Excerpts from the release notes: * ssh-agent(1): PKCS#11 modules must now be specified by their full paths. Previously dlopen(3) could search for them in system library directories. * ssh(1): allow forwarding Unix Domain sockets via ssh -W. * ssh(1): add support for configuration tags to ssh(1). This adds a ssh_config(5) "Tag" directive and corresponding "Match tag" predicate that may be used to select blocks of configuration similar to the pf.conf(5) keywords of the same name. * ssh(1): add a "match localnetwork" predicate. This allows matching on the addresses of available network interfaces and may be used to vary the effective client configuration based on network location. * ssh-agent(1): improve isolation between loaded PKCS#11 modules by running separate ssh-pkcs11-helpers for each loaded provider. * ssh-agent(1), ssh(1): improve defences against invalid PKCS#11 modules being loaded by checking that the requested module contains the required symbol before loading it. * ssh(1): don't incorrectly disable hostname canonicalization when CanonicalizeHostname=yes and ProxyJump was expicitly set to "none". bz3567 Full release notes at https://www.openssh.com/txt/release-9.4 Relnotes: Yes Sponsored by: The FreeBSD Foundation
405 lines
10 KiB
C
405 lines
10 KiB
C
/* $OpenBSD: gss-serv.c,v 1.32 2020/03/13 03:17:07 djm Exp $ */
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/*
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* Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#ifdef GSSAPI
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#include <sys/types.h>
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#include <stdarg.h>
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#include <string.h>
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#include <unistd.h>
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#include "openbsd-compat/sys-queue.h"
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#include "xmalloc.h"
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#include "sshkey.h"
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#include "hostfile.h"
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#include "auth.h"
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#include "log.h"
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#include "channels.h"
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#include "session.h"
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#include "misc.h"
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#include "servconf.h"
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#include "ssh-gss.h"
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extern ServerOptions options;
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static ssh_gssapi_client gssapi_client =
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{ GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
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GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}};
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ssh_gssapi_mech gssapi_null_mech =
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{ NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
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#ifdef KRB5
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extern ssh_gssapi_mech gssapi_kerberos_mech;
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#endif
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ssh_gssapi_mech* supported_mechs[]= {
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#ifdef KRB5
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&gssapi_kerberos_mech,
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#endif
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&gssapi_null_mech,
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};
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/*
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* ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the
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* list of supported mechanisms before privsep is set up.
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*/
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static gss_OID_set supported_oids;
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void
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ssh_gssapi_prepare_supported_oids(void)
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{
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ssh_gssapi_supported_oids(&supported_oids);
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}
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OM_uint32
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ssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present)
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{
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if (supported_oids == NULL)
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ssh_gssapi_prepare_supported_oids();
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return gss_test_oid_set_member(ms, member, supported_oids, present);
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}
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/*
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* Acquire credentials for a server running on the current host.
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* Requires that the context structure contains a valid OID
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*/
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/* Returns a GSSAPI error code */
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/* Privileged (called from ssh_gssapi_server_ctx) */
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static OM_uint32
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ssh_gssapi_acquire_cred(Gssctxt *ctx)
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{
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OM_uint32 status;
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char lname[NI_MAXHOST];
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gss_OID_set oidset;
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if (options.gss_strict_acceptor) {
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gss_create_empty_oid_set(&status, &oidset);
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gss_add_oid_set_member(&status, ctx->oid, &oidset);
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if (gethostname(lname, HOST_NAME_MAX)) {
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gss_release_oid_set(&status, &oidset);
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return (-1);
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}
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if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
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gss_release_oid_set(&status, &oidset);
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return (ctx->major);
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}
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if ((ctx->major = gss_acquire_cred(&ctx->minor,
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ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds,
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NULL, NULL)))
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ssh_gssapi_error(ctx);
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gss_release_oid_set(&status, &oidset);
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return (ctx->major);
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} else {
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ctx->name = GSS_C_NO_NAME;
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ctx->creds = GSS_C_NO_CREDENTIAL;
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}
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return GSS_S_COMPLETE;
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}
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/* Privileged */
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OM_uint32
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ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
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{
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if (*ctx)
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ssh_gssapi_delete_ctx(ctx);
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ssh_gssapi_build_ctx(ctx);
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ssh_gssapi_set_oid(*ctx, oid);
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return (ssh_gssapi_acquire_cred(*ctx));
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}
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/* Unprivileged */
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void
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ssh_gssapi_supported_oids(gss_OID_set *oidset)
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{
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int i = 0;
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OM_uint32 min_status;
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int present;
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gss_OID_set supported;
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gss_create_empty_oid_set(&min_status, oidset);
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gss_indicate_mechs(&min_status, &supported);
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while (supported_mechs[i]->name != NULL) {
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if (GSS_ERROR(gss_test_oid_set_member(&min_status,
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&supported_mechs[i]->oid, supported, &present)))
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present = 0;
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if (present)
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gss_add_oid_set_member(&min_status,
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&supported_mechs[i]->oid, oidset);
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i++;
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}
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gss_release_oid_set(&min_status, &supported);
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}
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/* Wrapper around accept_sec_context
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* Requires that the context contains:
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* oid
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* credentials (from ssh_gssapi_acquire_cred)
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*/
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/* Privileged */
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OM_uint32
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ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
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gss_buffer_desc *send_tok, OM_uint32 *flags)
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{
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OM_uint32 status;
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gss_OID mech;
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ctx->major = gss_accept_sec_context(&ctx->minor,
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&ctx->context, ctx->creds, recv_tok,
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GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
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send_tok, flags, NULL, &ctx->client_creds);
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if (GSS_ERROR(ctx->major))
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ssh_gssapi_error(ctx);
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if (ctx->client_creds)
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debug("Received some client credentials");
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else
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debug("Got no client credentials");
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status = ctx->major;
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/* Now, if we're complete and we have the right flags, then
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* we flag the user as also having been authenticated
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*/
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if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
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(*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
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if (ssh_gssapi_getclient(ctx, &gssapi_client))
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fatal("Couldn't convert client name");
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}
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return (status);
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}
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/*
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* This parses an exported name, extracting the mechanism specific portion
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* to use for ACL checking. It verifies that the name belongs the mechanism
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* originally selected.
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*/
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static OM_uint32
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ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
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{
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u_char *tok;
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OM_uint32 offset;
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OM_uint32 oidl;
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tok = ename->value;
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/*
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* Check that ename is long enough for all of the fixed length
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* header, and that the initial ID bytes are correct
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*/
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if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
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return GSS_S_FAILURE;
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/*
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* Extract the OID, and check it. Here GSSAPI breaks with tradition
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* and does use the OID type and length bytes. To confuse things
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* there are two lengths - the first including these, and the
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* second without.
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*/
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oidl = get_u16(tok+2); /* length including next two bytes */
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oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
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/*
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* Check the BER encoding for correct type and length, that the
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* string is long enough and that the OID matches that in our context
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*/
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if (tok[4] != 0x06 || tok[5] != oidl ||
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ename->length < oidl+6 ||
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!ssh_gssapi_check_oid(ctx, tok+6, oidl))
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return GSS_S_FAILURE;
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offset = oidl+6;
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if (ename->length < offset+4)
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return GSS_S_FAILURE;
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name->length = get_u32(tok+offset);
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offset += 4;
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if (UINT_MAX - offset < name->length)
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return GSS_S_FAILURE;
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if (ename->length < offset+name->length)
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return GSS_S_FAILURE;
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name->value = xmalloc(name->length+1);
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memcpy(name->value, tok+offset, name->length);
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((char *)name->value)[name->length] = 0;
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return GSS_S_COMPLETE;
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}
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/* Extract the client details from a given context. This can only reliably
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* be called once for a context */
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/* Privileged (called from accept_secure_ctx) */
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OM_uint32
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ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
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{
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int i = 0;
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gss_buffer_desc ename;
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client->mech = NULL;
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while (supported_mechs[i]->name != NULL) {
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if (supported_mechs[i]->oid.length == ctx->oid->length &&
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(memcmp(supported_mechs[i]->oid.elements,
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ctx->oid->elements, ctx->oid->length) == 0))
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client->mech = supported_mechs[i];
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i++;
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}
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if (client->mech == NULL)
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return GSS_S_FAILURE;
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if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
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&client->displayname, NULL))) {
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ssh_gssapi_error(ctx);
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return (ctx->major);
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}
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if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
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&ename))) {
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ssh_gssapi_error(ctx);
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return (ctx->major);
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}
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if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
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&client->exportedname))) {
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return (ctx->major);
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}
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/* We can't copy this structure, so we just move the pointer to it */
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client->creds = ctx->client_creds;
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ctx->client_creds = GSS_C_NO_CREDENTIAL;
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return (ctx->major);
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}
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/* As user - called on fatal/exit */
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void
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ssh_gssapi_cleanup_creds(void)
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{
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if (gssapi_client.store.filename != NULL) {
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/* Unlink probably isn't sufficient */
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debug("removing gssapi cred file\"%s\"",
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gssapi_client.store.filename);
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unlink(gssapi_client.store.filename);
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}
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}
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/* As user */
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void
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ssh_gssapi_storecreds(void)
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{
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if (gssapi_client.mech && gssapi_client.mech->storecreds) {
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(*gssapi_client.mech->storecreds)(&gssapi_client);
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} else
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debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
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}
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/* This allows GSSAPI methods to do things to the child's environment based
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* on the passed authentication process and credentials.
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*/
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/* As user */
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void
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ssh_gssapi_do_child(char ***envp, u_int *envsizep)
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{
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if (gssapi_client.store.envvar != NULL &&
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gssapi_client.store.envval != NULL) {
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debug("Setting %s to %s", gssapi_client.store.envvar,
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gssapi_client.store.envval);
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child_set_env(envp, envsizep, gssapi_client.store.envvar,
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gssapi_client.store.envval);
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}
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}
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/* Privileged */
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int
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ssh_gssapi_userok(char *user)
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{
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OM_uint32 lmin;
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if (gssapi_client.exportedname.length == 0 ||
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gssapi_client.exportedname.value == NULL) {
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debug("No suitable client data");
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return 0;
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}
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if (gssapi_client.mech && gssapi_client.mech->userok)
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if ((*gssapi_client.mech->userok)(&gssapi_client, user))
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return 1;
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else {
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/* Destroy delegated credentials if userok fails */
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gss_release_buffer(&lmin, &gssapi_client.displayname);
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gss_release_buffer(&lmin, &gssapi_client.exportedname);
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gss_release_cred(&lmin, &gssapi_client.creds);
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explicit_bzero(&gssapi_client,
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sizeof(ssh_gssapi_client));
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return 0;
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}
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else
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debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
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return (0);
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}
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/* Privileged */
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OM_uint32
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ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
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{
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ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
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gssbuf, gssmic, NULL);
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return (ctx->major);
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}
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/* Privileged */
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const char *ssh_gssapi_displayname(void)
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{
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if (gssapi_client.displayname.length == 0 ||
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gssapi_client.displayname.value == NULL)
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return NULL;
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return (char *)gssapi_client.displayname.value;
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}
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#endif
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