File Coverage

blib/lib/EMDIS/ECS/Config.pm

Criterion	Covered	Total	%
statement	243	265	91.7
branch	104	140	74.2
condition	35	54	64.8
subroutine	15	16	93.7
pod	0	2	0.0
total	397	477	83.2

#!/usr/bin/perl -w
#
# Copyright (C) 2002-2026 National Marrow Donor Program. All rights reserved.
#
# For a description of this module, please refer to the POD documentation
# embedded at the bottom of the file (e.g. perldoc EMDIS::ECS::Config).

package EMDIS::ECS::Config;

use Carp;
use Cwd;
use EMDIS::ECS qw($VERSION is_yes is_no);
use File::Basename;
use File::Spec::Functions qw(catdir catfile file_name_is_absolute rel2abs);
use strict;
use Text::ParseWords;
use vars qw($AUTOLOAD %ok_attr);

# ----------------------------------------------------------------------
# initialize %ok_attr hash with valid attribute names
BEGIN
{
    my @attrlist = qw(
        MSG_PROC MAIL_MRK THIS_NODE T_CHK T_SCN ERR_FILE LOG_FILE ADM_ADDR
        M_MSG_PROC BCK_DIR ACK_THRES LOG_LEVEL MAIL_LEVEL
        ECS_BIN_DIR ECS_DAT_DIR ECS_TO_DIR ECS_FROM_DIR ECS_DEBUG
        NODE_TBL NODE_TBL_LCK T_ADM_DELAY T_ADM_REMIND T_MSG_PROC
        ADAPTER_CMD ALWAYS_ACK GNU_TAR T_RESEND_DELAY
        SMTP_HOST SMTP_DOMAIN SMTP_TIMEOUT SMTP_DEBUG SMTP_FROM SMTP_PORT
        SMTP_USE_SSL SMTP_USE_STARTTLS SMTP_USERNAME SMTP_PASSWORD
        INBOX_PROTOCOL INBOX_HOST INBOX_PORT INBOX_TIMEOUT INBOX_DEBUG
        INBOX_FOLDER INBOX_USERNAME INBOX_PASSWORD INBOX_MAX_MSG_SIZE
        INBOX_DIRECTORY INBOX_USE_SSL INBOX_USE_STARTTLS
        MSG_PART_SIZE_DFLT
        GPG_HOMEDIR GPG_KEYID GPG_PASSPHRASE
        OPENPGP_CMD_ENCRYPT OPENPGP_CMD_DECRYPT
        PGP_HOMEDIR PGP_KEYID PGP_PASSPHRASE
        PGP2_CMD_ENCRYPT PGP2_CMD_DECRYPT
        ENABLE_AMQP
        AMQP_BROKER_URL AMQP_VHOST AMQP_ADDR_META AMQP_ADDR_MSG AMQP_ADDR_DOC
        AMQP_TRUSTSTORE AMQP_SSLCERT AMQP_SSLKEY AMQP_SSLPASS
        AMQP_USERNAME AMQP_PASSWORD
        AMQP_RECV_TIMEOUT AMQP_RECV_TIMELIMIT AMQP_SEND_TIMELIMIT
        AMQP_DEBUG_LEVEL AMQP_CMD_SEND AMQP_CMD_RECV
        EMDIS_MESSAGE_VERSION ENABLE_ENV_CONFIG
        INBOX_OAUTH_TOKEN_CMD
        INBOX_OAUTH_TOKEN_CMD_TIMELIMIT
        INBOX_OAUTH_SASL_MECHANISM
        SMTP_OAUTH_TOKEN_CMD
        SMTP_OAUTH_TOKEN_CMD_TIMELIMIT
        SMTP_OAUTH_SASL_MECHANISM
    );
    for my $attr (@attrlist)
    {
        $ok_attr{$attr} = 1;
    }
}

# ----------------------------------------------------------------------
# use AUTOLOAD method to provide accessor methods
# (as described in Perl Cookbook)
sub AUTOLOAD
{
    my $this = shift;
    my $attr = $AUTOLOAD;
    $attr =~ s/.*:://;
    return unless $attr =~ /[^A-Z]/;  # skip DESTROY and all-cap methods
                                      # (for EMDIS::ECS::Config, all valid
                                      # attribute names contain at least
                                      # one underscore)
    croak "invalid attribute method: ->$attr()" unless $ok_attr{$attr};
    return $this->{uc $attr};
}

# ----------------------------------------------------------------------
# Constructor.
# Returns EMDIS::ECS::Config reference if successful or error message if
# error encountered.
sub new
{
    my $class = shift;
    my $cfg_file = shift;
    my $skip_val = shift;
    $skip_val = '' unless defined $skip_val;
    my $this = {};
    bless $this, $class;
    $cfg_file = 'ecs.cfg' unless defined($cfg_file);
    $this->{CFG_FILE} = $cfg_file;
    $this->{CFG_CWD} = cwd();   # remember cwd in case it may be needed
    $this->_set_defaults();
    return $this if $cfg_file eq '';  # default config (used by ecs_setup)
    my $err = $this->_read_config();
    return $err if $err;
    return $this if $skip_val;        # skip validation (used by ecs_setup)
    $err = $this->_massage_config();
    return $err if $err;
    $err = $this->_validate_config();
    return $err if $err;
    return $this;
}

# ----------------------------------------------------------------------
# Display configuration data.
sub display
{
    my $this = shift;
    my $fmt = "%-20s   %s\n";
    print "ECS_CFG\n";
    print "---------------------------------------------------------------\n";
    for my $attr (sort keys %$this) {
        my $value = $this->{$attr};
        $value = '********' if $attr =~ /PASSWORD|PASSPHRASE/i;
        printf $fmt, $attr, $value;
    }
}

# ----------------------------------------------------------------------
# Parse config file data.
# Returns empty string if successful or error message if error encountered.
sub _read_config
{
    my $this = shift;

    # read config file
    my $err = '';
    if(not open CONFIG, "< $this->{CFG_FILE}")
    {
        return "Unable to open config file '$this->{CFG_FILE}': $!";
    }
    while()
    {
        chomp;               # trim EOL character(s)
        s/^\s+//;            # trim leading whitespace
        s/\s+$//;            # trim trailing whitespace
        next unless length;  # skip blank line
        next if /^#/;        # skip comment line
        my @fields = ();
        my @tokens = split '\|';  # split on pipe ('|') delimiter
        for my $token (@tokens)
        {
            if($#fields >= 0 and $fields[$#fields] =~ /\\$/)
            {
                # rejoin tokens separated by escaped pipe ('\|')
                chop($fields[$#fields]);
                $fields[$#fields] .= "|$token";
            }
            else
            {
                push(@fields, $token);
            }
        }
        # trim leading & trailing whitespace
        @fields = map { s/^\s+//; s/\s+$//; $_; } @fields;
        my ($attr, $value, $comment) = @fields;
        if($ok_attr{$attr})
        {
            # store value
            $this->{$attr} = $value;
        }
        else
        {
            $err .=
                "Unexpected input '$attr' at $this->{CFG_FILE} line $.\n";
        }
    }
    close CONFIG;
    if($err)
    {
        return $err .
            "Error(s) encountered while attempting to process " .
                "$this->{CFG_FILE}.";
    }

    return '';
}

# ----------------------------------------------------------------------
# Massage config data.
# Returns empty string if successful or error message if error encountered.
sub _massage_config
{
    my $this = shift;

    # initialize
    my $err = '';
    my $script_dir = dirname($0);
    $script_dir = rel2abs($script_dir)
        unless file_name_is_absolute($script_dir);
    my $config_dir = dirname($this->{CFG_FILE});
    $config_dir = rel2abs($config_dir)
        unless file_name_is_absolute($config_dir);
    if(is_yes($this->{ENABLE_ENV_CONFIG}))
    {
        for my $attr (keys %ok_attr)
        {
            if(exists $this->{$attr})
            {
                my $value = $this->{$attr};
                # if value follows $ENV{envvar} pattern, use value of environment variable
                if($value =~ /^\$ENV\{(\S+)\}$/)
                {
                    my $envvar = $1;
                    my $env_value = $ENV{$envvar};
                    if(defined $env_value)
                    {
                        $this->{$attr} = $env_value;
                    }
                    else
                    {
                        $err .=
                            "Environment variable '$envvar' has undefined value - referenced by $attr in config file '$this->{CFG_FILE}'\n";
                    }
                }
            }
        }
    }

    # parse some special tokens
    for my $attr (keys %ok_attr)
    {
        if(exists $this->{$attr})
        {
            my $value = $this->{$attr};
            $value =~ s/__SCRIPT_DIR__/$script_dir/;
            $value =~ s/__CONFIG_DIR__/$config_dir/;
            $this->{$attr} = $value;
        }
    }

    # prepend ECS_DAT_DIR to non-absolute file/path names
    for my $attr (qw(ERR_FILE GPG_HOMEDIR LOG_FILE NODE_TBL NODE_TBL_LCK
                     PGP_HOMEDIR ECS_TO_DIR ECS_FROM_DIR))
    {
        # don't prepend to special LOG_FILE value __STDOUT__
        next if $attr eq 'LOG_FILE' and $this->{$attr} eq '__STDOUT__';

        $this->{$attr} = catfile($this->{ECS_DAT_DIR}, $this->{$attr})
            if exists($this->{$attr})
                and not ($this->{$attr} eq '')
                and not file_name_is_absolute($this->{$attr});
    }

    # prepend ECS_BIN_DIR to non-absolute executable command names
    for my $attr (qw(MSG_PROC M_MSG_PROC))
    {
        $this->{$attr} = catfile($this->{ECS_BIN_DIR}, $this->{$attr})
            if exists($this->{$attr})
                and not file_name_is_absolute($this->{$attr});
    }

    # compute derived values
    $this->{ECS_TMP_DIR} = catdir($this->{ECS_DAT_DIR}, 'tmp');
    if ( ! defined($this->{ECS_TO_DIR}) || $this->{ECS_TO_DIR} eq '')
    {
       $this->{ECS_DRP_DIR} = catdir($this->{ECS_DAT_DIR}, 'maildrop');
    }
    else
    {
       $this->{ECS_DRP_DIR} = $this->{ECS_TMP_DIR};
    }
    $this->{ECS_MBX_DIR} = catdir($this->{ECS_DAT_DIR}, 'mboxes');
    $this->{ECS_MBX_AMQP_STAGING_DIR} = catdir($this->{ECS_MBX_DIR}, 'amqp_staging');
    $this->{ECS_MBX_IN_DIR}     = catdir($this->{ECS_MBX_DIR}, 'in');
    $this->{ECS_MBX_IN_FML_DIR} = catdir($this->{ECS_MBX_DIR}, 'in_fml');
    $this->{ECS_MBX_OUT_DIR}    = catdir($this->{ECS_MBX_DIR}, 'out');
    $this->{ECS_MBX_TRASH_DIR}  = catdir($this->{ECS_MBX_DIR}, 'trash');
    $this->{ECS_MBX_STORE_DIR}  = catdir($this->{ECS_MBX_DIR}, 'store');
    for my $attr (qw(ECS_TMP_DIR ECS_DRP_DIR ECS_MBX_DIR
                     ECS_MBX_AMQP_STAGING_DIR ECS_MBX_IN_DIR
                     ECS_MBX_IN_FML_DIR ECS_MBX_OUT_DIR ECS_MBX_TRASH_DIR
                     ECS_MBX_STORE_DIR))
    {
        $ok_attr{$attr} = 1;
    }

    # parse more special tokens
    for my $attr (keys %ok_attr)
    {
        if(exists $this->{$attr})
        {
            my $value = $this->{$attr};
            $value =~ s/__MAILDROP_DIR__/$this->{ECS_DRP_DIR}/;
            $this->{$attr} = $value;
        }
    }

    # if indicated, assign SMTP_PORT default value
    if(not defined($this->{SMTP_PORT})) {
        $this->{SMTP_PORT} = 25;
        $this->{SMTP_PORT} = 465 if is_yes($this->{SMTP_USE_SSL});
        $this->{SMTP_PORT} = 587 if is_yes($this->{SMTP_USE_STARTTLS});
    }

    # if indicated, assign INBOX_PORT default value
    if(not defined($this->{INBOX_PORT})) {
        for($this->{INBOX_PROTOCOL})
        {
            /POP3/ and do {
                $this->{INBOX_PORT} = 110;
                $this->{INBOX_PORT} = 995 if is_yes($this->{INBOX_USE_SSL});
            };
            /IMAP/ and do {
                $this->{INBOX_PORT} = 143;
                $this->{INBOX_PORT} = 993 if is_yes($this->{INBOX_USE_SSL});
            };
        }
    }

    return $err;
}

# ----------------------------------------------------------------------
# Assign default values to configuration settings.
# Note:  no default value for THIS_NODE, ADM_ADDR, ADAPTER_CMD, SMTP_DOMAIN,
# SMTP_FROM, SMTP_PORT, SMTP_USERNAME, SMTP_PASSWORD, INBOX_PORT,
# INBOX_FOLDER, INBOX_USERNAME, INBOX_PASSWORD, GPG_HOMEDIR, GPG_KEYID,
# GPG_PASSPHRASE, PGP_HOMEDIR, PGP_KEYID, PGP_PASSPHRASE,
# AMQP_BROKER_URL, AMQP_VHOST, AMQP_TRUSTSTORE, AMQP_SSLCERT AMQP_SSLKEY,
# AMQP_SSLPASS, AMQP_USERNAME, AMQP_PASSWORD
sub _set_defaults
{
    my $this = shift;
    $this->{MSG_PROC}          = "ecs_proc_msg";
    $this->{MAIL_MRK}          = "EMDIS";
    $this->{T_CHK}             = "7200";
    $this->{T_SCN}             = "3600";
    $this->{ENABLE_ENV_CONFIG} = 'YES';
    my $basename = basename($0);   # default;  use magic logfile name
    $this->{ERR_FILE}          = "$basename.err";
    $this->{LOG_FILE}          = "$basename.log";
    $this->{M_MSG_PROC}        = "ecs_proc_meta";
    $this->{BCK_DIR}           = "NONE";
    $this->{ACK_THRES}         = "100";
    $this->{ALWAYS_ACK}        = "NO";
    $this->{GNU_TAR}           = "/usr/bin/tar";
    $this->{ECS_BIN_DIR}       = "__SCRIPT_DIR__";
    $this->{ECS_DAT_DIR}       = "__CONFIG_DIR__";
    $this->{ECS_DEBUG}         = "0";
    $this->{NODE_TBL}          = "node_tbl.dat";
    $this->{NODE_TBL_LCK}      = "node_tbl.lock";
    $this->{T_ADM_DELAY}       = "0";
    $this->{T_ADM_REMIND}      = "86400";
    $this->{T_MSG_PROC}        = "3600";
    $this->{T_RESEND_DELAY}    = "14400";
    $this->{LOG_LEVEL}         = 1;
    $this->{MAIL_LEVEL}        = 2;
    $this->{MSG_PART_SIZE_DFLT} = "1073741824";
    $this->{SMTP_HOST}         = "smtp";
    $this->{SMTP_TIMEOUT}      = "60";
    $this->{SMTP_DEBUG}        = "0";
    $this->{SMTP_USE_SSL}      = "NO";
    $this->{SMTP_USE_STARTTLS} = "NO";
    $this->{INBOX_PROTOCOL}    = "POP3";
    $this->{INBOX_HOST}        = "mail";
    $this->{INBOX_FOLDER}      = "INBOX";
    $this->{INBOX_TIMEOUT}     = "60";
    $this->{INBOX_DEBUG}       = "0";
    $this->{INBOX_USE_SSL}     = "NO";
    $this->{INBOX_USE_STARTTLS} = "NO";
    $this->{INBOX_MAX_MSG_SIZE} = "1048576";
    $this->{OPENPGP_CMD_ENCRYPT} = '/usr/local/bin/gpg --armor --batch ' .
        '--charset ISO-8859-1 --force-mdc --logger-fd 1 --openpgp ' .
        '--output __OUTPUT__ --pinentry-mode loopback --passphrase-fd 0 ' .
        '--quiet --recipient __RECIPIENT__ --recipient __SELF__ --yes ' .
        '--sign --local-user __SELF__ --encrypt __INPUT__';
    $this->{OPENPGP_CMD_DECRYPT} = '/usr/local/bin/gpg --batch ' .
        '--charset ISO-8859-1 --logger-fd 1 --openpgp --output __OUTPUT__ ' .
        '--pinentry-mode loopback --passphrase-fd 0 --quiet --yes ' .
        '--decrypt __INPUT__';
    $this->{PGP2_CMD_ENCRYPT} = '/usr/local/bin/pgp +batchmode +verbose=0 ' .
        '+force +CharSet=latin1 +ArmorLines=0 -o __OUTPUT__ ' .
        '-u __SELF__ -eats __INPUT__ __RECIPIENT__ __SELF__';
    $this->{PGP2_CMD_DECRYPT} = '/usr/local/bin/pgp +batchmode +verbose=0 ' .
        '+force +CharSet=latin1 -o __OUTPUT__ __INPUT__';
    $this->{ENABLE_AMQP}       = "NO";
    $this->{AMQP_RECV_TIMEOUT} = 5;
    $this->{AMQP_RECV_TIMELIMIT} = 300;
    $this->{AMQP_SEND_TIMELIMIT} = 60;
    $this->{AMQP_DEBUG_LEVEL}  = 0;
    $this->{AMQP_CMD_SEND}     = 'ecs_amqp_send.py';
    $this->{AMQP_CMD_RECV}     = 'ecs_amqp_recv.py';
    $this->{INBOX_OAUTH_TOKEN_CMD_TIMELIMIT} = "60";
    $this->{INBOX_OAUTH_SASL_MECHANISM} = "XOAUTH2 OAUTHBEARER";
    $this->{SMTP_OAUTH_TOKEN_CMD_TIMELIMIT} = "60";
    $this->{SMTP_OAUTH_SASL_MECHANISM} = "XOAUTH2 OAUTHBEARER";
}

# ----------------------------------------------------------------------
# Do a few sanity checks on the configuration data.
# Returns empty string if successful or error message if error encountered.
sub _validate_config
{
    my $this = shift;
    my @errors = ();
    my @required_attrlist = qw(
        MSG_PROC MAIL_MRK THIS_NODE T_CHK T_SCN ERR_FILE LOG_FILE ADM_ADDR
        M_MSG_PROC BCK_DIR ACK_THRES
        ECS_BIN_DIR ECS_DAT_DIR ECS_DEBUG
        NODE_TBL NODE_TBL_LCK T_ADM_REMIND T_MSG_PROC
        SMTP_HOST SMTP_DOMAIN SMTP_TIMEOUT SMTP_DEBUG SMTP_FROM
        INBOX_PROTOCOL INBOX_HOST INBOX_TIMEOUT INBOX_DEBUG
        INBOX_MAX_MSG_SIZE
        MSG_PART_SIZE_DFLT
    );

    # check for required values that are undefined
    for my $attr (@required_attrlist)
    {
        push(@errors, "$attr not defined.")
            unless exists($this->{$attr});
    }

    # validate INBOX_PROTOCOL

    # username/password not needed for DIRECTORY inbox
    if($this->{INBOX_PROTOCOL} !~ /DIRECTORY/i and not exists($this->{INBOX_OAUTH_TOKEN_CMD}))
    {
        for my $attr (qw( INBOX_USERNAME INBOX_PASSWORD))
        {
            push(@errors, "$attr not defined.")
                unless exists($this->{$attr});
        }
    }

    if(exists $this->{INBOX_OAUTH_TOKEN_CMD}) {
        for my $attr (qw(INBOX_USERNAME
                         INBOX_OAUTH_TOKEN_CMD_TIMELIMIT
                         INBOX_OAUTH_SASL_MECHANISM))
        {
            push(@errors, "$attr not defined.")
                unless exists($this->{$attr});
        }
    }

    if($this->{INBOX_PROTOCOL} =~ /IMAP/i)
    {
        $this->{INBOX_PROTOCOL} = 'IMAP';  # force uppercase
        push(@errors,
            "INBOX_FOLDER not defined, but is required for IMAP protocol.")
            unless defined($this->{INBOX_FOLDER});
    }
    elsif($this->{INBOX_PROTOCOL} =~ /POP3/i)
    {
        $this->{INBOX_PROTOCOL} = 'POP3';  # force uppercase
    }
    elsif($this->{INBOX_PROTOCOL} =~ /DIRECTORY/i)
    {
        $this->{INBOX_PROTOCOL} = 'DIRECTORY';  # force uppercase
        push(@errors, "INBOX_DIRECTORY not defined, but is required for " .
            "DIRECTORY protocol.")
            unless defined($this->{INBOX_DIRECTORY});
    }
    elsif($this->{INBOX_PROTOCOL} =~ /NONE/i)
    {
        $this->{INBOX_PROTOCOL} = 'NONE';  # force uppercase
    }
    else
    {
        push(@errors,
            "Unrecognized INBOX_PROTOCOL:  $this->{INBOX_PROTOCOL}");
    }

    if(exists $this->{SMTP_OAUTH_TOKEN_CMD}) {
        for my $attr (qw(SMTP_USERNAME
                         SMTP_OAUTH_TOKEN_CMD_TIMELIMIT
                         SMTP_OAUTH_SASL_MECHANISM))
        {
            push(@errors, "$attr not defined.")
                unless exists($this->{$attr});
        }
    }

    if(is_yes($this->{ENABLE_AMQP}))
    {
        # sanity checks on AMQP configuration
        for my $attr (qw(AMQP_ADDR_META AMQP_ADDR_MSG AMQP_BROKER_URL
                         AMQP_CMD_SEND AMQP_CMD_RECV AMQP_DEBUG_LEVEL
                         AMQP_RECV_TIMEOUT AMQP_RECV_TIMELIMIT
                         AMQP_SEND_TIMELIMIT))
        {
            push(@errors, "$attr not defined, but is required for AMQP " .
                 "messaging.")
                unless exists($this->{$attr});
        }
    }

    # check whether an encryption method is configured
    if(!exists($this->{GPG_HOMEDIR}) && !exists($this->{PGP_HOMEDIR}))
    {
        push(@errors, "No encryption method configured.  Need to " .
             "configure either GPG_HOMEDIR or PGP_HOMEDIR, etc.");
    }

    # check OpenPGP encryption setup
    if(exists($this->{GPG_HOMEDIR}))
    {
        for my $attr (qw(GPG_HOMEDIR GPG_KEYID GPG_PASSPHRASE
                         OPENPGP_CMD_ENCRYPT OPENPGP_CMD_DECRYPT))
        {
            push(@errors, "$attr not defined, but is required for OpenPGP " .
                 "encryption setup (GPG_HOMEDIR = " .
                 $this->{GPG_HOMEDIR} . ").")
                unless exists($this->{$attr});
        }
    }

    # check PGP encryption setup
    if(exists($this->{PGP_HOMEDIR}))
    {
        for my $attr (qw(PGP_HOMEDIR PGP_KEYID PGP_PASSPHRASE
                         PGP2_CMD_ENCRYPT PGP2_CMD_DECRYPT))
        {
            push(@errors, "$attr not defined, but is required for PGP2 " .
                 "encryption setup (PGP_HOMEDIR = " .
                 $this->{PGP_HOMEDIR} . ").")
                unless exists($this->{$attr});
        }
    }

    # validate T_CHK
    if($this->{T_CHK} <= 0)
    {
        push(@errors,
            "T_CHK ($this->{T_CHK}) is required to be greater than zero.");
    }

    # validate T_SCN
    if($this->{T_SCN} <= 0)
    {
        push(@errors,
            "T_SCN ($this->{T_SCN}) is required to be greater than zero.");
    }

    # validate T_ADM_REMIND
    if($this->{T_ADM_REMIND} <= 0)
    {
        push(@errors,
             "T_ADM_REMIND ($this->{T_ADM_REMIND}) is required " .
             "to be greater than zero.");
    }

    # validate T_MSG_PROC
    if($this->{T_MSG_PROC} <= 0)
    {
        push(@errors,
             "T_MSG_PROC ($this->{T_MSG_PROC}) is required " .
             "to be greater than zero.");
    }

    # validate YES/NO values
    for my $name (qw(ALWAYS_ACK INBOX_USE_SSL INBOX_USE_STARTTLS SMTP_USE_SSL SMTP_USE_STARTTLS))
    {
        if(exists $this->{$name} and not is_yes($this->{$name})
            and not is_no($this->{$name}))
        {
            push(@errors, "Unrecognized $name (YES/NO) value:  " .
                $this->{$name});
        }
    }

    if(is_yes($this->{INBOX_USE_SSL})
        and is_yes($this->{INBOX_USE_STARTTLS}))
    {
        push(@errors, "INBOX_USE_SSL and INBOX_USE_STARTTLS " .
            "are both selected, but they are mutually exclusive.");
    }

    if(exists $this->{INBOX_OAUTH_TOKEN_CMD}
        and not is_yes($this->{INBOX_USE_SSL})
        and not is_yes($this->{INBOX_USE_STARTTLS}))
    {
        push(@errors, "INBOX OAuth 2.0 authentication requires SSL/TLS " .
            "(INBOX_USE_SSL or INBOX_USE_STARTTLS).");
    }

    if(is_yes($this->{SMTP_USE_SSL})
        and is_yes($this->{SMTP_USE_STARTTLS}))
    {
        push(@errors, "SMTP_USE_SSL and SMTP_USE_STARTTLS " .
            "are both selected, but they are mutually exclusive.");
    }

    if(exists $this->{SMTP_OAUTH_TOKEN_CMD}
        and not is_yes($this->{SMTP_USE_SSL})
        and not is_yes($this->{SMTP_USE_STARTTLS}))
    {
        push(@errors, "SMTP OAuth 2.0 authentication requires SSL/TLS " .
            "(SMTP_USE_SSL or SMTP_USE_STARTTLS).");
    }

    # check whether directories exist
    my @dirs = qw(ECS_BIN_DIR ECS_DAT_DIR ECS_TMP_DIR ECS_MBX_DIR
                  ECS_MBX_IN_DIR ECS_MBX_IN_FML_DIR ECS_MBX_OUT_DIR
                  ECS_MBX_TRASH_DIR ECS_MBX_STORE_DIR GPG_HOMEDIR
                  PGP_HOMEDIR);
    push(@dirs, 'BCK_DIR') if($this->{BCK_DIR} ne 'NONE');
    push(@dirs, 'ECS_DRP_DIR')
       if( ! defined($this->{ECS_TO_DIR})
           || $this->{ECS_TO_DIR} eq '');
    push(@dirs, 'ECS_MBX_AMQP_STAGING_DIR') if is_yes($this->{ENABLE_AMQP});
    for my $dir (@dirs)
    {
        if(exists $this->{$dir} and not -d $this->{$dir})
        {
            push(@errors,
                 "$dir ($this->{$dir}) directory not found.");
        }
    }

    # return error messages, if any
    if($#errors >= 0)
    {
        push(@errors,
            "Error(s) detected in configuration file $this->{CFG_FILE}");
        push(@errors, "Fatal configuration error(s) encountered.\n");
        return "\n" . join("\n", @errors);
    }
    return '';
}

1;

__DATA__