1KRB5_425_CONV_PRINCIP... BSD Library Functions Manual KRB5_425_CONV_PRINCIP...
2
4 krb5_425_conv_principal, krb5_425_conv_principal_ext,
5 krb5_524_conv_principal — converts to and from version 4 principals
6
8 Kerberos 5 Library (libkrb5, -lkrb5)
9
11 #include <krb5.h>
12 krb5_error_code
14 krb5_425_conv_principal(krb5_context context, const char *name,
15 const char *instance, const char *realm, krb5_principal *principal);
16 krb5_error_code
18 krb5_425_conv_principal_ext(krb5_context context, const char *name,
19 const char *instance, const char *realm,
20 krb5_boolean (*func)(krb5_context, krb5_principal),
21 krb5_boolean resolve, krb5_principal *principal);
22 krb5_error_code
24 krb5_524_conv_principal(krb5_context context,
25 const krb5_principal principal, char *name, char *instance,
26 char *realm);
27
29 Converting between version 4 and version 5 principals can at best be
30 described as a mess.
31 A version 4 principal consists of a name, an instance, and a realm. A
33 version 5 principal consists of one or more components, and a realm. In
34 some cases also the first component/name will differ between version 4
35 and version 5. Furthermore the second component of a host principal will
36 be the fully qualified domain name of the host in question, while the
37 instance of a version 4 principal will only contain the first part (short
38 hostname). Because of these problems the conversion between principals
39 will have to be site customized.
40 krb5_425_conv_principal_ext() will try to convert a version 4 principal,
42 given by name, instance, and realm, to a version 5 principal. This can
43 result in several possible principals, and if func is non-NULL, it will
44 be called for each candidate principal. func should return true if the
45 principal was “good”. To accomplish this, krb5_425_conv_principal_ext()
46 will look up the name in krb5.conf. It first looks in the
47 v4_name_convert/host subsection, which should contain a list of version 4
48 names whose instance should be treated as a hostname. This list can be
49 specified for each realm (in the realms section), or in the libdefaults
50 section. If the name is found the resulting name of the principal will
51 be the value of this binding. The instance is then first looked up in
52 v4_instance_convert for the specified realm. If found the resulting value
53 will be used as instance (this can be used for special cases), no further
54 attempts will be made to find a conversion if this fails (with func). If
55 the resolve parameter is true, the instance will be looked up with
56 gethostbyname(). This can be a time consuming, error prone, and unsafe
57 operation. Next a list of hostnames will be created from the instance
58 and the v4_domains variable, which should contain a list of possible
59 domains for the specific realm.
60 On the other hand, if the name is not found in a host section, it is
62 looked up in a v4_name_convert/plain binding. If found here the name will
63 be converted, but the instance will be untouched.
64 This list of default host-type conversions is compiled-in:
66 v4_name_convert = {
68 host = {
69 ftp = ftp
70 hprop = hprop
71 imap = imap
72 pop = pop
73 rcmd = host
74 smtp = smtp
75 }
76 }
77 It will only be used if there isn't an entry for these names in the con‐
79 fig file, so you can override these defaults.
80 krb5_425_conv_principal() will call krb5_425_conv_principal_ext() with
82 NULL as func, and the value of v4_instance_resolve (from the libdefaults
83 section) as resolve.
84 krb5_524_conv_principal() basically does the opposite of
86 krb5_425_conv_principal(), it just doesn't have to look up any names, but
87 will instead truncate instances found to belong to a host principal. The
88 name, instance, and realm should be at least 40 characters long.
89
91 Since this is confusing an example is in place.
92 Assume that we have the “foo.com”, and “bar.com” domains that have shared
94 a single version 4 realm, FOO.COM. The version 4 krb.realms file looked
95 like:
96 foo.com FOO.COM
98 .foo.com FOO.COM
99 .bar.com FOO.COM
100 A krb5.conf file that covers this case might look like:
102 [libdefaults]
104 v4_instance_resolve = yes
105 [realms]
106 FOO.COM = {
107 kdc = kerberos.foo.com
108 v4_instance_convert = {
109 foo = foo.com
110 }
111 v4_domains = foo.com
112 }
113 With this setup and the following host table:
115 foo.com
117 a-host.foo.com
118 b-host.bar.com
119 the following conversions will be made:
120 rcmd.a-host -> host/a-host.foo.com
122 ftp.b-host -> ftp/b-host.bar.com
123 pop.foo -> pop/foo.com
124 ftp.other -> ftp/other.foo.com
125 other.a-host -> other/a-host
126 The first three are what you expect. If you remove the “v4_domains”, the
128 fourth entry will result in an error (since the host “other” can't be
129 found). Even if “a-host” is a valid host name, the last entry will not be
130 converted, since the “other” name is not known to represent a host-type
131 principal. If you turn off “v4_instance_resolve” the second example will
132 result in “ftp/b-host.foo.com” (because of the default domain). And all
133 of this is of course only valid if you have working name resolving.
134
136 krb5_build_principal(3), krb5_free_principal(3), krb5_parse_name(3),
137 krb5_sname_to_principal(3), krb5_unparse_name(3), krb5.conf(5)
138HEIMDAL September 3, 2003 HEIMDAL