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Escape cask metadata in Homebrew Fleet-maintained-app script generation - #51324
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Cask metadata from the Homebrew ingester was interpolated into root-privileged generated install/uninstall scripts through double-quoted and unquoted-heredoc sinks, where shell command substitution survives. Escape every cask-controlled value at its sink: a new shellDoubleQuoteEscape for double-quoted $VAR contexts (keeps output byte-identical for legitimate casks, so the auto-update script comparison is unaffected), shellSingleQuote for the uninstall script directive, and printf with a single-quoted argument for the pkg choice XML (a heredoc, even with a quoted delimiter, remained injectable via a newline in the metadata). Adds regression tests asserting metacharacter payloads appear literally in the generated scripts. Resolves fleetdm/confidential#17171 (GHSA-fv3p-h7wv-2jgm).
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #51324 +/- ##
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+ Coverage 68.77% 68.82% +0.04%
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Files 4001 4008 +7
Lines 258512 260007 +1495
Branches 13863 13863
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+ Hits 177788 178943 +1155
- Misses 64925 65200 +275
- Partials 15799 15864 +65
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Pull request overview
This PR hardens the Homebrew maintained-apps ingester’s generated macOS install/uninstall shell scripts by ensuring cask-controlled metadata cannot be interpreted as shell code (notably command substitution) when interpolated into root-privileged script sinks.
Changes:
- Add
shellDoubleQuoteEscapefor safe interpolation into existing double-quoted shell strings, and apply it to app paths, pkg filenames, and symlink paths. - Quote uninstall
scriptdirectives withshellSingleQuoteto prevent apostrophe-based quote breakouts. - Replace choice-XML heredoc emission with a single-quoted
printfwrite to prevent shell expansion and delimiter-smuggling.
Reviewed changes
Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| ee/maintained-apps/ingesters/homebrew/scripts.go | Escapes/quotes cask-controlled metadata at all relevant script interpolation sinks (double-quoted contexts, uninstall script directive, and pkg choices XML emission). |
| ee/maintained-apps/ingesters/homebrew/scripts_test.go | Adds regression tests covering metacharacter payloads and a unit test for shellDoubleQuoteEscape. |
| changes/17171-homebrew-ingester-shell-escaping | Changelog entry (content excluded from review by policy). |
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| // dqEscaper backslash-escapes the only four characters that keep a special | ||
| // meaning inside a double-quoted shell string: backslash, dollar, backtick, and | ||
| // double quote. Backslash is listed first so an escape we introduce isn't | ||
| // re-escaped (strings.Replacer scans left to right in a single pass and never | ||
| // reconsiders inserted text). |
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Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review. WalkthroughHomebrew-generated macOS install and uninstall scripts now escape cask-controlled paths, package values, script directives, choice XML, and symlink arguments. Choice XML uses heredocs only for inert content and single-quoted 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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Inline comments:
In `@ee/maintained-apps/ingesters/homebrew/scripts.go`:
- Around line 483-484: Update the mkdir command generated in the pathsCreated
check to include the option terminator before the escaped pathname, and add a
regression test using a target whose parent directory begins with a hyphen to
verify it is treated as a directory rather than an option.
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changes/17171-homebrew-ingester-shell-escapingee/maintained-apps/ingesters/homebrew/scripts.goee/maintained-apps/ingesters/homebrew/scripts_test.go
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| require.Equal(t, `a\\b`, shellDoubleQuoteEscape(`a\b`)) | ||
| require.Equal(t, "a\\`id\\`b", shellDoubleQuoteEscape("a`id`b")) | ||
| // Backslash is escaped first, so an already-escaped dollar isn't doubled. | ||
| require.Equal(t, `\$`, shellDoubleQuoteEscape("$")) |
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It doesn't look like this is testing what the comment actually says, shouldn't the input be something like "$foo"?
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Could there be any issues with Fleet keeping old install scripts because they changed? #50097 I think even with the fix for that issue, it could still happen if any script actually changes. |
- Keep the historical unquoted mkdir and heredoc choice-XML forms when the metadata is inert (every real cask), emitting hardened forms only for metadata that needs them, so stored scripts don't churn and the FMA auto-update job doesn't mistake the rewrite for an admin customization. - Preserve a leading $APPDIR in symlink source/target while escaping the rest; unconditional escaping would have broken every binary-artifact app. - Add -- to the hardened mkdir so a leading dash can't be parsed as an option. - Fix the misleading dqEscaper ordering comment and the redundant TestShellDoubleQuoteEscape case it was echoed in. - Verified zero churn by regenerating zed, cursor, docker-desktop, surge, virtualbox, and microsoft-word outputs: script refs byte-identical apart from upstream version bumps.
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This will regen roughly 40 scripts. Any customer on 4.90.1 will be fixed, and going forward script updates will flow through to customer instances. Any customers on previous versions will still be impacted but I don't think there is a way to address that. |
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@allenhouchins I think we need to reconsider how we check if an admin edited a script on their Fleet instance so that we don't have to compare scripts on every FMA update. I'm currently filing a bug report for some FMAs that might still break with future version updates, so I will try to bring that up there. |
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- app.UniqueIdentifier goes raw into a single-quoted shell literal at 4 call sites in installScriptForApp (quit_and_track_application/relaunch_application), unlike every other field in this file, which goes through shellSingleQuote/shellDoubleQuoteEscape as of fleetdm#51324. - Escaping from fleetdm#51324 could be consistent across the whole file. This isn't really a bug or vuln now. - shellSingleQuote produces byte-identical output to the old '%s' literal for any string without an apostrophe, which covers every unique_identifier currently in the repo so this should be a no-op for existing golden-script tests/fixtures.
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…53570) **Related issue:** NA — found while reviewing #53566 # Checklist for submitter - [x] Changes file added for user-visible changes in `changes/`. - [x] Input data is properly validated, `SELECT *` is avoided, SQL injection is prevented (using placeholders for values in statements), JS inline code is prevented especially for url redirects, and untrusted data interpolated into shell scripts/commands is validated against shell metacharacters. ## What & why `quit_and_track_application` and `relaunch_application` derive the name of the "was it running" flag from the bundle ID and interpolate it into an `eval`: ```sh local var_name="APP_WAS_RUNNING_$(echo "$bundle_id" | tr '.-' '__')" eval "export $var_name=1" ``` `tr '.-' '__'` maps only dots and dashes. Any other character survives into the variable name, and a space breaks the `eval` in two: - **Write:** `eval "export APP_WAS_RUNNING_org_mozilla_pale moon=1"` — `export` takes two arguments, so it sets `APP_WAS_RUNNING_org_mozilla_pale` and a stray `moon=1`. The intended variable is never set. - **Read:** `eval "was_running=$APP_WAS_RUNNING_org_mozilla_pale moon"` — assigns empty, then tries to run `moon` as a command, printing `moon: command not found` into the install output. - **Result:** `was_running` is empty, so `relaunch_application` returns early. **Pale Moon hits this today.** `pale-moon.json` has `"unique_identifier": "org.mozilla.pale moon"`, and the shipped script calls `quit_and_track_application 'org.mozilla.pale moon'`. The app is quit during an update and never reopened. It is the only one of the 967 shipping macOS FMAs affected — every other identifier is drawn from `[A-Za-z0-9._-]`. This replaces the derivation with bash parameter expansion that maps everything outside `[A-Za-z0-9_]`: ```sh local var_name="APP_WAS_RUNNING_${bundle_id//[^[:alnum:]_]/_}" ``` Also applied to the thirteen custom install scripts under `inputs/homebrew/scripts/` that carry their own copy of these functions, so the two don't drift. ### Reviewer notes - **Inert for every app but pale-moon.** For identifiers drawn from `[A-Za-z0-9._-]` the new mapping produces a byte-identical variable name to `tr '.-' '__'`. I compared old vs. new across all 967 homebrew `unique_identifier` values: 966 identical, 1 changed (pale-moon, the broken one). Runtime behavior for every other app is unchanged. - **Why parameter expansion instead of `tr -c '[:alnum:]_' '_'`.** Same result, but no subshell, and it sidesteps two hazards: `echo` appends a newline that `tr -c` would map to a trailing underscore, and BSD vs. GNU `tr` differences in CI. Verified on `/bin/bash` 3.2, the macOS runtime — generated scripts have used a bash shebang since #44836. - **No output regeneration here.** This changes a shared function body, so all 956 generated scripts containing it will shift by two lines when the nightly regenerates. That matches how prior changes to these same functions landed (#43842, #42951, #44836 were all generator-only). - **Not a security fix.** `unique_identifier` comes from Fleet's own input files, not the brew API, so this isn't the untrusted-input class #51324 addressed. Hardening the `eval` is still worthwhile because the name reaches a root-privileged `eval`, but the bug being fixed is the relaunch failure. ## Testing - [x] Added/updated automated tests `TestQuitRelaunchVarNameSurvivesEval` runs the real write/read round trip through bash for four shipping identifier shapes including `org.mozilla.pale moon`, and asserts the flag survives. `TestQuitRelaunchVarNameNeutralizesCommandSubstitution` asserts the derived name is a bare shell identifier and that a `$(touch ...)` payload doesn't execute. `TestQuitAndRelaunchDeriveVarNameIdentically` pins the two derivations to the same line so they can't drift, and `TestCustomInstallScriptsDoNotUseOldVarNameDerivation` fails if any custom install script still uses `tr '.-' '__'`. Confirmed these fail against the old derivation: under `set -u`, pale-moon errors with `APP_WAS_RUNNING_org_mozilla_pale: unbound variable`; without it, the read back is silently empty. - [x] QA'd all new/changed functionality manually `go test ./ee/maintained-apps/...` passes. `bash -n` clean on all thirteen patched custom scripts. `go vet` and `gofmt` clean. (`make lint-go-incremental` couldn't run locally — it needs a network clone of golangci-lint — so leaving that to CI.) ## AI **AI:** Claude Code (claude-opus-5) <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit * **Bug Fixes** * Fixed macOS app updates so Fleet-maintained apps with spaces or other special characters in their bundle identifiers can relaunch successfully. * Improved tracking of whether applications were running before installation for identifiers containing special characters. * **Tests** * Added coverage for application tracking with special-character identifiers. <!-- end of auto-generated comment: release notes by coderabbit.ai -->
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…#56969) **Related issue:** Resolves fleetdm/security#154 ## What & why The Homebrew ingester copies a cask's uninstall and zap `quit` values into the generated FMA scripts. `quit_application` then put the value inside an AppleScript string (`osascript -e "application id \"$bundle_id\" is running"`), and the script runs as root. `shellSingleQuote` only protects the shell layer, so a quit value containing a double quote could close the AppleScript string and run `do shell script` as root on every host that uninstalls the app. I reproduced this locally with the issue's payload. The fix has two layers: - **Ingest validation.** `validateQuitIDs` rejects a cask whose uninstall or zap quit entries don't match `^[A-Za-z0-9 ._*-]+$`, and the ingest fails, as it does for a cask with no version. The pattern allows spaces because real casks use them (`org.mozilla.pale moon`, `com.native-instruments.Native Access`). I checked it against all 1,582 quit values in the Homebrew cask API, and every Fleet-maintained app passes. The only miss is `samsung-magician` (an `/Applications/...` path), which isn't a Fleet-maintained app. Valid values generate the same scripts as before. - **The ID goes in as data, not script text.** `quit_application` and `quit_and_track_application` now pass the ID as a run handler argument: `osascript -e 'on run argv' -e '… application id (item 1 of argv) …' -e 'end run' -- "$bundle_id"`. The `--` is required. osascript keeps parsing options after the script, so without it an ID starting with `-e` adds its own AppleScript statement. ### Rollout - The generator helpers in `scripts.go`, plus all 47 custom scripts in `inputs/homebrew/scripts/` that copy them, including the `$b` and `$BUNDLE_ID` variants. Three custom scripts hard-code their ID and are unchanged. - 56 outputs patched in place with no version change: - the 13 frozen ones, which the ingest job never rewrites - the 43 non-frozen custom-script ones, so the validator runs the hand-written scripts in this PR - The other 923 non-frozen generated outputs are left to the ingest job, which regenerates them after merge. **Expect its first run to touch ~923 outputs**, each with only these line changes. ### Reviewer notes - The output change is exactly two line rewrites, plus one comment in `quit_matching_applications`. Regenerating elgato-wave-link, balenaetcher and slack through the ingester produced the same scripts as the rewrite, at unchanged versions. Slack's regenerated output was byte-identical to the patched one. - Each patched output round-trips byte-identically through the manifest encoder, apart from the scripts and their refs. Custom-script outputs match their input files exactly. - This is the same issue class as GHSA-fv3p-h7wv-2jgm (#51324): cask metadata reaching a root script. ## Testing - [x] Added/updated automated tests - `TestValidateQuitIDs`: real-world values pass. Injection payloads are rejected in uninstall and zap stanzas, in both string and list form. - `TestIngestValidations`: ingesting a cask with the issue's payload in uninstall or zap fails, and Pale Moon's real quit value ingests. Both injection cases fail when the check is disabled. - `TestQuitHelpersPassBundleIDAsData`: fails if any generated helper or custom script puts a variable inside an AppleScript string, or if an argv call is missing `--`. - The `osascript` stubs in the existing quit tests read the new argument layout. - [x] QA'd all new/changed functionality manually - On a Mac, the new helpers quit a real app (Calculator) and still set the relaunch flag. The issue's payload, a string-concatenation payload and a leading-`-e` payload all ran nothing; the old form ran the payload. - `bash -n` passes on all rewritten custom scripts and on the 112 scripts in the patched outputs. - `gofmt` and `go vet` are clean. `make lint-go-incremental` couldn't run locally because the local golangci-lint fails to build the custom linter, so CI's lint job is the first lint run. - [x] Input data is properly validated, and untrusted data interpolated into shell scripts/commands is validated against shell metacharacters. ## AI **AI:** Claude Code (claude-opus-5-5) <!-- This is an auto-generated comment: release notes by coderabbit.ai --> <!-- coderabbit-ai-generated:v1 --> ## Summary by CodeRabbit * **Bug Fixes** * Homebrew app ingestion now rejects invalid quit identifiers before generating uninstall scripts, while valid identifiers continue to be supported. * macOS install and uninstall scripts now handle application identifiers consistently when checking whether apps are running or asking them to quit. Existing quit and installation flows are preserved. <!-- end of auto-generated comment: release notes by coderabbit.ai -->
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Related issue: Resolves fleetdm/confidential#17171 (draft advisory
GHSA-fv3p-h7wv-2jgm)What & why
The Fleet-maintained apps Homebrew ingester (
ee/maintained-apps/ingesters/homebrew/scripts.go) interpolated cask-controlled metadata into the generated install/uninstall scripts through double-quoted and unquoted-heredoc contexts, where shell command substitution is not neutralized. The same "package metadata → generated script" hardening previously applied to the admin-upload and winget paths was never applied here.This routes every cask-controlled interpolation site through explicit escaping or an inertness check:
shellDoubleQuoteEscape(new) for values that sit inside an existing double-quoted string alongside"$APPDIR"/"$TMPDIR"(app copymv/cp/rm,sudo rm -rfon uninstall, theinstaller -pkgfilename). It backslash-escapes only the four characters that stay special inside double quotes (\ $`"). Values without metacharacters — the common case — pass through byte-for-byte unchanged.escapeCaskPath(new) for the symlink (binaryartifact)lnarguments: same escaping, but a leading literal$APPDIRis preserved because every real binary-artifact source is"$APPDIR/Foo.app/..."and legitimately expands at runtime. Everything after the prefix is treated as data.inertShellWord(new) gates themkdirline for the symlink parent dir: inert paths (optional$APPDIRprefix + filename-safe bytes, no leading dash) keep the historical unquotedmkdir -p <path>form; anything else getsmkdir -p -- "<escaped>"(the--stops a leading dash being parsed as an option).heredocInert(new) gates the pkg choice XML: XML with no$/backtick/backslash and no line equal to the delimiter keeps the historicalcat << EOFheredoc; anything else is written viaprintf '%s\n' '<single-quoted xml>', which the shell can't interpret (an unquoted heredoc expands its body, and a body line equal to the delimiter ends it early and runs the remainder as commands).shellSingleQuotefor the uninstallscriptdirective (was a bare'%s'that an embedded apostrophe could break out of).Reviewer notes
zed,cursor,docker-desktop,surge,virtualbox, andmicrosoft-wordthrough the ingester: all install/uninstall script refs byte-identical except upstream version bumps (which only move the installer filename, already neutralized bynormalizeInstallerFilename).$APPDIRneeds special handling on the symlink path: unlike the other sinks, where"$APPDIR/is part of the Go template and only the suffix is cask data, thebinaryartifact's source/target strings embed$APPDIR(e.g."$APPDIR/Zed.app/Contents/MacOS/cli"). Escaping them wholesale would emit\$APPDIRand break the symlink for all ~28 binary-artifact apps.file.ValidatePackageIdentifiershere (as on the winget path): it rejects all shell metacharacters, which is fine for GUID product/upgrade codes but not for macOS app paths, which legitimately contain apostrophes (Cycling '74), spaces, and parentheses (Adobe Photoshop (2024).app). Correct quoting/escaping is the equivalent-strength control for this input class; the repo already relies onshellSingleQuotefor exactly this reason.Testing
Added/updated automated tests — regression tests assert metacharacter payloads (
$(...), backtick, apostrophe, leading dash) appear literally in the generated scripts at each sink; byte-exact tests pin the historical output for the shapes every real cask uses (bare and$APPDIRsymlink targets, inert choice XML); unit tests forshellDoubleQuoteEscape,escapeCaskPath,inertShellWord, andheredocInert.QA'd all new/changed functionality manually
bash -non generated scripts is valid; executed the choice-XML write path and confirmed a hostile payload is written as literal data and does not execute.Changes file added in
changes/.Untrusted data interpolated into shell scripts is validated/escaped against shell metacharacters.
Summary by CodeRabbit