🛡️ Sentinel: [MEDIUM] Harden entrypoint.sh against shell injection #29
Conversation
- Hardened `copyables/entrypoint.sh` by quoting variables and using `read -r`. - Used `set -f` to prevent globbing during command argument splitting. - Fixed broken binary paths in `copyables/gencert.sh`. - Created `.jules/sentinel.md` with security learnings. Co-authored-by: bluPhy <11618798+bluPhy@users.noreply.github.com>
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Summary of ChangesHello @bluPhy, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request significantly enhances the security of the Sentinel system by addressing a medium-severity shell injection vulnerability within Highlights
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WalkthroughSecurity hardening improvements applied to shell scripts to prevent argument splitting and glob expansion vulnerabilities. Documentation added explaining the shell variable expansion vulnerability. Binary paths updated from Changes
Estimated code review effort🎯 2 (Simple) | ⏱️ ~10 minutes Poem
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Code Review
This pull request effectively hardens the entrypoint.sh script against shell injection vulnerabilities by quoting variables and disabling globbing during command execution. The path corrections in gencert.sh are also accurate. I've identified a critical bug in the command processing loops for VPNCMD_SERVER and VPNCMD_HUB, where only the first of multiple semicolon-separated commands would be executed. My review includes suggestions to fix this by properly iterating over all commands.
| set -f | ||
| while IFS=";" read -ra CMD; do | ||
| vpncmd_server $CMD | ||
| done <<<"$VPNCMD_SERVER" | ||
| set +f |
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While adding set -f/set +f is a good security measure, the loop it wraps contains a critical bug. It will only execute the first of multiple semicolon-separated commands provided in $VPNCMD_SERVER. This is because read -ra CMD correctly creates an array of commands, but vpncmd_server $CMD (on the next line) only expands to the first element of that array.
To fix this and ensure all commands are executed, you need to iterate over the array, similar to how the USERS variable is processed earlier in the script.
| set -f | |
| while IFS=";" read -ra CMD; do | |
| vpncmd_server $CMD | |
| done <<<"$VPNCMD_SERVER" | |
| set +f | |
| set -f | |
| while IFS=";" read -ra CMDS; do | |
| for cmd in "${CMDS[@]}"; do | |
| vpncmd_server $cmd | |
| done | |
| done <<<"$VPNCMD_SERVER" | |
| set +f |
| set -f | ||
| while IFS=";" read -ra CMD; do | ||
| vpncmd_hub $CMD | ||
| done <<<"$VPNCMD_HUB" | ||
| set +f |
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Similar to the VPNCMD_SERVER loop, this loop for VPNCMD_HUB is also bugged and will only execute the first of multiple semicolon-separated commands. The read -ra CMD populates an array, but vpncmd_hub $CMD only uses the first element.
To ensure all commands from $VPNCMD_HUB are processed, you must iterate over all elements of the array.
| set -f | |
| while IFS=";" read -ra CMD; do | |
| vpncmd_hub $CMD | |
| done <<<"$VPNCMD_HUB" | |
| set +f | |
| set -f | |
| while IFS=";" read -ra CMDS; do | |
| for cmd in "${CMDS[@]}"; do | |
| vpncmd_hub $cmd | |
| done | |
| done <<<"$VPNCMD_HUB" | |
| set +f |
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Actionable comments posted: 5
Caution
Some comments are outside the diff and can’t be posted inline due to platform limitations.
⚠️ Outside diff range comments (1)
copyables/entrypoint.sh (1)
149-149: Inconsistent quoting:$USERNAMEand$PASSWORDare unquoted.Line 145 correctly quotes
"$username"and"$password", but this line leaves$USERNAMEand$PASSWORDunquoted. For consistency and safety, these should also be quoted.Proposed fix
- adduser $USERNAME $PASSWORD + adduser "$USERNAME" "$PASSWORD"
🤖 Fix all issues with AI agents
In @.jules/sentinel.md:
- Line 1: The header line "## 2025-02-18 - Shell Script Injection via Globbing"
has an incorrect past date; update that date in the header to the correct
current date (e.g., "2026-01-27" or the intended publication date) so the
entry's timestamp is accurate, by editing the header string in
.jules/sentinel.md.
In `@copyables/entrypoint.sh`:
- Around line 167-171: The loop is erroneously expanding the CMD array with
unquoted word-splitting (vpncmd_hub $CMD) which loses elements; change the call
to use the array expansion vpncmd_hub "${CMD[@]}" so each read -ra CMD element
is passed as a separate argument to vpncmd_hub (leave the IFS=';' read -ra CMD
logic and set -f usage intact).
- Around line 159-163: The loop uses read -ra CMD to populate an array but then
calls vpncmd_server with "$CMD", which only expands the first element; change
the call to use the full array expansion ${CMD[*]} so all elements are passed as
separate words after IFS-based splitting (keep the surrounding set -f/set +f and
the read -ra CMD loop intact); locate the loop around the read -ra CMD and
replace the single-element expansion referenced by "$CMD" with the full
expansion ${CMD[*]} when invoking vpncmd_server.
In `@copyables/gencert.sh`:
- Line 4: The shell redirection in the command "/usr/local/bin/vpnserver start
2>&1 >/dev/null" is reversed so stderr is still printed; update the redirect to
silence both streams by reversing the order (e.g., ">/dev/null 2>&1") or using
the equivalent shorthand "&>/dev/null" on the line that runs
/usr/local/bin/vpnserver start. Ensure the changed redirection replaces the
existing one exactly where that command appears.
- Line 10: The shell command line invoking /usr/local/bin/vpncmd currently
redirects stderr before stdout ("2>&1 >/dev/null"), which leaves stderr attached
to the original stdout; swap the redirections so stdout is redirected to
/dev/null first and then stderr is redirected to the same place (or use a single
shell operator like &>/dev/null) to silence both; update the line containing
"/usr/local/bin/vpncmd localhost /SERVER /CSV /CMD OpenVpnEnable yes
/PORTS:1194" accordingly.
🧹 Nitpick comments (1)
copyables/entrypoint.sh (1)
62-62: Pre-existing: incorrect redirect order.Same issue as in
gencert.sh- the redirect2>&1 >/dev/nulldoesn't silence stderr. Consider fixing for consistency.Proposed fix
- /usr/local/bin/vpnserver start 2>&1 >/dev/null + /usr/local/bin/vpnserver start >/dev/null 2>&1Similar fixes needed on lines 68, 112, and 182.
| @@ -0,0 +1,5 @@ | |||
| ## 2025-02-18 - Shell Script Injection via Globbing | |||
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Date appears incorrect.
The date 2025-02-18 is in the past relative to the current date (January 2026). Should this be 2026-01-27 or another date?
🤖 Prompt for AI Agents
In @.jules/sentinel.md at line 1, The header line "## 2025-02-18 - Shell Script
Injection via Globbing" has an incorrect past date; update that date in the
header to the correct current date (e.g., "2026-01-27" or the intended
publication date) so the entry's timestamp is accurate, by editing the header
string in .jules/sentinel.md.
| set -f | ||
| while IFS=";" read -ra CMD; do | ||
| vpncmd_server $CMD | ||
| done <<<"$VPNCMD_SERVER" | ||
| set +f |
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Array expansion bug: only the first element is used.
read -ra CMD reads into an array, but $CMD without an index expands to only the first element (${CMD[0]}). This means multi-word commands will be truncated.
To preserve argument splitting (the intent behind set -f) while using the full array, use ${CMD[*]} which expands to all elements separated by the first character of IFS, then word-splits:
Proposed fix
set -f
while IFS=";" read -ra CMD; do
- vpncmd_server $CMD
+ vpncmd_server ${CMD[*]}
done <<<"$VPNCMD_SERVER"
set +f📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| set -f | |
| while IFS=";" read -ra CMD; do | |
| vpncmd_server $CMD | |
| done <<<"$VPNCMD_SERVER" | |
| set +f | |
| set -f | |
| while IFS=";" read -ra CMD; do | |
| vpncmd_server ${CMD[*]} | |
| done <<<"$VPNCMD_SERVER" | |
| set +f |
🧰 Tools
🪛 Shellcheck (0.11.0)
[warning] 161-161: Expanding an array without an index only gives the first element.
(SC2128)
🤖 Prompt for AI Agents
In `@copyables/entrypoint.sh` around lines 159 - 163, The loop uses read -ra CMD
to populate an array but then calls vpncmd_server with "$CMD", which only
expands the first element; change the call to use the full array expansion
${CMD[*]} so all elements are passed as separate words after IFS-based splitting
(keep the surrounding set -f/set +f and the read -ra CMD loop intact); locate
the loop around the read -ra CMD and replace the single-element expansion
referenced by "$CMD" with the full expansion ${CMD[*]} when invoking
vpncmd_server.
| set -f | ||
| while IFS=";" read -ra CMD; do | ||
| vpncmd_hub $CMD | ||
| done <<<"$VPNCMD_HUB" | ||
| set +f |
There was a problem hiding this comment.
Same array expansion bug.
Proposed fix
set -f
while IFS=";" read -ra CMD; do
- vpncmd_hub $CMD
+ vpncmd_hub ${CMD[*]}
done <<<"$VPNCMD_HUB"
set +f📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| set -f | |
| while IFS=";" read -ra CMD; do | |
| vpncmd_hub $CMD | |
| done <<<"$VPNCMD_HUB" | |
| set +f | |
| set -f | |
| while IFS=";" read -ra CMD; do | |
| vpncmd_hub ${CMD[*]} | |
| done <<<"$VPNCMD_HUB" | |
| set +f |
🧰 Tools
🪛 Shellcheck (0.11.0)
[warning] 169-169: Expanding an array without an index only gives the first element.
(SC2128)
🤖 Prompt for AI Agents
In `@copyables/entrypoint.sh` around lines 167 - 171, The loop is erroneously
expanding the CMD array with unquoted word-splitting (vpncmd_hub $CMD) which
loses elements; change the call to use the array expansion vpncmd_hub
"${CMD[@]}" so each read -ra CMD element is passed as a separate argument to
vpncmd_hub (leave the IFS=';' read -ra CMD logic and set -f usage intact).
| set -e | ||
|
|
||
| /usr/bin/vpnserver start 2>&1 >/dev/null | ||
| /usr/local/bin/vpnserver start 2>&1 >/dev/null |
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Incorrect redirect order: stderr not silenced.
The redirect 2>&1 >/dev/null first redirects stderr to stdout (terminal), then redirects stdout to /dev/null. This means stderr still goes to the terminal. To silence both streams, the order should be reversed.
Proposed fix
-/usr/local/bin/vpnserver start 2>&1 >/dev/null
+/usr/local/bin/vpnserver start >/dev/null 2>&1📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| /usr/local/bin/vpnserver start 2>&1 >/dev/null | |
| /usr/local/bin/vpnserver start >/dev/null 2>&1 |
🧰 Tools
🪛 Shellcheck (0.11.0)
[warning] 4-4: To redirect stdout+stderr, 2>&1 must be last (or use '{ cmd > file; } 2>&1' to clarify).
(SC2069)
🤖 Prompt for AI Agents
In `@copyables/gencert.sh` at line 4, The shell redirection in the command
"/usr/local/bin/vpnserver start 2>&1 >/dev/null" is reversed so stderr is still
printed; update the redirect to silence both streams by reversing the order
(e.g., ">/dev/null 2>&1") or using the equivalent shorthand "&>/dev/null" on the
line that runs /usr/local/bin/vpnserver start. Ensure the changed redirection
replaces the existing one exactly where that command appears.
| while :; do | ||
| set +e | ||
| /usr/bin/vpncmd localhost /SERVER /CSV /CMD OpenVpnEnable yes /PORTS:1194 2>&1 >/dev/null | ||
| /usr/local/bin/vpncmd localhost /SERVER /CSV /CMD OpenVpnEnable yes /PORTS:1194 2>&1 >/dev/null |
There was a problem hiding this comment.
Same redirect order issue.
Proposed fix
- /usr/local/bin/vpncmd localhost /SERVER /CSV /CMD OpenVpnEnable yes /PORTS:1194 2>&1 >/dev/null
+ /usr/local/bin/vpncmd localhost /SERVER /CSV /CMD OpenVpnEnable yes /PORTS:1194 >/dev/null 2>&1📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| /usr/local/bin/vpncmd localhost /SERVER /CSV /CMD OpenVpnEnable yes /PORTS:1194 2>&1 >/dev/null | |
| /usr/local/bin/vpncmd localhost /SERVER /CSV /CMD OpenVpnEnable yes /PORTS:1194 >/dev/null 2>&1 |
🧰 Tools
🪛 Shellcheck (0.11.0)
[warning] 10-10: To redirect stdout+stderr, 2>&1 must be last (or use '{ cmd > file; } 2>&1' to clarify).
(SC2069)
🤖 Prompt for AI Agents
In `@copyables/gencert.sh` at line 10, The shell command line invoking
/usr/local/bin/vpncmd currently redirects stderr before stdout ("2>&1
>/dev/null"), which leaves stderr attached to the original stdout; swap the
redirections so stdout is redirected to /dev/null first and then stderr is
redirected to the same place (or use a single shell operator like &>/dev/null)
to silence both; update the line containing "/usr/local/bin/vpncmd localhost
/SERVER /CSV /CMD OpenVpnEnable yes /PORTS:1194" accordingly.
🛡️ Sentinel: [MEDIUM] Harden entrypoint.sh against shell injection
🚨 Severity: MEDIUM
💡 Vulnerability: Unquoted variable expansion in command processing loops allowed shell globbing (wildcard expansion), potentially leading to unintended file processing or execution if input contained characters like
*.🎯 Impact: Could be exploited to reference unexpected files or cause denial of service via malformed environment variables.
🔧 Fix: Hardened
entrypoint.shby:$CONFIG,$username,$password) to prevent word splitting.read -rto prevent backslash interpretation.set -f(noglob) around command execution loops to prevent wildcard expansion while allowing argument splitting.gencert.shpointing to/usr/bininstead of/usr/local/bin.✅ Verification: Verified script syntax with
bash -n.PR created automatically by Jules for task 6480463339127224038 started by @bluPhy
Summary by CodeRabbit
Bug Fixes
Documentation
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