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Add kx509 client and revamp kx509 service

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This commit adds support for kx509 in libkrb5, and revamps the KDC's
kx509 service (fixing bugs, adding features).

Of note is that kx509 is attempted optimistically by the client, with
the certificate and private key stored in the ccache, and optionally in
an external PEM or DER file.

NOTE: We do not optimistically use kx509 in krb5_cc_store_cred() if the
      ccache is a MEMORY ccache so we don't generate a key when
      accepting a GSS context with a delegated credential.

kx509 protocol issues to be fixed in an upcoming commit:

 - no proof of possession (this is mostly not too bad, but we'll want to
   fix it by using CSRs)
 - no algorithm agility (only plain RSA is supported)
 - very limited (no way to request any options in regards to the
   requested cert)
 - error codes are not very useful

Things we're adding in this commit:

 - libkrb5 kx509 client
 - automatic kx509 usage hooked in via krb5_cc_store_cred() of start TGT
 - per-realm templates on the KDC side
 - per-realm issuer certificates
 - send error messages on the KDC side
   (this is essential to avoid client-side timeouts on error)
 - authenticate as many error messages
 - add a protocol probe feature so we can avoid generating a
   keypair if the service is not enabled
   (once we add support for ECC algorithms we won't need this
    anymore; the issue is that RSA keygen is slow)
 - support for different types of client principals, not just username:

    - host-based service and domain-based service, each with its own
      template set per-{realm, service} or per-service

   (the idea is to support issuance of server certificates too, not
    just client/user certs)
 - more complete support for SAN types
 - tests (including that PKINIT->kx509->PKINIT works, which makes it
   possible to have "delegation" of PKIX credentials by just delegating
   Kerberos credentials)
 - document the protocol in lib/krb5/kx509.c

Future work:

 - add option for longer-ticket-lifetime service certs
 - add support for ECDSA, and some day for ed25519 and ed448
 - reuse private key when running kinit
   (this will require rethinking how we trigger optimistic kx509
    usage)
 - HDB lookup for:
    - optional revocation check (not strictly necessary)
    - adding to certificates those SANs listed in HDB
       - hostname aliases (dNSName SANs)
       - rfc822Name (email)
       - XMPP SANs
       - id-pkinit-san (a user could have aliases too)
 - support username wild-card A RRs, ala OSKT/krb5_admin
    i.e., if a host/f.q.d.n principal asks for a certificate for
    some service at some-label.f.q.d.n, then issue it
   (this is not needed at OSKT sites because OSKT already
    supports keying such service principals, which means kx509
    will issue certificates for them, however, it would be nice
    to be able to have this independent of OSKT)
   (a better way to do this would be to integrate more of OSKT
    into Heimdal proper)
 - a kx509 command, or heimtools kx509 subcommand for explicitly
   attempting use of the kx509 protocol (as opposed to implicit, as is
   done in kinit via krb5_cc_store_cred() magic right now)

Issues:

 - optimistically trying kx509 on start realm TGT store -> timeout issues!
    - newer KDCs will return errors because of this commit; older ones
      will not, which causes timouts
    - need a separate timeout setting for kx509 for optimistic case
    - need a [realm] config item and DNS SRV RR lookup for whether a
      realm is expected to support kx509 service
This commit is contained in:
Nicolas Williams
2019-06-17 19:34:21 -05:00
parent 78cb995e6e
commit 6a7e7eace6
23 changed files with 2729 additions and 263 deletions
Download Patch File Download Diff File Expand all files Collapse all files

126
kuser/klist.c
View File

@@ -36,6 +36,10 @@
#include "kuser_locl.h"
#include "parse_units.h"
#include "heimtools-commands.h"
#include <kx509_asn1.h>
#undef HC_DEPRECATED_CRYPTO
#include "../lib/hx509/hx_locl.h"
#include "hx509-private.h"
static char*
printable_time_internal(time_t t, int x)
@@ -173,6 +177,7 @@ print_cred_verbose(krb5_context context, krb5_creds *cred, int do_json)
strcmp(s, "FriendlyName") == 0 ||
strcmp(s, "fast_avail") == 0 ||
strcmp(s, "kx509store") == 0 ||
strcmp(s, "kx509_service_realm") == 0 ||
strcmp(s, "kx509_service_status") == 0)
printf(N_("Configuration item payload: %.*s\n", ""),
(int)cred->ticket.length,
@@ -253,22 +258,34 @@ print_cred_verbose(krb5_context context, krb5_creds *cred, int do_json)
*/
static void
print_tickets (krb5_context context,
krb5_ccache ccache,
krb5_principal principal,
int do_verbose,
int do_flags,
int do_hidden,
int do_json)
print_tickets(krb5_context context,
krb5_ccache ccache,
krb5_principal principal,
int do_verbose,
int do_flags,
int do_hidden,
int do_json,
const char *hx509_store)
{
char *str, *name, *fullname;
char *kx509_realm = NULL;
hx509_private_key key = NULL;
hx509_context hx509ctx = NULL;
hx509_certs certs = NULL;
hx509_cert cert = NULL;
krb5_error_code kx509_ret = 0;
krb5_error_code ret;
krb5_cc_cursor cursor;
krb5_creds creds;
krb5_deltat sec;
int print_comma = 0;
rtbl_t ct = NULL;
int print_comma = 0;
int kx509_disabled = 0;
int cert_stored = 0;
int cert_seen = 0;
if (hx509_store)
kx509_ret = hx509_context_init(&hx509ctx);
ret = krb5_unparse_name (context, principal, &str);
if (ret)
@@ -341,6 +358,45 @@ print_tickets (krb5_context context,
if (do_verbose && do_json)
printf("\"tickets\" : [");
while ((ret = krb5_cc_next_cred(context, ccache, &cursor, &creds)) == 0) {
if (krb5_is_config_principal(context, creds.server) &&
krb5_principal_get_num_comp(context, creds.server) == 2 &&
hx509_store) {
const char *s;
s = krb5_principal_get_comp_string(context, creds.server, 1);
if (strcmp(s, "kx509_service_status") == 0) {
kx509_disabled = 1;
} else if (strcmp(s, "kx509_service_realm") == 0) {
kx509_realm = strndup(creds.ticket.data, creds.ticket.length);
} else if (strcmp(s, "kx509cert") == 0) {
cert = hx509_cert_init_data(hx509ctx, creds.ticket.data,
creds.ticket.length, NULL);
} else if (strcmp(s, "kx509key") == 0) {
(void) hx509_parse_private_key(hx509ctx, NULL,
creds.ticket.data,
creds.ticket.length,
HX509_KEY_FORMAT_PKCS8, &key);
}
if (hx509ctx && cert && key && !cert_seen) {
/* Now store the cert and key into the given hx509 store */
(void) _hx509_cert_assign_key(cert, key);
kx509_ret = hx509_certs_init(hx509ctx, hx509_store,
HX509_CERTS_CREATE, NULL, &certs);
if (kx509_ret == 0)
kx509_ret = hx509_certs_add(hx509ctx, certs, cert);
if (kx509_ret == 0)
kx509_ret = hx509_certs_store(hx509ctx, certs, 0, NULL);
/*
* Wait till we're done listing the ccache to complain about
* failing to extract the cert and priv key.
*/
cert_seen = 1;
if (kx509_ret == 0)
cert_stored = 1;
}
}
if (!do_hidden && krb5_is_config_principal(context, creds.server)) {
;
} else if (do_verbose) {
@@ -353,12 +409,47 @@ print_tickets (krb5_context context,
}
krb5_free_cred_contents(context, &creds);
}
print_comma = 0;
if(ret != KRB5_CC_END)
if (ret != KRB5_CC_END)
krb5_err(context, 1, ret, "krb5_cc_get_next");
ret = krb5_cc_end_seq_get (context, ccache, &cursor);
if (ret)
krb5_err (context, 1, ret, "krb5_cc_end_seq_get");
krb5_err(context, 1, ret, "krb5_cc_end_seq_get");
/* Finish kx509 extraction error checking */
if (hx509_store && cert_seen && !cert_stored) {
if (!hx509ctx)
krb5_err(context, 1, kx509_ret,
N_("Failed to store certificate and private key "
"in %s due to failure to initialize context: %s", ""),
hx509_store, hx509_get_error_string(hx509ctx, kx509_ret));
if (!cert || !key)
krb5_err(context, 1, kx509_ret,
N_("Failed to store certificate and private key "
"in %s due to failure to parse them: %s", ""),
hx509_store, hx509_get_error_string(hx509ctx, kx509_ret));
krb5_err(context, 1, kx509_ret, N_("Failed to store certificate and "
"private key in %s", ""),
hx509_store);
}
if (hx509_store && !cert_seen) {
/* No PKIX creds in ccache, but maybe we can run kx509 now */
if (kx509_disabled)
krb5_errx(context, 1, N_("The kx509 protocol is disabled at the "
"KDC for realm %s", ""),
kx509_realm ? kx509_realm : "<out of memory>");
ret = krb5_kx509_ext(context, ccache, NULL, NULL, NULL, 0, hx509_store,
NULL);
if (ret)
krb5_err(context, 1, ret, N_("Failed to acquire certificate and "
"store it and private key in %s", ""),
hx509_store);
}
hx509_private_key_free(&key);
hx509_certs_free(&certs);
hx509_cert_free(cert);
hx509_context_free(&hx509ctx);
print_comma = 0;
if(!do_verbose) {
rtbl_format(ct, stdout);
rtbl_destroy(ct);
@@ -368,6 +459,7 @@ print_tickets (krb5_context context,
printf("]");
printf("}");
}
free(fullname);
}
/*
@@ -474,7 +566,7 @@ static int
display_v5_ccache (krb5_context context, krb5_ccache ccache,
int do_test, int do_verbose,
int do_flags, int do_hidden,
int do_json)
int do_json, const char *hx509_store)
{
krb5_error_code ret;
krb5_principal principal;
@@ -499,7 +591,7 @@ display_v5_ccache (krb5_context context, krb5_ccache ccache,
exit_status = check_expiration(context, ccache, NULL);
else
print_tickets (context, ccache, principal, do_verbose,
do_flags, do_hidden, do_json);
do_flags, do_hidden, do_json, hx509_store);
ret = krb5_cc_close (context, ccache);
if (ret)
@@ -646,7 +738,8 @@ klist(struct klist_options *opt, int argc, char **argv)
exit_status |= display_v5_ccache(heimtools_context, id, do_test,
do_verbose, opt->flags_flag,
opt->hidden_flag, opt->json_flag);
opt->hidden_flag, opt->json_flag,
opt->extract_kx509_cert_string);
if (!opt->json_flag)
printf("\n\n");
@@ -667,7 +760,8 @@ klist(struct klist_options *opt, int argc, char **argv)
}
exit_status = display_v5_ccache(heimtools_context, id, do_test,
do_verbose, opt->flags_flag,
opt->hidden_flag, opt->json_flag);
opt->hidden_flag, opt->json_flag,
opt->extract_kx509_cert_string);
}
}