Wallet::Config

(Configuration handling for the wallet server)

SYNOPSIS

    use Wallet::Config;
    my $driver = $Wallet::Config::DB_DRIVER;
    my $info;
    if (defined $Wallet::Config::DB_INFO) {
        $info = $Wallet::Config::DB_INFO;
    } else {
        $info = "database=$Wallet::Config::DB_NAME";
        $info .= ";host=$Wallet::Config::DB_HOST"
            if $Wallet::Config::DB_HOST;
        $info .= ";port=$Wallet::Config::DB_PORT"
            if $Wallet::Config::DB_PORT;
    }
    my $dsn = "dbi:$driver:$info";
    my $user = $Wallet::Config::DB_USER;
    my $password = $Wallet::Config::DB_PASSWORD;
    my $dbh = DBI->connect ($dsn, $user, $password);

DESCRIPTION

Wallet::Config encapsulates all of the site-specific configuration for the wallet server. It is implemented as a Perl class that declares and sets the defaults for various configuration variables and then, if it exists, loads the file specified by the WALLET_CONFIG environment variable or /etc/wallet/wallet.conf if that environment variable isn't set. That file should contain any site-specific overrides to the defaults, and at least some parameters must be set.

This file must be valid Perl. To set a variable, use the syntax:

    $VARIABLE = <value>;

where VARIABLE is the variable name (always in all-capital letters) and <value> is the value. If setting a variable to a string and not a number, you should normally enclose <value> in ''. For example, to set the variable DB_DRIVER to MySQL, use:

    $DB_DRIVER = 'MySQL';

Always remember the initial dollar sign ($) and ending semicolon (;). Those familiar with Perl syntax can of course use the full range of Perl expressions.

This configuration file should end with the line:

    1;

This ensures that Perl doesn't think there is an error when loading the file.

DATABASE CONFIGURATION

DB_DDL_DIRECTORY

Specifies the directory used to dump the database schema in formats for each possible database server. This also includes diffs between schema versions, for upgrades. The default value is /usr/local/share/wallet, which matches the default installation location.

DB_DRIVER

Sets the Perl database driver to use for the wallet database. Common values would be SQLite or MySQL. Less common values would be Oracle, Sybase, or ODBC. The appropriate DBD::* Perl module for the chosen driver must be installed and will be dynamically loaded by the wallet. For more information, see DBI.

This variable must be set.

DB_INFO

Sets the remaining contents for the DBI DSN (everything after the driver). Using this variable provides full control over the connect string passed to DBI. When using SQLite, set this variable to the path to the SQLite database. If this variable is set, DB_NAME, DB_HOST, and DB_PORT are ignored. For more information, see DBI and the documentation for the database driver you're using.

Either DB_INFO or DB_NAME must be set. If you don't need to pass any additional information to DBI, set DB_INFO to the empty string ('').

DB_NAME

If DB_INFO is not set, specifies the database name. The third part of the DBI connect string will be set to database=DB_NAME, possibly with a host and port appended if DB_HOST and DB_PORT are set. For more information, see DBI and the documentation for the database driver you're using.

Either DB_INFO or DB_NAME must be set.

DB_HOST

If DB_INFO is not set, specifies the database host. ;host=DB_HOST will be appended to the DBI connect string. For more information, see DBI and the documentation for the database driver you're using.

DB_PORT

If DB_PORT is not set, specifies the database port. ;port=DB_PORT will be appended to the DBI connect string. If this variable is set, DB_HOST should also be set. For more information, see DBI and the documentation for the database driver you're using.

DB_USER

Specifies the user for database authentication. Some database backends, particularly SQLite, do not need this.

DB_PASSWORD

Specifies the password for database authentication. Some database backends, particularly SQLite, do not need this.

DUO OBJECT CONFIGURATION

These configuration variables only need to be set if you intend to use the duo object type (the Wallet::Object::Duo class).

DUO_AGENT

If this configuration variable is set, its value should be an object that is call-compatible with LWP::UserAgent. This object will be used instead of LWP::UserAgent to make API calls to Duo. This is primarily useful for testing, allowing replacement of the user agent with a mock implementation so that a test can run without needing a Duo account.

DUO_KEY_FILE

The path to a file in JSON format that contains the key and hostname data for the Duo Admin API integration used to manage integrations via wallet. This file should be in the format expected by the key_file parameter to the Net::Duo::Admin constructor. See Net::Duo::Admin for more information.

DUO_KEY_FILE must be set to use Duo objects.

DUO_TYPE

The type of integration to create. The default value is unix to create UNIX integrations, since this was the first integration created and users may rely on it to still be the default.

FILE OBJECT CONFIGURATION

These configuration variables only need to be set if you intend to use the file object type (the Wallet::Object::File class).

FILE_BUCKET

The directory into which to store file objects. File objects will be stored in subdirectories of this directory. See Wallet::Object::File for the full details of the naming scheme. This directory must be writable by the wallet server and the wallet server must be able to create subdirectories of it.

FILE_BUCKET must be set to use file objects.

FILE_MAX_SIZE

The maximum size of data that can be stored in a file object in bytes. If this configuration variable is set, an attempt to store data larger than this limit will be rejected.

PASSWORD OBJECT CONFIGURATION

These configuration variables only need to be set if you intend to use the password object type (the Wallet::Object::Password class). You will also need to set the FILE_MAX_SIZE value from the file object configuration, as that is inherited.

PWD_FILE_BUCKET

The directory into which to store password objects. Password objects will be stored in subdirectories of this directory. See Wallet::Object::Password for the full details of the naming scheme. This directory must be writable by the wallet server and the wallet server must be able to create subdirectories of it.

PWD_FILE_BUCKET must be set to use file objects.

PWD_LENGTH_MIN

The minimum length for any auto-generated password objects created when get is run before data is stored.

PWD_LENGTH_MAX

The maximum length for any auto-generated password objects created when get is run before data is stored.

KEYTAB OBJECT CONFIGURATION

These configuration variables only need to be set if you intend to use the keytab object type (the Wallet::Object::Keytab class).

KEYTAB_FILE

Specifies the keytab to use to authenticate to kadmind. The principal whose key is stored in this keytab must have the ability to create, modify, inspect, and delete any principals that should be managed by the wallet. (In MIT Kerberos kadm5.acl parlance, this is admci privileges.)

KEYTAB_FILE must be set to use keytab objects with any backend other than Active Directory.

KEYTAB_FLAGS

These flags, if any, are passed to the addprinc command when creating a new principal in the Kerberos KDC. To not pass any flags, set KEYTAB_FLAGS to the empty string. The default value is -clearpolicy, which clears any password strength policy from principals created by the wallet. (Since the wallet randomizes the keys, password strength checking is generally pointless and may interact poorly with the way addprinc -randkey works when third-party add-ons for password strength checking are used.)

This option is ignored when using Active Directory.

KEYTAB_HOST

Specifies the host on which the kadmin or Active Directory service is running. This setting overrides the admin_server setting in the [realms] section of krb5.conf and any DNS SRV records and allows the wallet to run on a system that doesn't have a Kerberos configuration for the wallet's realm.

KEYTAB_KADMIN

The path to the kadmin command-line client. The default value is kadmin, which will cause the wallet to search for kadmin on its default PATH.

This option is ignored when using Active Directory.

KEYTAB_KRBTYPE

The Kerberos KDC implementation type, chosen from AD, Heimdal, or MIT (case-insensitive). KEYTAB_KRBTYPE must be set to use keytab objects.

KEYTAB_PRINCIPAL

The principal whose key is stored in KEYTAB_FILE. The wallet will authenticate as this principal to the kadmin service.

KEYTAB_PRINCIPAL must be set to use keytab objects unless Active Directory is the backend, at least until kadmin is smart enough to use the first principal found in the keytab it's using for authentication.

KEYTAB_REALM

Specifies the realm in which to create Kerberos principals. The keytab object implementation can only work in a single realm for a given wallet installation and the keytab object names are stored without realm. KEYTAB_REALM is added when talking to the KDC via kadmin.

KEYTAB_REALM must be set to use keytab objects. ktadd doesn't always default to the local realm and the Active Directory integration requires it.

KEYTAB_TMP

A directory into which the wallet can write keytabs temporarily while processing get commands from clients. The keytabs are written into this directory with predictable names, so this should not be a system temporary directory such as /tmp or /var/tmp. It's best to create a directory solely for this purpose that's owned by the user the wallet server will run as.

KEYTAB_TMP must be set to use keytab objects.

The following parameters are specific to generating keytabs from Active Directory (KEYTAB_KRBTYPE is set to AD).

AD_CACHE

Specifies the ticket cache to use when manipulating Active Directory objects. The ticket cache must be for a principal able to bind to Active Directory and run msktutil.

AD_CACHE must be set to use Active Directory support.

AD_COMPUTER_DN

The LDAP base DN for computer objects inside Active Directory. All keytabs of the form host/<hostname> will be mapped to objects with a samAccountName of the <hostname> portion under this DN.

AD_COMPUTER_DN must be set if using Active Directory as the keytab backend.

AD_DEBUG

If set to true, asks for some additional debugging information, such as the msktutil command, to be logged to syslog. These debugging messages will be logged to the local3 facility.

AD_MSKTUTIL

The path to the msktutil command-line client. The default value is msktutil, which will cause the wallet to search for msktutil on its default PATH.

AD_USER_DN

The LDAP base DN for user objects inside Active Directory. All keytabs of the form service/<user> will be mapped to objects with a servicePrincipalName matching the wallet object name under this DN.

AD_USER_DN must be set if using Active Directory as the keytab backend.

Retrieving Existing Keytabs

Heimdal provides the choice, over the network protocol, of either downloading the existing keys for a principal or generating new random keys. MIT Kerberos does not; downloading a keytab over the kadmin protocol always rekeys the principal.

For MIT Kerberos, the keytab object backend therefore optionally supports retrieving existing keys, and hence keytabs, for Kerberos principals by contacting the KDC via remctl and talking to keytab-backend. This is enabled by setting the unchanging flag on keytab objects. To configure that support, set the following variables.

This is not required for Heimdal; for Heimdal, setting the unchanging flag is all that's needed.

KEYTAB_REMCTL_CACHE

Specifies the ticket cache to use when retrieving existing keytabs from the KDC. This is only used to implement support for the unchanging flag. The ticket cache must be for a principal with access to run keytab retrieve via remctl on KEYTAB_REMCTL_HOST.

KEYTAB_REMCTL_HOST

The host to which to connect with remctl to retrieve existing keytabs. This is only used to implement support for the unchanging flag. This host must provide the keytab retrieve command and KEYTAB_REMCTL_CACHE must also be set to a ticket cache for a principal with access to run that command.

KEYTAB_REMCTL_PRINCIPAL

The service principal to which to authenticate when retrieving existing keytabs. This is only used to implement support for the unchanging flag. If this variable is not set, the default is formed by prepending host/ to KEYTAB_REMCTL_HOST. (Note that KEYTAB_REMCTL_HOST is not lowercased first.)

KEYTAB_REMCTL_PORT

The port on KEYTAB_REMCTL_HOST to which to connect with remctl to retrieve existing keytabs. This is only used to implement support for the unchanging flag. If this variable is not set, the default remctl port will be used.

WEBAUTH KEYRING OBJECT CONFIGURATION

These configuration variables only need to be set if you intend to use the wakeyring object type (the Wallet::Object::WAKeyring class).

WAKEYRING_BUCKET

The directory into which to store WebAuth keyring objects. WebAuth keyring objects will be stored in subdirectories of this directory. See Wallet::Object::WAKeyring for the full details of the naming scheme. This directory must be writable by the wallet server and the wallet server must be able to create subdirectories of it.

WAKEYRING_BUCKET must be set to use WebAuth keyring objects.

WAKEYRING_REKEY_INTERVAL

The interval, in seconds, at which new keys are generated in a keyring. The object implementation will try to arrange for there to be keys added to the keyring separated by this interval.

It's useful to provide some interval to install the keyring everywhere that it's used before the key becomes inactive. Every keyring will therefore normally have at least three keys: one that's currently active, one that becomes valid in the future but less than WAKEYRING_REKEY_INTERVAL from now, and one that becomes valid between one and two of those intervals into the future. This means that one has twice this interval to distribute the keyring everywhere it is used.

Internally, this is implemented by adding a new key that becomes valid in twice this interval from the current time if the newest key becomes valid at or less than this interval in the future.

The default value is 60 * 60 * 24 (one day).

WAKEYRING_PURGE_INTERVAL

The interval, in seconds, from the key creation date after which keys are removed from the keyring. This is used to clean up old keys and finish key rotation. Keys won't be removed unless there are more than three keys in the keyring to try to keep a misconfiguration from removing all valid keys.

The default value is 60 * 60 * 24 * 90 (90 days).

EXTERNAL ACL CONFIGURATION

This configuration variable is only needed if you intend to use the external ACL type (the Wallet::ACL::External class). This ACL type runs an external command to determine if access is granted.

EXTERNAL_COMMAND

Path to the command to run to determine whether access is granted. The first argument to the command will be the principal requesting access. The second and third arguments will be the type and name of the object that principal is requesting access to. The final argument will be the identifier of the ACL.

No other arguments are passed to the command, but the command will have access to all of the remctl environment variables seen by the wallet server (such as REMOTE_USER). For a full list of environment variables, see "ENVIRONMENT" in remctld(8).

The external command should exit with a non-zero status but no output to indicate a normal failure to satisfy the ACL. Any output will be treated as an error.

LDAP ACL CONFIGURATION

These configuration variables are only needed if you intend to use the ldap-attr ACL type (the Wallet::ACL::LDAP::Attribute class). They specify the LDAP server and additional connection and data model information required for the wallet to check for the existence of attributes.

LDAP_HOST

The LDAP server name to use to verify LDAP ACLs. This variable must be set to use LDAP ACLs.

LDAP_BASE

The base DN under which to search for the entry corresponding to a principal. Currently, the wallet always does a full subtree search under this base DN. This variable must be set to use LDAP ACLs.

LDAP_FILTER_ATTR

The attribute used to find the entry corresponding to a principal. The LDAP entry containing this attribute with a value equal to the principal will be found and checked for the required attribute and value. If this variable is not set, the default is krb5PrincipalName.

LDAP_CACHE

Specifies the Kerberos ticket cache to use when connecting to the LDAP server. GSS-API authentication is always used; there is currently no support for any other type of bind. The ticket cache must be for a principal with access to verify the values of attributes that will be used with this ACL type. This variable must be set to use LDAP ACLs.

Finally, depending on the structure of the LDAP directory being queried, there may not be any attribute in the directory whose value exactly matches the Kerberos principal. The attribute designated by LDAP_FILTER_ATTR may instead hold a transformation of the principal name (such as the principal with the local realm stripped off, or rewritten into an LDAP DN form). If this is the case, define a Perl function named ldap_map_principal. This function will be called whenever an LDAP attribute ACL is being verified. It will take one argument, the principal, and is expected to return the value to search for in the LDAP directory server.

For example, if the principal name without the local realm is stored in the uid attribute in the directory, set LDAP_FILTER_ATTR to uid and then define ldap_map_attribute as follows:

    sub ldap_map_principal {
        my ($principal) = @_;
        $principal =~ s/\@EXAMPLE\.COM$//;
        return $principal;
    }

Note that this example only removes the local realm (here, EXAMPLE.COM). Any principal from some other realm will be left fully qualified, and then presumably will not be found in the directory.

NETDB ACL CONFIGURATION

These configuration variables are only needed if you intend to use the netdb ACL type (the Wallet::ACL::NetDB class). They specify the remctl connection information for retrieving user roles from NetDB and the local realm to remove from principals (since NetDB normally expects unscoped local usernames).

NETDB_REALM

The wallet uses fully-qualified principal names (including the realm), but NetDB normally expects local usernames without the realm. If this variable is set, the given realm will be stripped from any principal names before passing them to NetDB. Principals in other realms will be passed to NetDB without modification.

NETDB_REMCTL_CACHE

Specifies the ticket cache to use when querying the NetDB remctl interface for user roles. The ticket cache must be for a principal with access to run netdb node-roles via remctl on KEYTAB_REMCTL_HOST. This variable must be set to use NetDB ACLs.

NETDB_REMCTL_HOST

The host to which to connect with remctl to query NetDB for user roles. This host must provide the netdb node-roles command and NETDB_REMCTL_CACHE must also be set to a ticket cache for a principal with access to run that command. This variable must be set to use NetDB ACLs.

NETDB_REMCTL_PRINCIPAL

The service principal to which to authenticate when querying NetDB for user roles. If this variable is not set, the default is formed by prepending host/ to NETDB_REMCTL_HOST. (Note that NETDB_REMCTL_HOST is not lowercased first.)

NETDB_REMCTL_PORT

The port on NETDB_REMCTL_HOST to which to connect with remctl to query NetDB for user roles. If this variable is not set, the default remctl port will be used.

DEFAULT OWNERS

By default, only users in the ADMIN ACL can create new objects in the wallet. To allow other users to create new objects, define a Perl function named default_owner. This function will be called whenever a non-ADMIN user tries to create a new object and will be passed the type and name of the object. It should return undef if there is no default owner for that object. If there is, it should return a list containing the name to use for the ACL and then zero or more anonymous arrays of two elements each giving the type and identifier for each ACL entry.

For example, the following simple function says to use a default owner named default with one entry of type krb5 and identifier rra@example.com for the object with type keytab and name host/example.com:

    sub default_owner {
        my ($type, $name) = @_;
        if ($type eq 'keytab' and $name eq 'host/example.com') {
            return ('default', [ 'krb5', 'rra@example.com' ]);
        } else {
            return;
        }
    }

Of course, normally this function is used for more complex mappings. Here is a more complete example. For objects of type keytab corresponding to various types of per-machine principals, return a default owner that sets as owner anyone with a NetDB role for that system and the system's host principal. This permits authorization management using NetDB while also allowing the system to bootstrap itself once the host principal has been downloaded and rekey itself using the old host principal.

    sub default_owner {
        my ($type, $name) = @_;
        my %allowed = map { $_ => 1 }
            qw(HTTP cifs host imap ldap nfs pop sieve smtp webauth);
        my $realm = 'example.com';
        return unless $type eq 'keytab';
        return unless $name =~ m%/%;
        my ($service, $instance) = split ('/', $name, 2);
        return unless $allowed{$service};
        my $acl_name = "host/$instance";
        my @acl = ([ 'netdb', $instance ],
                   [ 'krb5', "host/$instance\@$realm" ]);
        return ($acl_name, @acl);
    }

The auto-created ACL used for the owner of the new object will, in the above example, be named host/system where system is the fully-qualified name of the system as derived from the keytab being requested.

If the name of the ACL returned by the default_owner function matches an ACL that already exists in the wallet database, the existing ACL will be compared to the default ACL returned by the default_owner function. If the existing ACL has the same entries as the one returned by default_owner, creation continues if the user is authorized by that ACL. If they don't match, creation of the object is rejected, since the presence of an existing ACL may indicate that something different is being done with this object.

NAMING ENFORCEMENT

By default, wallet permits administrators to create objects of any name (unless the object backend rejects the name). However, naming standards for objects can be enforced, even for administrators, by defining a Perl function in the configuration file named verify_name. If such a function exists, it will be called for any object creation and will be passed the type of object, the object name, and the identity of the person doing the creation. If it returns undef or the empty string, object creation will be allowed. If it returns anything else, object creation is rejected and the return value is used as the error message.

This function is also called for naming audits done via Wallet::Report to find any existing objects that violate a (possibly updated) naming policy. In this case, the third argument (the identity of the person creating the object) will be undef. As a general rule, if the third argument is undef, the function should apply the most liberal accepted naming policy so that the audit returns only objects that violate all naming policies, but some sites may wish different results for their audit reports.

Please note that this return status is backwards from what one would normally expect. A false value is success; a true value is failure with an error message.

For example, the following verify_name function would ensure that any keytab objects for particular principals have fully-qualified hostnames:

    sub verify_name {
        my ($type, $name, $user) = @_;
        my %host_based = map { $_ => 1 }
            qw(HTTP cifs host imap ldap nfs pop sieve smtp webauth);
        return unless $type eq 'keytab';
        return unless $name =~ m%/%;
        my ($service, $instance) = split ('/', $name, 2);
        return unless $host_based{$service};
        return "host name $instance must be fully qualified"
            unless $instance =~ /\./;
        return;
    }

Objects that aren't of type keytab or which aren't for a host-based key have no naming requirements enforced by this example.

OBJECT HOST-BASED NAMES

The above demonstrates having a host-based naming convention, where we expect one part of an object name to be the name of the host that this object is for. The most obvious examples are those keytab objects above, where we want certain keytab names to be in the form of <service>/<hostname>. It's then also useful to provide a Perl function named is_for_host which then can be used to tell if a given object is a host-based keytab for a specific host. This function is then called by the objects_hostname in Wallet::Report to give a list of all host-based objects for a given hostname. It should return true if the given object is a host-based object for the hostname, otherwise false.

An example that matches the same policy as the last verify_name example would be:

    sub is_for_host {
        my ($type, $name, $hostname) = @_;
        my %host_based = map { $_ => 1 }
            qw(HTTP cifs host imap ldap nfs pop sieve smtp webauth);
        return 0 unless $type eq 'keytab';
        return 0 unless $name =~ m%/%;
        my ($service, $instance) = split ('/', $name, 2);
        return 0 unless $host_based{$service};
        return 1 if $hostname eq $instance;
        return 0;
    }

ACL NAMING ENFORCEMENT

Similar to object names, by default wallet permits administrators to create ACLs with any name. However, naming standards for ACLs can be enforced by defining a Perl function in the configuration file named verify_acl_name. If such a function exists, it will be called for any ACL creation or rename and will be passed given the new ACL name and the identity of the person doing the creation. If it returns undef or the empty string, object creation will be allowed. If it returns anything else, object creation is rejected and the return value is used as the error message.

This function is also called for naming audits done via Wallet::Report to find any existing objects that violate a (possibly updated) naming policy. In this case, the second argument (the identity of the person creating the ACL) will be undef. As a general rule, if the second argument is undef, the function should apply the most liberal accepted naming policy so that the audit returns only ACLs that violate all naming policies, but some sites may wish different results for their audit reports.

Please note that this return status is backwards from what one would normally expect. A false value is success; a true value is failure with an error message.

For example, the following verify_acl_name function would ensure that any ACLs created contain a slash and the part before the slash be one of host, group, user, or service.

    sub verify_acl_name {
        my ($name, $user) = @_;
        return 'ACL names must contain a slash' unless $name =~ m,/,;
        my ($first, $rest) = split ('/', $name, 2);
        my %types = map { $_ => 1 } qw(host group user service);
        unless ($types{$first}) {
            return "unknown ACL type $first";
        }
        return;
    }

Obvious improvements could be made, such as checking that the part after the slash for a host/ ACL looked like a host name and the part after a slash for a user/ ACL look like a user name.

ENVIRONMENT

WALLET_CONFIG

If this environment variable is set, it is taken to be the path to the wallet configuration file to load instead of /etc/wallet/wallet.conf.

SEE ALSO

DBI(3), Wallet::Object::Keytab(3), Wallet::Server(3), wallet-backend(8)

This module is part of the wallet system. The current version is available from <http://www.eyrie.org/~eagle/software/wallet/>.

AUTHOR

Russ Allbery <eagle@eyrie.org>

Last modified and spun 2016-01-24