NAME

       krb5_425_conv_principal,  krb5_425_conv_principal_ext,  krb5_524_conv_principal  —  converts  to and from
       version 4 principals

LIBRARY

       Kerberos 5 Library (libkrb5, -lkrb5)

SYNOPSIS

       #include <krb5.h>

       krb5_error_code
       krb5_425_conv_principal(krb5_context context, const char *name, const char *instance, const char  *realm,
           krb5_principal *principal);

       krb5_error_code
       krb5_425_conv_principal_ext(krb5_context    context,    const   char   *name,   const   char   *instance,
           const  char  *realm,  krb5_boolean  (*func)(krb5_context,  krb5_principal),   krb5_boolean   resolve,
           krb5_principal *principal);

       krb5_error_code
       krb5_524_conv_principal(krb5_context context, const krb5_principal principal, char *name, char *instance,
           char *realm);

DESCRIPTION

       Converting between version 4 and version 5 principals can at best be described as a mess.

       A version 4 principal consists of a name, an instance, and a realm. A version 5 principal consists of one
       or  more components, and a realm. In some cases also the first component/name will differ between version
       4 and version 5.  Furthermore the second component of a host principal will be the fully qualified domain
       name of the host in question, while the instance of a version 4 principal will  only  contain  the  first
       part  (short hostname).  Because of these problems the conversion between principals will have to be site
       customized.

       krb5_425_conv_principal_ext() will try to convert a version 4 principal, given  by  name,  instance,  and
       realm, to a version 5 principal. This can result in several possible principals, and if func is non-NULL,
       it will be called for each candidate principal.  func should return true if the principal was “good”.  To
       accomplish this, krb5_425_conv_principal_ext() will look up the name in krb5.conf.  It first looks in the
       v4_name_convert/host  subsection, which should contain a list of version 4 names whose instance should be
       treated as a hostname. This list can be specified for each realm (in  the  realms  section),  or  in  the
       libdefaults  section.  If the name is found the resulting name of the principal will be the value of this
       binding. The instance is then first looked up in v4_instance_convert for the specified  realm.  If  found
       the  resulting  value  will be used as instance (this can be used for special cases), no further attempts
       will be made to find a conversion if this fails (with func).  If  the  resolve  parameter  is  true,  the
       instance  will  be looked up with gethostbyname().  This can be a time consuming, error prone, and unsafe
       operation.  Next a list of hostnames will be created from the instance and the v4_domains variable, which
       should contain a list of possible domains for the specific realm.

       On the other hand, if the name is not found in a host section, it is looked up in a v4_name_convert/plain
       binding. If found here the name will be converted, but the instance will be untouched.

       This list of default host-type conversions is compiled-in:

             v4_name_convert = {
                     host = {
                             ftp = ftp
                             hprop = hprop
                             imap = imap
                             pop = pop
                             rcmd = host
                             smtp = smtp
                     }
             }

       It will only be used if there isn't an entry for these names in the config  file,  so  you  can  override
       these defaults.

       krb5_425_conv_principal()  will  call  krb5_425_conv_principal_ext()  with NULL as func, and the value of
       v4_instance_resolve (from the libdefaults section) as resolve.

       krb5_524_conv_principal() basically does the opposite of krb5_425_conv_principal(), it just doesn't  have
       to  look up any names, but will instead truncate instances found to belong to a host principal. The name,
       instance, and realm should be at least 40 characters long.

EXAMPLES

       Since this is confusing an example is in place.

       Assume that we have the “foo.com”, and “bar.com” domains that have  shared  a  single  version  4  realm,
       FOO.COM. The version 4 krb.realms file looked like:

             foo.com         FOO.COM
             .foo.com        FOO.COM
             .bar.com        FOO.COM

       A krb5.conf file that covers this case might look like:

             [libdefaults]
                     v4_instance_resolve = yes
             [realms]
                     FOO.COM = {
                             kdc = kerberos.foo.com
                             v4_instance_convert = {
                                     foo = foo.com
                             }
                             v4_domains = foo.com
                     }

       With this setup and the following host table:

             foo.com
             a-host.foo.com
             b-host.bar.com
       the following conversions will be made:

             rcmd.a-host     -> host/a-host.foo.com
             ftp.b-host      -> ftp/b-host.bar.com
             pop.foo         -> pop/foo.com
             ftp.other       -> ftp/other.foo.com
             other.a-host    -> other/a-host

       The  first  three are what you expect. If you remove the “v4_domains”, the fourth entry will result in an
       error (since the host “other” can't be found). Even if “a-host” is a valid host name, the last entry will
       not be converted, since the “other” name is not known to represent a host-type principal.   If  you  turn
       off  “v4_instance_resolve” the second example will result in “ftp/b-host.foo.com” (because of the default
       domain). And all of this is of course only valid if you have working name resolving.

SEE ALSO

       krb5_build_principal(3),    krb5_free_principal(3),    krb5_parse_name(3),    krb5_sname_to_principal(3),
       krb5_unparse_name(3), krb5.conf(5)

HEIMDAL                                         September 3, 2003                     KRB5_425_CONV_PRINCIPAL(3)