使用 ShellCheck 进行静态分析与审计

ShellCheck 是什么以及它为何重要

# Debian / Ubuntu
sudo apt-get install shellcheck

# macOS (Homebrew)
brew install shellcheck

# From source via Cabal (any platform)
cabal update && cabal install ShellCheck

# Verify
shellcheck --version

首次运行 ShellCheck

#!/usr/bin/env bash
# demo_bad.sh — intentionally flawed for ShellCheck demonstration

FILE=$1

if [ $FILE == '' ]; then
  echo "No file given"
fi

cat $FILE | grep 'error' | wc -l

解读 ShellCheck 输出和 SC 代码

#!/usr/bin/env bash
# demo_fixed.sh — ShellCheck-clean

FILE="$1"

if [ -z "$FILE" ]; then
  echo "No file given" >&2
  exit 1
fi

grep -c 'error' "$FILE"

严重程度级别及应采取的措施

#!/usr/bin/env bash
# gate.sh — fail CI on errors and warnings only
shellcheck --severity=warning scripts/*.sh
echo "ShellCheck exit code: $?"

将 ShellCheck 集成为 CI 安全关卡

#!/usr/bin/env bash
# ci/shellcheck_gate.sh
set -euo pipefail

SCRIPTS=$(find . -name '*.sh' -not -path './.git/*')
FAILED=0

for script in $SCRIPTS; do
  echo "==> Checking: $script"
  if ! shellcheck --severity=warning --format=tty "$script"; then
    FAILED=1
  fi
done

if [ "$FAILED" -eq 1 ]; then
  echo "[GATE] ShellCheck found warnings or errors. Build blocked." >&2
  exit 1
fi

echo "[GATE] All scripts passed ShellCheck."

SC2086 系列：未加引号的变量展开

#!/usr/bin/env bash
# Attacker sets: FILENAME="important.txt /etc/passwd"
FILENAME="$1"

# UNSAFE — word splitting turns this into two args
rm $FILENAME

# SAFE — double quotes prevent splitting
rm "$FILENAME"

# Arrays are the right tool for lists
FILES=("$@")
rm -- "${FILES[@]}"

使用 SC2046 和 SC2035 检测命令注入风险

#!/usr/bin/env bash
# SC2046 example — output of find fed unquoted to chmod
# If a filename contains spaces, extra arguments appear

# UNSAFE
chmod 600 $(find /secrets -name '*.key')

# SAFE — use a while-read loop or xargs with -0
find /secrets -name '*.key' -print0 \
  | xargs -0 chmod 600

# SC2035 example
# UNSAFE — a file named '-rf' would be passed as an option
rm *.sh

# SAFE
rm -- ./*.sh

使用 JSON 输出格式实现自动化

#!/usr/bin/env bash
# Emit JSON and filter for only error-severity findings using jq
shellcheck --format=json scripts/deploy.sh \
  | jq '[.[] | select(.level == "error")]'

# Count distinct SC codes across all scripts
find . -name '*.sh' -print0 \
  | xargs -0 shellcheck --format=json 2>/dev/null \
  | jq '[.[] | .code] | group_by(.) | map({code: .[0], count: length}) | sort_by(-.count)'

正确抑制误报

#!/usr/bin/env bash
# deploy.sh

# Legitimate suppression: $DEPLOY_ARGS is intentionally word-split
# because it is a pre-validated list of flags from a trusted config file.
# shellcheck disable=SC2086
exec deploy-tool $DEPLOY_ARGS

# Block suppression for a section that generates dynamic code
# shellcheck disable=SC2016
VARS='$HOME $PATH $USER'
echo "Unexpanded vars: $VARS"
# shellcheck enable=SC2016

通过 .shellcheckrc 配置 ShellCheck

# .shellcheckrc — project root
shell=bash
enable=all
external-sources=true

# SC2312: consider invoking this command separately to avoid masking its
# return value — suppressed project-wide because we use set -e.
# Rationale: errexit already aborts on failure; masking risk is mitigated.
disable=SC2312

端到端加固脚本：前后对比

#!/usr/bin/env bash
# BEFORE — multiple ShellCheck violations
DEST=$1
SRC=$2
DATE=`date +%Y%m%d`

if [ ! -d $DEST ]; then
  mkdir $DEST
fi

cp -r $SRC $DEST/$DATE
echo Done


#!/usr/bin/env bash
# AFTER — ShellCheck-clean and hardened
set -euo pipefail

DEST="${1:?Usage: backup.sh <dest> <src>}"
SRC="${2:?Usage: backup.sh <dest> <src>}"
DATE=$(date +%Y%m%d)

if [ ! -d "$DEST" ]; then
  mkdir -p -- "$DEST"
fi

cp -r -- "$SRC" "$DEST/$DATE"
echo 'Done' >&2

知识检查：安全关卡中的 ShellCheck

回顾：作为安全关卡的静态分析