AuthDBI.pm   [plain text]

package Apache::AuthDBI;

$Apache::AuthDBI::VERSION = '0.93';

# 1: report about cache miss
# 2: full debug output
$Apache::AuthDBI::DEBUG = 0;

use constant MP2 => $mod_perl::VERSION >= 1.99;
 
BEGIN {
  my @constants = qw( OK AUTH_REQUIRED FORBIDDEN DECLINED SERVER_ERROR );
  if (MP2) {
    require Apache::Const;
    import Apache::Const @constants;
  }
  else {
    require Apache::Constants;
    import Apache::Constants @constants;
  }
}

use DBI ();
use strict;

sub push_handlers {
  if ( MP2 ) {
    Apache->server->push_handlers(@_);
  }
  else {
    Apache->push_handlers(@_);
  }
}


# configuration attributes, defaults will be overwritten with values from .htaccess.

my %Config = (
    'Auth_DBI_data_source'      => '',
    'Auth_DBI_username'         => '',
    'Auth_DBI_password'         => '',
    'Auth_DBI_pwd_table'        => '',
    'Auth_DBI_uid_field'        => '',
    'Auth_DBI_pwd_field'        => '',
    'Auth_DBI_pwd_whereclause'  => '',
    'Auth_DBI_grp_table'        => '',
    'Auth_DBI_grp_field'        => '',
    'Auth_DBI_grp_whereclause'  => '',
    'Auth_DBI_log_field'        => '',
    'Auth_DBI_log_string'       => '',
    'Auth_DBI_authoritative'    => 'on',
    'Auth_DBI_nopasswd'         => 'off',
    'Auth_DBI_encrypted'        => 'on',
    'Auth_DBI_encryption_salt'  => 'password',
    'Auth_DBI_uidcasesensitive' => 'on',
    'Auth_DBI_pwdcasesensitive' => 'on',
    'Auth_DBI_placeholder'      => 'off',
);

# stores the configuration of current URL.
# initialized  during authentication, eventually re-used for authorization.
my $Attr = { };


# global cache: all records are put into one string.
# record separator is a newline. Field separator is $;.
# every record is a list of id, time of last access, password, groups (authorization only).
# the id is a comma separated list of user_id, data_source, pwd_table, uid_field.
# the first record is a timestamp, which indicates the last run of the CleanupHandler followed by the child counter.

my $Cache = time . "$;0\n";

# unique id which serves as key in $Cache.
# the id is generated during authentication and re-used for authorization.
my $ID;


# minimum lifetimes of cache entries in seconds.
# setting the CacheTime to 0 will not use the cache at all.

my $CacheTime = 0;

# supposed to be called in a startup script.
# sets CacheTime to a user defined value.

sub setCacheTime {
    my $class      = shift;
    my $cache_time = shift;
    # sanity check
    $CacheTime = $cache_time if ($cache_time =~ /\d+/);
}


# minimum time interval in seconds between two runs of the PerlCleanupHandler.
# setting CleanupTime to 0 will run the PerlCleanupHandler after every request.
# setting CleanupTime to a negative value will disable the PerlCleanupHandler.

my $CleanupTime = -1;

# supposed to be called in a startup script.
# sets CleanupTime to a user defined value.

sub setCleanupTime {
    my $class        = shift;
    my $cleanup_time = shift;
    # sanity check
    $CleanupTime = $cleanup_time if ($cleanup_time =~ /\-*\d+/);
}


# optionally the string with the global cache can be stored in a shared memory segment.
# the segment will be created from the first child and it will be destroyed if the last child exits.
# the reason for not handling everything in the main server is simply, that there is no way to setup 
# an ExitHandler which runs in the main server and which would remove the shared memory and the semaphore.
# hence we have to keep track about the number of children, so that the last one can do all the cleanup.
# creating the shared memory in the first child also has the advantage, that we don't have to cope
# with changing the ownership.
# if a shm-function fails, the global cache will automatically fall back to one string per process.

my $SHMKEY  =     0; # unique key for shared memory segment and semaphore set
my $SEMID   =     0; # id of semaphore set
my $SHMID   =     0; # id of shared memory segment
my $SHMSIZE = 50000; # default size of shared memory segment

# shortcuts for semaphores
my $obtain_lock  = pack("sss", 0,  0, 0) . pack("sss", 0, 1, 0);
my $release_lock = pack("sss", 0, -1, 0);

# supposed to be called in a startup script.
# sets SHMSIZE to a user defined value and initializes the unique key, used for the shared memory segment and for the semaphore set.
# creates a PerlChildInitHandler which creates the shared memory segment and the semaphore set.
# creates a PerlChildExitHandler which removes the shared memory segment and the semaphore set upon server shutdown.
# keep in mind, that this routine runs only once, when the main server starts up.

sub initIPC {
    my $class   = shift;
    my $shmsize = shift;
    require IPC::SysV;

    # make sure, this method is called only once
    return if $SHMKEY;

    # ensure minimum size of shared memory segment
    $SHMSIZE = $shmsize if $shmsize >= 500;

    # generate unique key based on path of AuthDBI.pm
    foreach my $file (keys %INC) {
        if ($file eq 'Apache/AuthDBI.pm') {
            $SHMKEY = IPC::SysV::ftok($INC{$file}, 1);
            last;
        }
    }

    # provide a handler which initializes the shared memory segment (first child)
    # or which increments the child counter. 
    push_handlers( PerlChildInitHandler => \&childinit);

    # provide a handler which decrements the child count or which destroys the shared memory 
    # segment upon server shutdown, which is defined by the exit of the last child.
    push_handlers( PerlChildExitHandler => \&childexit);
}


# authentication handler

sub authen {

    my ($r) = @_;
    my ($key, $val, $dbh);

    my $prefix = "$$ Apache::AuthDBI::authen";

    if ($Apache::AuthDBI::DEBUG > 1) {
        my ($type) = '';
        $type .= 'initial ' if $r->is_initial_req;
        $type .= 'main'     if $r->is_main;
        print STDERR "==========\n$prefix request type = >$type< \n";
    }

    return OK unless $r->is_initial_req; # only the first internal request

    print STDERR "REQUEST:\n", $r->as_string if $Apache::AuthDBI::DEBUG > 1;

    # here the dialog pops up and asks you for username and password
    my($res, $passwd_sent) = $r->get_basic_auth_pw;
    print STDERR "$prefix get_basic_auth_pw: res = >$res<, password sent = >$passwd_sent<\n" if $Apache::AuthDBI::DEBUG > 1;
    return $res if $res; # e.g. HTTP_UNAUTHORIZED

    # get username
    my ($user_sent) = $r->user;
    print STDERR "$prefix user sent = >$user_sent<\n" if $Apache::AuthDBI::DEBUG > 1;

    # do we use shared memory for the global cache ?
    print STDERR "$prefix cache in shared memory, shmid $SHMID, shmsize $SHMSIZE, semid $SEMID \n" if ($SHMID and $Apache::AuthDBI::DEBUG > 1);

    # get configuration
    while(($key, $val) = each %Config) {
        $val = $r->dir_config($key) || $val;
        $key =~ s/^Auth_DBI_//;
        $Attr->{$key} = $val;
        printf STDERR "$prefix Config{ %-16s } = %s\n", $key, $val if $Apache::AuthDBI::DEBUG > 1;
    }

    # parse connect attributes, which may be tilde separated lists
    my @data_sources = split(/~/, $Attr->{data_source});
    my @usernames    = split(/~/, $Attr->{username});
    my @passwords    = split(/~/, $Attr->{password});
    $data_sources[0] = '' unless $data_sources[0]; # use ENV{DBI_DSN} if not defined

    # obtain the id for the cache
    my $data_src = $Attr->{data_source};
    $data_src =~ s/\(.+\)//go; # remove any embedded attributes, because of trouble with regexps
    $ID = join ',', $user_sent, $data_src, $Attr->{pwd_table}, $Attr->{uid_field};

    # if not configured decline
    unless ($Attr->{pwd_table} && $Attr->{uid_field} && $Attr->{pwd_field}) {
        printf STDERR "$prefix not configured, return DECLINED\n" if $Apache::AuthDBI::DEBUG > 1;
        return DECLINED;
    }

    # do we want Windows-like case-insensitivity?
    $user_sent   = lc($user_sent)   if $Attr->{uidcasesensitive} eq "off";
    $passwd_sent = lc($passwd_sent) if $Attr->{pwdcasesensitive} eq "off";

    # check whether the user is cached but consider that the password possibly has changed
    my $passwd = '';
    my $salt   = '';
    if ($CacheTime) { # do we use the cache ?
        if ($SHMID) { # do we keep the cache in shared memory ?
            semop($SEMID, $obtain_lock) or print STDERR "$prefix semop failed \n";
            shmread($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmread failed \n";
            substr($Cache, index($Cache, "\0")) = '';
            semop($SEMID, $release_lock) or print STDERR "$prefix semop failed \n";
        }
        # find id in cache
        my ($last_access, $passwd_cached, $groups_cached);
        if ($Cache =~ /$ID$;(\d+)$;(.+)$;(.*)\n/) {
            $last_access   = $1;
            $passwd_cached = $2;
            $groups_cached = $3;
            printf STDERR "$prefix cache: found >$ID< >$last_access< >$passwd_cached< \n" if $Apache::AuthDBI::DEBUG > 1;
            $salt = $Attr->{encryption_salt} eq 'userid' ? $user_sent : $passwd_cached;
            my $passwd_to_check = $Attr->{encrypted} eq 'on' ? crypt($passwd_sent, $salt) : $passwd_sent; 
            # match cached password with password sent 
            $passwd = $passwd_cached if $passwd_to_check eq $passwd_cached;
        }
    }

    if ($passwd) { # found in cache
        printf STDERR "$prefix passwd found in cache \n" if $Apache::AuthDBI::DEBUG > 1;
    } else { # password not cached or changed
        printf STDERR "$prefix passwd not found in cache \n" if $Apache::AuthDBI::DEBUG;
        # connect to database, use all data_sources until the connect succeeds
        my $j;
        for ($j = 0; $j <= $#data_sources; $j++) {
            last if ($dbh = DBI->connect($data_sources[$j], $usernames[$j], $passwords[$j]));
        }
        unless ($dbh) {
            $r->log_reason("$prefix db connect error with data_source >$Attr->{data_source}<: $DBI::errstr", $r->uri);
            return SERVER_ERROR;
        }

        # generate statement
        my $user_sent_quoted = $dbh->quote($user_sent);
        my $select    = "SELECT $Attr->{pwd_field}";
        my $from      = "FROM $Attr->{pwd_table}";
        my $where     = ($Attr->{uidcasesensitive} eq "off") ? "WHERE lower($Attr->{uid_field}) =" : "WHERE $Attr->{uid_field} =";
        my $compare   = ($Attr->{placeholder}      eq "on")  ? "?" : "$user_sent_quoted";
        my $statement = "$select $from $where $compare";
        $statement   .= " AND $Attr->{pwd_whereclause}" if $Attr->{pwd_whereclause};
        print STDERR "$prefix statement: $statement\n" if $Apache::AuthDBI::DEBUG > 1;

        # prepare statement
        my $sth;
        unless ($sth = $dbh->prepare($statement)) {
            $r->log_reason("$prefix can not prepare statement: $DBI::errstr", $r->uri);
            $dbh->disconnect;
            return SERVER_ERROR;
        }

        # execute statement
        my $rv;
        unless ($rv = ($Attr->{placeholder} eq "on") ? $sth->execute($user_sent) : $sth->execute) {
            $r->log_reason("$prefix can not execute statement: $DBI::errstr", $r->uri);
            $dbh->disconnect;
            return SERVER_ERROR;
        }

        # fetch result
        while ($_ = $sth->fetchrow_array) {
            # strip trailing blanks for fixed-length data-type
            $_ =~ s/ +$// if $_;
            # consider the case with many users sharing the same userid
	    $passwd .= "$_$;";
        }

        chop  $passwd if $passwd;
        undef $passwd if 0 == $sth->rows; # so we can distinguish later on between no password and empty password

        if ($sth->err) {
            $dbh->disconnect;
            return SERVER_ERROR;
        }
        $sth->finish;

        # re-use dbh for logging option below
        $dbh->disconnect unless ($Attr->{log_field} && $Attr->{log_string});
    }

    $r->subprocess_env(REMOTE_PASSWORDS => $passwd);
    print STDERR "$prefix passwd = >$passwd<\n" if $Apache::AuthDBI::DEBUG > 1;

    # check if password is needed
    if (!defined($passwd)) { # not found in database
        # if authoritative insist that user is in database
        if ($Attr->{authoritative} eq 'on') {
            $r->log_reason("$prefix password for user $user_sent not found", $r->uri);
            $r->note_basic_auth_failure;
            return AUTH_REQUIRED;
        } else {
            # else pass control to the next authentication module
            return DECLINED;
        }
    }

    # allow any password if nopasswd = on and the retrieved password is empty
    if ($Attr->{nopasswd} eq 'on' && !$passwd) {
        return OK;
    }

    # if nopasswd is off, reject user
    unless ($passwd_sent && $passwd) {
        $r->log_reason("$prefix user $user_sent: empty password(s) rejected", $r->uri);
        $r->note_basic_auth_failure;
        return AUTH_REQUIRED;
    }

    # compare passwords
    my $found = 0;
    my $password;
    foreach $password (split(/$;/, $passwd)) {
        # compare the two passwords possibly crypting the password if needed
        $salt = $Attr->{encryption_salt} eq 'userid' ? $user_sent : $password;
        my $passwd_to_check = $Attr->{encrypted} eq 'on' ? crypt($passwd_sent, $password) : $passwd_sent; 
        if ($passwd_to_check eq $password) {
            $found = 1;
            $r->subprocess_env(REMOTE_PASSWORD => $password);
            print STDERR "$prefix user $user_sent: password match for >$password< \n" if $Apache::AuthDBI::DEBUG > 1;
            # update timestamp and cache userid/password if CacheTime is configured
            if ($CacheTime) { # do we use the cache ?
                if ($SHMID) { # do we keep the cache in shared memory ?
                    semop($SEMID, $obtain_lock) or print STDERR "$prefix semop failed \n";
                    shmread($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmread failed \n";
                    substr($Cache, index($Cache, "\0")) = '';
                }
                # update timestamp and password or append new record
                my $now = time;
                if (!($Cache =~ s/$ID$;\d+$;.*$;(.*)\n/$ID$;$now$;$password$;$1\n/)) {
		    $Cache .= "$ID$;$now$;$password$;\n";
                } else {
                }
                if ($SHMID) { # write cache to shared memory
                    shmwrite($SHMID, $Cache, 0, $SHMSIZE)  or printf STDERR "$prefix shmwrite failed \n";
                    semop($SEMID, $release_lock) or print STDERR "$prefix semop failed \n";
                }
            }
            last;
        }
    }
    unless ($found) {
        $r->log_reason("$prefix user $user_sent: password mismatch", $r->uri);
        $r->note_basic_auth_failure;
        return AUTH_REQUIRED;
    }

    # logging option
    if ($Attr->{log_field} && $Attr->{log_string}) {
        if (!$dbh) { # connect to database if not already done
            my ($j, $connect);
            for ($j = 0; $j <= $#data_sources; $j++) {
                if ($dbh = DBI->connect($data_sources[$j], $usernames[$j], $passwords[$j])) {
                    $connect = 1;
                    last;
                }
            }
            unless ($connect) {
                $r->log_reason("$prefix db connect error with $Attr->{data_source}", $r->uri);
                return SERVER_ERROR;
            }
        }
        my $user_sent_quoted = $dbh->quote($user_sent);
        my $statement = "UPDATE $Attr->{pwd_table} SET $Attr->{log_field} = $Attr->{log_string} WHERE $Attr->{uid_field}=$user_sent_quoted";
        print STDERR "$prefix statement: $statement\n" if $Apache::AuthDBI::DEBUG > 1;
        unless ($dbh->do($statement)) {
            $r->log_reason("$prefix can not do statement: $DBI::errstr", $r->uri);
            $dbh->disconnect;
            return SERVER_ERROR;
        }
        $dbh->disconnect;
    }

    # Unless the cache or the CleanupHandler is disabled, the CleanupHandler is initiated 
    # if the last run was more than $CleanupTime seconds before. 
    # Note, that it runs after the request, hence it cleans also the authorization entries 
    if ($CacheTime and $CleanupTime >= 0) {
        my $diff = time - substr($Cache, 0, index($Cache, "$;"));
        print STDERR "$prefix secs since last CleanupHandler: $diff, CleanupTime: $CleanupTime \n" if $Apache::AuthDBI::DEBUG > 1;
        if ($diff > $CleanupTime) {
            print STDERR "$prefix push PerlCleanupHandler \n" if $Apache::AuthDBI::DEBUG > 1;
            push_handlers( PerlCleanupHandler => \&cleanup);
        }
    }

    printf STDERR "$prefix return OK\n" if $Apache::AuthDBI::DEBUG > 1;
    return OK;
}


# authorization handler, it is called immediately after the authentication

sub authz {

    my ($r) = @_;
    my ($key, $val, $dbh);

    my ($prefix) = "$$ Apache::AuthDBI::authz ";

    if ($Apache::AuthDBI::DEBUG > 1) {
        my ($type) = '';
        $type .= 'initial ' if $r->is_initial_req;
        $type .= 'main'     if $r->is_main;
        print STDERR "==========\n$prefix request type = >$type< \n";
    }

    return OK unless $r->is_initial_req; # only the first internal request

    my ($user_result)  = DECLINED;
    my ($group_result) = DECLINED;

    # get username
    my ($user_sent) = $r->user;
    print STDERR "$prefix user sent = >$user_sent<\n" if $Apache::AuthDBI::DEBUG > 1 ;

    # here we could read the configuration, but we re-use the configuration from the authentication

    # parse connect attributes, which may be tilde separated lists
    my @data_sources = split(/~/, $Attr->{data_source});
    my @usernames    = split(/~/, $Attr->{username});
    my @passwords    = split(/~/, $Attr->{password});
    $data_sources[0] = '' unless $data_sources[0]; # use ENV{DBI_DSN} if not defined

    # if not configured decline
    unless ($Attr->{pwd_table} && $Attr->{uid_field} && $Attr->{grp_field}) {
        printf STDERR "$prefix not configured, return DECLINED\n" if $Apache::AuthDBI::DEBUG > 1;
        return DECLINED;
    }

    # do we want Windows-like case-insensitivity?
    $user_sent = lc($user_sent) if $Attr->{uidcasesensitive} eq "off";

    # select code to return if authorization is denied:
    my $authz_denied= $Attr->{expeditive} eq 'on' ? FORBIDDEN : AUTH_REQUIRED;

    # check if requirements exists
    my ($ary_ref) = $r->requires;
    unless ($ary_ref) {
        if ($Attr->{authoritative} eq 'on') {
            $r->log_reason("user $user_sent denied, no access rules specified (DBI-Authoritative)", $r->uri);
            $r->note_basic_auth_failure if $authz_denied == AUTH_REQUIRED;
            return $authz_denied;
        }
        printf STDERR "$prefix no requirements and not authoritative, return DECLINED\n" if $Apache::AuthDBI::DEBUG > 1;
        return DECLINED;
    }

    # iterate over all requirement directives and store them according to their type (valid-user, user, group)
    my($hash_ref, $valid_user, $user_requirements, $group_requirements);
    foreach $hash_ref (@$ary_ref) {
        while (($key,$val) = each %$hash_ref) {
            last if $key eq 'requirement';
        }
        $val =~ s/^\s*require\s+//;
        # handle different requirement-types
        if ($val =~ /valid-user/) {
            $valid_user = 1;
        } elsif ($val =~ s/^user\s+//go) {
            $user_requirements .= " $val";
        } elsif ($val =~ s/^group\s+//go) {
            $group_requirements .= " $val";
        }
    }
    $user_requirements  =~ s/^ //go;
    $group_requirements =~ s/^ //go;
    print STDERR "$prefix requirements: valid-user=>$valid_user< user=>$user_requirements< group=>$group_requirements< \n"  if $Apache::AuthDBI::DEBUG > 1;

    # check for valid-user
    if ($valid_user) {
        $user_result = OK;
        print STDERR "$prefix user_result = OK: valid-user\n" if $Apache::AuthDBI::DEBUG > 1;
    }

    # check for users
    if ($user_result != OK && $user_requirements) {
        $user_result = AUTH_REQUIRED;
        my $user_required;
        foreach $user_required (split /\s+/, $user_requirements) {
            if ($user_required eq $user_sent) {
                print STDERR "$prefix user_result = OK for $user_required \n" if $Apache::AuthDBI::DEBUG > 1;
                $user_result = OK;
                last;
           }
        }
    }

    # check for groups
    if ($user_result != OK && $group_requirements) {
        $group_result = AUTH_REQUIRED;
        my ($group, $group_required);

        # check whether the user is cached but consider that the group possibly has changed
        my $groups = '';
        if ($CacheTime) { # do we use the cache ?
            # we need to get the cached groups for the current id, which has been read already 
            # during authentication, so we do not read the Cache from shared memory again
            my ($last_access, $passwd_cached, $groups_cached);
            if ($Cache =~ /$ID$;(\d+)$;(.*)$;(.+)\n/) {
                $last_access   = $1;
                $passwd_cached = $2;
                $groups_cached = $3;
                printf STDERR "$prefix cache: found >$ID< >$last_access< >$groups_cached< \n" if $Apache::AuthDBI::DEBUG > 1;
                REQUIRE_1: foreach $group_required (split /\s+/, $group_requirements) {
                    foreach $group (split(/,/, $groups_cached)) {
                        if ($group_required eq $group) {
                            $groups = $groups_cached;
                            last REQUIRE_1;
		        }
                    }
                }
            }
        }

        if ($groups) { # found in cache
            printf STDERR "$prefix groups found in cache \n" if $Apache::AuthDBI::DEBUG > 1;
        } else { # groups not cached or changed
            printf STDERR "$prefix groups not found in cache \n" if $Apache::AuthDBI::DEBUG;

            # connect to database, use all data_sources until the connect succeeds
            my ($j, $connect);
            for ($j = 0; $j <= $#data_sources; $j++) {
                if ($dbh = DBI->connect($data_sources[$j], $usernames[$j], $passwords[$j])) {
                    $connect = 1;
                    last;
                }
            }
            unless ($connect) {
                $r->log_reason("$prefix db connect error with $Attr->{data_source}", $r->uri);
                return SERVER_ERROR;
            }

            # generate statement
            my $user_sent_quoted = $dbh->quote($user_sent);
            my $select    = "SELECT $Attr->{grp_field}";
            my $from      = ($Attr->{grp_table}) ? "FROM $Attr->{grp_table}" : "FROM $Attr->{pwd_table}";
            my $where     = ($Attr->{uidcasesensitive} eq "off") ? "WHERE lower($Attr->{uid_field}) =" : "WHERE $Attr->{uid_field} =";
            my $compare   = ($Attr->{placeholder}      eq "on")  ? "?" : "$user_sent_quoted";
            my $statement = "$select $from $where $compare";
            $statement   .= " AND $Attr->{grp_whereclause}" if ($Attr->{grp_whereclause});
            print STDERR "$prefix statement: $statement\n" if $Apache::AuthDBI::DEBUG > 1;

            # prepare statement
            my $sth;
            unless ($sth = $dbh->prepare($statement)) {
                $r->log_reason("can not prepare statement: $DBI::errstr", $r->uri);
                $dbh->disconnect;
                return SERVER_ERROR;
            }

            # execute statement
            my $rv;
            unless ($rv = ($Attr->{placeholder} eq "on") ? $sth->execute($user_sent) : $sth->execute) {
                $r->log_reason("can not execute statement: $DBI::errstr", $r->uri);
                $dbh->disconnect;
                return SERVER_ERROR;
            }

            # fetch result and build a group-list
            my $group;
            while ( $group = $sth->fetchrow_array ) {
                # strip trailing blanks for fixed-length data-type
                $group =~ s/ +$//;
                $groups .= "$group,";
            }
            chop $groups if $groups;

            $sth->finish;
            $dbh->disconnect;
        }

        $r->subprocess_env(REMOTE_GROUPS => $groups);
        print STDERR "$prefix groups = >$groups<\n" if $Apache::AuthDBI::DEBUG > 1;

        # skip through the required groups until the first matches
        REQUIRE_2: foreach $group_required (split /\s+/, $group_requirements) {
            foreach $group (split(/,/, $groups)) {
                # check group
                if ($group_required eq $group) {
                    $group_result = OK;
                    $r->subprocess_env(REMOTE_GROUP => $group);
                    print STDERR "$prefix user $user_sent: group_result = OK for >$group< \n" if $Apache::AuthDBI::DEBUG > 1;
                    # update timestamp and cache userid/groups if CacheTime is configured
                    if ($CacheTime) { # do we use the cache ?
                        if ($SHMID) { # do we keep the cache in shared memory ?
                            semop($SEMID, $obtain_lock) or print STDERR "$prefix semop failed \n";
                            shmread($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmread failed \n";
                            substr($Cache, index($Cache, "\0")) = '';
                        }
                        # update timestamp and groups
                        my $now = time;
                        # entry must exists from authentication
	        	$Cache =~ s/$ID$;\d+$;(.*)$;.*\n/$ID$;$now$;$1$;$groups\n/;
                        if ($SHMID) { # write cache to shared memory
                            shmwrite($SHMID, $Cache, 0, $SHMSIZE)  or printf STDERR "$prefix shmwrite failed \n";
                            semop($SEMID, $release_lock) or print STDERR "$prefix semop failed \n";
                        }
                    }
                    last REQUIRE_2;
		}
            }
        }
    }

    # check the results of the requirement checks
    if ($Attr->{authoritative} eq 'on' && $user_result != OK && $group_result != OK) {
        my $reason;
        $reason .= " USER"  if $user_result  == AUTH_REQUIRED;
        $reason .= " GROUP" if $group_result == AUTH_REQUIRED;
        $r->log_reason("DBI-Authoritative: Access denied on $reason rule(s)", $r->uri);
        $r->note_basic_auth_failure if $authz_denied == AUTH_REQUIRED;
        return $authz_denied;
    }

    # return OK if authorization was successful
    if ($user_result == OK || $group_result == OK) {
        printf STDERR "$prefix return OK\n" if $Apache::AuthDBI::DEBUG > 1;
        return OK;
    }

    # otherwise fall through
    printf STDERR "$prefix fall through, return DECLINED\n" if $Apache::AuthDBI::DEBUG > 1;
    return DECLINED;
}


# The PerlChildInitHandler initializes the shared memory segment (first child)
# or increments the child counter. 
# Note: this handler runs in every child server, but not in the main server.

sub childinit {
    my $prefix = "$$ Apache::AuthDBI         PerlChildInitHandler";
    # create (or re-use existing) semaphore set

    $SEMID = semget($SHMKEY, 1,
		    IPC::SysV::IPC_CREAT() | IPC::SysV::S_IRUSR() | IPC::SysV::S_IWUSR());
    if (!defined($SEMID)) {
      print STDERR "$prefix semget failed \n";
      return;
    }
    # create (or re-use existing) shared memory segment
    $SHMID = shmget($SHMKEY, $SHMSIZE,
		    IPC::SysV::IPC_CREAT() | IPC::SysV::S_IRUSR() | IPC::SysV::S_IWUSR());
    if (!defined($SHMID)) {
      print STDERR "$prefix shmget failed \n";
      return;
    }
    # make ids accessible to other handlers
    $ENV{AUTH_SEMID} = $SEMID;
    $ENV{AUTH_SHMID} = $SHMID;
    # read shared memory, increment child count and write shared memory segment
    semop($SEMID, $obtain_lock) or print STDERR "$prefix semop failed \n";
    shmread($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmread failed \n";
    substr($Cache, index($Cache, "\0")) = '';
    my $child_count_new = 1;
    if ($Cache =~ /^(\d+)$;(\d+)\n/) { # segment already exists (eg start of additional server)
        my $time_stamp   = $1;
        my $child_count  = $2;
        $child_count_new = $child_count + 1;
        $Cache =~ s/^$time_stamp$;$child_count\n/$time_stamp$;$child_count_new\n/;
    } else { # first child => initialize segment
        $Cache = time . "$;$child_count_new\n";
    }
    print STDERR "$prefix child count = $child_count_new \n" if $Apache::AuthDBI::DEBUG > 1;
    shmwrite($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmwrite failed \n";
    semop($SEMID, $release_lock) or print STDERR "$prefix semop failed \n";
    1;
}


# The PerlChildExitHandler decrements the child count or destroys the shared memory 
# segment upon server shutdown, which is defined by the exit of the last child.
# Note: this handler runs in every child server, but not in the main server.

sub childexit {
    my $prefix = "$$ Apache::AuthDBI         PerlChildExitHandler";
    # read Cache from shared memory, decrement child count and exit or write Cache to shared memory
    semop($SEMID, $obtain_lock) or print STDERR "$prefix semop failed \n";
    shmread($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmread failed \n";
    substr($Cache, index($Cache, "\0")) = '';
    $Cache =~ /^(\d+)$;(\d+)\n/;
    my $time_stamp  = $1;
    my $child_count = $2;
    my $child_count_new = $child_count - 1;
    if ($child_count_new) {
        print STDERR "$prefix child count = $child_count \n" if $Apache::AuthDBI::DEBUG > 1;
        # write Cache into shared memory
        $Cache =~ s/^$time_stamp$;$child_count\n/$time_stamp$;$child_count_new\n/;
        shmwrite($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmwrite failed \n";
        semop($SEMID, $release_lock) or print STDERR "$prefix semop failed \n";
    } else { # last child
        # remove shared memory segment and semaphore set
        print STDERR "$prefix child count = $child_count, remove shared memory $SHMID and semaphore $SEMID \n" if $Apache::AuthDBI::DEBUG > 1;
        shmctl($SHMID,    IPC::SysV::IPC_RMID(), 0) or print STDERR "$prefix shmctl failed \n";
        semctl($SEMID, 0, IPC::SysV::IPC_RMID(), 0) or print STDERR "$prefix semctl failed \n";
    }
    1;
}


# The PerlCleanupHandler skips through the cache and deletes any outdated entry.
# Note: this handler runs after the response has been sent to the client.

sub cleanup {
    my $prefix = "$$ Apache::AuthDBI         PerlCleanupHandler";
    print STDERR "$prefix \n" if $Apache::AuthDBI::DEBUG > 1;
    my $now = time;
    if ($SHMID) { # do we keep the cache in shared memory ?
        semop($SEMID, $obtain_lock) or print STDERR "$prefix semop failed \n";
        shmread($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmread failed \n";
        substr($Cache, index($Cache, "\0")) = ''; 
    }
    my $newCache = "$now$;"; # initialize timestamp for CleanupHandler
    my ($time_stamp, $child_count);
    foreach my $record (split(/\n/, $Cache)) {
        if (!$time_stamp) { # first record: timestamp of CleanupHandler and child count
            ($time_stamp, $child_count) = split(/$;/, $record);
            $newCache .= "$child_count\n";
            next;
        }
        my ($id, $last_access, $passwd, $groups) = split(/$;/, $record);
        my $diff = $now - $last_access;
        if ($diff >= $CacheTime) {
            print STDERR "$prefix delete >$id<, last access $diff s before \n" if $Apache::AuthDBI::DEBUG > 1;
        } else {
            print STDERR "$prefix keep   >$id<, last access $diff s before \n" if $Apache::AuthDBI::DEBUG > 1;
            $newCache .= "$id$;$now$;$passwd$;$groups\n";
        }
    }
    $Cache = $newCache;
    if ($SHMID) { # write Cache to shared memory
        shmwrite($SHMID, $Cache, 0, $SHMSIZE) or printf STDERR "$prefix shmwrite failed \n";
        semop($SEMID, $release_lock) or print STDERR "$prefix semop failed \n";
    }
    1;
}


1;

__END__


=head1 NAME

Apache::AuthDBI - Authentication and Authorization via Perl's DBI


=head1 SYNOPSIS

 # Configuration in httpd.conf or startup.pl:

 PerlModule Apache::AuthDBI

 # Authentication and Authorization in .htaccess:

 AuthName DBI
 AuthType Basic

 PerlAuthenHandler Apache::AuthDBI::authen
 PerlAuthzHandler  Apache::AuthDBI::authz

 PerlSetVar Auth_DBI_data_source   dbi:driver:dsn
 PerlSetVar Auth_DBI_username      db_username
 PerlSetVar Auth_DBI_password      db_password
 #DBI->connect($data_source, $username, $password)

 PerlSetVar Auth_DBI_pwd_table     users
 PerlSetVar Auth_DBI_uid_field     username
 PerlSetVar Auth_DBI_pwd_field     password
 # authentication: SELECT pwd_field FROM pwd_table WHERE uid_field=$user
 PerlSetVar Auth_DBI_grp_field     groupname
 # authorization: SELECT grp_field FROM pwd_table WHERE uid_field=$user

 require valid-user
 require user   user_1  user_2 ...
 require group group_1 group_2 ...

The AuthType is limited to Basic. You may use one or more valid require lines. 
For a single require line with the requirement 'valid-user' or with the requirements 
'user user_1 user_2 ...' it is sufficient to use only the authentication handler.


=head1 DESCRIPTION

This module allows authentication and authorization against a database 
using Perl's DBI. For supported DBI drivers see: 

 http://dbi.perl.org/

Authentication:

For the given username the password is looked up in the cache. If the cache 
is not configured or if the user is not found in the cache, or if the given 
password does not match the cached password, it is requested from the database. 

If the username does not exist and the authoritative directive is set to 'on', 
the request is rejected. If the authoritative directive is set to 'off', the 
control is passed on to next module in line. 

If the password from the database for the given username is empty and the nopasswd 
directive is set to 'off', the request is rejected. If the nopasswd directive is set 
to 'on', any password is accepted. 

Finally the passwords (multiple passwords per userid are allowed) are 
retrieved from the database. The result is put into the environment variable 
REMOTE_PASSWORDS. Then it is compared to the password given. If the encrypted 
directive is set to 'on', the given password is encrypted using perl's crypt() 
function before comparison. If the encrypted directive is set to 'off' the 
plain-text passwords are compared. 

If this comparison fails the request is rejected, otherwise the request is 
accepted and the password is put into the environment variable REMOTE_PASSWORD.

The SQL-select used for retrieving the passwords is as follows: 

 SELECT pwd_field FROM pwd_table WHERE uid_field = user

If a pwd_whereclause exists, it is appended to the SQL-select.

This module supports in addition a simple kind of logging mechanism. Whenever 
the handler is called and a log_string is configured, the log_field will be 
updated with the log_string. As log_string - depending upon the database - 
macros like TODAY can be used. 

The SQL-select used for the logging mechanism is as follows: 

 UPDATE pwd_table SET log_field = log_string WHERE uid_field = user

Authorization:

When the authorization handler is called, the authentication has already been 
done. This means, that the given username/password has been validated. 

The handler analyzes and processes the requirements line by line. The request 
is accepted if the first requirement is fulfilled. 

In case of 'valid-user' the request is accepted. 

In case of one or more user-names, they are compared with the given user-name 
until the first match. 

In case of one or more group-names, all groups of the given username are 
looked up in the cache. If the cache is not configured or if the user is not 
found in the cache, or if the requested group does not match the cached group, 
the groups are requested from the database. A comma separated list of all 
these groups is put into the environment variable REMOTE_GROUPS. Then these 
groups are compared with the required groups until the first match. 

If there is no match and the authoritative directive is set to 'on' the 
request is rejected. 

In case the authorization succeeds, the environment variable REMOTE_GROUP is 
set to the group name, which can be used by user scripts without accessing
the database again.

The SQL-select used for retrieving the groups is as follows (depending upon 
the existence of a grp_table): 

 SELECT grp_field FROM pwd_table WHERE uid_field = user
 SELECT grp_field FROM grp_table WHERE uid_field = user

This way the group-information can either be held in the main users table, or 
in an extra table, if there is an m:n relationship between users and groups. 
From all selected groups a comma-separated list is build, which is compared 
with the required groups. If you don't like normalized group records you can 
put such a comma-separated list of groups (no spaces) into the grp_field 
instead of single groups. 

If a grp_whereclause exists, it is appended to the SQL-select.

Cache:

The module maintains an optional cash for all passwords/groups. See the
method setCacheTime(n) on how to enable the cache. Every server has it's 
own cache. Optionally the cache can be put into a shared memory segment, 
so that it can be shared among all servers. See the CONFIGURATION section 
on how to enable the usage of shared memory. 

In order to prevent the cache from growing indefinitely a CleanupHandler can 
be initialized, which skips through the cache and deletes all outdated entries.
This can be done once per request after sending the response, hence without 
slowing down response time to the client. The minimum time between two successive 
runs of the CleanupHandler is configurable (see the CONFIGURATION section). The 
default is 0, which runs the CleanupHandler after every request. 

 
=head1 LIST OF TOKENS

=item *
Auth_DBI_data_source (Authentication and Authorization)

The data_source value has the syntax 'dbi:driver:dsn'. This parameter is 
passed to the database driver for processing during connect. The data_source 
parameter (as well as the username and the password parameters) may be a 
tilde ('~') separated list of several data_sources. All of these triples will 
be used until a successful connect is made. This way several backup-servers can 
be configured. if you want to use the environment variable DBI_DSN instead of 
a data_source, do not specify this parameter at all. 

=item *
Auth_DBI_username (Authentication and Authorization)

The username argument is passed to the database driver for processing during 
connect. This parameter may be a tilde ('~') separated list. See the data_source 
parameter above for the usage of a list. 

=item *
Auth_DBI_password (Authentication and Authorization)

The password argument is passed to the database driver for processing during 
connect. This parameter may be a tilde ('~')  separated list. See the data_source 
parameter above for the usage of a list. 

=item *
Auth_DBI_pwd_table (Authentication and Authorization)

Contains at least the fields with the username and the (possibly encrypted) 
password. The username should be unique. 

=item *
Auth_DBI_uid_field (Authentication and Authorization)

Field name containing the username in the Auth_DBI_pwd_table. 

=item *
Auth_DBI_pwd_field (Authentication only)

Field name containing the password in the Auth_DBI_pwd_table. 

=item *
Auth_DBI_pwd_whereclause (Authentication only)

Use this option for specifying more constraints to the SQL-select.

=item *
Auth_DBI_grp_table (Authorization only)

Contains at least the fields with the username and the groupname. 

=item *
Auth_DBI_grp_field (Authorization only)

Field-name containing the groupname in the Auth_DBI_grp_table. 

=item *
Auth_DBI_grp_whereclause (Authorization only)

Use this option for specifying more constraints to the SQL-select.

=item *
Auth_DBI_log_field (Authentication only)

Field name containing the log string in the Auth_DBI_pwd_table. 

=item *
Auth_DBI_log_string (Authentication only)

String to update the Auth_DBI_log_field in the Auth_DBI_pwd_table. Depending 
upon the database this can be a macro like 'TODAY'. 

=item *
Auth_DBI_authoritative  < on / off> (Authentication and Authorization)

Default is 'on'. When set 'on', there is no fall-through to other 
authentication methods if the authentication check fails. When this directive 
is set to 'off', control is passed on to any other authentication modules. Be 
sure you know what you are doing when you decide to switch it off. 

=item *
Auth_DBI_nopasswd  < on / off > (Authentication only)

Default is 'off'. When set 'on' the password comparison is skipped if the 
password retrieved from the database is empty, i.e. allow any password. This is 
'off' by default to ensure that an empty Auth_DBI_pwd_field does not allow people 
to log in with a random password. Be sure you know what you are doing when you 
decide to switch it on. 

=item *
Auth_DBI_encrypted  < on / off > (Authentication only)

Default is 'on'. When set to 'on', the password retrieved from the database 
is assumed to be crypted. Hence the incoming password will be crypted before 
comparison. When this directive is set to 'off', the comparison is done directly 
with the plain-text entered password. 

=item *
Auth_DBI_encryption_salt < password / userid > (Authentication only)

When crypting the given password AuthDBI uses per default the password selected 
from the database as salt. Setting this parameter to 'userid', the module uses 
the userid as salt. 

=item *
Auth_DBI_uidcasesensitive  < on / off > (Authentication and Authorization)

Default is 'on'. When set 'off', the entered userid is converted to lower case.
Also the userid in the password select-statement is converted to lower case. 

=item *
Auth_DBI_pwdcasesensitive  < on / off > (Authentication only)

Default is 'on'. When set 'off', the entered password is converted to lower 
case. 

=item *
Auth_DBI_placeholder < on / off > (Authentication and Authorization)

Default is 'off'.  When set 'on', the select statement is prepared using a 
placeholder for the username.  This may result in improved performance for 
databases supporting this method.
 

=head1 CONFIGURATION

The module should be loaded upon startup of the Apache daemon.
Add the following line to your httpd.conf:

 PerlModule Apache::AuthDBI

A common usage is to load the module in a startup file via the PerlRequire 
directive. See eg/startup.pl for an example. 

There are three configurations which are server-specific and which can be done 
in a startup file: 

 Apache::AuthDBI->setCacheTime(0);

This configures the lifetime in seconds for the entries in the cache. 
Default is 0, which turns off the cache. When set to any value n > 0, the 
passwords/groups of all users will be cached for at least n seconds. After 
finishing the request, a special handler skips through the cache and deletes 
all outdated entries (entries, which are older than the CacheTime). 

 Apache::AuthDBI->setCleanupTime(-1);

This configures the minimum time in seconds between two successive runs of the 
CleanupHandler, which deletes all outdated entries from the cache. The default 
is -1, which disables the CleanupHandler. Setting the interval to 0 runs the
CleanupHandler after every request. For a heavily loaded server this should be 
set to a value, which reflects a compromise between scanning a large cache 
possibly containing many outdated entries and between running many times the 
CleanupHandler on a cache containing only few entries. 

 Apache::AuthDBI->initIPC(50000);

This enables the usage of shared memory for the cache. Instead of every server 
maintaining it's own cache, all servers have access to a common cache. This 
should minimize the database load considerably for sites running many servers. 
The number indicates the size of the shared memory segment in bytes. This size 
is fixed, there is no dynamic allocation of more segments. As a rule of thumb 
multiply the estimated maximum number of simultaneously cached users by 100 to 
get a rough estimate of the needed size. Values below 500 will be overwritten 
with the default 50000. 

To enable debugging the variable $Apache::AuthDBI::DEBUG must be set. This 
can either be done in startup.pl or in the user script. Setting the variable 
to 1, just reports about a cache miss. Setting the variable to 2 enables full 
debug output. 


=head1 PREREQUISITES

Note that this module needs mod_perl-1.08 or higher, apache_1.3.0 or higher 
and that mod_perl needs to be configured with the appropriate call-back hooks: 

  PERL_AUTHEN=1 PERL_AUTHZ=1 PERL_CLEANUP=1 PERL_STACKED_HANDLERS=1


=head1 SECURITY

In some cases it is more secure not to put the username and the password in 
the .htaccess file. The following example shows a solution to this problem:

httpd.conf:

 <Perl>
 my($uid,$pwd) = My::dbi_pwd_fetch();
 $Location{'/foo/bar'}->{PerlSetVar} = [
     [ Auth_DBI_username  => $uid ],
     [ Auth_DBI_password  => $pwd ],
 ];
 </Perl>


=head1 SEE ALSO

L<Apache>, L<mod_perl>, L<DBI>


=head1 AUTHORS

=item *
Apache::AuthDBI by Edmund Mergl; now maintained and supported by the
modperl mailinglist, subscribe by sending mail to
modperl-subscribe@perl.apache.org.

=item *
mod_perl by Doug MacEachern.

=item *
DBI by Tim Bunce <dbi-users-subscribe@perl.org>



=head1 COPYRIGHT

The Apache::AuthDBI module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

=cut