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fix: sanitize save hook transcript and session inputs #62

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fix: sanitize save hook transcript and session inputs #62

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46 changes: 32 additions & 14 deletions hooks/mempal_save_hook.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -64,20 +64,37 @@ MEMPAL_DIR=""
# Read JSON input from stdin
INPUT=$(cat)

# Parse all fields in a single Python call (3x faster than separate invocations)
eval $(echo "$INPUT" | python3 -c "
import sys, json
data = json.load(sys.stdin)
sid = data.get('session_id', 'unknown')
sha = data.get('stop_hook_active', False)
tp = data.get('transcript_path', '')
# Shell-safe output — only allow alphanumeric, underscore, hyphen, slash, dot, tilde
# Parse fields from Claude Code's JSON
# Parse stdin JSON once and keep transcript_path as data, not inline code.
readarray -t HOOK_FIELDS < <(
printf '%s' "$INPUT" | python3 -c '
import json
import sys

try:
payload = json.load(sys.stdin)
except Exception:
payload = {}

print(payload.get("session_id", "unknown"))
print(payload.get("stop_hook_active", False))
print(payload.get("transcript_path", ""))
'
)

SESSION_ID="${HOOK_FIELDS[0]:-unknown}"
STOP_HOOK_ACTIVE="${HOOK_FIELDS[1]:-False}"
TRANSCRIPT_PATH="${HOOK_FIELDS[2]:-}"

# Normalize session id so it cannot escape the hook state directory.
SAFE_SESSION_ID=$(printf '%s' "$SESSION_ID" | python3 -c '
import re
safe = lambda s: re.sub(r'[^a-zA-Z0-9_/.\-~]', '', str(s))
print(f'SESSION_ID=\"{safe(sid)}\"')
print(f'STOP_HOOK_ACTIVE=\"{sha}\"')
print(f'TRANSCRIPT_PATH=\"{safe(tp)}\"')
" 2>/dev/null)
import sys

value = sys.stdin.read().strip()
safe = re.sub(r"[^A-Za-z0-9_.-]", "_", value) or "unknown"
print(safe)
')

# Expand ~ in path
TRANSCRIPT_PATH="${TRANSCRIPT_PATH/#\~/$HOME}"
Expand All @@ -94,6 +111,7 @@ fi
if [ -f "$TRANSCRIPT_PATH" ]; then
EXCHANGE_COUNT=$(python3 - "$TRANSCRIPT_PATH" <<'PYEOF'
import json, sys

count = 0
with open(sys.argv[1]) as f:
for line in f:
Expand All @@ -115,7 +133,7 @@ else
fi

# Track last save point for this session
LAST_SAVE_FILE="$STATE_DIR/${SESSION_ID}_last_save"
LAST_SAVE_FILE="$STATE_DIR/${SAFE_SESSION_ID}_last_save"
LAST_SAVE=0
if [ -f "$LAST_SAVE_FILE" ]; then
LAST_SAVE=$(cat "$LAST_SAVE_FILE")
Expand Down