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kdc: Move fetching krbtgt entry to before enctype selection

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Assists Samba to address CVE-2020-25719

This allows us to use it when validating user-to-user.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14873

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

(Similar to Samba commit f170f1eb4989d7f337eed0f45a558fe5231ea367)
This commit is contained in:
Joseph Sutton
2021-11-16 12:57:47 +13:00
committed by Luke Howard
parent 5cb5b6d748
commit b768c78fca
1 changed files with 40 additions and 40 deletions
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80
kdc/krb5tgs.c
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@@ -1665,6 +1665,46 @@ server_lookup:
else
rsp = sp;
/*
* Now refetch the primary krbtgt, and get the current kvno (the
* sign check may have been on an old kvno, and the server may
* have been an incoming trust)
*/
ret = krb5_make_principal(context,
&krbtgt_out_principal,
our_realm,
KRB5_TGS_NAME,
our_realm,
NULL);
if (ret) {
kdc_log(context, config, 4,
"Failed to make krbtgt principal name object for "
"authz-data signatures");
goto out;
}
ret = krb5_unparse_name(context, krbtgt_out_principal, &krbtgt_out_n);
if (ret) {
kdc_log(context, config, 4,
"Failed to make krbtgt principal name object for "
"authz-data signatures");
goto out;
}
ret = _kdc_db_fetch(context, config, krbtgt_out_principal,
HDB_F_GET_KRBTGT, NULL, NULL, &krbtgt_out);
if (ret) {
char *ktpn = NULL;
ret = krb5_unparse_name(context, krbtgt->entry.principal, &ktpn);
kdc_log(context, config, 4,
"No such principal %s (needed for authz-data signature keys) "
"while processing TGS-REQ for service %s with krbtg %s",
krbtgt_out_n, spn, (ret == 0) ? ktpn : "<unknown>");
free(ktpn);
ret = KRB5KRB_AP_ERR_NOT_US;
goto out;
}
/*
* Select enctype, return key and kvno.
*/
@@ -1727,46 +1767,6 @@ server_lookup:
* backward.
*/
/*
* Now refetch the primary krbtgt, and get the current kvno (the
* sign check may have been on an old kvno, and the server may
* have been an incoming trust)
*/
ret = krb5_make_principal(context,
&krbtgt_out_principal,
our_realm,
KRB5_TGS_NAME,
our_realm,
NULL);
if (ret) {
kdc_log(context, config, 4,
"Failed to make krbtgt principal name object for "
"authz-data signatures");
goto out;
}
ret = krb5_unparse_name(context, krbtgt_out_principal, &krbtgt_out_n);
if (ret) {
kdc_log(context, config, 4,
"Failed to make krbtgt principal name object for "
"authz-data signatures");
goto out;
}
ret = _kdc_db_fetch(context, config, krbtgt_out_principal,
HDB_F_GET_KRBTGT, NULL, NULL, &krbtgt_out);
if (ret) {
char *ktpn = NULL;
ret = krb5_unparse_name(context, krbtgt->entry.principal, &ktpn);
kdc_log(context, config, 4,
"No such principal %s (needed for authz-data signature keys) "
"while processing TGS-REQ for service %s with krbtg %s",
krbtgt_out_n, spn, (ret == 0) ? ktpn : "<unknown>");
free(ktpn);
ret = KRB5KRB_AP_ERR_NOT_US;
goto out;
}
/*
* The first realm is the realm of the service, the second is
* krbtgt/<this>/@REALM component of the krbtgt DN the request was