KRB5_KEYTAB(3)

NAME
krb5_kt_ops, krb5_keytab_entry, krb5_kt_cursor, krb5_kt_add_entry, krb5_kt_close, krb5_kt_compare, krb5_kt_copy_entry_contents, krb5_kt_default, krb5_kt_default_name, krb5_kt_end_seq_get, krb5_kt_free_entry, krb5_kt_get_entry, krb5_kt_get_name, krb5_kt_get_type, krb5_kt_next_entry, krb5_kt_read_service_key, krb5_kt_register, krb5_kt_remove_entry, krb5_kt_resolve, krb5_kt_start_seq_get - manage keytab (key storage) files

LIBRARY
Kerberos 5 Library (libkrb5, -lkrb5)

SYNOPSIS
#include <krb5.h>

krb5_error_code
krb5_kt_add_entry(krb5_context context, krb5_keytab id, krb5_keytab_entry *entry);
krb5_error_code
krb5_kt_close(krb5_context context, krb5_keytab id);
krb5_boolean
krb5_kt_compare(krb5_context context, krb5_keytab_entry *entry, krb5_const_principal principal, krb5_kvno vno, krb5_enctype enctype);
krb5_error_code
krb5_kt_copy_entry_contents(krb5_context context, const krb5_keytab_entry *in, krb5_keytab_entry *out);
krb5_error_code
krb5_kt_default(krb5_context context, krb5_keytab *id);
krb5_error_code
krb5_kt_default_name(krb5_context context, char *name, size_t namesize);
krb5_error_code
krb5_kt_end_seq_get(krb5_context context, krb5_keytab id, krb5_kt_cursor *cursor);
krb5_error_code
krb5_kt_free_entry(krb5_context context, krb5_keytab_entry *entry);
krb5_error_code
krb5_kt_get_entry(krb5_context context, krb5_keytab id, krb5_const_principal principal, krb5_kvno kvno, krb5_enctype enctype, krb5_keytab_entry *entry);
krb5_error_code
krb5_kt_get_name(krb5_context context, krb5_keytab keytab, char *name, size_t namesize);
krb5_error_code
krb5_kt_get_type(krb5_context context, krb5_keytab keytab, char *prefix, size_t prefixsize);
krb5_error_code
krb5_kt_next_entry(krb5_context context, krb5_keytab id, krb5_keytab_entry *entry, krb5_kt_cursor *cursor);
krb5_error_code
krb5_kt_read_service_key(krb5_context context, krb5_pointer keyprocarg, krb5_principal principal, krb5_kvno vno, krb5_enctype enctype, krb5_keyblock **key);
krb5_error_code
krb5_kt_register(krb5_context context, const krb5_kt_ops *ops);
krb5_error_code
krb5_kt_remove_entry(krb5_context context, krb5_keytab id, krb5_keytab_entry *entry);
krb5_error_code
krb5_kt_resolve(krb5_context context, const char *name, krb5_keytab *id);
krb5_error_code
krb5_kt_start_seq_get(krb5_context context, krb5_keytab id, krb5_kt_cursor *cursor);

DESCRIPTION
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:

file
    store the keytab in a file, the type's name is KEYFILE. The residual part is a filename.

keyfile
    store the keytab in a AFS keyfile (usually /usr/afs/etc/KeyFile), the type's name is AFSKEYFILE. The residual part is a filename.

krb4
    the keytab is a Kerberos 4 srvtab that is on-the-fly converted to a keytab. The type's name is krb4. The residual part is a filename.

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. There are no residual part, the only pointer back to the keytab is the id returned by krb5_kt_resolve().

krb5_keytab_entry holds all data for an entry in a keytab file, like principal name, key-type, key, key-version number, etc. krb5_kt_cursor holds the current position that is used when iterating through a keytab entry with krb5_kt_start_seq_get(), krb5_kt_next_entry(), and krb5_kt_end_seq_get().

krb5_kt_ops contains the different operations that can be done to a keytab. This structure is normally only used when doing a new keytab-type implementation.

krb5_kt_resolve() is the equivalent of an open(2) on keytab. Resolve the keytab name in name into a keytab in id. Returns 0 or an error. The opposite of krb5_kt_resolve() is krb5_kt_close(). krb5_kt_close() frees all resources allocated to the keytab.

krb5_kt_default() sets the argument id to the default keytab. Returns 0 or an error.

krb5_kt_default_name() copy the name of the default keytab into name. Return 0 or KRB5_CONFIG_NOTENUFSPACE if namesize is too short.

krb5_kt_add_entry() Add a new entry to the keytab id. KRB5_KT_NOWRITE is returned if the keytab is a readonly keytab.

krb5_kt_compare() compares the passed in entry against principal, vno, and enctype. Any of principal, vno or enctype might be 0 which acts as a wildcard. Return TRUE if they compare the same, FALSE otherwise.

krb5_kt_copy_entry_contents() copies the contents of in into out. Returns 0 or an error.

krb5_kt_get_name() retrieves the name of the keytab keytab into name, namesize. Returns 0 or an error.

krb5_kt_get_type() retrieves the type of the keytab keytab and store the prefix/name for type of the keytab into prefix, prefixsize. The prefix will have the maximum length of KRB5_KT_PREFIX_MAX_LEN (including terminating NUL). Returns 0 or an error.

krb5_kt_free_entry() frees the contents of entry.

krb5_kt_start_seq_get() sets cursor to point at the beginning of id. Returns 0 or an error.

krb5_kt_next_entry() gets the next entry from id pointed to by cursor and advance the cursor. Returns 0 or an error.

krb5_kt_end_seq_get() releases all resources associated with cursor.

krb5_kt_get_entry() retrieves the keytab entry for principal, kvno, enctype into entry from the keytab id. Returns 0 or an error.

krb5_kt_read_service_key() reads the key identified by (principal, vno, enctype) from the keytab in keyprocarg (the default if == NULL) into *key. Returns 0 or an error.

krb5_kt_remove_entry() removes the entry entry from the keytab id. Returns 0 or an error.

krb5_kt_register() registers a new keytab type ops. Returns 0 or an error.

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_short(context, entry.principal, &principal);
    	printf("principal: %s\n", 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");
        krb5_free_context(context);
        return 0;
    }

SEE ALSO
krb5.conf(5), kerberos(8)