* 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).

1 files changed, 242 insertions, 0 deletions

diff --git a/kexgssc.c b/kexgssc.c
new file mode 100644
index 000000000..eee96dd23
--- /dev/null
+++ b/kexgssc.c
@@ -0,0 +1,242 @@
+/*
+ * 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 <openssl/crypto.h>
+#include <openssl/bn.h>
+
+#include "xmalloc.h"
+#include "buffer.h"
+#include "bufaux.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "dh.h"
+#include "canohost.h"
+#include "ssh2.h"
+#include "ssh-gss.h"
+
+void
+kexgss_client(Kex *kex) {
+        gss_buffer_desc gssbuf, send_tok, recv_tok, msg_tok, *token_ptr;
+        Gssctxt *ctxt;
+        OM_uint32 maj_status, min_status, ret_flags;
+        unsigned int klen, kout;
+        DH *dh; 
+        BIGNUM *dh_server_pub = 0;
+        BIGNUM *shared_secret = 0;      
+        unsigned char *kbuf;
+        unsigned char *hash;
+        unsigned char *serverhostkey;
+        char *msg;
+        char *lang;
+        int type = 0;
+        int first = 1;
+        int slen = 0;
+        u_int strlen;
+        
+        ssh_gssapi_build_ctx(&ctxt);
+        if (ssh_gssapi_id_kex(ctxt,kex->name) == NULL)
+                fatal("Couldn't identify host exchange");
+
+        if (ssh_gssapi_import_name(ctxt,get_canonical_hostname(1)))
+                fatal("Couldn't import hostname ");
+        
+        /* This code should match that in ssh_dh1_client */
+                
+        /* Step 1 - e is dh->pub_key */
+        dh = dh_new_group1();
+        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)
+                        (void) gss_release_buffer(&min_status, &recv_tok);
+
+                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();
+
+                        /* If we've sent them data, they should reply */
+                
+                        type = packet_read();
+                        switch (type) {
+                        case SSH2_MSG_KEXGSS_HOSTKEY:
+                                debug("Received KEXGSS_HOSTKEY");
+                                serverhostkey = packet_get_string(&slen);
+                                break;
+                        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);
+                                fprintf(stderr,"GSSAPI Error: \n%s",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);
+
+        shared_secret = BN_new();
+        BN_bin2bn(kbuf,kout, shared_secret);
+        memset(kbuf, 0, klen);
+        xfree(kbuf);
+
+        /* The GSS hash is identical to the DH one */
+        hash = 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, slen, /* server host key */
+            dh->pub_key,        /* e */
+            dh_server_pub,      /* f */
+            shared_secret       /* K */
+        );
+        
+        gssbuf.value = hash;
+        gssbuf.length = 20;
+
+        /* 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");
+        
+        DH_free(dh);
+        /* save session id */
+        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);
+        }
+
+        if (gss_kex_context == NULL)
+                gss_kex_context = ctxt;
+        else
+                ssh_gssapi_delete_ctx(&ctxt);
+
+        kex_derive_keys(kex, hash, shared_secret);
+        BN_clear_free(shared_secret);
+        kex_finish(kex);
+}
+
+#endif /* GSSAPI */