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/* $OpenBSD: gss-serv.c,v 1.29 2015/05/22 03:50:02 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"
#ifdef GSSAPI
#include <sys/types.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include "openbsd-compat/sys-queue.h"
#include "xmalloc.h"
#include "buffer.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "log.h"
#include "channels.h"
#include "session.h"
#include "misc.h"
#include "servconf.h"
#include "ssh-gss.h"
extern ServerOptions options;
static ssh_gssapi_client gssapi_client =
{ GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}};
ssh_gssapi_mech gssapi_null_mech =
{ NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
#ifdef KRB5
extern ssh_gssapi_mech gssapi_kerberos_mech;
#endif
ssh_gssapi_mech* supported_mechs[]= {
#ifdef KRB5
&gssapi_kerberos_mech,
#endif
&gssapi_null_mech,
};
/*
* ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the
* list of supported mechanisms before privsep is set up.
*/
static gss_OID_set supported_oids;
void
ssh_gssapi_prepare_supported_oids(void)
{
ssh_gssapi_supported_oids(&supported_oids);
}
OM_uint32
ssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present)
{
if (supported_oids == NULL)
ssh_gssapi_prepare_supported_oids();
return gss_test_oid_set_member(ms, member, supported_oids, present);
}
/*
* Acquire credentials for a server running on the current host.
* Requires that the context structure contains a valid OID
*/
/* Returns a GSSAPI error code */
/* Privileged (called from ssh_gssapi_server_ctx) */
static OM_uint32
ssh_gssapi_acquire_cred(Gssctxt *ctx)
{
OM_uint32 status;
char lname[NI_MAXHOST];
gss_OID_set oidset;
if (options.gss_strict_acceptor) {
gss_create_empty_oid_set(&status, &oidset);
gss_add_oid_set_member(&status, ctx->oid, &oidset);
if (gethostname(lname, MAXHOSTNAMELEN)) {
gss_release_oid_set(&status, &oidset);
return (-1);
}
if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
gss_release_oid_set(&status, &oidset);
return (ctx->major);
}
if ((ctx->major = gss_acquire_cred(&ctx->minor,
ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds,
NULL, NULL)))
ssh_gssapi_error(ctx);
gss_release_oid_set(&status, &oidset);
return (ctx->major);
} else {
ctx->name = GSS_C_NO_NAME;
ctx->creds = GSS_C_NO_CREDENTIAL;
}
return GSS_S_COMPLETE;
}
/* Privileged */
OM_uint32
ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
{
if (*ctx)
ssh_gssapi_delete_ctx(ctx);
ssh_gssapi_build_ctx(ctx);
ssh_gssapi_set_oid(*ctx, oid);
return (ssh_gssapi_acquire_cred(*ctx));
}
/* Unprivileged */
void
ssh_gssapi_supported_oids(gss_OID_set *oidset)
{
int i = 0;
OM_uint32 min_status;
int present;
gss_OID_set supported;
gss_create_empty_oid_set(&min_status, oidset);
gss_indicate_mechs(&min_status, &supported);
while (supported_mechs[i]->name != NULL) {
if (GSS_ERROR(gss_test_oid_set_member(&min_status,
&supported_mechs[i]->oid, supported, &present)))
present = 0;
if (present)
gss_add_oid_set_member(&min_status,
&supported_mechs[i]->oid, oidset);
i++;
}
gss_release_oid_set(&min_status, &supported);
}
/* Wrapper around accept_sec_context
* Requires that the context contains:
* oid
* credentials (from ssh_gssapi_acquire_cred)
*/
/* Privileged */
OM_uint32
ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
gss_buffer_desc *send_tok, OM_uint32 *flags)
{
OM_uint32 status;
gss_OID mech;
ctx->major = gss_accept_sec_context(&ctx->minor,
&ctx->context, ctx->creds, recv_tok,
GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
send_tok, flags, NULL, &ctx->client_creds);
if (GSS_ERROR(ctx->major))
ssh_gssapi_error(ctx);
if (ctx->client_creds)
debug("Received some client credentials");
else
debug("Got no client credentials");
status = ctx->major;
/* Now, if we're complete and we have the right flags, then
* we flag the user as also having been authenticated
*/
if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
(*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
if (ssh_gssapi_getclient(ctx, &gssapi_client))
fatal("Couldn't convert client name");
}
return (status);
}
/*
* This parses an exported name, extracting the mechanism specific portion
* to use for ACL checking. It verifies that the name belongs the mechanism
* originally selected.
*/
static OM_uint32
ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
{
u_char *tok;
OM_uint32 offset;
OM_uint32 oidl;
tok = ename->value;
/*
* Check that ename is long enough for all of the fixed length
* header, and that the initial ID bytes are correct
*/
if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
return GSS_S_FAILURE;
/*
* Extract the OID, and check it. Here GSSAPI breaks with tradition
* and does use the OID type and length bytes. To confuse things
* there are two lengths - the first including these, and the
* second without.
*/
oidl = get_u16(tok+2); /* length including next two bytes */
oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
/*
* Check the BER encoding for correct type and length, that the
* string is long enough and that the OID matches that in our context
*/
if (tok[4] != 0x06 || tok[5] != oidl ||
ename->length < oidl+6 ||
!ssh_gssapi_check_oid(ctx, tok+6, oidl))
return GSS_S_FAILURE;
offset = oidl+6;
if (ename->length < offset+4)
return GSS_S_FAILURE;
name->length = get_u32(tok+offset);
offset += 4;
if (UINT_MAX - offset < name->length)
return GSS_S_FAILURE;
if (ename->length < offset+name->length)
return GSS_S_FAILURE;
name->value = xmalloc(name->length+1);
memcpy(name->value, tok+offset, name->length);
((char *)name->value)[name->length] = 0;
return GSS_S_COMPLETE;
}
/* Extract the client details from a given context. This can only reliably
* be called once for a context */
/* Privileged (called from accept_secure_ctx) */
OM_uint32
ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
{
int i = 0;
gss_buffer_desc ename;
client->mech = NULL;
while (supported_mechs[i]->name != NULL) {
if (supported_mechs[i]->oid.length == ctx->oid->length &&
(memcmp(supported_mechs[i]->oid.elements,
ctx->oid->elements, ctx->oid->length) == 0))
client->mech = supported_mechs[i];
i++;
}
if (client->mech == NULL)
return GSS_S_FAILURE;
if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
&client->displayname, NULL))) {
ssh_gssapi_error(ctx);
return (ctx->major);
}
if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
&ename))) {
ssh_gssapi_error(ctx);
return (ctx->major);
}
if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
&client->exportedname))) {
return (ctx->major);
}
/* We can't copy this structure, so we just move the pointer to it */
client->creds = ctx->client_creds;
ctx->client_creds = GSS_C_NO_CREDENTIAL;
return (ctx->major);
}
/* As user - called on fatal/exit */
void
ssh_gssapi_cleanup_creds(void)
{
if (gssapi_client.store.filename != NULL) {
/* Unlink probably isn't sufficient */
debug("removing gssapi cred file\"%s\"",
gssapi_client.store.filename);
unlink(gssapi_client.store.filename);
}
}
/* As user */
void
ssh_gssapi_storecreds(void)
{
if (gssapi_client.mech && gssapi_client.mech->storecreds) {
(*gssapi_client.mech->storecreds)(&gssapi_client);
} else
debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
}
/* This allows GSSAPI methods to do things to the childs environment based
* on the passed authentication process and credentials.
*/
/* As user */
void
ssh_gssapi_do_child(char ***envp, u_int *envsizep)
{
if (gssapi_client.store.envvar != NULL &&
gssapi_client.store.envval != NULL) {
debug("Setting %s to %s", gssapi_client.store.envvar,
gssapi_client.store.envval);
child_set_env(envp, envsizep, gssapi_client.store.envvar,
gssapi_client.store.envval);
}
}
/* Privileged */
int
ssh_gssapi_userok(char *user)
{
OM_uint32 lmin;
if (gssapi_client.exportedname.length == 0 ||
gssapi_client.exportedname.value == NULL) {
debug("No suitable client data");
return 0;
}
if (gssapi_client.mech && gssapi_client.mech->userok)
if ((*gssapi_client.mech->userok)(&gssapi_client, user))
return 1;
else {
/* Destroy delegated credentials if userok fails */
gss_release_buffer(&lmin, &gssapi_client.displayname);
gss_release_buffer(&lmin, &gssapi_client.exportedname);
gss_release_cred(&lmin, &gssapi_client.creds);
explicit_bzero(&gssapi_client,
sizeof(ssh_gssapi_client));
return 0;
}
else
debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
return (0);
}
/* Privileged */
OM_uint32
ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
{
ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
gssbuf, gssmic, NULL);
return (ctx->major);
}
#endif