KRB5_SET_DEFAULT_REALM(3)

✨ KRB5_SET_DEFAULT_REALM(3) ✨

okay so bestie, we're in the Library Functions Manual today and this page is literally about default and host realm read and manipulation routines — the KRB5_SET_DEFAULT_REALM(3) of it all. Kerberos realms, babes. Let's get into it 🎀

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💖 NAME 💖

krb5_copy_host_realm, krb5_free_host_realm, krb5_get_default_realm, krb5_get_default_realms, krb5_get_host_realm, krb5_set_default_realm — default and host realm read and manipulation routines

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🦋 LIBRARY 🦋

Kerberos 5 Library (libkrb5, -lkrb5)

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🌸 SYNOPSIS 🌸

#include <krb5.h>

krb5_error_code
krb5_copy_host_realm(krb5_context context, const krb5_realm *from,
    krb5_realm **to);

krb5_error_code
krb5_free_host_realm(krb5_context context, krb5_realm *realmlist);

krb5_error_code
krb5_get_default_realm(krb5_context context, krb5_realm *realm);

krb5_error_code
krb5_get_default_realms(krb5_context context, krb5_realm **realm);

krb5_error_code
krb5_get_host_realm(krb5_context context, const char *host,
    krb5_realm **realms);

krb5_error_code
krb5_set_default_realm(krb5_context context, const char *realm);

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👑 DESCRIPTION 👑

🫶 the realm shuffle

krb5_copy_host_realm() copies the list of realms from from to to. and the way that to is now your problem, bestie — the caller has to free it with krb5_free_host_realm. no cap, it's giving "you break it, you buy it" 💅

krb5_free_host_realm() frees all memory allocated by realmlist. that's it, that's the whole job, and honestly? iconic. clean up after yourself, queen 🌈

krb5_get_default_realm() returns the first default realm for this host. the realm it hands you should be freed with krb5_xfree(). not krb5_free_host_realm, not vibes, krb5_xfree(). iykyk ✨

krb5_get_default_realms() (plural, we love a plot twist) returns a NULL terminated list of default realms for this context. and the realms it returns should be freed with krb5_free_host_realm(). yes, different from the one above. no, i don't make the rules 🥲

krb5_get_host_realm() returns a NULL terminated list of realms for host, and it does that by looking up the info in the [domain_realm] in krb5.conf or in DNS. and here's the cute little easter egg: if the mapping in [domain_realm] results in the string dns_locate, then DNS is used to look up the realm. periodt 💫

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🌐 dns detective work, a saga

when it's using DNS to resolve the domain for the host a.b.c, krb5_get_host_realm() goes looking for a TXT resource record named _kerberos.a.b.c. and if it doesn't find it? it strips off the first component and tries again (_kerberos.b.c) — and it just keeps doing that, climbing and climbing, until it reaches the root. main character energy fr fr 🔥

if there's no configuration or DNS information found, krb5_get_host_realm() assumes it can use the domain part of the host to form a realm. and the caller must free realmlist with krb5_free_host_realm(). every single time. don't skip it 🙈

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🎀 setting the default realm

krb5_set_default_realm() sets the default realm for the context. and here's the fallback chain, bestie, write it down:

• if NULL is used as a realm, the [libdefaults]default_realm stanza in krb5.conf is used 💖
• if there is no such stanza in the configuration file, the krb5_get_host_realm() function is used to form a default realm 🦋

three layers deep. it's giving backup plan for the backup plan. slay 💅

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⭐ SEE ALSO ⭐

• free(3)
• krb5.conf(5)

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ok bestie that's the whole page, go forth and manage your realms responsibly 🫶✨

HEIMDAL · April 24, 2005 · that's the source, the version and the date, mwah, love u, bye 💜🎀