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/* $OpenBSD: gss-genr.c,v 1.26 2018/07/10 09:13:30 djm Exp $ */
/*
* 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"
#ifdef GSSAPI
#include <sys/types.h>
#include <limits.h>
#include <stdarg.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include "xmalloc.h"
#include "ssherr.h"
#include "sshbuf.h"
#include "log.h"
#include "ssh2.h"
#include "cipher.h"
#include "sshkey.h"
#include "kex.h"
#include "digest.h"
#include "packet.h"
#include "ssh-gss.h"
extern u_char *session_id2;
extern u_int session_id2_len;
typedef struct {
char *encoded;
gss_OID oid;
} ssh_gss_kex_mapping;
/*
* XXX - It would be nice to find a more elegant way of handling the
* XXX passing of the key exchange context to the userauth routines
*/
Gssctxt *gss_kex_context = NULL;
static ssh_gss_kex_mapping *gss_enc2oid = NULL;
int
ssh_gssapi_oid_table_ok(void) {
return (gss_enc2oid != NULL);
}
/* sshbuf_get for gss_buffer_desc */
int
ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g)
{
int r;
u_char *p;
size_t len;
if ((r = sshbuf_get_string(b, &p, &len)) != 0)
return r;
g->value = p;
g->length = len;
return 0;
}
/* sshpkt_get of gss_buffer_desc */
int
ssh_gssapi_sshpkt_get_buffer_desc(struct ssh *ssh, gss_buffer_desc *g)
{
int r;
u_char *p;
size_t len;
if ((r = sshpkt_get_string(ssh, &p, &len)) != 0)
return r;
g->value = p;
g->length = len;
return 0;
}
/*
* Return a list of the gss-group1-sha1 mechanisms supported by this program
*
* We test mechanisms to ensure that we can use them, to avoid starting
* a key exchange with a bad mechanism
*/
char *
ssh_gssapi_client_mechanisms(const char *host, const char *client,
const char *kex) {
gss_OID_set gss_supported = NULL;
OM_uint32 min_status;
if (GSS_ERROR(gss_indicate_mechs(&min_status, &gss_supported)))
return NULL;
return ssh_gssapi_kex_mechs(gss_supported, ssh_gssapi_check_mechanism,
host, client, kex);
}
char *
ssh_gssapi_kex_mechs(gss_OID_set gss_supported, ssh_gssapi_check_fn *check,
const char *host, const char *client, const char *kex) {
struct sshbuf *buf = NULL;
size_t i;
int r = SSH_ERR_ALLOC_FAIL;
int oidpos, enclen;
char *mechs, *encoded;
u_char digest[SSH_DIGEST_MAX_LENGTH];
char deroid[2];
struct ssh_digest_ctx *md = NULL;
char *s, *cp, *p;
if (gss_enc2oid != NULL) {
for (i = 0; gss_enc2oid[i].encoded != NULL; i++)
free(gss_enc2oid[i].encoded);
free(gss_enc2oid);
}
gss_enc2oid = xmalloc(sizeof(ssh_gss_kex_mapping) *
(gss_supported->count + 1));
if ((buf = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
oidpos = 0;
s = cp = xstrdup(kex);
for (i = 0; i < gss_supported->count; i++) {
if (gss_supported->elements[i].length < 128 &&
(*check)(NULL, &(gss_supported->elements[i]), host, client)) {
deroid[0] = SSH_GSS_OIDTYPE;
deroid[1] = gss_supported->elements[i].length;
if ((md = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
(r = ssh_digest_update(md, deroid, 2)) != 0 ||
(r = ssh_digest_update(md,
gss_supported->elements[i].elements,
gss_supported->elements[i].length)) != 0 ||
(r = ssh_digest_final(md, digest, sizeof(digest))) != 0)
fatal("%s: digest failed: %s", __func__,
ssh_err(r));
ssh_digest_free(md);
md = NULL;
encoded = xmalloc(ssh_digest_bytes(SSH_DIGEST_MD5)
* 2);
enclen = __b64_ntop(digest,
ssh_digest_bytes(SSH_DIGEST_MD5), encoded,
ssh_digest_bytes(SSH_DIGEST_MD5) * 2);
cp = strncpy(s, kex, strlen(kex));
for ((p = strsep(&cp, ",")); p && *p != '\0';
(p = strsep(&cp, ","))) {
if (sshbuf_len(buf) != 0 &&
(r = sshbuf_put_u8(buf, ',')) != 0)
fatal("%s: sshbuf_put_u8 error: %s",
__func__, ssh_err(r));
if ((r = sshbuf_put(buf, p, strlen(p))) != 0 ||
(r = sshbuf_put(buf, encoded, enclen)) != 0)
fatal("%s: sshbuf_put error: %s",
__func__, ssh_err(r));
}
gss_enc2oid[oidpos].oid = &(gss_supported->elements[i]);
gss_enc2oid[oidpos].encoded = encoded;
oidpos++;
}
}
free(s);
gss_enc2oid[oidpos].oid = NULL;
gss_enc2oid[oidpos].encoded = NULL;
if ((mechs = sshbuf_dup_string(buf)) == NULL)
fatal("%s: sshbuf_dup_string failed", __func__);
sshbuf_free(buf);
if (strlen(mechs) == 0) {
free(mechs);
mechs = NULL;
}
return (mechs);
}
gss_OID
ssh_gssapi_id_kex(Gssctxt *ctx, char *name, int kex_type) {
int i = 0;
#define SKIP_KEX_NAME(type) \
case type: \
if (strlen(name) < sizeof(type##_ID)) \
return GSS_C_NO_OID; \
name += sizeof(type##_ID) - 1; \
break;
switch (kex_type) {
SKIP_KEX_NAME(KEX_GSS_GRP1_SHA1)
SKIP_KEX_NAME(KEX_GSS_GRP14_SHA1)
SKIP_KEX_NAME(KEX_GSS_GRP14_SHA256)
SKIP_KEX_NAME(KEX_GSS_GRP16_SHA512)
SKIP_KEX_NAME(KEX_GSS_GEX_SHA1)
SKIP_KEX_NAME(KEX_GSS_NISTP256_SHA256)
SKIP_KEX_NAME(KEX_GSS_C25519_SHA256)
default:
return GSS_C_NO_OID;
}
#undef SKIP_KEX_NAME
while (gss_enc2oid[i].encoded != NULL &&
strcmp(name, gss_enc2oid[i].encoded) != 0)
i++;
if (gss_enc2oid[i].oid != NULL && ctx != NULL)
ssh_gssapi_set_oid(ctx, gss_enc2oid[i].oid);
return gss_enc2oid[i].oid;
}
/* Check that the OID in a data stream matches that in the context */
int
ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
{
return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
ctx->oid->length == len &&
memcmp(ctx->oid->elements, data, len) == 0);
}
/* Set the contexts OID from a data stream */
void
ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
{
if (ctx->oid != GSS_C_NO_OID) {
free(ctx->oid->elements);
free(ctx->oid);
}
ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
ctx->oid->length = len;
ctx->oid->elements = xmalloc(len);
memcpy(ctx->oid->elements, data, len);
}
/* Set the contexts OID */
void
ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
{
ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
}
/* All this effort to report an error ... */
void
ssh_gssapi_error(Gssctxt *ctxt)
{
char *s;
s = ssh_gssapi_last_error(ctxt, NULL, NULL);
debug("%s", s);
free(s);
}
char *
ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
OM_uint32 *minor_status)
{
OM_uint32 lmin;
gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
OM_uint32 ctx;
struct sshbuf *b;
char *ret;
int r;
if ((b = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
if (major_status != NULL)
*major_status = ctxt->major;
if (minor_status != NULL)
*minor_status = ctxt->minor;
ctx = 0;
/* The GSSAPI error */
do {
gss_display_status(&lmin, ctxt->major,
GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
(r = sshbuf_put_u8(b, '\n')) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
gss_release_buffer(&lmin, &msg);
} while (ctx != 0);
/* The mechanism specific error */
do {
gss_display_status(&lmin, ctxt->minor,
GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 ||
(r = sshbuf_put_u8(b, '\n')) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
gss_release_buffer(&lmin, &msg);
} while (ctx != 0);
if ((r = sshbuf_put_u8(b, '\n')) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
ret = xstrdup((const char *)sshbuf_ptr(b));
sshbuf_free(b);
return (ret);
}
/*
* Initialise our GSSAPI context. We use this opaque structure to contain all
* of the data which both the client and server need to persist across
* {accept,init}_sec_context calls, so that when we do it from the userauth
* stuff life is a little easier
*/
void
ssh_gssapi_build_ctx(Gssctxt **ctx)
{
*ctx = xcalloc(1, sizeof (Gssctxt));
(*ctx)->context = GSS_C_NO_CONTEXT;
(*ctx)->name = GSS_C_NO_NAME;
(*ctx)->oid = GSS_C_NO_OID;
(*ctx)->creds = GSS_C_NO_CREDENTIAL;
(*ctx)->client = GSS_C_NO_NAME;
(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
}
/* Delete our context, providing it has been built correctly */
void
ssh_gssapi_delete_ctx(Gssctxt **ctx)
{
OM_uint32 ms;
if ((*ctx) == NULL)
return;
if ((*ctx)->context != GSS_C_NO_CONTEXT)
gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
if ((*ctx)->name != GSS_C_NO_NAME)
gss_release_name(&ms, &(*ctx)->name);
if ((*ctx)->oid != GSS_C_NO_OID) {
free((*ctx)->oid->elements);
free((*ctx)->oid);
(*ctx)->oid = GSS_C_NO_OID;
}
if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
gss_release_cred(&ms, &(*ctx)->creds);
if ((*ctx)->client != GSS_C_NO_NAME)
gss_release_name(&ms, &(*ctx)->client);
if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
gss_release_cred(&ms, &(*ctx)->client_creds);
free(*ctx);
*ctx = NULL;
}
/*
* Wrapper to init_sec_context
* Requires that the context contains:
* oid
* server name (from ssh_gssapi_import_name)
*/
OM_uint32
ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
gss_buffer_desc* send_tok, OM_uint32 *flags)
{
int deleg_flag = 0;
if (deleg_creds) {
deleg_flag = GSS_C_DELEG_FLAG;
debug("Delegating credentials");
}
ctx->major = gss_init_sec_context(&ctx->minor,
ctx->client_creds, &ctx->context, ctx->name, ctx->oid,
GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
0, NULL, recv_tok, NULL, send_tok, flags, NULL);
if (GSS_ERROR(ctx->major))
ssh_gssapi_error(ctx);
return (ctx->major);
}
/* Create a service name for the given host */
OM_uint32
ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
{
gss_buffer_desc gssbuf;
char *val;
xasprintf(&val, "host@%s", host);
gssbuf.value = val;
gssbuf.length = strlen(gssbuf.value);
if ((ctx->major = gss_import_name(&ctx->minor,
&gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
ssh_gssapi_error(ctx);
free(gssbuf.value);
return (ctx->major);
}
OM_uint32
ssh_gssapi_client_identity(Gssctxt *ctx, const char *name)
{
gss_buffer_desc gssbuf;
gss_name_t gssname;
OM_uint32 status;
gss_OID_set oidset;
gssbuf.value = (void *) name;
gssbuf.length = strlen(gssbuf.value);
gss_create_empty_oid_set(&status, &oidset);
gss_add_oid_set_member(&status, ctx->oid, &oidset);
ctx->major = gss_import_name(&ctx->minor, &gssbuf,
GSS_C_NT_USER_NAME, &gssname);
if (!ctx->major)
ctx->major = gss_acquire_cred(&ctx->minor,
gssname, 0, oidset, GSS_C_INITIATE,
&ctx->client_creds, NULL, NULL);
gss_release_name(&status, &gssname);
gss_release_oid_set(&status, &oidset);
if (ctx->major)
ssh_gssapi_error(ctx);
return(ctx->major);
}
OM_uint32
ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
{
if (ctx == NULL)
return -1;
if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
GSS_C_QOP_DEFAULT, buffer, hash)))
ssh_gssapi_error(ctx);
return (ctx->major);
}
/* Priviledged when used by server */
OM_uint32
ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
{
if (ctx == NULL)
return -1;
ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
gssbuf, gssmic, NULL);
return (ctx->major);
}
void
ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service,
const char *context)
{
int r;
sshbuf_reset(b);
if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
(r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshbuf_put_cstring(b, user)) != 0 ||
(r = sshbuf_put_cstring(b, service)) != 0 ||
(r = sshbuf_put_cstring(b, context)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
}
int
ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host,
const char *client)
{
gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
OM_uint32 major, minor;
gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
Gssctxt *intctx = NULL;
if (ctx == NULL)
ctx = &intctx;
/* RFC 4462 says we MUST NOT do SPNEGO */
if (oid->length == spnego_oid.length &&
(memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
return 0; /* false */
ssh_gssapi_build_ctx(ctx);
ssh_gssapi_set_oid(*ctx, oid);
major = ssh_gssapi_import_name(*ctx, host);
if (!GSS_ERROR(major) && client)
major = ssh_gssapi_client_identity(*ctx, client);
if (!GSS_ERROR(major)) {
major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
NULL);
gss_release_buffer(&minor, &token);
if ((*ctx)->context != GSS_C_NO_CONTEXT)
gss_delete_sec_context(&minor, &(*ctx)->context,
GSS_C_NO_BUFFER);
}
if (GSS_ERROR(major) || intctx != NULL)
ssh_gssapi_delete_ctx(ctx);
return (!GSS_ERROR(major));
}
int
ssh_gssapi_credentials_updated(Gssctxt *ctxt) {
static gss_name_t saved_name = GSS_C_NO_NAME;
static OM_uint32 saved_lifetime = 0;
static gss_OID saved_mech = GSS_C_NO_OID;
static gss_name_t name;
static OM_uint32 last_call = 0;
OM_uint32 lifetime, now, major, minor;
int equal;
now = time(NULL);
if (ctxt) {
debug("Rekey has happened - updating saved versions");
if (saved_name != GSS_C_NO_NAME)
gss_release_name(&minor, &saved_name);
major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL,
&saved_name, &saved_lifetime, NULL, NULL);
if (!GSS_ERROR(major)) {
saved_mech = ctxt->oid;
saved_lifetime+= now;
} else {
/* Handle the error */
}
return 0;
}
if (now - last_call < 10)
return 0;
last_call = now;
if (saved_mech == GSS_C_NO_OID)
return 0;
major = gss_inquire_cred(&minor, GSS_C_NO_CREDENTIAL,
&name, &lifetime, NULL, NULL);
if (major == GSS_S_CREDENTIALS_EXPIRED)
return 0;
else if (GSS_ERROR(major))
return 0;
major = gss_compare_name(&minor, saved_name, name, &equal);
gss_release_name(&minor, &name);
if (GSS_ERROR(major))
return 0;
if (equal && (saved_lifetime < lifetime + now - 10))
return 1;
return 0;
}
#endif /* GSSAPI */
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