#!/usr/bin/env bash
#
# Credentials, before they are committed.
#
# ## Why this and not a generic scanner
#
# A general-purpose secret scanner knows about AWS keys and GitHub tokens. It
# does not know that *this* deployment issues `pllc_agent_<hex>`, or that its
# encrypted envelopes start `v2:<keyid>:`, or which of its environment variables
# hold a password. The project does know, and usually writes it down twice: once
# in whatever redacts its logs, and once in whatever redacts its outbound
# messages.
#
# So this reads the project's own patterns where they exist — point
# `SECRETS_PATTERN_FILE` at the module holding them — and falls back to a
# conservative built-in set. A scanner tuned to the shapes a project actually
# issues catches the leak a generic one misses, and stays quiet the rest of the
# time.
#
# ## What it scans
#
# By default the **staged diff**, which is the only moment a commit can still be
# stopped cheaply. `--tracked` scans every tracked file instead, which is what
# you want once, on adoption, to find what is already in the history's tip.
#
#   bash scripts/secrets.sh                 # staged changes (use in pre-commit)
#   bash scripts/secrets.sh --tracked       # everything tracked, for an audit
#   SECRETS_PATTERN_FILE=src/lib/log.ts bash scripts/secrets.sh
#   bash scripts/secrets.sh --allow docs/examples/
#
# ## What it cannot do
#
# It reads the working tree and the index. **A secret already committed is still
# in the history** after you delete it, and this will not tell you that — the
# fix there is a rotation, not a scan. Rotate first, then clean up.
#
# Exit codes: 0 nothing found. 1 a candidate found. 2 nothing was scanned.
# ---------------------------------------------------------------------------

set -uo pipefail

cd "$(git rev-parse --show-toplevel 2>/dev/null)" || {
  printf 'secrets: not a git repository.\n' >&2
  exit 2
}

say() { printf 'secrets: %s\n' "$*" >&2; }

MODE="staged"
ALLOW=()

while [ $# -gt 0 ]; do
  case "$1" in
    --tracked) MODE="tracked"; shift ;;
    --staged)  MODE="staged";  shift ;;
    --allow)   ALLOW+=("${2:-}"); shift 2 ;;
    *)         say "unknown argument: $1"; exit 2 ;;
  esac
done

# The built-in set. Deliberately shapes that are *structurally* credential-like
# rather than words that merely appear near credentials — `password` in a
# sentence is not a leak, and a scanner that says it is gets muted.
PATTERNS=(
  '//[^/@[:space:]:]+:[^/@[:space:]]+@'                 # user:pass@host in a URL
  '[?&](token|key|secret|password|access_token|api_key)=[^&[:space:]"]+'
  '\b(Bearer|Basic)[[:space:]]+[A-Za-z0-9._~+/=-]{20,}' # an authorization header
  # Anchored to the start of a line or an `export`, because unanchored it
  # matched `access_token = $1` in SQL and `apiKey=` in a property list — three
  # findings in src/ that were column names, not credentials.
  '(^|export )[A-Z][A-Z0-9_]*(SECRET|TOKEN|PASSWORD|API_KEY|PASSWD)[A-Z0-9_]*=[^[:space:]"'"'"']{8,}'
  '-----BEGIN [A-Z ]*PRIVATE KEY-----'
  '\bghp_[A-Za-z0-9]{20,}'                              # GitHub
  '\bxox[baprs]-[A-Za-z0-9-]{10,}'                      # Slack
  '\bAKIA[0-9A-Z]{16}\b'                                # AWS access key id
)

# The project's own shapes, if it has written them down. A `pllc_agent_<hex>`
# token is invisible to every generic scanner and obvious to the module that
# redacts it.
if [ -n "${SECRETS_PATTERN_FILE:-}" ] && [ -f "$SECRETS_PATTERN_FILE" ]; then
  loaded=0

  # Anchored on the closing `/flags,` and greedy to it, rather than on "no
  # commas". The first version used `[^,]+`, which cannot cross the comma inside
  # a bounded quantifier — so `pllc_[a-z]+_[0-9a-f]{8,}` was silently dropped
  # along with every other `{n,}` pattern: four of six on the file this was
  # written against, while the script printed that it had loaded them.
  while IFS= read -r found; do
    [ -n "$found" ] || continue

    PATTERNS+=("$found")
    loaded=$((loaded + 1))
  done < <(
    sed -nE 's/.*\[\/(.+)\/[gimsuy]*,[[:space:]]*".*/\1/p' "$SECRETS_PATTERN_FILE" 2>/dev/null || true
  )

  # The count, never a bare reassurance. "Loaded project patterns" over an empty
  # list is the same lie as a green test run that executed nothing.
  if [ "$loaded" -gt 0 ]; then
    say "loaded $loaded project pattern(s) from $SECRETS_PATTERN_FILE"
  else
    say "WARNING: $SECRETS_PATTERN_FILE yielded no patterns — scanning with the"
    say "         built-in set only. Check the file holds regex literals."
  fi
fi

if [ "$MODE" = "staged" ]; then
  # Added lines only. A removed line containing a token is somebody deleting
  # one, which is the opposite of a leak.
  CONTENT="$(git diff --cached --unified=0 --no-color | grep '^+' | grep -v '^+++' || true)"
  WHAT="staged changes"
else
  CONTENT=""
  WHAT="tracked files"

  while IFS= read -r file; do
    skip=""

    for allowed in ${ALLOW[@]+"${ALLOW[@]}"}; do
      case "$file" in *"$allowed"*) skip="yes" ;; esac
    done

    [ -n "$skip" ] && continue
    [ -f "$file" ] || continue

    # Text only; a webp full of bytes will match anything.
    file "$file" 2>/dev/null | grep -q "text" || continue

    CONTENT+="$(sed "s|^|${file}: |" "$file")"$'\n'
  done < <(git ls-files)
fi

if [ -z "$CONTENT" ]; then
  say "nothing to scan in $WHAT."
  exit 2
fi

found=0

for pattern in "${PATTERNS[@]}"; do
  while IFS= read -r hit; do
    [ -n "$hit" ] || continue

    skip=""
    for allowed in ${ALLOW[@]+"${ALLOW[@]}"}; do
      case "$hit" in *"$allowed"*) skip="yes" ;; esac
    done
    [ -n "$skip" ] && continue

    # The line is printed truncated and the match is never echoed in full — a
    # scanner that prints the secret it found has published it to the terminal
    # scrollback, the CI log, and wherever that log is shipped.
    printf '  %.120s…\n' "$hit"
    found=$((found + 1))
  done < <(printf '%s\n' "$CONTENT" | grep -nEI "$pattern" 2>/dev/null | head -20)
done

if [ "$found" -gt 0 ]; then
  say "$found candidate credential(s) in $WHAT."
  say "If one is real: rotate it first. Deleting the line does not remove it"
  say "from a commit that already exists, and the scan cannot see history."
  exit 1
fi

say "no credential shapes in $WHAT."