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krb5_keytab_intro(3) HeimdalKerberos5library krb5_keytab_intro(3)
NAME
krb5_keytab_intro - The keytab handing functions
Kerberos Keytabs
See the library functions here: Heimdal Kerberos 5 keytab handling
functions
Keytabs are long term key storage for servers, their equvalment of
password files.
Normally the only function that useful for server are to specify what
keytab to use to other core functions like krb5_rd_req()
krb5_kt_resolve(), and krb5_kt_close().
Keytab names
A keytab name is on the form type:residual. The residual part is
specific to each keytab-type.
When a keytab-name is resolved, the type is matched with an internal
list of keytab types. If there is no matching keytab type, the default
keytab is used. The current default type is FILE.
The default value can be changed in the configuration file
/etc/krb5.conf by setting the variable [defaults]default_keytab_name.
The keytab types that are implemented in Heimdal are:
o file store the keytab in a file, the type's name is FILE . The
residual part is a filename. For compatibility with other Kerberos
implemtation WRFILE and JAVA14 is also accepted. WRFILE has the same
format as FILE. JAVA14 have a format that is compatible with older
versions of MIT kerberos and SUN's Java based installation. They
store a truncted kvno, so when the knvo excess 255, they are truncted
in this format.
o keytab store the keytab in a AFS keyfile (usually
/usr/afs/etc/KeyFile ), the type's name is AFSKEYFILE. The residual
part is a filename.
o memory The keytab is stored in a memory segment. This allows
sensitive and/or temporary data not to be stored on disk. The type's
name is MEMORY. Each MEMORY keytab is referenced counted by and
opened by the residual name, so two handles can point to the same
memory area. When the last user closes using krb5_kt_close() the
keytab, the keys in they keytab is memset() to zero and freed and can
no longer be looked up by name.
Keytab example
This is a minimalistic version of ktutil.
int
main (int argc, char **argv)
{
krb5_context context;
krb5_keytab keytab;
krb5_kt_cursor cursor;
krb5_keytab_entry entry;
if (ret)
krb5_err(context, 1, ret, 'krb5_kt_default');
ret = krb5_kt_start_seq_get(context, keytab, &cursor);
if (ret)
krb5_err(context, 1, ret, 'krb5_kt_start_seq_get');
while((ret = krb5_kt_next_entry(context, keytab, &entry, &cursor)) == 0){
krb5_unparse_name(context, entry.principal, &principal);
printf('principal: %s0, principal);
free(principal);
krb5_kt_free_entry(context, &entry);
}
ret = krb5_kt_end_seq_get(context, keytab, &cursor);
if (ret)
krb5_err(context, 1, ret, 'krb5_kt_end_seq_get');
ret = krb5_kt_close(context, keytab);
if (ret)
krb5_err(context, 1, ret, 'krb5_kt_close');
krb5_free_context(context);
return 0;
}
Version 1.5.2 11 Jan 2012 krb5_keytab_intro(3)