lib/krb5/fcache.c

/*        $NetBSD: fcache.c,v 1.2 2017/01/28 21:31:49 christos Exp $  */

/*
 * Copyright (c) 1997 - 2008 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Portions Copyright (c) 2009 Apple Inc. 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.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``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 INSTITUTE OR CONTRIBUTORS 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 "krb5_locl.h"

typedef struct krb5_fcache{
    char *filename;
    int version;
}krb5_fcache;

struct fcc_cursor {
    int fd;
    off_t cred_start;
    off_t cred_end;
    krb5_storage *sp;
};

#define KRB5_FCC_FVNO_1 1
#define KRB5_FCC_FVNO_2 2
#define KRB5_FCC_FVNO_3 3
#define KRB5_FCC_FVNO_4 4

#define FCC_TAG_DELTATIME 1

#define FCACHE(X) ((krb5_fcache*)(X)->data.data)

#define FILENAME(X) (FCACHE(X)->filename)

#define FCC_CURSOR(C) ((struct fcc_cursor*)(C))

static const char* KRB5_CALLCONV
fcc_get_name(krb5_context context,
               krb5_ccache id)
{
    if (FCACHE(id) == NULL)
        return NULL;

    return FILENAME(id);
}

KRB5_LIB_FUNCTION int KRB5_LIB_CALL
_krb5_xlock(krb5_context context, int fd, krb5_boolean exclusive,
              const char *filename)
{
    int ret;
#ifdef HAVE_FCNTL
    struct flock l;

    l.l_start = 0;
    l.l_len = 0;
    l.l_type = exclusive ? F_WRLCK : F_RDLCK;
    l.l_whence = SEEK_SET;
    ret = fcntl(fd, F_SETLKW, &l);
#else
    ret = flock(fd, exclusive ? LOCK_EX : LOCK_SH);
#endif
    if(ret < 0)
          ret = errno;
    if(ret == EACCES) /* fcntl can return EACCES instead of EAGAIN */
          ret = EAGAIN;

    switch (ret) {
    case 0:
          break;
    case EINVAL: /* filesystem doesn't support locking, let the user have it */
          ret = 0;
          break;
    case EAGAIN:
          krb5_set_error_message(context, ret,
                                     N_("timed out locking cache file %s", "file"),
                                     filename);
          break;
    default: {
          char buf[128];
          rk_strerror_r(ret, buf, sizeof(buf));
          krb5_set_error_message(context, ret,
                                     N_("error locking cache file %s: %s",
                                          "file, error"), filename, buf);
          break;
    }
    }
    return ret;
}

KRB5_LIB_FUNCTION int KRB5_LIB_CALL
_krb5_xunlock(krb5_context context, int fd)
{
    int ret;
#ifdef HAVE_FCNTL
    struct flock l;
    l.l_start = 0;
    l.l_len = 0;
    l.l_type = F_UNLCK;
    l.l_whence = SEEK_SET;
    ret = fcntl(fd, F_SETLKW, &l);
#else
    ret = flock(fd, LOCK_UN);
#endif
    if (ret < 0)
          ret = errno;
    switch (ret) {
    case 0:
          break;
    case EINVAL: /* filesystem doesn't support locking, let the user have it */
          ret = 0;
          break;
    default: {
          char buf[128];
          rk_strerror_r(ret, buf, sizeof(buf));
          krb5_set_error_message(context, ret,
                                     N_("Failed to unlock file: %s", ""), buf);
          break;
    }
    }
    return ret;
}

static krb5_error_code
write_storage(krb5_context context, krb5_storage *sp, int fd)
{
    krb5_error_code ret;
    krb5_data data;
    ssize_t sret;

    ret = krb5_storage_to_data(sp, &data);
    if (ret) {
          krb5_set_error_message(context, ret, N_("malloc: out of memory", ""));
          return ret;
    }
    sret = write(fd, data.data, data.length);
    ret = (sret != (ssize_t)data.length);
    krb5_data_free(&data);
    if (ret) {
          ret = errno;
          krb5_set_error_message(context, ret,
                                     N_("Failed to write FILE credential data", ""));
          return ret;
    }
    return 0;
}


static krb5_error_code KRB5_CALLCONV
fcc_lock(krb5_context context, krb5_ccache id,
           int fd, krb5_boolean exclusive)
{
    return _krb5_xlock(context, fd, exclusive, fcc_get_name(context, id));
}

static krb5_error_code KRB5_CALLCONV
fcc_unlock(krb5_context context, int fd)
{
    return _krb5_xunlock(context, fd);
}

static krb5_error_code KRB5_CALLCONV
fcc_resolve(krb5_context context, krb5_ccache *id, const char *res)
{
    krb5_fcache *f;
    f = malloc(sizeof(*f));
    if(f == NULL) {
          krb5_set_error_message(context, KRB5_CC_NOMEM,
                                     N_("malloc: out of memory", ""));
          return KRB5_CC_NOMEM;
    }
    f->filename = strdup(res);
    if(f->filename == NULL){
          free(f);
          krb5_set_error_message(context, KRB5_CC_NOMEM,
                                     N_("malloc: out of memory", ""));
          return KRB5_CC_NOMEM;
    }
    f->version = 0;
    (*id)->data.data = f;
    (*id)->data.length = sizeof(*f);
    return 0;
}

/*
 * Try to scrub the contents of `filename' safely.
 */

static int
scrub_file (int fd)
{
    off_t pos;
    char buf[128];

    pos = lseek(fd, 0, SEEK_END);
    if (pos < 0)
        return errno;
    if (lseek(fd, 0, SEEK_SET) < 0)
        return errno;
    memset(buf, 0, sizeof(buf));
    while(pos > 0) {
          ssize_t tmp;
          size_t wr = sizeof(buf);
          if (wr > pos)
              wr = (size_t)pos;
        tmp = write(fd, buf, wr);

          if (tmp < 0)
              return errno;
          pos -= tmp;
    }
#ifdef _MSC_VER
    _commit (fd);
#else
    fsync (fd);
#endif
    return 0;
}

/*
 * Erase `filename' if it exists, trying to remove the contents if
 * it's `safe'.  We always try to remove the file, it it exists.  It's
 * only overwritten if it's a regular file (not a symlink and not a
 * hardlink)
 */

KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
_krb5_erase_file(krb5_context context, const char *filename)
{
    int fd;
    struct stat sb1, sb2;
    int ret;

    ret = lstat (filename, &sb1);
    if (ret < 0)
          return errno;

    fd = open(filename, O_RDWR | O_BINARY | O_CLOEXEC | O_NOFOLLOW);
    if(fd < 0) {
          if(errno == ENOENT)
              return 0;
          else
              return errno;
    }
    rk_cloexec(fd);
    ret = _krb5_xlock(context, fd, 1, filename);
    if (ret) {
          close(fd);
          return ret;
    }
    if (unlink(filename) < 0) {
          ret = errno;
          _krb5_xunlock(context, fd);
        close (fd);
          krb5_set_error_message(context, errno,
              N_("krb5_cc_destroy: unlinking \"%s\": %s", ""),
              filename, strerror(ret));
        return ret;
    }
    ret = fstat(fd, &sb2);
    if (ret < 0) {
          ret = errno;
          _krb5_xunlock(context, fd);
          close (fd);
          return ret;
    }

    /* check if someone was playing with symlinks */

    if (sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino) {
          _krb5_xunlock(context, fd);
          close(fd);
          return EPERM;
    }

    /* there are still hard links to this file */

    if (sb2.st_nlink != 0) {
          _krb5_xunlock(context, fd);
        close(fd);
        return 0;
    }

    ret = scrub_file(fd);
    if (ret) {
          _krb5_xunlock(context, fd);
          close(fd);
          return ret;
    }
    ret = _krb5_xunlock(context, fd);
    close(fd);
    return ret;
}

static krb5_error_code KRB5_CALLCONV
fcc_gen_new(krb5_context context, krb5_ccache *id)
{
    char *file = NULL, *exp_file = NULL;
    krb5_error_code ret;
    krb5_fcache *f;
    int fd;

    f = malloc(sizeof(*f));
    if(f == NULL) {
          krb5_set_error_message(context, KRB5_CC_NOMEM,
                                     N_("malloc: out of memory", ""));
          return KRB5_CC_NOMEM;
    }
    ret = asprintf(&file, "%sXXXXXX", KRB5_DEFAULT_CCFILE_ROOT);
    if(ret < 0 || file == NULL) {
          free(f);
          krb5_set_error_message(context, KRB5_CC_NOMEM,
                                     N_("malloc: out of memory", ""));
          return KRB5_CC_NOMEM;
    }
    ret = _krb5_expand_path_tokens(context, file, 1, &exp_file);
    free(file);
    if (ret) {
          free(f);
          return ret;
    }

    file = exp_file;

    fd = mkstemp(exp_file);
    if(fd < 0) {
          ret = (krb5_error_code)errno;
          krb5_set_error_message(context, ret, N_("mkstemp %s failed", ""), exp_file);
          free(f);
          free(exp_file);
          return ret;
    }
    close(fd);
    f->filename = exp_file;
    f->version = 0;
    (*id)->data.data = f;
    (*id)->data.length = sizeof(*f);
    return 0;
}

static void
storage_set_flags(krb5_context context, krb5_storage *sp, int vno)
{
    int flags = 0;
    switch(vno) {
    case KRB5_FCC_FVNO_1:
          flags |= KRB5_STORAGE_PRINCIPAL_WRONG_NUM_COMPONENTS;
          flags |= KRB5_STORAGE_PRINCIPAL_NO_NAME_TYPE;
          flags |= KRB5_STORAGE_HOST_BYTEORDER;
          break;
    case KRB5_FCC_FVNO_2:
          flags |= KRB5_STORAGE_HOST_BYTEORDER;
          break;
    case KRB5_FCC_FVNO_3:
          flags |= KRB5_STORAGE_KEYBLOCK_KEYTYPE_TWICE;
          break;
    case KRB5_FCC_FVNO_4:
          break;
    default:
          krb5_abortx(context,
                        "storage_set_flags called with bad vno (%x)", vno);
    }
    krb5_storage_set_flags(sp, flags);
}

static krb5_error_code KRB5_CALLCONV
fcc_open(krb5_context context,
           krb5_ccache id,
           const char *operation,
           int *fd_ret,
           int flags,
           mode_t mode)
{
    krb5_boolean exclusive = ((flags | O_WRONLY) == flags ||
                                    (flags | O_RDWR) == flags);
    krb5_error_code ret;
    const char *filename;
    struct stat sb1, sb2;
#ifndef _WIN32
    struct stat sb3;
    size_t tries = 3;
#endif
    int strict_checking;
    int fd;

    flags |= O_BINARY | O_CLOEXEC | O_NOFOLLOW;

    *fd_ret = -1;

    if (FCACHE(id) == NULL)
        return krb5_einval(context, 2);

    filename = FILENAME(id);

    strict_checking = (flags & O_CREAT) == 0 &&
          (context->flags & KRB5_CTX_F_FCACHE_STRICT_CHECKING) != 0;

again:
    memset(&sb1, 0, sizeof(sb1));
    ret = lstat(filename, &sb1);
    if (ret == 0) {
          if (!S_ISREG(sb1.st_mode)) {
              krb5_set_error_message(context, EPERM,
                                           N_("Refuses to open symlinks for caches FILE:%s", ""), filename);
              return EPERM;
          }
    } else if (errno != ENOENT || !(flags & O_CREAT)) {
          krb5_set_error_message(context, errno, N_("%s lstat(%s)", "file, error"),
                                     operation, filename);
          return errno;
    }

    fd = open(filename, flags, mode);
    if(fd < 0) {
          char buf[128];
          ret = errno;
          rk_strerror_r(ret, buf, sizeof(buf));
          krb5_set_error_message(context, ret, N_("%s open(%s): %s", "file, error"),
                                     operation, filename, buf);
          return ret;
    }
    rk_cloexec(fd);

    ret = fstat(fd, &sb2);
    if (ret < 0) {
          krb5_clear_error_message(context);
          close(fd);
          return errno;
    }

    if (!S_ISREG(sb2.st_mode)) {
          krb5_set_error_message(context, EPERM, N_("Refuses to open non files caches: FILE:%s", ""), filename);
          close(fd);
          return EPERM;
    }

#ifndef _WIN32
    if (sb1.st_dev && sb1.st_ino &&
          (sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino)) {
          /*
           * Perhaps we raced with a rename().  To complain about
           * symlinks in that case would cause unnecessary concern, so
           * we check for that possibility and loop.  This has no
           * TOCTOU problems because we redo the open().  We could also
           * not do any of this checking if O_NOFOLLOW != 0...
           */
          close(fd);
          ret = lstat(filename, &sb3);
          if (ret || sb1.st_dev != sb2.st_dev ||
              sb3.st_dev != sb2.st_dev || sb3.st_ino != sb2.st_ino) {
              krb5_set_error_message(context, EPERM, N_("Refuses to open possible symlink for caches: FILE:%s", ""), filename);
              return EPERM;
          }
          if (--tries == 0) {
              krb5_set_error_message(context, EPERM, N_("Raced too many times with renames of FILE:%s", ""), filename);
              return EPERM;
          }
          goto again;
    }
#endif

    /*
     * /tmp (or wherever default ccaches go) might not be on its own
     * filesystem, or on a filesystem different /etc, say, and even if
     * it were, suppose a user hard-links another's ccache to her
     * default ccache, then runs a set-uid program that will user her
     * default ccache (even if it ignores KRB5CCNAME)...
     *
     * Default ccache locations should really be on per-user non-tmp
     * locations on tmpfs "run" directories.  But we don't know here
     * that this is the case.  Thus: no hard-links, no symlinks.
     */
    if (sb2.st_nlink != 1) {
          krb5_set_error_message(context, EPERM, N_("Refuses to open hardlinks for caches FILE:%s", ""), filename);
          close(fd);
          return EPERM;
    }

    if (strict_checking) {
#ifndef _WIN32
          /*
           * XXX WIN32: Needs to have ACL checking code!
           * st_mode comes out as 100666, and st_uid is no use.
           */
          /*
           * XXX Should probably add options to improve control over this
           * check.  We might want strict checking of everything except
           * this.
           */
          if (sb2.st_uid != geteuid()) {
              krb5_set_error_message(context, EPERM, N_("Refuses to open cache files not own by myself FILE:%s (owned by %d)", ""), filename, (int)sb2.st_uid);
              close(fd);
              return EPERM;
          }
          if ((sb2.st_mode & 077) != 0) {
              krb5_set_error_message(context, EPERM,
                                           N_("Refuses to open group/other readable files FILE:%s", ""), filename);
              close(fd);
              return EPERM;
          }
#endif
    }

    if((ret = fcc_lock(context, id, fd, exclusive)) != 0) {
          close(fd);
          return ret;
    }
    *fd_ret = fd;
    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_initialize(krb5_context context,
                 krb5_ccache id,
                 krb5_principal primary_principal)
{
    krb5_fcache *f = FCACHE(id);
    int ret = 0;
    int fd;

    if (f == NULL)
        return krb5_einval(context, 2);

    unlink (f->filename);

    ret = fcc_open(context, id, "initialize", &fd, O_RDWR | O_CREAT | O_EXCL, 0600);
    if(ret)
          return ret;
    {
          krb5_storage *sp;
          sp = krb5_storage_emem();
          krb5_storage_set_eof_code(sp, KRB5_CC_END);
          if(context->fcache_vno != 0)
              f->version = context->fcache_vno;
          else
              f->version = KRB5_FCC_FVNO_4;
          ret |= krb5_store_int8(sp, 5);
          ret |= krb5_store_int8(sp, f->version);
          storage_set_flags(context, sp, f->version);
          if(f->version == KRB5_FCC_FVNO_4 && ret == 0) {
              /* V4 stuff */
              if (context->kdc_sec_offset) {
                    ret |= krb5_store_int16 (sp, 12); /* length */
                    ret |= krb5_store_int16 (sp, FCC_TAG_DELTATIME); /* Tag */
                    ret |= krb5_store_int16 (sp, 8); /* length of data */
                    ret |= krb5_store_int32 (sp, context->kdc_sec_offset);
                    ret |= krb5_store_int32 (sp, context->kdc_usec_offset);
              } else {
                    ret |= krb5_store_int16 (sp, 0);
              }
          }
          ret |= krb5_store_principal(sp, primary_principal);

          ret |= write_storage(context, sp, fd);

          krb5_storage_free(sp);
    }
    fcc_unlock(context, fd);
    if (close(fd) < 0)
          if (ret == 0) {
              char buf[128];
              ret = errno;
              rk_strerror_r(ret, buf, sizeof(buf));
              krb5_set_error_message(context, ret, N_("close %s: %s", ""),
                                           FILENAME(id), buf);
          }
    return ret;
}

static krb5_error_code KRB5_CALLCONV
fcc_close(krb5_context context,
            krb5_ccache id)
{
    if (FCACHE(id) == NULL)
        return krb5_einval(context, 2);

    free (FILENAME(id));
    krb5_data_free(&id->data);
    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_destroy(krb5_context context,
              krb5_ccache id)
{
    if (FCACHE(id) == NULL)
        return krb5_einval(context, 2);

    return _krb5_erase_file(context, FILENAME(id));
}

static krb5_error_code KRB5_CALLCONV
fcc_store_cred(krb5_context context,
                 krb5_ccache id,
                 krb5_creds *creds)
{
    int ret;
    int fd;

    ret = fcc_open(context, id, "store", &fd, O_WRONLY | O_APPEND, 0);
    if(ret)
          return ret;
    {
          krb5_storage *sp;

          sp = krb5_storage_emem();
          krb5_storage_set_eof_code(sp, KRB5_CC_END);
          storage_set_flags(context, sp, FCACHE(id)->version);
          ret = krb5_store_creds(sp, creds);
          if (ret == 0)
              ret = write_storage(context, sp, fd);
          krb5_storage_free(sp);
    }
    fcc_unlock(context, fd);
    if (close(fd) < 0) {
          if (ret == 0) {
              char buf[128];
              ret = errno;
              rk_strerror_r(ret, buf, sizeof(buf));
              krb5_set_error_message(context, ret, N_("close %s: %s", ""),
                                           FILENAME(id), buf);
          }
    }
    return ret;
}

static krb5_error_code
init_fcc(krb5_context context,
           krb5_ccache id,
           const char *operation,
           krb5_storage **ret_sp,
           int *ret_fd,
           krb5_deltat *kdc_offset)
{
    int fd;
    int8_t pvno, tag;
    krb5_storage *sp;
    krb5_error_code ret;

    *ret_fd = -1;
    *ret_sp = NULL;
    if (kdc_offset)
          *kdc_offset = 0;

    ret = fcc_open(context, id, operation, &fd, O_RDONLY, 0);
    if(ret)
          return ret;

    sp = krb5_storage_from_fd(fd);
    if(sp == NULL) {
          krb5_clear_error_message(context);
          ret = ENOMEM;
          goto out;
    }
    krb5_storage_set_eof_code(sp, KRB5_CC_END);
    ret = krb5_ret_int8(sp, &pvno);
    if (ret != 0) {
          if(ret == KRB5_CC_END) {
              ret = ENOENT;
              krb5_set_error_message(context, ret,
                                           N_("Empty credential cache file: %s", ""),
                                           FILENAME(id));
          } else
              krb5_set_error_message(context, ret, N_("Error reading pvno "
                                                                "in cache file: %s", ""),
                                           FILENAME(id));
          goto out;
    }
    if (pvno != 5) {
          ret = KRB5_CCACHE_BADVNO;
          krb5_set_error_message(context, ret, N_("Bad version number in credential "
                                                            "cache file: %s", ""),
                                     FILENAME(id));
          goto out;
    }
    ret = krb5_ret_int8(sp, &tag); /* should not be host byte order */
    if (ret != 0) {
          ret = KRB5_CC_FORMAT;
          krb5_set_error_message(context, ret, "Error reading tag in "
                                    "cache file: %s", FILENAME(id));
          goto out;
    }
    FCACHE(id)->version = tag;
    storage_set_flags(context, sp, FCACHE(id)->version);
    switch (tag) {
    case KRB5_FCC_FVNO_4: {
          int16_t length;

          ret = krb5_ret_int16 (sp, &length);
          if(ret) {
              ret = KRB5_CC_FORMAT;
              krb5_set_error_message(context, ret,
                                           N_("Error reading tag length in "
                                              "cache file: %s", ""), FILENAME(id));
              goto out;
          }
          while(length > 0) {
              int16_t dtag, data_len;
              int i;
              int8_t dummy;

              ret = krb5_ret_int16 (sp, &dtag);
              if(ret) {
                    ret = KRB5_CC_FORMAT;
                    krb5_set_error_message(context, ret, N_("Error reading dtag in "
                                                                      "cache file: %s", ""),
                                               FILENAME(id));
                    goto out;
              }
              ret = krb5_ret_int16 (sp, &data_len);
              if(ret) {
                    ret = KRB5_CC_FORMAT;
                    krb5_set_error_message(context, ret,
                                               N_("Error reading dlength "
                                                    "in cache file: %s",""),
                                               FILENAME(id));
                    goto out;
              }
              switch (dtag) {
              case FCC_TAG_DELTATIME : {
                    int32_t offset;

                    ret = krb5_ret_int32 (sp, &offset);
                    ret |= krb5_ret_int32 (sp, &context->kdc_usec_offset);
                    if(ret) {
                        ret = KRB5_CC_FORMAT;
                        krb5_set_error_message(context, ret,
                                                     N_("Error reading kdc_sec in "
                                                        "cache file: %s", ""),
                                                     FILENAME(id));
                        goto out;
                    }
                    context->kdc_sec_offset = offset;
                    if (kdc_offset)
                        *kdc_offset = offset;
                    break;
              }
              default :
                    for (i = 0; i < data_len; ++i) {
                        ret = krb5_ret_int8 (sp, &dummy);
                        if(ret) {
                              ret = KRB5_CC_FORMAT;
                              krb5_set_error_message(context, ret,
                                                         N_("Error reading unknown "
                                                              "tag in cache file: %s", ""),
                                                         FILENAME(id));
                              goto out;
                        }
                    }
                    break;
              }
              length -= 4 + data_len;
          }
          break;
    }
    case KRB5_FCC_FVNO_3:
    case KRB5_FCC_FVNO_2:
    case KRB5_FCC_FVNO_1:
          break;
    default :
          ret = KRB5_CCACHE_BADVNO;
          krb5_set_error_message(context, ret,
                                     N_("Unknown version number (%d) in "
                                          "credential cache file: %s", ""),
                                     (int)tag, FILENAME(id));
          goto out;
    }
    *ret_sp = sp;
    *ret_fd = fd;

    return 0;
  out:
    if(sp != NULL)
          krb5_storage_free(sp);
    fcc_unlock(context, fd);
    close(fd);
    return ret;
}

static krb5_error_code KRB5_CALLCONV
fcc_get_principal(krb5_context context,
                      krb5_ccache id,
                      krb5_principal *principal)
{
    krb5_error_code ret;
    int fd;
    krb5_storage *sp;

    ret = init_fcc (context, id, "get-principal", &sp, &fd, NULL);
    if (ret)
          return ret;
    ret = krb5_ret_principal(sp, principal);
    if (ret)
          krb5_clear_error_message(context);
    krb5_storage_free(sp);
    fcc_unlock(context, fd);
    close(fd);
    return ret;
}

static krb5_error_code KRB5_CALLCONV
fcc_end_get (krb5_context context,
               krb5_ccache id,
               krb5_cc_cursor *cursor);

static krb5_error_code KRB5_CALLCONV
fcc_get_first (krb5_context context,
                 krb5_ccache id,
                 krb5_cc_cursor *cursor)
{
    krb5_error_code ret;
    krb5_principal principal;

    if (FCACHE(id) == NULL)
        return krb5_einval(context, 2);

    *cursor = malloc(sizeof(struct fcc_cursor));
    if (*cursor == NULL) {
        krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", ""));
          return ENOMEM;
    }
    memset(*cursor, 0, sizeof(struct fcc_cursor));

    ret = init_fcc(context, id, "get-frist", &FCC_CURSOR(*cursor)->sp,
                       &FCC_CURSOR(*cursor)->fd, NULL);
    if (ret) {
          free(*cursor);
          *cursor = NULL;
          return ret;
    }
    ret = krb5_ret_principal (FCC_CURSOR(*cursor)->sp, &principal);
    if(ret) {
          krb5_clear_error_message(context);
          fcc_end_get(context, id, cursor);
          return ret;
    }
    krb5_free_principal (context, principal);
    fcc_unlock(context, FCC_CURSOR(*cursor)->fd);
    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_get_next (krb5_context context,
                krb5_ccache id,
                krb5_cc_cursor *cursor,
                krb5_creds *creds)
{
    krb5_error_code ret;

    if (FCACHE(id) == NULL)
        return krb5_einval(context, 2);

    if (FCC_CURSOR(*cursor) == NULL)
        return krb5_einval(context, 3);

    if((ret = fcc_lock(context, id, FCC_CURSOR(*cursor)->fd, FALSE)) != 0)
          return ret;
    FCC_CURSOR(*cursor)->cred_start = lseek(FCC_CURSOR(*cursor)->fd,
                                                     0, SEEK_CUR);

    ret = krb5_ret_creds(FCC_CURSOR(*cursor)->sp, creds);
    if (ret)
          krb5_clear_error_message(context);

    FCC_CURSOR(*cursor)->cred_end = lseek(FCC_CURSOR(*cursor)->fd,
                                                   0, SEEK_CUR);

    fcc_unlock(context, FCC_CURSOR(*cursor)->fd);
    return ret;
}

static krb5_error_code KRB5_CALLCONV
fcc_end_get (krb5_context context,
               krb5_ccache id,
               krb5_cc_cursor *cursor)
{

    if (FCACHE(id) == NULL)
        return krb5_einval(context, 2);

    if (FCC_CURSOR(*cursor) == NULL)
        return krb5_einval(context, 3);

    krb5_storage_free(FCC_CURSOR(*cursor)->sp);
    close (FCC_CURSOR(*cursor)->fd);
    free(*cursor);
    *cursor = NULL;
    return 0;
}

static void KRB5_CALLCONV
cred_delete(krb5_context context,
              krb5_ccache id,
              krb5_cc_cursor *cursor,
              krb5_creds *cred)
{
    krb5_error_code ret;
    krb5_storage *sp;
    krb5_data orig_cred_data;
    unsigned char *cred_data_in_file = NULL;
    off_t new_cred_sz;
    struct stat sb1, sb2;
    int fd = -1;
    ssize_t bytes;
    krb5_const_realm srealm = krb5_principal_get_realm(context, cred->server);

    /* This is best-effort code; if we lose track of errors here it's OK */

    heim_assert(FCC_CURSOR(*cursor)->cred_start < FCC_CURSOR(*cursor)->cred_end,
                    "fcache internal error");

    krb5_data_zero(&orig_cred_data);

    sp = krb5_storage_emem();
    if (sp == NULL)
          return;
    krb5_storage_set_eof_code(sp, KRB5_CC_END);
    storage_set_flags(context, sp, FCACHE(id)->version);

    /* Get a copy of what the cred should look like in the file; see below */
    ret = krb5_store_creds(sp, cred);
    if (ret)
          goto out;

    ret = krb5_storage_to_data(sp, &orig_cred_data);
    if (ret)
          goto out;
    krb5_storage_free(sp);

    cred_data_in_file = malloc(orig_cred_data.length);
    if (cred_data_in_file == NULL)
          goto out;

    /*
     * Mark the cred expired; krb5_cc_retrieve_cred() callers should use
     * KRB5_TC_MATCH_TIMES, so this should be good enough...
     */
    cred->times.endtime = 0;

    /* ...except for config creds because we don't check their endtimes */
    if (srealm && strcmp(srealm, "X-CACHECONF:") == 0) {
          ret = krb5_principal_set_realm(context, cred->server, "X-RMED-CONF:");
          if (ret)
              goto out;
    }

    sp = krb5_storage_emem();
    if (sp == NULL)
          goto out;
    krb5_storage_set_eof_code(sp, KRB5_CC_END);
    storage_set_flags(context, sp, FCACHE(id)->version);

    ret = krb5_store_creds(sp, cred);

    /* The new cred must be the same size as the old cred */
    new_cred_sz = krb5_storage_seek(sp, 0, SEEK_END);
    if (new_cred_sz != orig_cred_data.length || new_cred_sz !=
          (FCC_CURSOR(*cursor)->cred_end - FCC_CURSOR(*cursor)->cred_start)) {
          /* XXX This really can't happen.  Assert like above? */
          krb5_set_error_message(context, EINVAL,
                                     N_("Credential deletion failed on ccache "
                                          "FILE:%s: new credential size did not "
                                          "match old credential size", ""),
                                     FILENAME(id));
          goto out;
    }

    ret = fcc_open(context, id, "remove_cred", &fd, O_RDWR, 0);
    if (ret)
          goto out;

    /*
     * Check that we're updating the same file where we got the
     * cred's offset, else we'd be corrupting a new ccache.
     */
    if (fstat(FCC_CURSOR(*cursor)->fd, &sb1) == -1 ||
          fstat(fd, &sb2) == -1)
          goto out;
    if (sb1.st_dev != sb2.st_dev || sb1.st_ino != sb2.st_ino)
          goto out;

    /*
     * Make sure what we overwrite is what we expected.
     *
     * FIXME: We *really* need the ccache v4 tag for ccache ID.  This
     * check that we're only overwriting something that looks exactly
     * like what we want to is probably good enough in practice, but
     * it's not guaranteed to work.
     */
    if (lseek(fd, FCC_CURSOR(*cursor)->cred_start, SEEK_SET) == (off_t)-1)
          goto out;
    bytes = read(fd, cred_data_in_file, orig_cred_data.length);
    if (bytes != orig_cred_data.length)
          goto out;
    if (memcmp(orig_cred_data.data, cred_data_in_file, bytes) != 0)
          goto out;
    if (lseek(fd, FCC_CURSOR(*cursor)->cred_start, SEEK_SET) == (off_t)-1)
          goto out;
    ret = write_storage(context, sp, fd);
out:
    if (fd > -1) {
          fcc_unlock(context, fd);
          if (close(fd) < 0 && ret == 0) {
              krb5_set_error_message(context, errno, N_("close %s", ""),
                                           FILENAME(id));
          }
    }
    krb5_data_free(&orig_cred_data);
    free(cred_data_in_file);
    krb5_storage_free(sp);
    return;
}

static krb5_error_code KRB5_CALLCONV
fcc_remove_cred(krb5_context context,
                    krb5_ccache id,
                    krb5_flags which,
                    krb5_creds *mcred)
{
    krb5_error_code ret, ret2;
    krb5_cc_cursor cursor;
    krb5_creds found_cred;

    if (FCACHE(id) == NULL)
          return krb5_einval(context, 2);

    ret = krb5_cc_start_seq_get(context, id, &cursor);
    if (ret)
          return ret;
    while ((ret = krb5_cc_next_cred(context, id, &cursor, &found_cred)) == 0) {
          if (!krb5_compare_creds(context, which, mcred, &found_cred)) {
            krb5_free_cred_contents(context, &found_cred);
              continue;
        }
          cred_delete(context, id, &cursor, &found_cred);
          krb5_free_cred_contents(context, &found_cred);
    }
    ret2 = krb5_cc_end_seq_get(context, id, &cursor);
    if (ret == 0)
          return ret2;
    if (ret == KRB5_CC_END)
          return 0;
    return ret;
}

static krb5_error_code KRB5_CALLCONV
fcc_set_flags(krb5_context context,
                krb5_ccache id,
                krb5_flags flags)
{
    if (FCACHE(id) == NULL)
        return krb5_einval(context, 2);

    return 0; /* XXX */
}

static int KRB5_CALLCONV
fcc_get_version(krb5_context context,
                    krb5_ccache id)
{
    if (FCACHE(id) == NULL)
        return -1;

    return FCACHE(id)->version;
}

struct fcache_iter {
    int first;
};

static krb5_error_code KRB5_CALLCONV
fcc_get_cache_first(krb5_context context, krb5_cc_cursor *cursor)
{
    struct fcache_iter *iter;

    iter = calloc(1, sizeof(*iter));
    if (iter == NULL) {
          krb5_set_error_message(context, ENOMEM, N_("malloc: out of memory", ""));
          return ENOMEM;
    }
    iter->first = 1;
    *cursor = iter;
    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_get_cache_next(krb5_context context, krb5_cc_cursor cursor, krb5_ccache *id)
{
    struct fcache_iter *iter = cursor;
    krb5_error_code ret;
    const char *fn, *cc_type;
    krb5_ccache cc;

    if (iter == NULL)
        return krb5_einval(context, 2);

    if (!iter->first) {
          krb5_clear_error_message(context);
          return KRB5_CC_END;
    }
    iter->first = 0;

    /*
     * Note: do not allow krb5_cc_default_name() to recurse via
     * krb5_cc_cache_match().
     * Note that context->default_cc_name will be NULL even though
     * KRB5CCNAME is set in the environment if
     * krb5_cc_set_default_name() hasn't
     */
    fn = krb5_cc_default_name(context);
    ret = krb5_cc_resolve(context, fn, &cc);
    if (ret != 0)
        return ret;
    cc_type = krb5_cc_get_type(context, cc);
    if (strcmp(cc_type, "FILE") != 0) {
        krb5_cc_close(context, cc);
        return KRB5_CC_END;
    }

    *id = cc;

    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_end_cache_get(krb5_context context, krb5_cc_cursor cursor)
{
    struct fcache_iter *iter = cursor;

    if (iter == NULL)
        return krb5_einval(context, 2);

    free(iter);
    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_move(krb5_context context, krb5_ccache from, krb5_ccache to)
{
    krb5_error_code ret = 0;

    ret = rk_rename(FILENAME(from), FILENAME(to));

    if (ret && errno != EXDEV) {
          char buf[128];
          ret = errno;
          rk_strerror_r(ret, buf, sizeof(buf));
          krb5_set_error_message(context, ret,
                                     N_("Rename of file from %s "
                                          "to %s failed: %s", ""),
                                     FILENAME(from), FILENAME(to), buf);
          return ret;
    } else if (ret && errno == EXDEV) {
          /* make a copy and delete the orignal */
          krb5_ssize_t sz1, sz2;
          int fd1, fd2;
          char buf[BUFSIZ];

          ret = fcc_open(context, from, "move/from", &fd1, O_RDONLY, 0);
          if(ret)
              return ret;

          unlink(FILENAME(to));

          ret = fcc_open(context, to, "move/to", &fd2,
                           O_WRONLY | O_CREAT | O_EXCL, 0600);
          if(ret)
              goto out1;

          while((sz1 = read(fd1, buf, sizeof(buf))) > 0) {
              sz2 = write(fd2, buf, sz1);
              if (sz1 != sz2) {
                    ret = EIO;
                    krb5_set_error_message(context, ret,
                                               N_("Failed to write data from one file "
                                                    "credential cache to the other", ""));
                    goto out2;
              }
          }
          if (sz1 < 0) {
              ret = EIO;
              krb5_set_error_message(context, ret,
                                           N_("Failed to read data from one file "
                                              "credential cache to the other", ""));
              goto out2;
          }
    out2:
          fcc_unlock(context, fd2);
          close(fd2);

    out1:
          fcc_unlock(context, fd1);
          close(fd1);

          _krb5_erase_file(context, FILENAME(from));

          if (ret) {
              _krb5_erase_file(context, FILENAME(to));
              return ret;
          }
    }

    /* make sure ->version is uptodate */
    {
          krb5_storage *sp;
          int fd;
          if ((ret = init_fcc (context, to, "move", &sp, &fd, NULL)) == 0) {
              if (sp)
                    krb5_storage_free(sp);
              fcc_unlock(context, fd);
              close(fd);
          }
    }

    fcc_close(context, from);

    return ret;
}

static krb5_error_code KRB5_CALLCONV
fcc_get_default_name(krb5_context context, char **str)
{
    return _krb5_expand_default_cc_name(context,
                                                  KRB5_DEFAULT_CCNAME_FILE,
                                                  str);
}

static krb5_error_code KRB5_CALLCONV
fcc_lastchange(krb5_context context, krb5_ccache id, krb5_timestamp *mtime)
{
    krb5_error_code ret;
    struct stat sb;
    int fd;

    ret = fcc_open(context, id, "lastchange", &fd, O_RDONLY, 0);
    if(ret)
          return ret;
    ret = fstat(fd, &sb);
    close(fd);
    if (ret) {
          ret = errno;
          krb5_set_error_message(context, ret, N_("Failed to stat cache file", ""));
          return ret;
    }
    *mtime = sb.st_mtime;
    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_set_kdc_offset(krb5_context context, krb5_ccache id, krb5_deltat kdc_offset)
{
    return 0;
}

static krb5_error_code KRB5_CALLCONV
fcc_get_kdc_offset(krb5_context context, krb5_ccache id, krb5_deltat *kdc_offset)
{
    krb5_error_code ret;
    krb5_storage *sp = NULL;
    int fd;
    ret = init_fcc(context, id, "get-kdc-offset", &sp, &fd, kdc_offset);
    if (sp)
          krb5_storage_free(sp);
    fcc_unlock(context, fd);
    close(fd);

    return ret;
}


/**
 * Variable containing the FILE based credential cache implemention.
 *
 * @ingroup krb5_ccache
 */

KRB5_LIB_VARIABLE const krb5_cc_ops krb5_fcc_ops = {
    KRB5_CC_OPS_VERSION,
    "FILE",
    fcc_get_name,
    fcc_resolve,
    fcc_gen_new,
    fcc_initialize,
    fcc_destroy,
    fcc_close,
    fcc_store_cred,
    NULL, /* fcc_retrieve */
    fcc_get_principal,
    fcc_get_first,
    fcc_get_next,
    fcc_end_get,
    fcc_remove_cred,
    fcc_set_flags,
    fcc_get_version,
    fcc_get_cache_first,
    fcc_get_cache_next,
    fcc_end_cache_get,
    fcc_move,
    fcc_get_default_name,
    NULL,
    fcc_lastchange,
    fcc_set_kdc_offset,
    fcc_get_kdc_offset
};