fix: strip line-break characters from hostnames and comments#90
Merged
Conversation
Comments and hostnames passed to AddHost/AddHostWithComment were trimmed but embedded carriage return, line feed, vertical tab, form feed, and NUL characters were preserved. Because lineFormatter interpolates these fields with %s, an embedded "\r\n" let a single logical entry render as multiple physical lines, corrupting the hosts file structure when read back by txeh or any other consumer (CWE-117, improper output neutralization). Add stripLineBreaks and apply it at the input boundary (addHostWithComment) and as a render-time backstop (lineFormatter) so no code path can emit a multi-line entry. Tabs, spaces, and # are preserved, so normal comments are unaffected. This is a defense-in-depth robustness fix for downstream library callers that may pass untrusted input. It is not the privilege-escalation vector described in the report: exploiting the CLI requires root and an attacker-controlled -w path, which already grants arbitrary file write without any comment trick. The public API is unchanged; input is stripped silently rather than rejected to preserve backward compatibility.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #90 +/- ##
==========================================
+ Coverage 89.51% 89.70% +0.18%
==========================================
Files 18 18
Lines 706 719 +13
==========================================
+ Hits 632 645 +13
Misses 64 64
Partials 10 10 🚀 New features to boost your workflow:
|
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
What
Strip
\r,\n,\v,\f, and NUL from hostnames and comments before they are written into the hosts file. Tabs, spaces, and#are preserved, so normal comments (added by kubefwd) are unaffected.Why
Comments and hostnames passed to
AddHost/AddHostWithCommentwere trimmed but embedded line-break characters were kept. BecauselineFormatterinterpolates these fields with%s, an embedded\r\nlet a single logical entry render as multiple physical lines, corrupting the hosts file structure when it is read back by txeh or any other consumer (CWE-117, improper output neutralization).The guard is applied in two places:
addHostWithComment) so the in-memory model stays clean.lineFormatter) so no code path can emit a multi-line entry, even when aHostFileLineis populated directly.On the report this came from
This was prompted by a "CRLF injection" report claiming privilege escalation (CVSS 6.7 / 8.8). That severity does not hold: every PoC requires root plus an attacker-controlled
-wpath, which already grants arbitrary file write without any comment trick. The restricted-sudo escalation is a sudoers misconfiguration, since-walone hands the user root file write.What is real is the data-hygiene gap fixed here: a library that writes structured files should not let one logical entry silently become several lines. Low severity, no CVE warranted.
Compatibility
The public API is unchanged. Input is stripped silently rather than rejected, so existing callers (including kubefwd) keep working without an error-handling change.
Tests
crlf_test.goadds:stripLineBreaksunit tests with hardcoded expected valueslineFormatterbackstop testgo test -race ./...passes, coverage 94.8% (gate 80%).