int
ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
{
gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
OM_uint32 major, minor;
gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
/* RFC 4462 says we MUST NOT do SPNEGO */
if (oid->length == spnego_oid.length &&
(memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
return 0; /* false */
ssh_gssapi_build_ctx(ctx);
ssh_gssapi_set_oid(*ctx, oid);
major = ssh_gssapi_import_name(*ctx, host);
if (!GSS_ERROR(major)) {
major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
NULL);
gss_release_buffer(&minor, &token);
if ((*ctx)->context != GSS_C_NO_CONTEXT)
gss_delete_sec_context(&minor, &(*ctx)->context,
GSS_C_NO_BUFFER);
}
if (GSS_ERROR(major))
ssh_gssapi_delete_ctx(ctx);
return (!GSS_ERROR(major));
}
/* Privileged (called from ssh_gssapi_server_ctx) */
static OM_uint32
ssh_gssapi_acquire_cred(Gssctxt *ctx)
{
OM_uint32 status;
char lname[NI_MAXHOST];
gss_OID_set oidset;
if (options.gss_strict_acceptor) {
gss_create_empty_oid_set(&status, &oidset);
gss_add_oid_set_member(&status, ctx->oid, &oidset);
if (gethostname(lname, MAXHOSTNAMELEN)) {
gss_release_oid_set(&status, &oidset);
return (-1);
}
if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
gss_release_oid_set(&status, &oidset);
return (ctx->major);
}
if ((ctx->major = gss_acquire_cred(&ctx->minor,
ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds,
NULL, NULL)))
ssh_gssapi_error(ctx);
gss_release_oid_set(&status, &oidset);
return (ctx->major);
} else {
ctx->name = GSS_C_NO_NAME;
ctx->creds = GSS_C_NO_CREDENTIAL;
}
return GSS_S_COMPLETE;
}
/* Privileged (called from ssh_gssapi_server_ctx) */
static OM_uint32
ssh_gssapi_acquire_cred(Gssctxt *ctx)
{
OM_uint32 status;
char lname[NI_MAXHOST];
gss_OID_set oidset;
gss_create_empty_oid_set(&status, &oidset);
gss_add_oid_set_member(&status, ctx->oid, &oidset);
if (gethostname(lname, sizeof(lname))) {
gss_release_oid_set(&status, &oidset);
return (-1);
}
if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
gss_release_oid_set(&status, &oidset);
return (ctx->major);
}
if ((ctx->major = gss_acquire_cred(&ctx->minor,
ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL)))
ssh_gssapi_error(ctx);
gss_release_oid_set(&status, &oidset);
return (ctx->major);
}
/*
* Wrapper to init_sec_context. Requires that the context contains:
*
* oid
* server name (from ssh_gssapi_import_name)
*/
OM_uint32
ssh_gssapi_init_ctx(Gssctxt *ctx, const char *server_host, int deleg_creds,
gss_buffer_t recv_tok, gss_buffer_t send_tok)
{
int flags = GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG;
debug("%s(%p, %s, %d, %p, %p)", __func__, ctx, server_host,
deleg_creds, recv_tok, send_tok);
if (deleg_creds) {
flags |= GSS_C_DELEG_FLAG;
debug("Delegating GSS-API credentials");
}
/* Build target principal */
if (ctx->desired_name == GSS_C_NO_NAME &&
!ssh_gssapi_import_name(ctx, server_host)) {
return (ctx->major);
}
ctx->major = gss_init_sec_context(&ctx->minor, GSS_C_NO_CREDENTIAL,
&ctx->context, ctx->desired_name, ctx->desired_mech, flags,
0, /* default lifetime */
NULL, /* no channel bindings */
recv_tok,
NULL, /* actual mech type */
send_tok, &ctx->flags,
NULL); /* actual lifetime */
if (GSS_ERROR(ctx->major))
ssh_gssapi_error(ctx, "calling GSS_Init_sec_context()");
return (ctx->major);
}
int
ssh_gssapi_check_mechanism(gss_OID oid, const char *host)
{
Gssctxt * ctx = NULL;
gss_buffer_desc token;
OM_uint32 major,minor;
ssh_gssapi_build_ctx(&ctx);
ssh_gssapi_set_oid(ctx,oid);
ssh_gssapi_import_name(ctx, (char *) host);
major=ssh_gssapi_init_ctx(ctx,0, GSS_C_NO_BUFFER, &token, NULL);
gss_release_buffer(&minor,&token);
ssh_gssapi_delete_ctx(&ctx);
return(!GSS_ERROR(major));
}
void
kexgss_client(Kex *kex) {
gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
gss_buffer_desc recv_tok, gssbuf, msg_tok, *token_ptr;
Gssctxt *ctxt;
OM_uint32 maj_status, min_status, ret_flags;
u_int klen, kout, slen = 0, hashlen, strlen;
DH *dh;
BIGNUM *dh_server_pub = NULL;
BIGNUM *shared_secret = NULL;
BIGNUM *p = NULL;
BIGNUM *g = NULL;
u_char *kbuf, *hash;
u_char *serverhostkey = NULL;
u_char *empty = "";
char *msg;
char *lang;
int type = 0;
int first = 1;
int nbits = 0, min = DH_GRP_MIN, max = DH_GRP_MAX;
/* Initialise our GSSAPI world */
ssh_gssapi_build_ctx(&ctxt);
if (ssh_gssapi_id_kex(ctxt, kex->name, kex->kex_type)
== GSS_C_NO_OID)
fatal("Couldn't identify host exchange");
if (ssh_gssapi_import_name(ctxt, kex->gss_host))
fatal("Couldn't import hostname");
if (kex->gss_client &&
ssh_gssapi_client_identity(ctxt, kex->gss_client))
fatal("Couldn't acquire client credentials");
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\n");
nbits = dh_estimate(kex->we_need * 8);
packet_start(SSH2_MSG_KEXGSS_GROUPREQ);
packet_put_int(min);
packet_put_int(nbits);
packet_put_int(max);
packet_send();
packet_read_expect(SSH2_MSG_KEXGSS_GROUP);
if ((p = BN_new()) == NULL)
fatal("BN_new() failed");
packet_get_bignum2(p);
if ((g = BN_new()) == NULL)
fatal("BN_new() failed");
packet_get_bignum2(g);
packet_check_eom();
if (BN_num_bits(p) < min || BN_num_bits(p) > max)
fatal("GSSGRP_GEX group out of range: %d !< %d !< %d",
min, BN_num_bits(p), max);
dh = dh_new_group(g, p);
break;
default:
fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
}
/* Step 1 - e is dh->pub_key */
dh_gen_key(dh, kex->we_need * 8);
/* This is f, we initialise it now to make life easier */
dh_server_pub = BN_new();
if (dh_server_pub == NULL)
fatal("dh_server_pub == NULL");
token_ptr = GSS_C_NO_BUFFER;
do {
debug("Calling gss_init_sec_context");
maj_status = ssh_gssapi_init_ctx(ctxt,
kex->gss_deleg_creds, token_ptr, &send_tok,
&ret_flags);
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);
}
fatal("gss_init_context failed");
}
/* If we've got an old receive buffer get rid of it */
if (token_ptr != GSS_C_NO_BUFFER)
xfree(recv_tok.value);
if (maj_status == GSS_S_COMPLETE) {
/* If mutual state flag is not true, kex fails */
if (!(ret_flags & GSS_C_MUTUAL_FLAG))
fatal("Mutual authentication failed");
/* If integ avail flag is not true kex fails */
if (!(ret_flags & GSS_C_INTEG_FLAG))
fatal("Integrity check failed");
}
/*
* If we have data to send, then the last message that we
* received cannot have been a 'complete'.
*/
if (send_tok.length != 0) {
if (first) {
packet_start(SSH2_MSG_KEXGSS_INIT);
packet_put_string(send_tok.value,
send_tok.length);
packet_put_bignum2(dh->pub_key);
first = 0;
} else {
packet_start(SSH2_MSG_KEXGSS_CONTINUE);
packet_put_string(send_tok.value,
send_tok.length);
}
packet_send();
gss_release_buffer(&min_status, &send_tok);
/* If we've sent them data, they should reply */
do {
type = packet_read();
if (type == SSH2_MSG_KEXGSS_HOSTKEY) {
debug("Received KEXGSS_HOSTKEY");
if (serverhostkey)
fatal("Server host key received more than once");
serverhostkey =
packet_get_string(&slen);
}
} while (type == SSH2_MSG_KEXGSS_HOSTKEY);
switch (type) {
case SSH2_MSG_KEXGSS_CONTINUE:
debug("Received GSSAPI_CONTINUE");
if (maj_status == GSS_S_COMPLETE)
fatal("GSSAPI Continue received from server when complete");
recv_tok.value = packet_get_string(&strlen);
recv_tok.length = strlen;
break;
case SSH2_MSG_KEXGSS_COMPLETE:
debug("Received GSSAPI_COMPLETE");
packet_get_bignum2(dh_server_pub);
msg_tok.value = packet_get_string(&strlen);
msg_tok.length = strlen;
/* Is there a token included? */
if (packet_get_char()) {
recv_tok.value=
packet_get_string(&strlen);
recv_tok.length = strlen;
/* If we're already complete - protocol error */
if (maj_status == GSS_S_COMPLETE)
packet_disconnect("Protocol error: received token when complete");
} else {
/* No token included */
if (maj_status != GSS_S_COMPLETE)
packet_disconnect("Protocol error: did not receive final token");
}
break;
case SSH2_MSG_KEXGSS_ERROR:
debug("Received Error");
maj_status = packet_get_int();
min_status = packet_get_int();
msg = packet_get_string(NULL);
lang = packet_get_string(NULL);
fatal("GSSAPI Error: \n%.400s",msg);
default:
packet_disconnect("Protocol error: didn't expect packet type %d",
type);
}
token_ptr = &recv_tok;
} else {
/* No data, and not complete */
if (maj_status != GSS_S_COMPLETE)
fatal("Not complete, and no token output");
}
} while (maj_status & GSS_S_CONTINUE_NEEDED);
/*
* We _must_ have received a COMPLETE message in reply from the
* server, which will have set dh_server_pub and msg_tok
*/
if (type != SSH2_MSG_KEXGSS_COMPLETE)
fatal("Didn't receive a SSH2_MSG_KEXGSS_COMPLETE when I expected it");
/* Check f in range [1, p-1] */
if (!dh_pub_is_valid(dh, dh_server_pub))
packet_disconnect("bad server public DH value");
/* compute K=f^x mod p */
klen = DH_size(dh);
kbuf = xmalloc(klen);
kout = DH_compute_key(kbuf, dh_server_pub, dh);
if (kout < 0)
fatal("DH_compute_key: failed");
shared_secret = BN_new();
if (shared_secret == NULL)
fatal("kexgss_client: BN_new failed");
if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
fatal("kexdh_client: 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->my), buffer_len(&kex->my),
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
(serverhostkey ? serverhostkey : empty), slen,
dh->pub_key, /* e */
dh_server_pub, /* f */
shared_secret, /* K */
&hash, &hashlen
);
break;
case KEX_GSS_GEX_SHA1:
kexgex_hash(
kex->evp_md,
kex->client_version_string,
kex->server_version_string,
buffer_ptr(&kex->my), buffer_len(&kex->my),
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
(serverhostkey ? serverhostkey : empty), slen,
min, nbits, max,
dh->p, dh->g,
dh->pub_key,
dh_server_pub,
shared_secret,
&hash, &hashlen
);
break;
default:
fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
}
gssbuf.value = hash;
gssbuf.length = hashlen;
/* Verify that the hash matches the MIC we just got. */
if (GSS_ERROR(ssh_gssapi_checkmic(ctxt, &gssbuf, &msg_tok)))
packet_disconnect("Hash's MIC didn't verify");
xfree(msg_tok.value);
DH_free(dh);
if (serverhostkey)
xfree(serverhostkey);
BN_clear_free(dh_server_pub);
/* save session id */
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);
}
if (kex->gss_deleg_creds)
ssh_gssapi_credentials_updated(ctxt);
if (gss_kex_context == NULL)
gss_kex_context = ctxt;
else
ssh_gssapi_delete_ctx(&ctxt);
kex_derive_keys(kex, hash, hashlen, shared_secret);
BN_clear_free(shared_secret);
kex_finish(kex);
}
