doubled-quote ('') escape, so a literal containing
\' — the default escape in MySQL and in Postgres E'...' strings — closed at
the wrong quote. The lexer then desynchronised and emitted the *following*
literal's contents as query structure:
SELECT * FROM u WHERE a = E'it\'s' AND token = 'sk-live-abcdef'
-> SELECT * FROM u WHERE a = E?s?sk-live-abcdef?
That breaks the SECURITY.md invariant that no Result carries a raw literal
out of the process, and it applied to Result.Fingerprint too, so leaked
values could land in a metrics label.
Dialects genuinely disagree about whether a backslash escapes a quote, and
neither reading dominates: picking either one can desync on input written
for the other. Redact now scans under both readings and redacts the union
of the literal ranges, so no reading can leave a literal byte in the
output. Ambiguous SQL is over-redacted (structure lost, values not);
unambiguous SQL is byte-identical to before, and a query with no backslash
skips the second scan entirely.
Also redacted, both previously untouched:
- Postgres dollar-quoted strings ($$body$$, $tag$body$tag$), which passed
through completely. $1/$2 placeholders and unterminated $...$ runs are
still left alone.
- Hex/binary literals: 0x4142 redacted only its leading 0 and copied the
payload out as an identifier.
IsMultiStatement, which guards explain against stacked statements, keeps
the narrowest reading deliberately — the opposite fail-safe direction. It
must never miss a separator, so 'a\'; DROP TABLE t; --' stays refused
rather than reading as one literal. Pinned by tests.
PrepareQuery now redacts once rather than twice (the fingerprint is folded
from the already-redacted text), which offsets most of the two-pass cost.
Adds a fuzz target over the lexer's index arithmetic and benchmarks for
Redact/Fingerprint.
The dollar-quote support added in the previous commit taught redactSpans
about $tag$...$tag$ but not stripComments, which Redact runs first. A -- or
/* inside a dollar-quoted body was therefore stripped as a comment, taking
the body's closing delimiter with it; scanDollarQuoted then found no
terminator, gave up, and the body was copied out as query structure:
SELECT * FROM t WHERE a = $$SECRET -- x$$ AND b = 1
-> SELECT * FROM t WHERE a = $$SECRET
That is the same leak class the previous commit set out to close, and the
two commonest dollar-quote payloads — Postgres function bodies and free-text
notes — routinely contain "--".
The same disagreement also let a trailing comment survive when a dollar body
held an odd number of single quotes (SELECT $$a'b$$ -- alice@example.com):
stripComments desynced on the quote and copied the comment through, and the
new dollar span then consumed the body that used to swallow it. Comments are
a documented PII carrier, so that was a regression against main.
stripComments now treats a dollar-quoted run as opaque, which fixes both.
Regression tests cover a line comment, a block comment and a tagged body,
plus the two directions that must not change: real comments around a dollar
body are still stripped, and dollar signs inside a comment still do not open
a quote. Fuzz seeds extended to the same shapes.
Also documents a consequence of the two-reading union that was only framed
as a readability cost: over-redaction changes the fingerprint, so a query
whose values only sometimes contain a backslash groups under two
fingerprints, splitting N+1 counts and dedup across both.
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This repository does not receive automatic reviews because it has fewer than 10 stars. ⚙️ Run configurationConfiguration used: Repository: KARTIKrocks/sqlguard/.coderabbit.yaml Review profile: ASSERTIVE Plan: Advanced Run ID: WalkthroughThe analyzer expands SQL literal redaction to cover ambiguous backslash escapes, dollar-quoted strings, and radix numbers. Comment stripping preserves dollar-quoted bodies. ChangesSQL literal redaction
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant PrepareQuery as Analyzer.PrepareQuery
participant Redact
participant stripComments
participant redactSpans
participant foldRedacted
PrepareQuery->>Redact: raw SQL
Redact->>stripComments: SQL for comment stripping
stripComments-->>Redact: SQL with dollar-quoted bodies preserved
Redact->>redactSpans: comment-stripped SQL
redactSpans-->>Redact: literal and identifier spans
Redact-->>PrepareQuery: redacted SQL
PrepareQuery->>foldRedacted: redacted SQL
foldRedacted-->>PrepareQuery: fingerprint
Merge Risk: 🔵 Low · up to This change closes real literal leaks, but the new dollar-quote handling still copies the body of an unterminated 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 68.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 25 functions across 6 files. (3 skipped: 3 unsupported.) ✨ Finishing Touches 💡 1📝 Generate docstrings 💡
🧪 Generate unit tests (beta)
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Actionable comments posted: 4
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Inline comments:
In `@analyzer/redact.go`:
- Around line 219-220: Update scanDollarQuoted to reject an opening dollar-quote
delimiter when the preceding byte is an identifier character, using the existing
identifier-byte rules; this keeps dollar signs within identifiers such as
foo$tag$value$tag$ from being treated as literals by either caller.
- Around line 170-172: Update literalSpans to redact double-quoted runs
conservatively, since they may be string literals in MySQL default mode;
document that this also redacts double-quoted identifiers. Keep backtick-quoted
runs preserved as identifiers.
- Around line 231-234: Update scanDollarQuoted to reject an opening delimiter
preceded by an identifier byte using isIdentByte, then treat an unterminated
otherwise-valid dollar quote as extending to the end of the input. Preserve the
existing rejection of digit-starting tags so bind placeholders such as $1 remain
unchanged.
In `@website/docs/redaction.md`:
- Line 22: Update the redaction documentation entries marked “Changed in 0.3”
for single-quoted backslash escapes and radix literals to state their prior
behavior: escapes could expose subsequent literals, and radix literals retained
their payloads.
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CHANGELOG.mdanalyzer/analyzer.goanalyzer/fallback.goanalyzer/redact.goanalyzer/redact_bench_test.goanalyzer/redact_fuzz_test.goanalyzer/redact_test.gowebsite/docs/explain.mdwebsite/docs/redaction.md
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Three defects in the dollar-quote support, two of them leaks: Non-ASCII tags were unrecognised. Postgres tags follow unquoted-identifier rules, which admit non-ASCII letters, but the tag scan accepted ASCII only — so $é$secret$é$ matched neither delimiter, no redaction span was produced, and the body reached Result.Query and Result.Fingerprint in the clear. isIdentByte now accepts bytes >= 0x80. An unterminated but well-formed delimiter was ignored rather than redacted. On a truncated or malformed query the remainder is literal body, so it now runs to the end of the input. The previous reasoning — that an unterminated $...$ is more likely two stray dollar signs — is better served by the next change, which rejects those up front. A "$" that continues an identifier opened a literal. Postgres allows "$" inside an identifier after its first character, so foo$tag$v$tag$ is one name; it was being redacted to "foo?". The delimiter is now rejected when the preceding byte is an identifier byte. Also fixes a false rejection introduced when stripComments learned about dollar quotes: it copies a body verbatim (a comment marker inside one is data), but blankStringLiterals did not blank it, so a ";" in a body made IsMultiStatement refuse a single statement — explain rejected SELECT $$-- ; note$$ as though it were stacked. blankStringLiterals now blanks dollar bodies while keeping the narrow backslash reading the separator check depends on. Docs: the version markers on the redaction bullets moved into a paragraph that opens with the marker and states the prior behaviour, per the convention in AGENTS.md.
Teaching blankStringLiterals about Postgres dollar quotes (previous commit)
broke the invariant IsMultiStatement is built on. That check guards explain
against stacked statements on every dialect, but MySQL reads "$$" as
ordinary identifier bytes, so applying Postgres semantics blanked a real
MySQL separator out of existence:
IsMultiStatement("UPDATE t AS $$ SET id = 1; DROP TABLE t") == false
explain.validate then accepted it and handed the original SQL, semicolon
intact, to the EXPLAIN concatenation. With --allow-dml the statement
classifies as DML, so analyzeMySQL opens a read-write transaction; on a
connection with multiStatements enabled the trailing DROP TABLE would run,
and MySQL implicit-commits DDL, so the deferred rollback would not undo it.
blankStringLiterals no longer knows about dollar quotes, and its doc comment
now says why it must not learn. stripComments keeps its dollar handling:
that one only ever removes less, so it can only make the separator check
stricter, and Redact needs it to find the end of a dollar-quoted body.
The cost is the false rejection this reverts: a Postgres query with a ";"
inside a dollar-quoted body is refused by explain. Hiding a separator is the
one error the check cannot afford, so that trade is deliberate, and the
tests that pinned the old behaviour now pin the refusal instead.
Adds the two payloads to explain's own validate table, where the
consequence actually lands.
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The previous commit made stripComments dollar-aware but left
blankStringLiterals dialect-agnostic, and that asymmetry opened the mirror
image of the bypass it closed. stripComments copies a dollar body verbatim,
so a quote inside one survived into blankStringLiterals, which read it as
an ordinary literal and blanked everything after it — separator included:
IsMultiStatement("SELECT $$'$$; DROP TABLE t") == false
Neither reading of "$$" is safe on its own. Read as Postgres, that input
hides its ";" behind an unterminated ordinary literal. Read as anything
else, "UPDATE t AS $$ SET id = 1; DROP TABLE t" hides its ";" behind an
unterminated dollar body. IsMultiStatement now blanks under both readings
and refuses if a ";" sits outside a literal in either, so no single dialect
assumption can hide a separator. Backslash escapes stay unhonored.
blankStringLiterals goes back to blanking dollar bodies, which also fixes a
false negative the same asymmetry caused: a keyword in a dollar-quoted value
reached the clause regexes, so "WHERE note = $$LIMIT 1$$" read as having a
LIMIT clause and suppressed select-without-limit.
The false rejection stands and is now the only cost: a single statement
carrying a ";" inside a dollar-quoted body is refused. Over-rejection is
affordable here; a hidden separator is not.
The Security section had grown to ~90 lines of commit-message material: root-cause narrative, a before/after code block, benchmark numbers, test file paths, and unexported internals (stripComments, blankStringLiterals) that no consumer can see. None of that belongs in a changelog, and all of it already lives in the commits and the PR. Rewritten as four entries in the file's existing style — bold user-visible lead, a few lines each, no code blocks. Keeps every fact a user can act on: what was exposed and that logs may need auditing, that fingerprints change and split N+1 grouping, that explain now refuses more input, and the remaining double-quote gap on MySQL. Net 79 lines removed.
…comments
The doc comment on IsMultiStatement, and the matching passage in
website/docs/explain.md, attributed each hidden separator to the wrong
reading. Verified against the code:
SELECT $$'$$; DROP TABLE t dollar reading sees ";", ordinary hides
UPDATE t AS $$ SET id = 1; DROP .. ordinary reading sees ";", dollar hides
Both were stated backwards, and the MySQL one was a non-sequitur: it said
MySQL reads "$$" as identifier bytes and therefore hides the separator
behind a dollar body, but under that reading there is no dollar body. The
code was right; only the explanation was inverted. Since the explanation is
what stops someone dropping a reading later, it is now keyed on the reading
rather than on a dialect label, and pinned by a test that asserts exactly
one reading catches each payload.
explain.md also gains the _Changed in 0.3._ marker and a line on the prior
behaviour, per AGENTS.md.
Comment cleanup in redact.go: removed archaeology about the strings.Contains
check that no longer exists, an inline comment duplicating the doc comment
above it, and editorialising ("the classic PII carrier"). Tightened the
Redact, Fingerprint, foldRedacted and redactSpans docs without dropping any
load-bearing rationale. 34% comment lines, in line with analyzer.go's 33%.
2 of 13 tasks
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…ariant AGENTS.md said both Redact and IsMultiStatement scan under multiple readings of both the backslash and the "$$" question. They do not: literalSpans calls scanDollarQuoted unconditionally, so both of Redact's passes recognise dollar quotes and differ only on backslash escapes, while blankLiterals' flag is dollarQuotes and IsMultiStatement never honors backslash escapes at all. Each function scans twice over a *different* axis. The text now says which, and why Redact needs no second "$$" reading: honoring one can only add a redact span, so that ambiguity has no leak direction. The bot configs had a scope blind spot that matches where the bugs actually landed. Both .greptile/config.json and .coderabbit.yaml protect the multi-statement guard under explain/**, but IsMultiStatement lives in analyzer/redact.go and its blanker in analyzer/fallback.go — all three bypasses in PR #61 were edits to analyzer/, outside the scope of the rule meant to catch them. Added a dual-reading-lexer rule scoped to those two files, extended the coderabbit analyzer/** instructions to match, and wrote the three bugs up as a worked example in .greptile/rules.md, which exists for exactly that. Worth noting both bot configs already documented BeginTx(ReadOnly: !dml) correctly — AGENTS.md was the only file that had it wrong, which the previous commit fixed.
This was referenced Sep 24, 2026
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Summary
analyzer.Redactwas leaking literal values intoResult.QueryandResult.Fingerprint— the invariantSECURITY.mdnames explicitly: "A path that leaks literals to a reporter/log is a security bug."Three distinct leaks, each verified before and after:
a = E'it\'s' AND token = 'sk-live-abcdef'a = E?s?sk-live-abcdef?a = E?bio = $$super secret value$$bio = ?bio = $é$secret$é$bio = ?x = 0x4142414241424142x = ?x4142414241424142x = ?The backslash case is the worst of them: it does not truncate, it desynchronises the lexer, which then emits the following literal verbatim as query structure.
Why both readings are scanned
Dialects genuinely disagree about whether
\'closes a literal — MySQL's defaultsql_modeand PostgresE'…'say yes, Postgres withstandard_conforming_stringssays no. Neither reading dominates; each leaks on input written for the other. SoRedactscans under both and redacts the union of the literal spans. Ambiguous SQL is over-redacted (structure lost, values not); unambiguous SQL is byte-identical to before, and a query with no backslash skips the second scan entirely.The separator check goes the opposite way, deliberately
IsMultiStatement(explain's stacked-statement guard) keeps the narrowest reading and stays dialect-agnostic. The two have opposite fail-safe directions — redaction must never leave a literal byte in its output, the separator check must never miss a;.This bit twice in review. Teaching
blankStringLiteralsabout dollar quotes (to fix a false rejection) blanked a real MySQL separator out of existence:UPDATE t AS $$ SET id = 1; DROP TABLE tpassed the check and reachedEXPLAINwith its;intact, inside the read-write transaction--allow-dmluses, where DDL implicit-commits past the rollback. Fixed in 7ddc9b8 and pinned inexplain's own validate table.Type of change
Checklist
make cipasses (fmt-check, vet, lint, vuln, test-race, lint-docs) across all moduleswebsite/docs/with a version marker for anything newAGENTS.md/.sqlguard.example.yml— n/a, no convention or config key changed## [Unreleased]inCHANGELOG.mdanalyzer/middleware/reporterNotes for reviewers
Three trade-offs taken knowingly, all documented in the code and on the docs site.
Over-redaction changes the fingerprint. A query whose values only sometimes contain a backslash groups under two fingerprints, which splits N+1 counts and dedup across both. Bind parameters avoid it; called out in
website/docs/redaction.md.A
;inside a dollar-quoted body is refused byexplain. A Postgres-only false rejection, and the deliberate cost of the separator fix above — hiding a separator is the one error that check cannot afford.Double-quoted runs stay identifiers. A real gap on MySQL's default
sql_mode, pre-existing and pinned by tests the project wrote on purpose. Redacting them would blank every quoted identifier in ORM-generated Postgres SQL, turningSELECT "id", "email" FROM "users"intoSELECT ?, ? FROM ?. The honest fix is a dialect hint on theAnalyzer, which is a public API decision and out of scope for a security patch. Tracked in #62.Performance.
PrepareQuerynow redacts once instead of twice, offsetting most of the two-pass cost.Redactis ~690 ns parameterized (2 allocs, unchanged) and ~1.3 µs literal-heavy (3 allocs, +1) against a ~70 µsAnalyze— roughly 2% of that path. Benchmarks inanalyzer/redact_bench_test.go.Testing.
TestRedactNoLeakAcrossDialectAmbiguityasserts no secret byte survivesRedactorFingerprintacross 15 leak shapes.TestIsMultiStatementpins the separator cases that must stay refused, including the MySQL$$payloads, andexplain's validate table covers the same payloads where the consequence lands.FuzzRedactran ~12M execs clean over the lexer's index arithmetic and span postconditions.