1 files changed, 300 insertions, 0 deletions

diff --git a/kexgsss.c b/kexgsss.c
new file mode 100644
index 000000000..18070f1d7
--- /dev/null
+++ b/kexgsss.c
@@ -0,0 +1,300 @@
+/*
+ * Copyright (c) 2001-2009 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 <string.h>
+
+#include <openssl/crypto.h>
+#include <openssl/bn.h>
+
+#include "xmalloc.h"
+#include "sshbuf.h"
+#include "ssh2.h"
+#include "sshkey.h"
+#include "cipher.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "dh.h"
+#include "ssh-gss.h"
+#include "monitor_wrap.h"
+#include "misc.h"
+#include "servconf.h"
+#include "digest.h"
+
+extern ServerOptions options;
+
+int
+kexgss_server(struct ssh *ssh)
+{
+        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;
+        u_char *kbuf;
+        DH *dh;
+        int min = -1, max = -1, nbits = -1;
+        const BIGNUM *pub_key, *dh_p, *dh_g;
+        BIGNUM *shared_secret = NULL;
+        BIGNUM *dh_client_pub = NULL;
+        int type = 0;
+        gss_OID oid;
+        char *mechs;
+        u_char hash[SSH_DIGEST_MAX_LENGTH];
+        size_t hashlen;
+
+        /* 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()) {
+                mechs = ssh_gssapi_server_mechanisms();
+                free(mechs);
+        }
+
+        debug2("%s: Identifying %s", __func__, ssh->kex->name);
+        oid = ssh_gssapi_id_kex(NULL, ssh->kex->name, ssh->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 (ssh->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();
+                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(MAX(DH_GRP_MIN, min),
+                    nbits, MIN(DH_GRP_MAX, max)));
+                if (dh == NULL)
+                        packet_disconnect("Protocol error: no matching group found");
+                DH_get0_pqg(dh, &dh_p, NULL, &dh_g);
+
+                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__, ssh->kex->kex_type);
+        }
+
+        dh_gen_key(dh, ssh->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));
+
+                free(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);
+        free(kbuf);
+
+        DH_get0_key(dh, &pub_key, NULL);
+        DH_get0_pqg(dh, &dh_p, NULL, &dh_g);
+
+        hashlen = sizeof(hash);
+        switch (ssh->kex->kex_type) {
+        case KEX_GSS_GRP1_SHA1:
+        case KEX_GSS_GRP14_SHA1:
+                kex_dh_hash(
+                    ssh->kex->hash_alg,
+                    ssh->kex->client_version_string, ssh->kex->server_version_string,
+                    sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
+                    sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
+                    NULL, 0, /* Change this if we start sending host keys */
+                    dh_client_pub, pub_key, shared_secret,
+                    hash, &hashlen
+                );
+                break;
+        case KEX_GSS_GEX_SHA1:
+                kexgex_hash(
+                    ssh->kex->hash_alg,
+                    ssh->kex->client_version_string, ssh->kex->server_version_string,
+                    sshbuf_ptr(ssh->kex->peer), sshbuf_len(ssh->kex->peer),
+                    sshbuf_ptr(ssh->kex->my), sshbuf_len(ssh->kex->my),
+                    NULL, 0,
+                    min, nbits, max,
+                    dh_p, dh_g,
+                    dh_client_pub,
+                    pub_key,
+                    shared_secret,
+                    hash, &hashlen
+                );
+                break;
+        default:
+                fatal("%s: Unexpected KEX type %d", __func__, ssh->kex->kex_type);
+        }
+
+        BN_clear_free(dh_client_pub);
+
+        if (ssh->kex->session_id == NULL) {
+                ssh->kex->session_id_len = hashlen;
+                ssh->kex->session_id = xmalloc(ssh->kex->session_id_len);
+                memcpy(ssh->kex->session_id, hash, ssh->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(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_bn(ssh, hash, hashlen, shared_secret);
+        BN_clear_free(shared_secret);
+        kex_send_newkeys(ssh);
+
+        /* If this was a rekey, then save out any delegated credentials we
+         * just exchanged.  */
+        if (options.gss_store_rekey)
+                ssh_gssapi_rekey_creds();
+        return 0;
+}
+#endif /* GSSAPI */