scripts/db/postgresql.sh

#!/usr/bin/env bash
set -Eeo pipefail
# TODO swap to -Eeuo pipefail above (after handling all potentially-unset variables)
PGDATA="$DATABASE_DIR_PGSQL"
POSTGRES_USER="$DATABASE_USER_ROOT"
POSTGRES_PASSWORD="$DATABASE_PASS_ROOT"
# usage: file_env VAR [DEFAULT]
#    ie: file_env 'XYZ_DB_PASSWORD' 'example'
# (will allow for "$XYZ_DB_PASSWORD_FILE" to fill in the value of
#  "$XYZ_DB_PASSWORD" from a file, especially for Docker's secrets feature)
file_env() {
  local var="$1"
  local fileVar="${var}_FILE"
  local def="${2:-}"
  if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
    printf >&2 'error: both %s and %s are set (but are exclusive)\n' "$var" "$fileVar"
    exit 1
  fi
  local val="$def"
  if [ "${!var:-}" ]; then
    val="${!var}"
  elif [ "${!fileVar:-}" ]; then
    val="$(<"${!fileVar}")"
  fi
  export "$var"="$val"
  unset "$fileVar"
}

# check to see if this file is being run or sourced from another script
_is_sourced() {
  # https://unix.stackexchange.com/a/215279
  [ "${#FUNCNAME[@]}" -ge 2 ] &&
    [ "${FUNCNAME[0]}" = '_is_sourced' ] &&
    [ "${FUNCNAME[1]}" = 'source' ]
}

# used to create initial postgres directories and if run as root, ensure ownership to the "postgres" user
docker_create_db_directories() {
  local user
  user="$(id -u)"

  mkdir -p "$PGDATA"
  # ignore failure since there are cases where we can't chmod (and PostgreSQL might fail later anyhow - it's picky about permissions of this directory)
  chmod 700 "$PGDATA" || :

  # ignore failure since it will be fine when using the image provided directory; see also https://github.com/docker-library/postgres/pull/289
  mkdir -p /var/run/postgresql || :
  chmod 775 /var/run/postgresql || :

  # Create the transaction log directory before initdb is run so the directory is owned by the correct user
  if [ -n "${POSTGRES_INITDB_WALDIR:-}" ]; then
    mkdir -p "$POSTGRES_INITDB_WALDIR"
    if [ "$user" = '0' ]; then
      find "$POSTGRES_INITDB_WALDIR" \! -user postgres -exec chown postgres '{}' +
    fi
    chmod 700 "$POSTGRES_INITDB_WALDIR"
  fi

  # allow the container to be started with `--user`
  if [ "$user" = '0' ]; then
    find "$PGDATA" \! -user postgres -exec chown postgres '{}' +
    find /var/run/postgresql \! -user postgres -exec chown postgres '{}' +
  fi
}

# initialize empty PGDATA directory with new database via 'initdb'
# arguments to `initdb` can be passed via POSTGRES_INITDB_ARGS or as arguments to this function
# `initdb` automatically creates the "postgres", "template0", and "template1" dbnames
# this is also where the database user is created, specified by `POSTGRES_USER` env
docker_init_database_dir() {
  # "initdb" is particular about the current user existing in "/etc/passwd", so we use "nss_wrapper" to fake that if necessary
  # see https://github.com/docker-library/postgres/pull/253, https://github.com/docker-library/postgres/issues/359, https://cwrap.org/nss_wrapper.html
  local uid
  uid="$(id -u)"
  if ! getent passwd "$uid" &>/dev/null; then
    # see if we can find a suitable "libnss_wrapper.so" (https://salsa.debian.org/sssd-team/nss-wrapper/-/commit/b9925a653a54e24d09d9b498a2d913729f7abb15)
    local wrapper
    for wrapper in {/usr,}/lib{/*,}/libnss_wrapper.so; do
      if [ -s "$wrapper" ]; then
        NSS_WRAPPER_PASSWD="$(mktemp)"
        NSS_WRAPPER_GROUP="$(mktemp)"
        export LD_PRELOAD="$wrapper" NSS_WRAPPER_PASSWD NSS_WRAPPER_GROUP
        local gid
        gid="$(id -g)"
        printf 'postgres:x:%s:%s:PostgreSQL:%s:/bin/false\n' "$uid" "$gid" "$PGDATA" >"$NSS_WRAPPER_PASSWD"
        printf 'postgres:x:%s:\n' "$gid" >"$NSS_WRAPPER_GROUP"
        break
      fi
    done
  fi

  if [ -n "${POSTGRES_INITDB_WALDIR:-}" ]; then
    set -- --waldir "$POSTGRES_INITDB_WALDIR" "$@"
  fi

  # --pwfile refuses to handle a properly-empty file (hence the "\n"): https://github.com/docker-library/postgres/issues/1025
  eval 'initdb --username="$POSTGRES_USER" --pwfile=<(printf "%s\n" "$POSTGRES_PASSWORD") '"$POSTGRES_INITDB_ARGS"' "$@"'

  # unset/cleanup "nss_wrapper" bits
  if [[ "${LD_PRELOAD:-}" == */libnss_wrapper.so ]]; then
    rm -f "$NSS_WRAPPER_PASSWD" "$NSS_WRAPPER_GROUP"
    unset LD_PRELOAD NSS_WRAPPER_PASSWD NSS_WRAPPER_GROUP
  fi
}

# print large warning if POSTGRES_PASSWORD is long
# error if both POSTGRES_PASSWORD is empty and POSTGRES_HOST_AUTH_METHOD is not 'trust'
# print large warning if POSTGRES_HOST_AUTH_METHOD is set to 'trust'
# assumes database is not set up, ie: [ -z "$DATABASE_ALREADY_EXISTS" ]
docker_verify_minimum_env() {
  # check password first so we can output the warning before postgres
  # messes it up
  if [ "${#POSTGRES_PASSWORD}" -ge 100 ]; then
    cat >&2 <<-'EOWARN'

			WARNING: The supplied POSTGRES_PASSWORD is 100+ characters.

			  This will not work if used via PGPASSWORD with "psql".

			  https://www.postgresql.org/message-id/flat/E1Rqxp2-0004Qt-PL%40wrigleys.postgresql.org (BUG #6412)
			  https://github.com/docker-library/postgres/issues/507

		EOWARN
  fi
  if [ -z "$POSTGRES_PASSWORD" ] && [ 'trust' != "$POSTGRES_HOST_AUTH_METHOD" ]; then
    # The - option suppresses leading tabs but *not* spaces. :)
    cat >&2 <<-'EOE'
			Error: Database is uninitialized and superuser password is not specified.
			       You must specify POSTGRES_PASSWORD to a non-empty value for the
			       superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run".

			       You may also use "POSTGRES_HOST_AUTH_METHOD=trust" to allow all
			       connections without a password. This is *not* recommended.

			       See PostgreSQL documentation about "trust":
			       https://www.postgresql.org/docs/current/auth-trust.html
		EOE
    exit 1
  fi
  if [ 'trust' = "$POSTGRES_HOST_AUTH_METHOD" ]; then
    cat >&2 <<-'EOWARN'
			********************************************************************************
			WARNING: POSTGRES_HOST_AUTH_METHOD has been set to "trust". This will allow
			         anyone with access to the Postgres port to access your database without
			         a password, even if POSTGRES_PASSWORD is set. See PostgreSQL
			         documentation about "trust":
			         https://www.postgresql.org/docs/current/auth-trust.html
			         In Docker's default configuration, this is effectively any other
			         container on the same system.

			         It is not recommended to use POSTGRES_HOST_AUTH_METHOD=trust. Replace
			         it with "-e POSTGRES_PASSWORD=password" instead to set a password in
			         "docker run".
			********************************************************************************
		EOWARN
  fi
}

# usage: docker_process_init_files [file [file [...]]]
#    ie: docker_process_init_files /always-initdb.d/*
# process initializer files, based on file extensions and permissions
docker_process_init_files() {
  # psql here for backwards compatibility "${psql[@]}"
  psql=(docker_process_sql)

  printf '\n'
  local f
  for f; do
    case "$f" in
    *.sh)
      # https://github.com/docker-library/postgres/issues/450#issuecomment-393167936
      # https://github.com/docker-library/postgres/pull/452
      if [ -x "$f" ]; then
        printf '%s: running %s\n' "$0" "$f"
        "$f"
      else
        printf '%s: sourcing %s\n' "$0" "$f"
        . "$f"
      fi
      ;;
    *.sql)
      printf '%s: running %s\n' "$0" "$f"
      docker_process_sql -f "$f"
      printf '\n'
      ;;
    *.sql.gz)
      printf '%s: running %s\n' "$0" "$f"
      gunzip -c "$f" | docker_process_sql
      printf '\n'
      ;;
    *.sql.xz)
      printf '%s: running %s\n' "$0" "$f"
      xzcat "$f" | docker_process_sql
      printf '\n'
      ;;
    *.sql.zst)
      printf '%s: running %s\n' "$0" "$f"
      zstd -dc "$f" | docker_process_sql
      printf '\n'
      ;;
    *) printf '%s: ignoring %s\n' "$0" "$f" ;;
    esac
    printf '\n'
  done
}

# Execute sql script, passed via stdin (or -f flag of pqsl)
# usage: docker_process_sql [psql-cli-args]
#    ie: docker_process_sql --dbname=mydb <<<'INSERT ...'
#    ie: docker_process_sql -f my-file.sql
#    ie: docker_process_sql <my-file.sql
docker_process_sql() {
  local query_runner=(psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --no-password --no-psqlrc)
  if [ -n "$POSTGRES_DB" ]; then
    query_runner+=(--dbname "$POSTGRES_DB")
  fi

  PGHOST= PGHOSTADDR= "${query_runner[@]}" "$@"
}

# create initial database
# uses environment variables for input: POSTGRES_DB
docker_setup_db() {
  local dbAlreadyExists
  dbAlreadyExists="$(
    POSTGRES_DB= docker_process_sql --dbname postgres --set db="$POSTGRES_DB" --tuples-only <<-'EOSQL'
			SELECT 1 FROM pg_database WHERE datname = :'db' ;
		EOSQL
  )"
  if [ -z "$dbAlreadyExists" ]; then
    POSTGRES_DB= docker_process_sql --dbname postgres --set db="$POSTGRES_DB" <<-'EOSQL'
			CREATE DATABASE :"db" ;
		EOSQL
    printf '\n'
  fi
}

# Loads various settings that are used elsewhere in the script
# This should be called before any other functions
docker_setup_env() {
  file_env 'POSTGRES_PASSWORD'

  file_env 'POSTGRES_USER' 'postgres'
  file_env 'POSTGRES_DB' "$POSTGRES_USER"
  file_env 'POSTGRES_INITDB_ARGS'
  : "${POSTGRES_HOST_AUTH_METHOD:=}"

  declare -g DATABASE_ALREADY_EXISTS
  # look specifically for PG_VERSION, as it is expected in the DB dir
  if [ -s "$PGDATA/PG_VERSION" ]; then
    DATABASE_ALREADY_EXISTS='true'
  fi
}

# append POSTGRES_HOST_AUTH_METHOD to pg_hba.conf for "host" connections
# all arguments will be passed along as arguments to `postgres` for getting the value of 'password_encryption'
pg_setup_hba_conf() {
  # default authentication method is md5 on versions before 14
  # https://www.postgresql.org/about/news/postgresql-14-released-2318/
  if [ "$1" = 'postgres' ]; then
    shift
  fi
  local auth
  # check the default/configured encryption and use that as the auth method
  auth="$(postgres -C password_encryption "$@")"
  : "${POSTGRES_HOST_AUTH_METHOD:=$auth}"
  {
    printf '\n'
    if [ 'trust' = "$POSTGRES_HOST_AUTH_METHOD" ]; then
      printf '# warning trust is enabled for all connections\n'
      printf '# see https://www.postgresql.org/docs/12/auth-trust.html\n'
    fi
    printf 'host all all all %s\n' "$POSTGRES_HOST_AUTH_METHOD"
  } >>"$PGDATA/pg_hba.conf"
}

# start socket-only postgresql server for setting up or running scripts
# all arguments will be passed along as arguments to `postgres` (via pg_ctl)
docker_temp_server_start() {
  if [ "$1" = 'postgres' ]; then
    shift
  fi

  # internal start of server in order to allow setup using psql client
  # does not listen on external TCP/IP and waits until start finishes
  set -- "$@" -c listen_addresses='' -p "${PGPORT:-5432}"

  PGUSER="${PGUSER:-$POSTGRES_USER}" \
    pg_ctl -D "$PGDATA" \
    -o "$(printf '%q ' "$@")" \
    -w start
}

# stop postgresql server after done setting up user and running scripts
docker_temp_server_stop() {
  PGUSER="${PGUSER:-postgres}" \
    pg_ctl -D "$PGDATA" -m fast -w stop
}

# check arguments for an option that would cause postgres to stop
# return true if there is one
_pg_want_help() {
  local arg
  for arg; do
    case "$arg" in
    # postgres --help | grep 'then exit'
    # leaving out -C on purpose since it always fails and is unhelpful:
    # postgres: could not access the server configuration file "/var/lib/postgresql/data/postgresql.conf": No such file or directory
    -'?' | --help | --describe-config | -V | --version)
      return 0
      ;;
    esac
  done
  return 1
}

_main() {
  # if first arg looks like a flag, assume we want to run postgres server
  if [ "${1:0:1}" = '-' ]; then
    set -- postgres "$@"
  fi

  if [ "$1" = 'postgres' ] && ! _pg_want_help "$@"; then
    docker_setup_env
    # setup data directories and permissions (when run as root)
    docker_create_db_directories
    if [ "$(id -u)" = '0' ]; then
      # then restart script as postgres user
      exec su-exec postgres "$BASH_SOURCE" "$@"
    fi

    # only run initialization on an empty data directory
    if [ -z "$DATABASE_ALREADY_EXISTS" ]; then
      docker_verify_minimum_env

      # check dir permissions to reduce likelihood of half-initialized database
      ls /docker-entrypoint-initdb.d/ >/dev/null

      docker_init_database_dir
      pg_setup_hba_conf "$@"

      # PGPASSWORD is required for psql when authentication is required for 'local' connections via pg_hba.conf and is otherwise harmless
      # e.g. when '--auth=md5' or '--auth-local=md5' is used in POSTGRES_INITDB_ARGS
      export PGPASSWORD="${PGPASSWORD:-$POSTGRES_PASSWORD}"
      docker_temp_server_start "$@"

      docker_setup_db
      docker_process_init_files /docker-entrypoint-initdb.d/*

      docker_temp_server_stop
      unset PGPASSWORD

      cat <<-'EOM'

				PostgreSQL init process complete; ready for start up.

			EOM
    else
      cat <<-'EOM'

				PostgreSQL Database directory appears to contain a database; Skipping initialization

			EOM
    fi
  fi

  exec "$@"
}

if ! _is_sourced; then
  _main "$@"
fi