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🛡️ Sentinel: [HIGH] Fix shell quoting and command processing vulnerabilities #31

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🛡️ Sentinel: [HIGH] Fix shell quoting and command processing vulnerabilities #31

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4 changes: 4 additions & 0 deletions .jules/sentinel.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
## 2025-05-23 - Shell Script Variable Quoting and Globbing
**Vulnerability:** Found unquoted variables in `adduser` loop allowing password truncation/corruption (spaces/globs), and `VPNCMD_*` command processing vulnerable to glob injection and logic error (ignoring subsequent commands).
**Learning:** In bash, unquoted variables are subject to word splitting and glob expansion. `read` without `-r` interprets backslashes. Loops over `read` output need careful logic to ensure all input is processed.
**Prevention:** Always quote variables (`"$var"`) unless word splitting is explicitly intended. Use `read -r`. Use `set -f` when relying on word splitting but wanting to avoid globbing. Verify loop logic for multi-line/delimiter processing.
24 changes: 15 additions & 9 deletions copyables/entrypoint.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -140,13 +140,13 @@ if [ ! -f $CONFIG ] || [ ! -s $CONFIG ]; then
if [[ $USERS ]]; then
while IFS=';' read -ra USER; do
for i in "${USER[@]}"; do
IFS=':' read username password <<<"$i"
IFS=':' read -r username password <<<"$i"
# echo "Creating user: ${username}"
adduser $username $password
adduser "$username" "$password"
done
done <<<"$USERS"
else
adduser $USERNAME $PASSWORD
adduser "$USERNAME" "$PASSWORD"
fi

echo
Expand All @@ -156,15 +156,21 @@ if [ ! -f $CONFIG ] || [ ! -s $CONFIG ]; then

# handle VPNCMD_* commands right before setting admin passwords
if [[ $VPNCMD_SERVER ]]; then
while IFS=";" read -ra CMD; do
vpncmd_server $CMD
done <<<"$VPNCMD_SERVER"
set -f
IFS=";" read -ra CMDS <<<"$VPNCMD_SERVER"
for cmd in "${CMDS[@]}"; do
vpncmd_server $cmd
done
Comment on lines +161 to +163
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@gemini-code-assist gemini-code-assist bot Jan 29, 2026

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high

While set -f correctly prevents globbing, the unquoted expansion of $cmd performs word splitting that doesn't respect quotes within the command string. This will cause arguments containing spaces to be split incorrectly. For example, a command like UserSetPassword user "new password" would be broken. Using xargs can parse the command string correctly and handle quoted arguments, providing a safer alternative to eval.

Suggested change
for cmd in "${CMDS[@]}"; do
vpncmd_server $cmd
done
for cmd in "${CMDS[@]}"; do
# Use xargs to correctly parse the command string, respecting quoted arguments.
# This is safer than `eval` as it doesn't perform command substitution.
# The vpncmd_server function is inlined here to be callable from xargs.
echo "$cmd" | xargs --no-run-if-empty /usr/local/bin/vpncmd localhost /SERVER /CSV /CMD
done

set +f
Comment on lines +159 to +164
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@coderabbitai coderabbitai bot Jan 29, 2026

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⚠️ Potential issue | 🟠 Major

🧩 Analysis chain

🏁 Script executed:

# First, locate and read the entrypoint.sh file
find . -name "entrypoint.sh" -type f | head -20

Repository: bluPhy/docker-softether

Length of output: 92

🏁 Script executed:

# If found, let's read the relevant lines from the file
# Read around lines 159-164 and 168-173
if [ -f "copyables/entrypoint.sh" ]; then
  echo "=== Lines 155-175 of copyables/entrypoint.sh ==="
  sed -n '155,175p' copyables/entrypoint.sh | cat -n
fi

Repository: bluPhy/docker-softether

Length of output: 687

🏁 Script executed:

#!/bin/bash
set -euo pipefail
VPNCMD_SERVER='CmdA /ARG:pa\\ss;CmdB'
echo "Testing read behavior with and without -r flag:"
echo "Input: $VPNCMD_SERVER"
echo ""

IFS=";" read -a CMDS <<<"$VPNCMD_SERVER"
printf 'without -r: %q\n' "${CMDS[@]}"

IFS=";" read -r -a CMDS <<<"$VPNCMD_SERVER"
printf 'with -r: %q\n' "${CMDS[@]}"

Repository: bluPhy/docker-softether

Length of output: 234

Add -r to VPNCMD array reads to preserve backslashes in command arguments.

Lines 160 and 169 use read -a without -r, causing backslashes in VPNCMD_* commands to be interpreted as escape sequences. Without the -r flag, double backslashes are consumed and become single backslashes, which alters the intended command arguments.

Proposed fix 
-    IFS=";" read -ra CMDS <<<"$VPNCMD_SERVER"
+    IFS=";" read -r -a CMDS <<<"$VPNCMD_SERVER"
-    IFS=";" read -ra CMDS <<<"$VPNCMD_HUB"
+    IFS=";" read -r -a CMDS <<<"$VPNCMD_HUB"

Also applies to: 168-173

🤖 Prompt for AI Agents 
In `@copyables/entrypoint.sh` around lines 159 - 164, The loop that splits
VPNCMD_SERVER into CMDS uses IFS=";" read -ra CMDS <<<"$VPNCMD_SERVER" which
omits the -r flag and thus allows backslashes to be processed as escape
sequences; update the read usage (both here and in the similar block handling
VPNCMD_* arrays) to use read -r -a (e.g., read -r -a CMDS) so backslashes are
preserved in command arguments passed to vpncmd_server, leaving IFS and the rest
of the loop intact.

fi

if [[ $VPNCMD_HUB ]]; then
while IFS=";" read -ra CMD; do
vpncmd_hub $CMD
done <<<"$VPNCMD_HUB"
set -f
IFS=";" read -ra CMDS <<<"$VPNCMD_HUB"
for cmd in "${CMDS[@]}"; do
vpncmd_hub $cmd
done
Comment on lines +170 to +172
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@gemini-code-assist gemini-code-assist bot Jan 29, 2026

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high

Similar to the VPNCMD_SERVER loop, the unquoted expansion of $cmd here will incorrectly split arguments that contain spaces. Using xargs provides a robust way to parse the command string while respecting quotes.

Suggested change
for cmd in "${CMDS[@]}"; do
vpncmd_hub $cmd
done
for cmd in "${CMDS[@]}"; do
# Use xargs to correctly parse the command string, respecting quoted arguments.
# This is safer than `eval` as it doesn't perform command substitution.
# The vpncmd_hub function is inlined here to be callable from xargs.
echo "$cmd" | xargs --no-run-if-empty /usr/local/bin/vpncmd localhost /SERVER /CSV /HUB:DEFAULT /CMD
done

set +f
fi

# set password for hub
Expand Down