/* $NetBSD: auth2-gss.c,v 1.16.2.1 2023/11/02 22:15:21 sborrill Exp $ */ /* $OpenBSD: auth2-gss.c,v 1.34 2023/03/31 04:22:27 djm Exp $ */ /* * Copyright (c) 2001-2003 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" __RCSID("$NetBSD: auth2-gss.c,v 1.16.2.1 2023/11/02 22:15:21 sborrill Exp $"); #ifdef GSSAPI #include #include #include "xmalloc.h" #include "sshkey.h" #include "hostfile.h" #include "auth.h" #include "ssh2.h" #include "log.h" #include "misc.h" #include "dispatch.h" #include "sshbuf.h" #include "ssherr.h" #include "servconf.h" #include "packet.h" #include "kex.h" #include "ssh-gss.h" #include "monitor_wrap.h" #define SSH_GSSAPI_MAX_MECHS 2048 extern ServerOptions options; static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh); static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh); static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh); static int input_gssapi_errtok(int, u_int32_t, struct ssh *); /* * We only support those mechanisms that we know about (ie ones that we know * how to check local user kuserok and the like) */ static int userauth_gssapi(struct ssh *ssh, const char *method) { Authctxt *authctxt = ssh->authctxt; gss_OID_desc goid = {0, NULL}; Gssctxt *ctxt = NULL; int r, present; u_int mechs; OM_uint32 ms; size_t len; u_char *doid = NULL; if ((r = sshpkt_get_u32(ssh, &mechs)) != 0) fatal_fr(r, "parse packet"); if (mechs == 0) { logit_f("mechanism negotiation is not supported"); return (0); } else if (mechs > SSH_GSSAPI_MAX_MECHS) { logit_f("too many mechanisms requested %u > %u", mechs, SSH_GSSAPI_MAX_MECHS); return (0); } do { mechs--; free(doid); present = 0; if ((r = sshpkt_get_string(ssh, &doid, &len)) != 0) fatal_fr(r, "parse oid"); if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && doid[1] == len - 2) { goid.elements = doid + 2; goid.length = len - 2; ssh_gssapi_test_oid_supported(&ms, &goid, &present); } else { logit_f("badly formed OID received"); } } while (mechs > 0 && !present); if (!present) { free(doid); authctxt->server_caused_failure = 1; return (0); } if (!authctxt->valid || authctxt->user == NULL) { debug2_f("disabled because of invalid user"); free(doid); return (0); } if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { if (ctxt != NULL) ssh_gssapi_delete_ctx(&ctxt); free(doid); authctxt->server_caused_failure = 1; return (0); } authctxt->methoddata = (void *)ctxt; /* Return the OID that we received */ if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE)) != 0 || (r = sshpkt_put_string(ssh, doid, len)) != 0 || (r = sshpkt_send(ssh)) != 0) fatal_fr(r, "send packet"); free(doid); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); authctxt->postponed = 1; return (0); } static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh) { Authctxt *authctxt = ssh->authctxt; Gssctxt *gssctxt; gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; gss_buffer_desc recv_tok; OM_uint32 maj_status, min_status, flags; u_char *p; size_t len; int r; if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) fatal("No authentication or GSSAPI context"); gssctxt = authctxt->methoddata; if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 || (r = sshpkt_get_end(ssh)) != 0) fatal_fr(r, "parse packet"); recv_tok.value = p; recv_tok.length = len; maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, &send_tok, &flags)); free(p); if (GSS_ERROR(maj_status)) { if (send_tok.length != 0) { if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK)) != 0 || (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 || (r = sshpkt_send(ssh)) != 0) fatal_fr(r, "send ERRTOK packet"); } authctxt->postponed = 0; ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); userauth_finish(ssh, 0, "gssapi-with-mic", NULL); } else { if (send_tok.length != 0) { if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN)) != 0 || (r = sshpkt_put_string(ssh, send_tok.value, send_tok.length)) != 0 || (r = sshpkt_send(ssh)) != 0) fatal_fr(r, "send TOKEN packet"); } if (maj_status == GSS_S_COMPLETE) { ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); if (flags & GSS_C_INTEG_FLAG) ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, &input_gssapi_mic); else ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, &input_gssapi_exchange_complete); } } gss_release_buffer(&min_status, &send_tok); return 0; } static int input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh) { Authctxt *authctxt = ssh->authctxt; Gssctxt *gssctxt; gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; gss_buffer_desc recv_tok; OM_uint32 maj_status; int r; u_char *p; size_t len; if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) fatal("No authentication or GSSAPI context"); gssctxt = authctxt->methoddata; if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 || (r = sshpkt_get_end(ssh)) != 0) fatal_fr(r, "parse packet"); recv_tok.value = p; recv_tok.length = len; /* Push the error token into GSSAPI to see what it says */ maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, &send_tok, NULL)); free(recv_tok.value); /* We can't return anything to the client, even if we wanted to */ ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); /* The client will have already moved on to the next auth */ gss_release_buffer(&maj_status, &send_tok); return 0; } /* * This is called when the client thinks we've completed authentication. * It should only be enabled in the dispatch handler by the function above, * which only enables it once the GSSAPI exchange is complete. */ static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh) { Authctxt *authctxt = ssh->authctxt; int r, authenticated; const char *displayname; if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) fatal("No authentication or GSSAPI context"); /* * We don't need to check the status, because we're only enabled in * the dispatcher once the exchange is complete */ if ((r = sshpkt_get_end(ssh)) != 0) fatal_fr(r, "parse packet"); authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); if ((!use_privsep || mm_is_monitor()) && (displayname = ssh_gssapi_displayname()) != NULL) auth2_record_info(authctxt, "%s", displayname); authctxt->postponed = 0; ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL); return 0; } static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh) { Authctxt *authctxt = ssh->authctxt; Gssctxt *gssctxt; int r, authenticated = 0; struct sshbuf *b; gss_buffer_desc mic, gssbuf; const char *displayname; u_char *p; size_t len; if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) fatal("No authentication or GSSAPI context"); gssctxt = authctxt->methoddata; if ((r = sshpkt_get_string(ssh, &p, &len)) != 0) fatal_fr(r, "parse packet"); if ((b = sshbuf_new()) == NULL) fatal_f("sshbuf_new failed"); mic.value = p; mic.length = len; ssh_gssapi_buildmic(b, authctxt->user, authctxt->service, "gssapi-with-mic", ssh->kex->session_id); if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL) fatal_f("sshbuf_mutable_ptr failed"); gssbuf.length = sshbuf_len(b); if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); else logit("GSSAPI MIC check failed"); sshbuf_free(b); free(mic.value); if ((!use_privsep || mm_is_monitor()) && (displayname = ssh_gssapi_displayname()) != NULL) auth2_record_info(authctxt, "%s", displayname); authctxt->postponed = 0; ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL); return 0; } Authmethod method_gssapi = { "gssapi-with-mic", NULL, userauth_gssapi, &options.gss_authentication }; #endif