From f88d86e05895671b9d036c26566a41752ec86c31 Mon Sep 17 00:00:00 2001 From: Colin Watson Date: Wed, 14 Sep 2005 15:20:11 +0000 Subject: * Add remaining pieces of Kerberos support (closes: #275472): - Add GSSAPI key exchange support from http://www.sxw.org.uk/computing/patches/openssh.html (thanks, Stephen Frost). --- kexgsss.c | 204 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 204 insertions(+) create mode 100644 kexgsss.c (limited to 'kexgsss.c') diff --git a/kexgsss.c b/kexgsss.c new file mode 100644 index 000000000..80c133ac9 --- /dev/null +++ b/kexgsss.c @@ -0,0 +1,204 @@ +/* + * Copyright (c) 2001-2004 Simon Wilkinson. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#ifdef GSSAPI + +#include +#include + +#include "xmalloc.h" +#include "buffer.h" +#include "bufaux.h" +#include "kex.h" +#include "log.h" +#include "packet.h" +#include "dh.h" +#include "ssh2.h" +#include "ssh-gss.h" +#include "monitor_wrap.h" + +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, send_tok, recv_tok, msg_tok; + Gssctxt *ctxt = NULL; + unsigned int klen, kout; + unsigned char *kbuf, *hash; + DH *dh; + BIGNUM *shared_secret = NULL; + BIGNUM *dh_client_pub = NULL; + int type =0; + u_int slen; + gss_OID oid; + + /* Initialise GSSAPI */ + + debug2("%s: Identifying %s", __func__, kex->name); + oid = ssh_gssapi_id_kex(NULL, kex->name); + if (oid == NULL) + 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"); + + 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; + + dh_client_pub = BN_new(); + + if (dh_client_pub == 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)); + + gss_release_buffer(&min_status, &recv_tok); + + 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"); + + dh = dh_new_group1(); + dh_gen_key(dh, kex->we_need * 8); + + 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); + + shared_secret = BN_new(); + BN_bin2bn(kbuf, kout, shared_secret); + memset(kbuf, 0, klen); + xfree(kbuf); + + /* The GSSAPI hash is identical to the Diffie Helman one */ + hash = 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 + ); + BN_free(dh_client_pub); + + if (kex->session_id == NULL) { + kex->session_id_len = 20; + kex->session_id = xmalloc(kex->session_id_len); + memcpy(kex->session_id, hash, kex->session_id_len); + } + + gssbuf.value = hash; + gssbuf.length = 20; /* Hashlen appears to always be 20 */ + + 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((char *)msg_tok.value,msg_tok.length); + + if (send_tok.length!=0) { + packet_put_char(1); /* true */ + packet_put_string((char *)send_tok.value, send_tok.length); + } else { + packet_put_char(0); /* false */ + } + packet_send(); + + gss_release_buffer(&min_status, &send_tok); + + if (gss_kex_context == NULL) + gss_kex_context = ctxt; + else + ssh_gssapi_delete_ctx(&ctxt); + + DH_free(dh); + + kex_derive_keys(kex, hash, shared_secret); + BN_clear_free(shared_secret); + kex_finish(kex); +} +#endif /* GSSAPI */ -- cgit v1.2.3