/* $OpenBSD: gss-genr.c,v 1.3 2003/11/21 11:57:03 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 "ssh.h"
#include "xmalloc.h"
#include "bufaux.h"
#include "buffer.h"
#include "packet.h"
#include "compat.h"
#include <openssl/evp.h>
#include "cipher.h"
#include "kex.h"
#include "log.h"
#include "compat.h"
#include "monitor_wrap.h"
#include <netdb.h>
#include "ssh2.h"
#include "ssh-gss.h"
typedef struct {
char *encoded;
gss_OID oid;
} ssh_gss_kex_mapping;
static ssh_gss_kex_mapping *gss_enc2oid;
/* Return a list of the gss-group1-sha1-x mechanisms supported by this
* program.
*
* On the client side, we don't need to worry about whether we 'know'
* about the mechanism or not - we assume that any mechanism that we've been
* linked against is suitable for inclusion.
*
* XXX - We might want to make this configurable in the future, so as to
* XXX - allow the user control over which mechanisms to use.
*/
char *
ssh_gssapi_client_mechanisms(const char *host) {
gss_OID_set supported;
OM_uint32 min_status;
Buffer buf;
int i = 0;
char *mechs;
char *encoded;
int enclen;
char digest[EVP_MAX_MD_SIZE];
char deroid[2];
const EVP_MD *evp_md = EVP_md5();
EVP_MD_CTX md;
int oidpos=0;
gss_indicate_mechs(&min_status,&supported);
if (datafellows & SSH_BUG_GSSAPI_BER) {
gss_enc2oid=xmalloc(sizeof(ssh_gss_kex_mapping)
*((supported->count*2)+1));
} else {
gss_enc2oid=xmalloc(sizeof(ssh_gss_kex_mapping)
*(supported->count+1));
}
buffer_init(&buf);
for (i=0;i<supported->count;i++) {
gss_enc2oid[oidpos].encoded=NULL;
if (supported->elements[i].length<128 &&
ssh_gssapi_check_mechanism(&(supported->elements[i]),host)) {
/* Earlier versions of this code interpreted the
* spec incorrectly with regard to OID encoding. They
* also mis-encoded the krb5 OID. The following
* _temporary_ code interfaces with these broken
* servers */
if (datafellows & SSH_BUG_GSSAPI_BER) {
char *bodge=NULL;
gss_OID_desc krb5oid={9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"};
gss_OID_desc gsioid={9, "\x2B\x06\x01\x04\x01\x9B\x50\x01\x01"};
if (supported->elements[i].length==krb5oid.length &&
memcmp(supported->elements[i].elements,
krb5oid.elements, krb5oid.length)==0) {
bodge="Se3H81ismmOC3OE+FwYCiQ==";
}
if (supported->elements[i].length==gsioid.length &&
memcmp(supported->elements[i].elements,
gsioid.elements, gsioid.length)==0) {
bodge="N3+k7/4wGxHyuP8Yxi4RhA==";
}
if (bodge) {
if (oidpos!=0) {
buffer_put_char(&buf,',');
}
buffer_append(&buf, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1);
buffer_append(&buf, bodge, strlen(bodge));
gss_enc2oid[oidpos].oid=&(supported->elements[i]);
gss_enc2oid[oidpos].encoded=bodge;
oidpos++;
}
}
/* Add the required DER encoding octets and MD5 hash */
deroid[0]=0x06; /* Object Identifier */
deroid[1]=supported->elements[i].length;
EVP_DigestInit(&md, evp_md);
EVP_DigestUpdate(&md,deroid,2);
EVP_DigestUpdate(&md,
supported->elements[i].elements,
supported->elements[i].length);
EVP_DigestFinal(&md, digest, NULL);
/* Base64 encode it */
encoded=xmalloc(EVP_MD_size(evp_md)*2);
enclen=__b64_ntop(digest, EVP_MD_size(evp_md),
encoded,EVP_MD_size(evp_md)*2);
if (oidpos!=0) {
buffer_put_char(&buf,',');
}
buffer_append(&buf, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1);
buffer_append(&buf, encoded, enclen);
debug("Mechanism encoded as %s",encoded);
gss_enc2oid[oidpos].oid=&(supported->elements[i]);
gss_enc2oid[oidpos].encoded=encoded;
oidpos++;
}
}
gss_enc2oid[oidpos].oid=NULL;
gss_enc2oid[oidpos].encoded=NULL;
buffer_put_char(&buf,'\0');
mechs=xmalloc(buffer_len(&buf));
buffer_get(&buf,mechs,buffer_len(&buf));
buffer_free(&buf);
if (strlen(mechs)==0)
return(NULL);
else
return(mechs);
}
gss_OID
ssh_gssapi_client_id_kex(Gssctxt *ctx, char *name) {
int i=0;
if (strncmp(name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) !=0) {
return(NULL);
}
name+=sizeof(KEX_GSS_SHA1)-1; /* Move to the start of the ID string */
while (gss_enc2oid[i].encoded!=NULL &&
strcmp(name,gss_enc2oid[i].encoded)!=0) {
i++;
}
if (gss_enc2oid[i].oid!=NULL) {
ssh_gssapi_set_oid(ctx,gss_enc2oid[i].oid);
}
return gss_enc2oid[i].oid;
}
extern u_char *session_id2;
extern u_int session_id2_len;
/* 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) {
xfree(ctx->oid->elements);
xfree(ctx->oid);
}
ctx->oid = xmalloc(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)
{
debug("%s", ssh_gssapi_last_error(ctxt, NULL, NULL));
}
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;
Buffer b;
char *ret;
buffer_init(&b);
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, GSS_C_NULL_OID, &ctx, &msg);
buffer_append(&b, msg.value, msg.length);
buffer_put_char(&b, '\n');
gss_release_buffer(&lmin, &msg);
} while (ctx != 0);
/* The mechanism specific error */
do {
gss_display_status(&lmin, ctxt->minor,
GSS_C_MECH_CODE, GSS_C_NULL_OID, &ctx, &msg);
buffer_append(&b, msg.value, msg.length);
buffer_put_char(&b, '\n');
gss_release_buffer(&lmin, &msg);
} while (ctx != 0);
buffer_put_char(&b, '\0');
ret = xmalloc(buffer_len(&b));
buffer_get(&b, ret, buffer_len(&b));
buffer_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 = xmalloc(sizeof (Gssctxt));
(*ctx)->major = 0;
(*ctx)->minor = 0;
(*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) {
xfree((*ctx)->oid->elements);
xfree((*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);
xfree(*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,
GSS_C_NO_CREDENTIAL, &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;
gssbuf.length = sizeof("host@") + strlen(host);
gssbuf.value = xmalloc(gssbuf.length);
snprintf(gssbuf.value, gssbuf.length, "host@%s", host);
if ((ctx->major = gss_import_name(&ctx->minor,
&gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
ssh_gssapi_error(ctx);
xfree(gssbuf.value);
return (ctx->major);
}
/* Acquire credentials for a server running on the current host.
* Requires that the context structure contains a valid OID
*/
/* Returns a GSSAPI error code */
OM_uint32
ssh_gssapi_acquire_cred(Gssctxt *ctx)
{
OM_uint32 status;
char lname[MAXHOSTNAMELEN];
gss_OID_set oidset;
gss_create_empty_oid_set(&status, &oidset);
gss_add_oid_set_member(&status, ctx->oid, &oidset);
if (gethostname(lname, MAXHOSTNAMELEN))
return (-1);
if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname)))
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);
}
OM_uint32
ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
{
if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
GSS_C_QOP_DEFAULT, buffer, hash)))
ssh_gssapi_error(ctx);
return (ctx->major);
}
void
ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
const char *context)
{
buffer_init(b);
buffer_put_string(b, session_id2, session_id2_len);
buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
buffer_put_cstring(b, user);
buffer_put_cstring(b, service);
buffer_put_cstring(b, context);
}
int
ssh_gssapi_check_mechanism(gss_OID oid, const char *host)
{
Gssctxt * ctx = NULL;
gss_buffer_desc token;
OM_uint32 major,minor;
ssh_gssapi_build_ctx(&ctx);
ssh_gssapi_set_oid(ctx,oid);
ssh_gssapi_import_name(ctx, (char *) host);
major=ssh_gssapi_init_ctx(ctx,0, GSS_C_NO_BUFFER, &token, NULL);
gss_release_buffer(&minor,&token);
ssh_gssapi_delete_ctx(&ctx);
return(!GSS_ERROR(major));
}
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));
}
#endif /* GSSAPI */
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