Intermittent "database disk image is malformed" after ROLLBACK TO undoes a DROP TRIGGER (4.12.0 – 4.19.0) #635

#!/usr/bin/env bash
# Intermittent "database disk image is malformed" after ROLLBACK TO undoes a DROP TRIGGER
# on an encrypted database. Uses only the SQLCipher command-line shell and bash.
#
# Usage: repro.sh <path to the sqlcipher shell> [iterations] [variant]
#   variant: savepoint (default) | no_read | transaction (control) |
#            plaintext (control: the savepoint sequence with no key, i.e. not encrypted)
#
# Each iteration creates a fresh database with a random 256-bit raw key, creates 10 tables
# and 13 triggers in one transaction, then drops and restores 4 triggers. The shell runs
# with -bail, so the first error stops it and is printed. On failure the database is
# reopened with the same key and checked with PRAGMA integrity_check.
#
# License: CC0 1.0 Universal (public domain dedication),
# https://creativecommons.org/publicdomain/zero/1.0/ - use it freely, e.g. in your tests.
set -euo pipefail

SQL_SHELL="${1:?path to the sqlcipher shell}"
N="${2:-10000}"
VARIANT="${3:-savepoint}"
WORKDIR="$(mktemp -d)"
trap 'rm -rf "${WORKDIR:?}"' EXIT

READ="SELECT count(*) FROM sqlite_schema WHERE type = 'trigger';"

schema() {
  echo "BEGIN;"
  for i in $(seq 0 9); do
    echo "CREATE TABLE t$i (id INTEGER PRIMARY KEY, a TEXT NOT NULL, b BLOB, c INTEGER);"
  done
  local events=(UPDATE DELETE INSERT INSERT)
  for n in 0 1 2 3; do
    echo "CREATE TRIGGER d$n BEFORE ${events[$n]} ON t0 WHEN $n >= 0 BEGIN SELECT RAISE(ABORT, 'trigger $n'); END;"
  done
  for i in $(seq 1 9); do
    echo "CREATE TRIGGER e$i BEFORE UPDATE OF a ON t$i BEGIN SELECT RAISE(ABORT, 'table $i'); END;"
  done
  echo "COMMIT;"
}

script() {
  [ "$VARIANT" = plaintext ] || echo "PRAGMA key = \"x'$1'\";"
  schema
  for n in 0 1 2 3; do
    case "$VARIANT" in
      transaction) echo "BEGIN; DROP TRIGGER d$n; $READ ROLLBACK;" ;;
      no_read) echo "SAVEPOINT s; DROP TRIGGER d$n; ROLLBACK TO s; RELEASE s;" ;;
      *) echo "SAVEPOINT s; DROP TRIGGER d$n; $READ ROLLBACK TO s; RELEASE s;" ;;
    esac
  done
  echo "$READ"
}

"$SQL_SHELL" :memory: <<< "PRAGMA key = \"x'00'\"; SELECT 'sqlite ' || sqlite_version(); PRAGMA cipher_version; PRAGMA cipher_provider_version;" | tail -n +2 | tr '\n' ' '
echo "| $(uname -sr)"

failures=0
for i in $(seq 1 "$N"); do
  db="${WORKDIR:?}/test-$i.db"
  key="$(od -An -tx1 -N32 /dev/urandom | tr -d ' \n')"
  if ! err="$(script "$key" | "$SQL_SHELL" -bail "$db" 2>&1 >/dev/null)"; then
    failures=$((failures + 1))
    if [ "$VARIANT" = plaintext ]; then
      reopened="$(printf 'PRAGMA integrity_check;\n%s\n' "$READ" | "$SQL_SHELL" "$db" 2>&1 | tr '\n' ' ')"
    else
      reopened="$(printf 'PRAGMA key = "x%s";\nPRAGMA integrity_check;\n%s\n' "'$key'" "$READ" \
        | "$SQL_SHELL" "$db" 2>&1 | tail -n +2 | tr '\n' ' ')"
    fi
    echo "[$i] ${err//$'\n'/ } | reopened: integrity_check, trigger count = $reopened"
  fi
  rm -f "${db:?}"
done
echo "$VARIANT: $N iterations, $failures failures"