source: trunk/third/openssh/gss-genr.c @ 22574

/*      $OpenBSD: gss-genr.c,v 1.4 2005/07/17 07:17:55 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 "xmalloc.h"
#include "bufaux.h"
#include "compat.h"
#include "log.h"
#include "monitor_wrap.h"
#include "ssh2.h"
#include <openssl/evp.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;

/*
 * 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) {
        gss_OID_set gss_supported;
        OM_uint32 min_status;

        gss_indicate_mechs(&min_status, &gss_supported);

        return(ssh_gssapi_kex_mechs(gss_supported, ssh_gssapi_check_mechanism,
            (void *)host));
}

char *
ssh_gssapi_kex_mechs(gss_OID_set gss_supported, ssh_gssapi_check_fn *check,
    void *data) {
        Buffer buf;
        int i, oidpos, enclen;
        char *mechs, *encoded;
        char digest[EVP_MAX_MD_SIZE];
        char deroid[2];
        const EVP_MD *evp_md = EVP_md5();
        EVP_MD_CTX md;

        if (gss_enc2oid != NULL) {
                for (i=0;gss_enc2oid[i].encoded!=NULL;i++)
                        xfree(gss_enc2oid[i].encoded);
                xfree(gss_enc2oid);
        }

        if (datafellows & SSH_BUG_GSSAPI_BER) {
                gss_enc2oid=xmalloc(sizeof(ssh_gss_kex_mapping)
                                        *((gss_supported->count*2)+1));
        } else {
                gss_enc2oid=xmalloc(sizeof(ssh_gss_kex_mapping)
                                        *(gss_supported->count+1));
        }

        buffer_init(&buf);

        oidpos = 0;
        for (i=0;i<gss_supported->count;i++) {
                gss_enc2oid[oidpos].encoded = NULL;
        
                if (gss_supported->elements[i].length<128 &&
                    (*check)(&(gss_supported->elements[i]), data)) {

                        /* 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 (gss_supported->elements[i].length == krb5oid.length &&
                                    memcmp(gss_supported->elements[i].elements,
                                           krb5oid.elements, krb5oid.length) == 0) {
                                        bodge="Se3H81ismmOC3OE+FwYCiQ==";
                                }
                                
                                if (gss_supported->elements[i].length == gsioid.length &&
                                    memcmp(gss_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 = &(gss_supported->elements[i]);
                                        gss_enc2oid[oidpos].encoded = bodge;
                        
                                        oidpos++;
                                }
                        }
                        
                        /* Add the required DER encoding octets and MD5 hash */
                        deroid[0] = SSH_GSS_OIDTYPE;
                        deroid[1] = gss_supported->elements[i].length;
                        
                        EVP_DigestInit(&md, evp_md);
                        EVP_DigestUpdate(&md, deroid, 2);
                        EVP_DigestUpdate(&md,
                            gss_supported->elements[i].elements,
                            gss_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);

                        gss_enc2oid[oidpos].oid = &(gss_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) {
                xfree(mechs);
                mechs = NULL;
        }
        
        return (mechs);
}

gss_OID
ssh_gssapi_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; /* Skip ID string */

        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);

        debug("using GSSAPI mechanism %s:%s", KEX_GSS_SHA1, gss_enc2oid[i].encoded);

        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) {
                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 == 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(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);
}

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));
}

int
ssh_gssapi_check_mechanism(gss_OID oid, void *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, 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));
}

#endif /* GSSAPI */