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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;
	   krb5_error_code ret;
	   char	*principal;

	   if (krb5_init_context (&context) != 0)
	       errx(1, 'krb5_context');

	   ret = krb5_kt_default (context, &keytab);
	   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)

NAME | Kerberos Keytabs

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