/* $OpenBSD: auth-krb5.c,v 1.24 2021/04/03 06:18:40 djm Exp $ */
/*
 *    Kerberos v5 authentication and ticket-passing routines.
 *
 * From: FreeBSD: src/crypto/openssh/auth-krb5.c,v 1.6 2001/02/13 16:58:04 assar
 */
/*
 * Copyright (c) 2002 Daniel Kouril.  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"

#include <sys/types.h>
#include <pwd.h>
#include <stdarg.h>

#include "xmalloc.h"
#include "ssh.h"
#include "packet.h"
#include "log.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "misc.h"
#include "servconf.h"
#include "uidswap.h"
#include "hostfile.h"
#include "auth.h"

#ifdef KRB5
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <krb5.h>

extern ServerOptions     options;

static int
krb5_init(void *context)
{
        Authctxt *authctxt = (Authctxt *)context;
        krb5_error_code problem;

        if (authctxt->krb5_ctx == NULL) {
                problem = krb5_init_context(&authctxt->krb5_ctx);
                if (problem)
                        return (problem);
        }
        return (0);
}

int
auth_krb5_password(Authctxt *authctxt, const char *password)
{
#ifndef HEIMDAL
        krb5_creds creds;
        krb5_principal server;
#endif
        krb5_error_code problem;
        krb5_ccache ccache = NULL;
        int len;
        char *client, *platform_client;
        const char *errmsg;

        /* get platform-specific kerberos client principal name (if it exists) */
        platform_client = platform_krb5_get_principal_name(authctxt->pw->pw_name);
        client = platform_client ? platform_client : authctxt->pw->pw_name;

        temporarily_use_uid(authctxt->pw);

        problem = krb5_init(authctxt);
        if (problem)
                goto out;

        problem = krb5_parse_name(authctxt->krb5_ctx, client,
                    &authctxt->krb5_user);
        if (problem)
                goto out;

#ifdef HEIMDAL
# ifdef HAVE_KRB5_CC_NEW_UNIQUE
        problem = krb5_cc_new_unique(authctxt->krb5_ctx,
            krb5_mcc_ops.prefix, NULL, &ccache);
# else
        problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_mcc_ops, &ccache);
# endif
        if (problem)
                goto out;

        problem = krb5_cc_initialize(authctxt->krb5_ctx, ccache,
                authctxt->krb5_user);
        if (problem)
                goto out;

        restore_uid();

        problem = krb5_verify_user(authctxt->krb5_ctx, authctxt->krb5_user,
            ccache, password, 1, NULL);

        temporarily_use_uid(authctxt->pw);

        if (problem)
                goto out;

# ifdef HAVE_KRB5_CC_NEW_UNIQUE
        problem = krb5_cc_new_unique(authctxt->krb5_ctx,
            krb5_fcc_ops.prefix, NULL, &authctxt->krb5_fwd_ccache);
# else
        problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_fcc_ops,
            &authctxt->krb5_fwd_ccache);
# endif
        if (problem)
                goto out;

        problem = krb5_cc_copy_cache(authctxt->krb5_ctx, ccache,
            authctxt->krb5_fwd_ccache);
        krb5_cc_destroy(authctxt->krb5_ctx, ccache);
        ccache = NULL;
        if (problem)
                goto out;

#else
        problem = krb5_get_init_creds_password(authctxt->krb5_ctx, &creds,
            authctxt->krb5_user, (char *)password, NULL, NULL, 0, NULL, NULL);
        if (problem)
                goto out;

        problem = krb5_sname_to_principal(authctxt->krb5_ctx, NULL, NULL,
            KRB5_NT_SRV_HST, &server);
        if (problem)
                goto out;

        restore_uid();
        problem = krb5_verify_init_creds(authctxt->krb5_ctx, &creds, server,
            NULL, NULL, NULL);
        krb5_free_principal(authctxt->krb5_ctx, server);
        temporarily_use_uid(authctxt->pw);
        if (problem)
                goto out;

        if (!krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user,
            authctxt->pw->pw_name)) {
                problem = -1;
                goto out;
        }

        problem = ssh_krb5_cc_gen(authctxt->krb5_ctx,
            &authctxt->krb5_fwd_ccache);
        if (problem)
                goto out;

        problem = krb5_cc_initialize(authctxt->krb5_ctx,
            authctxt->krb5_fwd_ccache, authctxt->krb5_user);
        if (problem)
                goto out;

        problem = krb5_cc_store_cred(authctxt->krb5_ctx,
            authctxt->krb5_fwd_ccache, &creds);
        if (problem)
                goto out;
#endif

        authctxt->krb5_ticket_file = (char *)krb5_cc_get_name(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);

        len = strlen(authctxt->krb5_ticket_file) + 6;
        authctxt->krb5_ccname = xmalloc(len);
        snprintf(authctxt->krb5_ccname, len, "FILE:%s",
            authctxt->krb5_ticket_file);

#ifdef USE_PAM
        if (options.use_pam)
                do_pam_putenv("KRB5CCNAME", authctxt->krb5_ccname);
#endif

 out:
        restore_uid();
        
        free(platform_client);

        if (problem) {
                if (ccache)
                        krb5_cc_destroy(authctxt->krb5_ctx, ccache);

                if (authctxt->krb5_ctx != NULL && problem!=-1) {
                        errmsg = krb5_get_error_message(authctxt->krb5_ctx,
                            problem);
                        debug("Kerberos password authentication failed: %s",
                            errmsg);
                        krb5_free_error_message(authctxt->krb5_ctx, errmsg);
                } else
                        debug("Kerberos password authentication failed: %d",
                            problem);

                krb5_cleanup_proc(authctxt);

                if (options.kerberos_or_local_passwd)
                        return (-1);
                else
                        return (0);
        }
        return (authctxt->valid ? 1 : 0);
}

void
krb5_cleanup_proc(Authctxt *authctxt)
{
        debug("krb5_cleanup_proc called");
        if (authctxt->krb5_fwd_ccache) {
                krb5_cc_destroy(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
                authctxt->krb5_fwd_ccache = NULL;
        }
        if (authctxt->krb5_user) {
                krb5_free_principal(authctxt->krb5_ctx, authctxt->krb5_user);
                authctxt->krb5_user = NULL;
        }
        if (authctxt->krb5_ctx) {
                krb5_free_context(authctxt->krb5_ctx);
                authctxt->krb5_ctx = NULL;
        }
}

#ifndef HEIMDAL
krb5_error_code
ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
        int tmpfd, ret, oerrno;
        char ccname[40];
        mode_t old_umask;

        ret = snprintf(ccname, sizeof(ccname),
            "FILE:/tmp/krb5cc_%d_XXXXXXXXXX", geteuid());
        if (ret < 0 || (size_t)ret >= sizeof(ccname))
                return ENOMEM;

        old_umask = umask(0177);
        tmpfd = mkstemp(ccname + strlen("FILE:"));
        oerrno = errno;
        umask(old_umask);
        if (tmpfd == -1) {
                logit("mkstemp(): %.100s", strerror(oerrno));
                return oerrno;
        }

        if (fchmod(tmpfd,S_IRUSR | S_IWUSR) == -1) {
                oerrno = errno;
                logit("fchmod(): %.100s", strerror(oerrno));
                close(tmpfd);
                return oerrno;
        }
        close(tmpfd);

        return (krb5_cc_resolve(ctx, ccname, ccache));
}
#endif /* !HEIMDAL */
#endif /* KRB5 */