1 files changed, 474 insertions, 0 deletions

diff --git a/kexgsss.c b/kexgsss.c
new file mode 100644
index 000000000..60bc02deb
--- /dev/null
+++ b/kexgsss.c
@@ -0,0 +1,474 @@
+/*
+ * 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"
+
+#if defined(GSSAPI) && defined(WITH_OPENSSL)
+
+#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"      /* servconf.h needs misc.h for struct ForwardOptions */
+#include "servconf.h"
+#include "ssh-gss.h"
+#include "digest.h"
+#include "ssherr.h"
+
+extern ServerOptions options;
+
+int
+kexgss_server(struct ssh *ssh)
+{
+        struct kex *kex = ssh->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;
+        struct sshbuf *shared_secret = NULL;
+        struct sshbuf *client_pubkey = NULL;
+        struct sshbuf *server_pubkey = NULL;
+        struct sshbuf *empty = sshbuf_new();
+        int type = 0;
+        gss_OID oid;
+        char *mechs;
+        u_char hash[SSH_DIGEST_MAX_LENGTH];
+        size_t hashlen;
+        int r;
+
+        /* 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__, 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");
+
+        do {
+                debug("Wait SSH2_MSG_KEXGSS_INIT");
+                type = ssh_packet_read(ssh);
+                switch(type) {
+                case SSH2_MSG_KEXGSS_INIT:
+                        if (client_pubkey != NULL)
+                                fatal("Received KEXGSS_INIT after initialising");
+                        if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
+                                &recv_tok)) != 0 ||
+                            (r = sshpkt_getb_froms(ssh, &client_pubkey)) != 0 ||
+                            (r = sshpkt_get_end(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+
+                        switch (kex->kex_type) {
+                        case KEX_GSS_GRP1_SHA1:
+                        case KEX_GSS_GRP14_SHA1:
+                        case KEX_GSS_GRP14_SHA256:
+                        case KEX_GSS_GRP16_SHA512:
+                                r = kex_dh_enc(kex, client_pubkey, &server_pubkey,
+                                    &shared_secret);
+                                break;
+                        case KEX_GSS_NISTP256_SHA256:
+                                r = kex_ecdh_enc(kex, client_pubkey, &server_pubkey,
+                                    &shared_secret);
+                                break;
+                        case KEX_GSS_C25519_SHA256:
+                                r = kex_c25519_enc(kex, client_pubkey, &server_pubkey,
+                                    &shared_secret);
+                                break;
+                        default:
+                                fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
+                        }
+                        if (r != 0)
+                                goto out;
+
+                        /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
+                        break;
+                case SSH2_MSG_KEXGSS_CONTINUE:
+                        if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
+                                &recv_tok)) != 0 ||
+                            (r = sshpkt_get_end(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+                        break;
+                default:
+                        sshpkt_disconnect(ssh,
+                            "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 (client_pubkey == NULL)
+                        fatal("No client public key");
+
+                if (maj_status & GSS_S_CONTINUE_NEEDED) {
+                        debug("Sending GSSAPI_CONTINUE");
+                        if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
+                            (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
+                            (r = sshpkt_send(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+                        gss_release_buffer(&min_status, &send_tok);
+                }
+        } while (maj_status & GSS_S_CONTINUE_NEEDED);
+
+        if (GSS_ERROR(maj_status)) {
+                if (send_tok.length > 0) {
+                        if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
+                            (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
+                            (r = sshpkt_send(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+                }
+                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");
+
+        hashlen = sizeof(hash);
+        if ((r = kex_gen_hash(
+            kex->hash_alg,
+            kex->client_version,
+            kex->server_version,
+            kex->peer,
+            kex->my,
+            empty,
+            client_pubkey,
+            server_pubkey,
+            shared_secret,
+            hash, &hashlen)) != 0)
+                goto out;
+
+        gssbuf.value = hash;
+        gssbuf.length = hashlen;
+
+        if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt, &gssbuf, &msg_tok))))
+                fatal("Couldn't get MIC");
+
+        if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_COMPLETE)) != 0 ||
+            (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
+            (r = sshpkt_put_string(ssh, msg_tok.value, msg_tok.length)) != 0)
+                fatal("sshpkt failed: %s", ssh_err(r));
+
+        if (send_tok.length != 0) {
+                if ((r = sshpkt_put_u8(ssh, 1)) != 0 || /* true */
+                    (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0)
+                        fatal("sshpkt failed: %s", ssh_err(r));
+        } else {
+                if ((r = sshpkt_put_u8(ssh, 0)) != 0) /* false */
+                        fatal("sshpkt failed: %s", ssh_err(r));
+        }
+        if ((r = sshpkt_send(ssh)) != 0)
+                fatal("sshpkt_send failed: %s", ssh_err(r));
+
+        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);
+
+        if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
+                r = 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();
+out:
+        sshbuf_free(empty);
+        explicit_bzero(hash, sizeof(hash));
+        sshbuf_free(shared_secret);
+        sshbuf_free(client_pubkey);
+        sshbuf_free(server_pubkey);
+        return r;
+}
+
+int
+kexgssgex_server(struct ssh *ssh)
+{
+        struct kex *kex = ssh->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;
+        struct sshbuf *shared_secret = NULL;
+        int type = 0;
+        gss_OID oid;
+        char *mechs;
+        u_char hash[SSH_DIGEST_MAX_LENGTH];
+        size_t hashlen;
+        BIGNUM *dh_client_pub = NULL;
+        const BIGNUM *pub_key, *dh_p, *dh_g;
+        int min = -1, max = -1, nbits = -1;
+        int cmin = -1, cmax = -1; /* client proposal */
+        struct sshbuf *empty = sshbuf_new();
+        int r;
+
+        /* 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()))
+                        free(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");
+
+        /* 5. S generates an ephemeral key pair (do the allocations early) */
+        debug("Doing group exchange");
+        ssh_packet_read_expect(ssh, SSH2_MSG_KEXGSS_GROUPREQ);
+        /* store client proposal to provide valid signature */
+        if ((r = sshpkt_get_u32(ssh, &cmin)) != 0 ||
+            (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
+            (r = sshpkt_get_u32(ssh, &cmax)) != 0 ||
+            (r = sshpkt_get_end(ssh)) != 0)
+                fatal("sshpkt failed: %s", ssh_err(r));
+        kex->nbits = nbits;
+        kex->min = cmin;
+        kex->max = cmax;
+        min = MAX(DH_GRP_MIN, cmin);
+        max = MIN(DH_GRP_MAX, cmax);
+        nbits = MAXIMUM(DH_GRP_MIN, nbits);
+        nbits = MINIMUM(DH_GRP_MAX, nbits);
+        if (max < min || nbits < min || max < nbits)
+                fatal("GSS_GEX, bad parameters: %d !< %d !< %d",
+                    min, nbits, max);
+        kex->dh = PRIVSEP(choose_dh(min, nbits, max));
+        if (kex->dh == NULL) {
+                sshpkt_disconnect(ssh, "Protocol error: no matching group found");
+                fatal("Protocol error: no matching group found");
+        }
+
+        DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
+        if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_GROUP)) != 0 ||
+            (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 ||
+            (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 ||
+            (r = sshpkt_send(ssh)) != 0)
+                fatal("sshpkt failed: %s", ssh_err(r));
+
+        if ((r = ssh_packet_write_wait(ssh)) != 0)
+                fatal("ssh_packet_write_wait: %s", ssh_err(r));
+
+        /* Compute our exchange value in parallel with the client */
+        if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
+                goto out;
+
+        do {
+                debug("Wait SSH2_MSG_GSSAPI_INIT");
+                type = ssh_packet_read(ssh);
+                switch(type) {
+                case SSH2_MSG_KEXGSS_INIT:
+                        if (dh_client_pub != NULL)
+                                fatal("Received KEXGSS_INIT after initialising");
+                        if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
+                                &recv_tok)) != 0 ||
+                            (r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
+                            (r = sshpkt_get_end(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+
+                        /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */
+                        break;
+                case SSH2_MSG_KEXGSS_CONTINUE:
+                        if ((r = ssh_gssapi_sshpkt_get_buffer_desc(ssh,
+                                &recv_tok)) != 0 ||
+                            (r = sshpkt_get_end(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+                        break;
+                default:
+                        sshpkt_disconnect(ssh,
+                            "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");
+                        if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
+                            (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
+                            (r = sshpkt_send(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+                        gss_release_buffer(&min_status, &send_tok);
+                }
+        } while (maj_status & GSS_S_CONTINUE_NEEDED);
+
+        if (GSS_ERROR(maj_status)) {
+                if (send_tok.length > 0) {
+                        if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_CONTINUE)) != 0 ||
+                            (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 ||
+                            (r = sshpkt_send(ssh)) != 0)
+                                fatal("sshpkt failed: %s", ssh_err(r));
+                }
+                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");
+
+        /* calculate shared secret */
+        if ((shared_secret = sshbuf_new()) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        if ((r = kex_dh_compute_key(kex, dh_client_pub, shared_secret)) != 0)
+                goto out;
+
+        DH_get0_key(kex->dh, &pub_key, NULL);
+        DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
+        hashlen = sizeof(hash);
+        if ((r = kexgex_hash(
+            kex->hash_alg,
+            kex->client_version,
+            kex->server_version,
+            kex->peer,
+            kex->my,
+            empty,
+            cmin, nbits, cmax,
+            dh_p, dh_g,
+            dh_client_pub,
+            pub_key,
+            sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
+            hash, &hashlen)) != 0)
+                fatal("kexgex_hash failed: %s", ssh_err(r));
+
+        gssbuf.value = hash;
+        gssbuf.length = hashlen;
+
+        if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt, &gssbuf, &msg_tok))))
+                fatal("Couldn't get MIC");
+
+        if ((r = sshpkt_start(ssh, SSH2_MSG_KEXGSS_COMPLETE)) != 0 ||
+            (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||
+            (r = sshpkt_put_string(ssh, msg_tok.value, msg_tok.length)) != 0)
+                fatal("sshpkt failed: %s", ssh_err(r));
+
+        if (send_tok.length != 0) {
+                if ((r = sshpkt_put_u8(ssh, 1)) != 0 || /* true */
+                    (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0)
+                        fatal("sshpkt failed: %s", ssh_err(r));
+        } else {
+                if ((r = sshpkt_put_u8(ssh, 0)) != 0) /* false */
+                        fatal("sshpkt failed: %s", ssh_err(r));
+        }
+        if ((r = sshpkt_send(ssh)) != 0)
+                fatal("sshpkt failed: %s", ssh_err(r));
+
+        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);
+
+        /* Finally derive the keys and send them */
+        if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
+                r = 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();
+out:
+        sshbuf_free(empty);
+        explicit_bzero(hash, sizeof(hash));
+        DH_free(kex->dh);
+        kex->dh = NULL;
+        BN_clear_free(dh_client_pub);
+        sshbuf_free(shared_secret);
+        return r;
+}
+#endif /* defined(GSSAPI) && defined(WITH_OPENSSL) */