/* $OpenBSD: gss-genr.c,v 1.31 2026/02/08 19:54:31 dtucker Exp $ */

/*
 * Copyright (c) 2001-2007 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.
 */

#ifdef GSSAPI

#include <sys/types.h>

#include <limits.h>
#include <stdarg.h>
#include <string.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>

#include "xmalloc.h"
#include "ssherr.h"
#include "sshbuf.h"
#include "log.h"
#include "ssh2.h"

#include "ssh-gss.h"

/* 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;
}

/* 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_f("sshbuf_new failed");

        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_fr(r, "assemble GSS_CODE");

                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_fr(r, "assemble MECH_CODE");

                gss_release_buffer(&lmin, &msg);
        } while (ctx != 0);

        if ((r = sshbuf_put_u8(b, '\n')) != 0)
                fatal_fr(r, "assemble newline");
        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,
            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;
        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_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(struct sshbuf *b, const char *user, const char *service,
    const char *context, const struct sshbuf *session_id)
{
        int r;

        sshbuf_reset(b);
        if ((r = sshbuf_put_stringb(b, session_id)) != 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_fr(r, "assemble buildmic");
}

int
ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
{
        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"};

        /* 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)) {
                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))
                ssh_gssapi_delete_ctx(ctx);

        return (!GSS_ERROR(major));
}

#endif /* GSSAPI */