int
mm_answer_gss_setup_ctx(int sock, struct sshbuf *m)
{
gss_OID_desc goid;
OM_uint32 major;
size_t len;
u_char *p;
int r;
if ((r = sshbuf_get_string(m, &p, &len)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
goid.elements = p;
goid.length = len;
major = ssh_gssapi_server_ctx(&gsscontext, &goid);
free(goid.elements);
sshbuf_reset(m);
if ((r = sshbuf_put_u32(m, major)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
mm_request_send(sock, MONITOR_ANS_GSSSETUP, m);
/* Now we have a context, enable the step */
monitor_permit(mon_dispatch, MONITOR_REQ_GSSSTEP, 1);
return (0);
}
int
mm_answer_gss_setup_ctx(int sock, Buffer *m)
{
gss_OID_desc goid;
OM_uint32 major;
u_int len;
if (!options.gss_authentication)
fatal("%s: GSSAPI authentication not enabled", __func__);
goid.elements = buffer_get_string(m, &len);
goid.length = len;
major = ssh_gssapi_server_ctx(&gsscontext, &goid);
free(goid.elements);
buffer_clear(m);
buffer_put_int(m, major);
mm_request_send(sock, MONITOR_ANS_GSSSETUP, m);
/* Now we have a context, enable the step */
monitor_permit(mon_dispatch, MONITOR_REQ_GSSSTEP, 1);
return (0);
}
/* Unprivileged */
int
ssh_gssapi_server_check_mech(gss_OID oid, void *data) {
Gssctxt * ctx = NULL;
int res;
res = !GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctx, oid)));
ssh_gssapi_delete_ctx(&ctx);
return (res);
}
/* Unprivileged */
int
ssh_gssapi_server_check_mech(Gssctxt **dum, gss_OID oid, const char *data,
const char *dummy) {
Gssctxt *ctx = NULL;
int res;
res = !GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctx, oid)));
ssh_gssapi_delete_ctx(&ctx);
return (res);
}
/*
* We only support those mechanisms that we know about (ie ones that we know
* how to check local user kuserok and the like)
*/
static int
userauth_gssapi(Authctxt *authctxt)
{
gss_OID_desc goid = {0, NULL};
Gssctxt *ctxt = NULL;
int mechs;
int present;
OM_uint32 ms;
u_int len;
u_char *doid = NULL;
if (!authctxt->valid || authctxt->user == NULL)
return (0);
mechs = packet_get_int();
if (mechs == 0) {
debug("Mechanism negotiation is not supported");
return (0);
}
do {
mechs--;
free(doid);
present = 0;
doid = packet_get_string(&len);
if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
doid[1] == len - 2) {
goid.elements = doid + 2;
goid.length = len - 2;
ssh_gssapi_test_oid_supported(&ms, &goid, &present);
} else {
logit("Badly formed OID received");
}
} while (mechs > 0 && !present);
if (!present) {
free(doid);
authctxt->server_caused_failure = 1;
return (0);
}
if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
if (ctxt != NULL)
ssh_gssapi_delete_ctx(&ctxt);
free(doid);
authctxt->server_caused_failure = 1;
return (0);
}
authctxt->methoddata = (void *)ctxt;
packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
/* Return the OID that we received */
packet_put_string(doid, len);
packet_send();
free(doid);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
authctxt->postponed = 1;
return (0);
}
void
kexgss_server(Kex *kex)
{
OM_uint32 maj_status, min_status;
/*
* Some GSSAPI implementations use the input value of ret_flags (an
* output variable) as a means of triggering mechanism specific
* features. Initializing it to zero avoids inadvertently
* activating this non-standard behaviour.
*/
OM_uint32 ret_flags = 0;
gss_buffer_desc gssbuf, recv_tok, msg_tok;
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
Gssctxt *ctxt = NULL;
u_int slen, klen, kout, hashlen;
u_char *kbuf, *hash;
DH *dh;
int min = -1, max = -1, nbits = -1;
BIGNUM *shared_secret = NULL;
BIGNUM *dh_client_pub = NULL;
int type = 0;
gss_OID oid;
char *mechs;
/* Initialise GSSAPI */
/* If we're rekeying, privsep means that some of the private structures
* in the GSSAPI code are no longer available. This kludges them back
* into life
*/
if (!ssh_gssapi_oid_table_ok())
if ((mechs = ssh_gssapi_server_mechanisms()))
xfree(mechs);
debug2("%s: Identifying %s", __func__, kex->name);
oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type);
if (oid == GSS_C_NO_OID)
fatal("Unknown gssapi mechanism");
debug2("%s: Acquiring credentials", __func__);
if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid))))
fatal("Unable to acquire credentials for the server");
switch (kex->kex_type) {
case KEX_GSS_GRP1_SHA1:
dh = dh_new_group1();
break;
case KEX_GSS_GRP14_SHA1:
dh = dh_new_group14();
break;
case KEX_GSS_GEX_SHA1:
debug("Doing group exchange");
packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ);
min = packet_get_int();
nbits = packet_get_int();
max = packet_get_int();
min = MAX(DH_GRP_MIN, min);
max = MIN(DH_GRP_MAX, max);
packet_check_eom();
if (max < min || nbits < min || max < nbits)
fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
min, nbits, max);
dh = PRIVSEP(choose_dh(min, nbits, max));
if (dh == NULL)
packet_disconnect("Protocol error: no matching group found");
packet_start(SSH2_MSG_KEXGSS_GROUP);
packet_put_bignum2(dh->p);
packet_put_bignum2(dh->g);
packet_send();
packet_write_wait();
break;
default:
fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
}
dh_gen_key(dh, kex->we_need * 8);
do {
debug("Wait SSH2_MSG_GSSAPI_INIT");
type = packet_read();
switch(type) {
case SSH2_MSG_KEXGSS_INIT:
if (dh_client_pub != NULL)
fatal("Received KEXGSS_INIT after initialising");
recv_tok.value = packet_get_string(&slen);
recv_tok.length = slen;
if ((dh_client_pub = BN_new()) == NULL)
fatal("dh_client_pub == NULL");
packet_get_bignum2(dh_client_pub);
/* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
break;
case SSH2_MSG_KEXGSS_CONTINUE:
recv_tok.value = packet_get_string(&slen);
recv_tok.length = slen;
break;
default:
packet_disconnect(
"Protocol error: didn't expect packet type %d",
type);
}
maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok,
&send_tok, &ret_flags));
xfree(recv_tok.value);
if (maj_status != GSS_S_COMPLETE && send_tok.length == 0)
fatal("Zero length token output when incomplete");
if (dh_client_pub == NULL)
fatal("No client public key");
if (maj_status & GSS_S_CONTINUE_NEEDED) {
debug("Sending GSSAPI_CONTINUE");
packet_start(SSH2_MSG_KEXGSS_CONTINUE);
packet_put_string(send_tok.value, send_tok.length);
packet_send();
gss_release_buffer(&min_status, &send_tok);
}
} while (maj_status & GSS_S_CONTINUE_NEEDED);
if (GSS_ERROR(maj_status)) {
if (send_tok.length > 0) {
packet_start(SSH2_MSG_KEXGSS_CONTINUE);
packet_put_string(send_tok.value, send_tok.length);
packet_send();
}
fatal("accept_ctx died");
}
if (!(ret_flags & GSS_C_MUTUAL_FLAG))
fatal("Mutual Authentication flag wasn't set");
if (!(ret_flags & GSS_C_INTEG_FLAG))
fatal("Integrity flag wasn't set");
if (!dh_pub_is_valid(dh, dh_client_pub))
packet_disconnect("bad client public DH value");
klen = DH_size(dh);
kbuf = xmalloc(klen);
kout = DH_compute_key(kbuf, dh_client_pub, dh);
if (kout < 0)
fatal("DH_compute_key: failed");
shared_secret = BN_new();
if (shared_secret == NULL)
fatal("kexgss_server: BN_new failed");
if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
fatal("kexgss_server: BN_bin2bn failed");
memset(kbuf, 0, klen);
xfree(kbuf);
switch (kex->kex_type) {
case KEX_GSS_GRP1_SHA1:
case KEX_GSS_GRP14_SHA1:
kex_dh_hash(
kex->client_version_string, kex->server_version_string,
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
buffer_ptr(&kex->my), buffer_len(&kex->my),
NULL, 0, /* Change this if we start sending host keys */
dh_client_pub, dh->pub_key, shared_secret,
&hash, &hashlen
);
break;
case KEX_GSS_GEX_SHA1:
kexgex_hash(
kex->evp_md,
kex->client_version_string, kex->server_version_string,
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
buffer_ptr(&kex->my), buffer_len(&kex->my),
NULL, 0,
min, nbits, max,
dh->p, dh->g,
dh_client_pub,
dh->pub_key,
shared_secret,
&hash, &hashlen
);
break;
default:
fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
}
BN_clear_free(dh_client_pub);
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = xmalloc(kex->session_id_len);
memcpy(kex->session_id, hash, kex->session_id_len);
}
gssbuf.value = hash;
gssbuf.length = hashlen;
if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok))))
fatal("Couldn't get MIC");
packet_start(SSH2_MSG_KEXGSS_COMPLETE);
packet_put_bignum2(dh->pub_key);
packet_put_string(msg_tok.value,msg_tok.length);
if (send_tok.length != 0) {
packet_put_char(1); /* true */
packet_put_string(send_tok.value, send_tok.length);
} else {
packet_put_char(0); /* false */
}
packet_send();
gss_release_buffer(&min_status, &send_tok);
gss_release_buffer(&min_status, &msg_tok);
if (gss_kex_context == NULL)
gss_kex_context = ctxt;
else
ssh_gssapi_delete_ctx(&ctxt);
DH_free(dh);
kex_derive_keys(kex, hash, hashlen, shared_secret);
BN_clear_free(shared_secret);
kex_finish(kex);
/* If this was a rekey, then save out any delegated credentials we
* just exchanged. */
if (options.gss_store_rekey)
ssh_gssapi_rekey_creds();
}
/*
* We only support those mechanisms that we know about (ie ones that we know
* how to check local user kuserok and the like
*/
static int
userauth_gssapi(Authctxt *authctxt)
{
gss_OID_desc oid = {0, NULL};
Gssctxt *ctxt = NULL;
int mechs;
gss_OID_set supported;
int present;
OM_uint32 ms;
u_int len;
char *doid = NULL;
if (!authctxt->valid || authctxt->user == NULL)
return (0);
mechs = packet_get_int();
if (mechs == 0) {
debug("Mechanism negotiation is not supported");
return (0);
}
ssh_gssapi_supported_oids(&supported);
do {
mechs--;
if (doid)
xfree(doid);
doid = packet_get_string(&len);
if (doid[0] != SSH_GSS_OIDTYPE || doid[1] != len-2) {
logit("Mechanism OID received using the old encoding form");
oid.elements = doid;
oid.length = len;
} else {
oid.elements = doid + 2;
oid.length = len - 2;
}
gss_test_oid_set_member(&ms, &oid, supported, &present);
} while (mechs > 0 && !present);
gss_release_oid_set(&ms, &supported);
if (!present) {
xfree(doid);
return (0);
}
if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &oid)))) {
xfree(doid);
return (0);
}
authctxt->methoddata=(void *)ctxt;
packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
/* Return OID in same format as we received it*/
packet_put_string(doid, len);
packet_send();
xfree(doid);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
authctxt->postponed = 1;
return (0);
}
/*
* We only support those mechanisms that we know about (ie ones that we know
* how to check local user kuserok and the like)
*/
static int
userauth_gssapi(struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
gss_OID_desc goid = {0, NULL};
Gssctxt *ctxt = NULL;
int r, present;
u_int mechs;
OM_uint32 ms;
size_t len;
u_char *doid = NULL;
if ((r = sshpkt_get_u32(ssh, &mechs)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
if (mechs == 0) {
debug("Mechanism negotiation is not supported");
return (0);
}
do {
mechs--;
free(doid);
present = 0;
if ((r = sshpkt_get_string(ssh, &doid, &len)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
doid[1] == len - 2) {
goid.elements = doid + 2;
goid.length = len - 2;
ssh_gssapi_test_oid_supported(&ms, &goid, &present);
} else {
logit("Badly formed OID received");
}
} while (mechs > 0 && !present);
if (!present) {
free(doid);
authctxt->server_caused_failure = 1;
return (0);
}
if (!authctxt->valid || authctxt->user == NULL) {
debug2("%s: disabled because of invalid user", __func__);
free(doid);
return (0);
}
if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
if (ctxt != NULL)
ssh_gssapi_delete_ctx(&ctxt);
free(doid);
authctxt->server_caused_failure = 1;
return (0);
}
authctxt->methoddata = (void *)ctxt;
/* Return the OID that we received */
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE)) != 0 ||
(r = sshpkt_put_string(ssh, doid, len)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
free(doid);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
authctxt->postponed = 1;
return (0);
}
