Our initiator supports configuration-driven delegation of destination
TGTs.
This commit adds acceptor-side handling of destination TGT policy to
reject storing of non-destination TGTs when destination TGTs are
desired.
Currently we use the same appdefault for this.
Background:
    A root TGT is one of the form krbtgt/REALM@SAME-REALM.
    A destination TGT is a root TGT for the same realm as the acceptor
    service's realm.
    Normally clients delegate a root TGT for the client's realm.
    In some deployments clients may want to delegate destination TGTs as
    a form of constrained delegation: so that the destination service
    cannot use the delegated credential to impersonate the client
    principal to services in its home realm (due to KDC lineage/transit
    checks).  In those deployments there may not even be a route back to
    the KDCs of the client's realm, and attempting to use a
    non-destination TGT might even lead to timeouts.
		
	
		
			
				
	
	
		
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			5.4 KiB
		
	
	
	
		
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			169 lines
		
	
	
		
			5.4 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
/*
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 * Copyright (c) 2018 Kungliga Tekniska Högskolan
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 * (Royal Institute of Technology, Stockholm, Sweden).
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 *
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 *
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 * 3. Neither the name of the Institute nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include "gsskrb5_locl.h"
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OM_uint32 GSSAPI_CALLCONV _gsskrb5_duplicate_cred (
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     OM_uint32           *minor_status,
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     gss_const_cred_id_t input_cred_handle,
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     gss_cred_id_t       *output_cred_handle)
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{
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    krb5_context context;
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    gsskrb5_cred cred, dup;
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    OM_uint32 major, junk;
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    dup = NULL;
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    if (output_cred_handle == NULL) {
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        *minor_status = EINVAL;
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        return GSS_S_CALL_INACCESSIBLE_WRITE;
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    }
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    GSSAPI_KRB5_INIT (&context);
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    if (input_cred_handle == GSS_C_NO_CREDENTIAL) {
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        /* Duplicate the default credential */
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        return _gsskrb5_acquire_cred_from(minor_status, GSS_C_NO_NAME,
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					  GSS_C_INDEFINITE,
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					  GSS_C_NO_OID_SET,
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					  GSS_C_BOTH,
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					  GSS_C_NO_CRED_STORE,
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					  output_cred_handle,
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					  NULL, NULL);
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    }
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    /* Duplicate the input credential */
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    dup = calloc(1, sizeof(*dup));
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    if (dup == NULL) {
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        *minor_status = krb5_enomem(context);
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        return (GSS_S_FAILURE);
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    }
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    *output_cred_handle = (gss_cred_id_t)dup; /* making sure to release on error */
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    cred = (gsskrb5_cred)input_cred_handle;
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    HEIMDAL_MUTEX_lock(&cred->cred_id_mutex);
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    dup->destination_realm = NULL;
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    if (cred->destination_realm &&
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        (dup->destination_realm = strdup(cred->destination_realm)) == NULL) {
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        *minor_status = krb5_enomem(context);
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        free(dup);
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        return (GSS_S_FAILURE);
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    }
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    dup->usage = cred->usage;
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    dup->endtime = cred->endtime;
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    dup->principal = NULL;
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    dup->keytab = NULL;
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    dup->ccache = NULL;
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    dup->mechanisms = NULL;
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    major = GSS_S_FAILURE;
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    HEIMDAL_MUTEX_init(&dup->cred_id_mutex);
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    *minor_status = krb5_copy_principal(context, cred->principal,
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                                        &dup->principal);
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    if (*minor_status)
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        goto fail;
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    if (cred->keytab) {
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        char *name = NULL;
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        *minor_status = krb5_kt_get_full_name(context, cred->keytab, &name);
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        if (*minor_status)
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            goto fail;
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        *minor_status = krb5_kt_resolve(context, name, &dup->keytab);
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        krb5_xfree(name);
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        if (*minor_status)
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            goto fail;
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    }
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    if (cred->ccache) {
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        const char *type, *name;
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        char *type_name = NULL;
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        type = krb5_cc_get_type(context, cred->ccache); /* can't fail */
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        if (strcmp(type, "MEMORY") == 0) {
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            *minor_status = krb5_cc_new_unique(context, type, NULL,
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                                               &dup->ccache);
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            if (*minor_status)
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                goto fail;
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            *minor_status = krb5_cc_copy_cache(context, cred->ccache,
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                                               dup->ccache);
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            if (*minor_status)
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                goto fail;
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        } else {
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            name = krb5_cc_get_name(context, cred->ccache);
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            if (name == NULL) {
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                *minor_status = ENOMEM;
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                goto fail;
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            }
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            if (asprintf(&type_name, "%s:%s", type, name) == -1 ||
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                type_name == NULL) {
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                *minor_status = ENOMEM;
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                goto fail;
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            }
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            *minor_status = krb5_cc_resolve(context, type_name,
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                                            &dup->ccache);
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            free(type_name);
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            if (*minor_status)
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                goto fail;
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        }
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    }
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    major = gss_create_empty_oid_set(minor_status, &dup->mechanisms);
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    if (major != GSS_S_COMPLETE)
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        goto fail;
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    major = gss_add_oid_set_member(minor_status, GSS_KRB5_MECHANISM,
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                                   &dup->mechanisms);
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    if (major != GSS_S_COMPLETE)
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        goto fail;
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    HEIMDAL_MUTEX_unlock(&cred->cred_id_mutex);
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    *output_cred_handle = (gss_cred_id_t)dup;
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    *minor_status = 0;
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    return major;
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fail:
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    HEIMDAL_MUTEX_unlock(&cred->cred_id_mutex);
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    *output_cred_handle = (gss_cred_id_t)dup;
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    _gsskrb5_release_cred(&junk, output_cred_handle);
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    return major;
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}
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